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Does onchocerciasis transmission take place in hypoendemic areas? a study from the North Region of Cameroon
Author(s) -
Katabarwa Moses N.,
Eyamba Albert,
Chouaibou Mouhamadou,
Enyong Peter,
Kuété Thomas,
Yaya Souleymanou,
Yougouda Abdoulaye,
Baldiagaï Jean,
Madi Kambaba,
Andze Gervais Ondobo,
Richards Frank
Publication year - 2010
Publication title -
tropical medicine and international health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.056
H-Index - 114
eISSN - 1365-3156
pISSN - 1360-2276
DOI - 10.1111/j.1365-3156.2010.02501.x
Subject(s) - onchocerciasis , geography , transmission (telecommunications) , environmental protection , socioeconomics , medicine , immunology , telecommunications , economics , engineering
Summary Objective Community‐directed treatment with ivermectin (CDTI) for onchocerciasis control is targeted to meso and hyperendemic areas in Africa. Below the threshold, communities are considered hypoendemic and, mass treatment is not recommended. As policy begins to shift from control to elimination, the role of hypoendemic areas in maintaining Onchocerca volvulus needs to be re‐examined. The study determined whether independent transmission occurs in a hypoendemic area in the North region of Cameroon. Methods Ten ‘high risk’ communities along the River Mayo Douka system in Ngong Health District, at least 20 km from the nearest CDTI program were studied. Six hundred and forty‐nine adults (over 20 years of age) and 561 children (under 10 years) were examined for nodules and microfilaria. A subsample of 334 adults was examined for onchocercal ocular morbidity. Simulium flies from 4 collection points were captured over 3 months annually for 2 years and dissected for larval stages of O. volvulus. Results Nodule and microfilariae (mf) prevalence among adults was 12.20% and 2.91%, and 9.2% and 0.48% among children, respectively. Blindness because of onchocerciasis was insignificant, although low rates of chronic onchocercal ocular disease (<2%) were observed. Four (0.16 percent) of 255 flies collected in 2008 were infected with L3 larval stage, and 1 black fly of 39 collected in 2009 had two L2 larval stage morphologically consistent with O. volvulus . Conclusion Ngong is a ‘hypoendemic’ focus with likely low grade indigenous transmission in isolation from meso/hyperendemic areas. Consequently, transmission from hypoendemic areas could contribute to rapid disease recrudescence in the post‐treatment phase of adjacent former meso and hyperendemic areas.