Onchocerciasis in Ecuador: prevalence of infection on the Ecuador-Colombia border in the Province of Esmeraldas

The prevalence of onchocerciasis infection was determined in communities on 7 rivers located in the northern area of the canton San Lorenzo, province of Esmeraldas. Diagnosis of the infection was obtained by skin biopsies and recombinant-antigen based-serology. No evidence of infection was detected in 9 communities studied along the Rio Mataje, which forms the frontier between Ecuador and Colombia, nor in 10 adjacent communities located on 5 interior rivers. Evidence for Onchocerca volvulus infection was found in 4 communities on the Rio Tululvi with the following prevalence: La Boca (3,5 per cent by biopsy and 3,9 per cent by serology), Guayabal (9,1 per cent by both biopsy and serology), La Ceiva (51,5 per cent by biopsy and 53 per cent by serology), and Salidero (4 per cent by biopsy and 7,7 per cent by serology). A few individuals in these communities were seropositive for O. volvulus in the absence of detectable dermal microfilariae: these might harbor very light or prepatent infections. No clinical disease attributable to onchocerciasis was found. The infected communities will be included in the ivermectin-based National Control Program for the disease, with no evidence of the infection having extended north of the Ecuadorian-Colombian border.

Transmission of onchocerca volvulus by simulium damnosum S.L. in four villages in the Gorama Chiefdom; Kono district; Sierra Leone

Quantitative studies on the transmission of onchocerca volvulus; including monthly and annual biting densities; age composition; parity rates; infection and infective rates of the similium damnosum s.l. population; were carried out for a year in a tropical rain-forest zone in Sierra Leone. In all 19;432 s. damnosum s.l. female flies were acught and 8;755 dissected; of which 6.307 were parous. The annual biting rate (ABR) varied between 20;787 and 39;188; 5.4 per cent of all flies were infected with O. volvulus; 3.6 per cent carried infective larvae in the head capsule; with mean of 2.5 per fly. The annual transmission potential (ATP) varied between 1;138 and 2;081. The ATPs for Bunabu; Matama; Kangama and Moimandu villages were 2;081; 1;403; 1;138 and 1;498 respectively; with most of the infection occuring during the months of May and August. The prevalences of skin microfilariae (mf) in Bunabu; Matama; Kangama and Moimandu villages were 79.0 per cent; 51.3 per cent; 78.0 per cent and 80.0 per cent respectively