| This study examined the seroprevalence of West Nile Virus (WNV) specific Immunoglobulin G (IgG) antibodies among five different farm animal species including: Bos taurus (cattle), Capra hircus (goat), Ovis aries (sheep), Sus scrofa (pig), and Gallus gallus domesticus (chicken). Twenty samples were collected at three different time periods from each of the five species, totaling 300. March, April, May were grouped as the spring collection; June, July, August the summer collection; and September, October, November the fall collection. These grouping closely reflect the fluctuation in mosquito activity, specifically Culex species, which are the main vectors for WNV. Seroprevalence was determined using an indirect antigen capture Enzyme-Linked Immunosorbent Assay (ELISA). A Kruskal-Wallis One Way Analysis of Variance (ANOVA) suggested a significant difference of WNV specific IgG titrations among species (P = 0.009). A Tukey multiple-comparison test could not determine which species were significantly different (P > 0.05). However, chickens had the largest amount of samples positive for WNV specific IgG. The ANOVA also suggested a significant difference among collection periods (P = 0.033) but the Tukey multiple-comparison test could not determine which collection period or periods were different (P > 0.05). However, the summer collection recorded the largest number of positive samples among collection periods.; Attempts to use diagnostic tests to detect the presence of antibodies specific to a particular flavivirus have been plagued by cross-reactivity. To determine if WNV was the antigen responsible for the IgG immune response detected by ELISA I also ran an ELISA with St. Louis Encephalitis Virus (SLEV) as the antigen. A Wilcoxon signed-rank test revealed that the antibody titrations against WNV antigen were significantly different than antibody titrations against SLEV antigen (P < 0.001). Eleven of sixteen samples testing positive for WNV specific IgG showed cross-reactivity with SLEV. Of these eleven, all but one showed a four-fold difference or greater in endpoint titration to WNV antigen, in comparison to SLEV antigen. The exception showed a two-fold difference. This strongly suggests the antigen responsible for the IgG immune response was WNV. However, a co-infection with SLEV cannot be ruled out. |
