A cross-sectional serosurvey in a sheep population in central Italy following a bluetongue epidemic (original) (raw)
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BMC Veterinary Research, 2008
Background: In August 2006 a major epidemic of bluetongue virus serotype 8 (BTV8) started off in North-West Europe. In the course of 2007 it became evident that BTV8 had survived the winter in North-West Europe, re-emerged and spread exponentially. Recently, the European Union decided to start vaccination against BTV8. In order to improve the understanding of the epidemiological situation, it was necessary to execute a cross-sectional serological study at the end of the BT vector season. Cattle were the target species for cross-sectional serological studies in Europe at the end of 2006 and 2007. However, there was no information on the BTV8seroprevalence in sheep and goats.
2009
Bluetongue virus serotype 8 (BTV-8) was detected in Austria for the first time, in November 2008. Due to outbreaks previously occurred in German regions close to the Austrian border, an active surveillance system was in place and allowed for an early identification of BTV-8 in the country. Mass emergency vaccination was started in the western part of the country in July 2008, due to the inclusion of that area in the protection zone around German outbreaks. The main objective of this work was to study the occurrence of BTV-8 in Austria in 2008 by i) describing the outbreak in Schärding, ii) comparing the two similar districts with different preventive strategies where BTV was identified-Schärding and Bregenz, iii) evaluating the influence of population dynamics in the duration of vaccinal immunity of cattle from the region of Styria included in the emergency vaccination program, and iv) developing a transmission model for the Styria region. From the analysis of the BT cases occurred in Schärding it was concluded that the moments of infection were very likely between May and October 2008, considering the optimal temperatures for Culicoides abundance that were verified in the region between April and September. The comparison between Schärding and Bregenz, concluded that the former district gathered a higher number of risk factors for disease spread. Higher cattle density in Schärding may have contributed to a higher spread of BTV, whereas the performance of a preventive mass vaccination campaign in Bregenz, most likely contributed for the opposite. It was also found that the proportion of PCR + results amongst c-ELISA positive sera was statistically associated to the district of origin. A much lower proportion was observed in Bregenz when compared to Schärding. The analysis of the dynamics of cattle population in Styria resulted in an estimation of 3% year variation in cattle numbers which probably has a negligible effect on the decrease of the HIT in a time-frame of one year, leading to the conclusion that the lost of population immunity to BTV in Styria will be mostly due to the lost of immunity conferred by vaccination that lasts close to one year. The results of the BT transmission model for Styria indicated that the risk of occurrence of secondary infections in the summer months is not negligible, with a maximum estimated R 0 of 2.66. These studies highlight the importance of epidemiological analysis of available data, using tools like mathematical modeling and GIS in order to understand disease occurrence in animal populations.
Monitoring bluetongue disease (BTV-1) epidemic in southern Spain during 2007
Preventive Veterinary Medicine, 2010
On the 25th of July 2007, bluetongue virus (BTV) serotype 1 was detected in Andalusia, southern Spain for the first time. A total of 4436 farms infected with BTV-1 were confirmed during that year: 3162 in sheep flocks, 113 in goat flocks, 7 in cattle herds and 1154 in mixed farms (sheep, goat and/or cattle in the same farm). The most common clinical signs were: fever, depression, lethargy, facial edema, and salivation (observed in more than 70% of the infected farms). Lesions in oral mucosa, lameness and dyspnea were also frequently observed.
PLoS ONE, 2014
Wild and domestic ruminants are susceptible to Bluetongue virus (BTV) infection. Three BTV serotypes (BTV-4, BTV-1 and BTV-8) have been detected in Spain in the last decade. Even though control strategies have been applied to livestock, BTV circulation has been frequently detected in wild ruminant populations in Spain. The aim of the present study is to assess the role for wild ruminants in maintaining BTV after the vaccination programs in livestock in mainland Spain. A total of 931 out 1,914 (48.6%) serum samples, collected from eight different wild ruminant species between 2006 and 2011, were BTV positive by ELISA. In order to detect specific antibodies against BTV-1, BTV-4 and BTV-8, positive sera were also tested by serumneutralisation test (SNT). From the ELISA positive samples that could be tested by SNT (687 out of 931), 292 (42.5%) showed neutralising antibodies against one or two BTV serotypes. For each BTV seroptype, the number of outbreaks in livestock (11,857 outbreaks in total) was modelled with pure autoregressive models and the resulting smoothed values, representing the predicted number of BTV outbreaks in livestock at municipality level, were positively correlated with BTV persistence in wild species. The strength of this relationship significantly decreased as red deer (Cervus elaphus) population abundance increased. In addition, BTV RNA was detected by real time RT-PCR in 32 out of 311 (10.3%) spleen samples from seropositive animals. Although BT outbreaks in livestock have decreased substantially after vaccination campaigns, our results indicated that wild ruminants have been exposed to BTV in territories where outbreaks in domestic animals occurred. The detection of BTV RNA and spatial association between BT outbreaks in livestock and BTV rates in red deer are consistent with the hypothesis of virus circulation and BTV maintenance within Iberian wild ruminant populations.
Veterinary Medicine and Science
Background: Bluetongue (BT), a vector-borne disease of wild and domestic ruminants, is responsible for severe economic losses in flocks. To reduce this impact, a surveillance and control plan was implemented in Tunisia. However, the epidemiological situation of BT remains incompletely understood, especially for the circulating serotypes. Objective: The aim of this survey was to determine the seroprevalence, to identify the circulating serotypes and to identify the associated risk factors for bluetongue virus (BTV) circulation in Tunisia using risk-based sampling (RBS). Methods: A total of 3314 blood samples were randomly collected from 67 sectors using risk-based sampling and screened by competitive enzyme-linked immunosorbent assays (c-ELISAs). Out of the 1330 positive samples, 200 samples were analysed by serum neutralization test (SNT) to identify circulating BTV serotypes. Results: Of 3314 sera, 1330 were c-ELISA-positive (40.1%) for antibodies against the BTV structural protein VP7. The result of SNT showed the presence of BTV-1, BTV-2, BTV-3, BTV-4 and, for the first time in Tunisia, BTV-26. The logistic regression model revealed that older animals had nearly two times the odds of being infected with BTV compared to younger animals. Flocks with a history of BT were almost 1.5 times more likely to be at risk for contracting BTV infection. The flock size, housing indoors and intensive production system were significant protective factors. Conclusions: High seroprevalence of BTV among sheep was highlighted in Tunisia. The neutralization test showed the presence of the following BTV serotypes: BTV-1, BTV-2, BTV-3, BTV-4 and, for the first time in Tunisia, BTV-26. Age, production system and flock size were important variables associated with BTV infection in sheep. This finding is crucial, as it will allow the adjustment of the BT control programme in Tunisia.
High seroprevalence of bluetongue virus infection in sheep flocks in West Azerbaijan, Iran
Comparative Immunology Microbiology and Infectious Diseases, 2010
Bluetongue (BT) is an important disease of ruminant livestock that is currently emerging in previously unaffected regions, most notably extensive portions of Europe. The epidemiology of BT virus (BTV) infection is poorly defined in much of the world, including extensive portions of Asia and the Middle East. Thus, the objective of this study was to describe the distribution and seroprevalence of BTV infection of sheep in West Azerbaijan Province of Iran, and to identify demographic and climatological factors associated with exposure of these sheep to BTV infection. BTV infection was widespread in the province as 400 of 1153 (34.7%) of the sheep sera evaluated contained antibodies to BTV, as determined by competitive ELISA, and 172 of 184 flocks included BTV seropositive sheep (93.5%). Multivariable logistic analyses failed to identify specific demographic or animal management practices that were predictive of BTV serological status of the sheep flocks. The virus serotypes and vector insects that occur within the region remain unknown. #