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Acquired resistance to Schistosoma haematobium in the baboon (Papio anubis)
CORRESPONDENCE
151
ACQUIRED RESISTANCE TO SCHISTOSOMA HAEMATOBIUAff IN THE BABOON (PAPIO ANUBIS)
SIR,--Extensive data are now available on the development of acquired resistance to
Schistosoma mansoni in the rhesus monkey (SMITHERS, 1971). The immunological competence of the baboon (Papio anubis) to infections with S. haematobium however has not previously been established. I n a preliminary study 2 baboons (30 and 31), 1 male and 1 female, were given a trickle infection of S. haematobiurn (Nigerian strain) comprising 22 fortnightly exposures of cercariae during a period of 45 weeks, totalling 7,700 per baboon. 100 weeks after the initial exposure these baboons and 2 uninfected control baboons (Nos. 45 and 47), 1 male and I female, were each exposed to 10,000 cercariae of an Egyptian strain of S. haematobium. Baboon 45 died suddenly 13 weeks after infection and a thorough search for adult schistosome worms was made at post-morten examination. Baboon 47 became sick and was killed and perfused 15 weeks after exposure, while baboons 30 and 31 were killed and perfused 14 and 15 weeks respectively after the challenge infections were given. Tissue egg counts were made on all 4 animals using the K O H method of CHEEVER (1968). Weekly urine and faecal egg counts were carried out throughout the periods of the patent infections. T h e average bi-weekly egg production in 24-hour samples of faeces of the 4 baboons is shown in the Figure. Following an initial increase the egg counts of baboon 30, and particularly of baboon 31, fell and remained at a low level throughout their infection. The challenge infections did not alter this pattern. The egg production of control baboons 45 and 47 however rose rapidly following onset of patency and continued to increase until the death of the animals. Following perfusion and dissection the total worm returns were: 461 for baboon 30 (male : female ratio 2 : 1); 3 for baboon 31 (male : female ratio 1 : 2); 1,497 for baboon 45 (male : female ratio 1 : 1); and 2,945 for baboon 47 (male : female ratio 1.5 : 1). The tissue egg counts (Figure, Insert) suggest that baboon 31 acquired resistance to reinfection very early in infection and that eggs laid before this were largely resolved in the tissues. Baboon 30 also apparently developed early resistance to reinfection and to the main challenge infection, but harboured a larger number of adult worms which continued to lay eggs. Baboons 45 and 47 both had expectedly large numbers of eggs in their tissues. JORDAN et al. (1967) found some evidence of resistance to reinfection of Papio anubis
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[ 131CHALLENGER
FINAL TRICKLE
I I~ 47 INFESTER
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txPesuntl
16 2D 2q 29 32 36 40 44 4e 52 50
] 30 CHALLENGER i 45 INFEGTEO
ee ON 60 72 70 Be 14
AGE OF INFECTION- WEEKS
ee 82
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31 • 45 47
no 169 104 195 100 107 108 log 116 111 112 113 114 eADOON45
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11 12
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Average weekly egg production in 24-hour samples of faeces of the four baboons, with insert showing comparative tissue egg counts of different organs.
152
CORRESPONDENCE
with S. haematobium. The results of weekly egg outputs in the present observations show that resistance to reinfection developed relatively early in the course of the 22 weekly exposures of baboon 31. T h e development of a strong acquired resistance in these animals is also clearly demonstrated by the failure of the challenge infections 100 weeks after initial exposure to alter egg output patterns. These data are supported by the adult worm recoveries and tissue egg counts of baboons 30 and 31 compared with those of baboons 45 and 47. These data provide unequivocal confirmation of the development of acquired resistance to S. haematobium in the baboon, epidemiological evidence for which already exists in the case of man (CLARKE, 1966). We are, etc.,
G. WEBBE, C. JAMES, 13 December, 1972
Winches Farm Field Station, London School of Hygiene and Tropical Medicine. REFERENCES
CHEEVER,A. W. (1968). Am. O7. trop. Med. Hyg., 17, 38. CLARKE, V. DE V. (1966). Centr. Aft. J. ivied. Suppl., 12, 1. JORDAN, P., YON LICHTENBERG, F. & GOATLY, K. D. (1967). Bull. Wld Hlth Org., 37, 393. SMITHERS, S. R. (1971). Br. med. Bull., 28, 49. IDENTIFICATIONOF GUINEA-WORMSPECIES SIR,--As MULLER (1971) has pointed out, the specific identification of guinea-worm from non-human hosts is highly controversial. In particular, the relationship of Dracunculus medinensis, the guinea-worm of man which occurs in many parts of Africa and Asia, and D. insignis, which normally parasitizes wild mammals (such as raccoon and mink) in North America, has long been a subject of speculation and confusion (BENBROOK, 1932; CHITWOOD, 1933; CHANDLER, 1942; MEDWAY and SOULSBY, 1966; CRICHTON, 1972; GIBSON and McKIEL, 1972). Recently we have infected a rhesus monkey with D. insignis obtained originally from a wild-caught raccoon and subsequently cycled experimentally in a ranch bred mink. 9 mature female worms were recovered from the wrists and ankles of the rhesus at necropsy after 180 days. The female worms contained eggs, developing embryos and motile larvae. T h e rhesus originated from India, but guinea-worm has never beer~ observed in this host at the Connaught Medical Research Laboratories, Toronto, where this experiment was conducted. This preliminary observation suggests that D. medinensis and D. insignis may be conspecific although different physiological "strains" may exist. Further work is in progress. We thank Dr. M. Walcroft of the Connaught Medical Research Laboratories, Toronto and Dr. R. Ko, University of Hong Kong, for their assistance. We are, etc., M. BEVERLEY-BURTON, Zoology Department, College of Biological Science, University of Guelph, Guelph, Ontario, Canada. V. F. J. CRICHTON, Manitoba Department of Mines, Resources and Environmental Management, 1-139, Tuxedo Boulevard, Box 12, 4 January, 1973 Winnipeg, Manitoba, Canada. REFERENCES BENBROOK, E. A. (1932). O7. Am. vet. med. Ass., 81, 821. CHANDLER,A. C. (1942). Am. O7. trop. Med., 22, 153. CHITWOOD, B. G. (1933). O7. Am. reed. Ass., 100, 802. CRICHTON, V. F. J. (1972). Ph.D. Thesis, University of Guelph. 105 pp. GIBSON, G. G. & McKIEL, D. A. (1972). Can. O7. Zool., 50, 897. MEDWAY,W. & SOULSBY,E. J. L. (1966). o7. Am. med. Ass., 149, 176. MULLER, R. (1971). Dracunculus and Dracunculiasis. Advances in Parasitology, 9, 73, London: Academic Press.
151
ACQUIRED RESISTANCE TO SCHISTOSOMA HAEMATOBIUAff IN THE BABOON (PAPIO ANUBIS)
SIR,--Extensive data are now available on the development of acquired resistance to
Schistosoma mansoni in the rhesus monkey (SMITHERS, 1971). The immunological competence of the baboon (Papio anubis) to infections with S. haematobium however has not previously been established. I n a preliminary study 2 baboons (30 and 31), 1 male and 1 female, were given a trickle infection of S. haematobiurn (Nigerian strain) comprising 22 fortnightly exposures of cercariae during a period of 45 weeks, totalling 7,700 per baboon. 100 weeks after the initial exposure these baboons and 2 uninfected control baboons (Nos. 45 and 47), 1 male and I female, were each exposed to 10,000 cercariae of an Egyptian strain of S. haematobium. Baboon 45 died suddenly 13 weeks after infection and a thorough search for adult schistosome worms was made at post-morten examination. Baboon 47 became sick and was killed and perfused 15 weeks after exposure, while baboons 30 and 31 were killed and perfused 14 and 15 weeks respectively after the challenge infections were given. Tissue egg counts were made on all 4 animals using the K O H method of CHEEVER (1968). Weekly urine and faecal egg counts were carried out throughout the periods of the patent infections. T h e average bi-weekly egg production in 24-hour samples of faeces of the 4 baboons is shown in the Figure. Following an initial increase the egg counts of baboon 30, and particularly of baboon 31, fell and remained at a low level throughout their infection. The challenge infections did not alter this pattern. The egg production of control baboons 45 and 47 however rose rapidly following onset of patency and continued to increase until the death of the animals. Following perfusion and dissection the total worm returns were: 461 for baboon 30 (male : female ratio 2 : 1); 3 for baboon 31 (male : female ratio 1 : 2); 1,497 for baboon 45 (male : female ratio 1 : 1); and 2,945 for baboon 47 (male : female ratio 1.5 : 1). The tissue egg counts (Figure, Insert) suggest that baboon 31 acquired resistance to reinfection very early in infection and that eggs laid before this were largely resolved in the tissues. Baboon 30 also apparently developed early resistance to reinfection and to the main challenge infection, but harboured a larger number of adult worms which continued to lay eggs. Baboons 45 and 47 both had expectedly large numbers of eggs in their tissues. JORDAN et al. (1967) found some evidence of resistance to reinfection of Papio anubis
mno~ lug)
2uoe~ 2uoe[ 19oo ~ INJOg
i
unO? uoo: "
___
!', ~
"'!
u,,
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m
l.:
L
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/
BAeOON ,- o 30
[ 131CHALLENGER
FINAL TRICKLE
I I~ 47 INFESTER
....
II
txPesuntl
16 2D 2q 29 32 36 40 44 4e 52 50
] 30 CHALLENGER i 45 INFEGTEO
ee ON 60 72 70 Be 14
AGE OF INFECTION- WEEKS
ee 82
/
i
'
/
~
31 • 45 47
no 169 104 195 100 107 108 log 116 111 112 113 114 eADOON45
i
NHH47
t
e
g
10
11 12
0
7
8
O 10 E 12
13
Average weekly egg production in 24-hour samples of faeces of the four baboons, with insert showing comparative tissue egg counts of different organs.
152
CORRESPONDENCE
with S. haematobium. The results of weekly egg outputs in the present observations show that resistance to reinfection developed relatively early in the course of the 22 weekly exposures of baboon 31. T h e development of a strong acquired resistance in these animals is also clearly demonstrated by the failure of the challenge infections 100 weeks after initial exposure to alter egg output patterns. These data are supported by the adult worm recoveries and tissue egg counts of baboons 30 and 31 compared with those of baboons 45 and 47. These data provide unequivocal confirmation of the development of acquired resistance to S. haematobium in the baboon, epidemiological evidence for which already exists in the case of man (CLARKE, 1966). We are, etc.,
G. WEBBE, C. JAMES, 13 December, 1972
Winches Farm Field Station, London School of Hygiene and Tropical Medicine. REFERENCES
CHEEVER,A. W. (1968). Am. O7. trop. Med. Hyg., 17, 38. CLARKE, V. DE V. (1966). Centr. Aft. J. ivied. Suppl., 12, 1. JORDAN, P., YON LICHTENBERG, F. & GOATLY, K. D. (1967). Bull. Wld Hlth Org., 37, 393. SMITHERS, S. R. (1971). Br. med. Bull., 28, 49. IDENTIFICATIONOF GUINEA-WORMSPECIES SIR,--As MULLER (1971) has pointed out, the specific identification of guinea-worm from non-human hosts is highly controversial. In particular, the relationship of Dracunculus medinensis, the guinea-worm of man which occurs in many parts of Africa and Asia, and D. insignis, which normally parasitizes wild mammals (such as raccoon and mink) in North America, has long been a subject of speculation and confusion (BENBROOK, 1932; CHITWOOD, 1933; CHANDLER, 1942; MEDWAY and SOULSBY, 1966; CRICHTON, 1972; GIBSON and McKIEL, 1972). Recently we have infected a rhesus monkey with D. insignis obtained originally from a wild-caught raccoon and subsequently cycled experimentally in a ranch bred mink. 9 mature female worms were recovered from the wrists and ankles of the rhesus at necropsy after 180 days. The female worms contained eggs, developing embryos and motile larvae. T h e rhesus originated from India, but guinea-worm has never beer~ observed in this host at the Connaught Medical Research Laboratories, Toronto, where this experiment was conducted. This preliminary observation suggests that D. medinensis and D. insignis may be conspecific although different physiological "strains" may exist. Further work is in progress. We thank Dr. M. Walcroft of the Connaught Medical Research Laboratories, Toronto and Dr. R. Ko, University of Hong Kong, for their assistance. We are, etc., M. BEVERLEY-BURTON, Zoology Department, College of Biological Science, University of Guelph, Guelph, Ontario, Canada. V. F. J. CRICHTON, Manitoba Department of Mines, Resources and Environmental Management, 1-139, Tuxedo Boulevard, Box 12, 4 January, 1973 Winnipeg, Manitoba, Canada. REFERENCES BENBROOK, E. A. (1932). O7. Am. vet. med. Ass., 81, 821. CHANDLER,A. C. (1942). Am. O7. trop. Med., 22, 153. CHITWOOD, B. G. (1933). O7. Am. reed. Ass., 100, 802. CRICHTON, V. F. J. (1972). Ph.D. Thesis, University of Guelph. 105 pp. GIBSON, G. G. & McKIEL, D. A. (1972). Can. O7. Zool., 50, 897. MEDWAY,W. & SOULSBY,E. J. L. (1966). o7. Am. med. Ass., 149, 176. MULLER, R. (1971). Dracunculus and Dracunculiasis. Advances in Parasitology, 9, 73, London: Academic Press.