Mosquito host choices on livestock amplifiers of Rift Valley fever virus in Kenya

Authors

David P. Tchouassi, International Centre of Insect Physiology and EcologyFollow
Robinson O. Okiro, International Centre of Insect Physiology and Ecology
Rosemary Sang, International Centre of Insect Physiology and Ecology & Centre for Virus Research, Kenya Medical 3 ResearchInstitute(KEMRI)
Lee W. Cohnstaedt, USDA-ARS Arthropod-Borne Animal Disease Research Unit, Center for Grain and Animal Health Research
D. Scott McVey, USDA-ARS Arthropod-Borne Animal Disease Research Unit, Center for Grain and Animal Health ResearchFollow
Baldwyn Torto, International Centre of Insect Physiology and EcologyFollow

Date of this Version

2016

Citation

Tchouassi et al. Parasites & Vectors (2016) 9:184 DOI 10.1186/s13071-016-1473-x

Comments

2016 Tchouassi et al.

Abstract

Background: Animal hosts may vary in their attraction and acceptability as components of the host location process for assessing preference, and biting rates of vectors and risk of exposure to pathogens. However, these parameters remain poorly understood for mosquito vectors of the Rift Valley fever (RVF), an arboviral disease, and for a community of mosquitoes.

Methods: Using three known livestock amplifiers of RVF virus including sheep, goat and cattle as bait in enclosure traps, we investigated the host-feeding patterns for a community of mosquitoes in Naivasha, an endemic area of Rift Valley fever (RVF), in a longitudinal study for six months (June–November 2015). We estimated the incidence rate ratios (IRR) where mosquitoes chose cow over the other livestock hosts by comparing their attraction (total number collected) and engorgement rate (proportion freshly blood-fed) on these hosts.

Results: Overall, significant differences were observed in host preference parameters for attraction (F2,15 = 4.1314, P = 0.037) and engorgement (F2,15 = 6.24, P = 0.01) with cow consistently attracting about 3-fold as many mosquitoes as those engorged on sheep (attraction: IRR = 2.9, 95 % CI 1.24–7.96; engorgement: IRR = 3.2, 95 % CI = 1.38–7.38) or goat (attraction: IRR = 2.7, 95 % CI 1.18–7.16; engorgement: IRR = 3.28, 95 % CI 1.47–7.53). However, there was no difference between the attraction elicited by sheep and goat (IRR = 1.08; 95 % CI 0.35–3.33 or engorgement rate (IRR = 0.96, 95 % CI 0.36–2.57).

Conclusion: Despite the overall attractive pattern to feed preferentially on cows, the engorgement rate was clearly independent of the number attracted for certain mosquito species, notably among the flood water Aedes spp., largely incriminated previously as primary vectors of RVF. Our findings suggest that insecticide treated cattle (ITC) can be exploited in enclosure traps as contact bait in the monitoring and control of disease-causing mosquitoes in RVF endemic areas.