The Seasonal Fluctuation in the Number of Eggs of Nematodirus sp. in Feces

Abstract

In studies on the biology of Trichostrongylidae during the last few years, we have been able to observe day by day the degree of invasion of certain host animals, especially of roes, Gazella subgutturosa, stags, etc., in the Zoopark. Our findings are given in this paper. We and our collaborators find that those animals which supplied us with abundant material in the form of trichostrongylid eggs during the summer and autumn months, showed a considerable reduction in the number of eggs in late winter and early spring. This reduction led us to suppose that a considerable decrease in the number of worms takes place in the intestine of the host in winter, as our investigators (M. M. Zawadowsky and collaborators) have shown, that the invasion of animals, even of those that remain in the open on glades infected by trichostrongylids during the whole winter, stops almost completely because of the low temperature. We have deemed it necessary to subject the regularity of decline in infestation as qualitatively established, to a more precise quantitative verification. Nematodirus seemed to be a suitable object for this study, owing to the size and the specificity of its eggs which can be easily distinguished from the eggs of other Trichostrongylidae. These observations should be of some practical interest in animal husbandry, for they afford evidence as to the prophylactic role of the winter period, give indirect indications as to the longevity of Nematodirus1 in the intestine of the host, and show also the specific value of prophylactic measures. One of the Zoopark llamas, gravely infected with Nematodirus, served as an object of observation during the years I929, I930 and 1931, thus providing observations on the number of Nematodirus eggs in the feces of a llama during almost two whole years.