Ruminant pestiviruses in North Africa.

Ruminant pestiviruses are widely distributed worldwide, causing congenital disease and massive economic losses. Although ruminant production is an important economic sector in North Africa, the knowledge about pestiviruses is scarce. The present study aimed at assessing the presence of Pestivirus in cattle in Algeria, and to review the data available on ruminant pestiviruses in North Africa. A cross-sectional study was conducted on dairy farms from North-Western Algeria. Blood samples from 234 dairy cattle from 31 herds were collected. All sera were analysed for the presence of antibodies using a commercial iELISA. The presence of Pestivirus RNA was also assessed by using a Reverse Transcription-PCR, and PCR-positive samples were sequenced. Risk factors related to Pestivirus infection were also analysed. The review of the presence of ruminant pestiviruses in North Africa was performed using a systematic search and compilation methodology of the peer-reviewed literature available in order to identify gaps of knowledge for future research. The seroprevalence at population and farm levels obtained in the present study (59.9% and 93.5%, respectively) concur with data reported in neighbouring countries. Risk factors associated with Pestivirus infection in cattle were the presence of sheep in the herd and the animal category (cow vs heifer). Furthermore, we confirmed the presence of BVDV-1a in Algeria. The scarce data suggest an endemic epidemiological scenario of pestivirus in livestock. The lack of studies about the epidemiology and molecular variability of ruminant pestiviruses in livestock and wildlife in North Africa is of concern for animal health and wildlife conservation, and needs to be addressed.

Experimental study of the susceptibility of a European Aedes albopictus strain to dengue virus under a simulated Mediterranean temperature regime.

Dengue virus (DENV) has re-emerged in Europe driven by the geographic expansion of the mosquito species Aedes albopictus and Aedes aegypti (Diptera: Culicidae) and the introduction of the virus by viraemic travellers. In the present study, the vector competence (VC) of Ae. albopictus collected in Catalonia (northeast Spain) was evaluated for two different DENV strains, DENV-1 and DENV-2, the serotypes responsible for all outbreaks of dengue that have occurred in Europe. Mosquitoes were reared under environmental conditions mimicking the mean temperature and humidity recorded in July on the Mediterranean coast of Catalonia. Mosquitoes were fed on an artificial infectious bloodmeal and, at 14 days post-exposure, infection, disseminated infection and transmission rates (IR, DIR, TR) and transmission efficiency (TE) were determined by testing the virus in the body, legs and saliva. The tested Ae. albopictus strain was found to be susceptible to both DENV-1 and DENV-2 and to be able to transmit DENV-1. This is the first time that the VC of Ae. albopictus for DENV has been tested in Europe in this specific context (i.e. mimicking the Mediterranean temperature and humidity recorded in Catalonia in July). This study confirms the potential of Ae. albopictus to start autochthonous DENV transmission cycles in the Mediterranean basin.

Emergence and spread of highly pathogenic avian influenza A(H5N8) in Europe in 2016-2017.

Circulation of highly pathogenic avian influenza (HPAI) viruses poses a continuous threat to animal and public health. After the 2005-2006 H5N1 and the 2014-2015 H5N8 epidemics, another H5N8 is currently affecting Europe. Up to August 2017, 1,112 outbreaks in domestic and 955 in wild birds in 30 European countries have been reported, the largest epidemic by a HPAI virus in the continent. Here, the main epidemiological findings are described. While some similarities with previous HPAI virus epidemics were observed, for example in the pattern of emergence, significant differences were also patent, in particular the size and extent of the epidemic. Even though no human infections have been reported to date, the fact that A/H5N8 has affected so far 1,112 domestic holdings, increases the risk of exposure of humans and therefore represents a concern. Understanding the epidemiology of HPAI viruses is essential for the planning future surveillance and control activities.

Assessing the variability in transmission of bovine tuberculosis within Spanish cattle herds.

In Spain, despite years of efforts to eradicate bovine tuberculosis (bTB), the disease is still endemic, with some areas of high prevalence. In this context, the surveillance and control plans may need to be re-evaluated, and understanding the dynamics of bTB spread within Spanish herds may help to develop new strategies for reducing the time for detection of infected herds and for the elimination of bTB from the herds already infected. Here, we developed a compartmental stochastic model to simulate bTB within-herd transmission, fed it with epidemiological data from 22 herds (obtained from a previous work) and carried out parameter inference using Approximate Bayesian Computing methods We also estimated the "Within-herd transmission potential Number" (Rh), i.e. the average number of secondary cases generated by a single animal infected introduced into a totally susceptible herd, considering different scenarios depending on the frequency of controls. The median global values obtained for the transmission parameters were: for the transmission coefficient (ß), 0.014 newly infected animals per infectious individual per day (i.e. 5.2 per year), for the rate at which infected individuals become infectious (α), 0.01 per day (equivalent to a latent period of 97 days), and for the rate at which infected individuals become reactive to the skin test (α1), 0.08 per day (equivalent to a period of 12 days for an infected animal to become reactive). However, the results also evidenced a great variability in the estimates of those parameters (in particular ß and α) among the 22 herds. Considering a 6-month interval between tests, the mean Rh was 0.23, increasing to 0.82 with an interval of 1 year, and to 2.01 and 3.47 with testing intervals of 2 and 4 years, respectively.

Epidemiology and spatio-temporal analysis of West Nile virus in horses in Spain between 2010 and 2016.

During the last decade, West Nile virus (WNV) outbreaks have increased sharply in both horses and human in Europe. The aims of this study were to evaluate characteristics and spatio-temporal distribution of WNV outbreaks in horses in Spain between 2010 and 2016 in order to identify the environmental variables most associated with WNV occurrence and to generate high-resolution WNV suitability maps to inform risk-based surveillance strategies in this country. Between August 2010 and November 2016, a total of 403 WNV suspected cases were investigated, of which, 177 (43.9%) were laboratory confirmed. Mean values of morbidity, mortality and case fatality rates were 7.5%, 1.6% and 21.2%, respectively. The most common clinical symptoms were as follows: tiredness/apathy, recumbency, muscular tremor, ataxia, incoordination and hyperaesthesia. The outbreaks confirmed during the last 7 years, with detection of WNV RNA lineage 1 in 2010, 2012, 2013, 2015 and 2016, suggest an endemic circulation of the virus in Spain. The spatio-temporal distribution of WNV outbreaks in Spain was not homogeneous, as most of them (92.7%) were concentrated in western part of Andalusia (southern Spain) and significant clusters were detected in this region in two non-consecutive years. These findings were supported by the results of the space-time scan statistics permutation model. A presence-only MaxEnt ecological niche model was used to generate a suitability map for WNV occurrence in Andalusia. The most important predictors selected by the Ecological Niche Modeling were as follows: mean annual temperature (49.5% contribution), presence of Culex pipiens (19.5% contribution), mean annual precipitation (16.1% contribution) and distance to Ramsar wetlands (14.9% contribution). Our results constitute an important step for understanding WNV emergence and spread in Spain and will provide valuable information for the development of more cost-effective surveillance and control programmes and improve the protection of horse and human populations in WNV-endemic areas.

Serological Follow-up of Tuberculosis in a Wild Boar Population in Contact with Infected Cattle.

There is an increasing concern in several European countries over the role that tuberculosis (TB)-infected wild boar may play in the progress of bovine TB eradication campaigns. In 2004, as a consequence of the detection of a TB focus in wild boar from a National Game Reserve (NGR) located in southern Catalonia, a surveillance programme based on post-mortem inspection for detection of macroscopic TB-like lesions (TBLL) was initiated in the affected area. The source of infection for wild boar was linked to a tuberculous cattle herd located in the same area. Besides, the results of the surveillance programme in wild boar were used for the validation of an indirect enzyme-linked immunosorbent assay (ELISA) specific for Mycobacterium tuberculosis complex (MTBC) IgG antibodies. Using this ELISA, a seven-year serological study of MTBC in wild boar from the NGR was conducted in 173 animals (93 adults, 44 juveniles-yearlings and 36 piglets) culled between 2004 and 2010. ELISA results and presence of TBLL showed excellent agreement for adult and juvenile wild boar (Kappa index = 0.85; 95% CI: 0.76-0.95). Of the thirty-eight adults, yearlings and juveniles classified as positives by the ELISA, 34 (89%) showed TBLL at necropsy. In contrast, none of the ELISA-positive wild boar piglets (n = 20) showed TBLL, suggesting the detection of early antibody responses to the infection. Overall, this study contributes to the knowledge of wild boar humoral responses to MTBC. The results also highlight the usefulness of this serological test for wild boar TB surveillance.

Monitoring of West Nile virus, Usutu virus and Meaban virus in waterfowl used as decoys and wild raptors in southern Spain.

In the last decade, the number of emerging flaviviruses described worldwide has increased considerably, with wild birds acting as the main reservoir hosts of these viruses. We carried out an epidemiological survey to determine the seroprevalence of antigenically related flaviviruses, particularly West Nile virus (WNV), Usutu virus (USUV) and Meaban virus (MBV), in waterfowl used as decoys and wild raptors in Andalusia (southern Spain), the region considered to have the highest risk of flaviviruses circulation in Spain. The overall flaviviruses seroprevalence according to bELISA was 13.0% in both in decoys (n=1052) and wild raptors (n=123). Specific antibodies against WNV, USUV and MBV were confirmed by micro virus neutralization tests in 12, 38 and 4 of the seropositive decoys, respectively. This is the first study on WNV and USUV infections in decoys and the first report of MBV infections in waterfowl and raptors. Moreover we report the first description of WNV infections in short-toed snake eagle (Circaetus gallicus) and Montagu's harrier (Circus pygargus). The seropositivity obtained indicates widespread but not homogeneous distribution of WNV and USUV in Andalusia. The results also confirm endemic circulation of WNV, USUV and MBV in both decoys and wild raptors in southern Spain. Our results highlight the need to implement surveillance and control programs not only for WNV but also for other related flaviviruses. Further research is needed to determine the eco-epidemiological role that waterfowl and wild raptors play in the transmission of emerging flaviviruses, especially in decoys, given their close interactions with humans.

Understanding Spatio-Temporal Variability in the Reproduction Ratio of the Bluetongue (BTV-1) Epidemic in Southern Spain (Andalusia) in 2007 Using Epidemic Trees.

Andalusia (Southern Spain) is considered one of the main routes of introduction of bluetongue virus (BTV) into Europe, evidenced by a devastating epidemic caused by BTV-1 in 2007. Understanding the pattern and the drivers of BTV-1 spread in Andalusia is critical for effective detection and control of future epidemics. A long-standing metric for quantifying the behaviour of infectious diseases is the case-reproduction ratio (Rt), defined as the average number of secondary cases arising from a single infected case at time t (for t>0). Here we apply a method using epidemic trees to estimate the between-herd case reproduction ratio directly from epidemic data allowing the spatial and temporal variability in transmission to be described. We then relate this variability to predictors describing the hosts, vectors and the environment to better understand why the epidemic spread more quickly in some regions or periods. The Rt value for the BTV-1 epidemic in Andalusia peaked in July at 4.6, at the start of the epidemic, then decreased to 2.2 by August, dropped below 1 by September (0.8), and by October it had decreased to 0.02. BTV spread was the consequence of both local transmission within established disease foci and BTV expansion to distant new areas (i.e. new foci), which resulted in a high variability in BTV transmission, not only among different areas, but particularly through time, which suggests that general control measures applied at broad spatial scales are unlikely to be effective. This high variability through time was probably due to the impact of temperature on BTV transmission, as evidenced by a reduction in the value of Rt by 0.0041 for every unit increase (day) in the extrinsic incubation period (EIP), which is itself directly dependent on temperature. Moreover, within the range of values at which BTV-1 transmission occurred in Andalusia (20.6°C to 29.5°C) there was a positive correlation between temperature and Rt values, although the relationship was not linear, probably as a result of the complex relationship between temperature and the different parameters affecting BTV transmission. Rt values for BTV-1 in Andalusia fell below the threshold of 1 when temperatures dropped below 21°C, a much higher threshold than that reported in other BTV outbreaks, such as the BTV-8 epidemic in Northern Europe. This divergence may be explained by differences in the adaptation to temperature of the main vectors of the BTV-1 epidemic in Andalusia (Culicoides imicola) compared those of the BTV-8 epidemic in Northern Europe (Culicoides obsoletus). Importantly, we found that BTV transmission (Rt value) increased significantly in areas with higher densities of sheep. Our analysis also established that control of BTV-1 in Andalusia was complicated by the simultaneous establishment of several distant foci at the start of the epidemic, which may have been caused by several independent introductions of infected vectors from the North of Africa. We discuss the implications of these findings for BTV surveillance and control in this region of Europe.

Estimation of the individual slaughterhouse surveillance sensitivity for bovine tuberculosis in Catalonia (North-Eastern Spain).

The achievement of the Officially Tuberculosis Free (OTF) status in regions with low bovine Tuberculosis (bTB) herd prevalence, as is the case of North-Eastern Spain (Catalonia), might be a likely option in the medium term. In this context, risk-based approaches could be an alternative surveillance strategy to the costly current strategy. However, before any change in the system may be contemplated, a reliable estimate of the sensitivity of the different surveillance components is needed. In this study, we focused on the slaughterhouse component. The probability of detection of a bTB-infected cattle by the slaughterhouses in Catalonia was estimated as the product of three consecutive probabilities: (P1) the probability that a bTB-infected animal arrived at the slaughterhouse presenting Macroscopically Detectable Lesions (MDL); (P2) the probability that MDL were detected by the routine meat inspection process and (P3) the probability that the veterinary officer suspected bTB and sent the sample for laboratory confirmation. The first probability was obtained from data collected through the bTB eradication program carried out in Catalonia between 2005 and 2008, while the last two were obtained through the expert opinion of the veterinary officers working at the slaughterhouses who fulfilled a questionnaire administered during 2014. The bTB surveillance sensitivity of the different cattle slaughterhouses in Catalonia obtained in this study was 31.4% (CI 95%: 28.6-36.2), and there were important differences among them. The low bTB surveillance sensitivity was mainly related with the low probability that a bTB-infected animal arrived at the slaughterhouse presenting MDL (around 44.8%). The variability of the sensitivity among the different slaughterhouses could be explained by significant associations between some variables included in the survey and P2. For instance, factors like attendance to training courses, number of meat technicians and speed of the slaughter chain were significantly related with the probabilities that a MDL was detected by the meat inspection procedure carried out in the slaughterhouse. Technical and policy efforts should be focused on the improvement of these factors in order to maximize the slaughterhouse sensitivity.

Risk factors for bovine tuberculosis persistence in beef herds of Southern and Central Spain.

In order to assess risk factors related to bovine tuberculosis (bTB) persistence, a case-control study, comparing persistent versus transient bTB infected beef farms from Central and Southern Spain, was conducted. Farms were matched by herd size and geographical location (county). A questionnaire administered by personal interview was conducted on 150 herds (80 controls and 70 cases) from Andalucia and Castilla La Mancha regions. The questionnaire included questions related to the personnel involved in routine diagnostics, structure of the farm and of the herd, management, presence of other domestic species and of wildlife reservoirs. According to the results of our study, farms with large pasture areas and bTB infected neighbors had more difficulties in eradicating the disease, and therefore, were more likely to suffer a persistent bTB infection. The odds of bTB persistence were between 1.2 and 5.1 (i.e., 95% confidence interval of the OR) times higher in those herds that had a neighbor infected herd. Farms with large pasture areas had odds between 1.2 and 12.7 (i.e., 95% confidence interval of the OR) times higher of having a persistent bTB episode than farms with small pasture areas.

Ecological surveillance for West Nile in Catalonia (Spain), learning from a five-year period of follow-up.

To enhance early detection of West Nile virus (WNV) transmission, an integrated ecological surveillance system was implemented in Catalonia (north-eastern Spain) from 2007 to 2011. This system incorporated passive and active equine surveillance, periodical testing of chicken sentinels in wetland areas, serosurveillance wild birds and testing of adult mosquitoes. Samples from 298 equines, 100 sentinel chickens, 1086 wild birds and 39 599 mosquitoes were analysed. During these 5 years, no acute WNV infection was detected in humans or domestic animal populations in Catalonia. WNV was not detected in mosquitoes either. Nevertheless, several seroconversions in resident and migrant wild birds indicate that local WNV or other closely related flaviviruses transmission was occurring among bird populations. These data indicate that bird and mosquito surveillance can detect otherwise silent transmission of flaviviruses and give some insights regarding possible avian hosts and vectors in a European setting.

Assessment of the risk of a bluetongue outbreak in Europe caused by Culicoides midges introduced through intracontinental transport and trade networks.

The importation of infected hosts and the arrival of windborne infected Culicoides (Diptera: Ceratopogonidae) were considered unlikely mechanisms for bluetongue virus (BTV) incursion into a BTV-free area during the recent BTV serotype 8 (BTV-8) epidemic in northern Europe. Therefore, alternative mechanisms need to be considered. Air, sea and land transport networks continue to expand, and an important consequence of this is vector-borne pathogen importation. One important aspect of bluetongue (BT) epidemiology not yet addressed is the potential movement of infected Culicoides via transport and trade networks. Therefore, a risk assessment model was constructed to assess the probability of a BTV outbreak as a consequence of the introduction of Culicoides via these networks. The model was applied to calculate the risk for a BTV-8 epidemic in Spain in 2007 caused by the introduction of Culicoides from affected northern European countries. The mean weighted annual risk for an outbreak caused by transportation of a single vector from an affected northern European country varied from 1.8 × 10(-7) to 3.0 × 10(-13), with the highest risks associated with Culicoides imported from Belgium, the Netherlands, Germany and France. For this mechanism to pose a significant risk to BTV-free countries, a large number of vectors would have to be transported.

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

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.

Comparison of bovine cysticercosis prevalence detected by antigen ELISA and visual inspection in the North East of Spain.

A cross-sectional serological study on cattle less than 2 years old, using an antigen ELISA for the detection of bovine cysticercosis was carried out between November 2009 and February 2010 in 10 slaughterhouses from the Catalonia region (North-Eastern Spain). Circulating antigen was detected in 23 of 2073 animals, i.e. a sero-prevalence of 1.11% (CI95%: 0.76-1.75%). The determined sero-prevalence was about 50 times higher than the prevalence obtained by visual inspection within the same period: 19 positive animals of 90,891 slaughtered animals (0.02%) in the same slaughterhouses. None of the animals with positive result in the Ag-ELISA was detected by meat inspection.

Analysis of the spatial variation of Bovine tuberculosis disease risk in Spain (2006-2009).

In this study we explored the spatial variation of Bovine tuberculosis (BTB) risk of being positive, new positive or persistently positive, as well as the risk of eliminating BTB in positive herds throughout Spain from 2006 to 2009 by means of hierarchical Bayesian models. The results of the models showed that the risk of infection (positive or new positive herds), persistence and elimination was lower in counties located in north and north-eastern of Spain, and in the Balearic and Canary islands than in the rest of the country. In some counties the risk of positivity was high during the four years of study, whereas there were others where the risk of positivity was high only in some of the years. With regard to the risk of persistence of BTB positive herds, counties located in the central, western and south-western part of the country had a higher risk in the three studied periods. This study has identified some specific areas of increased BTB risk in Spain, information that is useful for disease management.

Quantitative assessment of the probability of bluetongue virus transmission by bovine semen and effectiveness of preventive measures.

Given that bluetongue (BT) may potentially be transmitted by semen, that the disease has significantly expanded in recent years, and that millions of doses of cattle semen are annually traded throughout the world, the transmission of bluetongue virus (BTV) by semen could have severe consequences in the cattle industry. The hypothesis that infected bulls could excrete BTV in their semen led to restrictions on international trade of ruminant semen and the establishment of measures to prevent BTV transmission by semen. However, neither the risk of BTV transmission by semen nor the effectiveness of these measures was estimated quantitatively. The objective of the study was to assess, in case of introduction of BTV into a bovine semen collection centre (SCC), both the risk of BTV transmission by bovine semen and the risk reduction achieved by some of the preventive measures, by means of a stochastic risk assessment model. The model was applied to different scenarios, depending on for example the type of diagnostic test and the interval between the controls (testing) of donor bulls, or the rate of BTV spread within the SCC. Enzyme-linked immunosorbant assay (ELISA) controls of donor bulls every 60 days seemed to be an ineffective method for reducing the risk of BTV transmission in contrast to polymerase chain reaction (PCR) tests every 28 days. An increase in the rate of spread within the SCC resulted in a reduced risk of BTV transmission by semen. The storage of semen for 30 days prior to dispatch seemed to be an efficient way of reducing the risk of transmission by semen. The sensitivity analysis identified the probability of BTV shedding in semen as a crucial parameter in the probability of BTV transmission by semen. However, there is a great degree of uncertainty associated with this parameter, with significant differences depending on the BTV serotype.

Assessment of different surveillance systems for avian influenza in commercial poultry in Catalonia (North-Eastern Spain).

Compulsory surveillance programmes for avian influenza (AI) have been implemented in domestic poultry and wild birds in all the European Member States since 2005. The implementation of these programmes is complex and requires a close evaluation. A good indicator to assess their efficacy is the sensitivity (Se) of the surveillance system. In this study, the sensitivities for different sampling designs proposed by the Spanish authorities for the commercial poultry population of Catalonia were assessed, using the scenario tree model methodology. These samplings were stratified throughout the territory of Spain and took into account the species, the types of production and their specific risks. The probabilities of detecting infection at different prevalences at both individual and holding level were estimated. Furthermore, those subpopulations that contributed more to the Se of the system were identified. The model estimated that all the designs met the requirements of the European Commission. The probability of detecting AI circulating in Catalonian poultry did not change significantly when the within-holding design prevalence varied from 30% to 10%. In contrast, when the among-holding design prevalence decreased from 5% to 1%, the probability of detecting AI was drastically reduced. The sampling of duck and goose holdings, and to a lesser extent the sampling of turkey and game bird holdings, increased the Se substantially. The Se of passive surveillance in chickens for highly pathogenic avian influenza (HPAI) and low pathogenicity avian influenza (LPAI) were also assessed. The probability of the infected birds manifesting apparent clinical signs and the awareness of veterinarians and farmers had great influence on the probability of detecting AI. In order to increase the probability of an early detection of HPAI in chicken, the probability of performing AI specific tests when AI is suspected would need to be increased.

Monitoring bluetongue disease (BTV-1) epidemic in southern Spain during 2007.

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. Median morbidity rate in sheep and goat flocks were 6.3% and 2.7% respectively. Median mortality rate was 2.2% in sheep flocks and 1.2% in goat flocks. Median case fatality rate was 29.8% in sheep flocks and 45% in goat flocks. Morbidity and mortality rates were not significantly higher in sheep flocks than in goat flocks (p>0.05), whereas case fatality rate was significant higher in goat flocks compared to sheep flocks (p<0.05). Neither clinical signs nor mortality were observed in cattle herds. The spatial distribution of the risk of BTV infection over Andalusia by municipality was evaluated by means of a hierarchical Bayesian model. The results evidenced that the risk was not homogeneous over the territory, being higher in the western part of the region. The likelihood of BTV infection was increased between 1.01 and 1.16 times by an increase of 10,000 domestic ruminants, and between 1.01 and 1.69 times by the presence of red deer (Cervus elaphus) in the municipality.