Publikationsdatenbank

West Nile-Virus-Infektion beim Pferd - ein Überblick:
West Nile Virus infection in the horse – an overview (2019)

Art

Zeitschriftenartikel / wissenschaftlicher Beitrag

Autoren

Stöckle, Sabita Diana (WE 17)

Winter, Judith (WE 17)

Gehlen, H. (WE 17)

Quelle

Pferdeheilkunde : offizielles Organ der DVG, Fachgruppe Pferdekrankheiten = Equine medicine

Bandzählung: 35

Heftzählung: 3

Seiten: 240 – 245

ISSN: 0177-7726

Verweise

URL (Volltext): http://www.pferdeheilkunde.de/10.21836/PEM20190305

DOI: 10.21836/PEM20190305

Kontakt

Pferdeklinik

Oertzenweg 19 b
14163 Berlin
+49 30 838 62299 / 62300
pferdeklinik@vetmed.fu-berlin.de

Abstract / Zusammenfassung

The arbovirus West Nile Virus (WNV) can cause fatal encephalitis in horses and humans. WNV belongs to the family Flaviviridae and the genus Flavivirus. It was first described in 1937 in the West Nile district in Uganda. The diameter of the single strand, enveloped RNA virus with a nucleocapside is approximately 50 nm. Horses and humans are so-called “dead-end hosts” that are infected by mosquitos but cannot infect mosquitos in return. The most important vector is Culex pipiens. The main host of WNV are birds, which transmit the virus to the mosquito, while it feeds on them. Birds like sparrows can have a high titer, but show no clinical signs. Others like raptors and corvidae become diseased and might die. Many infected horses do not develop any clinical signs, whereas approximately 8 % develop neurological disease. At the beginning, clinical signs are rather nonspecific and include depression, anorexia, and fever. The developing neurological signs are typical for a polioencephalomyelitis. These include ataxia with stumbling, staggering, and a wobbly gait. Horses can also show circling, weakness of the hindlimbs, paralysis of one or more limbs, muscle fasciculations, proprioceptive deficits blindness, pendant lip or paralysis of the lip, and teeth grinding. These signs can progress to recumbency or to acute death. A dysfunction of the autonomous nervous system can lead to respiratory arrest and to disturbances in the gastrointestinal system. There is no specific therapy of WNV infection so far. Antiviral medications do not have a reliable effect. Recommendations include the administration of flunixin-meglumine (1.1 mg/kg IV BID), tranquilizers (acepromazin: 0.02 mg/kg IV or 0.05 mg/kg IM) to relieve fear as well as sedatives (detomidine: 0.02–0.04 mg/kg IV) for prolonged quieting. In the recumbent horse, therapy is usually more aggressive and can include mannitol (0.25–2mg/kg IV SID) and dexamethasone – sodium (0.05–0.1 mg/kg IV SID). Improvement is usually seen within 3–7 days, but 30 % of the horses experience a relapse of clinical signs. WNV encephalitis cannot be diagnosed solely on a clinical basis. The clinical suspicion always has to be confirmed by a laboratory diagnosis. Organic disorders can be excluded using routine laboratory tests. The infection with WNV can be proven by the detection of the virus genome (PCR) or by detecting specific IgM-antibodies (ELISA). As viremia is short in horses, the PCR often yields false negative results. As the infection of a bird or horse with WNV is a notifiable disease in Germany, the national reference laboratory (Nationales Referenzlabor am Friedrich Loeffler Institut) has to confirm the diagnosis. Since 2008, WNV outbreaks have been reported more frequently and the incidence of neuroinvasive disease in humans and animals has also increased. In 2017, 204 cases were reported in Europe, of which 23 were fatal. In horses, 127 cases were registered. The incidence of WNV infection in horses was 285 in the EU in 2018. In Germany, the first WNV infection in a horse was confirmed on the 21st of September 2018 in the county Elbe-Elster (Brandenburg). The second case was detected in the county Salzlandkreis (Sachsen-Anhalt). The vaccination of horses, especially in concerned regions, is highly recommended. The initial immunization should accomplished before the beginning of the mosquito season (end of May).