Onchocerciasis in Gilgel Ghibe River valley Southwest Ethiopia

Abstract

Objective: To determine the prevalence of onchocerciasis and the entomological transmission indices such as the parous rate and annual transmission potential (ATP). Setting: Gilgel Ghibe village, Gilgel Ghibe River Valley Southwest Ethiopia between April 1994 and March 1995. Subjects: Two hundred twenty eight subjects of the total 400 population in Gilgel Ghibe village were subjected to parasitological and clinical examinations. Method: Two skin snips per person were taken and examined for microfilariae of Onchocerca volvulus. Fly collections were done from dawn to dusk from human baits seated in pairs at four representative sites at the river bank and away from the river bank. Flies were dissected for parity and infections with O. volvulus larvae. Results: Among the 228 people examined, the prevalence of the disease was low (17%), being higher in males (19%) than in females (14%). The geometric mean of microfilarial density was 11.1 (range, 1-132) mf per skin snip. Itching followed by pigmentary changes were the most common clinical signs and symptoms. The predominant anthropophilic blackfly species was Simulium (Edwardsellum) damnosum s.l. The annual parous rate and ATP were 74.7% and 1669.5, respectively, being higher at the river bank than at sites further away suggesting a greater risk of infection by the river side. Conclusion:The low prevalence of onchocerciasis in Gilgel Ghibe area vis-a-vis the high ATP level could be due to the possible presence of bovine onchocerciasis in the area. Further studies employing molecular techniques are thus required to identify O. volvulus from other filariae in flies.

Parasitological and clinico-epidemiological features of onchocerciasis in West Wellega, Ethiopia

“…Adopting the endemic rates classification as defined by World Health Organization, these communities can be regarded as hyperendemic for onchocerciasis (WHO 1992). The prevalence observed in our study area was higher than the reports from some parts of the country (Adugna et al 1996;Taye et al 2000) even though other reports have previously documented a high prevalence among different ethnic groups of western Ethiopia. For instance, Jira (1993) reported a high prevalence of onchocerciasis (81.0%) among Nilotic people living in Blue Nile Valley of Western Ethiopia.…”

“…Relatively lower level of CMFL (13.6) has previously been reported from nearby region of southwestern Ethiopia (Taye et al 2000). The higher magnitude of CMFL observed in our study area might be due to the fact that CDTI was not in place at the time of the survey, notwithstanding the fact that self-treatment was commonplace.…”

“…This disparity between the NCR and MFCR is much wider than previously reported in other countries (Remme et al 1986;Mace et al 1997;Ngoumou et al 1994), and may be associated with the variability in parasite strains' virulence, differences of vectors in their biting proclivities, altered host factors associated with genetic susceptibility or host immunity, and history of co-infection by other parasites (McCarthy et al 1994). A study from southwest Ethiopia showed even the complete absence of onchocercal nodules among study subjects whilst microscopic examination of the skin snips demonstrated a prevalence of 17.1% (Taye et al 2000). Additionally Adugna et al (1996) has reported disproportionally low rate of palpable NCR (1.7%) and microfilaridermia prevalence of 15.3% (Adugna et al 1996).…”

“…In Ethiopia, several studies were previously undertaken in an attempt to determine the prevalence of onchocerciasis in different regions of the country. Consequently, various estimates of prevalence of infection ranging from low to high rates were reported (Adugna et al 1996;Jira 1993;Taye et al 2000;Hailu et al 2002). The prevalence of onchocerciasis in Anfilo District during our survey was 74.8%.…”

Onchocerciasis in Tigray

“…Onchocerciasis, and other neglected diseases, affect inhabitants of developing countries who are too poor to pay for treatment. Ethiopia is one of the countries involved in the African Programme for Onchocerciasis Control (APOC), but the literature concerning onchocerciasis relates to the north‐western and south‐western regions of the country 1,5–8 . The filariacidal drug ivermectin, recognized as a mainstay of treatment for onchocerciasis, and utilized in mass distribution by APOC, is not available in the capital of the northern region of Ethiopia.…”