Trichinella spiralis in India. II. Characteristics of a strain isolated from a civet cat in Calcutta.

Abstract

Abstract 2 strains of Trichinella , one isolated from a civet cat in Calcutta, and a second isolated from a pig raised at Joliette, Quebec, were passaged through rats for 3 generations. Comparison of the strains in their 4th generation in albino rats showed that the strains differed, the Indian being the less well adapted to rats. It produced fewer trichinellae per g. of muscle, fewer adults, and these were unusually small. Males were scarce, which resulted in a markedly disparate sex ratio. The reproductive success, i.e. the number of larvae recovered divided by the number of adult females, was less in the Indian strain than in the Canadian. In cats and inbred rats, it was shown that, of the differences recorded above, only the small size of the Indian strain might distinguish it from other geographical races of Trichinella . The first comparative experiment was repeated, but with the Indian strain in its 9th generation in rats, and the Canadian in its 5th. The Indian strain had become more highly adapted to rats by serial passage. The differences which originally served to distinguish it clearly from the Canadian strain had been largely eliminated. It was concluded that the strain recovered from a civet cat in Calcutta could not be distinguished from the classical Trichinella , by the criteria we used, and, hence, it probably did not represent a peculiar Indian form. It is suggested that the natural range of the classical Trichinella of North Temperate areas may extend into India, or that it may have been introduced by human activities. This suggestion does not exclude the possibility that a peculiar autochthonous form of Trichinella may occur in the larger wild mammals of India.