Roundworm Transmission from Cats to Humans and Treatment
Humans acquire roundworm (Toxocara) infections from cats primarily by accidentally ingesting embryonated eggs from contaminated soil, not through direct contact with cats, and treatment involves anthelmintics like albendazole or mebendazole for symptomatic cases. 1, 2
Transmission Routes
Direct contact with cats does NOT transmit infection because Toxocara eggs require a minimum of 2 weeks in the environment to embryonate and become infectious. 3 The key transmission pathways include:
Primary Routes
- Contaminated soil exposure: Touching mouth with hands after gardening, cleaning litter boxes, or contact with anything contaminated by cat feces 1
- Unwashed produce: Eating fruits or vegetables contaminated with soil containing embryonated eggs 1
- Environmental contamination: Accidental ingestion of embryonated eggs from contaminated surfaces, sandboxes, or yards 3, 2
Important Caveat
Approximately 78% of Toxocara infections in the United States are transmitted via oocysts (from environmental contamination), not from direct animal contact. 4 Children are at highest risk due to closer soil contact, poor hand hygiene, and pica behavior. 3
Clinical Manifestations
The infection presents in several distinct syndromes:
- Visceral larva migrans: Fever, eosinophilia, wheezing, cough, abdominal pain, and hepatosplenomegaly 1
- Ocular toxocariasis: Visual changes, retinal granuloma, or uveitis (eosinophilia less common in isolated ocular disease) 1
- Neurotoxocariasis: Myelitis, encephalitis, or meningitis 1
- Covert toxocariasis: Mild, nonspecific symptoms 2
Most infections remain asymptomatic. 2
Treatment
For symptomatic infections, anthelmintics are the primary treatment:
- Albendazole, mebendazole, or thiabendazole are effective options 2
- Anti-inflammatory corticosteroids may be given concurrently, particularly for ocular or severe visceral disease 2
- Laser photocoagulation for ocular lesions 3
Critical Warning
Anthelmintic treatment can cause hypersensitivity reactions from dying larvae, requiring careful monitoring. 3
Prevention Strategies
Environmental hygiene is paramount since direct cat contact is not the risk:
Household Measures
- Daily litter box changes (Toxocara eggs require 1-5 days to become infectious after shedding) 4
- Thorough handwashing after any soil contact, gardening, or litter box handling 4
- Wash all fruits and vegetables thoroughly before consumption 1, 5
Cat Management
- Keep cats indoors to prevent hunting and environmental contamination 4
- Feed only commercial or well-cooked food, never raw meat 4
- Avoid adopting stray cats or kittens under 1 year of age (higher infection rates) 4, 6
- Regular deworming of cats, starting at early age 2
High-Risk Populations
For immunocompromised individuals (HIV-infected persons), the same prevention measures apply, with emphasis on avoiding contact with cat feces and maintaining strict hand hygiene. 4
Key Clinical Pitfall
Do not assume cat ownership equals infection risk. The evidence shows no direct relationship between household cat exposure and infection because eggs must embryonate in the environment first. 3 The actual risk comes from environmental contamination in yards, sandboxes, and public spaces where infected cat feces have been deposited weeks to months earlier.