Posted by Vector and Vector-borne Disease Committee
November 1, 2022
Host selection and forage ratio in West Nile virus–transmitting Culex mosquitoes: Challenges and knowledge gaps. 2022. PLoS Negl Trop Dis 16(10): e0010819. https://doi.org/10.1371/journal.pntd.0010819
Riccetti N, Fasano A, Ferraccioli F, Gomez-Ramirez J, Stilianakis NI
European Commission, Joint Research Centre (JRC), Ispra (VA), Italy, Department of Biometry and Epidemiology, University of Erlangen-Nuremberg, Erlangen, Germany
Author’s Abstract [Shortened]
Background. Whereas mosquitoes’ intrinsic characteristics cause them to favour certain hosts (host preference), absolute selection is impossible in natural settings. Conversely, the selection carried out among available hosts and influenced from hosts’ availability and other ecological/environmental factors is defined as host selection.
Methodology/Principal findings. In July 2022, we searched PubMed database for original articles exploring host selection among WNV-transmitting Culex mosquitoes, the main WNV vector. We considered only original field studies estimating and reporting forage ratio. This index results from the ratio between the proportion of blood meals taken by mosquitoes on potential host species and the hosts’ relative abundance. From the originally retrieved 585 articles, 9 matched the inclusion criteria and were included in this review. All but one of the included studies were conducted in the Americas, six in the United States, and one each in Mexico and Colombia. The remaining study was conducted in Italy. American Robin, Northern Cardinal, and House Finch were the most significantly preferred birds in the Americas, Common Blackbird in Italy.
Conclusions/Significance. Although ornithophilic, all observed WNV-transmitting mosquitoes presented opportunistic feeding behaviour. All the observed species showed potential to act as bridges for zoonotic diseases, feeding also on humans. All the observed mosquitoes presented host selection patterns and did not feed on hosts as expected by chance alone. The articles observe different species of mosquitoes in different environments. In addition, the way the relative host abundance was determined differed. Finally, this review is not systematic. Therefore, the translation of our results to different settings should be conducted cautiously.
Note: This paper reviewed many references on host selection by Culex but seemingly failed to extract any novel conclusions north discussed previously. An important aspect not discussed here was the significance of female Culex ‘hunting strategies’ and the utilization of flight paths dictated by landscape features which seemed to determine female-host contact. This concept was originally discussed by Bidlingmayer (Bidlingmayer and Hem 1981) and later investigated for Culex tarsalis (Lothrop and Reisen 2001; Meyer et al. 1989). Theoretically, if substantiated these flight paths could be targets for control, but operationally difficult to recognize and target effectively.
Reference List
Bidlingmayer, W. L., and D. G. Hem. 1981. Mosquito flight paths in relation to the environment. Effect of the forest edge upon trap catches in the field. Mosq. News 41: 55-59.
Lothrop, H. D., and W. K. Reisen. 2001. Landscape affects the host-seeking patterns of Culex tarsalis (Diptera: Culicidae) in the Coachella Valley of California. J Med Entomol. 38: 325-332.
Meyer, R. P., W. K. Reisen, and M. M. Milby. 1989. The influence of vegetation on CO2 trap effectiveness. Proc. Calif. Mosq. Vector Control Assoc. , 57: 80