Equine Encephalomyelitis Outbreak Caused by a Genetic Lineage 2 West Nile Virus in Hungary

Abstract

Background: The spread of lineage 2 West Nile virus (WNV) from sub-Saharan regions to Europe and the unpredictable change in pathogenicity indicate a potential public and veterinary health threat and requires scientific awareness.Objectives: To describe the results of clinical and virological investigations of the 1st outbreak of a genetic lineage 2 WNV encephalomyelitis in horses.Animals: Seventeen horses with neurologic signs. Methods: Information regarding signalment, clinical signs, and outcome was obtained for each animal. Serology was performed in 15 cases, clinicopathological examination in 7 cases, and cerebrospinal fluid was collected from 2 horses. Histopathology was carried out in 4 horses, 2 of which were assessed for the presence of WNV in their nervous system.Results: WNV neutralizing antibody titers were between 10 and 270 (median, 90) and the results of other serological assays were in agreement with those of the plaque reduction neutralization test. Common signs included ataxia, weakness, asymmetric gait, muscle tremors, hypersensitivity, cranial nerve deficits, and recumbency. Twelve animals survived. Amplicons derived from the infection-positive specimens allowed molecular characterization of the viral strain.Conclusions and Clinical Importance: From our results, we conclude that this outbreak was caused by a lineage 2 WNV strain, even though such strains often are considered nonpathogenic. Neurological signs and survival rates were similar to those reported for lineage 1 virus infections. The disease occurrence was not geographically limited as had been the typical case during European outbreaks; this report describes a substantial northwestern spread of the pathogen.

The contribution of rodent models to the pathological assessment of flaviviral infections of the central nervous system

“…Lineage 2 virus transmission has principally been detected in Sub-Saharan Africa and Madagascar [17]. However, recently, these viruses have been associated with epidemics of encephalitis in horses in Hungary in 2008 [73,75] and humans in Romania [160] and Greece [124,125] in 2010. Lineages 3 and 4 comprise isolates obtained from Central and Eastern Europe [9], but these viruses have not been associated with human illnesses.…”

High Seroprevelance of West Nile Virus Antibodies Observed in Horses from Southwestern Nigeria

“…One of the earliest reports of WNV infection occurred in a 12-year-old police horse in Egypt in 1959 (Murgue et al 2002). Since then, WNV outbreaks in humans, birds and horses have been reported in Greece, Hungary, Spain, and central Europe (Papa et al 2010, Kutasi et al 2011, Lopez et al 2011, Bakonyi et al 2013. In sub-Saharan Africa, WNV activity in horses has been documented in Senegal, Côte d'Ivoire, Chad, Democratic Republic of the Congo, Gabon, and Djibouti (Cabre et al 2006), whereas in South Africa, diagnosis and seroprevalence studies of WNV in horses have been reported (Venter et al 2011).…”

The West Nile Virus-Like Flavivirus Koutango Is Highly Virulent in Mice due to Delayed Viral Clearance and the Induction of a Poor Neutralizing Antibody Response

“…Lineage II comprises WNV isolates from west, central, and east Africa and Madagascar (14,15). Historically, lineage II strains were associated with fever and mild symptoms until 2008, when the emergence of lineage II strains was responsible for outbreaks of neurological disease in Greece, Hungary, and Italy (6,8,10,16).…”