Situation-Based Surveillance: Adapting Investigations to Actual Epidemic Situations

Abstract

Surveillance approaches for wildlife diseases often are based on strategies devised for livestock diseases. Following standard protocols, surveillance sometimes continues after apparent disease elimination. However, in the case of recurrent wildlife diseases that cause decisive morbidity and mortality, efficient and effective surveillance strategies might need to be more dynamic and adaptable to the actual epidemic situation. Here, we evaluated existing surveillance schemes by reanalyzing historic data on three wildlife diseases in Europe: rabies, classical swine fever, and avian influenza. We analyzed the aims of different surveillance activities and the way in which they were performed. Our analyses revealed that static, nonadaptive surveillance was a suboptimal approach. Consequently, we propose and discuss a more adaptive alternative scheme of situation-based surveillance for recurrent wildlife diseases that cause readily recognizable morbidity and mortality.

Development of harmonised schemes for monitoring and reporting of rabies in animals in the European Union

“…The testing of healthy animals is likely to lead to negative results of no value as the presence of the virus can only be confirmed in the late stage of the disease and no "carrier state" or asymptomatic sub-clinical infection exists. Taking this concept into consideration, disease surveillance for important diseases in wildlife that show clinically visible alterations has recently been reconsidered (Thulke et al, 2009). The purpose was to evaluate common sampling schemes to derive one single improved "situation-based" strategy for wildlife diseases that cause mortality or morbidity events, including rabies.…”

“…A situation-based scheme has been proposed showing that adapting surveillance to the actual epidemic situation provides a straightforward and cost-efficient solution for an overall surveillance (Thulke et al, 2009). The study provided evidence that a sample size cannot be defined for proving the absence or the presence of rabies in wildlife regardless of the reservoir species.…”

“…No minimum sample size is required for maintaining "an effective system of disease surveillance" (Thulke et al, 2009). Veterinary authorities must be aware, or made aware, that the effective notification of rabies outbreaks can be baselined by continuing vigilance of suspect animals.…”

“…With these characteristics the routine sampling of IAs fits the needs of rabies surveillance in both rabies-endemic and rabies-free countries. From the retrospective analysis of historic rabies surveillance data sets, it was found that the sampling of IAs is always more effective for detecting virus-positive animals than sampling hunted animals regardless whether a national ORV programme was implemented or not (Thulke et al, 2009). …”

Molecular epidemiology of current classical swine fever virus isolates of wild boar in Germany

“…Should this be the case, very low virus prevalence could have led to nondetection. It is known that virological prevalence is always low, even in outbreak situations without vaccination, due to the natural development of population immunity (Anonymous, 1999;Thulke et al, 2009). As one can expect that any introduction and spread of CSF in a naïve population would trigger a significant increase of seroprevalence, these findings are surprising, especially when taking into account that the sample size taken was statistically high enough to detect an introduction during the study period (with 95 % probability to detect at least 1.74 % seroprevalence each year).…”