Updated September 14, 2026
Toxoplasmosis in Hawaiʻi
Cat feces can carry Toxoplasma gondii, the parasite that causes toxoplasmosis. It has killed Hawaiian monk seals, spinner dolphins and native birds. Outdoor cats shed oocysts into soil, where rain can carry them to the ocean. It also poses a health risk to people, especially during pregnancy or with a weakened immune system. The research below explains the problem. If you see cats, feeding sites or cat shit, report them so we can build a better picture of what is happening on the ground.
How cats spread Toxoplasma
Toxoplasma gondii infects most warm-blooded animals. Cats and their wild relatives are the hosts that produce oocysts, the stage shed in feces. Other animals can carry tissue cysts and pass the infection on when eaten, but they do not shed oocysts. A cat can become infected by eating an infected bird or rodent, or by swallowing oocysts from its surroundings (CDC lifecycle).
- Cats usually shed for one to three weeks after their first infection, often when young (Dabritz HA 2010). Repeat shedding has been demonstrated in experiments (Dubey JP 1995), including after a different strain was introduced. How much repeat shedding contributes outdoors is still uncertain (Zulpo et al. 2018).
- Oocysts take one to five days to become infectious. Once in soil, they can persist for months or longer. In a controlled study, about 44% remained viable in damp soil after 100 days, compared with 7% in dry soil (Lélu M 2012). Another experiment found infectivity after two years in seawater stored at 4 °C (Lindsay DS 2009). Those laboratory conditions do not tell us how long oocysts survive at a particular Hawaiʻi beach.
- Cat latrines concentrate feces in one place. A review reported annual environmental oocyst burdens of 3 to 434 per square foot, with higher contamination where cats repeatedly defecate (Torrey EF 2013). A California coastal study estimated annual deposition of about 100 to 4,700 oocysts per square metre (Dabritz HA 2007).
What it does to Hawaiʻi’s wildlife
Hawaiʻi has no native cats. Introduced cats provide the host that sheds these oocysts into the environment. Rain can carry that contamination through our watersheds to the coast. Wildlife can be exposed on land or while feeding at sea.
Hawaiian monk seals
NOAA identifies toxoplasmosis as a leading disease-related cause of monk seal death. Losses have included breeding females and their pups (Barbieri MM 2016). These deaths affect recovery: protozoal disease was among the causes with the greatest effect on the main-island population trend (Harting AL 2021). The runoff study compared a small set of stranded seals; its odds ratio describes that association, not an individual animal’s chance of infection (Robinson SJ 2023). A separate Oʻahu model estimated that about 0.06% of deposited oocysts reached the coast, with human-associated cats contributing most of the modeled load (Robinson S 2024).
Dolphins and whales
Three fatal cases have been reported in Hawaiian spinner dolphins: one in 1990 and two in 2022 (Migaki G 1990, Landrau-Giovannetti N 2022). The parasite genotype in the two later cases also occurs in Oʻahu feral pigs. Only a small share of dead dolphins are recovered.Cascadia Research Collective describes an extrapolation of roughly 60 deaths over 30 years, based on a carcass recovery rate of 5% or less. That estimate is uncertain; three is the documented spinner-dolphin count. A fatal case has also been reported in a Hawaiian bottlenose dolphin (West KL 2025).
Native birds
Five released ʻalalā died of toxoplasmosis (Work TM 2000). In a nēnē study, antibodies were found in 21% of birds sampled on Kauaʻi, 23% on Maui and 48% on Molokaʻi. Toxoplasmosis accounted for about 4% of the nēnē deaths examined (Work TM 2016). Birds can pick up oocysts while feeding on contaminated ground. Keeping cat feces out of places native birds use is part of protecting them.
Evidence on land
On remote Mauna Kea, 37% of sampled feral cats had Toxoplasma antibodies (Danner RM 2007). On Oʻahu, feces from three of four sampled colonies near important bird areas contained Toxoplasma DNA (Lepczyk CA 2020). DNA detection alone does not establish that a sample contains infectious oocysts. A multistate wild-pig survey found antibodies in about 79% of the Hawaiʻi samples (Cleveland CA 2024). Antibodies show past infection; they do not measure the amount of parasite in soil today.
From cat to ocean
California sea-otter research helps explain how a parasite shed on land reaches marine wildlife. Storm runoff carries oocysts to the sea, where particles, biofilms and small animals can concentrate them (Conrad PA 2005, Shapiro K 2012, Krusor C 2015). A wild mussel tested positive after the first autumn rain (Miller MA 2008), and parasite genotypes in sea otters matched those in cats from nearby watersheds (Shapiro K 2019). In a California model, development increased estimated delivery by 44%, heavier rain by 79%, and the combined scenario by 175% (VanWormer E 2016). Those are model results for California.
The Oʻahu runoff study and export model support a land-to-sea pathway here (Robinson SJ 2023, Robinson S 2024). They do not measure the parasite concentration at a beach. Sampling local streams, outfalls and nearshore water would help test the models. Better information about where outdoor cats live and defecate would improve their inputs.
People and pregnancy
Most healthy people have no symptoms after infection. Toxoplasmosis can cause serious illness in people with weakened immune systems, and a new infection during pregnancy can harm the fetus (Fallahi S 2018, Elmore SA 2010). People become infected by swallowing oocysts in contaminated soil, food or water, or by eating undercooked meat containing tissue cysts. CDC and Hawaiʻi Department of Health precautions include:
- Wear gloves when gardening or handling soil and sand, and wash hands afterward.
- Rinse fruit and vegetables under running water. Use a food thermometer to cook meat to the recommended temperature. Avoid untreated drinking water.
- If you are pregnant or immunocompromised, have someone else clean the litter box if possible. Otherwise, wear disposable gloves and wash your hands with soap and water afterward. Change litter daily, before oocysts become infectious.
- Keep children’s sandboxes covered.
- Follow Hawaiʻi DOH brown-water advisories and stay out of affected streams and coastal water. These are general water-quality advisories; they do not measure Toxoplasma.
Concerned about an exposure?
Talk with your healthcare provider, especially if you are pregnant or immunocompromised. They can help decide whether testing is appropriate. A cat report cannot tell you whether you were exposed or whether a beach is safe during pregnancy. Read the official guidance:
The precautions apply wherever cat feces may contaminate soil or water. Wash your hands after handling litter or soil, and keep cats and their feces away from children’s play areas.
What the TNR research says
Trap-neuter-return (TNR) sterilizes cats and returns them outdoors. It prevents those cats from reproducing. Reducing the number of outdoor cats takes sustained work across the area where they live, along with attention to new arrivals. The studies below show why the results depend on how a program is run.
Coverage has to last
Models use different birth rates, survival rates and assumptions about immigration, so there is no single sterilization threshold that applies everywhere (Andersen MC 2004, Foley P 2005, Miller PS 2014). In a twelve-year city study in Israel, maintaining more than 70% neutering across connected areas produced an average decline of about 7% a year. Treating only part of the city did not reduce numbers (Gunther I 2022).
New arrivals change the outcome
Cats move between sites, and abandoned pets add to outdoor populations. In Miller’s model, immigration and abandonment reduced the effect of both sterilization and removal. TNR could still reduce numbers, but connected populations were not eliminated (Miller PS 2014). An Oʻahu model also found that reducing abandonment improved control (Lohr CA 2013). At the University of Central Florida, adoption removed 47% of the cats enrolled in a long-running TNR program (Levy JK 2003). That decline reflects adoption as well as sterilization.
Count cats before claiming success
Surgery totals tell us how much work was done. To judge the result, we also need repeated counts of cats, the proportion sterilized and records of new arrivals. The studies linked here do not establish a statewide population trend for Hawaiʻi. They cannot prove that every local TNR program has succeeded or failed. Publicly funded programs should publish those counts so people can see what their money achieved.
Sterilization can reduce future births, but it does not make a cat immune to Toxoplasma or remove feces already outdoors. Cats returned to a site can still hunt and can become infected (Elmore SA 2010). Protecting native wildlife also requires keeping cats out of wildlife habitat and preventing abandonment. Report outdoor cats and feeding sites so those locations are recorded.
What you can do
Report the cats you see
Report cats you see, food or feeding stations, and cat feces. Include a count and what you actually observed. Reports from repeat visits help document changes at a site. They can also help identify places that need a closer field survey.
Do not feed cats outdoors
Regular feeding supports cats living outdoors, including in places used by native birds. Avoid creating feeding sites in parks, on beaches or in wildlife habitat. If cats need help, contact a local shelter or rescue about bringing them into care.
Keep your cat indoors and sterilized
Keep your cat indoors and feed commercial or fully cooked food to reduce exposure. Have it sterilized. Bag used litter and put it in the trash. Do not flush it or put it in compost or a garden. If you can no longer care for a cat, arrange a safe handoff; never abandon it.
Ask for counts and follow-up
Ask cat-management programs to publish cat counts and sterilization coverage over time. Support sampling at stream mouths and outfalls so researchers can check where contamination reaches the coast. Start with the places where cats are being fed and where their feces collect.
Publications
59 papers on Hawaiʻi wildlife, cat management and the parasite itself. Each entry has a short summary and a source link. Search by author or topic, or show only Hawaiʻi studies. Have a paper to add? Send it to us.
Showing 59 of 59 publications
- 2025
Planning and optimizing neutering programs for free-roaming cat populations: an interactive tool for cost-effective management in closed systems
Cecchetti M, Nelli L. Journal of Applied Ecology 62:1421–1436.
A Bayesian population model fitted to three island censuses, with an interactive planner. Assumes a closed population; movement between sites would need separate treatment.
- 2025Hawaiʻi study
Pacific Islands cetaceans: a review of strandings from 2006–2024
West KL, et al.. Diseases of Aquatic Organisms 164:217–242.
Nineteen-year stranding review for Hawaiʻi and the Pacific Islands, including the infectious-disease findings that place toxoplasmosis among documented causes of death.
- 2024Hawaiʻi study
Toxoplasma gondii in wild pigs in the United States
Cleveland CA, et al.. Veterinary Parasitology 325:110090.
About 79% of Hawaiʻi wild-pig samples had Toxoplasma antibodies, the highest seroprevalence among the 36 states surveyed. Antibodies indicate past infection.
- 2024Hawaiʻi study
Evaluating the risk landscape of Hawaiian monk seal exposure to Toxoplasma gondii
Robinson S, Falinski K, Johnson D, VanWormer E, Shapiro K, Amlin A, Barbieri M. EcoHealth 21:141–154.
Oʻahu model linking cat source loading, watershed export (InVEST) and seal habitat use. About 0.06% of deposited oocysts were estimated to reach the coast; human-associated cats dominated modeled loading, with the highest relative risk on southwest Oʻahu.
- 2023
Counting the Capital's cats: estimating drivers of abundance of free-roaming cats with a novel hierarchical model
Cove MV, Herrmann V, Herrera DJ, Augustine BC, Flockhart DTT, McShea WJ. Ecological Applications 33:e2790.
Nearly 1,500 camera deployments across Washington, DC, and a model that uses both identifiable and unidentifiable photos, gave densities of 0.02 to 1.75 cats per hectare.
- 2023Hawaiʻi study
Terrestrial pathogen pollutant, Toxoplasma gondii, threatens Hawaiian monk seals (Neomonachus schauinslandi) following heavy runoff events
Robinson SJ, Amlin A, Barbieri MM. Journal of Wildlife Diseases 59:1–11.
Compared 12 confirmed and one suspect toxoplasmosis case with 22 controls from 2004–2021. Heavy Oʻahu runoff was associated with toxoplasmosis strandings about three weeks later.
- 2022
Reduction of free-roaming cat population requires high-intensity neutering in spatial contiguity to mitigate compensatory effects
Gunther I, Hawlena H, Azriel L, Gibor D, Berke O, Klement E. Proceedings of the National Academy of Sciences 119:e2119000119.
In a twelve-year city study, maintaining more than 70% neutering across connected areas produced about 7% annual decline. Partial-area treatment did not reduce numbers.
- 2022Hawaiʻi study
Prevalence and genotype of Toxoplasma gondii in stranded Hawaiian cetaceans
Landrau-Giovannetti N, Waltzek TB, López-Orozco N, Su C, Rotstein D, Levine G, Rodrigues TCS, Silva-Krott I, Humann C, West K. Diseases of Aquatic Organisms 152:27–36.
Two of 37 spinner dolphins tested positive and had acute disseminated disease; 51 other cetaceans tested negative. Genotype #24 had also been found in Oʻahu feral pigs.
- 2022
A science-based policy for managing free-roaming cats
Lepczyk CA, Fantle-Lepczyk JE, Dunham KD, Bonnaud E, Lynn J, Doherty TS, Woinarski JCZ. Biological Invasions 24:3693–3701.
Reviews the evidence and calls for treating free-roaming cats as an invasive species, ending outdoor feeding, preventing abandonment and replacing TNR with strategies that reduce numbers.
- 2021
Free-ranging domestic cat abundance and sterilization percentage following five years of a trap-neuter-return program
Coe ST, Elmore JA, Elizondo EC, Loss SR. Wildlife Biology 2021:wlb.00799.
After five years of TNR in Stillwater, Oklahoma, camera-based counts showed no significant decline, and the sterilized fraction reached only about a quarter of identified cats.
- 2021Hawaiʻi study
Population-level impacts of natural and anthropogenic causes-of-death on Hawaiian monk seals in the main Hawaiian Islands
Harting AL, Barbieri MM, Baker JD, Mercer TA, Johanos TC, Robinson SJ, Littnan CL, Colegrove KM, Rotstein DS. Marine Mammal Science 37:235–250.
Ranks protozoal disease among the three causes of death with the largest effect on population growth of the main-island seal population.
- 2021
Counting cats: the integration of expert and citizen science data for unbiased inference of population abundance
McDonald JL, Cleasby IR, Brodbelt DC, Church DB, O'Neill DG. PLOS ONE 16:e0251102.
Citizen reports alone overestimated an unowned cat population 6 to 23 fold; adding expert counts at 10% of sites corrected the estimate. Community reports needed validation against field counts.
- 2020Hawaiʻi study
Genotyping of viable Toxoplasma gondii from the first national survey of feral swine revealed evidence for sylvatic transmission cycle, and presence of highly virulent parasite genotypes
Dubey JP, Cerqueira-Cézar CK, Murata FHA, Verma SK, Kwok OCH, Pedersen K, Rosenthal BM, Su C. Parasitology 147:295–302.
Ten of fourteen viable isolates from Hawaiʻi feral pigs were genotype #24, the same genotype later found in Hawaiian spinner dolphins.
- 2020Hawaiʻi study
Quantifying the presence of feral cat colonies and Toxoplasma gondii in relation to bird conservation areas on Oʻahu, Hawaiʻi
Lepczyk CA, Haman KH, Sizemore GC, Farmer C. Conservation Science and Practice 2:e179.
Cats were present at 25 of 32 public sites near important bird areas, with feeding at 23. Feces from three of four sampled colonies contained Toxoplasma DNA.
- 2020Hawaiʻi study
Managing the effects of introduced predators on Hawaiian endangered seabirds
Raine AF, Driskill S, Vynne M, Harvey D, Pias K. Journal of Wildlife Management 84:425–435.
Of 309 recorded seabird depredations on Kauaʻi in 2011–2017, cats were the leading predator and killed more breeding adults than chicks.
- 2019
A long-term lens: cumulative impacts of free-roaming cat management strategy and intensity on preventable cat mortalities
Boone JD, Miller PS, Briggs JR, Benka VAW, Lawler DF, Slater M, Levy JK, Zawistowski S. Frontiers in Veterinary Science 6:238.
Compared management strategies and intensity over ten years in a population model. Intensive sterilization reduced cat numbers and preventable deaths more than low-intensity sterilization.
- 2019
Toxoplasma gondii in edible fishes captured in the Mediterranean basin
Marino AMF, Giunta RP, Salvaggio A, Castello A, Alfonzetti T, Barbagallo A, Aparo A, Scalzo F, Reale S, Buffolano W, Percipalle M. Zoonoses and Public Health 66:826–834.
Detected Toxoplasma DNA in twelve species of market fish from the Mediterranean. DNA detection alone does not establish that the fish contained infectious oocysts.
- 2019
Environmental transmission of Toxoplasma gondii: oocysts in water, soil and food
Shapiro K, Bahia-Oliveira L, Dixon B, Dumètre A, de Wit LA, VanWormer E, Villena I. Food and Waterborne Parasitology 15:e00049.
Reviews how oocysts move through water, soil and food, including detection methods and their limits.
- 2019
Type X strains of Toxoplasma gondii are virulent for southern sea otters (Enhydra lutris nereis) and present in felids from nearby watersheds
Shapiro K, VanWormer E, Packham A, Dodd E, Conrad PA, Miller M. Proceedings of the Royal Society B 286:20191334.
Parasite genotypes in dead sea otters matched those in wild and domestic cats from nearby watersheds, supporting land-to-sea transmission.
- 2018
An updated literature review on maternal-fetal and reproductive disorders of Toxoplasma gondii infection
Fallahi S, Rostami A, Nourollahpour Shiadeh M, Behniafar H, Paktinat S. Journal of Gynecology Obstetrics and Human Reproduction 47:133–140.
Reviews infection during pregnancy, transmission to the fetus and reproductive outcomes.
- 2016Hawaiʻi study
Protozoal-related mortalities in endangered Hawaiian monk seals Neomonachus schauinslandi
Barbieri MM, Kashinsky L, Rotstein DS, Colegrove KM, Haman KH, Magargal SL, Sweeny AR, Kaufman AC, Grigg ME, Littnan CL. Diseases of Aquatic Organisms 121:85–95.
Eight confirmed and two suspect toxoplasmosis deaths 2001–2015, including the first documented mother-to-pup transmission. Establishes protozoal disease as a leading cause of death in the main islands.
- 2016
Predicting free-roaming cat population densities in urban areas
Flockhart DTT, Norris DR, Coe JB. Animal Conservation 19:472–483.
Unowned cat density can be predicted from household density and income, giving a validated way to estimate city-wide numbers without counting every cat.
- 2016
Coastal development and precipitation drive pathogen flow from land to sea: evidence from a Toxoplasma gondii and felid host system
VanWormer E, Carpenter TE, Singh P, Shapiro K, Wallender WW, Conrad PA, Largier JL, Maneta MP, Mazet JAK. Scientific Reports 6:29252.
In a California watershed model, development increased estimated delivery by 44%, heavier rain by 79%, and the combined scenario by 175%.
- 2016Hawaiʻi study
Toxoplasma gondii antibody prevalence and two new genotypes of the parasite in endangered Hawaiian geese (nene: Branta sandvicensis)
Work TM, Verma SK, Su C, Medeiros J, Kaiakapu T, Kwok OC, Dubey JP. Journal of Wildlife Diseases 52:253–257.
Nēnē seroprevalence of 21% on Kauaʻi, 23% on Maui and 48% on Molokaʻi, with two new genotypes that were geographically segregated. Toxoplasmosis accounted for roughly 4% of examined nēnē deaths.
- 2015
Concentration and retention of Toxoplasma gondii oocysts by marine snails demonstrate a novel mechanism for transmission of terrestrial zoonotic pathogens in coastal ecosystems
Krusor C, Smith WA, Tinker MT, Silver M, Conrad PA, Shapiro K. Environmental Microbiology 17:4527–4537.
Marine snails concentrate oocysts and retain them for days to weeks, a pathway into the diets of coastal predators.
- 2014Hawaiʻi study
Desires and management preferences of stakeholders regarding feral cats in the Hawaiian Islands
Lohr CA, Lepczyk CA. Conservation Biology 28:392–403.
Survey of 1,510 Hawaiʻi residents on cat management preferences, the reference for public attitudes across the islands.
- 2014
Simulating free-roaming cat population management options in open demographic environments
Miller PS, Boone JD, Briggs JR, Lawler DF, Levy JK, Nutter FB, Slater M, Zawistowski S. PLOS ONE 9:e113553.
Modeled cat management with immigration and abandonment. Both TNR and removal could reduce numbers, but connected populations were not eliminated under the modeled conditions.
- 2014
Aquatic polymers can drive pathogen transmission in coastal ecosystems
Shapiro K, Krusor C, Mazzillo FFM, Conrad PA, Largier JL, Mazet JAK, Silver MW. Proceedings of the Royal Society B 281:20141287.
Sticky marine polymers and biofilms on kelp capture oocysts, concentrating them where grazing invertebrates feed.
- 2013Hawaiʻi study
Costs and benefits of trap-neuter-release and euthanasia for removal of urban cats in Oahu, Hawaii
Lohr CA, Cox LJ, Lepczyk CA. Conservation Biology 27:64–73.
Compared costs and population outcomes of TNR and removal in an Oʻahu model. Continued abandonment undermined control; reducing abandonment improved outcomes.
- 2013
Toxoplasma oocysts as a public health problem
Torrey EF, Yolken RH. Trends in Parasitology 29:380–384.
Reviews environmental contamination and reports annual oocyst burdens of 3 to 434 per square foot, with greater contamination where cats repeatedly defecate.
- 2013
Toxoplasma gondii, source to sea: higher contribution of domestic felids to terrestrial parasite loading despite lower infection prevalence
VanWormer E, Conrad PA, Miller MA, Melli AC, Carpenter TE, Mazet JAK. EcoHealth 10:277–289.
Managed feral cats were far less often infected (17%) than unmanaged or wild felids (73–81%), yet domestic cats contributed most of the oocysts because there are so many of them.
- 2012
Quantitative estimation of the viability of Toxoplasma gondii oocysts in soil
Lélu M, Villena I, Dardé ML, Aubert D, Geers R, Dupuis E, Marnef F, Poulle ML, Gotteland C, Dumètre A, Gilot-Fromont E. Applied and Environmental Microbiology 78:5127–5132.
After 100 days under controlled conditions, about 7% of oocysts remained viable in dry soil and 44% in damp soil.
- 2012
Association of Toxoplasma gondii oocysts with fresh, estuarine, and marine macroaggregates
Shapiro K, Silver MW, Largier JL, Conrad PA, Mazet JAK. Limnology and Oceanography 57:449–456.
In seawater, oocysts attach to sinking particle aggregates, which carries them toward the seabed and the animals that feed there.
- 2010
Cats and Toxoplasma: implications for public health
Dabritz HA, Conrad PA. Zoonoses and Public Health 57:34–52.
Review of feline shedding: about 1% of cats shed at any moment, but because shedding lasts only one to two weeks, a much larger share of young cats shed each year.
- 2010Hawaiʻi study
Survival of feral cats, Felis catus (Carnivora: Felidae), on Mauna Kea, Hawaiʻi, based on tooth cementum lines
Danner RM, Farmer C, Hess SC, Stephens RM, Banko PC. Pacific Science 64:381–389.
Annual survival of about 0.65 for cats aged one year or more, with high reproductive output that lets populations rebound quickly after control.
- 2010
Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention
Elmore SA, Jones JL, Conrad PA, Patton S, Lindsay DS, Dubey JP. Trends in Parasitology 26:190–196.
Clinical and epidemiological overview of toxoplasmosis in cats and people, including prevention guidance.
- 2009Hawaiʻi study
An adaptive strategy for reducing feral cat predation on endangered Hawaiian birds
Hess SC, Banko PC, Hansen H. Pacific Conservation Biology 15:56–64.
Across 5,888 trap nights on Mauna Kea, 151 cats were captured. Effort-standardized catch rates ranged from about 1 to 11 cats per 100 trap nights depending on site.
- 2009
Long-term survival of Toxoplasma gondii sporulated oocysts in seawater
Lindsay DS, Dubey JP. Journal of Parasitology 95:1019–1020.
Oocysts remained infectious after 24 months in seawater stored at 4 °C, but not after 24 months at room temperature. This was a laboratory experiment.
- 2009
Evaluation of euthanasia and trap-neuter-return (TNR) programs in managing free-roaming cat populations
Schmidt PM, Swannack TM, Lopez RR, Slater MR. Wildlife Research 36:117–128.
Modeled removal and TNR under different immigration rates. New arrivals reduced the effectiveness of both strategies, with removal generally producing larger reductions.
- 2008Hawaiʻi study
Home range and movements of feral cats on Mauna Kea, Hawaiʻi
Goltz DM, Hess SC, Brinck KW, Banko PC, Danner RM. Pacific Conservation Biology 14:177–184.
Mean home ranges of 772 ha for females and 1,418 ha for males, among the largest recorded for the species. Cats in Hawaiian wildlands move over whole watersheds.
- 2008
Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: new linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters
Miller MA, Miller WA, Conrad PA, James ER, Melli AC, Leutenegger CM, Dabritz HA, Packham AE, Paradies D, Harris M, Ames J, Jessup DA, Worcester K, Grigg ME. International Journal for Parasitology 38:1319–1328.
A wild mussel tested positive immediately after the first autumn rain, and its parasite genotype matched terrestrial carnivores upstream.
- 2007
Detection of Toxoplasma gondii-like oocysts in cat feces and estimates of the environmental oocyst burden
Dabritz HA, Miller MA, Atwill ER, Gardner IA, Leutenegger CM, Melli AC, Conrad PA. Journal of the American Veterinary Medical Association 231:1676–1684.
Estimated an annual deposition of roughly 100 to 4,700 oocysts per square metre across a California coastal community from owned and unowned cats.
- 2007Hawaiʻi study
Evidence of feline immunodeficiency virus, feline leukemia virus, and Toxoplasma gondii in feral cats on Mauna Kea, Hawaii
Danner RM, Goltz DM, Hess SC, Banko PC. Journal of Wildlife Diseases 43:315–318.
Twenty-five of 67 feral cats (37%) on remote Mauna Kea carried Toxoplasma antibodies, showing the parasite cycles even far from towns.
- 2007Hawaiʻi study
Using population genetic tools to develop a control strategy for feral cats (Felis catus) in Hawaiʻi
Hansen H, Hess SC, Cole D, Banko PC. Wildlife Research 34:587–596.
Genetic markers showed gene flow among Hawaiʻi Island cat populations and more dispersal by males. The sampled populations were not isolated by lava flows.
- 2006Hawaiʻi study
Survey for selected pathogens and evaluation of disease risk factors for endangered Hawaiian monk seals in the main Hawaiian Islands
Littnan CL, Stewart BS, Yochem PK, Braun R. EcoHealth 3:232–244.
Two of 18 live main-island seals sampled had Toxoplasma antibodies. This small survey documents exposure, not a population-wide infection rate.
- 2005
Transmission of Toxoplasma: clues from the study of sea otters as sentinels of Toxoplasma gondii flow into the marine environment
Conrad PA, Miller MA, Kreuder C, James ER, Mazet J, Dabritz H, Jessup DA, Gulland F, Grigg ME. International Journal for Parasitology 35:1155–1168.
Established the land-to-sea framework with California sea otters as sentinels, linking coastal freshwater runoff to marine infection.
- 2005
Analysis of the impact of trap-neuter-return programs on populations of feral cats
Foley P, Foley JE, Levy JK, Paik T. Journal of the American Veterinary Medical Association 227:1775–1781.
Evaluated two TNR programs and estimated that 71–94% sterilization would be needed to stop growth under the study assumptions. No consistent reduction in growth was detected.
- 2005Hawaiʻi study
Toxoplasmosis in a Hawaiian monk seal (Monachus schauinslandi)
Honnold SP, Braun R, Scott DP, Sreekumar C, Dubey JP. Journal of Parasitology 91:695–697.
The first confirmed fatal toxoplasmosis in a Hawaiian monk seal, a Type III strain.
- 2004
Use of matrix population models to estimate the efficacy of euthanasia versus trap-neuter-return for management of free-roaming cats
Andersen MC, Martin BJ, Roemer GW. Journal of the American Veterinary Medical Association 225:1871–1876.
In this matrix model, population control required annual removal of at least 50% of cats or neutering more than 75% of the fertile population. These thresholds depend on the model assumptions.
- 2004
Reproductive capacity of free-roaming domestic cats and kitten survival rate
Nutter FB, Levine JF, Stoskopf MK. Journal of the American Veterinary Medical Association 225:1399–1402.
Pregnant cats were found in every month of the year in North Carolina. Females averaged 1.4 litters a year with a median of three kittens; 75% of kittens died or disappeared before six months.
- 2003
Trap/neuter/release methods ineffective in controlling domestic cat colonies on public lands
Castillo D, Clarke AL. Natural Areas Journal 23:247–253.
Two managed colonies in Miami-Dade parks grew despite sterilization, mainly because people abandoned new cats at the feeding sites.
- 2003
Evaluation of the effect of a long-term trap-neuter-return and adoption program on a free-roaming cat population
Levy JK, Gale DW, Gale LA. Journal of the American Veterinary Medical Association 222:42–46.
A campus population fell from 68 to 23 cats over eleven years. Adoption removed 47% of enrolled cats, so both removal and sterilization contributed to the program.
- 2002Hawaiʻi study
Toxoplasmosis in three species of native and introduced Hawaiian birds
Work TM, Massey JG, Lindsay DS, Dubey JP. Journal of Parasitology 88:1040–1042.
Fatal toxoplasmosis in nēnē, a red-footed booby and an Erckel's francolin, showing exposure across native and introduced birds.
- 2000Hawaiʻi study
Home range and diet of feral cats in Hawaii forests
Smucker TD, Lindsey GD, Mosher SM. Pacific Conservation Biology 6:229–237.
Feral cats persist in montane wet forest at Hakalau, ranging over several square kilometres, with rodents and birds in the diet.
- 2000Hawaiʻi study
Fatal toxoplasmosis in free-ranging endangered ʻalalā from Hawaii
Work TM, Massey JG, Rideout BA, Gardiner CH, Ledig DB, Kwok OCH, Dubey JP. Journal of Wildlife Diseases 36:205–212.
Documents fatal toxoplasmosis in five released ʻalalā (Hawaiian crows).
- 1996
Infectivity and pathogenicity of Toxoplasma gondii oocysts for cats
Dubey JP. Journal of Parasitology 82:957–961.
Individual cats shed between 7 million and 162 million oocysts during a single infection.
- 1995
Duration of immunity to shedding of Toxoplasma gondii oocysts by cats
Dubey JP. Journal of Parasitology 81:410–415.
An experimental study of how long protection against repeat shedding lasts. Four of nine cats shed again when challenged 77 months after their first infection.
- 1990Hawaiʻi study
Fatal disseminated toxoplasmosis in a spinner dolphin (Stenella longirostris)
Migaki G, Sawa TR, Dubey JP. Veterinary Pathology 27:463–464.
The first report of fatal disseminated toxoplasmosis in a Hawaiian spinner dolphin.
- 1975
Soil survival of Toxoplasma oocysts in Kansas and Costa Rica
Frenkel JK, Ruiz A, Chinchilla M. American Journal of Tropical Medicine and Hygiene 24:439–443.
Oocysts remained infectious for one year at three shaded Costa Rica sites. A Kansas soil deposit was followed for 18 months.
Common questions
- Can I get toxoplasmosis from petting a cat?
- Petting a cat is not a usual route of infection. People generally become infected by swallowing the parasite in contaminated food, water or material from cat feces. Wash your hands after handling litter or soil and before eating.
- Do sterilized cats still spread the parasite?
- They can. Sterilization prevents reproduction, but it does not prevent infection or shedding. Cats usually shed after their first infection. Reducing births can reduce future sources of contamination, while keeping cats indoors prevents them from depositing feces outside.
- Is a beach near a cat colony dangerous?
- A nearby cat report cannot tell you the parasite concentration in the sand or water. Follow DOH water-quality advisories and the precautions above. The absence of an advisory does not establish that a beach is free of Toxoplasma.
- What happens to my report?
- We store the location you submit and show a generalized cell on the public map. Reports document what people observed at a place and time; follow-up surveys are needed to estimate populations reliably. See the privacy policy.
- Where does this page get its numbers?
- The source links lead to research papers and official agency guidance. Study results describe the animals, places and conditions examined; model estimates depend on their assumptions. Send corrections or missing sources to contact@nene.org.