Procedure for Handling and Storage of Onchocerca volvulus Microfilariae Obtained from Skin Snips for Downstream Genetic Work

WHO and endemic countries target elimination of transmission of Onchocerca volvulus, the parasite causing onchocerciasis. Population genetic analysis of O. volvulus may provide data to improve the evidence base for decisions on when, where, and for how long to deploy which interventions and post-intervention surveillance to achieve elimination. Development of necessary methods and tools requires parasites suitable for genetic analysis. Based on our experience with microfilariae obtained from different collaborators, we developed a microfilariae transfer procedure for large-scale studies in the Democratic Republic of Congo (DRC) comparing safety and efficacy of ivermectin, the mainstay of current onchocerciasis elimination strategies, and moxidectin, a new drug. This procedure is designed to increase the percentage of microfilariae in skin snips suitable for genetic analysis, improve assignment to metadata, and minimize time and materials needed by the researchers collecting the microfilariae. Among 664 microfilariae from South Sudan, 35.7% and 39.5% failed the mitochondrial and nuclear qPCR assay. Among the 576 microfilariae from DRC, 16.0% and 16.7% failed these assays, respectively. This difference may not only be related to the microfilariae transfer procedure but also to other factors, notably the ethanol concentration in the tubes in which microfilariae were stored (64% vs. ≥75%).

Validation of the rapid assessment procedure for loiasis (RAPLOA) in the Democratic Republic of Congo

BACKGROUND

A simple method called RAPLOA, to rapidly assess what proportion of people in a community are infected with L. loa and hence which communities are at high risk of severe adverse reactions following ivermectin treatment, was developed in Cameroon and Nigeria. The method needed further validation in other geographical and cultural contexts before its application in all endemic countries. The present study was designed to validate RAPLOA in two regions in the North East and South West of the Democratic Republic of Congo.

METHODS

In each study region, villages were selected from different bio-ecological zones in order to cover a wide range of loiasis endemicity. In each selected community, 80 people above the age of 15 years were interviewed for a history of eye worm (migration of adult L. loa under the conjunctiva of the eye) and parasitologically examined for the presence and intensity of L. loa infection. In total, 8100 individuals from 99 villages were enrolled into the study.

RESULTS

The results confirmed the findings of the original RAPLOA study: i) the eye worm phenomenon was well-known in all endemic areas, ii) there was a clear relationship between the prevalence of eye worm history and the prevalence and intensity of L. loa microfilaraemia, and iii) using a threshold of 40%, the prevalence of eye worm history was a sensitive and specific indicator of high-risk communities.

CONCLUSION

Following this successful validation, RAPLOA was recommended for the assessment of loiasis endemicity in areas targeted for ivermectin treatment by lymphatic filariasis and onchocerciasis control programmes.

Conjunctival rhinosporidiosis. Report of three cases from Zaire

The authors report three cases of conjunctival rhinosporidiosis from Zaire, two of which are believed to be the first documented in the northeastern part of the country. All patients were males. Two patients were very young children, respectively 5 and 6 years old. The third patient was a 35-year-old man. The diagnosis was based on histopathology which revealed the characteristic features of Rhinosporidium seeberi. Total excision was the elective treatment. The disease recurred eleven months later in one case, probably from local dissemination of the parasite during surgery.

Ocular ulcerative herpes following measles in Kinshasa, Zaire

Eight cases of ocular ulcerative herpes following measles are reported. The clinical features are characterized by dendritic corneal ulcer (6 cases) and ulcero-erosive blepharitis associated with corneal ulcer (2 cases). Bacteriologic examination disclosed Pseudomonas aeruginosas in 2 cases. The serum level of retinol, RBP, prealbumin and albumin were generally diminished in cases of dendritic corneal ulcer. These data are discussed in relation to the onset and severity of ocular ulcerative herpes associated with measles.