1.1 Background of the study
Microsporidia are single-celled, obligate intracellular parasites that were recently reclassified from protozoa to fungi. Microsporidia are a group of intracellular parasites which have attracted the interest of parasitologists for over 100 years. The first species, Nosemabombycis, was discovered in the middle of the 19th century as the cause of silkworm disease (i.e., pepper disease, pebrine disease), which nearly destroyed the silkworm industry in Southern Europe (Didier,2005; Franzen,2008).More than 1,400 microsporidian species have been described in both invertebrate and vertebrate hosts. Only eight genera and 15 species of microsporidia have been associated with human infections.
The first report on human microsporidia infection was in 1959 and described the case of a 9-year-old Japanese boy who presented with disseminated microsporidiosis associated with fever, headache, vomiting, and spastic convulsions, (Matsubayash et al.,1959). Interest in this group of parasites started with the development of the AIDS pandemic around the world in 1980’s. In 1985, a new species Enterocytozoonbieneusi was found in an HIV-infected patient. Since then, species of microsporidia have been recognized worldwide as etiologic agents of opportunistic infections. The clinical course of microsporidiosis depends on the immune status of the patient and the site of infection. The groups at risk constitute people with HIV/AIDS, organ transplant recipients being treated with immunosuppressive drugs, travellers, children and the elderly, (Didier, 2000; Garcia, 2002;Rabodonirina, 2003; Wichro, 2005; Dworkin, 2007; Galvan, 2011).
Two microsporodia Enterocytozoon bieneusi and Encephalitozoon Intestinalis have been identified as possible causes of diarrhoeal illness in HIV-infected patients, (Moura et al.,1993; Kotler, 1995). Over 40 million people are living with HIV/AIDS, the majority (more than 25 million) of whom live in sub-Saharan Africa. Up to 2.4 million deaths were recorded worldwide in 2005, (Akinbo et al., 2009).
People in the advanced stages of HIV infection are vulnerable to secondary infections and malignancies that are generally termed as opportunistic infections as they take the advantage of the opportunity offered by a weakened immune system, (Saidu, et al.,2009). In HIV/AIDS positive patients, the most clinical manifestation is chronic diarrhoea and wasting due to enteric infection, (UNIADS 1998).This parasite is commonly observed in HIV-infected patients with CD4 Lymphocytes count of less than 50cells/mm3 who complain of chronic diarrhoea, nausea, malabsorption and severe weight loss but asymptomatic infection have also been reported in immune competent persons, (Sak et al., 2011).