Periparturient immunosuppression in the bitch and its influence on infection with Toxocara canis

Pregnancy and lactation in dogs induced a marked suppression of their immunological responsiveness as judged by in vitro phytomitogen‐ and Toxocara canis antigen‐induced lymphocyte transformation. In addition, the eosinophilia otherwise seen following infection with T. canis was suppressed during the periparturient period. Coincidental with this periparturient immunosuppression was the occurrence of heavy infections with T. canis in the intestine of lactating bitches and the establishment of such infections perhaps may be related to the suppressed immune reactivity observed. These infections in the bitch appeared to be acquired primarily through the ingestion of immature stages of T. canis passed in the faeces of their puppies. The results demonstrate that the lactating bitch can be a major source of contamination of the environment with eggs of T. canis.