Evidence for Suppression of Onchocerciasis Transmission in Bioko Island, Equatorial Guinea.

Onchocerciasis or "river blindness" is a chronic parasitic neglected tropical disease which is endemic both in mainland and insular Equatorial Guinea. We aim to estimate the current epidemiological situation of onchocerciasis in Bioko Island after vector elimination in 2005 and more than sixteen years of Community Directed Treatment with Ivermectin (CDTI) by using molecular and serological approaches for onchocerciasis diagnosis. A community-based cross-sectional study was carried out in Bioko Island from mid-January to mid-February 2014. A total of 544 study participants were recruited. A complete dermatological examination was performed and three skin snips were performed in every participant for parasitological and molecular assessments. Blood spots were also taken for determination of Ov16 IgG4 antibodies trough an "in-house" ELISA assay. Overall, we found 15 out of 522 individuals suffering any onchocerciasis specific cutaneous lesions and 16 out of 528 (3.0%) with onchocercal nodules in the skin. Nodules were significantly associated with age, being more common in subjects older than 10 years than in younger people (3.9% vs. 0%, p = 0.029). Regarding the onchocerciasis laboratory assessment, no positive parasitological test for microfilaria detection was found in the skin snips. The calculated seroprevalence through IgG4 serology was 7.9%. No children less than 10 years old were found to be positive for this test. Only one case was positive for Onchocerca volvulus (O. volvulus) after skin PCR. The present study points out that the on-going mass ivermectin treatment has been effective in reducing the prevalence of onchocerciasis and corroborates the interruption of transmission in Bioko Island. To our knowledge, this is the first time that accurate information through molecular and serological techniques is generated to estimate the onchocerciasis prevalence in this zone. Sustained support from the national program and appropriate communication and health education strategies to reinforce participation in CDTI activities are essential to ensure progress towards onchocerciasis elimination in the country.

A pilot study on the prevalenceof loiasis in Equatorial Guineausing an accurate Nested PCR

Background: In the last years loiasis has emerged as a public health problem in areas where Loa loa is co-endemic with Onchocerca volvulus, Wuchereria bancrofti and other filarial parasites. The objective of this work was to carried out a preliminary field study on the prevalence ofloiasis in Equatorial Guinea. Methods: The study design was carried out in three villages situated in the continental region and the insular region from Equatorial Guinea. A total of 236 human blood samples were obtained from individuals living in the continental region (n=142) and on the island of Bioko(n=96). Blood samples were diagnosed by leucoconcentration and microscopy examination formicrofilariae of L. loa and other filarial species. The molecular diagnosis was carried out by theL. loa specific nested PCR. Results: The study results shown a 22.8% of loiasis prevalence by microscopy observation, whereas the nested PCR revealed a prevalence of 76.4% in the continental region. In the 94samples obtained from individuals from the island of Bioko, loiasis was not detected either bymicroscopy analysis or by nested PCR. Conclusions: The nested PCR used in this work showed itself to be an accurate technique that detects the presence of L. loa DNA and it could be a useful complementary tool in ascertaining more precise estimates of the prevalence of loiasis in Equatorial Guinea (AU)

Fundamentos: En los últimos años la loasis se ha convertido en un grave problema de Salud Pública en áreas donde Loa loa es co-endémica con Onchocerca volvulus, Wuchereriabancrofti y otras filarias. El objetivo de este trabajo fue llevar a cabo un estudio preliminar de la prevalencia de loasis en Guinea Ecuatorial. Método: El diseño del estudio se llevo a cabo en tres poblaciones de la región continental yen la región insular de Guinea Ecuatorial. Se obtuvieron un total de 236 muestras de sangre procedentes de individuos de la región continental (n=142) y de la isla de Bioko (n=96). Las muestras fueron diagnosticadas por leuco concentración y examen microscópico de Loa loa y otras especies de filarias. El diagnóstico molecular se llevó a cabo mediante una nested PCR específica para Loa loa. Resultados: El resultado del estudio reveló una prevalencia de loasis del 22,8 % mediante diagnóstico microscópico y del 76,4% mediante nested PCR en la región continental. Loa loano fue detectada ni por análisis microscópico ni por nested PCR en las 94 muestras obtenidas de individuos de la Isla de Bioko. Conclusiones: La nested PCR utilizada en el trabajo y optimizada en nuestro laboratorio, es un método sensible que permite la detección de ADN de Loa loa y podría ser una herramienta complementaría útil en una evaluación más precisa de la prevalencia de loasis en Guinea Ecuatorial (AU)