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Epidemiology of paragonimiasis in Cross River basin, Nigeria
Public Health (1998) 112, 119±122 ß R.I.P.H.H. 1998
Epidemiology of paragonimiasis in Cross River basin, Nigeria: prevalence and intensity of infection due to Paragonimus uterobilateralis in Yakurr local government area FOI Arene1, E Ibanga2 and JE Asor3 1 Parasitology Unit, Department of Zoology, University of Port Harcourt, PMB 5323, Port Harcourt, Nigeria; 2 Department of Biological Sciences, University of Uyo, Uyo, Nigeria; and 3 Department of Biological Sciences, University of Calabar, Calabar, Nigeria
Prevalence and intensity of paragonimiasis among inhabitants of the Yakurr Local Government Area in the Cross River basin of Nigeria is reported. Diagnosis was based on a single sample detection of eggs of Paragonimus in 5 ml of sputum. 12.27% out of 880 subjects were infected. The infections were due to Paragonimus uterobilateralis. Prevalence of the infection increased with age, up to a peak prevalence of 23.75% (19 out of 108) among subjects between the ages of 17±22 y old. Thereafter, it declined progressively with increase in age to much lower values such that by the age of 53±58 y old, infection had fallen by more than 75%. Prevalence of the infection was signi®cantly higher among females, 13.80% (58 out of 108), than males 11.36% (50 out of 108) (P < 0.009). Intensity of infection (eggs/5 ml sputum) ranged from 12±123 eggs/5 ml sputum, with subjects between the ages of 17±22 y old being the most heavily infected group. Prevalence and intensity of the infection were positively correlated (P < 0.497). The need for control measures to reduce human suffering due to infections in the area, particularly among women and children is emphasized. Keywords: prevalence; intensity; Paragonimus eggs; sputum; Yakurr Local Government Area; Nigeria
Introduction
Methods
Human paragonimiasis has been known in Nigeria since 1943.1 However, little information exists on epidemiology of the infection in the country. Following discovery, in a community health survey of the Cross River basis, of Paragonimus egg in sputum of sixteen inhabitants of the Agoi-Ibami village in the Yakurr Local Government Area, we initiated a pilot survey of the local government area to evaluate the level of infection and gather information on the epidemiological characteristics of paragonimiasis in the area. Aspects of our ®ndings reported here deals with prevalence and intensity of paragonimiasis due to Paragonimus uterobilateralis among inhabitants of the Yakurr Local Government Area, in the Cross River basin in Nigeria. The study was conducted between October, 1995 and March, 1996.
Deep sputum samples from 880 randomly selected inhabitants of the local government area were examined for Paragonimus eggs. The inhabitants examined were between 5 and 65 y old. Both sexes were represented. Sputum produced between 5.00 am and 7.00 am, were sought. Results of the investigation of eggs excretion periodicity in subjects in the area (which is to be published in a separate report) suggested that sputum collected between 5.00 am and 8.00 am would be more meaningful for subsequent investigations. 5 ml of sputum was removed and mixed with 10 ml caustic soda (4% solution) for 20 min at 37 C. The solution was centrifuged at 1200 rpm for 3 min after which the sediment was examined microscopically with the 10 objective lens. The number of sputum samples containing Paragonimus eggs, as well as the number of Paragonimus eggs contained in each of the 5 ml egg-positive sputum samples were recorded. Participants in the survey were motivated by simple explanation and assurance that treatment would be provided free, as indeed it was. A dose of 25 mg/kg praziquantel three times a day for two consecutive days was offered.
The study area Yakurr Local Government Area is located in the Cross River basin, in the Cross River State of Nigeria (8 E and 12 N), Figure 1. The climatic feature of the area is typical of the rainforest zone of Nigeria, with a rainy season which extends from April to October, and dry season months from November to March. Peak rainfall is between June and September. The soil is of the mixed granite and alluvial type. The population is put at 54000 (National Census, 1993), and is made up of the Ibibio speaking ethnic group. Subsistence farming and ®shing are the principal occupations of the people. Health service coverage in the area is poor. Correspondence: Dr FOI Arene. Accepted 27 March 1997
Results Of the 880 sputum samples examined, 12.27% (108 out of 880) were tested positive for Paragonimus eggs. The characteristic yellowish-brown operculate eggs (Plate 1) were morphologically easily identi®ed as those of Paragonimus uterobilateralis.2 The eggs measured on the average 64.0m 6 38.0m in size. Participants in the survey were categorized into eleven age-groups as shown in Table 1. The table shows prevalence of Paragonimus eggs in 5 ml sputum samples of inhabitants of the Yakurr Local
120
Paragonimus infection Nigeria FOI Arene et al
Figure 1 Map of the Cross River State showing study area.
Government Area, by age-group and sex. Prevalence of the infection rose to a peak among the 17±22 y old age group, 23.7% (19 out of 108), after which it declined progressively with increase in age to much lower values such that by the age of 53±58 y, infection had fallen by more than 75%. Prevalence of the infection was signi®cantly higher among females 13.8% (58 out of 108) than males 11.36% (50 out of 108), (P < 0.009).
Distribution of infected subjects based on intensity of infection is shown in Table 2. High egg counts (over 60 eggs/5 ml sputum) were rare in subjects over the age of 40 y. The mean egg count in the 53±58 y old age group was 32.2% of that in the most heavily infected 17±22 y old age group. Prevalence and intensity of the infection were positively correlated (P < 0.495).
Paragonimus infection Nigeria FOI Arene et al
121
The life cycle of the parasite has not been fully described in Nigeria. Two species, Paragonimus africanus and Paragonimus uterobilateralis, are known to occur in West Africa. Freshwater snails belonging to two genera, Afroloomus and Potadoma; and freshwater crabs belonging to three genera; Sudanonautes Libernautes and Potamonemus are suspected ®rst and second intermediate hosts respectively, of Paragonimus uterobilateralis in the rainforest zone of West Africa. If either or both of these intermediate hosts of the parasite could be shown to be naturally infected in the local government area, that would help to elucidate the epidemiology of the infection in the area. These studies are indicated and are being conducted in our unit. The overall prevalence rate of 12.27% recorded in the present study is higher than earlier records of the infection in Okigwe area of eastern Nigeria; 5±10%,3 and in the neighbouring parts of south-western Cameroon; 5.6%.4 These earlier studies also showed that more females than males were infected, as was the case in the present study. The reason for the difference in the prevalence between the sexes recorded in the present study is not obvious. Epidemiology of paragonimiasis is linked with the habit of consuming raw or undercooked freshwater crabs. Crab is one of the common food items of rural communities in the Cross River basin of Nigeria. The crabs are either roasted on open ®res or boiled in sauces used for eating a variety of local dishes. In Yakurr community, it is the traditional role
Plate 1 Egg of P. uterobilateralis in sputum of infected people in the Yakurr Local Government Area of the Cross River Basin, Nigeria.
Discussion The present study established the prevalence of paragonimiasis due to Paragonimus uterobilateralis in the Yakurr Local Government Area, in the Cross River basin of Nigeria. The high prevalence and intensity of the infection particularly among children should be of serious concern to relevant health authorities in the area. Interviews with the infected persons indicated that most of them acquired the infection in the local government area.
Table 1 Prevalence of infection with Paragonimus uterobilateralis among inhabitants of the Yakurr Local Government Area of Cross River Basin, Nigeria in relation to age and sex Age group (years)
Number of persons examined
Total number positive (%)
Number Positive
Female
Male
Female No. (%)
Male No. (%)
40 40 40 40 40 40 40 40 40 40 40
40 40 40 40 40 40 40 40 40 40 40
3(7.5) 6(15.0) 10(25.0) 8(20.0) 7(17.5) 6(15.0) 5(12.5) 4(10.0) 4(10.0) 3(7.5) 2(5.0)
2(5.0) 7(17.5) 9(22.5) 7(17.5) 7(17.5) 5(12.5) 3(7.0) 3(7.5) 2(5.0) 4(10.0) 1(2.5)
5±10 11±16 17±22 23±28 29±34 35±40 41±46 47±52 53±58 59±64 > 64
5(6.25) 13(16.25) 19(23.75) 15(18.75) 14(17.50) 11(13.75) 8(10.00) 7(8.75) 6(7.50) 7(8.75) 3(3.75)
Table 2 Distribution of number of persons infected with Paragonimus uterobilateralis in the Yakurr Local Government Area in Cross River Basin, Nigeria into six categories based on intensity of infection (egg counts in 5 ml sputum) by age group Age group (years)
Number of persons examined in each age group
Number of persons infected
5±10 11±16 17±22 23±28 29±34 35±40 41±46 47±52 53±58 59±64 > 64
80 80 80 80 80 80 80 80 80 40 40
5 13 19 15 14 11 8 7 6 7 3
Intensity of infection (eggs/5 ml sputum) < 20
20±39
40±59
60±79
80±99
100
0 0 0 1 0 2 1 2 3 3 0
0 0 2 1 2 2 2 3 2 3 2
2 4 4 4 5 6 3 2 1 0 1
2 5 7 5 3 1 2 0 0 1 0
1 4 4 2 2 0 0 0 0 0 0
0 0 2 2 2 0 0 0 0 0 0
122
Paragonimus infection Nigeria FOI Arene et al
of females to prepare food for the families. Contamination of ®ngers or cooking utensils during food preparation is considered a factor in the transmission of the paragonimiasis.5 Children in the study area frequently collect crabs from nearby streams. While doing their collection, the children occasionally consume raw, broken-off parts of the crab's tissues6 and hence may contribute to the higher prevalence of the infection recorded in children. Some of the cases seen during the survey experienced severe morbidity. Despite the high prevalence and intensity of the infection, the disease has drawn very little attention in the local government area. There has as yet, been no control programme to deal with the infection in the area. This is urgently needed to reduce suffering due to the infection, particularly among women and children in the area. Acknowledgement This work was supported by University of Port Harcourt Senate Research Grant.
References 1 Nwokolo C. Paragonimiasis in Eastern Nigeria. J. Trop Med Hyg 1964; 67(1): 1±4. 2 Sachs R, Albeiz EJ, Voelker J. Prevalence of Paragonimus uterobilateralis infection in children in a Liberian village. Trans Roy Soc Trop Med Hyg 1986; 80(5): 800±801. 3 Nwokolo C. Endemic paragonimiasis in Africa. Bull Wld Hlth Org 1974; 50: 569±571. 4 Kum PN, Nchinda TC. Pulmonary paragonimiasis in Cameroon. Trans Royal Soc Trop Med Hyg 1982; 76(6): 768±772. 5 Suzuki Z. Epidemiological studies on paragonimiasis in South Izu district, Shizouka. Prefecture, Japan. 6 Saachs R, Cumberlidge N. Distribution of metacercariae in freshwater crabs in relation to Paragonimus infection of children in Liberia, West Africa. Ann Trop Med Parasit 1990; 84(3): 277±280.
Epidemiology of paragonimiasis in Cross River basin, Nigeria: prevalence and intensity of infection due to Paragonimus uterobilateralis in Yakurr local government area FOI Arene1, E Ibanga2 and JE Asor3 1 Parasitology Unit, Department of Zoology, University of Port Harcourt, PMB 5323, Port Harcourt, Nigeria; 2 Department of Biological Sciences, University of Uyo, Uyo, Nigeria; and 3 Department of Biological Sciences, University of Calabar, Calabar, Nigeria
Prevalence and intensity of paragonimiasis among inhabitants of the Yakurr Local Government Area in the Cross River basin of Nigeria is reported. Diagnosis was based on a single sample detection of eggs of Paragonimus in 5 ml of sputum. 12.27% out of 880 subjects were infected. The infections were due to Paragonimus uterobilateralis. Prevalence of the infection increased with age, up to a peak prevalence of 23.75% (19 out of 108) among subjects between the ages of 17±22 y old. Thereafter, it declined progressively with increase in age to much lower values such that by the age of 53±58 y old, infection had fallen by more than 75%. Prevalence of the infection was signi®cantly higher among females, 13.80% (58 out of 108), than males 11.36% (50 out of 108) (P < 0.009). Intensity of infection (eggs/5 ml sputum) ranged from 12±123 eggs/5 ml sputum, with subjects between the ages of 17±22 y old being the most heavily infected group. Prevalence and intensity of the infection were positively correlated (P < 0.497). The need for control measures to reduce human suffering due to infections in the area, particularly among women and children is emphasized. Keywords: prevalence; intensity; Paragonimus eggs; sputum; Yakurr Local Government Area; Nigeria
Introduction
Methods
Human paragonimiasis has been known in Nigeria since 1943.1 However, little information exists on epidemiology of the infection in the country. Following discovery, in a community health survey of the Cross River basis, of Paragonimus egg in sputum of sixteen inhabitants of the Agoi-Ibami village in the Yakurr Local Government Area, we initiated a pilot survey of the local government area to evaluate the level of infection and gather information on the epidemiological characteristics of paragonimiasis in the area. Aspects of our ®ndings reported here deals with prevalence and intensity of paragonimiasis due to Paragonimus uterobilateralis among inhabitants of the Yakurr Local Government Area, in the Cross River basin in Nigeria. The study was conducted between October, 1995 and March, 1996.
Deep sputum samples from 880 randomly selected inhabitants of the local government area were examined for Paragonimus eggs. The inhabitants examined were between 5 and 65 y old. Both sexes were represented. Sputum produced between 5.00 am and 7.00 am, were sought. Results of the investigation of eggs excretion periodicity in subjects in the area (which is to be published in a separate report) suggested that sputum collected between 5.00 am and 8.00 am would be more meaningful for subsequent investigations. 5 ml of sputum was removed and mixed with 10 ml caustic soda (4% solution) for 20 min at 37 C. The solution was centrifuged at 1200 rpm for 3 min after which the sediment was examined microscopically with the 10 objective lens. The number of sputum samples containing Paragonimus eggs, as well as the number of Paragonimus eggs contained in each of the 5 ml egg-positive sputum samples were recorded. Participants in the survey were motivated by simple explanation and assurance that treatment would be provided free, as indeed it was. A dose of 25 mg/kg praziquantel three times a day for two consecutive days was offered.
The study area Yakurr Local Government Area is located in the Cross River basin, in the Cross River State of Nigeria (8 E and 12 N), Figure 1. The climatic feature of the area is typical of the rainforest zone of Nigeria, with a rainy season which extends from April to October, and dry season months from November to March. Peak rainfall is between June and September. The soil is of the mixed granite and alluvial type. The population is put at 54000 (National Census, 1993), and is made up of the Ibibio speaking ethnic group. Subsistence farming and ®shing are the principal occupations of the people. Health service coverage in the area is poor. Correspondence: Dr FOI Arene. Accepted 27 March 1997
Results Of the 880 sputum samples examined, 12.27% (108 out of 880) were tested positive for Paragonimus eggs. The characteristic yellowish-brown operculate eggs (Plate 1) were morphologically easily identi®ed as those of Paragonimus uterobilateralis.2 The eggs measured on the average 64.0m 6 38.0m in size. Participants in the survey were categorized into eleven age-groups as shown in Table 1. The table shows prevalence of Paragonimus eggs in 5 ml sputum samples of inhabitants of the Yakurr Local
120
Paragonimus infection Nigeria FOI Arene et al
Figure 1 Map of the Cross River State showing study area.
Government Area, by age-group and sex. Prevalence of the infection rose to a peak among the 17±22 y old age group, 23.7% (19 out of 108), after which it declined progressively with increase in age to much lower values such that by the age of 53±58 y, infection had fallen by more than 75%. Prevalence of the infection was signi®cantly higher among females 13.8% (58 out of 108) than males 11.36% (50 out of 108), (P < 0.009).
Distribution of infected subjects based on intensity of infection is shown in Table 2. High egg counts (over 60 eggs/5 ml sputum) were rare in subjects over the age of 40 y. The mean egg count in the 53±58 y old age group was 32.2% of that in the most heavily infected 17±22 y old age group. Prevalence and intensity of the infection were positively correlated (P < 0.495).
Paragonimus infection Nigeria FOI Arene et al
121
The life cycle of the parasite has not been fully described in Nigeria. Two species, Paragonimus africanus and Paragonimus uterobilateralis, are known to occur in West Africa. Freshwater snails belonging to two genera, Afroloomus and Potadoma; and freshwater crabs belonging to three genera; Sudanonautes Libernautes and Potamonemus are suspected ®rst and second intermediate hosts respectively, of Paragonimus uterobilateralis in the rainforest zone of West Africa. If either or both of these intermediate hosts of the parasite could be shown to be naturally infected in the local government area, that would help to elucidate the epidemiology of the infection in the area. These studies are indicated and are being conducted in our unit. The overall prevalence rate of 12.27% recorded in the present study is higher than earlier records of the infection in Okigwe area of eastern Nigeria; 5±10%,3 and in the neighbouring parts of south-western Cameroon; 5.6%.4 These earlier studies also showed that more females than males were infected, as was the case in the present study. The reason for the difference in the prevalence between the sexes recorded in the present study is not obvious. Epidemiology of paragonimiasis is linked with the habit of consuming raw or undercooked freshwater crabs. Crab is one of the common food items of rural communities in the Cross River basin of Nigeria. The crabs are either roasted on open ®res or boiled in sauces used for eating a variety of local dishes. In Yakurr community, it is the traditional role
Plate 1 Egg of P. uterobilateralis in sputum of infected people in the Yakurr Local Government Area of the Cross River Basin, Nigeria.
Discussion The present study established the prevalence of paragonimiasis due to Paragonimus uterobilateralis in the Yakurr Local Government Area, in the Cross River basin of Nigeria. The high prevalence and intensity of the infection particularly among children should be of serious concern to relevant health authorities in the area. Interviews with the infected persons indicated that most of them acquired the infection in the local government area.
Table 1 Prevalence of infection with Paragonimus uterobilateralis among inhabitants of the Yakurr Local Government Area of Cross River Basin, Nigeria in relation to age and sex Age group (years)
Number of persons examined
Total number positive (%)
Number Positive
Female
Male
Female No. (%)
Male No. (%)
40 40 40 40 40 40 40 40 40 40 40
40 40 40 40 40 40 40 40 40 40 40
3(7.5) 6(15.0) 10(25.0) 8(20.0) 7(17.5) 6(15.0) 5(12.5) 4(10.0) 4(10.0) 3(7.5) 2(5.0)
2(5.0) 7(17.5) 9(22.5) 7(17.5) 7(17.5) 5(12.5) 3(7.0) 3(7.5) 2(5.0) 4(10.0) 1(2.5)
5±10 11±16 17±22 23±28 29±34 35±40 41±46 47±52 53±58 59±64 > 64
5(6.25) 13(16.25) 19(23.75) 15(18.75) 14(17.50) 11(13.75) 8(10.00) 7(8.75) 6(7.50) 7(8.75) 3(3.75)
Table 2 Distribution of number of persons infected with Paragonimus uterobilateralis in the Yakurr Local Government Area in Cross River Basin, Nigeria into six categories based on intensity of infection (egg counts in 5 ml sputum) by age group Age group (years)
Number of persons examined in each age group
Number of persons infected
5±10 11±16 17±22 23±28 29±34 35±40 41±46 47±52 53±58 59±64 > 64
80 80 80 80 80 80 80 80 80 40 40
5 13 19 15 14 11 8 7 6 7 3
Intensity of infection (eggs/5 ml sputum) < 20
20±39
40±59
60±79
80±99
100
0 0 0 1 0 2 1 2 3 3 0
0 0 2 1 2 2 2 3 2 3 2
2 4 4 4 5 6 3 2 1 0 1
2 5 7 5 3 1 2 0 0 1 0
1 4 4 2 2 0 0 0 0 0 0
0 0 2 2 2 0 0 0 0 0 0
122
Paragonimus infection Nigeria FOI Arene et al
of females to prepare food for the families. Contamination of ®ngers or cooking utensils during food preparation is considered a factor in the transmission of the paragonimiasis.5 Children in the study area frequently collect crabs from nearby streams. While doing their collection, the children occasionally consume raw, broken-off parts of the crab's tissues6 and hence may contribute to the higher prevalence of the infection recorded in children. Some of the cases seen during the survey experienced severe morbidity. Despite the high prevalence and intensity of the infection, the disease has drawn very little attention in the local government area. There has as yet, been no control programme to deal with the infection in the area. This is urgently needed to reduce suffering due to the infection, particularly among women and children in the area. Acknowledgement This work was supported by University of Port Harcourt Senate Research Grant.
References 1 Nwokolo C. Paragonimiasis in Eastern Nigeria. J. Trop Med Hyg 1964; 67(1): 1±4. 2 Sachs R, Albeiz EJ, Voelker J. Prevalence of Paragonimus uterobilateralis infection in children in a Liberian village. Trans Roy Soc Trop Med Hyg 1986; 80(5): 800±801. 3 Nwokolo C. Endemic paragonimiasis in Africa. Bull Wld Hlth Org 1974; 50: 569±571. 4 Kum PN, Nchinda TC. Pulmonary paragonimiasis in Cameroon. Trans Royal Soc Trop Med Hyg 1982; 76(6): 768±772. 5 Suzuki Z. Epidemiological studies on paragonimiasis in South Izu district, Shizouka. Prefecture, Japan. 6 Saachs R, Cumberlidge N. Distribution of metacercariae in freshwater crabs in relation to Paragonimus infection of children in Liberia, West Africa. Ann Trop Med Parasit 1990; 84(3): 277±280.