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Echinococcus granulosus in animals in northern India
Veterinary Parasitology, 28 (1988) 261-266 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
261
Short Communication
Echinococcus granulosus in A n i m a l s in n o r t h e r n India B.P.SINGH' and D.N.DHAR 2"
1Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, U.P. (India) 2Regional Research Centre, Indian Veterinary Research Institute, Rawalpora, Srinagar 190005, Kashmir (India) (Accepted for publication 26 May 1987)
ABSTRACT Singh, B.P. and Dhar, D.N., 1988. Echinococcus granulosus in animals in northern India. Vet. Parasitol., 28: 261-266. The prevalence of larval Echinococcus granulosus in buffaloes, sheep and goats and in adult stray and shepherd dogs was studied in northern India. A total of 48.1% of 754 buffaloes, 30.5% of 1215 sheep and 21.0% of 447 goats were found to be infected with this parasite. The prevalence of infection in buffaloes was higher in older animals than in younger animals. The lungs and livers appeared to be the sites of predilection. A high percentage of cysts from buffaloes (71.1%) were sterile, whereas a high percentage (90.0%) of cysts from sheep and goats were fertile. Shepherd dogs showed a higher prevalence of infection than stray dogs and the latter examined near the vicinity of slaughter houses had a higher prevalence of infection than those examined in other parts of the city. INTRODUCTION
In India, hydatidosis in man and animals results from infection with Echinococcus granulosus (Reddy et al., 1958; Gill and Rao, 1967; Rao, 1968). However, one case of E. multilocularis from man has been reported (Aikat et al., 1978). The overall zoonotic importance of E. granulosus for man and animals in India is high and the present study was therefore undertaken to define the prevalence of larval E. granulosus in sheep, goats and buffaloes and in adult stray and shepherd dogs in northern India. MATERIALS AND METHODS
A total of 754 buffaloes from Bareilly and 3987 sheep and 2133 goats from Bareilly, Delhi, Meerut, Nainital, Almora and Ranikhet were examined be*To whom reprint requests and correspondence should be addressed.
0304-4017/88/$03.50
© 1988 Elsevier Science Publishers B.V.
262 TABLE I Age prevalence of Echinococcusgranulosus in buffaloes Age group (in years)
No. of animals examined
No. and (%) positive
0-2 2-4 4-6 6-8 8-10 910
29 80 160 175 210 100
2(6.9) 15(18.8) 52(32.5) 84(48.0) 138(65.7) 72(72.0)
Total
754
363 ( 48.1)
tween 1978 and 1984. Data on location, size and fertility of cysts for each age group were recorded. Cysts were examined for protoscolices and daughter cysts under a stereoscopic binocular microscope. The viability of protoscolices was determined by the method described by S m y t h and B a r r n e t t (1980). The prevalence of E. granulosus was also determined at necropsy of 440 stray and shepherd dogs killed by the municipal authorities in Bareilly and Meerut. RESULTS
Buffaloes Table I summarizes the results on the prevalence of Echinococcusgranulosus infections in buffaloes in Bareilly. Of 754 buffaloes 48.1% were infected. The prevalence varied from 6.9 to 72.0% and was age related. The principal sites of predilection were the liver and lungs, although occasionally the spleen, heart and kidneys were involved (Table II). Of the cysts found in the liver and lungs 66.0-70.0% had a m a x i m u m diameter of up to 3 cm and only 9.0-13.0% had a d i a m e t e r > 10 cm. Only 19.5% of the 1000 hydatid cysts from the buffaloes examined, were found to be fertile. TABLE II Prevalence of Echinococcusgranulosus in different organs of buffaloes Total animals examined
No. and (%) showing cysts in Liver
Lungs
Spleen
Heart
Kidney
550
188(34.1)
312(56.7)
40(7.3)
2(0.4)
8(1.5)
263 TABLE III Prevalence of Echinococus g r a n u l o s u s Places
Bareilly
Species and (No.) of animals examined
in
No. and (%) positive
sheep and goats Location of cysts Liver
Lungs
Spleen
Kidney
Other organs
Sheep (437) Goats (108
122(27.9) 12 (11.1)
+
+
+
--
_
+
+
+
--
_
Sheep (1000) Goats (1000)
330(33.0) 220(22.0)
+
+
+
+
+
+
+
+
+
+
Sheep (1200) Goats (700)
444(37.0) 168(24.4)
+
+
+
+
+
+
+
+
--
_
Sheep (300) Goats (100)
51(17.0) 13(13.0)
+
+
--
_
_
+
+
+
--
_
Sheep (250) Goats (110)
52(20.8) 11 (10.0)
+
+
+
--
_
÷
÷
--
_
_
Ranikhet Sheep (800) Goats (115)
216(27.0) 23(20.0)
÷
÷
--
_
_
+
+
+
+
+
Delhi Meerut Nanital Almora
Total
Sheep (3987) Goats (2133)
1215(30.5) 447(21.0)
( + ) Indicates presence and ( - ) absence of cysts.
Sheep and Goats Table III summarizes the prevalence of E. granulosus in sheep and goats at various places in northern India. Significantly more sheep (30.5%) were found to be infected with hydatid cysts than goats (21.0%) ( P < 0 . 0 5 ) . The prevalence varied from 17.0 to 37.0% in sheep and from 10.0 to 24.0% in goats. The principal sites of predilection were again the liver and lungs. About 90.0% of the cysts examined from sheep and goats were found fertile.
Dogs Sixteen per cent of stray and shepherd dogs examined were found infected with E. granulosus ( Table IV). Shepherd dogs showed a higher prevalence of infection ( 35.0 %) than stray dogs (11.0-17.0% ). A higher precentage of stray dogs examined near the vicinity of slaughter houses were infected (Table IV ).
264 TABLE IV Prevalence of Echinococcus granulosus in dogs. Type of dogs examined
No. examined
No. and ( % ) positive
Stray 1 Stray 2 Shepherd 3
200 200 40 440
34{17.0) 22(11.0) 14(35.0) 70(15.9)
1From the vicinity of slaughter houses. 2From other parts of the city. 3From the city. DISCUSSION
The present study showed an overall E. granulosus prevalence of 48.1, 30.5 and 21.0% in buffaloes, sheep and goats, respectively, in northern India. The prevalence of E. granulosus in the three intermediate hosts studied was comparable but somewhat higher than previously reported for northern India i.e. 11.1-40.0% in buffaloes (Rao and Mohiyuddin, 1976; Varma, 1978; Prasad and Mandal, 1979; Abraham et al., 1980a; Kosalaraman and Ranganathan, 1980), 35.2-62.3% in cattle (Hegde et al., 1974; Rao and Mohiyuddin, 1976; Abraham et al., 1980a), 2.6-4.6% in sheep (Varma, 1978; Abraham et al., 1980a), 1.1-6.9% in goats (Varma, 1978; Prasad and Mandal, 1979; Abraham et al., 1980a); 7.6% in pigs ( Prasad, 1981 ) and 71.4% in camels ( Lodha et al., 1982 ). The lungs and liver of buffaloes were the favoured sites of predilection, as has been shown to be the case with other studies (Hegde et al., 1974; Islam, 1977; Prasad and Mandal, 1978, 1979; Abraham et al., 1980a; Prasad, 1981; Islam, 1981 ). Our studies with buffaloes also showed an increase in prevalence associated with age. Similar findings have been reported in buffaloes, cattle, sheep, goats and pigs by others (Reddy et al., 1958; Chabanian, 1965; Bandaliev and Avakian, 1971; Islam, 1981, 1982 a,b). A high percentage of hydatid cysts from buffaloes in our study were found to be sterile, thus confirming similar findings reported by Kosalaraman and Ranganathan (1980) for Madras and Islam (1982 a,b) for the adjoining Bangladesh. However, studies from some parts of the country have shown a level of high fertility of hydatid cysts from buffaloes (Gill and Rao, 1967; Prasad and Mandal, 1979; Prasad, 1981 ). The precise reasons for the variation in the fertility levels of buffalo hydatid cysts seen by different workers are not known. Perhaps age of the intermediate host at the time of the infection and strain of E. granulosus causing the infection were responsible for the differences observed. Strain differences exist in E. granulosus (Smyth and Smyth, 1964) and intermediate hosts infected at a young age have been reported to develop
265
fertile cysts as against older animals which were shown to develop sterile cysts (Soulsby, 1965). In contrast to the low fertility of buffalo hydatid cysts observed in our study, 90.0% of cysts from sheep and goats were found to be fertile. A high level of fertility, varying from 71.9 to 93.3% of hydatid cysts from sheep and goats has been reported by others (Prasad and Mandal, 1978; Abraham et al., 1980 b ). In our study, 16% of the dogs examined were infected with E. granulosus, as against a prevalence of 33.3% in dogs from the Kurnool district of Andhara Pradesh as reported by Reddy et al. (1958) (which is probably the only other comparable report available for India).
REFERENCES Abraham, J., Madhavan Pillai, K. and Iyer, R.P., 1980a. Fertility rate in hydatid cysts in domestic animals. (Kerala J. Vet. Sci., 11: 155-158. Abraham, J., Madhavan Pillai, K. and Iyer, R.P., 1980b. Incidence of hydatidosis in animals slaughtered in Kerala. Kerala J. Vet. Sci., 11: 247-251. Aikat, B.K., Bhusnurmath, S.R., Cadersa, M., Chhauttani, P.N. and Mitra, S.K., 1978. Echinococcus multilocularis infection in India: First case report proved at autopsy. Trans. Roy. Soc. Trop Med. Hyg., 72: 619-621. Bandaliev, A.L. and Avakian, D.M., 1971. Echinococcosis and alveococcosis in animals. Nat. Sc. Conf. Helminth. Dis. 22: 30-34. Chabanian, A.G., 1965. Epizootiological aspects of echinococcosis in Armenia, USSR. Byull. Vses. Gelm. im. Skryabin., 2: 260-263. Gill, H.S. and Rao, B.V., 1967. On the biology and morphology ofEchinococcus granulosus (Batsch, 1786) of buffalo-dog origin. Parasitology, 57: 695-704. Hegde, K.S., Abdul Rahman, S., Rajasekarian, G.R. and Jagannath, M.S., 1974. A study of the incidence of hydatid disease in animlas and human beings in Bangalore city. Mysore J. Agric. Sci., 8: 418-422. Islam, A.W.M.S., 1981. Echinococcosis in goats. Indian Vet. J., 58: 999-1000. Islam, A.W.M.S., 1982a. Hydatidosis in buffaloes in Bangladesh. Rev. Sci. Tech. Off. Int. Epiz., 1: 435-441. Islam, A.W.M.S., 1982b. The prevalence of hydatid disease in buffaloes in Bangladesh. Ann. Trop. Med. Parasitol., 76: 623-626. Islam, N., 1977. Hydatid disease in Bangladesh. Lancet, 2: (8027) :33. Kosalaraman, V.R. and Ranganathan, M., 1980. A survey of disease condition of lungs of buffaloes. Cheiron, 9: 281-284. Lodha, K.R., Raisinghani, P.M. and Vyas, U.K., 1982. Note on echinococcosis in Indian camel (Camelus dromerdarius). Indian J. Anita. Sci., 52: 613-616. Prasad, B.N., 1981. Prevalence of hydatidosis amongst pigs of Bihar and its public health importance. Haryana Vet., 20: 24-28. Prasad, B.N. and Mandal, L.N., 1978. Hydatidosis in goats in India. Philipp. J. Vet. Med., 17: 191-196. Prasad, B.N. and Mandal, L.N., 1979. Incidence of hydatid cysts in buffaloes in Bihar, India. Kerala J. Vet. Sci., 10: 220-225. Rao, B.V., 1968. Certain biological and epidemiological considerations of hydatidosis in India with special reference to buffalo material. Bull. Ind. Soc. Mal. Com. Dis., 5: 257-261.
266 Rao, D.G. and Mohiyuddin, S., 1976,. Incidence of hydatid cyst in bovines and histopathological changes of pulmonary tissue in hydatidosis. Indian J. Anim. Sci., 44: 437-440. Reddy, C.R.R.M., Morasiah, I.L., Parvathi, G. and Somasundara Rao, M., 1958. Epidemiology of hydatid disease in Kurnool. Indian J. Med. Res., 56: 1205-1220. Smyth, J.D. and Barrnett, N.J., 1980. Procedures for testing the viability of human hydatid cysts following surgical removal, especially after chemotherapy. Trans. Roy. Soc. Trop. Med. Hyg., 74: 649-652. Smyth, J.D. and Smyth, M.M., 1964. Natural and experimental hosts of Echinococcus granulosus. and E. multilocularis, with comments on the genetics of speciation in the genus Echinococcus. Parasitology, 54: 493-514. Soulsby, E.J.L., 1965. Text Book of Veterinary Clinical Parasitology, Volume I. Helminths. Blackwell Scientific Publications, Oxford, p. 1044. Varma, T.K., 1978. Hydatid disease in food animals and man. Livestock Adviser, 3: 17-19.
261
Short Communication
Echinococcus granulosus in A n i m a l s in n o r t h e r n India B.P.SINGH' and D.N.DHAR 2"
1Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, U.P. (India) 2Regional Research Centre, Indian Veterinary Research Institute, Rawalpora, Srinagar 190005, Kashmir (India) (Accepted for publication 26 May 1987)
ABSTRACT Singh, B.P. and Dhar, D.N., 1988. Echinococcus granulosus in animals in northern India. Vet. Parasitol., 28: 261-266. The prevalence of larval Echinococcus granulosus in buffaloes, sheep and goats and in adult stray and shepherd dogs was studied in northern India. A total of 48.1% of 754 buffaloes, 30.5% of 1215 sheep and 21.0% of 447 goats were found to be infected with this parasite. The prevalence of infection in buffaloes was higher in older animals than in younger animals. The lungs and livers appeared to be the sites of predilection. A high percentage of cysts from buffaloes (71.1%) were sterile, whereas a high percentage (90.0%) of cysts from sheep and goats were fertile. Shepherd dogs showed a higher prevalence of infection than stray dogs and the latter examined near the vicinity of slaughter houses had a higher prevalence of infection than those examined in other parts of the city. INTRODUCTION
In India, hydatidosis in man and animals results from infection with Echinococcus granulosus (Reddy et al., 1958; Gill and Rao, 1967; Rao, 1968). However, one case of E. multilocularis from man has been reported (Aikat et al., 1978). The overall zoonotic importance of E. granulosus for man and animals in India is high and the present study was therefore undertaken to define the prevalence of larval E. granulosus in sheep, goats and buffaloes and in adult stray and shepherd dogs in northern India. MATERIALS AND METHODS
A total of 754 buffaloes from Bareilly and 3987 sheep and 2133 goats from Bareilly, Delhi, Meerut, Nainital, Almora and Ranikhet were examined be*To whom reprint requests and correspondence should be addressed.
0304-4017/88/$03.50
© 1988 Elsevier Science Publishers B.V.
262 TABLE I Age prevalence of Echinococcusgranulosus in buffaloes Age group (in years)
No. of animals examined
No. and (%) positive
0-2 2-4 4-6 6-8 8-10 910
29 80 160 175 210 100
2(6.9) 15(18.8) 52(32.5) 84(48.0) 138(65.7) 72(72.0)
Total
754
363 ( 48.1)
tween 1978 and 1984. Data on location, size and fertility of cysts for each age group were recorded. Cysts were examined for protoscolices and daughter cysts under a stereoscopic binocular microscope. The viability of protoscolices was determined by the method described by S m y t h and B a r r n e t t (1980). The prevalence of E. granulosus was also determined at necropsy of 440 stray and shepherd dogs killed by the municipal authorities in Bareilly and Meerut. RESULTS
Buffaloes Table I summarizes the results on the prevalence of Echinococcusgranulosus infections in buffaloes in Bareilly. Of 754 buffaloes 48.1% were infected. The prevalence varied from 6.9 to 72.0% and was age related. The principal sites of predilection were the liver and lungs, although occasionally the spleen, heart and kidneys were involved (Table II). Of the cysts found in the liver and lungs 66.0-70.0% had a m a x i m u m diameter of up to 3 cm and only 9.0-13.0% had a d i a m e t e r > 10 cm. Only 19.5% of the 1000 hydatid cysts from the buffaloes examined, were found to be fertile. TABLE II Prevalence of Echinococcusgranulosus in different organs of buffaloes Total animals examined
No. and (%) showing cysts in Liver
Lungs
Spleen
Heart
Kidney
550
188(34.1)
312(56.7)
40(7.3)
2(0.4)
8(1.5)
263 TABLE III Prevalence of Echinococus g r a n u l o s u s Places
Bareilly
Species and (No.) of animals examined
in
No. and (%) positive
sheep and goats Location of cysts Liver
Lungs
Spleen
Kidney
Other organs
Sheep (437) Goats (108
122(27.9) 12 (11.1)
+
+
+
--
_
+
+
+
--
_
Sheep (1000) Goats (1000)
330(33.0) 220(22.0)
+
+
+
+
+
+
+
+
+
+
Sheep (1200) Goats (700)
444(37.0) 168(24.4)
+
+
+
+
+
+
+
+
--
_
Sheep (300) Goats (100)
51(17.0) 13(13.0)
+
+
--
_
_
+
+
+
--
_
Sheep (250) Goats (110)
52(20.8) 11 (10.0)
+
+
+
--
_
÷
÷
--
_
_
Ranikhet Sheep (800) Goats (115)
216(27.0) 23(20.0)
÷
÷
--
_
_
+
+
+
+
+
Delhi Meerut Nanital Almora
Total
Sheep (3987) Goats (2133)
1215(30.5) 447(21.0)
( + ) Indicates presence and ( - ) absence of cysts.
Sheep and Goats Table III summarizes the prevalence of E. granulosus in sheep and goats at various places in northern India. Significantly more sheep (30.5%) were found to be infected with hydatid cysts than goats (21.0%) ( P < 0 . 0 5 ) . The prevalence varied from 17.0 to 37.0% in sheep and from 10.0 to 24.0% in goats. The principal sites of predilection were again the liver and lungs. About 90.0% of the cysts examined from sheep and goats were found fertile.
Dogs Sixteen per cent of stray and shepherd dogs examined were found infected with E. granulosus ( Table IV). Shepherd dogs showed a higher prevalence of infection ( 35.0 %) than stray dogs (11.0-17.0% ). A higher precentage of stray dogs examined near the vicinity of slaughter houses were infected (Table IV ).
264 TABLE IV Prevalence of Echinococcus granulosus in dogs. Type of dogs examined
No. examined
No. and ( % ) positive
Stray 1 Stray 2 Shepherd 3
200 200 40 440
34{17.0) 22(11.0) 14(35.0) 70(15.9)
1From the vicinity of slaughter houses. 2From other parts of the city. 3From the city. DISCUSSION
The present study showed an overall E. granulosus prevalence of 48.1, 30.5 and 21.0% in buffaloes, sheep and goats, respectively, in northern India. The prevalence of E. granulosus in the three intermediate hosts studied was comparable but somewhat higher than previously reported for northern India i.e. 11.1-40.0% in buffaloes (Rao and Mohiyuddin, 1976; Varma, 1978; Prasad and Mandal, 1979; Abraham et al., 1980a; Kosalaraman and Ranganathan, 1980), 35.2-62.3% in cattle (Hegde et al., 1974; Rao and Mohiyuddin, 1976; Abraham et al., 1980a), 2.6-4.6% in sheep (Varma, 1978; Abraham et al., 1980a), 1.1-6.9% in goats (Varma, 1978; Prasad and Mandal, 1979; Abraham et al., 1980a); 7.6% in pigs ( Prasad, 1981 ) and 71.4% in camels ( Lodha et al., 1982 ). The lungs and liver of buffaloes were the favoured sites of predilection, as has been shown to be the case with other studies (Hegde et al., 1974; Islam, 1977; Prasad and Mandal, 1978, 1979; Abraham et al., 1980a; Prasad, 1981; Islam, 1981 ). Our studies with buffaloes also showed an increase in prevalence associated with age. Similar findings have been reported in buffaloes, cattle, sheep, goats and pigs by others (Reddy et al., 1958; Chabanian, 1965; Bandaliev and Avakian, 1971; Islam, 1981, 1982 a,b). A high percentage of hydatid cysts from buffaloes in our study were found to be sterile, thus confirming similar findings reported by Kosalaraman and Ranganathan (1980) for Madras and Islam (1982 a,b) for the adjoining Bangladesh. However, studies from some parts of the country have shown a level of high fertility of hydatid cysts from buffaloes (Gill and Rao, 1967; Prasad and Mandal, 1979; Prasad, 1981 ). The precise reasons for the variation in the fertility levels of buffalo hydatid cysts seen by different workers are not known. Perhaps age of the intermediate host at the time of the infection and strain of E. granulosus causing the infection were responsible for the differences observed. Strain differences exist in E. granulosus (Smyth and Smyth, 1964) and intermediate hosts infected at a young age have been reported to develop
265
fertile cysts as against older animals which were shown to develop sterile cysts (Soulsby, 1965). In contrast to the low fertility of buffalo hydatid cysts observed in our study, 90.0% of cysts from sheep and goats were found to be fertile. A high level of fertility, varying from 71.9 to 93.3% of hydatid cysts from sheep and goats has been reported by others (Prasad and Mandal, 1978; Abraham et al., 1980 b ). In our study, 16% of the dogs examined were infected with E. granulosus, as against a prevalence of 33.3% in dogs from the Kurnool district of Andhara Pradesh as reported by Reddy et al. (1958) (which is probably the only other comparable report available for India).
REFERENCES Abraham, J., Madhavan Pillai, K. and Iyer, R.P., 1980a. Fertility rate in hydatid cysts in domestic animals. (Kerala J. Vet. Sci., 11: 155-158. Abraham, J., Madhavan Pillai, K. and Iyer, R.P., 1980b. Incidence of hydatidosis in animals slaughtered in Kerala. Kerala J. Vet. Sci., 11: 247-251. Aikat, B.K., Bhusnurmath, S.R., Cadersa, M., Chhauttani, P.N. and Mitra, S.K., 1978. Echinococcus multilocularis infection in India: First case report proved at autopsy. Trans. Roy. Soc. Trop Med. Hyg., 72: 619-621. Bandaliev, A.L. and Avakian, D.M., 1971. Echinococcosis and alveococcosis in animals. Nat. Sc. Conf. Helminth. Dis. 22: 30-34. Chabanian, A.G., 1965. Epizootiological aspects of echinococcosis in Armenia, USSR. Byull. Vses. Gelm. im. Skryabin., 2: 260-263. Gill, H.S. and Rao, B.V., 1967. On the biology and morphology ofEchinococcus granulosus (Batsch, 1786) of buffalo-dog origin. Parasitology, 57: 695-704. Hegde, K.S., Abdul Rahman, S., Rajasekarian, G.R. and Jagannath, M.S., 1974. A study of the incidence of hydatid disease in animlas and human beings in Bangalore city. Mysore J. Agric. Sci., 8: 418-422. Islam, A.W.M.S., 1981. Echinococcosis in goats. Indian Vet. J., 58: 999-1000. Islam, A.W.M.S., 1982a. Hydatidosis in buffaloes in Bangladesh. Rev. Sci. Tech. Off. Int. Epiz., 1: 435-441. Islam, A.W.M.S., 1982b. The prevalence of hydatid disease in buffaloes in Bangladesh. Ann. Trop. Med. Parasitol., 76: 623-626. Islam, N., 1977. Hydatid disease in Bangladesh. Lancet, 2: (8027) :33. Kosalaraman, V.R. and Ranganathan, M., 1980. A survey of disease condition of lungs of buffaloes. Cheiron, 9: 281-284. Lodha, K.R., Raisinghani, P.M. and Vyas, U.K., 1982. Note on echinococcosis in Indian camel (Camelus dromerdarius). Indian J. Anita. Sci., 52: 613-616. Prasad, B.N., 1981. Prevalence of hydatidosis amongst pigs of Bihar and its public health importance. Haryana Vet., 20: 24-28. Prasad, B.N. and Mandal, L.N., 1978. Hydatidosis in goats in India. Philipp. J. Vet. Med., 17: 191-196. Prasad, B.N. and Mandal, L.N., 1979. Incidence of hydatid cysts in buffaloes in Bihar, India. Kerala J. Vet. Sci., 10: 220-225. Rao, B.V., 1968. Certain biological and epidemiological considerations of hydatidosis in India with special reference to buffalo material. Bull. Ind. Soc. Mal. Com. Dis., 5: 257-261.
266 Rao, D.G. and Mohiyuddin, S., 1976,. Incidence of hydatid cyst in bovines and histopathological changes of pulmonary tissue in hydatidosis. Indian J. Anim. Sci., 44: 437-440. Reddy, C.R.R.M., Morasiah, I.L., Parvathi, G. and Somasundara Rao, M., 1958. Epidemiology of hydatid disease in Kurnool. Indian J. Med. Res., 56: 1205-1220. Smyth, J.D. and Barrnett, N.J., 1980. Procedures for testing the viability of human hydatid cysts following surgical removal, especially after chemotherapy. Trans. Roy. Soc. Trop. Med. Hyg., 74: 649-652. Smyth, J.D. and Smyth, M.M., 1964. Natural and experimental hosts of Echinococcus granulosus. and E. multilocularis, with comments on the genetics of speciation in the genus Echinococcus. Parasitology, 54: 493-514. Soulsby, E.J.L., 1965. Text Book of Veterinary Clinical Parasitology, Volume I. Helminths. Blackwell Scientific Publications, Oxford, p. 1044. Varma, T.K., 1978. Hydatid disease in food animals and man. Livestock Adviser, 3: 17-19.