Six-year surveillance of Newcastle disease virus in wild birds in north-eastern Spain (Catalonia).

Given that Newcastle disease (ND) is one of the major threats for the poultry industry, testing of Newcastle disease virus (NDV) has been carried out since 2010 in cases of mortality in wild birds (passive surveillance) in Catalonia. The objective is to provide an early warning system to prevent the infection of poultry. Since 2010, 35 episodes of mortality in wild birds were attributed to NDV infection. Throughout this period there was a progressive expansion of NDV to new areas, with an increase in the episodes of mortality, although it is not clear whether they were the result of the spread of the virus, or of the improvement of the surveillance. Phylogenetic analyses indicate that two distinct sublineages of NDV, 4a and 4b, were circulating in Catalonia. Both sublineages seem to be endemic in the wild bird population, affecting mainly Eurasian-collared doves, with a clear pattern in relation to its spatial distribution (coincident with the distribution of this species), and its temporal distribution (with the majority of cases between September and February). So far, endemicity in wild birds has not resulted in ND outbreaks in poultry. However, there are still many uncertainties about, for example, whether NDV may expand to new areas of Catalonia (with higher poultry density), or about the threat that the apparently more novel sublineage 4a may represent. Hence, efforts should be made so that measures to prevent infection of poultry farms (particularly in high-risk areas and periods) are encouraged, and surveillance is maintained.

Role of wild ruminants in the epidemiology of bluetongue virus serotypes 1, 4 and 8 in Spain.

Although the importance of wild ruminants as potential reservoirs of bluetongue virus (BTV) has been suggested, the role played by these species in the epidemiology of BT in Europe is still unclear. We carried out a serologic and virologic survey to assess the role of wild ruminants in the transmission and maintenance of BTV in Andalusia (southern Spain) between 2006 and 2010.A total of 473 out of 1339 (35.3%) wild ruminants analyzed showed antibodies against BTV by both ELISA and serum neutralization test (SNT). The presence of neutralizing antibodies to BTV-1 and BTV-4 were detected in the four species analyzed (red deer, roe deer, fallow deer and mouflon), while seropositivity against BTV-8 was found in red deer, fallow deer and mouflon but not in roe deer. Statistically significant differences were found among species, ages and sampling regions. BTV RNA was detected in twenty-one out of 1013 wild ruminants (2.1%) tested. BTV-1 and BTV-4 RNA were confirmed in red deer and mouflon by specific rRT-PCR.BTV-1 and BTV-4 seropositive and RNA positive wild ruminants, including juveniles and sub-adults, were detected years after the last outbreak was reported in livestock. In addition, between the 2008/2009 and the 2010/2011 hunting seasons, the seroprevalence against BTV-1, BTV-4 and BTV-8 increased in the majority of provinces, and these serotypes were detected in many areas where BTV outbreaks were not reported in domestic ruminants. The results indicate that wild ruminants seem to be implicated in the dissemination and persistence of BTV in Spain.