Reshedding of Toxoplasma oocysts by chronically infected cats

Abstract

INFECTION with Toxoplasma gondii is prevalent in man and animals. It can be acquired congenially by the foetus from an infected mother¹, but also throughout life by eating under-cooked meat² or by contact with contaminated faeces of cats³. All forms of Toxoplasma lose their infectivity quickly when exposed to the environment, with the exception of oocysts shed in feline faeces. These are remarkably resistant to ordinary environmental influences and can survive in most soil for several months⁴. In the acute phase of infection cats may shed several million oocysts in 1–2 weeks. It has been assumed that after the acute phase, chronically infected cats are safe as pets⁵ since they have acquired immunity and oocysts seldom pass in the faeces^6–8. I report here the reshedding of T. gondii oocysts by chronically infected cats in the absence of exogenous reinfection.