Immunological response of the hosts to <i>Toxocara canis</i> (Werner, 1782) infection I. Effect of superinfection on naturally infected puppies

Abstract

Superinfection of naturally infected puppies with large numbers of Toxocara canis eggs induced a self-cure reaction. There was a sharp fall in Toxocara egg output following superinfection in most of the puppies. In most, but not all the puppies, the existing worm burden was eliminated. Eliminated worms were full of fertile eggs, but, in the puppies in which egg production fell sharply without expulsion of the worm burden, egg production by the naturally acquired worms was suppressed only transiently. Antibody production, measured by the complement-fixation test, was directly related to resistance to superinfection but not to self-cure. Acquired resistance reduced the pathogenic effects of superinfection, and prevented development of the parasite beyond the second stage. It is a pleasure to thank Professor P. Seneviratna, University of Ceylon, for his constructive criticisms of the manuscript and the facilities provided. The writer thanks Mr W. G. Senaratne for technical assistance and typing of the manuscript. This work was carried out with a special research grant from the University of Ceylon.