Hendy, Adam ORCID: 0000-0001-8082-6352, Krit, Meryam, Pfarr, Kenneth, Laemmer, Christine, De Witte, Jacobus, Nwane, Philippe, Kamgno, Joseph, Nana-Djeunga, Hugues C., Boussinesq, Michel, Dujardin, Jean-Claude, Post, Rory, Colebunders, Robert, O'Neill, Sarah, Enyong, Peter and Njamnshi, Alfred K. (2021). Onchocerca volvulus transmission in the Mbam valley of Cameroon following 16 years of annual community-directed treatment with ivermectin, and the description of a new cytotype of Simulium squamosum. Parasites Vectors, 14 (1). LONDON: BMC. ISSN 1756-3305

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Abstract

Background: The onchocerciasis focus surrounding the lower Mbam and Sanaga rivers, where Onchocerca volvulus is transmitted by Simulium damnosum s.l. (Diptera: Simuliidae), was historically the largest in the southern regions of Cameroon. Annual community- directed treatment with ivermectin (CDTI) has been taking place since 2000, but recent studies have shown that new infections are occurring in children. We aimed to investigate blackfly biting and O. volvulus transmission rates along the lower Mbam river 16 years after the formal onset of annual CDTI. Methods: Black flies were collected for three consecutive days each month between July 2016 and June 2017 at two riverside villages and two inland sites situated 4.9 km and 7.9 km from the riverside. Specimens collected at each site were dissected on one of the three collection days each month to estimate parity rates and O. volvulus infection rates, while the remaining samples were preserved for pool screening. Results: In total, 93,573 S. damnosum s.l. black flies were recorded biting humans and 9281 were dissected. Annual biting rates of up to 606,370 were estimated at the riverside, decreasing to 20,540 at 7.9 km, while, based on dissections, annual transmission potentials of up to 4488 were estimated at the riverside, decreasing to 102 and 0 at 4.9 km and 7.9 km, respectively. However, pool screening showed evidence of infection in black flies at the furthest distance from the river. Results of both methods demonstrated the percentage of infective flies to be relatively low (0.100.36%), but above the WHO threshold for interruption of transmission. In addition, a small number of larvae collected during the dry season revealed the presence of Simulium squamosum E. This is the first time S. squamosum E has been found east of Lake Volta in Ghana, but our material was chromosomally distinctive, and we call it S. squamosum E2. Conclusions: Relatively low O. volvulus infection rates appear to be offset by extremely high densities of biting black flies which are sustaining transmission along the banks of the lower Mbam river.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Hendy, AdamUNSPECIFIEDorcid.org/0000-0001-8082-6352UNSPECIFIED
Krit, MeryamUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Pfarr, KennethUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Laemmer, ChristineUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
De Witte, JacobusUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Nwane, PhilippeUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Kamgno, JosephUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Nana-Djeunga, Hugues C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Boussinesq, MichelUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Dujardin, Jean-ClaudeUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Post, RoryUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Colebunders, RobertUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
O'Neill, SarahUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Enyong, PeterUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Njamnshi, Alfred K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-602606
DOI: 10.1186/s13071-021-05072-y
Journal or Publication Title: Parasites Vectors
Volume: 14
Number: 1
Date: 2021
Publisher: BMC
Place of Publication: LONDON
ISSN: 1756-3305
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
DAMNOSUM COMPLEX DIPTERA; CHROMOSOMAL IDENTIFICATION; BLACK FLIES; EDWARDSELLUM; CYTOTAXONOMY; EPILEPSY; MEMBERS; VECTOR; FOREST; GUIDEMultiple languages
Parasitology; Tropical MedicineMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/60260

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