Toxoplasmosis in coypu.

Serological studies indicate that toxoplasmosis is a common infection in coypus now established in Norfolk. A strain of Toxoplasma gondii was isolated from an animal which had shown a high titre to the dye test for toxoplasma antibodies. This was similar to the many tissue cyst producing strains which are of low virulence for most of the small laboratory animals. Congenital toxoplasmosis was proved in a litter born to one of the coypus during captivity. Superinfection occurred when animals, previously infected with a strain of low virulence, were given a challenge of the highly virulent RH strain, but coypus are so resistant that the latter strain caused no apparent illness even in previously uninfected seronegative animals. Antibodies developed to titres of 1:100,000 or more and, at lower levels, persisted for at least a year.