Distribution of Simuliids Larvae and Physio-chemical Parameters of Breeding sites along Contiguous Tributaries of an Onchocerciasis Hyper-endemic focus in Gashaka, Taraba State, Nigeria

Abstract

Taraba State, located in the north-eastern part of Nigeria harbours some of the hyper endemic onchocerciasis sites in the country. The  distribution of simuliids larvae along the river contiguous with these sites has been documented but unpublished. Larval sampling was  conducted along the tributaries adjoining the hyper-endemic focus in Gashaka Local Government Area of Taraba State, between  December 2006 and January 2007. This study therefore presents the distribution of simuliid species and physico-chemical parameters of  the breeding sites along the tributaries of the endemic foci in Gashaka LGAof Taraba State. The physico-chemical parameters of breeding  sites were measured using standardized equipment, and larvae of various Simulium species were collected, fixed in Carnoy’s solution and  subsequently identified in the laboratory. Eleven tributaries were examined, with only 3(25.0%) serving as breeding sites during the  collection period. A total of 552 simuliids larvae were identified; Simulium damnosum, 490 (86.96%); S. medusaeforme hargreavesi,  51(9.24%); S. colas belcouri, 11(1.99%); S. vorax, 7(1.27%) and S. bovis, 3(0.54%). S. damnosum were the most predominant, collected from  all breeding sites, with 95.95% (284/296) in Ngam Ngam, 100% (90/90) in Kam, and 63.86% (106/166) in Mayo Selbe. The physico- chemical parameters of the tributaries range from 6.6-6.9 for pH, 45- o 82µs/cm for conductivity, 140-157m/s for water velocity, 20-22 C  for temperature, 146-246m for river width, 185-455m for altitude and clear turbidity across the sampling sites. Larvae of S. damnosum, S.  medusaeforme, S. colas, S. 2 vorax, and S. bovis had strong positive correlations (r = 0.5-1.0) with pH and altitude parameters of breeding  sites. This study provides baseline data on the identity and abundance of simuliid larvae, which are useful for comparative assessments  with recent entomological surveys across breeding sites in the focus.