Antibody Prevalence to Influenza Type A in Wild Boars of Northern Ukraine

Abstract

ObjectiveA preliminary serological survey was carried out to assess thelikelihood of Influenza A (IA) infection in wild boars and begin tocharacterize the role of wild boars in the epidemiology of the IA virus.IntroductionDomestic swine have been viewed as important for the adaptationand spillover of IA from birds into human populations as they aresensitive to both avian and mammalian (including human) influenzaviruses [1]. However, in much of Eurasia and North America wildswine are geographically widespread, abundant and often come inclose contact with humans in rural and agricultural settings. Untilrecently, little attention has been paid to this as an alternate routefor IA transmission to human and domestic populations and itssignificance is not clear.Therefore, the monitoring of the exposure of wild mammals toIA was viewed as essential as potential vectors impacting domesticanimals and public health.MethodsFrom September to December 2014, wild boar sera were collectedby professional hunters in 4 Oblasts of Ukraine: Volyn, Rivne,Zhytomyr, and Chernihiv. Blood was collected from jugular veins.Sera were collected in Eppendorf type tubes, separated from wholeblood without centrifugation and stored at -20C until serologicallytested. To detect antibodies to IA, a blocking ELISA was used.Serum samples were tested using commercial test kits “InfluenzaA Ab Test” (IDEXX, USA). Specific antibodies in wild boarserum samples were detected based on manufacturer’s instructions.Briefly, sera were diluted 1:10, and incubated in test wells for60 minutes at room temperature, followed by three washes. Anti-IAHorseradish Peroxidase HRP conjugate was then added and incubatedfor 30 minutes at room temperature. Following three washes,3',5,5’-tetramethylbenzidine (TMB), as a substrate, was addedand incubated for 15 minutes. Absorbencies were measured at 650A using a iMark Microplate Absorbance Reader and data wereanalyzed using Microsoft Excel. Based on the manufacturer’sinstructions, a serum sample was considered positive if the sample/negative control ratio (S/N) did not exceed a threshold of 0.60.Statistical analyses were performed with the program “StatisticsCalculator”.ResultsSera from 120 wild boars that were shot in 2014 were tested. Thirtyboars from each of 4 Oblasts were collected in the north central andnorthwestern regions of Ukraine. Antibodies against IAV weredetected using ELISA in 27 samples (22.5 %), (Table 1). Antibodiesto IA virus were detected in at least some of the wild boars from all ofthe 4 Oblasts. The highest percentages of seropositive samples weredetected in wild boar from Volyn and Zhytomyr Oblasts (Fig. 1).The prevalence differences were statistically significant only betweensamples from Volyn and Chernihiv Oblasts (P<0.05). The averageS/N value of all positive serum samples was 0.36±0.03.ConclusionsThis preliminary survey of IA antibodies in wild boar populationsof northern Ukraine indicates a substantial presence of exposure toIAV throughout the region.Infection of wild boar populations provides an alternative oradditional route for spillover from wild populations to domesticanimals and humans. This potential has received relatively littleattention until recently, likely in part because feral swine populationshave not been viewed as a serious challenge in most regions of theworld where the natural history of IA has received serious study.Table 1Seroprevalence of IA virus in wild boars in UkraineFigure 1Serological surveillance of wild boars for IA virus innorthern Ukraine