unsheathed and non-periodic (sub-periodic in M. perstans) microfilariae that reach the blood stream. A midge or black fly ingests microfilariae during a blood meal. After ingestion, the microfilariae migrate from the midgut through the hemocoel to the thoracic muscles of the arthropod. There the microfilariae develop into first-stage larvae and later into third-stage infective larvae. The third-stage infective larvae migrate to the arthropod’s proboscis where they can then infect another human when the midge or blackfly takes a blood meal. Asymptomatic humans serve as a significant reservoir for the disease. Little is known about other reservoirs of the disease. Pathogenesis Mansonelliasis infection has been considered a minor filariasis, remaining asymptomatic in most infected subjects. Larvae develop in the subject and migrate to their respective regions in the skin or body cavities. It is likely that aside from being caused by the worm itself, some of the pathological changes observed are induced by the immune response to the infection leading to some of the various symptoms mentioned above. However, Mansonelliasis is little studied compared to other forms of filariasis so there is not as much information known regarding its specific pathogenesis. Diagnosis Examination of blood samples will allow identification of microfilariae of M. perstans, and M. ozzardi based. This diagnosis can be made on the basis of the morphology of the nuclei distribution in the tails of the microfilariae. The blood sample can be a thick smear, stained with Giemsa or hematoxylin and eosin. For increased sensitivity, concentration techniques can be used. These include centrifugation of the blood sample lyzed in 2% formalin (Knott's technique), or filtration through a Nucleopore membrane. Examination of skin snips will identify microfilariae of Onchocerca volvulus and M. streptocerca. Skin snips can be obtained using a corneal-scleral punch, or more simply a scalpel and needle. It is important that the sample be allowed to incubate for 30 minutes to 2 hours in saline or culture medium and then examined. This allows for the microfilariae that would have been in the tissue to migrate to the liquid phase of the specimen. Additionally, to differentiate the skin-dwelling filariae M. streptocerca and Onchocerca volvulus, a nested polymerase chain reaction (PCR) assay was developed using small amounts of parasite material present in skin biopsies. Prevention Prevention can be partially achieved through limiting contact with vectors through the use of DEET and other repellents, but due to the predominantly relatively mild