熱帯病と公衆衛生ジャーナル

概要

Onchocerciasis Prevalence and Transmission Potential of Simulium spp. in Three Areas of the Northern Regions of Cameroon

Sanda Amadou, Djafsia Boursou, Pierre Saotoing, Dieudonné Ndjonka*

Background: Onchocerciasis is an infection caused by Onchocerca volvulus: A filarial nematode transmitted by Simulium spp. More than 99% of infected people live in 30 countries in sub-Saharan Africa, 37 million people are carriers of Onchocerca volvulus in Central and East Africa, and 800,000 blinds people are recorded. Villages in northern Cameroon had more than 80% microfilaria index in 1991 with bilateral blindness rates 1.7% to 4.0%.

Methods: Three villages have been selected to study: Lagaye in the district of Touboro, Mandjiri in the department of Vina (Adamawa), and Mayo-Salah in Mayo Rey Department. Concerning the parasitological research, the persons to be examined have been gathered by sex (female and male) and age group. Three age groups were concerned: 5 to 9 years, 10 to 15 years, and beyond 16 years. Using a vaccine style and a razor blade, a 2 mm fragment of skin was removed from the scapula, iliac crest, and calf. The place for removing was cleaned with alcohol (95°C). The skin was placed in a tube containing 2 mL of physiological water (NaCl, 9%) for 24 hours then centrifuged. The pellet was collected for direct examination and stained with the Giemsa, then observed on a binocular microscope. Entomologically, an adult of black flies was captured on human bait and dissected under the entomological microscope. Their physiological age has been determinate. The blackfly was dilacerated to search all the stages of filariae larvae.

Results: Seven (07) out of 165 skin samples were found positive, giving an overall parasite prevalence of 4.24%. According to the distribution of the prevalence by sex, it appears that the male was the most infected (6/165) 3.64%, with (1/165) 0.60% for females. Entomologically, 11,695 black flies were captured; only 4,065 females were dissected (34.75%). Of these females, 2,514 (61.84%) were parous exhibiting structures with semi-clear or clear Malpighi tubes, 1,418 (34.88%) nulliparous presenting opaque Malpighi tubes. As regards parasitological research only 229 (5.63%) blackflies were infected by Onchocerca volvulus all confounded forms among which 125 (3.07%) carrying infected stage (L3).

Conclusion: At the end of our investigation, the results revealed that there are still vectors of onchocerciasis and the transmission of this human parasite in the regions is still ongoing.