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.

At this stage they are known as sporozoites, which can survive in soil and remain infectious for months. If ingested by another animal, including humans (intermediate hosts), the sporozoites penetrate the intestine, multiplying and migrating throughout the body.

They may end up in any tissue, surrounding themselves in cysts, especially in the brain, eyes, liver and muscle. Damage caused in these tissues can cause a variety of signs.