Cryptosporidium species in HIV-infected individuals in India: an overview

Cryptosporidium spp. are a major cause of diarrhoea in developing countries mainly affecting children and HIV-infected individuals with low CD4 counts. The infection is self-limiting in immunocompetent hosts, but can be severe and persistent in the immunocompromised and malnourished. Treatment is less than optimal and no vaccine is currently available. In the West, the ability of this protozoan parasite to survive in the environment for a long duration and cause explosive outbreaks in susceptible populations has led to its inclusion as a category B pathogen for biodefence. Reports on the prevalence of cryptosporidial diarrhoea in HIV-infected adults from different parts of India from the mid-1990s have ranged from 0.7% to 83% in symptomatic and from 1.4% to 57% in asymptomatic individuals, with very high rates in both groups in the northeastern states. Several studies in India have also documented a correlation between CD4 count <200 cells/cmm and symptomatic cryptosporidiosis. Among children with diarrhoea, the prevalence of cryptosporidiosis has ranged from 1.1% to 18.9%. Other susceptible populations studied include patients with malignancies and transplant recipients. Molecular tools have permitted speciation and genotyping, leading to more detailed epidemiological studies than were possible with microscopy alone. Using these methods, the common cryptosporidial species reported to affect both HIV-infected adults and children in India are C. hominis and C. parvum. With easier access to antiretroviral therapy for Indian patients with HIV, the effect on the prevalence of cryptosporidiosis and aetiology of HIV-related diarrhoea remains to be seen. Therefore, data from different parts of India form a necessary baseline against which the effect of antiretroviral therapy can be evaluated.