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The extraparasitic life cycle of Toxocara vitulorum of buffalo in the villages of Sri Lanka is related to observations on buffalo behaviour, experimental studies on the development and persistence of the eggs in soil and in wallows and the presence of eggs in village locations. Calf faeces on soil were rapidly incorporated by insect activity and the eggs developed only slightly slower than in the laboratory. Some infective eggs persisted 3-4 cm deep for 17 months, finally dying during a prolonged hot, dry period. Eggs in a wallow developed intermittently over 16 months as it was flushed with rain water, and eventually died when the wallow dried out. When infected faeces were placed in water, decomposition caused some material to rise to the surface and eggs developed. In villages, eggs are ubiquitous where young calves are kept but survive best where there is moisture and shade around animal pens and wallows. Cows and calves acquire infection from infective eggs in wallow water, soil and pasture, while calves may also be infected from contamination on the udder and teats of the cow. The larvae resulting from this infection do not mature until the infection is passed to the calf through the milk of the cow. At least 72% of village calves have patent infections and current treatment procedures do not reduce the prevalence. The possibility that T. vitulorum is a cause of human visceral larva migrans is discussed.

Treatment of buffalo calves (Bubalus bubalis) at different times after birth demonstrated that transmission of Toxocara vitulorum from the cow to the calf via milk occurs in all calves during the first 2 days after birth, decreases to 53% by 6 days, 10% by 8-9 days and 2% from Day 10 onwards. This may be because the larvae are no longer in the milk or because the calf has become resistant to the establishment of a new infection. The result also emphasizes the importance of mammary transmission of the parasite. Against immature parasites the efficacy of pyrantel and levamisole was 97%; febantel was 100% on one farm, only 35% on another; piperazine 42% and thiabendazole 35%. Santonin was ineffective in four calves. Against mature parasites the efficacy of pyrantel was 100%; febantel was 100% on one farm, only 35% on another; oral levamisole 83%; cutaneous levamisole 73%; oxfendazole 89%; and piperazine 57%. Nevertheless, piperazine reduced the infection to levels which were probably not pathogenic. In general, the efficacy against mature parasites was similar to that against immature parasites. Treatment of 10-16-day-old calves with an anthelmintic, which is effective against immature parasites, is recommended. This procedure greatly reduces contamination of the environment and also precludes the pathogenic effect of a large number of immature or mature parasites.