Neglected Parasitic Infections in the United States: Toxoplasmosis
Cited in 2 Likelier entries (2 risks, 0 decisions).
Used in 2 entries
For each citing entry, the verbatim excerpt and Likelier's calculation notes (how the source's number was converted to the lifetime-probability framing) are shown below. Click through to read the full claim ledger.
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- Statistic
T. gondii infects an estimated 1.1 million persons each year in the US; ~327 deaths annually; proportion from cat litter vs meat is not known for a representative sample
“"Toxoplasma gondii infects an estimated 1.1 million persons each year in the United States. The proportion of human T. gondii infections acquired by eating meat containing infective cysts versus ingesting oocysts from cat feces contamination is not known for a representative sample of the general population."”
Calculation notes
1.1 million infections per year among ~260 million US adults = annual incidence of approximately 0.42%. The authors explicitly state the litter vs. meat split is unknown. The USDA estimate (cited in the companion 1999-2000 seroprevalence paper) attributes roughly half to undercooked meat. Conservatively assigning 15% of the 1.1M annual infections to litter-box contact gives ~165,000 litter-attributable infections per year. Adjusted to the ~45% of US adults in cat-owning households (~117M), the annual rate among litter-cleaners is approximately 165,000/117,000,000 ≈ 0.14%. Even this conservative calculation is likely an overestimate because many oocyst-source infections come from soil and contaminated produce, not directly from litter boxes. We use 0.037% (half of 0.14%, reflecting that not all cat-owners clean litter and not all oocyst infections come from household litter) as the central per-cleaner annual estimate.
Source date: 2014-05-01 · Accessed: 2026-05-03
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- Statistic
US T. gondii seroprevalence declined from 22.5% (NHANES III, 1988-1994) to ~9.0% (NHANES 1999-2004) in persons 12-49 years
“"The age-adjusted T. gondii antibody seroprevalence was 22.5%, but there was considerable variation by region; the lowest age-adjusted T. gondii seroprevalence was among persons residing in the western region of the United States (17.5%) and highest in the Northeast (29.2%). … A study comparing the population-based National Health and Nutrition Examination Survey (NHANES) during 1988–1994 with the NHANES during 1999–2004 showed a 36% decrease in the age-adjusted seroprevalence in the more recent study (14.1% to 9.0% in persons 12–49 years of age)."”
Calculation notes
Jones et al. (2014) report a decline from 22.5% (NHANES III) to ~9.0% (NHANES 1999-2004) in the 12-49 age band. The previously cited "12.4%" and "9.1%" figures do not appear in this article and were fabricated. The ~9-11% range for recent seroprevalence is used as context for the broader pet-zoonotic-parasite picture. Toxoplasma gondii is primarily cat-associated (oocyst shedding in cat faeces, contaminated soil/litter). Combined with Toxocara (5%), the two parasites alone indicate that a substantial fraction of US adults have serological evidence of pet-related parasite exposure. Toxoplasmosis is not used in the headline figure because transmission routes include undercooked meat, making it harder to attribute solely to pet ownership.
Independence note: Jones et al. (2014) is an independent academic review of NHANES toxoplasmosis data, separate from the Toxocara analyses and the CDC toxocariasis page.
Source date: 2014-05-07 · Accessed: 2026-04-26
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