Monitoring of the West Nile Virus epidemic in Spain between 2010 and 2011

Abstract

West Nile virus (WNV) is a mosquito-transmitted flavivirus recognized as an emerging and re-emerging pathogen in different countries. This study describes the monitoring of the first WNV epidemic in Spain between 2010 and 2011. Between September and December 2010, 36 outbreaks of WNV in horses were reported in three different provinces of Andalusia (southern Spain), with no apparent spread outside this area. The temporal distribution and the clinical signs observed during the WNV epidemic in Spain were, in general, similar to those reported in Europe and in the Mediterranean Basin. Morbidity, mortality and fatality rate in the affected herds were 4.6, 1.4 and 35.3%, respectively. Thirty-six of 75 (47.4%) suspected herds investigated presented at least one IgM seropositive animal. The individual seroprevalence in unvaccinated animals from the infected holdings was 51.7%. RNA WNV lineage 1 virus was confirmed from blood and cerebrospinal fluid samples in a lethally infected horse. The entomological survey showed that the most abundant mosquito species detected in the affected area was Culex pipiens. A cross-sectional study was carried out in non-suspected herds between April 2010 and February 2011 in the affected area. The individual seroprevalence was 11.0%, and six of the 38 herds sampled (15.8%) presented at least one seropositive animal. The results showed active WNV circulation several months before the first outbreak was reported in horses. The seropositivity found in municipalities where clinical cases were not reported indicates a higher geographical dissemination of the virus. Significantly higher seroprevalences were detected in areas close to Morocco. Furthermore, 90 wild ruminants were tested for the presence of antibodies against WNV, but the results were all negative.

Spatio-temporal trends and risk factors affecting West Nile virus and related flavivirus exposure in Spanish wild ruminants

“…Similar seroprevalences were also found in white-tailed deer in the United States [22, 23]. In contrast, a limited number of wild ruminants from south-western Spain tested during surveillance of WNV outbreaks were negative for flavivirus antibodies using the same bELISA [8]. In our study, no antibodies were detected in roe deer, potentially due to the small sample size, while a similar study in the Czech Republic reported flavivirus exposure in roe deer, mouflons, fallow deer and red deer [24].…”

“…Five of them have circulated in Spain in the last decade. WNV exposure has been documented in mosquitoes [4], wild birds [5, 6] and different mammalian species, including humans [7], horses [8], dromedary camels ( Camelus dromedarios ) [9], wild boar ( Sus scrofa ) and Iberian pigs and red foxes ( Vulpes vulpes ) [10]. Clinical disease and mortality associated with WNV infection has also been detected in wild birds, horses and humans in this country [11, 12].…”

“…In addition, fatal cases of WN fever were reported in white-tailed deer and reindeer ( Rangifer tarandus ) in North America [25, 26]. Serosurveillance on WNV and related flaviviruses has also been performed in wild and domestic Spanish animals such as wild boar, red deer ( Cervus elaphus ), Iberian pigs, red foxes, and others [8, 10]. Accordingly, 0.2 % yearling red deer from south-western Spain had antibodies against WNV or cross-reacting flaviviruses [27].…”

Environmental Drivers of West Nile Fever Epidemiology in Europe and Western Asia—A Review

“…Monitoring of the first WNV epidemic in Spain (between 2010 and 2011) showed that many wetlands support large bird populations. The plenty of competent vectors indicate that ideal conditions for creating endemic cycles and WNV re-introduction are existed in Andalusia (Spain) [83]. …”

Predictive Modeling of West Nile Virus Transmission Risk in the Mediterranean Basin: How Far from Landing?

“…The major WNF epidemic that occurred in 2010 in Central Macedonia, Greece, was caused by a lineage 2 strain [17,18]. Recently, human cases were reported from Albania, Hungary, Israel, Italy, Macedonia, the Palestinian territory, Romania, the Russian federation, Serbia, Spain, Ukraine, Tunisia, Turkey and Greece [12,19,20,21]. Most of the European countries have implemented surveillance networks, either passive of active, that have improved the quality of available epidemiological data.…”