Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

ences in their infectivity to domestic animals and, possibly, to man (Thompson 1986, Thompson et al. 1987). It was suggested that the British sheep strain was infective to man, while the horse strain was probably non-infective, although no definite reason for such differences was given (Thompson and Smyth 1976). In Northern India, the incidence of hydatidosis in man and livestock has been studied, and the buffalo has been found to be the most common intermediate host (Irshadullah et al. 1989a,b). Differences in incidence, fertility and viability rate were also noticed between cysts derived from buffalo liver and lung, but no definite reasons were given for such disparities. Therefore, the presents study was undertaken to investigate similarities and dissimilarities of protoscoleces from buffalo liver and lung cysts by comparing their developmental pattern in experimental puppies. MATERIALS AND METHODS Collection of protoscoleces. Protoscoleces of E. granulosus were isolated from fertile liver and lung hydatid cysts from naturally infected Indian water buffalo, Bubalus bubalis, as described by Smyth and Davies (1974). The mean viability of protoscoleces was determined by the eosin exclusion test and flame cell activity. Experimental design The experimental design as shown in Table 1 was essentially the same as described by Thompson (1977) for the characterization of British horse and sheep strains. There were 10 groups of experimental puppies: five received protoscoleces of lung and the other five were infected with protoscoleces of liver origin. Puppies in each group were 10-12 weeks old and preferably of the same litter. They were kept on a controlled diet. Each experimental animal was starved for 18 h before oral infection with a gelatin capsule containing 0.1 ml packed volume of protoscoleces (approximately 28,000). In order to find out the effect of viability on worm recovery, protoscoleces of different viability (65-96 %) were used. In total, forty-six puppies were infected experimentally and were autopsied at various intervals starting from the 5th day post infection (p.i). Autopsy and worm recovery Infected puppies were starved for 12 h prior to autopsy and euthanatized with an intravenous injection of pentabarbital sodium (Veterinary Drug Co. PLC, U.K.) at a dose of 1 ml/2.5 kg body weight. All measurements and maturation studies were carried out on material fixed in 10 % neutral buffered formalin and stained in acidified Gower's carmine. Maximum care was taken in handling the gravid worms, as formalin has been reported to be ineffective in killing the eggs (Hercus et al. 1962). To study the growth, segmentation and maturation, about 200 worms recovered at different intervals were examined in each case. The maximum number of worms showing a particular stage of development and increase in length with respect to time interval were used for line drawing.