Environmental risk factors associated with West Nile virus clinical disease in Florida horses

Abstract

The objective of this study was to examine the extrinsic risk factors of West Nile virus (WNV) clinical disease in Florida horses as established from confirmed and negative horses tested within the state from 2001 to 2003. An Arboviral Case Information Form (ACF) was submitted by a referring veterinarian at the time of testing to the Florida Department of Agriculture and Consumer Services on every horse suspected of a viral encephalitis in Florida. A follow-up survey that focused on arbovirus prevention and farm ecology was created and mailed to the owner of each tested horse. Data from the follow-up survey indicated peak WNV prevalence in the late summer months in Florida. Quarter horses were the most commonly affected breed. The WNV vaccine was highly protective and natural water on the property also had a protective association. Factors that increased the risk of WNV to horses were the use of fans and a stable construction of solid wood or cement. Some risk indicators were dead birds on the property and other ill animals on the property. Data from this retrospective study have helped identify factors associated with WNV transmission in equines in Florida. Horses that have not been vaccinated and show clinical signs of arboviral infection from June to November should be tested for WNV. Horses that have been vaccinated and show clinical signs should be tested when the vaccination was administered within 1 month or greater than 6 months prior to the onset of clinical symptoms associated with WN infection.

Spatial and Temporal Distribution of West Nile Virus in Horses in Israel (1997–2013) - from Endemic to Epidemics

“…In addition, grooming and anti-pesticides regimes are most likely stricter in the Warmblood breeds since they are mostly used for competitions in Israel while the Quarter horses and cross breeds are used mostly for pleasure riding. The higher seroprevalence detected in the Quarter horses in our study is in accordance with a study performed in Florida, USA, in which Quarter horses were the most commonly affected breed [13] , and with a study performed in Saskatchewan, Canada, which indicated that most of the WNV clinical cases were light horse breeds and most were used for pleasure riding [54] . However, as opposed to the above study, in which dark coloured horses were most commonly affected with WNV [54] , univariate analysis in the current study demonstrated higher seroprevalence in the lighter colours (grey/light appaloosa; 70.4%) as compared to the darker colours (black/dark brown/dark grey; 52.9%).…”

“…West Nile virus imposes great threat on human and animal health not only by emerging in new geographical areas but also as it causes epidemics in endemic areas. Despite the presence of WNV in most of the United States already a decade ago and its spread to all regions of the continental US throughout this decade [13] , WNV epidemic activity was demonstrated in 2012, in which more human disease cases were reported nationally than any year since 2003. This outbreak resulted in 2,873 cases of neuroinvasive disease and 286 human deaths [14] , [15] .…”

Serological evidence of co‐circulation of West Nile and Usutu viruses in equids from western Spain

“…Few studies have addressed the influence of this factor in USUV horse infections. Some authors found differences between horse breeds and WNV infection (Ahmadnejad et al., 2011; Rios et al., 2009) but not with USUV infection (Bażanów et al., 2018). Ahmadnejad et al.…”

“…Ahmadnejad et al. (2011) also found that the Arab breed was a seropositive risk factor to WNV infection in horses of Iran and the quarter horses were four times more likely to be exposed to WNV than mixed breeds (Rios et al., 2009). In our case, the pure breeds, especially the Arabian breed and the Thoroughbred, seem to have a greater susceptibility to infection, possibly due to their training habits.…”

Effects of weather and landscape on the equine West Nile virus infection risk in Mississippi, USA

“…Therefore, it is plausible to predict that land cover diversity would increase the species diversity of avian communities and thus reduce equine WNv infection risks (Roche et al, 2012). Equine WNv infections varied spatially at the county level in the American states of North Dakota, Texas and Florida (Mongoh et al, 2007;Ward and Scheurmann, 2008;Rios et al, 2009). Equine and human WNv vectors may differ in abundance and may be differently influenced by weather conditions.…”