Protozoan Agents

Protozoa are microscopic organisms, usually single-celled and heterotrophic (using organic carbon as a source of energy), belonging to any of the major lineages of protists. All protozoans are eukaryotes and therefore possess a “true,” or membrane-bound, nucleus. They also are non-filamentous (in contrast to organisms such as moulds, a group of fungi, which have filaments called hyphae) and are confined to moist or aquatic habitats. Many are symbionts of other organisms, and some species are parasitic.

Cryptosporidium spp. - [Cat B] cause cryptosporidiosis which is a diarrheal and respiratory tract disease.  Cryptosporidia are protozoan, obligate intracellular parasites.There are more than twenty members of the genus. In humans the organisms most commonly are Cryptosporidium hominis and C. parvum. It is most commonly seen in children aged between 1 and 5 years. People with weak immune systems are likely to be more seriously affected. The most common symptom is mild to severe watery (commonly bloody) diarrhoea but symptoms can also include fever, abdominal cramps and vomiting. The fever is characteristically low-grade. The incubation period is typically 2 to 10 days but may be as long as 28 days. Symptoms may last as long as a month.