Similar antibody response observed in single-dose-vaccination vs. revaccination against Aujeszky's disease in wild boar

Wild boar is an important reservoir of Aujeszky's disease virus (ADV). There is concern that transmission of this virus from wild boar to domestic pigs is possible. The aim of this work was to compare the antibody response produced by single dose of a gE-deleted ADV vaccine in wild boar to revaccinated animals, to assess if simple single-dose vaccination plans should be examined as a possible control measure against ADV in wild boar. Twenty-five wild boar (ages ranging between 2.5 to 5 months) were included in this study and distributed in three different groups: a control group (n = 5), a single-dose group (10 animals vaccinated only with one dose (day 0)) and a revaccinated group [10 animals vaccinated (day 0) and revaccinated (day 28)]. Mean antibody titers against ADV were determined in three groups using an ELISA assay at three different time points [day 0 (pre-vaccination), 28 (post 1st dose) and 56 (post 2nd dose)]. At day 28, single-dose and revaccinated groups showed a significant increment of antibody titers whereas antibodies in the control group remained stable. At day 56, revaccinated animals did not show a significant increment and antibody titers were similar to those found in animals vaccinated with one dose. These results indicate that vaccination with one dose produces a similar early antibody response to revaccination and therefore, should be examined as a possible control measure against ADV in wild boar. Keywords: Aujeszky's disease; serology; vaccination; wild boar.

Influence of porcine circovirus type 2 infections on bovine tuberculosis in wild boar populations

The wild boar is an important reservoir of bovine tuberculosis (bTB) in south-western Spain. Some risk factors such as wild boar density or age have been associated with the presence of high prevalences of bTB in wild boar. However, the influence of other risk factors such as co-infections with other pathogens has not yet been studied. This work aims to assess the influence of porcine circovirus type 2 (PCV-2) infection on bTB prevalence and bTB lesional patterns observed in wild boar. The presence of bTB-like lesions was evaluated in 551 hunted wild boar from 11 different game estates in south-western Spain, with a known history of bTB. Tuberculosis prevalences in each estate were calculated based on the percentage of animals found with bTB-like lesions. The percentage of animals with generalized bTB lesional patterns (bTB lesions in more than one organ) was also assessed. The prevalence of PCV-2 was studied in each estate using a specific PCR assay. The relationship between PCV-2 and bTB prevalences and between PCV-2 infections and the presence of generalized lesional patterns in wild boar were analysed. A statistical relationship between the prevalences of bTB and PCV-2 was found, with bTB prevalences being higher in estates where prevalences of PCV-2 were high. On the other hand, animals infected with PCV-2 were more likely to develop a generalized lesional pattern. Porcine circovirus type 2 prevalences seem to be associated with prevalences of bTB in wild boar. PCV-2 infection may aggravate the development and severity of bTB, favouring the presence of generalized lesional patterns and raising the risk of contagion in these estates. The implementation of sanitary measures that focus on the control of PCV-2 infection may be necessary as a preliminary measure in bTB control programmes for wild boar.

Non-tuberculous mycobacteria in wild boar (Sus scrofa) from Southern Spain: epidemiological, clinical and diagnostic concerns

Non-tuberculous mycobacteria (NTM) are widely distributed in the environment, particularly in wet soil, marshland, rivers or streams, but also are causative agents of a wide variety of infections in animals and humans. Little information is available regarding the NTM prevalence in wildlife and their effects or significance in the bovine tuberculosis (bTB) epidemiology and diagnosis. This research shows the most frequently NTM isolated in lymph nodes of wild boar (Sus scrofa) from southern Spain, relating the NTM presence with the individual characteristics, the management of animals and the possible misdiagnosis of Mycobacterium bovis in concurrent infections. A total of 219 NTM isolates were obtained from 1249 wild boar mandibular lymph nodes sampled between 2007 and 2011. All but 75 isolates were identified by the PCR-restriction analysis-hsp65, and a partial sequencing of the 16S rDNA was carried out to identify the rest of the isolates. Results showed that Mycobacterium chelonae was the most frequently isolated NTM specie (133 isolates, 60.7%), followed by Mycobacterium avium (24 isolates, 11%). No relation was found regarding sex, body condition and management, but M. chelonae was more frequently detected in adults, whereas M. avium was more prevalent in subadults. The high NTM prevalence observed in the studied wild boar populations could make difficult the bTB diagnostic.

Reducing Eurasian wild boar (Sus scrofa) population density as a measure for bovine tuberculosis control: effects in wild boar and a sympatric fallow deer (Dama dama) population in Central Spain

Research on management of bovine tuberculosis (bTB) in wildlife reservoir hosts is crucial for the implementation of effective disease control measures and the generation of practical bTB management recommendations. Among the management methods carried out on wild species to reduce bTB prevalence, the control of population density has been frequently used, with hunting pressure a practical strategy to reduce bTB prevalence. However, despite the number of articles about population density control in different bTB wildlife reservoirs, there is little information regarding the application of such measures on the Eurasian wild boar (Sus scrofa), which is considered the main bTB wildlife reservoir within Mediterranean ecosystems. This study shows the effects of a management measure leading to a radical decrease in wild boar population density at a large hunting estate in Central Spain, in order to assess the evolution of bTB prevalence in both the wild boar population and the sympatric fallow deer population. The evolution of bTB prevalence was monitored in populations of the two wild ungulate species over a 5-year study period (2007-2012). The results showed that bTB prevalence decreased in fallow deer, corresponding to an important reduction in the wild boar population. However, this decrease was not homogeneous: in the last season of study there was an increase in bTB-infected male animals. Moreover, bTB prevalence remained high in the remnant wild boar population.

Comparative pathology of the natural infections by Mycobacterium bovis and by Mycobacterium caprae in wild boar (Sus scrofa)

The potential role of wild animals in the maintenance and spread of tuberculosis (TB) infection in domestic livestock is of particular importance in countries where eradication programs have substantially reduced the incidence of bovine tuberculosis but sporadic outbreaks still occur. Mycobacterium bovis is the agent mainly isolated in wildlife in Spain, but recently, infections by Mycobacterium caprae have increased substantially. In this study, we have analysed 43 mandibular lymph nodes samples containing TB-like lesions from 43 hunted wild boar from Madrid and Extremadura (central and south-western regions of Spain). After isolation, identification and typing of Mycobacterium tuberculosis complex isolates, we found that 23 mandibular lymph nodes involved M. caprae infections and 20 M. bovis. The lesions were compared for histopathology (different granuloma stage and number of multinucleated giant cells (MNGCs)), and acid-fast bacilli (AFBs) were quantified in the Ziehl-Neelsen-stained slides. Granulomas produced by M. caprae showed more stage IV granulomas, more MNGCs and higher AFBs counts than those induced by M. bovis. In conclusion, lesions caused by M. caprae would be more prone to the excretion of bacilli, and infected animals result as a high-risk source of infection for other animals.

Management practices and their association with Mycobacterium tuberculosis complex prevalence in red deer populations in Southwestern Spain

Intensification of game management may increase the prevalence of tuberculosis (TB) in wildlife despite eradication programs implemented in cattle herds in the same areas. In this cross-sectional study, we investigated the association between wild game management practices and the presence of tuberculosis in red deer populations in Southwestern Spain. Five hundred and fifty-one animals were examined by necropsy to detect tuberculosis-like lesions in the main lymph nodes. Prevalence, as determined by TB-like lesions, was estimated to be 5.1% of animals, with 77% of TB-like lesions confirmed by PCR. Our results suggest that population density, in addition to factors which promote the local aggregation of animals, is factors associated with increased prevalence of TB in red deer populations. We suggest that management practices including supplementary feeding, fencing, water ponds and interaction with domestic livestock should be revised in order to prevent TB in wild deer both.

Bovine tuberculosis in wild boar (Sus scrofa), red deer (Cervus elaphus) and cattle (Bos taurus) in a Mediterranean ecosystem (1992–2004)

During the last 12 years, an increasing frequency in condemnation of hunted red deer and wild boar carcasses due to the presence of tubercle-like lesions has been observed in Extremadura (Western Spain). Before 1993, tuberculosis was a very rare finding in hunted animals. The current tuberculosis regional prevalence in cattle approaches 0.4% after years of expensive test and slaughter campaigns. It is imperative to investigate the epidemiology of Mycobacterium bovis infection in red deer and wild boar in order to keep a good health status and to maintain the effectiveness of domestic species TB eradication programs. The present paper evaluates the problem in Sierra de San Pedro, estimating the prevalence of TB in wild boar and red deer, the main wild artiodactyls in the area, and domestic cattle since 1992-2004, by the use of a low-cost surveillance method based on detailed pathological inspection of hunted animal carcasses. Microbiology and molecular epidemiology studies on several M. bovis isolates from domestic and wild animals helped to define the interspecies contacts. These findings, as well as recent history of game estates management and descriptive epidemiology field work, throw light on the rise and maintenance of these epizootics.

Epidemiology of Mycobacterium bovis infections of pigs and wild boars using a molecular approach

A molecular epidemiological approach was applied to establishing a possible role for the wild boar as a natural reservoir of Mycobacterium bovis in Sierra de Villuercas, Western Spain; an area free of farmed cattle and wild deer populations. Spoligo and VNTR typing were used over a three year period to study the epidemiological relationship between the occurrence of bovine tuberculosis (TB) in extensively bred Iberian pigs and indigenous wild boar. The 37 sampled wild boar showed different degree of calcified granulomatous lesions in retropharyngeal, mediastinal and pulmonary lymph nodes. The 25 sampled Iberian pigs showed calcified lesions, mainly in the respiratory tract. Lesions located in the mesenteric lymph nodes appeared secondarily. M. bovis was isolated from all affected animals. Twenty-five and 37 isolates of M. bovis were obtained from domestic pigs and wild boar, respectively. Our findings provide evidence that supports the possibility of cross infection between wild boar and domestic pig populations. This is contrary to the generally held belief that swine represent an epidemiological dead end host and play no role in the epidemiology of M. bovis.