Isosporiasis
Pathogen:
Isospora belli, a parasite most commonly found in tropical and subtropical climates.
Sites of Infection:
Intestines.
Symptoms:
Watery, non-inflammatory diarrhea; abdominal cramping; and weight loss. These symptoms are chronically indistinguishable from those of cryptosporidiosis.
Diagnosis:
Fecal smear. Antibody tests are not available.
Treatment Results:
Oral TMP/SMX is effective against isosporiasis. Pape et al. successfully treated 32 AIDS patients with isosporiasis with TMP/SMX (one double-strength tablet PO four times daily). For maintenance, the patients were randomized to receive TMP/SMX (one double strength tablet three times weekly), sulfadoxine/pyrimethamine (500 mg/25 mg weekly), or placebo. One patient receiving TMP/SMX relapsed three weeks after initiation of maintenance. All others remained asymptomatic. 5/10 on placebo relapsed a mean of 1.5 months after randomization.
Weiss et al. successfully treated two AIDS patients unable to tolerate sulfonamides, for isosporiasis with pyrimethamine (50-75 mg PO qd) and leucovorin (10 mg PO qd); recurrence was prevented by maintenance treatment with pyrimethamine (25 mg PO qd) and leucovorin (5 mg PO qd).
REFERENCES:
Pape JW et al. Treatment and prophylaxis of isospora belli infection in patients with AIDS. NEJM 320:1044-7,1989.
Weiss LM et al. Isospora belli infection: treatment with pyrimethamine. Ann Int Med 109(6): 474-75, 1988.