Toxoplasmosis a Zoonotic Disease

Toxoplasma gondii is a parasite which lives inside the cells of mammals. Cats are the definitive host of this parasite but other animals including humans can act as intermediate hosts. Toxoplasmosis is the disease caused by this parasite and is particularly important because it can be transmitted to humans with potentially devastating effects in pregnant women.

Cats contract toxoplasmosis by ingesting raw meat, bones or viscera fed to them by their owners or from prey animals, drinking unpasteurized milk, or eating insects such as flies or cockroaches, all of which may carry toxoplasmosis. They could also get it from dirty litter trays or contact with cat faeces in the garden. Cats are most likely to contract toxoplasmosis for the first time while they are young, often from prey animals they catch while out hunting. They often show few signs of disease and the infection may go unnoticed. However, it is at this time of initial infection that they are most likely to shed toxoplasma oocysts in their faeces and transmit the disease to other animals or to humans.

Clinical disease due to toxoplasmosis is uncommon in felines and most infected individuals will not have noticeable signs. However a few unfortunate individuals will become clinically ill at the time of initial infection or later on due to the disease being reactivated when the cat's immune system is compromised because of some other problem such as FeLV, FIV, FIP or treatment with corticosteroids.

Cats which have clinical toxoplasmosis may show non-specific signs of illness such as lethargy, lack of appetite, weight loss, fever, vomiting and diarrhoea. Often there may be signs of ocular problems such as a discharge from the eyes. Respiratory and neurological signs are also possible. When a cat contracts the disease during pregnancy the kittens are at risk. If kittens contract the disease from their mother before they are born the symptoms tend to be severe, with many kittens being stillborn or dying shortly after birth. If the disease is contracted postnatally in young kittens the most common signs are vomiting and diarrhoea as well as respiratory problems. In immunocompromised patients there can often be a reactivation of the disease so that animals become clinically ill and shed oocysts once more. In these immunocompromised cats the disease can be quite severe, so cats with FIV, FeLV and FIP or those on corticosteroids are at risk. Generally healthy cats will not shed oocysts after the initial infection.

Treatment is possible for cats with clinical toxoplasmosis. Clindamycin may be used at a dose rate of 25-50 mg/kg per day divided between two doses and this treatment should be continued for two weeks after the signs of disease have abated. Ocular problems such as uveitis associated with toxoplasmosis may need to be treated concurrently, 1% prednisone drops are often used for this. The clinical signs of disease should begin to resolve in a few days with treatment but don't stop the medication until 2 weeks after your cat seems to be cured. The prognosis for feline patients with clinical toxoplasmosis is guarded because response to therapy is unpredictable, those patients most at risk are young kittens and severely immunocompromised cats.

People may contract Toxoplasmosis in a number of ways. These include eating raw or undercooked meat, eating unwashed salads, vegetables or fruit which has been contaminated with Toxoplasma (usually from cat faeces), contact with cat faeces in the home or garden and contact with ewes at lambing time. In people Toxoplasma generally only causes mild symptoms possibly involving a rise in temperature, swollen glands and general flu-like signs. The problem can last 14 days or so and most people do not realize that they had Toxoplasmosis. In fact about 50% of people will prove to have been infected at one time or another if blood samples are checked for this disease.

Problems may arise from this disease if people are immunocompromised. Perhaps due to AIDS, cancer or chemotherapy. In these people the immune system is not able to fight the disease as it should with the result that the disease is potentially much more serious than in normal people.

The most well known at risk group are pregnant women, in whom the disease can be passed to their unborn child with resulting blindness, brain damage or epilepsy. The disease is most likely to cause a problem if contracted in the first or second trimester of pregnancy. Luckily the risk of contracting the disease is quite small and only one in 10 000 babies is born with severe congenital toxoplasmosis.

If you are pregnant it is sensible to take a few simple precautions to avoid contracting toxoplasmosis, these are:

1: Take care that all fruit and vegetables are well washed. Particular care should be taken with root vegetables or any other food showing evidence of heavy soiling. Wear gloves when washing such vegetables and clean work surfaces and sinks following this washing.

2: Do not eat any uncooked or undercooked (rare) meat. Handle raw meat with gloves reserved for this purpose and wash all utensils, surfaces and your hands afterwards. Cook meat to 150 F to kill T.gondii

3: Do not eat unpasteurised dairy products such as cheese, or drink unpasteurised milk especially that of sheep or goats.

4: Do not handle sheep or help out at lambing time as sheep around the time of giving birth can transmit toxoplasmosis to humans.

5: If you do any gardening it is best to wear gloves and wash your hands afterwards.

6: If you have cats try to let them out to defaecate and urinate. If you do have a litter tray get somebody else to clean it out twice per day. (The risk of infection is greater with faeces passed longer than 24 hours). If there is nobody to help then wear gloves, a face mask and wash your hands thoroughly afterwards. Use boiling water to disinfect and clean the tray, put faeces into plastic bags and seal them before putting them into your bin, any cloths used should be disposable and only used once.

7: If your cat seems unwell don't handle it.

8: Don't let your cat onto your work surfaces, or sleep on your bed.

9: Postpone getting a new cat until after your pregnancy.

10: Always wash your hands after handling your cat.

It is possible for cats to be tested to try to find out if they carry toxoplasmosis. These tests involve blood or faecal samples, however I would not rely on the results of these tests as they may be inaccurate; I believe it is best to assume your cat may be carrying toxoplasmosis and take the precautions above. If you do decide to have your cat tested and the results are positive it may pose little risk to you, unless it is actively shedding oocysts: it may be possible for your cat to stay in the veterinary hospital until it has stopped shedding these oocysts in the faeces. If your cat is negative for the disease you can help to prevent it contracting toxoplasmosis by keeping it indoors and feeding a commercial pet food. Remember that cats tend to shed the spores in their faeces most when they first get the disease and the oocysts in the faeces need at least 24 hours to mature before they are infective.

If you are pregnant and concerned about toxoplasmosis speak to your midwife or GP. You may be able to have a blood test to find out if you have already been exposed to toxoplasmosis, which in many cases will mean that you could be immune to it.

© Samantha Coe. All rights reserved. Further information, news and pet-related healthcare articles are available at vetbase.co.uk

Questions Answered

Your Questions Answered

© vetask.com Springing Dragon Limited 2012 | Terms and Conditions and Privacy Policy | All Rights Reserved | All Trademarks observed | No responsibility taken for links to external sites or any content beyond our control | Views expressed by contributors or forum users not endorsed by vetask.com. Disclaimer: The content of this website is based upon the opinions of the authors and contributors, unless otherwise stated. Individual articles, extracts, and any links to external sites are based upon the opinions of the respective author(s). The purpose of this site is the sharing of knowledge and information and you are encouraged to make informed healthcare decisions for animals in your care based upon your research and in consultation with your vet.