Whales, Dolphins and Porpoises Down the Toilet?

A group of workers at Swansea and Glamorgan Universities as well as the Public Health Laboratories at Singleton Hospital have made the Guardian (http://www.guardian.co.uk/environment/2007/aug/30/3 ) via the Veterinary Record (Forman, West, Powell, Francis and Guy [2007] Toxoplasma in cetaceans around the British Isles. 161: 279) with an intriguing, yet speculative, hypothesis linking the parasite Toxoplasma gondii to deaths in whales, porpoises and dolphins around our coasts. They basically discovered a surprisingly high rate of seropositive responses to this protozoan parasite in washed up carcasses of marine cetaceans. Toxoplasma is of great public health concern because it can cause foetal abnormalities (including blindness) when pregnant women are exposed to the parasite for the first time as well as problems in immunocompromised individuals (with HIV or following transplants). The domestic cat is routinely 'fingered' as the 'domestic' transmission agent to humans via its feces. The protozoan is an interesting parasite as it has been shown to make infected rats fearless of cats (facilitating its passage to the predator). It may also have profound behavioural effects in other species. The paper noted accounts from California linking Sea otter deaths to human disposal of cat litter (bags of cat litter on sale there reportedly now carry advice about safe disposal). In a quick survey, the group found that one in eight of responding Swansea University cat owners 'admitted' to flushing cat litter down the toilet, raising the possibility that this activity may help the parasite 'jump' to cetaceans. There are, of course, still many unanswered questions. Are Swansea University cat lovers atypical in their cat litter disposal practices? One might also ask whether sewage treatment would negate this problem. If the parasite is passed in cat litter, it is an unexpected further environmental problem associated with pet keeping. Another possibility is that some other infected bird or mammal is implicated. The study essentially confirms that Toxoplasma is found in a very wide range of UK mammalian species. Perhaps we shouldn't be obsessed by cats?