March 31, 2022 — Doctors are proactive in warning pregnant people about the dangers of exposure to the parasite Toxoplasma gondii, and encourage them to avoid contact with used cat litter as well as take precautions when handling raw meat. However, it’s important for everyone, not just pregnant cat owners, to know about this important parasite and the disease it causes, toxoplasmosis, which is especially dangerous to the unborn fetus and immunocompromised individuals.
What is Toxoplasma gondii?
T. gondii is a protozoan, a small parasite found worldwide. T. gondii can infect all mammals, but cats play an important role in the parasite’s life cycle. Cats get infected by eating animals infected with T. gondii.
After the parasite completes part of its life cycle in the cat’s intestine, it is shed in the stool. T. gondii can be shed in the stool of newly infected cats for 10 to 14 days. Even though the immune system of most cats quickly prevents widespread replication of the organism, T. gondii can live in the tissues of the intestine of cats indefinitely. However, it is rare that once the initial period of shedding is past, a cat will shed the parasite again.
Once passed, T. gondii can live in food, water and soil for up to one year. The organism must go through another process of maturation before it is infectious, a process called sporulation that can take from one to five days. Although a wide range of animals are susceptible to infection, only cats are capable of shedding the parasite in stool.
How common is infection?
According to the Centers for Disease Control and Prevention, at least 60 million people in the United Sates are thought to be infected with T. gondii.
In animals, studies report that 30% of cats and 10% of dogs in the United States have antibodies against T. gondii, a sign of exposure at some time in their lives.
Getting a grasp on exposure and infection measurements in wildlife is difficult but one particular 2017 study took blood samples from a variety of wild animals in the southeastern United States and found evidence of infection in feral hogs, white-tailed deer, raccoons, coyotes, opossum, woodchuck, elk, gray fox and mink. Other researchers have found T. gondii in a number of different species, including sea otters.
How is toxoplasmosis in cats diagnosed?
Cats infected with T. gondii usually show little to know signs of disease. However, occasionally T. gondii may cause clinical disease in cats, humans and other animals. A diagnosis of toxoplasmosis relies on a combination of clinical signs and laboratory tests. Physical examination findings consistent with toxoplasmosis include:
- Inflammation of the eye
- Stiff gait
- Difficulty breathing
- Jaundice (icterus)
- Increased muscle sensitivity
- Neurologic signs
Routine bloodwork can show abnormalities consistent with liver and muscle disease, low blood protein levels and low white blood count.
Measuring blood antibody levels confirms a diagnosis and is essential when testing for toxoplasmosis. Sometimes the organism can be found in analysis of tissues, but it’s rare to find it in stool. PCR can be used to find evidence in blood, spinal fluid, tissue and ocular fluid.
How is toxoplasmosis treated?
Antibiotic therapy and supportive care are the main treatment options for dogs and cats showing signs of illness due to infection. The prognosis for recovery is guarded in very sick animals but much better if signs are mild.
Can toxoplasmosis be prevented?
The answer is a resounding yes. People can take simple steps to keep their homes safe.
- Don’t scoop or change the litterbox if you’re pregnant or immunocompromised.
- Dispose of cat litter properly – flushing litter can introduce T. gondii to the environment where it can infect wildlife.
- Cook meat and poultry appropriately – this will kill any T. gondii present.
- Avoid eating raw shellfish.
- Peel and wash fruits and vegetables carefully.
- Keep outdoor play sandboxes covered.
- Wash cutting boards, dishes, counter tops, utensils and hands after handling raw meat, poultry, seafood or unwashed fruits and vegetables.
- Wear gloves when gardening outside if cat feces might be present.
- Change the litterbox daily.
- Wash hands after handling raw food, after cleaning the litter pan or gardening.
Some experts recommend immunocompromised and pregnant women keep their cats indoors to avoid infection through hunting and eating rodents.
Toxoplasmosis and wildlife
Toxoplasmosis also affects wildlife, sometimes with devastating consequences. Sea otters are vulnerable to toxoplasmosis, but the extent of the problem wasn’t known or well-understood until Morris Animal Foundation-funded researchers solved the mystery of how sea otters were likely infected. These findings resulted in new legislation designed to help keep this vulnerable species healthy.
Another Foundation-funded study focused on the effects of T. gondii infection in hyenas. The research team focused on disease prevalence and kinetics in African hyenas as a model for other large mammals in the region. The team published two papers, one on the effect of infection on steroid blood levels and a second on how infection with T. gondii affects behavior. They hope their work will be a springboard for similar studies in other species with the ultimate goal of finding strategies to minimize infection in local wildlife.
It's still early when it comes to understanding the impact and extent of T. gondii infections in wildlife. As more wildlife come in contact with humans and domestic cats, there is a possibility of greater transmission of the disease.
Toxoplasmosis is a zoonotic disease
It’s important to remember that toxoplasmosis is a zoonotic disease. It can be transmitted from animals to people. Although most people who get infected with T. gondii show no signs of illness, it can be a problem in infants and people who are immunocompromised.