THE IMPACT OF SIBLING SPECIATION IN SIMULIUM DAMNOSUM COMPLEX ON CURRENT ONCHOCERCIASIS CONTROL EFFORTS

Human onchocerciasis is a debilitating tropical infection that can result in blindness and severe skin disease. Despite the fact that the National Onchocerciasis Control Programme (NOCP) has been highly successful, at least from a public health perspective (in terms of significant reduction in morbidity), there still remains the problem of persistent transmission in some hyper endemic areas as opposed to what is obtainable in the Americas that ran a similar programme (where interruption of transmission has been achieved). This paper, reviewed the current strategies used in the control of onchocerciasis and highlighted a cryptic factor decimating the efforts employed against the disease; culminating in an extraordinary propensity of Simulium damnosum complex to exhibit sibling speciation and the attendant poor understanding of this phenomenon in relation to disease epidemiology. The review revealed that, poor knowledge of the role of sibling species in disease transmission could be contributing directly to the persistence in transmission seen in some endemic foci despite some control interventions, as this has not been seen in the Americas where a fair knowledge of the role of different sibling species has been reported. It is recommended that any control effort should take into account the possible varied roles of different sibling species in disease transmission. This will involve proper identification of vectors at cytotaxonomic and molecular levels, since sibling species are morphologically similar but reproductively isolated, rendering morphormetrics relatively irrelevant.