Clinical Management

Similar to C. parvum infection, the cornerstone of management is maintaining adequate hydration orally or, if clinically indicated, parenterally in I. belli infection. However, unlike C. parvum

Fig. 6.4 Acid-fast stain of stool containing Cryptosporidium parvum, Cyclospora cayetanensis and Isospora belli. This figure illustrates the morphology and size differences between the oocysts of C. parvum (~5 ^m, left panel), C. cayetanensis (~8-10 ^m, middle panel) and I. belli 10-19 x 20-30 ^m, right panel). Magnification, x 400

Fig. 6.4 Acid-fast stain of stool containing Cryptosporidium parvum, Cyclospora cayetanensis and Isospora belli. This figure illustrates the morphology and size differences between the oocysts of C. parvum (~5 ^m, left panel), C. cayetanensis (~8-10 ^m, middle panel) and I. belli 10-19 x 20-30 ^m, right panel). Magnification, x 400

infection, I. belli infection is rapidly responsive to appropriate antimicrobial therapy, as was first reported by Trier et al. (1974). The drug of choice is trimethoprim-sulfamethoxazole. Treatment with trimethoprim-sulfamethoxazole leads to resolution of diarrhea on average in 2 days, with a range of 1-6 days even in immuno-compromised hosts (including AIDS patients), and is associated with the disappearance of fecal oocysts (DeHovitz et al., 1986; Pape et al., 1989; Verdier et al., 2000; Westerman and Christensen, 1979). Although more intensive regimens were originally studied (DeHovitz et al., 1986; Pape et al., 1989), the infection appears to respond promptly in AIDS patients to trimethoprim-sulfamethoxazole 160mg/800mg twice daily for 7 days (Verdier et al., 2000). Since approximately 50% of AIDS patients have been reported to relapse after a mean of 8 weeks (range 2-20 weeks) once therapy is discontinued (DeHovitz et al., 1986), subsequent suppressive therapy with trimethoprim-sulfamethoxazole 160 mg/800 mg three times a week is suggested for AIDS patients and possibly other persistently immunocompromised hosts (Verdier et al., 2000). Of note, however, relapses respond promptly to reinstitution of treatment. A recent study suggests that ciprofloxacin (500 mg twice daily for 7 days) may be an acceptable alternative in patients who do not tolerate trimethoprim-sulfamethoxazole (Verdier et al., 2000). Anecdoctal reports suggest that I. belli may respond to treatment with pyrimethamine and sulfadiazine, sulfadoxine-pyrimethamine (Fansidar®) or macrolides such as roxithromycin (Musey et al., 1988; Trier et al., 1974; Weiss et al., 1988).

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