Toxoplasmosis immunity?

Question

I hope everyone has managed to convince the pregnant lady that she will be fine and she takes her cat back into her home however I just wanted to inform you all that you should not presume you are immune just because you have cats, handle raw meat or garden.

After 12 years of being a veterinary nurse handling some of the most dirty cats you can imagine and also being a gardener I presumed I would be immune but while I was having a blood test for something else decided to get tested for toxoplasmosis immunity at the same time as I was planning my second pregnancy. I discovered I was NOT immune. If you follow basic hygiene rules like washing your hands before eating, after gardening, after handling cats, litter trays etc then it is unlikely you will be immune.

For the person in a previous question who said 90% of us are immune - if a veterinary nurse is not immune then I very much doubt that 90% of the population are.

Four years down the line I got tested again and guess what - Still not immune. I guess I wash my hands properly.

With cat poop it has to sit around for 24hrs before it becomes a problem. If litter trays are cleaned out regularly with poop removed as soon as it 'appears' then it is quite safe to handle. This is why gardeners are more likely to get it as cats use their gardens for a toilet and they don't realise until they have been digging around in it and as the poo is usually older the toxoplasmosis has become viable.

Answer 1

Once infected cats excrete oocysts that each contain eight sporozoites (the infective stage for humans). These can survive for months and the cat can excrete millions at a time in its faeces. Once infected (by swallowing these oocysts) humans often exhibit transient flu like symptoms caused by the Tachyzoite parasitic stage. The infection peaks at 10-20days and the immune system brings it under control. As this stage ends another begins with an asymptomatic chronic stage where a different form of the parasite, Bradyzoites encyst in your brain and muscle tissue. The body has a very weak immue responce to this stage but a very powerful one against the Tachyzoite stage. Therefore when a change of conditions in the body such as the pH triggers these Bradyzoites to change back into Tachyzoites the immune system soon mops them up and prevents them dividing.

For the actual figures i think you will find in the UK prevelance in the human population is around 20% and around 1/2000 births are affected. In other places such as france it is a far more important issue as 80% of the population are infected and 3/1000 births are affected.

An infection during pregnancy may result from transfer of the Tachyzoite stage to the baby from the mother. The severity of damage relates to how long the baby is exposed to the parasite. Transmission in early gestation causes more severe foetal pathology.
Once you have this parasite the body developes a defence against the Tachyzoite stage and although you will probably have the Bradyzoite form in your long lived body tissues for the rest of your life this stage doesn't affect your developing baby.

Just out of interest recent studies have shown individuals that have the toxoplamosis parasite are more likely to take risks. The reason behind this is that the Bradyzoite stage wants you to be eaten by a cat. Studies with mice have shown that mice infected with Toxoplasmosis are no longer afraid of cats and walk towards them rather than away, Its not been proven but it is interesting :-)

Answer 2

in truth unless your cats go out and happen to encouter a mouse at the time the mouse is shedding the parasite..its not likey you will be affected.. although I have heard there is a good chance most of us with cts have already been exposed...
of course you cannot get it simply from handling raw meat.. you actually have to put your hand in your mouth when the parasite is on your hands and so forth (same with handling cat poop)

I am always saddened though when doctors are too quick to tell pregnant women to get rid of their cats....

Answer 3

The CDC fact sheet is available for anyone on the internet, maybe we should bookmark it for all the toxo questions.

http://www.cdc.gov/NCIDOD/dpd/parasites/toxoplasmosis/factsht_toxoplasmosis.htm

Answer 4

Thanks that was very informative!