Factors Affecting Filarial Transmission by Simuliids

Simuliid blackflies (Diptera: Simuliidae) and ceratopogonid midges (Diptera: Ceratopogonidae) as vectors of Mansonella ozzardi (Nematoda: Onchocercidae) in northern Argentina

“…All the species cited in Yarzábal et al (1985) possess cibarial teeth, whereas S. exiguum at Finca Normenta does not. This would therefore suggest that this simuliid population is a poor host to M. ozzardi because of rapid formation of the peritrophic membrane or because of an inhibitor in the thoracic musculature as is seen in some simuliid species that transmit O. volvulus in Africa and Latin America (Shelley 1988(Shelley , 1994. Host capacity variations also occur at the level of cytospecies.…”

“…It has been shown by Shelley et al (1987) that S. oyapockense s.l. in the Brazilian Amazon is a relatively poor host to O. volvulus because of the damage caused by its cibarial teeth to microfilariae during ingestion, and that this was a major factor in determining vectorial competence in vector simuliid species in Latin America (Shelley 1988(Shelley , 1994. Generally, species with unarmed cibaria are more effective hosts to O. volvulus than those with armed cibaria and the same must be true for M. ozzardi.…”

“…Host capacity variations also occur at the level of cytospecies. S. exiguum is a species complex in which individual cytospecies show different capacities to act as hosts to O. volvulus in Ecuador (Shelley et al 1990) and in which some populations (Venezuela) are actually poor hosts (Shelley 1994).…”

Human onchocerciasis in Brazil: an overview

“…The ELISA used in this study for detection of O. volvulus cross-reacts with M. ozzardi and hence needs to be further refined before it can be reliably used where the two parasites are sympatric, such as in the Amazonia onchocerciasis focus. Identification problems between these two filarial species also occur in the larval stages found in the vectors (see review in Shelley, 1994 Equator degree to which microfilariae may occur in the head of partially fed flies in landing catches is probably low but is likely to be higher in species with a cibarial armature because microfilariae become trapped on the cibarial teeth.…”

“…Major conclusions were that the pattern of onchocerciasis endemicity is directly related to the simuliid species present. Of the numerous factors that affect onchocerciasis transmission in Latin America (reviewed by Shelley, 1994), the presence or absence of cibarial teeth and the compatibility of parasite to vector morphospecies or cytospecies have major effects on parasite transmission. The relevance of these factors to the epidemiology and control of onchocerciasis in the Americas are reviewed in Shelley (1988Shelley ( , 1991.…”