Do you know about TOXO, a Cat to Human Disease?

The President’s Hoot
by Richard H. Baker, Ph.D.
May 2022

The terrible disease called Toxoplasmosis is an infection caused by the protozoan parasite Toxoplasma gondii. Over half of the 40 million Americans infected are from food or water contaminated through contact with cat feces, not only from cleaning litter boxes, but also from gardening, sand boxes, or even playing on a beach infested with feces. This disease causes foodborne illness-related deaths and hospitalization infecting over 800,000 Americans each year. An estimated 3,600 individuals annually develop symptomatic eye disease leading to vision loss and an estimated 300–4,000 cases affect pregnant women and their unborn child. 

Individuals whose immune systems are severely compromised can develop encephalitis or have further spread of disease, which can be fatal ( Infections are highest in Florida and other coastal states.  A 2001 study estimated 750 deaths each year. 

This and more details about how the estimated 12,334,800 million pounds of cat feces lead to death, miscarriages, blindness, memory loss, brain cancer, and even estimates of 20% of new cases of psychosis, can be found in a new book by E. Fuller Torrey (2022). “Parasites, Pussycats and Psychosis the Unknown Dangers of Human Toxoplasmosis,” which can be read free online:

Thanks to all five Indian River County (IRC) Commissioners for not removing the requirement that all owners must keep cats on a leash outside their home.  Supporting them, Miranda Hawker, IRC Health Officer/Florida Department of Health, spoke on the major health reasons especially, rabies, and said in 2021, there were 95 cat bites reported in Indian River County. Rabies is a well-known virus transmitted to humans by animal bites four times more in cats than dogs.  Free-roaming cats are responsible for 1/3 of human rabies post-exposure treatments in the U.S.  Children are at the highest risk. Other diseases carried by cats are Cat-scratch Fever, Feline Leukemia Virus, Feline Panleukopenia (feline distemper), Feline Immunodeficiency Virus, and Feline Viral Upper Respiratory Disease. 

Anthony Brown, President of IRC NAACP, described the huge numbers of cats being dumped around Gifford by those who no longer are willing to care for the cats.  Domestic cats are exotic and invasive in the Americas, first introduced to our ecosystem by Europeans only 500 years ago. Tourists come to see our unique Floridian birds and animals, not cats. 

In the U.S. there are estimated 140 million cats (50 million feral and 90 million owned by humans). They are sexually mature at 6 months old and can produce three litters of 2-4 kittens per year, totaling12 per year! A Trap-Neuter-Return (TNR) cat cannot reproduce, but remains an ecological threat to native species, is a potential reservoir of animal and human diseases like Toxoplasmosis.

Cats are America’s favorite pet and deserve to be cuddled, kept warm, dry, and fed to live a long, healthy, and humane life by keeping them indoors.  It is cruel to release them into nature where, even in back yards, they are subject to hawks, owls, snakes, alligators, and bobcats, let alone killed by traffic or shot by kids or hunters.  

What can we do locally? Enforce cat leash laws. Require cats be vaccinated, licensed, and microchipped. To reduce toxoplasmosis and rabies, remove stray and cat colonies. Enact ordinances making illegal releasing or feeding stray cats and wildlife as feeding stations attract racoons, skunks, foxes, coyotes with rabies and toxoplasmosis dangerous to humans. Pass and enforce local and state ordinances prohibiting release of unwanted pet or feral cats into the wild. Educate the public about the impact of free-roaming cats and the diseases they carry on native wildlife and humans, especially childbearing age women.

Let’s protect us and our wildlife by keeping our lands and water from becoming toxoplasma litter boxes.  Keep all cats inside the home where they can live a long, healthy, and humane life.

From the Centers for Disease Control – Parasites – Toxoplasmosis (Toxoplasma infection):

Life cycle of Toxoplasma gondii, a protozoan parasite that infects most species of warm-blooded animals, including humans, and causes the disease toxoplasmosis.

The only known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives). (1) Unsporulated oocysts are shed in the cat’s feces. Although oocysts are usually only shed for 1–3 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. (2) Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water or plant material contaminated with oocysts. Oocysts transform into tachyzoites shortly after ingestion. (3) These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites. (4) Cats become infected after consuming intermediate hosts harboring tissue cysts. Cats may also become infected directly by ingestion of sporulated oocysts. (5) Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment. Humans can become infected by any of several routes:

  • (6) Eating undercooked meat of animals harboring tissue cysts.
  • (7) Consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat).
  • (8) Blood transfusion or organ transplantation.
  • (9) Transplacentally from mother to fetus.

In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. (10) Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens. (11) Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as PCR.

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