Epidemiological Mapping of Onchocerciasis Hypoendemic Area of North Achefer District, Amhara Regional State, Ethiopia

Background

Onchocerciasis (river blindness) is caused by a filarial nematode worm called Onchocerca volvulus encapsulated in nodules under skin. The adult worm logged itself in nodules of cutaneous skin producing thousands of microfilariae per-day those migrating under the dermis of the skin causing cutaneous and eye disease. Ethiopia is one of countries with a high disease burden of onchocerciasis in Africa. Epidemiological mapping of onchocerciasis in hypoendemic area is a first step in elimination programme and to identify intervention eligible areas. Many districts are uncertain about onchocerciasis transmission; in identifying intervention eligible areas especially North Achefer is located adjacent to onchocerciasis endemic district (Alefa) which receiving semi-annual MDA, and its transmission status of the district is not well studied.

Objective

The purpose of this study was to assess the epidemiological status of onchocerciasis in the hypoendemic area of the North Achefer district of the Amhara Regional State.

Methodology

Community-based cross-sectional study design conducted from July to August 2021. Parasitological, immunological and serological (ELISA and RDT) data were collected from the field and for central laboratory. Statistical analysis was conducted using Epi-info software version 7, transported to SPSS software version 26. Descriptive analysis was conducted and presented with frequencies and percentages. The association between dependent and independent variables was analyzed using bivariate logistic regression and variables those with a P-value <0.05% was considered statistically significant.

Result

A total of 264 participants enrolled in the study out of which 56.4% were male, with mean age of 28 years. The microscopic examination of skin snip was no microfilariae positive cases, whereas, 3% and 9.1% positive were recorded for Ov16 RDT and Ov16 ELISA test, respectively. Onchocerciasis morbidity indicators were 6 (2.3%), 12 (4.5%), and 9 (3.4%) palpable nodule, skin discoloration, and skin depigmentation respectively. Age, gender, village type, and distance from the river were independent variables that had a significant association with positivity for Ov16 ELISA test.

Conclusion

A high prevalence of onchocerciasis exposure which is above the WHO recommended threshold (5%) by Ov16 ELISA assay was observed. Distance from the river, village type, age, and gender had significantly associated with Ov16 ELISA test. Therefore, onchocerciasis elimination intervention in North Achefer is recommended to be implemented. Increasing the sample size and including molecular (i.e. PCR) and entomological technique best recommended to maximize the positivity of the disease and to insure the exact status of the disease in the district respectively.