The nematode transmission of Toxoplasma gondii

A cat infected with the nematode, Toxocara cati, and another which was nematode-negative, were both fed with the cystic forms of Toxoplasma gondii. The cat infected with Toxocara cati produced faeces capable of infecting mice with Toxoplasma; the Toxocara-negative cat did not. The Toxocara-negative cat was then infected with this nematode and the positive cat was treated with an anthelmintic to remove the worms. Both cats were again fed with Toxoplasma cysts; once again, the faeces containing the Toxocara cati ova infected mice with Toxoplasma, while those negative for Toxocara did not. These experiments support the idea that Toxoplasma gondii can be transmitted within Toxocara cati ova. Additional support has been provided by the fact that the toxoplasm infections can be filtered from a positive inoculum by using a sieve whose mesh size is small enough to retain the nematode ova. Evidence is given that this transmission mechanism could be responsible for avian infections.