Is litter tray a risk for mum-to-be?

I have a five-year-old female cat. As I am pregnant, I am advised not to clean my cat's litter tray because of the risk of toxoplasmosis. Is this true?

- DR DAVID GRANT

Toxoplasma gondii is a single cell protozoon parasite that causes toxoplasmosis. The parasite can infect all warm-blooded animals, but it is only in the cat (definitive host) where sexual reproduction is possible.

Oocysts are then formed, which are excreted in the faeces. These become infectious in one to five days on exposure to air and moisture.