A rat model for combined Trypanosoma cruzi and Pneumocystis carinii infection.

Dexamethasone treated rats inoculated with Trypanosoma cruzi developed acute parasitemia. In addition, these animals concomitantly developed severe Pneumocystis carinii pneumonia (PCP) and died after 4 weeks of immunosuppression (100%). However, immunocompetent (untreated) rats inoculated with T. cruzi did not acquire P. carinii and recovered from T. cruzi infection. Rats immunosuppressed, but not inoculated with T. cruzi, developed only PCP and died 5-6 weeks later (93%). In contrast, immunocompetent or immunocompromised IRC mice infected with T. cruzi all died of acute parasitemia in only 8-12 days with no detectable PCP infection. In conclusion, rats immunosuppressed and T. cruzi inoculated can serve as a MOPPS model for a single drug evaluation. In addition, T. cruzi infection independently does not provoke P. carinii pneumonia in this model. Finally, patients with Chagas' disease treated with corticosteroids may be at risk for PCP and should be considered for chemoprophylaxis.