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Population movement and malaria persistence in Rameswaram Island
Sot. Scl. Med. Vol. 22. No. 8. pp. 879-886. 1986 Printed in Great Bntain
POPULATION PERSISTENCE P. K.
RAJAGOPALAN,
02”-9536 86 53 CMI-F 0.00 Pcrgamon Press Ltd
MOVElMENT AND IN RAMESWARAM
MALARIA ISLAND*
P. JAMBULINGAM, S. SABESAS, K. KRISHSA.LICIORTHY, S. RAJESDRAS. K. GUXASEKARAN and N. PRADEEP KUY~~R Vector Control Research Centre, Pondicherry. India
FOREWORD R. MANSELL PROTHERO Department of Geography, University of Liverpool. Roxby Building. Liverpocl L69 3BX, England In the late 1950s and early 1960s frequent warnings were expressed about the intervention of what may be called ‘human factors’ in anti-malaria programmes in various parts of the world. Reports of the WHO Expert Committee on Malaria continually referred to the prejudicial effects of settlement patterns, types of dwellings, social organization, economic activities and various forms of population mobility on attempts at malaria eradication. These effects continue and in practice little has been done to deal adequately with them. Of the three related elements in human malaria (parasite, vector and human being) the third has received insufficient attention, time and competence in its study. Levels of generalization are accepted concerning the human element which would not be tolerated in respect of parasite and vector. There is every cause to be concerned with relationships between population movements and malaria. They present problems in the contribution of mobile elements to the continuation of transmission and in the devising of anti-malarial programmes in which mobility can be adequately accommodated. Work on these programmes in various African countries between 1960 and 1970 provided clear evidence of insufficient attention being given to the multi-faceted nature of mobility and to other ‘human factors’ (11. There is need for detailed knowledge not only of ‘how many’, ‘where’ and ‘when’ people move, but also of population distribution, patterns of settlements, the nature of dwellings, administrative and social organization and the range of economic activities. These may be investigated at a variety of scales. They may be illustrated at macro-scale with reference to North-Eastern Africa [I]. Major north-south movements of population and stock in the wet season brought people into contact with malaria vectors breeding in the water sources required for human and animal survival. There were further movements of people associated with the day-to-day availability of resources, social tradition and family organization. All these movements made it difficult to maintain contact with people in order to spray dwellings (which were also mobile) with residual insecticide and to distribute anti-malaria drugs. This complexity of mobility is quite logical in relation to environmental constraints and social organization, but seemingly chaotic for the design and function of anti-malarial measures. Traditional pastoralism, politics and contemporary refugee movements have combined to prejudice measures for the improvement of public health. An example at micro-scale is provided by the Garki Project in Northern Nigeria where over the period 1970-1975 the epidemiology and control of malaria in the Sudan savanna was studied experimentally [3]. The Project concentrated particularly on the measurement of entomological, parasitological and seroimmunological variables and on their relationships; some meteorological, demographic and climatic variables and the prevalence of abnormal haemoglobins in the population were also studied. The study population was relatively mobile, mobility patterns showing marked variations seasonally and from one year to another, with some differences from one village to another. The overall conclusion was that “It is very unlikely that mobility in the human population, which was relatively pronounced, was the main cause of the maintenance of transmission”. However, while the Garki study probably provides some of the most detailed evidence of relationships between mobility and malaria the data are not complete and certainly not all types of mobility occurring in the project area were identified. In a paper on “The role of migrant studies in epidemiological research” Wessen drew attention to the need to understand the migration process in relation to environmental (physical, socio-economic and political) and genetic factors which characterize migrants and also the need to consider these factors in non-migrants [4]. While stating that “most movements of people are temporary rather than permanent” Wessen’s main concern was with “a migration a change of residence and community that is intended to be if not permanent, at least of substantial duration”. In epidemiology it is vital to differentiate specificall~vamong those who move, to counter the tendency to regard movements, whatever and wherever they may be, as having uniform ‘This paper, without the Foreword, has been published in the Bulletin, India Council of Medical Research, to which due acknowledgement is made. 879
P. K. RAJACYJP*LAN er ai.
St30
character and impact [j]. Within the last few years the medical authorities in Brazil, with its vast movements of people into Xmazonia and into the major cities, identify mobility as the single most important non-medical factor in the great range of medical problems which confront them [6]. In 1983. the Socio-Economic Working Group in the World Bank UNDP/WHO Special Programme for Research and Training in Tropical Diseases supported a workshop on “Human population movements and their impact on tropical disease transmission and control”, held at the Faculty of Medicine at the University of Peradeniya, Sri Lanka [7]. However, in many other instances a great deal of lip-service has been paid to mobility and other human factors by those
involved in planning anti-malaria and other public health activities but too little of a practical nature and in sufficient detail has been done about these factors in the field. Harinasuta et al. reviewing recent advances in malaria with special reference to Southeast Asia state “ a continuing need to study the epidemiological social and economic aspects in endemic areas” and specify factors of human ecology and ethnology, including population movements, among these [S]. They note the epidemiological importance of movements to and from malarious countries, the varying extent of movement within countries which is largely uncontrolled, and the influx of population across international boundaries during political disturbances (e. g. the influx of about half a million Kampuchean refugees to Thailand, many infected with P. fulciparum that did not respond to a combination of
sulphadoxine-pyramethamine). Recommendations on epidemiology and control include encouraging research on the socio-economic aspects of malaria and its control, with particular reference to population movements, human behaviour and attitudes and agricultural practise in relation to the transmission season. But little is being done in practice to carry out such recommendations. Only one of the research projects on malaria reported to the South-East Asia Advisory Committee on Medical Research, Seventh Session, New Delhi, India, April 1981, was of a specifically ‘social’ character; it was undertaken in Thailand and concerned “Knowledge, perception and behaviour of malaria prevention” [9]. The report of a “Seminar on anti-malaria operations with special reference to applied field research in malaria in the WHO South-East Asia Region”, held in 1979, made limited and for the most part only passing reference to ‘human factors’ [IO].
Kalra in a review of the National Malaria Eradication Programme in India made many references to the roles played by human factors-both long-standing (e.g. the movements of ‘tribal’ people and the mud plastering of sprayed surfaces) and recent (e.g. ‘man-made malaria’ consequent on irrigation developments, hydro-electric projects and flood control) [ 1I]. In the need for applied research he specified nothing on these factors in the short-term, though for long-term studies recommended that the vector ecologicalepidemiological field stations being set up should concern themselves with human and socio-economic factors in the epidemiology on malaria. Pattanayak and Roy, discussing the modified plan of operations for malaria control in India, make no reference to these factors in their brief specification of needs for basic and applied research [l2]. In Southeast Asia and in parts of India there are problems arising from P. fufciporum resistance to 4-aminoquinolines and evidence has been given of the part played by population movements in the diffusion of this resistance [13]. Only limited resources have been directed to investigating the specific function of population movements in the diffusion of resistance and work might be undertaken to simulate this diffusion and thus possibly assist in containing resistance. The question may be fairly asked as to whether too much is being taken for granted? The neglect of human factors in general and of population mobility in particular is unwarranted, for there is much evidence to show that this element has been dealt with inadequately and with limited competence. Should not human factors be given at least as much attention as that which is given to parasites and vectors? They certainly present very special problems, given the unpredictability of human beings, for which they (human beings) may be partly responsible, but which may also result from environmental influences (such as natural hazards) over which they have limited control. The paper on Rameswaram Island is a significant, but rare, example of a detailed field investigation of relationships between population movements and malaria, undertaken with interdisciplinary and longitudinal perspectives (see also [14]). Abstract-The role of population movement on the persistent transmission of malaria in Rameswaram Island was studied. Majority of the inhabitants of the island are fishermen, who engage in perennial fishing. They move from one coastal place to the other for fishing and stay in temporary camps depending on season and fish availability. Such seasonal fishing camps attract fishermen from the mainland coastal villages also. The parasitological and entomological studies carried out in these places reveal that some of the camps are highly vulnerable to the movement of individuals with malaria infection and highly receptive. Rameswaram being a holy place, receives pilgrims from all over India and Nepal. Phsmodium falciparum cases recorded from the pilgrims of North India indicate the danger of the possible introduction of chloroquine-resistant parasite in the island. Also, a large number of passengers in transit from various countries, many of which are at risk of malaria transmission, stay in the island before or after visiting Sri Lanka. Such population movements being a continuous and regular feature are significant and result in failures in the operational programmes. INTRODUCTION
Population movement is one of the important factors having impact on malaria prevalence. It has been the
major reason for many outbreaks, spreading of drug resistant strains of parasites, failure of control operations etc. in different parts of the world. Though the
Population movement and malaria Persistence in Rameswaram Island importance of population movement in malaria epidemiology has been recognized, due consideration has not been given to this aspect of the disease in planning and implementation of control programmes. It is only recently that the need for research on this aspect is emphasized and a few studies have been initiated in some countries, where population movements pose a major problem for disease control. A study was carried out by the Vector Control Research Centre, Pondicherry on the role of population movement in persistence of malaria transmission in Rameswaram Island, Tamil Nadu and the results are presented. Rameswaram island (09’16’N, 79’18’E) with an area of 55 km’ and a population of about 56,000 (198 1 census) is not only an important pilgrim centre for the Hindus, attracting visitors from all over India, but is also a fishermen’s paradise as the physiographic features favour year round fishing. Therefore, the majority of the local inhabitants are either fishermen or are engaged in the fishing industry. Strategically located between India and Sri Lanka, the island is connected with Mandapam in the mainland by a 3 km-long rail bridge (there is no road connection) across Palk strait. There is a regular ferry service between Rameswaram and Sri Lanka (23 km distance) every alternate day which enables, movement of people between India and Sri Lanka through the island. Extensive studies carried out by the Vector Control Research Centre on malaria and its vector in the island showed that there is perennial transmission of malaria and a large number of positive cases (both Plasmodium cicax and P. falciparum) transmitted by Anopheles culicifncies was recorded year after year since 1974 [15-171. Fishermen regularly move from one place to another within the island, between the coastal mainland villages and the island and this population movement coupled with the socioeconomic aspects of fishing and the peculiar topography of the island contributes in a large measure to perpetuate malaria transmission in the island and in the coastal villages of the mainland. These factors were studied during 1982-1984 and described below. MATERIAL AND iMETHODS
Fishermen movement was monitored by questioning them in various camps and also by the VCRC staff accompanying them whenever possible. A card was made for each migrating family, where all data was recorded. Entomological collection, fever surveys and mass blood surveys for malaria were made following standard procedures and the data recorded and analysed. Additional information on movement of tourists including pilgrims and transit passengers to Sri Lanka and India was kindly provided by the Department of Tourism, Port Office and Choultries. Data on malaria incidence were provided by the State NMEP. SPECIAL FEATURES OF THE ISLAND
The island Dhanushkodi. 45 km away Adam’s bridge,
lies west to east from Pamban to Talaimannar in Sri Lanka is about from Dhanushkodi, connected by which is a chain of shoals separating
881
Palk Bay in the north and Gulf of Mannar in the south. Some of the sand banks along Adam’s bridge are dry and nowhere are the shoals deeper than 1 m. No boat sails across Adam’s bridge. Pamban. on the western side of the island, is connected to the mainland by a rail bridge constructed over a century ago, and to enable ferry boats to pass under, one span in the middle is lifted mechanically. This facility is not. however, used frequently. However, all kinds of boats can easily pass below this span of the rail bridge. The sea around the entire island is relatively shallow- and the depth is not more than 30m for considerable distance around the island and as a result the sea is calm without much wave action. Therefore. fishing takes place around the island throughout the year. South-west monsoon (June-August) is weak while the north-east monsoon (September-December) is strong. The fishing activities are more intense on the south bay of the island which is relatively calm from December to June and as a result several fishermen camps are established in the southern shores. Apart from fishermen moving from northern part of the island to southern part, there is a regular movement of fishermen from the coastal areas of the mainland, the districts of Thanjavur, Pudukkottai, Ramnad, Tirunelveli and Kanya-kumari in Tamil Nadu to the camps in the island. The sea along the mainland coast between point Calimere in Thanjavur district and Mandapam in Ramnad district is also relatively calm because of the peculiar topography, but becomes rough during and in the months following the northeast monsoon. This is one of the reasons why a large scale movement of fishermen takes place from the mainland villages to the island. Over 30 varieties of fish, prawns and crab are available around Rameswaram Island throughout the year. The daily catch of fish, prawns etc. amounts to Rs. 5.00,OOO (us%50,000). Rameswaram, being one of the holy places for Hindus, attracts pilgrims from all over India and Nepal throughout the year, their number varying between 1000-4000 per day. Many of them come from some states of India where resistant strain of P. falciparum has been reported. They usually stay for a day or two in the island. Several adventurous groups from mainland have also, in recent years, migrated to certain areas of the island to eke out a living. While some of them have taken to fishing, most others are engaged in odd job-not excluding stealing of firewood from casuarina plantations (belonging to the Government of Tamil Nadu) and selling them for profit, smuggling and illicit distillation of liquor. There are several settlements like this which have come up in the island during the last decade, the most recent one being Muthuramalingapuram, which is highly malarious, with about 100 families. The induction of a relatively large susceptible population in these new settlements is a factor for high malaria prevalence in the island, particularly in view of the fact that these settlements are located near inaccessible casuarina plantations with high vector breeding sources. Since the island is strategically located between India and Sri Lanka, there is a large floating population. Tourists and businessmen from India and many foreign countries pass through the island.
P. K.
SUL F
OF
RUAGOPALAN et al
MANNAR
SCALE
. ,BPIDGE .
Fig. 1. Coastal villages and seasonal fishermen camps in Rameswaram Island PATTERN
OF 1lOVEMEST
OF FISHERMEN
The coastal areas were surveyed and the places where fishermen camps are established year after year were marked and the pattern of movement studied. The seasonal and perennial fishing centres in Rameswaram island are shown in Fig. 1. The seasonal centres are temporary camps on the seashore with thatched huts built by fishermen from other coastal villages during the season and removed later. Duration of each camp depends on fish availability in a particular season. While the duration of some of the camps (Kundukal, Thuraimugam and Dhanushkodi) on the southern shore line extends from 5 to 7 months. the duration of most of the other camps varies between 2-3 months. However, almost all the seasonal camps on the northern sea-shore lasts as long as 7 months. Some fishermen form companies owning diesel-operated launches and stay at the camps near Pamban and Rameswaram (the two places in the island where facilities for harbouring and fuelling launches are available). Fishermen employed in the companies belong to different villages in the island and mainland and are rarely accompanied by their families. These fishermen go to the southern side of the island for fishing in seasons and return the same day. Only those fishermen who are employed in companies owning certain special nets and who own country boats stay with their entire family in the temporary settlements for the entire fishing season which lasts for several months. The pattern of fishermen movement from the mainland coastal villages to Rameswaram Island and vice versa is shown in Fig. 2. The different areas from where people migrate and the season are indicated. Once the fishing season in a particular camp is over, the fishermen either move to another camp or return to their villages, which may be either in the island itself or in the mainland. The number of people from different villages/ districts joining the various camps in the island are shown in Table 1. The bigger camps are in Kundukal, Thuraimugam, Moonramchattram, Dhanushkodi and Vallathadi. In addition, there are several smaller camps with less than 100 fishermen in each. A study
of the population composition in these camps during 1983-1984 showed that out of 6355 people, 2964 were adult males, 1537 were adult females and I854 were children including 205 infants indicating the movement of entire families. SlASS
BLOOD AND FEVER
SURVEYS
The VCRC teams visited the camps within 1 week of their being set up and carried out mass blood surveys to find out whether any cases have been imported. From 11 such camps in rhe island, 4073 blood smears were examined and 138 were found positive for malaria (P. cicax 43; P. falciparum 92; mixed 3) (Table 2). Among the positives, IO7 had no apparent clinical symptoms. About 80% of P. fulciparum cases were recorded from the asymptomatic carriers. Malaria positives were found in all age groups including infants (under 1 year) and children aged 14 years. There were 109 gametocyte carriers confirming the existence of a reservoir to enable subsequent local transmission. Positive cases in the camp included fishermen from mainland villages as well as the coastal villages of the island. Fever survey was carried out regularly, three times a week, in the camp for the entire duration to determine whether local transmission takes place and the data recorded in cards issued to each family. A total of 680 fever cases were examined and 107 were found positive for malaria (P. uivax 75;P.fufciparum 31; mixed 1) (Table 3). Among the positives, those who were examined within 10 days of their arrival at a camp were considered as imported. There are six such imported cases. Based on their malaria history the remaining 101 positives were considered to be new infections (excluding the possibility of recrudescence or relapse). The positive slides were from all age groups including infants and children of 1-4 years of age, confirming local transmission in the camps. RECEPTIVITY
STATUS
The receptivity of the island has always been high as shown by earlier studies [15-l 71. Regular mosquito
Population
movement
and malaria
persistence
in Rameswaram
THANJAVUR
j-k-J
R
RAMNAD
/
TIRUNELVELI
S MANGALA+
883
Island
Dt.
:..
Dt.
Dt.
MUTl4WIPURAM_,.’ ERAL
-4
,._ . . . . -‘:;;.
3
_ RAJAYARGAd
Fig. 2.
1
Ai;AT+flSWARAU
Seasonal migration
pattern
of fishermen
‘I
PftlYARY
HEALTH
.
COASTAL
VILLAGES
in the coastal Island.
I. Pouulation
mizratine
in different
No. of families ScE.Oll
Name of camp
in months
Kundukal Tburaimugam Othathalai Thavakadu Paraiyadi Otha Patti Moonramchatram Dhanushkodi Vallathadi Total
Nov.-Mar. Nov.-Mar. Jan.-Mar. Jan.-Mar. Dec.-Feb. Jan.-Mar. Jan.-Mar. Feb.-Ott. Feb.-July
-Kanyakumari district 0 0 0 0 0 0 103 (648) 0 0 103 (648)
I
of mainland
and Rameswaram
a frequent movement of fishermen between Kundukal camp and Kundukal village. The camp being in such close proximity with Kundukal village with abundant breeding sources is highly receptive for malaria transmission. One sporozoite positive A. culicifacies was found in the camp in March, confirming local transmission. The largest number of positive cases recorded during fever surveys were also from this camp. A. culicifacies was also recorded from Vallathadi camp in the northern shore. This camp is in close proximity to the Nalupanai village where the fishermen from the camp stay during night.
collections carried out in Kundukal camp showed the presence of Anopheles culicifacies in both resting and biting collections. This camp is adjacent to the Kundukal village where A. cuficzjkies was recorded every month from June 1983 to May 1984, with density ranging from 0.17 to 2.83 pmh in different months. The mean hut density ranged from 1.0 to 13.75 during the same period. Breeding sources are abundant in this village. The duration of the Kundukal camp coincides with the season of high vector prevalence (post-monsoon season) and with the peak season in malaria incidence in the island. There is also
Table
villages
CENTRES
(persons)
Tirunelveli district
1(4) 1 (4) 0 0 0
l(4) 3(l6) I (3) 5 (23) I2 (54)
seasons migrated
in different
camos
from the villages
Ramanathapuram district 86 (523) 76 (445) 1(3) 5 (69) 2 (32) 8 (47) IO (55) 25(147) 84 (465) 297 (I 786)
in
Within Rameswaram
Island
347 (1979) 69 (395) IO (80) 30(182) I7 (106) 39 (227) 37 (209) 1I7 (595) 20 (94) 686 (3867)
Total 434 (2506) 146 (844) I I (83) 35 (251) 19(138) 48 (278) I53 (928) 143 (745) I09 (382) 1098 (6355)
P. K.
884
et al.
RAJAGOPALAN
Table 2. Mass blood surveys carried out in the seasonal fishermen camps No. of persons examined
Number positive
Kundukal Thuraimugam Thavakadu South Thavakadu North Paraiyadi Othapatti Moonramchatram South h4oonramchatram North Dhanushkodi South Dhanushkodi North Karaiyur Company Total
I702 469 IM) I77 40 139 I35 90 323 272 626 4073
61 7 4 5 5 IO 2 2 IO I4 IS 138
2 I3
Mainland Mandapam Ervadi (Thonithurai thoppu) Rochmanager village Total
252 61 691 loo4
ia I 24 43
0 I 2
Name of camp
Number with fever P. ciwx
P. falciponrm
Number wnhout symptoms Mixed
P. vitzx
P. falciparum
MIXed
Island
6 I I 0 0 0 0 1 I
I
I
IO 0 0 I 0 2 0 0 0 I 3 17
I
I4
0 0 0 0 0 0 0 0 0 0
I
0 3 0 3 3 0 0 I 4 2 30
II 75
0 0 0 0 0 1
3 0 4 7
0 0 I I
4 I 4 9
IO 0 I3 23
0 0 I I
30 6 0 J I 4 2 I 8
a
0 0 0 0
I I
Sporozoite positive specimens were obtained during blood smears examined, 43 were positive, 10 from the camping period of fishermen in the Nalupanai fever cases and 33 from asymptomatic cases. Sevvillage. The receptivity of the other camps vary. enteen of these were gametocyte carriers. These studThough it was not possible to obtain more accurate ies show that there is a back and forth movement of data, there is the possibility of local transmission in fishermen periodically between mainland villages and some of the other camps. Rameswaram and that they can either be donors or Because these fishermen camps are of a transient recipients for malaria in these places. nature, there is no permanent provision to carry out It may be mentioned here that in terms of species surveillance and treatment under the existing NMEP composition, seasonal prevalence and type of breedset up to cover the population. As a result, most cases ing places of the vector population, season of malaria do not receive radical treatment and therefore when transmission, climatic conditions and vegetation patthe camps are wound up and the fishermen return to tern, the coastal villages in the districts of Pudukottai, their villages, they carry with them the infection, Ramanathapuram and Tirunelveli are similar to thereby creating foci for further transmission in such Rameswaram island. However, the coastal areas of areas where the receptivity is high. An earlier study Ramanathapuram District and Rameswaram Island had shown the presence of gametocyte carriers in are most receptive for malaria transmission because large numbers in some areas of the island and some of the abundance of coconut garden pits and casuof this population also moves to the camps in main- arina plantation pits, where the vector species, A. land [18]. Data collected from Primary Health Cen- culicifacies, breed and where malaria transmission is tres and District Health Units in the mainland (Table also perennial. The degree of receptivity in this area, 4) show that in several PHCs, both indigenous and based on the distribution and numbers of coconut imported cases were recorded by NMEP. These and casuarina gardens with viable pits heavily breedPHCs cover all coastal villages from where fishermen ing A. culicifacies is shown in Fig. 3. This is reflected visit the camps in Rameswaram Island. Thus, there is in the number of malaria cases recorded by different clear evidence of importation of malaria cases from PHCs in the mainland (Table 4), the largest number the island to the mainland. The movement of game- of malaria cases having been recorded in Uchipuli tocyte carriers from the mainland villages to camps in PHC (which includes Rameswaram Island also). The the island also takes place as shown by the results of receptivity decreases as one goes either northwards or mass blood surveys in camps. Mass blood surveys southwards along the mainland coast from Mandacarried out in mainland camps of Mandapam, Ervadi pam. There are also some coastal towns like Kayand Rochmanagar (Table 2) showed that out of 1004 Table 3. Fever survey in fishermen camps in Rameswaram Island Name of camps Kundukal Thuraimugam Othathalai Thavakadu South Paraiyadi Othapatti Moonramchatram South. Dhanushkodi South Vallathadi Karaiyur Companies Total
Number examined
Number positive
335 69 8 9 IO 31 46 106 56 IO 680
77 6 0 I 0 6 ‘2 I4 I 0 107
P. viuax
58 4 0 I 0 0 2 9 I 0 75
P. falciporum
18 2 0 0 0 6 0 5 0 0 31
Mixed
I 0 0 0 0 0 0 0 0 0
I
Population movement and malaria persistence in Rameswaram
Island
885
Table 4. Number of malaria cases recorded in different Primary Health Centres and District Heaith Units of Tamil Nadu, covering the coastal area (1982) data, from State NMEP). Number of malaria cases in Coastal villages PHC;Health Unit
District Pudukottai Ramanathapuram
Tirunelveli Kanyakumari
Ponbethi Kannangudi Pandukudi R. S. Mangalam Devipattinam Uchipulli (1981) (including Rameswaram) T. U. Mangai Kadaladi (198 I) Palayamkottai Sankarankoil Kanyakumari
Indigenous 0 0 IS8 45 319 6475
Interior villages
Imported
Indigenous
Imported
0 0 54 55 I62 0
0 0 0 0 259
2 22 39 23 0 0
24 127 I52’ I62 99
201 0 0 0 0
39 157 235 0 0
48 22 40’ 0 0
7
*Positives recorded only from two coastal towns. Tuticorin and Kayalpattinam
alpattinam and Tuticorin in Tirunelveli District and Thondi in Ramanathapuram District where urban malaria transmitted by Anophefes stephensi breeding in wells and overhead tanks, has been recorded year after year. STUDIES ON PILGRIMS AND TOURISTS
There is also evidence of possible introduction of resistant strains of P. fuiciparum into the island by pilgrims coming from north eastern states of India. In a random study conducted on 640 pilgrims from several states whose blood smears were examined, 11 were found positive for P. falciparum (one from Maharashtra, one from Uttar Pradesh and 9 from
(1981).
Bihar). Ten of them were asymptomatic gametocyte carriers. Chloroquine resistant strains of P. fulciparum has been recorded in all these three states. In Rameswaram, P. fufciparum is known to be still sensitive to chloroquine [19]. Since the piigrims normally stay at least for a day it will not be long before chloroquine resistant strain of P. falciparum becomes established in this island and thus pose more problems for the control of malaria in the island, because of high receptivity in the island. It was ascertained from the Port authorities and the Tourism Department that from January to October 1983, a total of 56,403 people from 52 countries (including South Americas, United States, Europe, Africa and South-East Asian countries) visited Ram-
POINT
RAMNAD
01.
PAMBAN
BRIDGE
1
PAMBAN
b
Gulf
TIRUNELVELI
of
CALWERE
Mannor
Dt
Fig. 3. Receptivity status for malaria (risk of transmission) in Rameswaram Island and coastal mainland (intensity indicated by shading).
P. K. RAJAGOPALASer al.
886
eswaram either for tourism or in transit on their way to Sri Lanka or back. The vast majority of them (51,227) were from Sri Lanka. There were visitors (excluding those from Sri Lanka) from 19 countries of the World where the risk of malaria transmission exists and from five countries (Brazil, Thailand, Indonesia, Burma and Phillippines) where chloroquine resistant P. falciparum is known [20]. About 100,000 Indian settlers, Tamils and Sri Lankans travel by ferry between Sri Lanka and Rameswaram every year. Apart from this, thousands of repatriates from Sri Lanka are coming to India through Rameswaram port every year following the SrimavoaSastri agreement in 1964. A total of 439,521 repatriates have passed through Rameswaram till May 1984. Though sporadic cases of malaria have been recorded among travellers, no systematic study has been done and therefore no data are available on the possibility of malaria being imported into the island by foreigners. But the danger exists. Population movement, particularly fishermen migration, contribute to a large measure to the persistence and high prevalence of malaria not only in Rameswaram Island but also in the coastal areas of mainland. There are several localities where people from malarious areas move to but there are no vector breeding source. In such pockets, malaria could be eliminated by prompt administration of drugs. In other areas, like Kundukal in Rameswaram Island, which are vulnerable to the movement of people from either malarious or non-malarious areas and which are highly receptive because of vector prevalence and favourable season, chemotherapeutic measures should be combined with vector control measures. Under the existing NMEP operational set up, there is not much flexibility in approach and decision makine at the local level due to several constraints includmg lack of adequate facilities to meet the special needs of the situation. While the influence of human ecology has always been recognized in malaria epidemiology, this factor has not received due attention in malaria conrol in this area.
REFERENCES
Prothero R. M. Population movements and problems of malaria eradication in Africa. Bull. W/d Hlth Org. 24, 405125, 1961. Prothero R. M. Geographical factors and malaria eradication: the case of Morocco. Pacific Viewpoint 5, 182-204, 1964. Prothero R. M. Migrants and Malaria. Longman, London, 1965. Prothero R. M. Public Health, Pasforalism and Politics in the Horn of Ajrica. Melville Herskovits Memorial Lecture, North-Western University Press, Evanston, 1968. Prothero R. M. Problems of public health among pastoralists in Africa: a case study. In Medical
Geography: Techniques und Field Siadies (Edited by McGlashan N. D.). Mrthuen. London. 1977. L. and Gramiccia Cr. The Garki Projecr: 3. Molineaux Research on the Epidemiology and Conrrol of.Ma/aria in Sudan Surunna of W’esl .-ffrica. WHO. Geneva, 19SO. 4. Wessen A. F. The role of migrant studies in epidemiological research. Israel J. med. Sci. 7, Ij8+1591. 1971. 5 Gould W. T. S. and Prothero R. M. Space and time in African population mobility. In People on rhe Move (Edited by i(osinski L. A. and Prothero R. M.). Methuen. London. 1975. Prothero R. XI. Disease and mobility: a neglected factor in epidemiology. Inf. J. Epid. 6, X9-267, 1977. 6. Minsterio da Saude. Doencas e migracao humana. Centro de Documentacao do Ministerio da Sauda. Brasilia, 1982. M. A. (Ed.) Human Popularion Moremew 7. Fernando and Their Impact on Tropical Disease Transmission and Conrrol. Faculty of Medicine, University of Peradenyia. Sri Lanka. T. ef al. Recent advances in malaria with 8. Harinasuta. special reference to South-east Asia. .SEtir Asian J. rrop. Med. publ. Hith 13, 1982. Research. South-East 9. WHO S.E.A. Region. Malaria Asia Advisory Committee on Medical Research. WHO South-East Asia Region. SEA/ACMR 7,.2/a. 1981. 10. WHO S.E.A. Region. Seminnr on Anri-Malaria Operations with Special Reference to Apphed Field Research in Malaria. WHO South-East Asia Region. SEA/MAL:‘IZS. 1980. programme Il. Kalra N. L. National malaria eradication India: its problems, management and research needs. J. Communicable Dis. 10, l-20, 1978. 12. Pattanayak S. and Roy R. G. Malaria in India and the modified plan of operations for its control. J. Communicabk Dis. 12, l-14, 1980. 13 Beales P. F. The effects of migration on the evolution of drug resistant forms of malaria. Paper presented at Conference on Consequences of Migration in Asia and the Pacific. East-West Population Institute, Hawaii, 198 1. Ray A. P. Some aspects of P. falcipnrum resistance programme. Indian J. med. Res. 70, Suppl., 1-13, 1979. 14. Bradley D. J. The epidemiology of fishermen as migrants. E. Afr. med. J. 45, 254-262. 1968. R. K. ef al. Epidemiological aspects of 15. Chandrahas malaria in Rameswaram Island (Tarnil Nadu). Indian J. med. Res. 80, 37, 1984. 16. Sabesan S. er al. Natural infection and vectorial capacity of Anopheles culicifacies Giles in Rameswaram Island. Indian J. med. Res. 80, 43, 1984. P. et al. Density and biting behaviour of 17. Jambulingam Anopheles culicifocies Giles in Rameswaram Island (Tamil Nadu). Indian J. med. Res. 80, 47, 1984. 18. Krishnamoorthy K. er al. Mass blood survey in three villages of Rameswaram Island endemic for malaria. Indian J. med. Res. 80, 1984. 19. Roy R. G. et al. Response of P. falciparum infection to chlorocmine therapy in some parts of Tamil Nadu and Karnamka states.-indian J. med. Res. 63, 1964, 1975. L. J. Essential Malariology, p. 334. 20. Bruce-Chwatt Heinemann Medical Books, London, 1980.
POPULATION PERSISTENCE P. K.
RAJAGOPALAN,
02”-9536 86 53 CMI-F 0.00 Pcrgamon Press Ltd
MOVElMENT AND IN RAMESWARAM
MALARIA ISLAND*
P. JAMBULINGAM, S. SABESAS, K. KRISHSA.LICIORTHY, S. RAJESDRAS. K. GUXASEKARAN and N. PRADEEP KUY~~R Vector Control Research Centre, Pondicherry. India
FOREWORD R. MANSELL PROTHERO Department of Geography, University of Liverpool. Roxby Building. Liverpocl L69 3BX, England In the late 1950s and early 1960s frequent warnings were expressed about the intervention of what may be called ‘human factors’ in anti-malaria programmes in various parts of the world. Reports of the WHO Expert Committee on Malaria continually referred to the prejudicial effects of settlement patterns, types of dwellings, social organization, economic activities and various forms of population mobility on attempts at malaria eradication. These effects continue and in practice little has been done to deal adequately with them. Of the three related elements in human malaria (parasite, vector and human being) the third has received insufficient attention, time and competence in its study. Levels of generalization are accepted concerning the human element which would not be tolerated in respect of parasite and vector. There is every cause to be concerned with relationships between population movements and malaria. They present problems in the contribution of mobile elements to the continuation of transmission and in the devising of anti-malarial programmes in which mobility can be adequately accommodated. Work on these programmes in various African countries between 1960 and 1970 provided clear evidence of insufficient attention being given to the multi-faceted nature of mobility and to other ‘human factors’ (11. There is need for detailed knowledge not only of ‘how many’, ‘where’ and ‘when’ people move, but also of population distribution, patterns of settlements, the nature of dwellings, administrative and social organization and the range of economic activities. These may be investigated at a variety of scales. They may be illustrated at macro-scale with reference to North-Eastern Africa [I]. Major north-south movements of population and stock in the wet season brought people into contact with malaria vectors breeding in the water sources required for human and animal survival. There were further movements of people associated with the day-to-day availability of resources, social tradition and family organization. All these movements made it difficult to maintain contact with people in order to spray dwellings (which were also mobile) with residual insecticide and to distribute anti-malaria drugs. This complexity of mobility is quite logical in relation to environmental constraints and social organization, but seemingly chaotic for the design and function of anti-malarial measures. Traditional pastoralism, politics and contemporary refugee movements have combined to prejudice measures for the improvement of public health. An example at micro-scale is provided by the Garki Project in Northern Nigeria where over the period 1970-1975 the epidemiology and control of malaria in the Sudan savanna was studied experimentally [3]. The Project concentrated particularly on the measurement of entomological, parasitological and seroimmunological variables and on their relationships; some meteorological, demographic and climatic variables and the prevalence of abnormal haemoglobins in the population were also studied. The study population was relatively mobile, mobility patterns showing marked variations seasonally and from one year to another, with some differences from one village to another. The overall conclusion was that “It is very unlikely that mobility in the human population, which was relatively pronounced, was the main cause of the maintenance of transmission”. However, while the Garki study probably provides some of the most detailed evidence of relationships between mobility and malaria the data are not complete and certainly not all types of mobility occurring in the project area were identified. In a paper on “The role of migrant studies in epidemiological research” Wessen drew attention to the need to understand the migration process in relation to environmental (physical, socio-economic and political) and genetic factors which characterize migrants and also the need to consider these factors in non-migrants [4]. While stating that “most movements of people are temporary rather than permanent” Wessen’s main concern was with “a migration a change of residence and community that is intended to be if not permanent, at least of substantial duration”. In epidemiology it is vital to differentiate specificall~vamong those who move, to counter the tendency to regard movements, whatever and wherever they may be, as having uniform ‘This paper, without the Foreword, has been published in the Bulletin, India Council of Medical Research, to which due acknowledgement is made. 879
P. K. RAJACYJP*LAN er ai.
St30
character and impact [j]. Within the last few years the medical authorities in Brazil, with its vast movements of people into Xmazonia and into the major cities, identify mobility as the single most important non-medical factor in the great range of medical problems which confront them [6]. In 1983. the Socio-Economic Working Group in the World Bank UNDP/WHO Special Programme for Research and Training in Tropical Diseases supported a workshop on “Human population movements and their impact on tropical disease transmission and control”, held at the Faculty of Medicine at the University of Peradeniya, Sri Lanka [7]. However, in many other instances a great deal of lip-service has been paid to mobility and other human factors by those
involved in planning anti-malaria and other public health activities but too little of a practical nature and in sufficient detail has been done about these factors in the field. Harinasuta et al. reviewing recent advances in malaria with special reference to Southeast Asia state “ a continuing need to study the epidemiological social and economic aspects in endemic areas” and specify factors of human ecology and ethnology, including population movements, among these [S]. They note the epidemiological importance of movements to and from malarious countries, the varying extent of movement within countries which is largely uncontrolled, and the influx of population across international boundaries during political disturbances (e. g. the influx of about half a million Kampuchean refugees to Thailand, many infected with P. fulciparum that did not respond to a combination of
sulphadoxine-pyramethamine). Recommendations on epidemiology and control include encouraging research on the socio-economic aspects of malaria and its control, with particular reference to population movements, human behaviour and attitudes and agricultural practise in relation to the transmission season. But little is being done in practice to carry out such recommendations. Only one of the research projects on malaria reported to the South-East Asia Advisory Committee on Medical Research, Seventh Session, New Delhi, India, April 1981, was of a specifically ‘social’ character; it was undertaken in Thailand and concerned “Knowledge, perception and behaviour of malaria prevention” [9]. The report of a “Seminar on anti-malaria operations with special reference to applied field research in malaria in the WHO South-East Asia Region”, held in 1979, made limited and for the most part only passing reference to ‘human factors’ [IO].
Kalra in a review of the National Malaria Eradication Programme in India made many references to the roles played by human factors-both long-standing (e.g. the movements of ‘tribal’ people and the mud plastering of sprayed surfaces) and recent (e.g. ‘man-made malaria’ consequent on irrigation developments, hydro-electric projects and flood control) [ 1I]. In the need for applied research he specified nothing on these factors in the short-term, though for long-term studies recommended that the vector ecologicalepidemiological field stations being set up should concern themselves with human and socio-economic factors in the epidemiology on malaria. Pattanayak and Roy, discussing the modified plan of operations for malaria control in India, make no reference to these factors in their brief specification of needs for basic and applied research [l2]. In Southeast Asia and in parts of India there are problems arising from P. fufciporum resistance to 4-aminoquinolines and evidence has been given of the part played by population movements in the diffusion of this resistance [13]. Only limited resources have been directed to investigating the specific function of population movements in the diffusion of resistance and work might be undertaken to simulate this diffusion and thus possibly assist in containing resistance. The question may be fairly asked as to whether too much is being taken for granted? The neglect of human factors in general and of population mobility in particular is unwarranted, for there is much evidence to show that this element has been dealt with inadequately and with limited competence. Should not human factors be given at least as much attention as that which is given to parasites and vectors? They certainly present very special problems, given the unpredictability of human beings, for which they (human beings) may be partly responsible, but which may also result from environmental influences (such as natural hazards) over which they have limited control. The paper on Rameswaram Island is a significant, but rare, example of a detailed field investigation of relationships between population movements and malaria, undertaken with interdisciplinary and longitudinal perspectives (see also [14]). Abstract-The role of population movement on the persistent transmission of malaria in Rameswaram Island was studied. Majority of the inhabitants of the island are fishermen, who engage in perennial fishing. They move from one coastal place to the other for fishing and stay in temporary camps depending on season and fish availability. Such seasonal fishing camps attract fishermen from the mainland coastal villages also. The parasitological and entomological studies carried out in these places reveal that some of the camps are highly vulnerable to the movement of individuals with malaria infection and highly receptive. Rameswaram being a holy place, receives pilgrims from all over India and Nepal. Phsmodium falciparum cases recorded from the pilgrims of North India indicate the danger of the possible introduction of chloroquine-resistant parasite in the island. Also, a large number of passengers in transit from various countries, many of which are at risk of malaria transmission, stay in the island before or after visiting Sri Lanka. Such population movements being a continuous and regular feature are significant and result in failures in the operational programmes. INTRODUCTION
Population movement is one of the important factors having impact on malaria prevalence. It has been the
major reason for many outbreaks, spreading of drug resistant strains of parasites, failure of control operations etc. in different parts of the world. Though the
Population movement and malaria Persistence in Rameswaram Island importance of population movement in malaria epidemiology has been recognized, due consideration has not been given to this aspect of the disease in planning and implementation of control programmes. It is only recently that the need for research on this aspect is emphasized and a few studies have been initiated in some countries, where population movements pose a major problem for disease control. A study was carried out by the Vector Control Research Centre, Pondicherry on the role of population movement in persistence of malaria transmission in Rameswaram Island, Tamil Nadu and the results are presented. Rameswaram island (09’16’N, 79’18’E) with an area of 55 km’ and a population of about 56,000 (198 1 census) is not only an important pilgrim centre for the Hindus, attracting visitors from all over India, but is also a fishermen’s paradise as the physiographic features favour year round fishing. Therefore, the majority of the local inhabitants are either fishermen or are engaged in the fishing industry. Strategically located between India and Sri Lanka, the island is connected with Mandapam in the mainland by a 3 km-long rail bridge (there is no road connection) across Palk strait. There is a regular ferry service between Rameswaram and Sri Lanka (23 km distance) every alternate day which enables, movement of people between India and Sri Lanka through the island. Extensive studies carried out by the Vector Control Research Centre on malaria and its vector in the island showed that there is perennial transmission of malaria and a large number of positive cases (both Plasmodium cicax and P. falciparum) transmitted by Anopheles culicifncies was recorded year after year since 1974 [15-171. Fishermen regularly move from one place to another within the island, between the coastal mainland villages and the island and this population movement coupled with the socioeconomic aspects of fishing and the peculiar topography of the island contributes in a large measure to perpetuate malaria transmission in the island and in the coastal villages of the mainland. These factors were studied during 1982-1984 and described below. MATERIAL AND iMETHODS
Fishermen movement was monitored by questioning them in various camps and also by the VCRC staff accompanying them whenever possible. A card was made for each migrating family, where all data was recorded. Entomological collection, fever surveys and mass blood surveys for malaria were made following standard procedures and the data recorded and analysed. Additional information on movement of tourists including pilgrims and transit passengers to Sri Lanka and India was kindly provided by the Department of Tourism, Port Office and Choultries. Data on malaria incidence were provided by the State NMEP. SPECIAL FEATURES OF THE ISLAND
The island Dhanushkodi. 45 km away Adam’s bridge,
lies west to east from Pamban to Talaimannar in Sri Lanka is about from Dhanushkodi, connected by which is a chain of shoals separating
881
Palk Bay in the north and Gulf of Mannar in the south. Some of the sand banks along Adam’s bridge are dry and nowhere are the shoals deeper than 1 m. No boat sails across Adam’s bridge. Pamban. on the western side of the island, is connected to the mainland by a rail bridge constructed over a century ago, and to enable ferry boats to pass under, one span in the middle is lifted mechanically. This facility is not. however, used frequently. However, all kinds of boats can easily pass below this span of the rail bridge. The sea around the entire island is relatively shallow- and the depth is not more than 30m for considerable distance around the island and as a result the sea is calm without much wave action. Therefore. fishing takes place around the island throughout the year. South-west monsoon (June-August) is weak while the north-east monsoon (September-December) is strong. The fishing activities are more intense on the south bay of the island which is relatively calm from December to June and as a result several fishermen camps are established in the southern shores. Apart from fishermen moving from northern part of the island to southern part, there is a regular movement of fishermen from the coastal areas of the mainland, the districts of Thanjavur, Pudukkottai, Ramnad, Tirunelveli and Kanya-kumari in Tamil Nadu to the camps in the island. The sea along the mainland coast between point Calimere in Thanjavur district and Mandapam in Ramnad district is also relatively calm because of the peculiar topography, but becomes rough during and in the months following the northeast monsoon. This is one of the reasons why a large scale movement of fishermen takes place from the mainland villages to the island. Over 30 varieties of fish, prawns and crab are available around Rameswaram Island throughout the year. The daily catch of fish, prawns etc. amounts to Rs. 5.00,OOO (us%50,000). Rameswaram, being one of the holy places for Hindus, attracts pilgrims from all over India and Nepal throughout the year, their number varying between 1000-4000 per day. Many of them come from some states of India where resistant strain of P. falciparum has been reported. They usually stay for a day or two in the island. Several adventurous groups from mainland have also, in recent years, migrated to certain areas of the island to eke out a living. While some of them have taken to fishing, most others are engaged in odd job-not excluding stealing of firewood from casuarina plantations (belonging to the Government of Tamil Nadu) and selling them for profit, smuggling and illicit distillation of liquor. There are several settlements like this which have come up in the island during the last decade, the most recent one being Muthuramalingapuram, which is highly malarious, with about 100 families. The induction of a relatively large susceptible population in these new settlements is a factor for high malaria prevalence in the island, particularly in view of the fact that these settlements are located near inaccessible casuarina plantations with high vector breeding sources. Since the island is strategically located between India and Sri Lanka, there is a large floating population. Tourists and businessmen from India and many foreign countries pass through the island.
P. K.
SUL F
OF
RUAGOPALAN et al
MANNAR
SCALE
. ,BPIDGE .
Fig. 1. Coastal villages and seasonal fishermen camps in Rameswaram Island PATTERN
OF 1lOVEMEST
OF FISHERMEN
The coastal areas were surveyed and the places where fishermen camps are established year after year were marked and the pattern of movement studied. The seasonal and perennial fishing centres in Rameswaram island are shown in Fig. 1. The seasonal centres are temporary camps on the seashore with thatched huts built by fishermen from other coastal villages during the season and removed later. Duration of each camp depends on fish availability in a particular season. While the duration of some of the camps (Kundukal, Thuraimugam and Dhanushkodi) on the southern shore line extends from 5 to 7 months. the duration of most of the other camps varies between 2-3 months. However, almost all the seasonal camps on the northern sea-shore lasts as long as 7 months. Some fishermen form companies owning diesel-operated launches and stay at the camps near Pamban and Rameswaram (the two places in the island where facilities for harbouring and fuelling launches are available). Fishermen employed in the companies belong to different villages in the island and mainland and are rarely accompanied by their families. These fishermen go to the southern side of the island for fishing in seasons and return the same day. Only those fishermen who are employed in companies owning certain special nets and who own country boats stay with their entire family in the temporary settlements for the entire fishing season which lasts for several months. The pattern of fishermen movement from the mainland coastal villages to Rameswaram Island and vice versa is shown in Fig. 2. The different areas from where people migrate and the season are indicated. Once the fishing season in a particular camp is over, the fishermen either move to another camp or return to their villages, which may be either in the island itself or in the mainland. The number of people from different villages/ districts joining the various camps in the island are shown in Table 1. The bigger camps are in Kundukal, Thuraimugam, Moonramchattram, Dhanushkodi and Vallathadi. In addition, there are several smaller camps with less than 100 fishermen in each. A study
of the population composition in these camps during 1983-1984 showed that out of 6355 people, 2964 were adult males, 1537 were adult females and I854 were children including 205 infants indicating the movement of entire families. SlASS
BLOOD AND FEVER
SURVEYS
The VCRC teams visited the camps within 1 week of their being set up and carried out mass blood surveys to find out whether any cases have been imported. From 11 such camps in rhe island, 4073 blood smears were examined and 138 were found positive for malaria (P. cicax 43; P. falciparum 92; mixed 3) (Table 2). Among the positives, IO7 had no apparent clinical symptoms. About 80% of P. fulciparum cases were recorded from the asymptomatic carriers. Malaria positives were found in all age groups including infants (under 1 year) and children aged 14 years. There were 109 gametocyte carriers confirming the existence of a reservoir to enable subsequent local transmission. Positive cases in the camp included fishermen from mainland villages as well as the coastal villages of the island. Fever survey was carried out regularly, three times a week, in the camp for the entire duration to determine whether local transmission takes place and the data recorded in cards issued to each family. A total of 680 fever cases were examined and 107 were found positive for malaria (P. uivax 75;P.fufciparum 31; mixed 1) (Table 3). Among the positives, those who were examined within 10 days of their arrival at a camp were considered as imported. There are six such imported cases. Based on their malaria history the remaining 101 positives were considered to be new infections (excluding the possibility of recrudescence or relapse). The positive slides were from all age groups including infants and children of 1-4 years of age, confirming local transmission in the camps. RECEPTIVITY
STATUS
The receptivity of the island has always been high as shown by earlier studies [15-l 71. Regular mosquito
Population
movement
and malaria
persistence
in Rameswaram
THANJAVUR
j-k-J
R
RAMNAD
/
TIRUNELVELI
S MANGALA+
883
Island
Dt.
:..
Dt.
Dt.
MUTl4WIPURAM_,.’ ERAL
-4
,._ . . . . -‘:;;.
3
_ RAJAYARGAd
Fig. 2.
1
Ai;AT+flSWARAU
Seasonal migration
pattern
of fishermen
‘I
PftlYARY
HEALTH
.
COASTAL
VILLAGES
in the coastal Island.
I. Pouulation
mizratine
in different
No. of families ScE.Oll
Name of camp
in months
Kundukal Tburaimugam Othathalai Thavakadu Paraiyadi Otha Patti Moonramchatram Dhanushkodi Vallathadi Total
Nov.-Mar. Nov.-Mar. Jan.-Mar. Jan.-Mar. Dec.-Feb. Jan.-Mar. Jan.-Mar. Feb.-Ott. Feb.-July
-Kanyakumari district 0 0 0 0 0 0 103 (648) 0 0 103 (648)
I
of mainland
and Rameswaram
a frequent movement of fishermen between Kundukal camp and Kundukal village. The camp being in such close proximity with Kundukal village with abundant breeding sources is highly receptive for malaria transmission. One sporozoite positive A. culicifacies was found in the camp in March, confirming local transmission. The largest number of positive cases recorded during fever surveys were also from this camp. A. culicifacies was also recorded from Vallathadi camp in the northern shore. This camp is in close proximity to the Nalupanai village where the fishermen from the camp stay during night.
collections carried out in Kundukal camp showed the presence of Anopheles culicifacies in both resting and biting collections. This camp is adjacent to the Kundukal village where A. cuficzjkies was recorded every month from June 1983 to May 1984, with density ranging from 0.17 to 2.83 pmh in different months. The mean hut density ranged from 1.0 to 13.75 during the same period. Breeding sources are abundant in this village. The duration of the Kundukal camp coincides with the season of high vector prevalence (post-monsoon season) and with the peak season in malaria incidence in the island. There is also
Table
villages
CENTRES
(persons)
Tirunelveli district
1(4) 1 (4) 0 0 0
l(4) 3(l6) I (3) 5 (23) I2 (54)
seasons migrated
in different
camos
from the villages
Ramanathapuram district 86 (523) 76 (445) 1(3) 5 (69) 2 (32) 8 (47) IO (55) 25(147) 84 (465) 297 (I 786)
in
Within Rameswaram
Island
347 (1979) 69 (395) IO (80) 30(182) I7 (106) 39 (227) 37 (209) 1I7 (595) 20 (94) 686 (3867)
Total 434 (2506) 146 (844) I I (83) 35 (251) 19(138) 48 (278) I53 (928) 143 (745) I09 (382) 1098 (6355)
P. K.
884
et al.
RAJAGOPALAN
Table 2. Mass blood surveys carried out in the seasonal fishermen camps No. of persons examined
Number positive
Kundukal Thuraimugam Thavakadu South Thavakadu North Paraiyadi Othapatti Moonramchatram South h4oonramchatram North Dhanushkodi South Dhanushkodi North Karaiyur Company Total
I702 469 IM) I77 40 139 I35 90 323 272 626 4073
61 7 4 5 5 IO 2 2 IO I4 IS 138
2 I3
Mainland Mandapam Ervadi (Thonithurai thoppu) Rochmanager village Total
252 61 691 loo4
ia I 24 43
0 I 2
Name of camp
Number with fever P. ciwx
P. falciponrm
Number wnhout symptoms Mixed
P. vitzx
P. falciparum
MIXed
Island
6 I I 0 0 0 0 1 I
I
I
IO 0 0 I 0 2 0 0 0 I 3 17
I
I4
0 0 0 0 0 0 0 0 0 0
I
0 3 0 3 3 0 0 I 4 2 30
II 75
0 0 0 0 0 1
3 0 4 7
0 0 I I
4 I 4 9
IO 0 I3 23
0 0 I I
30 6 0 J I 4 2 I 8
a
0 0 0 0
I I
Sporozoite positive specimens were obtained during blood smears examined, 43 were positive, 10 from the camping period of fishermen in the Nalupanai fever cases and 33 from asymptomatic cases. Sevvillage. The receptivity of the other camps vary. enteen of these were gametocyte carriers. These studThough it was not possible to obtain more accurate ies show that there is a back and forth movement of data, there is the possibility of local transmission in fishermen periodically between mainland villages and some of the other camps. Rameswaram and that they can either be donors or Because these fishermen camps are of a transient recipients for malaria in these places. nature, there is no permanent provision to carry out It may be mentioned here that in terms of species surveillance and treatment under the existing NMEP composition, seasonal prevalence and type of breedset up to cover the population. As a result, most cases ing places of the vector population, season of malaria do not receive radical treatment and therefore when transmission, climatic conditions and vegetation patthe camps are wound up and the fishermen return to tern, the coastal villages in the districts of Pudukottai, their villages, they carry with them the infection, Ramanathapuram and Tirunelveli are similar to thereby creating foci for further transmission in such Rameswaram island. However, the coastal areas of areas where the receptivity is high. An earlier study Ramanathapuram District and Rameswaram Island had shown the presence of gametocyte carriers in are most receptive for malaria transmission because large numbers in some areas of the island and some of the abundance of coconut garden pits and casuof this population also moves to the camps in main- arina plantation pits, where the vector species, A. land [18]. Data collected from Primary Health Cen- culicifacies, breed and where malaria transmission is tres and District Health Units in the mainland (Table also perennial. The degree of receptivity in this area, 4) show that in several PHCs, both indigenous and based on the distribution and numbers of coconut imported cases were recorded by NMEP. These and casuarina gardens with viable pits heavily breedPHCs cover all coastal villages from where fishermen ing A. culicifacies is shown in Fig. 3. This is reflected visit the camps in Rameswaram Island. Thus, there is in the number of malaria cases recorded by different clear evidence of importation of malaria cases from PHCs in the mainland (Table 4), the largest number the island to the mainland. The movement of game- of malaria cases having been recorded in Uchipuli tocyte carriers from the mainland villages to camps in PHC (which includes Rameswaram Island also). The the island also takes place as shown by the results of receptivity decreases as one goes either northwards or mass blood surveys in camps. Mass blood surveys southwards along the mainland coast from Mandacarried out in mainland camps of Mandapam, Ervadi pam. There are also some coastal towns like Kayand Rochmanagar (Table 2) showed that out of 1004 Table 3. Fever survey in fishermen camps in Rameswaram Island Name of camps Kundukal Thuraimugam Othathalai Thavakadu South Paraiyadi Othapatti Moonramchatram South. Dhanushkodi South Vallathadi Karaiyur Companies Total
Number examined
Number positive
335 69 8 9 IO 31 46 106 56 IO 680
77 6 0 I 0 6 ‘2 I4 I 0 107
P. viuax
58 4 0 I 0 0 2 9 I 0 75
P. falciporum
18 2 0 0 0 6 0 5 0 0 31
Mixed
I 0 0 0 0 0 0 0 0 0
I
Population movement and malaria persistence in Rameswaram
Island
885
Table 4. Number of malaria cases recorded in different Primary Health Centres and District Heaith Units of Tamil Nadu, covering the coastal area (1982) data, from State NMEP). Number of malaria cases in Coastal villages PHC;Health Unit
District Pudukottai Ramanathapuram
Tirunelveli Kanyakumari
Ponbethi Kannangudi Pandukudi R. S. Mangalam Devipattinam Uchipulli (1981) (including Rameswaram) T. U. Mangai Kadaladi (198 I) Palayamkottai Sankarankoil Kanyakumari
Indigenous 0 0 IS8 45 319 6475
Interior villages
Imported
Indigenous
Imported
0 0 54 55 I62 0
0 0 0 0 259
2 22 39 23 0 0
24 127 I52’ I62 99
201 0 0 0 0
39 157 235 0 0
48 22 40’ 0 0
7
*Positives recorded only from two coastal towns. Tuticorin and Kayalpattinam
alpattinam and Tuticorin in Tirunelveli District and Thondi in Ramanathapuram District where urban malaria transmitted by Anophefes stephensi breeding in wells and overhead tanks, has been recorded year after year. STUDIES ON PILGRIMS AND TOURISTS
There is also evidence of possible introduction of resistant strains of P. fuiciparum into the island by pilgrims coming from north eastern states of India. In a random study conducted on 640 pilgrims from several states whose blood smears were examined, 11 were found positive for P. falciparum (one from Maharashtra, one from Uttar Pradesh and 9 from
(1981).
Bihar). Ten of them were asymptomatic gametocyte carriers. Chloroquine resistant strains of P. fulciparum has been recorded in all these three states. In Rameswaram, P. fufciparum is known to be still sensitive to chloroquine [19]. Since the piigrims normally stay at least for a day it will not be long before chloroquine resistant strain of P. falciparum becomes established in this island and thus pose more problems for the control of malaria in the island, because of high receptivity in the island. It was ascertained from the Port authorities and the Tourism Department that from January to October 1983, a total of 56,403 people from 52 countries (including South Americas, United States, Europe, Africa and South-East Asian countries) visited Ram-
POINT
RAMNAD
01.
PAMBAN
BRIDGE
1
PAMBAN
b
Gulf
TIRUNELVELI
of
CALWERE
Mannor
Dt
Fig. 3. Receptivity status for malaria (risk of transmission) in Rameswaram Island and coastal mainland (intensity indicated by shading).
P. K. RAJAGOPALASer al.
886
eswaram either for tourism or in transit on their way to Sri Lanka or back. The vast majority of them (51,227) were from Sri Lanka. There were visitors (excluding those from Sri Lanka) from 19 countries of the World where the risk of malaria transmission exists and from five countries (Brazil, Thailand, Indonesia, Burma and Phillippines) where chloroquine resistant P. falciparum is known [20]. About 100,000 Indian settlers, Tamils and Sri Lankans travel by ferry between Sri Lanka and Rameswaram every year. Apart from this, thousands of repatriates from Sri Lanka are coming to India through Rameswaram port every year following the SrimavoaSastri agreement in 1964. A total of 439,521 repatriates have passed through Rameswaram till May 1984. Though sporadic cases of malaria have been recorded among travellers, no systematic study has been done and therefore no data are available on the possibility of malaria being imported into the island by foreigners. But the danger exists. Population movement, particularly fishermen migration, contribute to a large measure to the persistence and high prevalence of malaria not only in Rameswaram Island but also in the coastal areas of mainland. There are several localities where people from malarious areas move to but there are no vector breeding source. In such pockets, malaria could be eliminated by prompt administration of drugs. In other areas, like Kundukal in Rameswaram Island, which are vulnerable to the movement of people from either malarious or non-malarious areas and which are highly receptive because of vector prevalence and favourable season, chemotherapeutic measures should be combined with vector control measures. Under the existing NMEP operational set up, there is not much flexibility in approach and decision makine at the local level due to several constraints includmg lack of adequate facilities to meet the special needs of the situation. While the influence of human ecology has always been recognized in malaria epidemiology, this factor has not received due attention in malaria conrol in this area.
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