Comparison of the Efficiency and Cost of West Nile Virus Surveillance Methods in California

Abstract

Surveillance systems for West Nile virus (WNV) combine several methods to determine the location and timing of viral amplification. The value of each surveillance method must be measured against its efficiency and costs to optimize integrated vector management and suppress WNV transmission to the human population. Here we extend previous comparisons of WNV surveillance methods by equitably comparing the most common methods after standardization on the basis of spatial sampling density and costs, and by estimating optimal levels of sampling effort for mosquito traps and sentinel chicken flocks. In general, testing for evidence of viral RNA in mosquitoes and public-reported dead birds resulted in detection of WNV approximately 2-5 weeks earlier than serological monitoring of sentinel chickens at equal spatial sampling density. For a fixed cost, testing of dead birds reported by the public was found to be the most cost effective of the methods, yielding the highest number of positive results per $1000. Increased spatial density of mosquito trapping was associated with more precise estimates of WNV infection prevalence in mosquitoes. Our findings also suggested that the most common chicken flock size of 10 birds could be reduced to six to seven without substantial reductions in timeliness or sensitivity. We conclude that a surveillance system that uses the testing of dead birds reported by the public complemented by strategically timed mosquito and chicken sampling as agency resources allow would detect viral activity efficiently in terms of effort and costs, so long as susceptible bird species that experience a high mortality rate from infection with WNV, such as corvids, are present in the area.

Surveillance of maternal antibodies against West Nile virus in chicken eggs in South‐West Germany

“…Mobovirus surveillance can have different goals such as detection of vector species, human cases or vertebrate hosts. Most important for the control of WNV transmission is the early detection of virus activity, which can best be achieved through a combination of different surveillance systems . However, the presented survey method for WNV antibodies in eggs from domestic chicken did not indicate evidence for WNV circulation in the south‐west of Germany.…”

“…The technique's particular advantage is that it does not require taking blood from chickens and therefore no animal use/care protocols or authorisation permits. Surveillance for maternal antibodies in domestic chicken eggs has the same advantages as surveillance with sentinel chickens, which is generally considered to be a good method for the detection of WNV activity . Recent surveillance programmes for moboviruses in Germany already include passive detection of dead birds and active mosquito sampling .…”

“…A number of surveillance strategies can detect the circulation of moboviruses, for example testing for virus‐specific antibodies in sentinel animals or detection of virus RNA in mosquitoes. These methods have advantages and disadvantages regarding their sensitivity, collection effort or associated costs . Previous monitoring studies for WNV circulation in Germany included the screening of mosquitoes, wild resident and migratory birds, domestic poultry and horses .…”

“…WNV surveillance through the collection of blood samples from sentinel birds has several advantages: the chickens are captive, and thus, a seroconversion event indicates local transmission; chickens are preferred blood‐feeding hosts of important WNV vectors in the genus Culex . Therefore, besides passive detection of dead birds and sampling of mosquito vectors, monitoring of sentinel chickens is generally recommended in an effective WNV surveillance system . However, the main disadvantage of sentinel animals is the fact that it requires animal use/care protocols and several authorisation permits.…”

West Nile Virus–related Trends in Avian Mortality in California, Usa, 2003–12

“…Although studies have used data from the DBSP (e.g., Reisen et al 2004Reisen et al , 2013Crosbie et al 2008;Wheeler et al 2009;Ernest et al 2010;Kwan et al 2010;Carney et al 2011;Healy et al 2015), an overview and summary of WNV-infected dead birds has not been presented since the detection of WNV in California.…”