By Dr. Michael W. Fox
The Centers for Disease Control and Prevention (CDC) has recently identified toxoplasmosis as one of five neglected parasitic infections of people due to its high prevalence. More than 60 million people in the U.S. are thought to be infected.
The only solution is for owned cats to be kept indoors or at least prevented from killing and consuming infected rodents and for communities to better address free-roaming and feral cats.
This is because the domestic cat is the definitive host for this parasite, Toxoplasma gondii, and can pass it on via feces and contaminated soil, vegetation, feed and food-crops, to other animal species and humans. When a cat ingests infected prey or raw meat, the parasite is released from cysts into the cat’s digestive tract, where it reproduces and produces oocysts. Infected cats then excrete these oocysts in their feces by the millions for about 2 weeks. Most cats infected with T. gondii show no signs of disease. Occasionally, however, a clinical disease called toxoplasmosis occurs, often when the cat’s immune response cannot stop the spread of tachyzoite forms. The disease is more likely to occur in cats with suppressed immune systems, including young kittens and cats with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV). Cats diagnosed with this parasite can effectively treated with a course of antibiotic clindamycin, either alone or in combination with corticosteroids if there is significant inflammation of the eyes or central nervous system.
Communities need to be more vigilant with regard to free roaming and feral cats and owners adopting cats that have been outdoors consider having them tested. ( See https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/toxoplasmosis-cats ).
As this article states: “Indoor cats that do not hunt prey or consume raw meat are unlikely to be infected with T. gondii. In the U.S., people are much more likely to become infected by eating raw meat and unwashed fruits and vegetables than by handling cat feces. The possibility of infection after gardening in soil that has been contaminated with cat feces also exists, and this possibility can be mitigated by wearing gloves and by washing hands after gardening.”
To break the cycle of infection from cats to farm animals-cattle, sheep, goats, pigs, equines, and poultry, cats should not be allowed around farms. This is a global problem affecting the health and productivity of farmed animals, and putting consumers at risk (Stelzer S, et Toxoplasma gondii infection and toxoplasmosis in farm animals: Risk factors and economic impact. Food Waterborne Parasitol. 2019 Apr 3;15:e00037. doi: 10.1016/j.fawpar.2019.e00037 ). Dogs can become infected by ingesting contaminated material like cat feces, raw meat, or soil. Most healthy adult dogs may not show symptoms, but puppies and dogs with weakened immune systems are more susceptible to developing illness. Infected cats can infect wild carnivores such as bobcats and coyotes as well as most other wild species that ingest infected prey or contaminated soil.
Medical studies have established a relationship between infection with this parasite Toxoplasma gondii. and aggressive behavior. It also causes congenital birth defects, ocular disease, and opportunistic illness in HIV/AIDS; latent infection has also been linked to behavioral changes, impulsivity and neuropsychosis.
Considering the almost daily shootings in America and other acts of violence, and not withstanding multiple causes, it would be prudent for public health authorities to have all perpetrators of criminal acts of violence tested for this parasite. (See Emil F. Coccaro, Teodor T. Postolache, Royce Lee et al. Toxoplasma gondii Infection: Relationship With Aggression in Psychiatric Subjects. The Journal of Clinical Psychiatry 2016; 77: 310.4088/JCP.14m09621).
All owned cats should be kept indoors, and can be walked on a leash in a harness or put in an outdoor “catio” enclosure to avoid possible infection from another cat’s feces or from consuming an infected rodent. Their litter boxes should be cleaned with due caution, especially by pregnant women. Feeding cats any kind of raw meat is ill advised.