Pelayo Acevedo

Disease risks and overabundance of game species

Different studies have evidenced the relationship between host abundance and health status of wildlife populations. Diseases that benefit from wildlife overabundance can affect not only the fitness and trophy quality of game species, but also public health, livestock health, and the conservation of endangered species. This paper reviews a number of European examples to highlight the relationship between overabundance and disease in game species, and discusses the possibilities of limiting the associated risks. Management tools to estimate overabundance are needed for legislative purposes and for the monitoring of wildlife populations, but artificial feeding interferes in the objective measurement of overabundance. Therefore, we propose a multidisciplinary approach to diagnose if a given wildlife population is overabundant. This includes not only signs such as adverse effects on the soil, vegetation or fauna (first group), poor body condition scores, low trophy scores or low reproductive performance (second group), or increased parasite burdens (third group), but also the measurement of infectious disease prevalences (the fourth group of overabundance signs). This combined assessment of overabundance ideally requires the cooperation of wildlife managers, botanists, and veterinarians. Once a given wildlife population is defined as overabundant, it is difficult to establish palliative management actions. These can consist in banning certain management tools (e.g. feeding) or increasing the hunting harvest, but both of them are difficult to implement in practice. A close monitoring of both wildlife densities and wildlife diseases, the establishment of reference values for all signs of overabundance, and the mapping of the disease and density hotspots will be needed to design adequate risk-control measures for each particular situation.

Estimation of European wild boar relative abundance and aggregation: a novel method in epidemiological risk assessment

Wild boars are important disease reservoirs. It is well known that abundance estimates are needed in wildlife epidemiology, but the expense and effort required to obtain them is prohibitive. We evaluated a simple method based on the frequency of faecal droppings found on transects (FBII), and developed a spatial aggregation index, based on the runs test statistic. Estimates were compared with hunting data, and with porcine circovirus and Aujeszkys disease virus seroprevalences and Mycobacterium tuberculosis complex and Metastrongylus spp. prevalence. The FBII and the aggregation index were correlated with the hunting index, but both of the former estimates correlated better than the latter with the disease prevalences. Hence, at least in habitats with high wild boar densities, the FBII combined with the aggregation index constitutes a cheap and reliable alternative for wild boar abundance estimation that can be used for epidemiological risk assessment, even outside the hunting season and in areas with no available data on hunting activities.

Bovine Tuberculosis in Doñana Biosphere Reserve: The Role of Wild Ungulates as Disease Reservoirs in the Last Iberian Lynx Strongholds

Doñana National Park (DNP) in southern Spain is a UNESCO Biosphere Reserve where commercial hunting and wildlife artificial feeding do not take place and traditional cattle husbandry still exists. Herein, we hypothesized that Mycobacterium bovis infection prevalence in wild ungulates will depend on host ecology and that variation in prevalence will reflect variation in the interaction between hosts and environmental risk factors. Cattle bTB reactor rates increased in DNP despite compulsory testing and culling of infected animals. In this study, 124 European wild boar, 95 red deer, and 97 fallow deer were sampled from April 2006 to April 2007 and analyzed for M. bovis infection. Modelling and GIS were used to identify risk factors and intra and inter-species relationships. Infection with M. bovis was confirmed in 65 (52.4%) wild boar, 26 (27.4%) red deer and 18 (18.5%) fallow deer. In the absence of cattle, wild boar M. bovis prevalence reached 92.3% in the northern third of DNP. Wild boar showed more than twice prevalence than that in deer (p<0.001). Modelling revealed that M. bovis prevalence decreased from North to South in wild boar (p<0.001) and red deer (p<0.01), whereas no spatial pattern was evidenced for fallow deer. Infection risk in wild boar was dependent on wild boar M. bovis prevalence in the buffer area containing interacting individuals (p<0.01). The prevalence recorded in this study is among the highest reported in wildlife. Remarkably, this high prevalence occurs in the absence of wildlife artificial feeding, suggesting that a feeding ban alone would have a limited effect on wildlife M. bovis prevalence. In DNP, M. bovis transmission may occur predominantly at the intra-species level due to ecological, behavioural and epidemiological factors. The results of this study allow inferring conclusions on epidemiological bTB risk factors in Mediterranean habitats that are not managed for hunting purposes. Our results support the need to consider wildlife species for the control of bTB in cattle and strongly suggest that bTB may affect animal welfare and conservation.

Factors affecting wild boar abundance across an environmental gradient in Spain

The recent Europe-wide increase in wild boarSus scrofa, Linnaeus, 1758 abundance is undoubtedly due to many different factors, the relative importance of which differs from region to region. In Aragón (northeastern Spain), wild boar enlarged its distribution area eight times in the 1990s as compared with the century before, occupying the whole region. We studied wild boar abundance along an environmental gradient in Aragón to determine which factors are most responsible for its variation. Relative abundance of wild boars was estimated by catch-effort methods in 134 hunting estates (sampling units) for 5 consecutive hunting seasons. To characterise the environmental conditions, we quantified landscape composition and structure, topographical factors and climatic factors. Hunting pressure indices were also calculated for our sampling units. The average wild boar catch per hunting activity and per 100 km2 ranged from 0.72 to 16.31. Our results suggest thatwild boar abundances are affected by landscape structure, mainly by landscape diversity. In addition, lowland arid agrosystems (characterized by high temperatures and open juniper woodlands with little food availability) constrain the abundance of wild boar populations in spite of their wide plasticity to colonize new habitats.

Spatial distribution and risk factors of Brucellosis in Iberian wild ungulates

BackgroundThe role of wildlife as a brucellosis reservoir for humans and domestic livestock remains to be properly established. The aim of this work was to determine the aetiology, apparent prevalence, spatial distribution and risk factors for brucellosis transmission in several Iberian wild ungulates.MethodsA multi-species indirect immunosorbent assay (iELISA) using Brucella S-LPS antigen was developed. In several regions having brucellosis in livestock, individual serum samples were taken between 1999 and 2009 from 2,579 wild bovids, 6,448 wild cervids and4,454 Eurasian wild boar (Sus scrofa), and tested to assess brucellosis apparent prevalence. Strains isolated from wild boar were characterized to identify the presence of markers shared with the strains isolated from domestic pigs.ResultsMean apparent prevalence below 0.5% was identified in chamois (Rupicapra pyrenaica), Iberian wild goat (Capra pyrenaica), and red deer (Cervus elaphus). Roe deer (Capreolus capreolus), fallow deer (Dama dama), mouflon (Ovis aries) and Barbary sheep (Ammotragus lervia) tested were seronegative. Only one red deer and one Iberian wild goat resulted positive in culture, isolating B. abortus biovar 1 and B. melitensis biovar 1, respectively. Apparent prevalence in wild boar ranged from 25% to 46% in the different regions studied, with the highest figures detected in South-Central Spain. The probability of wild boar being positive in the iELISA was also affected by age, age-by-sex interaction, sampling month, and the density of outdoor domestic pigs. A total of 104 bacterial isolates were obtained from wild boar, being all identified as B. suis biovar 2. DNA polymorphisms were similar to those found in domestic pigs.ConclusionsIn conclusion, brucellosis in wild boar is widespread in the Iberian Peninsula, thus representing an important threat for domestic pigs. By contrast, wild ruminants were not identified as a significant brucellosis reservoir for livestock.

A Broad Assessment of Factors Determining Culicoides imicola Abundance: Modelling the Present and Forecasting Its Future in Climate Change Scenarios

Bluetongue (BT) is still present in Europe and the introduction of new serotypes from endemic areas in the African continent is a possible threat. Culicoides imicola remains one of the most relevant BT vectors in Spain and research on the environmental determinants driving its life cycle is key to preventing and controlling BT. Our aim was to improve our understanding of the biotic and abiotic determinants of C. imicola by modelling its present abundance, studying the spatial pattern of predicted abundance in relation to BT outbreaks, and investigating how the predicted current distribution and abundance patterns might change under future (2011–2040) scenarios of climate change according to the Intergovernmental Panel on Climate Change. C. imicola abundance data from the bluetongue national surveillance programme were modelled with spatial, topoclimatic, host and soil factors. The influence of these factors was further assessed by variation partitioning procedures. The predicted abundance of C. imicola was also projected to a future period. Variation partitioning demonstrated that the pure effect of host and topoclimate factors explained a high percentage (>80%) of the variation. The pure effect of soil followed in importance in explaining the abundance of C. imicola. A close link was confirmed between C. imicola abundance and BT outbreaks. To the best of our knowledge, this study is the first to consider wild and domestic hosts in predictive modelling for an arthropod vector. The main findings regarding the near future show that there is no evidence to suggest that there will be an important increase in the distribution range of C. imicola; this contrasts with an expected increase in abundance in the areas where it is already present in mainland Spain. What may be expected regarding the future scenario for orbiviruses in mainland Spain, is that higher predicted C. imicola abundance may significantly change the rate of transmission of orbiviruses.

Past, present and future of wild ungulates in relation to changes in land use

In recent decades, Mediterranean landscapes have been experiencing more rapid changes in land use than usual, which have affected the ecology of the species inhabiting this biodiversity hotspot. Some studies have assessed the effect of such changes on biodiversity, but most of these were diachronic studies of population dynamics, or synchronic studies of species habitat selection, whereas few studies have simultaneously taken into account temporal changes in habitat composition and changes in species distribution. This study analysed the effects of land-use changes on the distribution of wild ungulates (Capreolus capreolus, Capra pyrenaica, Cervus elaphus and Sus scrofa). Using favourability function and Markov chain analysis combined with cellular automata, we addressed the following objectives: (i) to examine the environmental determinants of ungulate distribution in the past (1960s) and present (1990s), (ii) to model land use for 2040 to forecast future species distributions and (iii) to assess the biogeographical differences between the above-mentioned study periods (past–present and present–future). Species favourability was predicted to be more widely distributed in the present than in the past, but this increase varied across species. Areas predicted to be favourable in the present should remain stable in the future, but in addition there will be more new favourable areas not previously occupied by these species. The results are discussed from the perspective of the socio-economic relevance of wild ungulates in relation to some unfavourable areas of Mediterranean regions.

Serosurvey of Aujeszky’s disease virus infection in European wild boar in Spain

Serum samples from 693 hunted wild boar (Sus scrofa) were analysed by means of a blocking ELISA technique, and the mean (se) prevalence of antibodies to Aujeszky’s disease virus was 44 (4) per cent. All the seropositive wild boar were from south central Spain, except for one from central Spain, close to the main positive area. In this area, where large game species are increasingly managed for hunting, the seroprevalence was affected by the type of management. More intensively managed populations had a higher prevalence than wild boar living in natural situations, and the seroprevalence increased with the age of the animals; the seroprevalence was higher in females in all age groups. The seroprevalence in males more than one year old peaked after the breeding season, whereas females of the same age had a higher and constant seroprevalence throughout the year.

Favourability: concept, distinctive characteristics and potential usefulness

The idea of analysing the general favourability for the occurrence of an event was presented in 2006 through a mathematical function. However, even when favourability has been used in species distribution modelling, the conceptual framework of this function is not yet well perceived among many researchers. The present paper is conceived for providing a wider and more in-depth presentation of the idea of favourability; concretely, we aimed to clarify both the concept and the main distinctive characteristics of the favourability function, especially in relation to probability and suitability, the most common outputs in species distribution modelling. As the capabilities of the favourability function go beyond species distribution modelling, we also illustrate its usefulness for different research disciplines for which this function remains unknown. In particular, we stressed that the favourability function has potential to be applied in all the cases where the probability of occurrence of an event is analysed, such as, for example, habitat selection or epidemiological studies.

The Iberian ibex is under an expansion trend but displaced to suboptimal habitats by the presence of extensive goat livestock in central Spain

In this paper an updated distribution of the Iberian ibex (Capra pyrenaica, Schinz 1838) in the central Spanish region of Castile–La Mancha is shown. The species is present in 19% of the study region, and in areas not cited so far in the literature. A detailed analysis of habitat suitability was also carried out, applying a␣new methodology, Ecological-Niche Factor Analysis, which uses presence data to␣build a habitat suitability map of a given species. As livestock activity is quite intense in the region, the presence of a potential competitor, the domestic goat (Capra hircus), was included in the analyses. Factors affecting ibex relative abundance were determined by means of a nested stepwise multiple regression, where livestock presence/absence was the nested factor. The presence of livestock has a negative effect on ibex relative abundance, causing the ibex to select areas of poor, sparse vegetation, cultivated lands and forests, whereas in the absence of livestock, the ibex is mainly present in pasture–scrub lands and non-cultivated lands. Conservation implications of these results are discussed in the context of a Mediterranean region where extensive livestock grazing systems abound.