Pregnancy, Cats & Toxoplasmosis

by Dr. Kurt Miller, DVM | Oct 31, 2011

Understanding toxoplasmosis

No Need to Panic! 

Relax you can Keep Your Feline Friends.

Lately, PAWS Chicago has noticed an increasing number of cats relinquished by expecting families or those who want to become pregnant due to serious concern over an infection called Toxoplasmosis gondii (Toxoplasmosis). Although Toxoplasmosis is a pathogen that is a major zoonotic disease (a disease spread from animals to people), there is a fair amount of misunderstanding regarding the nature of the disease in both humans and cats. 

This article will provide an overview of the current understanding about toxoplasmosis in cats, and measures that all pregnant women or those considering pregnancy should practice to minimize their potential exposure. These risks are not generally associated with exposure to their own cats! Families and friends, unfortunately you will be cleaning the litter box. Although this article will largely revolve around risks to pregnant women, the basic principles hold true for immunocompromised individuals who also would be considered at greater risk.

Toxoplasmosis is a parasite that can infect almost any warm blooded animal. The cat is the only definitive host that can complete the life cycle and actually shed eggs of the parasite. All mammals including humans are considered intermediate hosts and can become infected, but cannot shed the eggs of the parasite and infect others. It is considered that greater than 40% of humans and 30% of cats have been exposed to Toxoplasmosis and would have a positive antibody test. 

Cats become infected by ingesting animals that have cysts of the parasite in their tissues, being fed raw meat that contain parasite cysts or by ingesting contaminated soil or water that contains parasite eggs shed by other cats. Strictly indoor cats do not have many of these risk factors. 

Humans most commonly contract the disease by ingesting undercooked meat, not properly handling raw meat, inadvertently ingesting eggs of the parasite in contaminated soil while gardening, or eating poorly washed uncooked vegetables and fruits. In people, the disease tends to be self limiting and results in general malaise, fever, and possible lymph node enlargement, but in pregnant women it can also cause numerous affects on the fetus. 

Immunocompromised cats and humans tend to develop more serious forms of the infection. Cats with primary infections generally only pass eggs in their stool for a few days to weeks, and even though they become infected for life they do not again pose a significant risk of infection to others. Eggs passed by infected cats are not infective to others and require at least 24 hours to become infective, so even the fresh stool of a highly parasitized cat is not infective to humans. Cats tend to be fastidious groomers and do not tolerate feces on their fur, therefore transmission from petting cats is unlikely. Eggs passed into the environment will stay infective for many months. This is why gardening and exposure to the meat of an animal that may have grazed on contaminated soil pose much greater risks than an indoor cat.

Lab Tests 

There are a number of reasons that laboratory testing is of limited value and is not currently recommended by either the Centers for Disease Control (CDC) or the American Association of Feline Practitioners (AAFP). Laboratory testing for Toxoplasmosis involves detecting antibodies produced by the host and it takes a number of weeks for a cat or human to produce these antibodies. 

Since a significant percentage of the feline population has been exposed, many cats will have antibodies yet are clinically normal. Cats only shed eggs for a few days post exposure therefore most cats will still be negative while they are shedding eggs. By the time a cat is positive on the test they likely will be done shedding eggs for life. 

The practical significance is that a negative cat is likely a greater risk than a positive cat, yet neither pose a significant risk. There is no way to decide when or if a negative cat will be exposed and shed eggs. Fecal analysis can help determine if a cat is actively shedding the parasite. If a fecal sample is run and demonstrates parasites of a size typical of Toxoplasmosis then pregnant or immunocompromised individuals should not be changing the litter box.

Prevention of Exposure to Toxoplasmosis 

The discussion above illustrates why domestic cats are not a common source of human exposure to Toxoplasmosis, and that with minimal precautions the risks to humans including those pregnant or attempting to become pregnant are minimal. Indeed both the AAFP and the CDC have guidelines that do not recommend testing your cat for Toxoplasmosis, nor suggest relinquishing your cat. 

The risk of contracting Toxoplasmosis from your pet cat is so minimal that the CDC does not suggest testing or relinquishing your cat even if you are immunocompromised and are also pregnant! Since eggs are not infective for at least 24 hours after being passed by the cat, having the litter box changed every day by a non-pregnant, healthy person basically means transmission is not possible. 

Pregnant women should wear gloves when gardening and wash hands thoroughly after being around potentially contaminated soil. The main source of exposure for people is undercooked meat so pregnant women should not handle raw meat, or must wear gloves and should not eat meat that is not cooked to an internal temperature of at least 165 F. 

Further evidence that individual house cats are not the main source of transmission is that there is not a higher incidence of Toxoplasmosis among the veterinary community who are with cats all day. Even immunocompromised individuals with cats do not have a higher incidence of Toxoplasmosis antibodies than those that did not have cats. 

The facts above explain why it is not necessary, nor recommended, to consider relinquishing your cat due to a pregnancy, planned pregnancy or having an immunocompromised person within the household as long as some basic guidelines are followed. Toxoplasmosis is a potentially very serious disease and protective measures should be taken to avoid exposure, but the idea that the indoor house cat is a major risk is not realistic. 

Our cats provide us with so much unconditional love and enrich our lives to such a degree that adding the stress and pain of relinquishing a pet when we likely need them the most could be devastating and more importantly not necessary. 

Do not relinquish your cat! You need them and they need you! 

This article is written from the perspective of a veterinarian who also researched the human health aspects of Toxoplasmosis. Anyone who is pregnant, trying to become pregnant or immunocompromised for any reason needs to consult their own health care provider to discuss their own risks and measures that they feel are appropriate. Two excellent informational websites include the American Association of Feline Practitioners zoonosis guidelines (www.catvets.com) and the Centers for Disease Control (www.cdc.gov) guidelines on opportunistic infections in HIV infected individuals. These websites not only address Toxoplasmosis, but many other potential feline zoonotic diseases for which there appears to be significant misinformation.

Guidelines: Prevent exposure to Toxoplasmosis for you & your cat 

 

• Avoid contact with raw meat, particularly pork, wear gloves when handling raw meat and sterilize utensils when finished. 
• Do not ingest rare meat; meat should be cooked to 165 F. 
• Wear gloves when gardening and wash hands thoroughly after exposure to soil. 
• Wash fruits and vegetables thoroughly to eliminate soil contamination. 
• Cover children’s sand boxes so that they are not used by stray cats as a litter box. 
• Cats should be kept indoors to minimize hunting and exposure to eggs or contaminated water. 
• Litter boxes need to be cleaned daily by someone who is not pregnant or trying to become pregnant. Use liners that can be thrown out often. 
• Cats should be fed only fully cooked food. Do not feed your cat anything raw that could contain live tissue cysts.