INFECTIOUS DISEASES: E. cuniculi, myxomatosis, RHD and parasites

Encephalitozoon cuniculi Encephalitozoon cuniculi is a single-cell, microsporidial organism. Microsporidia are a diverse group of organisms and more than 1200 species have been identified. They parasitise a range of vertebrate and invertebrate hosts. Microsporidia lack mitochondria and rely on a host cell for energy. They produce large numbers of spores that contain a coiled polar tube. Classification of microsporidia within the animal kingdom has proved difficult. Many early papers describe microsporidia as protozoa but papers that are more recent classify them as atypical fungi. Chitin is present in the cell wall. There has been an upsurge of interest in microsporidia in recent years because several species can cause disease in humans, especially in people that are immunocompromised by HIV infection or anti-rejection drugs following organ transplantation. Medication to treat cancer can also be immunosuppressive. Encephalitozoon is only one genus of microsporidia and it contains several species, including Encephalitozoon cuniculi. The most common microsporidial infections in humans are due to Encephalitozoon bieneusi and Encephalitozoon intestinalis. Both species have been found worldwide, mainly in HIV-infected patients with chronic diarrhoea but also in immunocompetent persons with acute, self-limited diarrhoea. Disease due to Encephalitozoon cuniculi and Encephalitozoon hellem are rare but have been diagnosed in humans.