Álvaro Oleaga

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.

New techniques for an old disease: Sarcoptic mange in the Iberian wolf

Sarcoptic mange, a parasitic skin infection caused by the burrowing mite Sarcoptes scabiei, has been reported in over 100 mammals, including humans. In endangered species, mange causes conservation concerns because it may decimate isolated populations and contribute to extinction. The Iberian Peninsula still maintains one of the largest wolf (Canis lupus) populations in Europe. In Iberia, sarcoptic mange is endemic in red foxes (Vulpes vulpes) and the first confirmed wolf mange cases were recently reported. However, knowledge on S. scabiei in wolves is scarce because of the sampling difficulties inherent to research on scarce species. In order to describe wolf mange epidemiology and to infer conservation implications, this study combined traditional laboratory techniques with the revision of wolf carcass pictures taken by field biologists and original information obtained by camera trapping. A total of 125 necropsies and 8783 camera-trap days allowed insights into wolf mange epidemiology between 2003 and 2010. Living Sarcoptes mites were detected in 19% of the fresh carcasses. Alopecic (delayed) type IV hypersensitive response reactions were observed, while parakeratotic lesions were infrequent. The number of mites isolated per wolf ranged from 1 to 78, and had a negative correlation with the percentage of alopecic skin. No effect by sex on mange prevalence was found. Yearlings showed a lower probability to present mange-compatible lesions than pups or adults. Wolves with mange-compatible lesions had a lower kidney fat index than apparently healthy ones. ELISA testing of 88 sera yielded an antibody prevalence of 20%. Photo-trapping recorded mange-compatible lesions since 2003 with a peak in 2008. The percentage of wolves with mange-compatible lesions registered in camera-traps during 1 year correlated with the percentage of red foxes with lesions in the previous year. This is the first large survey on sarcoptic mange in the Iberian wolf. Necropsy data, with alopecia as the main feature and a slight effect on body condition, and trends derived from camera trapping coincided in showing a rather low prevalence and an apparently stable situation of the disease and its host, suggesting that this parasite is currently not a major threat for this wolf population. However, more information is needed in order to assess the effect of mange on aspects such as pup survival.

Temporal stability in the genetic structure of Sarcoptes scabiei under the host-taxon law: empirical evidences from wildlife-derived Sarcoptes mite in Asturias, Spain.

BackgroundImplicitly, parasite molecular studies assume temporal genetic stability. In this study we tested, for the first time to our knowledge, the extent of changes in genetic diversity and structure of Sarcoptes mite populations from Pyrenean chamois (Rupicapra pyrenaica) in Asturias (Spain), using one multiplex of 9 microsatellite markers and Sarcoptes samples from sympatric Pyrenean chamois, red deer (Cervus elaphus), roe deer (Capreolus capreolus) and red fox (Vulpes vulpes).ResultsThe analysis of an 11-years interval period found little change in the genetic diversity (allelic diversity, and observed and expected heterozygosity). The temporal stability in the genetic diversity was confirmed by population structure analysis, which was not significantly variable over time. Population structure analysis revealed temporal stability in the genetic diversity of Sarcoptes mite under the host-taxon law (herbivore derived- and carnivore derived-Sarcoptes mite) among the sympatric wild animals from Asturias.ConclusionsThe confirmation of parasite temporal genetic stability is of vital interest to allow generalizations to be made, which have further implications regarding the genetic structure, epidemiology and monitoring protocols of the ubiquitous Sarcoptes mite. This could eventually be applied to other parasite species.

Spatio-temporal trends of Iberian wild boar contact with Mycobacterium tuberculosis complex detected by ELISA.

The continuing expansion of Eurasian wild boar (Sus scrofa) populations raises concerns regarding disease transmission. In south-central Spain, overabundant wild boar are reservoirs of Mycobacterium bovis, and related members of the Mycobacterium tuberculosis complex (MTBC), the causative agents of bovine tuberculosis (bTB). An indirect enzyme-linked immunosorbent assay using bovine-purified protein derivative was applied to determine the spatial and temporal distribution of wild boar contact with MTBC in the Iberian Peninsula and to model and identify the associated risk factors. Wild boar apparent seroprevalence was 22%. Seropositives were detected in 71% of 81 sites, including 23 sites where wildlife was thought to be bTB free. The results described a new geographic range of wild boar contact with MTBC and a stable prevalence in this wildlife reservoir that contrasts with the success of bTB control in cattle. Inference of which host (wild boar or cattle) is driving bTB maintenance was not possible with our correlational results. The possibility of a wild boar bTB emergence in non-endemic regions should urgently be taken into account to avoid a future scenario resembling the current situation in south-central Spain.

Serosurvey for selected pathogens in Iberian roe deer

BackgroundThe roe deer is the most abundant and widespread wild Eurasian cervid. Its populations are expanding and increasingly in contact with livestock. This may affect the distribution of infectious diseases shared with other wild and domestic ungulates.MethodsWe investigated the antibody seroprevalence against Pestivirus, Herpesvirus, Bluetongue (BT) virus, M. avium paratuberculosis (MAP), and Brucella sp. in 519 roe deer from different regions in Spain, south-western Europe.ResultsNo antibodies were detected against BT and Brucella sp. However, antibodies were detected against Pestivirus (1.5%), Herpesvirus (0.2%) and MAP (9.2%). MAP antibodies were detected in seven of the eight populations (range 5-16.4%).ConclusionsThe detection of MAP antibodies in samples from most roe deer populations suggests that contact with MAP is widespread in this wildlife species. The highest prevalence was detected in sites with abundant dairy cattle and frequent use of liquid manure on pastures. Considering the results obtained regarding exposure to different pathogens, we suggest that antibody prevalences in this non-gregarious browser are largely determined by environmental factors, potentially modulating vector populations or pathogen survival in the environment.

Prevalence of antibodies against selected agents shared between Cantabrian chamois (Rupicapra pyrenaica parva) and domestic goats.

Southern chamois (Rupicapra pyrenaica) share the habitat with domestic ungulates, and may, therefore, play a role in the epidemiology of shared agents. The objective of this study was to determine the seroprevalence for Brucella spp., Mycobacterium avium ssp. paratuberculosis (MAP), pestivirus, and Sarcoptes scabiei in Cantabrian chamois (Rupicapra pyrenaica parva) and compare these data with those of sympatric domestic goats (Capra hircus). From 2005 to 2008, blood samples were obtained from 236 adult Cantabrian chamois in two different populations, the western one and the eastern one. Seroprevalence for Brucella spp. and pestivirus was assessed using commercial ELISA kits, whereas specifically designed ELISA tests were used for MAP and S. scabiei. No antibodies against Brucella spp. were detected. Conversely, antibodies against MAP, pestivirus (chamois 3.8%; goat 2.3%), and S. scabiei (chamois 11.9%; goat 12.8%) were detected in both species. Seroprevalence for MAP was significantly higher for domestic goats (26%) than for chamois (9.7%). In chamois, seroprevalence for pestivirus was higher in the west (6.5%) than in the east (range 0–1.8%), whereas seroprevalence for S. scabiei followed the opposite trend (west 4.6%; east 16.7–21.4%). We suggest that certain diseases could circulate between Cantabrian chamois and domestic goat populations, and domestic livestock may suppose a threat for the health status of sympatric Cantabrian chamois.

Ecological preferences of exophilic and endophilic ticks (Acari: Ixodidae) parasitizing wild carnivores in the Iberian Peninsula.

Ticks parasitizing wild carnivores and the tick-borne pathogens (TBPs) that they transmit may affect domestic carnivores and humans. Thus, investigating the role of wild carnivores as tick hosts is of relevance for understanding the life cycle of ticks in natural foci and the epidemiology of TBPs shared with domestic animals and humans. Therefore, the main objective of this study was to determine the ixodid tick fauna of wild carnivores in Peninsular Spain and the environmental factors driving the risk of wild carnivores to be parasitized by ixodid ticks. We hypothesized that the adaptation of tick species to differing climatic conditions may be reflected in a similar parasitization risk of wild carnivores by ticks between bioclimatic regions in our study area. To test this, we surveyed ixodid ticks in wild carnivores in oceanic, continental-Mediterranean, and thermo-Mediterranean bioclimatic regions of Peninsular Spain. We analyzed the influence of environmental factors on the risk of wild carnivores to be parasitized by ticks by performing logistic regression models. Models were separately performed for exophilic and endophilic ticks under the expected differing influence of environmental conditions on their life cycle. We found differences in the composition of the tick community parasitizing wild carnivores from different bioclimatic regions. Modelling results partially confirmed our null hypothesis because bioclimatic region was not a relevant factor influencing the risk of wild carnivores to be parasitized by exophilic ticks. Bioclimatic region was however a factor driving the risk of wild carnivores to be parasitized by endophilic ticks. Spanish wild carnivores are hosts to a relevant number of tick species, some of them being potential vectors of pathogens causing serious animal and human diseases. Information provided herein can be of help to understand tick ecology in Spanish wildlife, the epidemiology of tick-borne diseases, and to prevent the risks of TBPs for wildlife, domestic animals, and humans.

Primary and secondary experimental infestation of rabbits (Oryctolagus cuniculus) with Sarcoptes scabiei from a wild rabbit: factors determining resistance to reinfestation.

Studies of sarcoptic mange and immunity are hampered by lack of mite sources and natural infestation models. We have investigated the clinical and pathological signs, specific IgG response and acquired immunity in naïve New Zealand White rabbits (Oryctolagus cuniculus) experimentally infested with Sarcoptes scabiei originally isolated from a clinically affected free-living European wild rabbit. Twenty rabbits were infested using two methods, direct contact for a 24 h period with a seeder rabbit simulating the natural process of infestation and application of a dressing holding approximately 1800 live mites on each hind limb (foot area) for a 24h period. Eight weeks post infestation, rabbits were treated with ivermectin and infestation cleared. Eight weeks later seventeen previously infested and four uninfested naïve controls were then re-exposed to the same S. scabiei variety using the same methods and followed for another 8 weeks. The progress of the disease was markedly more virulent in the animals infested by contact, indicating that the effective dose of mites managing to thrive and infest each rabbit by this method was higher. Nevertheless, infestation by contact resulted in partial protection to reexposure, rabbits developed high non-protective antibody titres upon reinfestation and presented severe clinical signs. However, rabbits reinfested by dressing developed lower IgG titres, and presented high levels of resistance to reinfestation, which might be due to induction of a strong local cellular response in the inoculation point that killed the mites and resulted in a lower mite effective dose, with subsequent reduced lesion development. Statistical analysis showed that sex, method of infestation and previous exposure are key factors determining the ability of rabbits to develop immunity to this disease. The rabbit-mange model developed will allow the further study of immunity and resistance to this neglected pathogen using a natural host system.

Large-scale serosurvey of Besnoitia besnoiti in free-living carnivores in Spain

The disease bovine besnoitiosis is responsible for severe economic losses caused by the protozoan Besnoitia besnoiti. The identity of the definitive host (DH) of this parasite has yet to be determined, although it is presumed to be a carnivore. With the aim of advancing in the identification of B. besnoiti DH, a necessary step in implementing control strategies, the contact rate of 205 free-roaming carnivores with this parasite in Spain was studied. The study included 16 wolves (Canis lupus), 41 red foxes (Vulpes vulpes), 21 pine martens (Martes martes), eight stone martens (M. foina), 12 Eurasian badgers (Meles meles), 18 common genets (Genetta genetta), five Egyptian mongooses (Herpestes ichneumon), 28 European wildcats (Felis silvestris silvestris), 43 feral cats (Felis silvestris catus), and 13 other animals belonging to five other species. Serum samples were analysed by an indirect fluorescent antibody test (IFAT) and by two western immunoblots (WB, one with tachyzoite and the other with bradyzoite antigen). Twelve individuals (eight of which were cats) seroconverted by one or other of these techniques but no individual showed seroconversion by IFAT and one of the WBs. The results provided no evidence to support the idea that within the geographical regions covered by the analysis wild carnivores are implicated in the transmission of B. besnoiti in Spain.

Patterns of Exposure of Iberian Wolves (Canis lupus) to Canine Viruses in Human-Dominated Landscapes.

Wildlife inhabiting human-dominated landscapes is at risk of pathogen spill-over from domestic species. With the aim of gaining knowledge in the dynamics of viral infections in Iberian wolves (Canis lupus) living in anthropized landscapes of northern Spain, we analysed between 2010 and 2013 the samples of 54 wolves by serology and polymerase chain reaction (PCR) for exposure to four pathogenic canine viruses: canine distemper virus (CDV), canine parvovirus-2 (CPV), canine adenovirus 1 and 2 (CAV-1 and CAV-2) and canine herpesvirus. Overall, 76% of the studied wolves presented evidence of exposure to CPV (96% by HI, 66% by PCR) and 75% to CAV (75% by virus neutralization (VN), 76% by PCR, of which 70% CAV-1 and 6% CAV-2). This represents the first detection of CAV-2 infection in a wild carnivore. CPV/CAV-1 co-infection occurred in 51% of the wolves. The probability of wolf exposure to CPV was positively and significantly correlated with farm density in a buffer zone around the place where the wolf was found, indicating that rural dogs might be the origin of CPV infecting wolves. CPV and CAV-1 appear to be enzootic in the Iberian wolf population, which is supported by the absence of seasonal and inter-annual variations in the proportion of positive samples detected. However, while CPV may depend on periodical introductions by dogs, CAV-1 may be maintained within the wolf population. All wolves were negative for exposure to CDV (by VN and PCR) and CHV (by PCR). The absence of acquired immunity against CDV in this population may predispose it to an elevated rate of mortality in the event of a distemper spill-over via dogs.