Mansonelliasis - Diagnosis

Diagnosis

Examination of blood samples will allow identification of microfilariae of M. perstans, and M. ozzardi based (3). This diagnosis can be made on the basis of the morphology of the nuclei distribution in the tails of the microfilariae (5, 8). The blood sample can be a thick smear, stained with Giemsa or hematoxylin and eosin (6, 3). 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 (3).

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 (3). 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 (4).