Study links toxocariasis exposure and eye findings in people, dogs

CURRENT BRIEF VERSION: A new Scientific Reports study is drawing attention to toxocariasis as a shared human-animal-environment issue, not just a canine parasite problem. Researchers in southern Brazil used a One Health design to assess 342 people and their dogs in a coastal Atlantic Forest region, finding that 112 participants, or 32.7%, were seropositive for anti-Toxocara antibodies, while Toxocara eggs were detected in only 2.8% of dog fecal samples and 2.1% of dog hair samples. The study also added ophthalmic exams to the picture: one human participant had a lesion highly suggestive of ocular toxocariasis, 32 others had retinal scars compatible with prior chorioretinitis, and 86.5% of examined dogs had at least one ophthalmic abnormality, most commonly chronic ocular surface or adnexal lesions. The paper was published February 24, 2026, and the authors say it is the first study to combine human serology, dog feces testing, and ophthalmic assessment of both pet parents and dogs in the same toxocariasis investigation. (nature.com)

Why it matters: For veterinary professionals, the key takeaway is that low fecal detection in dogs didn’t mean low human exposure. That gap reinforces a familiar parasitology problem: fecal testing can underestimate true exposure risk, especially in endemic settings and in adult animals, where immunity may reduce patent egg shedding. Broader veterinary literature also helps explain why. Toxocara canis has a complex life cycle, with transplacental transmission a major route of canine infection, and eggs shed in feces are not immediately infective to people; they typically need 2 to 7 weeks in the environment to embryonate. The study also found that untreated water increased the odds of canine contamination or infection 6.3-fold, while human seropositivity was associated in multivariable analysis with having dogs and cats, soil contact, and artesian well water. Taken together, the findings support routine parasite prevention, prompt feces removal before eggs become infective, environmental hygiene counseling, and closer attention to ocular findings that may signal broader exposure patterns in a household rather than direct proof of transmission from dog to person. CDC and prior veterinary literature also underscore that Toxocara can cause visceral, ocular, neurologic, and covert toxocarosis in people, with permanent visual damage possible in ocular cases. (nature.com)

What to watch: Expect follow-up work on whether canine retinal changes can function as practical sentinel markers for shared household exposure, and whether more sensitive diagnostics can better link ocular findings, serology, and environmental contamination. (nature.com)