One Health approach on toxocariasis and ophthalmic assessment in owners and dogs
A newly released study in Scientific Reports highlights why toxocariasis must be approached through a true One Health lens — especially in coastal communities where environmental exposure is high.
Researchers investigated human and canine toxocariasis in a seashore region of southern Brazil known to be endemic for Toxocara spp. The team conducted serologic testing in dog owners, fecal and hair analysis in dogs, and ophthalmic examinations in both people and pets to better understand shared risk and ocular impact.
High Human Exposure, Low Egg Detection
Among 342 dog owners tested, 32.7 percent were seropositive for anti-Toxocara IgG antibodies, indicating prior exposure. Lower family income was identified as a significant risk factor. Interestingly, while human exposure was relatively high, parasite eggs were detected in only a small percentage of dogs: 2.78 percent of fecal samples and 2.12 percent of hair samples.
However, untreated water increased a dog’s likelihood of carrying Toxocara canis eggs by more than six times. Purebred status and outdoor access were identified as protective factors in the statistical model, suggesting environmental and management variables strongly influence transmission risk.
Ocular Findings in Owners
Only one individual showed classic signs highly suggestive of ocular toxocariasis, and the lesion was already in a scarred stage. However, among 32 individuals with retinal scarring compatible with prior inflammation, nearly one third were seropositive for Toxocara antibodies. This suggests that subclinical or previously undiagnosed ocular involvement may be more common than overt disease.
Widespread Ophthalmic Abnormalities in Dogs
Ophthalmic exams revealed abnormalities in 86.5 percent of evaluated dogs. Most were nonspecific chronic lesions, but notable findings included Florida Spot Keratopathy in 5.1 percent and retinopathy in 4.6 percent of dogs. Although less common, fundoscopic changes were significantly associated with Toxocara exposure in both owners and their pets.
The prevalence of Florida Spot Keratopathy in this population was considered particularly high, raising additional environmental or infectious considerations for clinicians practicing in similar regions.
Why This Matters for Veterinary Professionals
This study underscores the importance of coordinated human–animal health surveillance in endemic areas. Even when parasite egg detection in dogs appears low, human seroprevalence and ocular findings may reveal ongoing environmental exposure. Shared fundoscopic abnormalities between owners and dogs reinforce that toxocariasis is not simply a veterinary issue or a public health issue — it is both.
For veterinary teams, this means emphasizing routine deworming, environmental hygiene, safe water access, and client education. For clinicians on either side of the human–animal divide, it reinforces the need to consider zoonotic parasites when evaluating unexplained ocular changes.
The take-home message is clear: toxocariasis remains a neglected but clinically relevant zoonosis. A One Health approach — integrating veterinary care, public health awareness, and ophthalmic assessment — is essential for fully understanding and reducing its impact.
