Cats May Prove Deadly to Organ Transplant Recipients

Cats May Prove Deadly to Organ Transplant Recipients


When Miller Nance received his new heart, he had no idea he would have to give away his beloved cat, Cleavon. Although the big, black Persian cat, with his watery, yellow eyes and flattened face looked harmless enough, he might have been carrying a dangerous parasite that could have life-threatening consequences to his owner. The parasite, Toxoplasma gondii can cause a serious infection known as toxoplasmosis, which for the severely immunosuppressed could lead to death.

“The doctors told me it would be best to get rid of Cleavon,” explained Nance. “They told me cats may prove deadly to organ transplant recipients and I just couldn’t take the chance.”

A recent study has brought Toxoplasma gondii to the world’s attention, citing its ability to rewire the brain of mice and rats, leaving them drawn to cat urine and unafraid of their worst enemy. Yet, for years, pregnant women have been told not to touch cats or their litter boxes for fear of toxoplasmosis being transmitted to their unborn babies. Although the mother may have no symptoms to alert her of an infection, the baby could contract the infection and eventually suffer from blindness or retardation. Cats are also a big source of concern in the world for those with suppressed immune systems, such as HIV patients and recipients of solid organ transplants.

Today in the United States, over 60 million adults and children carry the Toxoplasma gondii parasite, according to the Centers for Disease Control and Prevention. In those with healthy immune systems, it probably will never turn into a serious illness, but for those with compromised immune systems, becoming infected by this parasite can cause severe results. For organ transplant recipients, whose immune systems are deliberately suppressed to avoid rejection of the new organ, having toxoplasmosis could reactive a more chronic infection leading to life-threatening circumstances or death.

When Miller Nance was told to find a new home for his cat, there was a good reason. Domestic cats are leading transmitters of the oocysts, the thick-walled spores of the parasite, which can live outside a host for long periods of time. When a cat eats a mouse with the Toxoplasma gondii parasite, the oocysts are passed out of the cat into its feces, where they remain alive for long periods in a litter box; for months or years in moist soil. For this reason, the simple act of organ transplant recipients cleaning the cat’s litter box may prove deadly.

Direct contact with cat feces is not the most prevalent way for an organ transplant recipient to contract toxoplasmosis. During transplantation an organ or bone marrow recipient’s donor may have been infected, transmitting it into the patient. If the transplant patient had the infection before the immune system was compromised the introduction by the donor organ or bone marrow of a more chronic disease could cause toxoplasmosis to arise. The only way to try and avoid these scenarios is for anyone at risk for Toxoplasma gondii to undergo antibody screening and for anyone who owns a cat to take precautions when around cat feces.

To lessen exposure, transplant recipients are advised to avoid litter boxes altogether, but if contact with litter boxes is made, to wash their hands thoroughly and boil empty litter trays for five minutes to kill any infectious oocysts. Since cat feces may be present in yards and gardens, recipients should always wear gloves when gardening or handling soil or sand. Vegetables from gardens, where a cat may have defecated, should be thoroughly washed before cooking or eating. To avoid further infection, feed cats only dry, canned, or cooked food. The Toxoplasma gondii parasite may prove deadly to organ transplant recipients, so like Mr. Nance, it may be smarter to put the cats out.

By: Lisa Nance

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