What should I test for after exposure to cat feces?

Testing After Cat Feces Exposure

The single most important test after cat feces exposure is serum IgG antibody testing for Toxoplasma gondii, as this is the primary pathogen of clinical concern transmitted through cat feces that requires specific diagnostic evaluation. 1

Primary Testing Recommendation

Toxoplasma IgG Antibody Testing

• Test for IgG antibody to Toxoplasma gondii to detect latent infection, particularly important for immunocompromised individuals and pregnant women 1
• This testing should be performed soon after known exposure, especially in high-risk populations 1
• The presence or absence of IgG antibodies helps determine if acute infection has occurred versus pre-existing immunity 1

Context-Dependent Considerations

For Immunocompromised Patients (HIV-infected or other immunosuppression)

• Toxoplasma IgG testing is essential as these patients are at highest risk for toxoplasmic encephalitis, a life-threatening complication 1
• Testing helps guide prophylaxis decisions in severely immunosuppressed individuals 1

For Pregnant Women

• Immediate Toxoplasma serology is critical due to risk of congenital toxoplasmosis with devastating fetal consequences 1
• Serial testing may be needed to detect seroconversion if initial testing is negative 1

Additional Pathogen Considerations

While less commonly requiring specific testing after isolated exposure, cat feces can transmit:

• Cryptosporidium: Generally diagnosed clinically if diarrhea develops; stool testing for ova and parasites or specific Cryptosporidium antigen testing if symptomatic 1
• Salmonella and Campylobacter: Stool culture only if gastrointestinal symptoms develop 1
• Bartonella (cat scratch disease): Typically transmitted through scratches/bites rather than feces; testing only if compatible symptoms develop 1

Important Clinical Caveats

Testing Cats is NOT Recommended

• Do not test cats for Toxoplasma or other pathogens as this does not provide useful clinical information for human risk assessment 1
• Cat serology does not predict oocyst shedding status 2
• Fecal examination for oocysts has limited utility as shedding is brief and intermittent 2, 3

Reassuring Evidence

• Veterinary staff with regular cat exposure show only 14.2% seropositivity, suggesting routine cat contact (even occupational) does not dramatically increase infection risk 4
• Most human Toxoplasma infections (78%) come from environmental contamination rather than direct cat contact 5
• Oocysts require 1-5 days to become infectious after shedding, so immediate exposure to fresh feces carries lower risk 5

When NOT to Test

• Asymptomatic immunocompetent, non-pregnant individuals with isolated exposure do not require routine testing unless symptoms develop 1
• The low yield and lack of specific interventions make universal testing after exposure unnecessary in this population

Symptom-Directed Testing

If symptoms develop after exposure, consider:

• Visceral larva migrans presentation (fever, eosinophilia, hepatosplenomegaly): Toxocara serology, complete blood count with differential 5
• Ocular symptoms: Ophthalmologic evaluation for toxoplasmosis or toxocariasis 5
• Neurologic symptoms: Consider neurotoxoplasmosis or neurotoxocariasis workup 5
• Diarrheal illness: Stool studies for Cryptosporidium, Salmonella, Campylobacter 1