Parasite Causes Concern Among Cat Owners

Parasite causes concern among cats, owners

By Dr. Jill Bowen

Source: Roanoke Times & World News

Q: There have been a couple of articles recently in The Roanoke Times about this thing that cats get called toxoplasmosis. What exactly is toxoplasmosis? Will I be able to see it in the litter box? And should I be worried, since we have always had cats in the home.

A: Toxoplasma gondii is an intracellular coccidian protozoan parasite that can infect all mammals. Cats are the definitive host for this parasite, while all other mammals are intermediate hosts. The definitive host means that sexual reproduction of the parasite takes place in the gut of the cat but not in other animals.

The ripe oocysts (eggs) are passed in the cat's feces and become infective in three to four days and wait to be eaten by an unsuspecting intermediate host. This can be any warm-blooded animal.

Once eaten, the oocysts hatch and spread via the blood stream throughout the body before forming infective cysts in the muscles or internal organs. Once cats become infected, they are only at risk for spreading toxoplasmosis for approximately three weeks, after which time the parasite disappears from the gut and infective oocysts are no longer passed in the feces.

These oocysts do not become infective until three to four days after leaving the cat's body. So provided the dirt tray is scooped on a daily basis, there should be no cause to worry. However, as a precaution, nobody who is pregnant should clean the litter box.

Because of the potential risk to people, it is considered to be an important zoonotic parasite. The oocysts passed in the feces are microscopic and cannot be seen with the naked eye. In people, an infection may show no symptoms or in some cases merely a mild flu.

However, if the newly infected person is pregnant, the developing fetus may be infected, causing congenital birth defects. Serious illness also can result if the person or animal is immuno- compromised.

Humans can become infected with toxoplasmosis in two ways. The first is by direct ingestion of the oocysts. This is done by coming in contact with the cat's feces through cleaning the cat's litter box, weeding the garden or handling contaminated vegetables.

Because of these risks, pregnant women should not clean the cat's litter box, gardeners should wear gloves and all vegetables should be washed thoroughly before cooking.

The second, and more common, way that humans become infected is through handling infected meat. Pigs, sheep, goats and poultry are sources of meat commonly infected with toxoplasma. Deer meat also may contain infective cysts.

When meat is undercooked, these cysts may remain infective and once consumed by a person, go through a rapid proliferation phase, casting off organisms, which spread throughout the body via the blood and become lodged as cysts in many organs such as the heart, eye and central nervous system, as well as the muscles.

This spread is rarely fatal and usually causes no symptoms unless there is already another disease present.

Some doctors have suggested that pregnant women should avoid all raw vegetables, especially when eating out, when lettuce and other vegetables may not have been as thoroughly washed, as they would be at home.

Approximately 30 percent of all cats and 50 percent of people test positive for T. gondii using a blood test. Probably more people become infected from handling raw meat and not washing their hands or cutting boards, etc., properly, than ever become infected from a cat.

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Q: My sister has a male, neutered Siamese that recently began defecating in the same place. His litter box is clean, and there don't seem to be any health problems. There is another cat in the house and one dog, but they have all lived together for more than five years and this problem is recent. My sister thinks that it is the result of a stray cat getting in the house and bothering him.

I think it might have to do with the fact that my sister has a new baby and hasn't been able to give enough attention to the animals. Currently, the cat has been banished to the outdoors; he has a warm doghouse to sleep in, but he really is an indoor cat. He has had three chances to come back inside, and every time, he again defecated in the same spot.

A: This helpful suggestion came from one of my readers and it sounds as if they had an identical problem to your sister. It is certainly worth trying.

"I read the article you wrote recently about poor litter box habits with interest because this happened with our cat that at the time was only about 10 years old.

"I took him to the vet and nothing physically was wrong and he suggested that I set his litter box on the area in our dining room carpet where he had been relieving himself and move it very gradually back to where it had been kept, in a half bath in the hallway; it took a lot of patience, but finally paid off and we never experienced any more problems. But we could never figure out why he acted this way, as we had not gotten new pets, etc. He was strictly a house cat, but we did let him out in a fenced yard some each day."

I presume that your sister has thoroughly cleaned the spot with one of the new enzymatic cleaners, including the area under the carpet. Another suggestion that has worked in some cases is to cover the selected area with aluminum foil.

Another remedy that has been tried with success is to place the cat's food and water on the controversial spot, since most cats will not defecate where they eat -- also, that there are sufficient litter boxes, one for each cat and one extra.

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Dr. Jill Bowen as practiced veterinary medicine in England and Texas, and has taught at Texas A&M University. She lives with her veterinarian husband and two cats in Blacksburg. If you have a question, please write to her in care of The Roanoke Times' New River Current, P.O. Box 540, Christiansburg, VA 24068, or send an e- mail to mjbowen@radford.edu.

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