What Every Public Health Official Should Know About Community Cats

If you see a cat outdoors, the cat could be stray, feral, or free-roaming. Those terms are often used interchangeably by the general public when referring to cats who live outdoors. At Best Friends Animal Society, we like to call these outdoor cats "community cats" because they are valued members of our community and are often cared for by community members.

Trap-neuter-vaccinate-return (TNVR) is a common-sense, cost-effective solution for managing community cat populations by preventing additional births — rather than trying to round up, house, feed, and kill more cats. Despite TNVR becoming increasingly popular over the past few decades, a great deal of misinformation exists regarding TNVR programs and community cats in general.

To protect your community’s public health and welfare, you need to know the facts.

Community cat fact vs. fiction

Fiction: TNVR doesn’t work.

Facts: The science is quite clear: There are only two ways proven to reduce, and eventually eliminate, a population of community cats: intensive TNVR efforts or intensive eradication efforts, such as those done using poison, disease, lethal trapping, and hunting on small oceanic islands.^1,2 

Given the horrendous methods employed — and costs that can exceed $100,000 per square mile³ — eradication is a nonstarter in the U.S. The only fiscally sound option, then, is TNVR. Arguments about the limitations of its effectiveness, the alleged impact of outdoor cats on the environment, and so forth largely miss the point. In the vast majority of instances, TNVR is simply the best option available to humanely reduce the outdoor cat population and any related nuisance complaints.

A number of TNVR program success stories have demonstrated dramatic population reductions and, in some cases, have completely eliminated community cat colonies. 

Fiction: TNVR increases the risk of rabies transmission to humans, domestic animals, and wildlife.

Facts: The Centers for Disease Control and Prevention (CDC) reports: “Over the last 100 years, rabies in the United States has changed dramatically. More than 90 percent of all animal cases reported annually … now occur in wildlife.”⁴ 

Vaccination against rabies is common practice for TNVR programs in the U.S., especially in parts of the country where rabies in cats occurs most frequently. (Best Friends Animal Society recommends that vaccination against rabies be included in all TNVR programs and that reasonable attempts are made to assure that boosters are also administered.) In fact, a 2012 nationwide survey of feral cat groups conducted by Alley Cat Rescue revealed that 96% of the groups provide rabies vaccinations as part of their TNVR programs.⁵ 

TNVR therefore protects public health by creating a powerful barrier between wildlife and humans. And not every cat needs to be vaccinated to achieve “herd immunity”⁶ (Figure 1). The public health benefit of TNVR is therefore two-fold: The cats are vaccinated, and their numbers are reduced over time.

Since 1975, the CDC has documented 109 cases of human rabies in the U.S., most of which were attributed to contact with wildlife. Of the 26 cases attributed to domestic animals, 25 were attributed to dogs (nearly all exposures were outside the U.S.). Just one case was attributed to contact with a cat.⁷ (Seven cases were the result of organ and arterial transplants.)

Fiction: TNVR doesn’t reduce the spread of toxoplasmosis to humans, domestic animals, and wildlife.

Facts: Although cats (domestic as well as wild felids, such as bobcats and mountain lions) are the only known “definitive host” of the Toxoplasma gondii parasite, infected cats generally shed the microscopic egg-like spores in their feces only once for a one-week period.⁸ 

According to the CDC, humans can become infected by consuming the undercooked meat of an infected animal or by the accidental ingestion of oocysts found in the environment (e.g., garden vegetables from contaminated soil). Most people never exhibit symptoms, and for those who do, illness is generally mild. 

Prevention is straightforward: Meat should be frozen and/or cooked thoroughly (or avoided altogether), and hands should be washed with soap and warm water after handling meat. People with cats should change litter boxes daily, washing hands afterward. Gloves should be worn while gardening or otherwise in contact with soil or sand.⁹

Data from the large-scale National Health and Nutrition Examination Survey reveal a significant decrease between 1988 and 2010 in the
age-adjusted infection rate of toxoplasmosis among people 12–49 years of age born in the U.S. (Figure 2).¹⁰ Over this same period, the popularity of TNVR increased dramatically,¹¹ raising doubts about any suggestion that community cats pose a serious threat of infecting humans with the T. gondii parasite. 

Moreover, research has shown that cats living in close proximity to humans — typical of TNVR cats — are much less likely to be exposed to the T. gondii parasite than “solitary, feral domestic cats living in undeveloped landscapes.”¹² 

Feeding community cats — common practice even where robust TNVR programs don’t exist — therefore seems to be an effective measure of reducing the spread of toxoplasmosis in cats, humans and wildlife. Of course, an active, targeted TNVR program would likely reduce the population of community cats, further reducing the risks.

Fiction: Contact with cats increases the risk of several diseases, including mental illness.

Facts: Many of the early studies on the subject, under more careful examination, have proved to be seriously flawed.^13,14 More recently, large-scale longitudinal studies have challenged the findings of earlier research — finding no evidence, for example, of a link between having a cat in early childhood and “psychotic disorders” later in life¹⁴ and, more generally, “little evidence that T. gondii was related to increased risk of psychiatric disorder, poor impulse control, personality aberrations or neurocognitive impairment.”¹⁵

Fiction: TNVR is too costly to be feasible.

Facts: Studies show that TNVR can actually save taxpayers money. A review of data from Hillsborough County Animal Services (HCAS) in Tampa, Florida, for example, found the cost to sterilize and vaccinate colony cats to be $65 per cat “as opposed to $168 for (HCAS) picking up, handling, and disposing of an animal.”¹⁶ 

This is similar to cost estimates from San José Animal Care and Services, in California, which reports a cost of approximately $72 per cat for “vaccinations against rabies and other common cat disease, flea treatment, ear treatment, microchip, and ear-tipping.”¹⁷ 

Estimates compiled from across the U.S. by researchers with the Alliance for Contraception in Cats & Dogs indicate less of a cost difference — but with TNVR still more economical (about $20 to $97 per cat) than the traditional impoundment and lethal injection (about $52 to $123 per cat).

Dr. Donna M. Alexander, administrator for Cook County (Illinois) Animal and Rabies Control, has testified in court that “prior to adoption of the TNR programs, local municipalities were trapping and euthanizing approximately 500 to 600 feral cats per year, at a cost to taxpayers of about $135 per cat.” Implementation of the county’s TNVR program, then about five or six years old, “had saved the county over $1.5 million, primarily resulting from having fewer feral cats to euthanize.”¹⁸

Literature cited

(1) Bester, M. N.; Bloomer, J. P.; Aarde, R. J. van; Erasmus, B. H.; Rensburg, P. J. J. van; Skinner, J. D.; Howell, P. G.; Naude, T. W. A Review of the Successful Eradication of Feral Cats from Sub-Antarctic Marion Island, Southern Indian Ocean. South African Journal of Wildlife Research 2002, 32 (1), 65–73.

(2) Ratcliffe, N.; Bell, M.; Pelembe, T.; Boyle, D.; Benjamin, R.; White, R.; Godley, B.; Stevenson, J.; Sanders, S. The Eradication of Feral Cats from Ascension Island and Its Subsequent Recolonization by Seabirds. Oryx 2009, 44 (01), 20–29.

(3) Campbell, K. J.; Harper, G.; Algar, D.; Hanson, C. C.; Keitt, B. S.; Robinson, S. Review of Feral Cat Eradications on Islands. In Island invasives: eradication and management; Veitch, C. R., Clout, M. N., Towns, D. R., Eds.; IUCN: Gland, Switzerland, 2011.

(4) CDC. Rabies in the U.S.: Public Health Importance of Rabies. 2011.

(5) ACR. Alley Cat Rescue’s National Feral Cat Survey. PR Newswire 2012.

(6) Jekel, J. F. Epidemiology, Biostatistics, and Preventive Medicine, 3rd ed.; Elsevier Health Sciences, 2007.

(7) Sung, J. H.; Hayano, M.; Okagaki, T.; Mastri, A. A Case of Human Rabies and Ultrastructure of the Negri Body. Journal of Neuropathology & Experimental Neurology 1976, 35 (5), 541–559.

(8) Dubey, J. P.; Jones, J. L. Toxoplasma Gondii Infection in Humans and Animals in the United States. International Journal for Parasitology 2008, 38 (11), 1257–1278.

(9) CDC. Toxoplasmosis: Prevention & Control cdc.gov/parasites/toxoplasmosis/prevent.html (accessed Mar 5, 2018).

(10) Krueger, W.; Hilborn, E.; Converse, R.; Wade, T. Drinking Water Source and Human Toxoplasma Gondii Infection in the United States: A Cross-Sectional Analysis of NHANES Data. BMC Public Health 2014, 14 (1), 711.

(11) Holtz, E. Trap-Neuter-Return Ordinances and Policies in the United States: The Future of Animal Control; Law & Policy Brief; Alley Cat Allies: Bethesda, MD, 2014.

(12) VanWormer, E.; Conrad, P.; Miller, M.; Melli, A.; Carpenter, T.; Mazet, J. K. Toxoplasma Gondii, Source to Sea: Higher Contribution of Domestic Felids to Terrestrial Parasite Loading Despite Lower Infection Prevalence. EcoHealth 2013, 1–13.

(13) Wolf, P. J.; Hamilton, F. E. Flawed Analyses Undermine Proposed Relationship between Childhood Cat Ownership and Schizophrenia. Schizophrenia Research 2015.

(14) Solmi, F.; Hayes, J. F.; Lewis, G.; Kirkbride, J. B. Curiosity Killed the Cat: No Evidence of an Association between Cat Ownership and Psychotic Symptoms at Ages 13 and 18 Years in a UK General Population Cohort. Psychological Medicine 2017, 1–9.

(15) Sugden, K.; Moffitt, T. E.; Pinto, L.; Poulton, R.; Williams, B. S.; Caspi, A. Is Toxoplasma Gondii Infection Related to Brain and Behavior Impairments in Humans? Evidence from a Population-Representative Birth Cohort. PLoS ONE 2016, 11 (2), e0148435.

(16) Hamilton, F. E. Leading and Organizing Social Change for Companion Animals. Anthrozoös 2010, 23 (3), 277–292.

(17) Johnson, K. L.; Cicirelli, J. Study of the Effect on Shelter Cat Intakes and Euthanasia from a Shelter Neuter Return Project of 10,080 Cats from March 2010 to June 2014. PeerJ 2014, 2, e646.

(18) County of Cook v. Village of Bridgeview; 2014.