- Email: [email protected]
Leishmaniasis in Central Brazil: Results of a Montenegro skin test survey among Amerindians in the Xingu National Park
671 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE.
Vol. 64.
No. 5.
1970.
L E I S H M A N I A S I S IN C E N T R A L BRAZIL: R E S U L T S OF A M O N T E N E G R O SKIN T E S T S U R V E Y A M O N G A M E R I N D I A N S IN T H E X I N G U N A T I O N A L PARK D. L. ASTON AND A. P. THORLEY Members of the Royal Society and Royal Geographical Society Xavantina-Cachimbo Expedition
Introduction T h e clinical disease, mucocutaneous leishmaniasis or espundia, has long been recognized in the central regions of Brazil but little is known of its incidence or epidemiology. Recently LAtNSON and SHAW (1968) and SrIaw and LAmSON (1968) examined the epidemiological situation in the Lower Amazon Basin and have established a mammalian reservoir and insect vectors in that area. Further epidemiological studies are being carried out by these workers in undeveloped areas of Central Brazil (LAmsoN and SHAW 1969). Although brief reports of clinical leishmaniasis in the Upper Xingti region have been made (CARNERIet al. 1963, CARNEaI 1964), nothing is known of the incidence of the disease among indigenous peoples in these areas. This paper describes the results of a Montenegro skin test survey for mucocutaneous leishmaniasis in eight villages of protected Amerindians in the Xingti National Park.
Materials and methods The subjects of the survey were made up of the whole available population of each village, only excitable infants being excluded. Subjects were examined for active primary lesions, old scars and signs of secondary involvement. Characteristically the Indians of the Upper Xingd are naked, and this considerably facilitates a speedy examination. Lesions were scraped with a sterile blade and the sample was smeared on to a glass slide. After being fixed in methanol and stained with Giemsa, it was examined under a microscope for Leishmania braziliensis. Past or present infection by L. braziliensis resulting in antibody formation was detected by use of the Montenegro antigen skin test. Positive reactions to L. braziliemis antigen from other leishmanial species e.g.L, donovani are rare, even with subjects known to be infected with visceral leishrnaniasis in an area where both visceral and mucocutaneous forms are endemic (PESSOAand LOPES 1963). The antigen used in our study was prepared from a culture of L. braziliensis at the Wellcome Parasitological Laboratories, Instituto Evandro Chagas, Belem. The antigen was diluted 1/100 with physiological saline, and a control was also prepared consisting of physiological saline containing 0.5% phenol to allow for the phenolized antigen.
*All correspondence to A. P. Thorley, U.C.H. Medical School, University Street, London, W.C.1. Apart from the generous sponsors of the expedition, the authors would like to thank Professor P. C. C. Garnham for his interest and encouragement, Dr. R. Lainson and Dr. J. J. Shaw for supplying the antigen, Mr. I. Bishop, leader of the expedition, for much practical assistance, and Sr. Orlando Vilas Boas, warden of the Xingti National Park, for hospitality and permission to work in the Indian communities.
LEISHMANIASIS IN CENTRAL BRAZIL
672
Both forearms were cleaned with 70% alcohol, and 0.1 ml. of the antigen and control were injected subcutaneously into the flexor surfaces of the right and left forearms respectively. Gillette gamma-irradiated disposable syringes (1 "0 ml. tuberculin-type) and disposable needles (25G × 8~ in., No. 20) were used and were most satisfactory under difficult conditions. T h e injection sites were ringed with indelible marker, and examined and graded by one of us (A.P.T.) after 48 hours, according to the following scheme: (a) Negative--no induration or erythema. (b) Doubtful--area of induration less than 3 mm. in diameter, with or without erythema. (c) Positive--area of induration more than 3 mm. in diameter, with erythema present. This scheme of gradation follows closely the one used in a previous survey by one of the authors in British Honduras (CI-IALMERSet al., 1968). Local information regarding the individual communities was gathered at the National Park headquarters. Note was made of the age of each Indian examined and skin tested. As Indians do not measure age in years, the ages were gained from anthropologists or other workers in the villages concerned, or assessed as accurately as possible by the authors. This survey was carried out in the dry season during the month of August 1968.
Selection of subjects T h e ideal subjects for study were to be isolated indigenous communities with little regional movement and little or no contact with Europeans. Previous experience in British Honduras (CI-IALMERSet al., 1968) had shown that a village with a population not greater than 200 was the most practical size for a pair o f workers to deal with in one day. ,Ws3*30' ;~(.-
//>'-
4"
~~>-,i, ~" 9
//S . /J
~;.-"
Waura ,fro ,I!
(
,t )
ij
I I
~o
Karnayura(~\~
k
Txik~o-,\'~
}
~/~¢/I{
Posto Leonardo->oe~.~ Yawalap" ' "I? //
? '~
~
/
MAP.
-×\
P
i '/ i
[
/
"~..
0
5,
/'
f
,~
12~00' ~"o Matlpu
L] ° Katapal°s
)~
..... ,,,
t'
)
,s
Kulkuru
""::\l
Indian Villages in southern part of Xingfi National Park.
T h e Indians in the southern part o f the Xing6 National Park have lived in the U p p e r Xing~ Basin (see map) for many generations, with minimal contact with Euro-
D. L. ASTON AND A. P. THORLEY
673
peans. During the last 25 years, in order to prevent their rapid extinction they have been encouraged to move their villages closer to the National Park headquarters at Posto Leonardo Vilas Boas, where basic medical facilities exist. At present they are stringently protected from contact with infectious diseases common in other parts of Brazil, and entry to the Park is restricted to anthropologists and other scientific workers. There are 9 villages of closely related Indians with a total population of 600 in the southern part of the National Park. Individual villages have populations ranging from 40 to 150, and in the dry season all can be reached within one day on foot and by canoe. As they have had some contact with scientific workers, the Indians are helpful and cooperative with visitors who show courtesy and strictly respect their ways and customs. Each village has its own Indian language, but usually a few of the men speak a little Portuguese and this served as a common language of communication. The Upper Xingd Basin lies between 600 and 1,500 feet above sea level, and the region in which the villages are situated is subject to gross annual flooding in the wet season. The vegetation in the area is varied and includes open campos limpos (treeless grasslands), cerrado (savanna woodland) and tall "dry" (semi-deciduous) forest.
Results The authors visited 8 of the 9 Indian villages, and 400 Indians were successfully examined and skin tested, this being 66°~, of the total population.
Evidence of clinical lesions No active primary or secondary lesions were observed. Only one infected lesion was seen which resembled a leishmanial lesion, but microscopic examination of a smear clearly showed a staphylococcal infection. Between late 1962 and the end of 1964 many people in the Waurfi tribe were diagnosed at the National Park headquarters as being infected with primary lesions. This phenomenon had not been reported before in the area, and may be best described as an epidemic (CARNERIet al., 1963). The lesions proved unresponsive to any treatment other than a course of antimonial drugs. The time spent at the Park headquarters while receiving the course of injections was vividly remembered. We examined 71 out of the 97 members of the Waur~ tribe and found 11 males and 5 females with old scars of leishmanial infection.
The Montenegro skin test Control tests were made on 123 Indians, the 71 Waurfi and 6 to 10 members chosen at random from each of the other tribes. The results of the control tests are compared with those of the antigen tests in Table I. Detailed results of the antigen tests for each tribe may be found in Table II. The results for males and females of all tribes are presented graphically in Figure 1, the percentage of positive Montenegro reactions being plotted for each group. The incidence of doubtful reactions and false positive reactions was neglible compared with the incidence of positive reactions (see Table I), and thus will not be considered in the discussion.
674
LEISHMANIASIS IN CENTRAL BRAZIL TABLE I.
Sex
÷
±
M
162
4
46
212
F
88
4
96
188
Total
250
8
142
400
Total
Antigen
%
62.5
2"0
Sex
÷
±
35-5
100 Total
M
5
76
81
F
1
40
42
1
6
116
123
0'8
4-9
Control Total
%
94"3
100
+ = Positive Montenegro reaction 5: = Doubtful reaction - - = Negative reaction
Mates Fema|es
*/a 100 90 I
80
!--
70 I--
BO 50 /-,0 30 20 10 0 0-5 6-10
FIG. 1.
11- 20
21-30
31 -/.0
1.1 -
50
50+ Years
T h e number of positive Montenegro reactions in succeeding age groups expressed as a percentage of the total number of males or females in each group.
D.
L.
ASTON
AND
A. P.
675
THORLEY
TABLE II.
Tribe
Sex
Montenegro Test
Age <5 +
M
6-
5: --
+
10
11 - 2 0 I 2 1 -
5: -- +
1
±
30
3_
3
1
31 - 4 0
41 - 5 0
~ 5: --
+
1
1
M
2 1
1
1
1
4
1 3
F
1
2 4
2
4
Txikao 6
M
2
2
9
F
2
2
4
12
1
9
M
1
1
i
3
1
5
4
3
2
3
2
3
6
4
4
3
1 6
Kamayura F
2
M
J
8
50
2
1
12
1
5
67
10
29
1
1 3
1
1
5
1
5
3
M
2
4
2
3
4
5
3
i
1
12
1
4
7
2
1
2
5
F
10
M
2
4
F
6
2
Matipu M
4
22 22
F
7
29
5
+ = :c = -- =
5
2
t
4] 4 3[ 42
24 15
2 22 28
4 22
1
15
2
2 1
2
38
3
93
21
9
70
2
26
2
13
63
13
1
11
52 66
2
21
11
11
21
36
1
15
7
68
20
23
1
1
3
2
1
4 32
2 17 19
81 88
1
1 1
4
1
3 3
4
3 16 4 3
Totals 9
3
21
2
1 1
3
9
2
Kalapalos
I
4
Kuikuru F
93
1
1
3
1
9
1
6
%+
13
2
1 10 3
-
1
Waura 2
5:
2
2
6
_
4
1
12
F
5
1t4
Mehinaku M
i 3
.
7
Yawalapiti F
±
Totals
50+
6 1
15
2
88
9
17
29
1 10
9
162
4
46
76
4
2
I 88
4
96
47
8
I
Positive M o n t e n e g r o reaction. Doubtful reaction Negative reaction.
Discussion The Indians in the Xingti National Park comprise one of the best groups of protected communities in Brazil and simple clinical surveys can be carried out with little prior experience of working in Indian villages. Although the subjects were most cooperative at the time of receiving the injections, they often remained puzzled and indifferent when we wished to re-examine the arms after 48 hours. On some occasions groups of Indians were missed because they had left the village on a long fishing trip or were involved in religious ceremonies. These are unavoidable inconveniences, and in the circumstances we were fortunate in being able to cover two thirds of the population in such a short time. Be¢ore working with the Indians, we were able to examine and skin test 30 Brazilians on a small fazenda on the road 100 km. south east of the National Park. This squatters' farm, set in cerrado country, had been established some 2 years, and the squatters were poor Brazilians from all over Central Brazil. The results of this pilot survey are not detailed enough to record in the results section as the population is so varied, but it is useful to make reference to them when considering the Indian results. At the single fazenda that was tested, 20 (66%) of the Brazilians had positive reactions, 5 had active primary lesions and 2 others had secondary nasal involvement. We saw only one case of active secondary involvement which may have developed from an active infection contracted in the region. The number of active lesions found on the fazenda contrasts strongly with the fact that no active lesions were found among the Indians. Within the limits of language
676
LEISHMANIASIS I N CENTRAL BRAZIL
and understanding, all the Indians were carefully questioned about primary lesions and secondary involvement and, the Waur~i excepted, there were no reports of such lesions. The Indians were found to be particularly free from scars of any nature, and when questioned, invariably connected them with a specific cut or similar trauma. Although this important difference exists with regard to active lesions, the high percentage of positive reactions among the Indians is very similar to that found among the Brazilians on the fazenda. There is no clear explanation for these findings, but it may be that there are inherent hereditary differences in resistance to clinical leishmaniasis between Indians and Brazilians or that there are strains of Leishmania braziliensis with different virulences in different regions. The high "subclinical" infection rate among the Indians may thus be associated with a small transient lesion, i.e. insect bite, but this passes unnoticed and does not leave any visible scar. Factors which may be of importance are hygiene and nutrition. Under normal conditions the Indian .is healthy and enjoys an abundant diet of fish and manioc, and in some villages game, birds, sugar cane, forest fruits and belries are also eaten. Malnutrition and a low standard of hygiene were common findings at the fazenda. The Indian maintains a high level of body cleanliness, bathing several times a day in the river or lagoon, and rubbing his body surface with a vegetable dye called uruku. This dye is a very effective fly repellent and is used particularly in the wet season when biting flies are in abundance. Thus it may be argued that the Indian is less likely to be bitten by a phlebotomine vector, and i f a primary lesion did occur, secondary bacterial infection would be less likely. It may be assumed that the high percentage of positive reactions correlates with a high biting incidence of infected flies, but no regional differences in infection rates can be discerned. The differences between the percentages of positive reactions for individual villages have been examined and compared, but they are insufficiently large to correlate in any way with subjectively observed differences in local predominating vegetation. It must be noted that the Indians move freely over this whole region and hence are exposed to the bites of insects in all vegetations. The epidemic of leishmaniasis which affected almost a fifth of the Waurfi tribe is particularly interesting and may be an exception to the apparent regional equality in infection rates. The outbreak began a few months after the village had been moved to its present site from an earlier one 4 hours canoe journey up the Rio Batovi. The present site is surrounded on three sides by high dry forest. Prior to the move, it may be assumed that the immunity and ;nfection rates showed the same characteristics as those of any, other comparable tribe in the Park. However, several Indians suffered more than one lesion. CARNERIet al. (1963), in reporting the epidemic up to September 1963 found 9 males and 3 females with active lesions. These authors were particularly impressed by multiple lesions observed on the buttocks of the women, and speculate that these were due to infection by phlebotomines that fly close to the ground, as the women sit outside the huts for long periods each day preparing manioc. I f active infection does occur in this manner, and evidence discussed below suggests that this is unlikely, we would expect to find lesions on other parts of the body close to the ground when sitting or squatting e.g. calves, knees, ankles. By late 1964 the epidemic was over, and when we visited the tribe in 1968 there were no active lesions. We found only 5 females with old scars from primary lesions, and consider that with this small number it is unrealistic to attempt generalizations about modes of infection. 2 had multiple scars on the buttocks or upper thigh, and the others had single or multiple scars distributed randomly, as had the men. Thus it is our opinion that the random siting of old
D. L. ASTON AND A. P. THORLEY
677
lesions as found in both sexes does not appear to indicate infection taking place during any specific social activity. Of the 11 Waur~i males that we found with scars, 7 were children aged between 5 and 10 years, and no infected persons were under 5 or over 40 years. As the older men and women were unaffected after the move, presumably because of their effective resistance, it is assumed that the tribe moved into an area with a higher rate of infection. Two possible reasons for this increased rate are suggested. First, that the area was a temporary focus of a higher incidence or concentration of infected flies, owing to local conditions of vegetation and humidity before clearance. Second, that there was a very localized strain of Leishmania which was significantly more virulent than the surrounding normal strain. The graph demonstrates an important difference between males and females of all tribes when the percentage of positive reactions is considered for each age group. The linear increase of the percentage against age suggests strongly an equal incidence of infection at all ages in the case of the female, such that 100% of the women above the age of 40 have been infected. In contrast to this, over 90% of males above the age of 10 have been infected, suggesting that early in their lives the young boys of the village are subjected to a much higher rate of infection than their sisters. The reason for this may be found in the wider activities of the two groups within the social and economic structure of village life. Women spend their whole lives from childhood to old age within the village and the cleared plantation areas in the forest, only very rarely spending nights out in the forest, or travelling to other villages. Thus their environment, and hence the chance of being bitten by infected flies, does not alter. Young boys, however, stay with their mothers and sisters only until they are about 5 years old, and after that they spend an increasing time with their fathers and brothers on hunting and fishing trips. After the age of 14 a young boy will travel long distances away from the village and spend many nights sleeping in the open forest. Thus at an early age his environment is considerably extended, and as this correlates with an early high percentage of positive reactions, we suggest that the forest environment contains the major source of infection. It is concluded that the Indians are living in an area where Leishmania braziliensis is present, and as shown by the detection of antibodies, all the Indians have been infected by the age of 40. Althougn an epidemic of leishmaniasis has been described in one tribe, normal clinical primary lesions were not observed and may be rare, and there is no evidence of secondary involvement.
Summary 74% of the population (540) of 8 tribes of protected Amerindians in the Xing~ National Park of Brazil were skin tested with Montenegro antigen and examined for lesions due to Leishmania braziliensis. No active primary lesions or evidence of secondary mucocutaneous involvement were found. Old scars from primary lesions due to an epidemic of leishmaniasis in the Wanrfi tribe between 1962 and 1964 were examined, and possible causes for this outbreak are discussed. 76% of all males and 47% of all females gave positive Montenegro reactions, and all Indians by the age of 40 were found to have evidence of skin sensitivity to the antigen. The high rate of infection was found to be constant over the whole region studied.
678
LEISHMANIASIS IN CENTRAL BRAZIL
Important differences in the rates of infection in succeeding age groups of males and females appear to correlate with differing activities within the tribe of the two groups, and suggest that the major source of infection is beyond the confines of the village. REFERENCES CARNERI,IVO DE, et al. (1963). Revta Inst. Med. trop., S. Paulo., 5, 271. (1964). Trans. R. Soc. trop. Med. Hyg., 58, 93. CHALMERS,A. H., HARRIS, J. C., SWANTON,R. H. & THORLEY,A. P. (1968). Ibid., 62, 213. LAINSON, R. & SHAW, J. J. (1968). Ibid., 62, 385. &~ (1969). Ibid., 63, 408. PESSOA, S. B. & LOPES, J. A. (1963). Revta Inst. Med. trop. S. Paulo., 5, 170. SHAW, J. J. & LAINSON, R. (1968). Trans. R. Soc, trop. ivied. Hyg., 62, 396.
Vol. 64.
No. 5.
1970.
L E I S H M A N I A S I S IN C E N T R A L BRAZIL: R E S U L T S OF A M O N T E N E G R O SKIN T E S T S U R V E Y A M O N G A M E R I N D I A N S IN T H E X I N G U N A T I O N A L PARK D. L. ASTON AND A. P. THORLEY Members of the Royal Society and Royal Geographical Society Xavantina-Cachimbo Expedition
Introduction T h e clinical disease, mucocutaneous leishmaniasis or espundia, has long been recognized in the central regions of Brazil but little is known of its incidence or epidemiology. Recently LAtNSON and SHAW (1968) and SrIaw and LAmSON (1968) examined the epidemiological situation in the Lower Amazon Basin and have established a mammalian reservoir and insect vectors in that area. Further epidemiological studies are being carried out by these workers in undeveloped areas of Central Brazil (LAmsoN and SHAW 1969). Although brief reports of clinical leishmaniasis in the Upper Xingti region have been made (CARNERIet al. 1963, CARNEaI 1964), nothing is known of the incidence of the disease among indigenous peoples in these areas. This paper describes the results of a Montenegro skin test survey for mucocutaneous leishmaniasis in eight villages of protected Amerindians in the Xingti National Park.
Materials and methods The subjects of the survey were made up of the whole available population of each village, only excitable infants being excluded. Subjects were examined for active primary lesions, old scars and signs of secondary involvement. Characteristically the Indians of the Upper Xingd are naked, and this considerably facilitates a speedy examination. Lesions were scraped with a sterile blade and the sample was smeared on to a glass slide. After being fixed in methanol and stained with Giemsa, it was examined under a microscope for Leishmania braziliensis. Past or present infection by L. braziliensis resulting in antibody formation was detected by use of the Montenegro antigen skin test. Positive reactions to L. braziliemis antigen from other leishmanial species e.g.L, donovani are rare, even with subjects known to be infected with visceral leishrnaniasis in an area where both visceral and mucocutaneous forms are endemic (PESSOAand LOPES 1963). The antigen used in our study was prepared from a culture of L. braziliensis at the Wellcome Parasitological Laboratories, Instituto Evandro Chagas, Belem. The antigen was diluted 1/100 with physiological saline, and a control was also prepared consisting of physiological saline containing 0.5% phenol to allow for the phenolized antigen.
*All correspondence to A. P. Thorley, U.C.H. Medical School, University Street, London, W.C.1. Apart from the generous sponsors of the expedition, the authors would like to thank Professor P. C. C. Garnham for his interest and encouragement, Dr. R. Lainson and Dr. J. J. Shaw for supplying the antigen, Mr. I. Bishop, leader of the expedition, for much practical assistance, and Sr. Orlando Vilas Boas, warden of the Xingti National Park, for hospitality and permission to work in the Indian communities.
LEISHMANIASIS IN CENTRAL BRAZIL
672
Both forearms were cleaned with 70% alcohol, and 0.1 ml. of the antigen and control were injected subcutaneously into the flexor surfaces of the right and left forearms respectively. Gillette gamma-irradiated disposable syringes (1 "0 ml. tuberculin-type) and disposable needles (25G × 8~ in., No. 20) were used and were most satisfactory under difficult conditions. T h e injection sites were ringed with indelible marker, and examined and graded by one of us (A.P.T.) after 48 hours, according to the following scheme: (a) Negative--no induration or erythema. (b) Doubtful--area of induration less than 3 mm. in diameter, with or without erythema. (c) Positive--area of induration more than 3 mm. in diameter, with erythema present. This scheme of gradation follows closely the one used in a previous survey by one of the authors in British Honduras (CI-IALMERSet al., 1968). Local information regarding the individual communities was gathered at the National Park headquarters. Note was made of the age of each Indian examined and skin tested. As Indians do not measure age in years, the ages were gained from anthropologists or other workers in the villages concerned, or assessed as accurately as possible by the authors. This survey was carried out in the dry season during the month of August 1968.
Selection of subjects T h e ideal subjects for study were to be isolated indigenous communities with little regional movement and little or no contact with Europeans. Previous experience in British Honduras (CI-IALMERSet al., 1968) had shown that a village with a population not greater than 200 was the most practical size for a pair o f workers to deal with in one day. ,Ws3*30' ;~(.-
//>'-
4"
~~>-,i, ~" 9
//S . /J
~;.-"
Waura ,fro ,I!
(
,t )
ij
I I
~o
Karnayura(~\~
k
Txik~o-,\'~
}
~/~¢/I{
Posto Leonardo->oe~.~ Yawalap" ' "I? //
? '~
~
/
MAP.
-×\
P
i '/ i
[
/
"~..
0
5,
/'
f
,~
12~00' ~"o Matlpu
L] ° Katapal°s
)~
..... ,,,
t'
)
,s
Kulkuru
""::\l
Indian Villages in southern part of Xingfi National Park.
T h e Indians in the southern part o f the Xing6 National Park have lived in the U p p e r Xing~ Basin (see map) for many generations, with minimal contact with Euro-
D. L. ASTON AND A. P. THORLEY
673
peans. During the last 25 years, in order to prevent their rapid extinction they have been encouraged to move their villages closer to the National Park headquarters at Posto Leonardo Vilas Boas, where basic medical facilities exist. At present they are stringently protected from contact with infectious diseases common in other parts of Brazil, and entry to the Park is restricted to anthropologists and other scientific workers. There are 9 villages of closely related Indians with a total population of 600 in the southern part of the National Park. Individual villages have populations ranging from 40 to 150, and in the dry season all can be reached within one day on foot and by canoe. As they have had some contact with scientific workers, the Indians are helpful and cooperative with visitors who show courtesy and strictly respect their ways and customs. Each village has its own Indian language, but usually a few of the men speak a little Portuguese and this served as a common language of communication. The Upper Xingd Basin lies between 600 and 1,500 feet above sea level, and the region in which the villages are situated is subject to gross annual flooding in the wet season. The vegetation in the area is varied and includes open campos limpos (treeless grasslands), cerrado (savanna woodland) and tall "dry" (semi-deciduous) forest.
Results The authors visited 8 of the 9 Indian villages, and 400 Indians were successfully examined and skin tested, this being 66°~, of the total population.
Evidence of clinical lesions No active primary or secondary lesions were observed. Only one infected lesion was seen which resembled a leishmanial lesion, but microscopic examination of a smear clearly showed a staphylococcal infection. Between late 1962 and the end of 1964 many people in the Waurfi tribe were diagnosed at the National Park headquarters as being infected with primary lesions. This phenomenon had not been reported before in the area, and may be best described as an epidemic (CARNERIet al., 1963). The lesions proved unresponsive to any treatment other than a course of antimonial drugs. The time spent at the Park headquarters while receiving the course of injections was vividly remembered. We examined 71 out of the 97 members of the Waur~ tribe and found 11 males and 5 females with old scars of leishmanial infection.
The Montenegro skin test Control tests were made on 123 Indians, the 71 Waurfi and 6 to 10 members chosen at random from each of the other tribes. The results of the control tests are compared with those of the antigen tests in Table I. Detailed results of the antigen tests for each tribe may be found in Table II. The results for males and females of all tribes are presented graphically in Figure 1, the percentage of positive Montenegro reactions being plotted for each group. The incidence of doubtful reactions and false positive reactions was neglible compared with the incidence of positive reactions (see Table I), and thus will not be considered in the discussion.
674
LEISHMANIASIS IN CENTRAL BRAZIL TABLE I.
Sex
÷
±
M
162
4
46
212
F
88
4
96
188
Total
250
8
142
400
Total
Antigen
%
62.5
2"0
Sex
÷
±
35-5
100 Total
M
5
76
81
F
1
40
42
1
6
116
123
0'8
4-9
Control Total
%
94"3
100
+ = Positive Montenegro reaction 5: = Doubtful reaction - - = Negative reaction
Mates Fema|es
*/a 100 90 I
80
!--
70 I--
BO 50 /-,0 30 20 10 0 0-5 6-10
FIG. 1.
11- 20
21-30
31 -/.0
1.1 -
50
50+ Years
T h e number of positive Montenegro reactions in succeeding age groups expressed as a percentage of the total number of males or females in each group.
D.
L.
ASTON
AND
A. P.
675
THORLEY
TABLE II.
Tribe
Sex
Montenegro Test
Age <5 +
M
6-
5: --
+
10
11 - 2 0 I 2 1 -
5: -- +
1
±
30
3_
3
1
31 - 4 0
41 - 5 0
~ 5: --
+
1
1
M
2 1
1
1
1
4
1 3
F
1
2 4
2
4
Txikao 6
M
2
2
9
F
2
2
4
12
1
9
M
1
1
i
3
1
5
4
3
2
3
2
3
6
4
4
3
1 6
Kamayura F
2
M
J
8
50
2
1
12
1
5
67
10
29
1
1 3
1
1
5
1
5
3
M
2
4
2
3
4
5
3
i
1
12
1
4
7
2
1
2
5
F
10
M
2
4
F
6
2
Matipu M
4
22 22
F
7
29
5
+ = :c = -- =
5
2
t
4] 4 3[ 42
24 15
2 22 28
4 22
1
15
2
2 1
2
38
3
93
21
9
70
2
26
2
13
63
13
1
11
52 66
2
21
11
11
21
36
1
15
7
68
20
23
1
1
3
2
1
4 32
2 17 19
81 88
1
1 1
4
1
3 3
4
3 16 4 3
Totals 9
3
21
2
1 1
3
9
2
Kalapalos
I
4
Kuikuru F
93
1
1
3
1
9
1
6
%+
13
2
1 10 3
-
1
Waura 2
5:
2
2
6
_
4
1
12
F
5
1t4
Mehinaku M
i 3
.
7
Yawalapiti F
±
Totals
50+
6 1
15
2
88
9
17
29
1 10
9
162
4
46
76
4
2
I 88
4
96
47
8
I
Positive M o n t e n e g r o reaction. Doubtful reaction Negative reaction.
Discussion The Indians in the Xingti National Park comprise one of the best groups of protected communities in Brazil and simple clinical surveys can be carried out with little prior experience of working in Indian villages. Although the subjects were most cooperative at the time of receiving the injections, they often remained puzzled and indifferent when we wished to re-examine the arms after 48 hours. On some occasions groups of Indians were missed because they had left the village on a long fishing trip or were involved in religious ceremonies. These are unavoidable inconveniences, and in the circumstances we were fortunate in being able to cover two thirds of the population in such a short time. Be¢ore working with the Indians, we were able to examine and skin test 30 Brazilians on a small fazenda on the road 100 km. south east of the National Park. This squatters' farm, set in cerrado country, had been established some 2 years, and the squatters were poor Brazilians from all over Central Brazil. The results of this pilot survey are not detailed enough to record in the results section as the population is so varied, but it is useful to make reference to them when considering the Indian results. At the single fazenda that was tested, 20 (66%) of the Brazilians had positive reactions, 5 had active primary lesions and 2 others had secondary nasal involvement. We saw only one case of active secondary involvement which may have developed from an active infection contracted in the region. The number of active lesions found on the fazenda contrasts strongly with the fact that no active lesions were found among the Indians. Within the limits of language
676
LEISHMANIASIS I N CENTRAL BRAZIL
and understanding, all the Indians were carefully questioned about primary lesions and secondary involvement and, the Waur~i excepted, there were no reports of such lesions. The Indians were found to be particularly free from scars of any nature, and when questioned, invariably connected them with a specific cut or similar trauma. Although this important difference exists with regard to active lesions, the high percentage of positive reactions among the Indians is very similar to that found among the Brazilians on the fazenda. There is no clear explanation for these findings, but it may be that there are inherent hereditary differences in resistance to clinical leishmaniasis between Indians and Brazilians or that there are strains of Leishmania braziliensis with different virulences in different regions. The high "subclinical" infection rate among the Indians may thus be associated with a small transient lesion, i.e. insect bite, but this passes unnoticed and does not leave any visible scar. Factors which may be of importance are hygiene and nutrition. Under normal conditions the Indian .is healthy and enjoys an abundant diet of fish and manioc, and in some villages game, birds, sugar cane, forest fruits and belries are also eaten. Malnutrition and a low standard of hygiene were common findings at the fazenda. The Indian maintains a high level of body cleanliness, bathing several times a day in the river or lagoon, and rubbing his body surface with a vegetable dye called uruku. This dye is a very effective fly repellent and is used particularly in the wet season when biting flies are in abundance. Thus it may be argued that the Indian is less likely to be bitten by a phlebotomine vector, and i f a primary lesion did occur, secondary bacterial infection would be less likely. It may be assumed that the high percentage of positive reactions correlates with a high biting incidence of infected flies, but no regional differences in infection rates can be discerned. The differences between the percentages of positive reactions for individual villages have been examined and compared, but they are insufficiently large to correlate in any way with subjectively observed differences in local predominating vegetation. It must be noted that the Indians move freely over this whole region and hence are exposed to the bites of insects in all vegetations. The epidemic of leishmaniasis which affected almost a fifth of the Waurfi tribe is particularly interesting and may be an exception to the apparent regional equality in infection rates. The outbreak began a few months after the village had been moved to its present site from an earlier one 4 hours canoe journey up the Rio Batovi. The present site is surrounded on three sides by high dry forest. Prior to the move, it may be assumed that the immunity and ;nfection rates showed the same characteristics as those of any, other comparable tribe in the Park. However, several Indians suffered more than one lesion. CARNERIet al. (1963), in reporting the epidemic up to September 1963 found 9 males and 3 females with active lesions. These authors were particularly impressed by multiple lesions observed on the buttocks of the women, and speculate that these were due to infection by phlebotomines that fly close to the ground, as the women sit outside the huts for long periods each day preparing manioc. I f active infection does occur in this manner, and evidence discussed below suggests that this is unlikely, we would expect to find lesions on other parts of the body close to the ground when sitting or squatting e.g. calves, knees, ankles. By late 1964 the epidemic was over, and when we visited the tribe in 1968 there were no active lesions. We found only 5 females with old scars from primary lesions, and consider that with this small number it is unrealistic to attempt generalizations about modes of infection. 2 had multiple scars on the buttocks or upper thigh, and the others had single or multiple scars distributed randomly, as had the men. Thus it is our opinion that the random siting of old
D. L. ASTON AND A. P. THORLEY
677
lesions as found in both sexes does not appear to indicate infection taking place during any specific social activity. Of the 11 Waur~i males that we found with scars, 7 were children aged between 5 and 10 years, and no infected persons were under 5 or over 40 years. As the older men and women were unaffected after the move, presumably because of their effective resistance, it is assumed that the tribe moved into an area with a higher rate of infection. Two possible reasons for this increased rate are suggested. First, that the area was a temporary focus of a higher incidence or concentration of infected flies, owing to local conditions of vegetation and humidity before clearance. Second, that there was a very localized strain of Leishmania which was significantly more virulent than the surrounding normal strain. The graph demonstrates an important difference between males and females of all tribes when the percentage of positive reactions is considered for each age group. The linear increase of the percentage against age suggests strongly an equal incidence of infection at all ages in the case of the female, such that 100% of the women above the age of 40 have been infected. In contrast to this, over 90% of males above the age of 10 have been infected, suggesting that early in their lives the young boys of the village are subjected to a much higher rate of infection than their sisters. The reason for this may be found in the wider activities of the two groups within the social and economic structure of village life. Women spend their whole lives from childhood to old age within the village and the cleared plantation areas in the forest, only very rarely spending nights out in the forest, or travelling to other villages. Thus their environment, and hence the chance of being bitten by infected flies, does not alter. Young boys, however, stay with their mothers and sisters only until they are about 5 years old, and after that they spend an increasing time with their fathers and brothers on hunting and fishing trips. After the age of 14 a young boy will travel long distances away from the village and spend many nights sleeping in the open forest. Thus at an early age his environment is considerably extended, and as this correlates with an early high percentage of positive reactions, we suggest that the forest environment contains the major source of infection. It is concluded that the Indians are living in an area where Leishmania braziliensis is present, and as shown by the detection of antibodies, all the Indians have been infected by the age of 40. Althougn an epidemic of leishmaniasis has been described in one tribe, normal clinical primary lesions were not observed and may be rare, and there is no evidence of secondary involvement.
Summary 74% of the population (540) of 8 tribes of protected Amerindians in the Xing~ National Park of Brazil were skin tested with Montenegro antigen and examined for lesions due to Leishmania braziliensis. No active primary lesions or evidence of secondary mucocutaneous involvement were found. Old scars from primary lesions due to an epidemic of leishmaniasis in the Wanrfi tribe between 1962 and 1964 were examined, and possible causes for this outbreak are discussed. 76% of all males and 47% of all females gave positive Montenegro reactions, and all Indians by the age of 40 were found to have evidence of skin sensitivity to the antigen. The high rate of infection was found to be constant over the whole region studied.
678
LEISHMANIASIS IN CENTRAL BRAZIL
Important differences in the rates of infection in succeeding age groups of males and females appear to correlate with differing activities within the tribe of the two groups, and suggest that the major source of infection is beyond the confines of the village. REFERENCES CARNERI,IVO DE, et al. (1963). Revta Inst. Med. trop., S. Paulo., 5, 271. (1964). Trans. R. Soc. trop. Med. Hyg., 58, 93. CHALMERS,A. H., HARRIS, J. C., SWANTON,R. H. & THORLEY,A. P. (1968). Ibid., 62, 213. LAINSON, R. & SHAW, J. J. (1968). Ibid., 62, 385. &~ (1969). Ibid., 63, 408. PESSOA, S. B. & LOPES, J. A. (1963). Revta Inst. Med. trop. S. Paulo., 5, 170. SHAW, J. J. & LAINSON, R. (1968). Trans. R. Soc, trop. ivied. Hyg., 62, 396.