Insights into the spatiotemporal dynamics of West Nile virus transmission in emerging scenarios.

The incidence of West Nile fever (WNF) is highly variable in emerging areas, making it difficult to identify risk periods. Using clinical case records has important biases in understanding the transmission dynamics of West Nile virus (WNV) because asymptomatic infections are frequent. However, estimating virus exposure in sentinel species could help achieve this goal at varying spatiotemporal scales. To identify the determinants of inter-annual variation in WNV transmission rates, we designed a 15-year longitudinal seroepidemiological study (2005-2020) in five environmentally diverse areas of southwestern Spain. We modeled individual annual area-dependent exposure risk based on potential environmental and host predictors using generalized linear mixed models. Further, we analyzed the weight of predictors on exposure probability by variance partitioning of the model components. The analysis of 2418 wild ungulate sera (1168 red deer - Cervus elaphus - and 1250 Eurasian wild boar - Sus scrofa) with a highly sensitive commercial blocking ELISA identified an average seroprevalence of 24.9% (95% confidence interval (CI): 23.2-26.7%). Antibody prevalence was slightly higher in wild boar (27.5%; CI: 25.1-30.1%) than in deer (22.2%; CI: 19.8-24.7%). We observed a spatial trend in exposure, with higher frequency in the southernmost areas and a slight, although area-dependent, increasing temporal trend. Host-related predictors were important drivers of exposure risk. The environmental predictor with the highest weight was annual cumulative precipitation, while temperature variations were also relevant but with less weight. We observed a coincidence of spatiotemporal changes in exposure with the notification of WNF outbreaks in horses and humans. That indicates the usefulness of wild ungulates as sentinels for WNV transmission and as models to understand its spatiotemporal dynamics. These results will allow the development of more accurate predictive models of spatiotemporal variations in transmission risk that can inform health authorities to take appropriate action.

Red deer reveal spatial risks of Crimean-Congo haemorrhagic fever virus infection.

Crimean-Congo haemorrhagic fever virus (CCHFV) continues to cause new human cases in Iberia while its spatial distribution and ecological determinants remain unknown. The virus remains active in a silent tick-animal cycle to which animals contribute maintaining the tick populations and the virus itself. Wild ungulates, in particular red deer, are essential hosts for Hyalomma ticks in Iberia, which are the principal competent vector of CCHFV. Red deer could be an excellent model to understand the ecological determinants of CCHFV as well as to predict infection risks for humans because it is large, gregarious, abundant and the principal host for Hyalomma lusitanicum. We designed a cross-sectional study, analysed the presence of CCHFV antibodies in 1444 deer from 82 populations, and statistically modelled exposure risk with host and environmental predictors. The best-fitted statistical model was projected for peninsular Spain to map infection risks. Fifty out of 82 deer populations were seropositive, with individual population prevalence as high as 88%. The highest prevalence of exposure to CCHFV occurred in the southwest of the Iberian Peninsula. Climate and ungulate abundance were the most influential predictors of the risk of exposure to the virus. The highest risk regions were those where H. lusitanicum is most abundant. Eight of the nine primary human cases occurred in or bordering these regions, demonstrating that the model predicts human infection risk accurately. A recent human case of CCHF occurred in northwestern Spain, a region that the model predicted as low risk, pointing out that it needs improvement to capture all determinants of the CCHFV infection risk. In this study, we have been able to identify the main ecological determinants of CCHFV, and we have also managed to create an accurate model to assess the risk of CCHFV infection.

Assessing red deer hunting management in the Iberian Peninsula: the importance of longitudinal studies.

Understanding the dynamics of a wildlife population in relation to hunting strategies is essential to achieve sustainable management. We used monitoring data over 25 years from two red deer (Cervus elaphus) populations with different management (with and without supplemental feeding) in South Central Spain to: (i) characterise the density dependence of population dynamics under contrasted management, and (ii) provide the basis for sustainable extraction by considering the theoretical maximum sustainable yield (MSYt) as the reference. The red deer population displayed a typical management reactive culling approach ('saw-tooth-like' curves), with occasional strong annual harvests but not occurring on a regular basis. Interestingly, we found reduced population growth at high densities in both populations, indicating that density-mediated factors determined population growth even when artificial feeding was provided. However, no effects of sex not age class of the extracted population on the population growth rate were determined. The total number of animals hunted was only slightly above those predicted by MSYt (i.e. K 50%) in both populations, despite high densities close to theoretical K, being consistent throughout the study period. The extraction rates (30.3 and 34.0%, for supplemented and unsupplemented populations, respectively) were 13.3% and 10.2% lower compared to the MSYt situation in the unsupplemented and supplemented populations, respectively. Long term population monitoring data provided feasible and suitable baseline values to optimise the sustainable exploitation of red deer populations in the Mediterranean ecosystem under these contrasting management scenarios. Adaptive management, involving objective-driven decision making informed by data on red deer population dynamic, can contribute (i) to maximising the total extraction over the long term while (ii) reducing the ecological impact of high population densities.

Quality of main types of hunted red deer meat obtained in Spain compared to farmed venison from New Zealand.

Deer venison is increasingly valued as a natural meat. This study examines the three main sources of venison: farmed venison from New Zealand (NZ), the world's leading producer, and wild deer from Spain (SP), the second largest producer, which mainly supplies venison from traditional autumn-winter driven hunts (monteria), involving packs of dogs, and a smaller proportion culled through summer selective stalking. Meat from NZ contained more protein, lower shear force and lower n-6/n-3 ratio (P < 0.01). Spanish meat had a greater content of total, essential and non-essential amino acids (P < 0.01). Meat from deer culled in winter had lower intramuscular fat and saturated fatty acids (FA) but higher polyunsaturated FA (P < 0.01) and pH (P < 0.001) than meat from summer stalked deer. Therefore, venison presents differences by country of origin for composition, FA and texture that are likely to affect its health characteristics. Anomalies observed in meat between the winter driven hunt and non-stressful summer stalking may be attributed to the level of death stress in the case of variables such as pH. However, the effect on fat and mineral composition seems to be seasonal, depending respectively on wild diet or cyclic osteoporosis in males.

Sex-biased differences in the effects of host individual, host population and environmental traits driving tick parasitism in red deer.

The interactions between host individual, host population, and environmental factors modulate parasite abundance in a given host population. Since adult exophilic ticks are highly aggregated in red deer (Cervus elaphus) and this ungulate exhibits significant sexual size dimorphism, life history traits and segregation, we hypothesized that tick parasitism on males and hinds would be differentially influenced by each of these factors. To test the hypothesis, ticks from 306 red deer-182 males and 124 females-were collected during 7 years in a red deer population in south-central Spain. By using generalized linear models, with a negative binomial error distribution and a logarithmic link function, we modeled tick abundance on deer with 20 potential predictors. Three models were developed: one for red deer males, another for hinds, and one combining data for males and females and including "sex" as factor. Our rationale was that if tick burdens on males and hinds relate to the explanatory factors in a differential way, it is not possible to precisely and accurately predict the tick burden on one sex using the model fitted on the other sex, or with the model that combines data from both sexes. Our results showed that deer males were the primary target for ticks, the weight of each factor differed between sexes, and each sex specific model was not able to accurately predict burdens on the animals of the other sex. That is, results support for sex-biased differences. The higher weight of host individual and population factors in the model for males show that intrinsic deer factors more strongly explain tick burden than environmental host-seeking tick abundance. In contrast, environmental variables predominated in the models explaining tick burdens in hinds.

Impact of major histocompatibility complex class II polymorphisms on Iberian red deer parasitism and life history traits.

Host genetic diversity plays an important role in buffering populations against pathogens. We characterized the allelic diversity at the second exon of the b (DRB-2) chain of the major histocompatibility complex class II (MHC-II) locus in a population of Iberian red deer (Cervus elaphus hispanicus) and its impact on parasitism by macroparasites, on a microparasite causing tuberculosis, and on relevant life history traits (spleen size and body condition). No DRB-2 haplotype conferred general resistance or susceptibility against all parasites. However, specific significant correlations were found between some DRB-2 haplotypes and specific parasites. We also detected associations between DRB-2 haplotypes and body condition and spleen size after controlling for body size, sex and age. Our results evidenced a functional significance of MHC-II genes in the defence of Iberian red deer against parasites. These results also support a role of MHC-II as a fitness-enhancing genetic element which can be mediated by parasite effects on life traits with a genetic basis. We conclude that MHC immunogenetic studies may assess management decisions in Iberian red deer because (i) loss of genetic diversity may lead to increased disease occurrence, and (ii) MHC genes are ecologically relevant since they underlie host infection rates and life history traits.

Seasonal dynamics of the fecal excretion of Elaphostrongylus cervi (Nematoda, Metastrongyloidea) first-stage larvae in Iberian red deer (Cervus elaphus hispanicus) from southern Spain.

Elaphostrongylus cervi (Nematoda, Metastrongyloidea) is an extrapulmonary lungworm of red deer (Cervus elaphus) whose first-stage larvae (L1) require terrestrial gastropods as intermediate hosts. The seasonal pattern of fecal excretion of E. cervi L1 in Iberian red deer (Cervus elaphus hispanicus) was monitored during three annual periods (June 2000-May 2003) on a hunting estate from south-central Spain. The lowest rates of mean intensity of fecal L1 were found in summer, whereas no seasonal variation was found for prevalence. Monthly intensity of excretion was positively associated with early rainfall (the next month) rather than with rainfall of the same month. This seasonal rhythm of E. cervi L1 discharge may be the result of parasite adaptation to the seasonal Mediterranean climate and habitat constraints to improve the chance of parasite transmission. We have standardized the sampling period to compare E. cervi L1 infection rates of Iberian red deer populations in Mediterranean Spain, a natural limit of both the parasite and deer historical ranges, for potential use in the assessment of management strategies.

Efficacy of an in-feed preparation of ivermectin against helminths in the European wild boar.

The wild boar is one of Europe's most popular game species and its densities are increasing. Management tools such as farm breeding, supplementary feeding, and translocations are more frequently employed and anthelmintics are increasingly used in game farms and translocations. Here, we report the results of a controlled slaughter study on the efficacy of an in-feed preparation of ivermectin in European wild boars naturally infected with various helminths. The efficacy of ivermectin against adult stages of Metastrongylus sp., Ascaris suum, Ascarops strongylina, Physocephalus sexalatus, and Simondsia paradoxa was 100%. Its efficacy against Oesophagostomum dentatum was 85.1%. There was no sufficient effect on Globocephalus urosubulatus, Trichuris suis, and Capillaria garfiai. The egg reduction in the treated group ( n=12) was 100% 6 days after the treatment. The importance of parasite surveillance and the application of anthelmintic treatments to wild boars in game farms or during translocations are discussed. We conclude that any attempt at helminth treatment in wild boars should consider the addition of a second compound with a more consistent effect on trichurids and other helminths.

Wild boar helminths: risks in animal translocations.

The helminth populations found in a group of wild boars collected in central Spain were compared to those in a group of animals imported from a French game farm that produces boars for restocking. Eleven helminth species, including ten nematodes and one acanthocephalan, were found. Gongylonema pulchrum and Macracanthorhynchus hirundinaceus were only detected in autochthonous wild boars, while Oesophagostomum dentatum, Ascaris suum, and Trichuris suis were detected in imported animals only. Autochthonous wild boars were more frequently and more intensely parasitised by Ascarops strongylina than the imported ones. No differences in prevalence nor intensity were found for the species Capillaria garfiai, Globocephalus urosubulatus, Metastrongylus sp., Physocephalus sexalatus and Simondsia paradoxa. To our knowledge, G. urosubulatus, G. pulchrum and S. paradoxa have not previously been described in wild boars in Spain. Our results highlight the risks of translocating wild animals, with regard to their helminth parasites. Until improved control measures are established, it would be wise to avoid long-distance translocations in order to prevent the potential introduction of foreign parasites.