High prevalence of large spiny-tailed protostrongylid larvae in Iberian red deer

The First Report of Elaphostrongylus cervi Infection in Two Imported Wapitis (Cervus canadensis) in Slovenia

This study describes two female wapitis (Cervus canadensis) with neurological signs associated with an Elaphostrongylus cervi (E. cervi) infection. The original host of the nematode parasite is the Eurasian red deer (Cervus elaphus), although other cervids and small ruminants may also be affected. The two wapitis imported from Canada were kept in an enclosure with the Slovenian red deer herd. After developing debilitating neurological signs, the wapitis were euthanized and examined for possible causes. A histopathological examination of the brain of the first wapiti revealed severe diffuse perivascular meningoencephalitis with chronic vasculitis, and some cross-sections of nematodes were found in the leptomeninges. A necropsy of the second wapiti revealed severe pachymeningitis and leptomeningitis, where several adult nematode parasites were found. E. cervi was confirmed by molecular methods. The prevalence of E. cervi in the European red deer population is high, but no study has been conducted to assess its prevalence in Slovenia. This was the first confirmation of E. cervi in Slovenia and the first infection with this parasite described in Europe in a wapiti. Elaphostrongylus cervi should also be considered as a differential diagnosis in Europe for all ruminants grazing on pastures frequented by red deer and showing neurological clinical signs.

Divergent impacts of warming weather on wildlife disease risk across climates

Disease outbreaks among wildlife have surged in recent decades alongside climate change, although it remains unclear how climate change alters disease dynamics across different geographic regions. We amassed a global, spatiotemporal dataset describing parasite prevalence across 7346 wildlife populations and 2021 host-parasite combinations, compiling local weather and climate records at each location. We found that hosts from cool and warm climates experienced increased disease risk at abnormally warm and cool temperatures, respectively, as predicted by the thermal mismatch hypothesis. This effect was greatest in ectothermic hosts and similar in terrestrial and freshwater systems. Projections based on climate change models indicate that ectothermic wildlife hosts from temperate and tropical zones may experience sharp increases and moderate reductions in disease risk, respectively, though the magnitude of these changes depends on parasite identity.

Serum haptoglobin response in red deer naturally infected with tuberculosis

The analysis of haptoglobin (Hp) serum concentration is a very sensitive, but non-specific, indicator of inflammation or infection. Methods to accurately diagnose infection in vivo in wildlife are usually constrained by low sensitivity due to the effects of stress on individual immune response and the challenging logistics of performing tests in the wild. Firstly, we sought to determine serum Hp concentration in red deer (Cervus elaphus) naturally infected with bovine tuberculosis (TB). Secondly, we assessed the complementary diagnostic value of serum Hp levels in conjunction with the cervical comparative skin test (CCT) performed in a subsample (n = 33). Serum Hp concentrations were significantly higher in TB-infected individuals (based on the presence of macroscopic lesions confirmed by culture) compared to those uninfected. In addition, serum Hp significantly changed with the type of animal handling, with captured and handled animals showing higher levels of Hp than hunted animals. Four out of 6 TB positive individuals that tested negative to the CCT (false negatives) showed Hp levels higher than the 95th percentile of healthy animals. These findings indicate that an acute phase response develops in animals with TB. In this paper, we demonstrate for the first time that an acute phase protein can provide a complementary assessment for specific diagnosis tests in wild species.

Etiopathological aspects of Elaphostrongylus cervi and Varestrongylus sagittatus infections in red deer in Bulgaria

One hundred and ten faecal samples and five lungs of red deer (aged 2 to 8 years) coming from the State Hunting Enterprise Vitinya in Bulgaria (Balkan Mountain) were examined. A larvoscopic examination of the faeces and helminthological necropsies, pathoanatomical and histological examinations of the lungs were performed. The overall prevalence of protostrongylids was 70% (77/110), and the prevalence ofElaphostrongylus cerviandVarestrongylus sagittatuswas 68% (75/110), and 27% (30/110), respectively. In 25% (28/110) of the faecal samples, mixed infection withV. sagittatusandE. cerviwas found. Mixed protostrongylid infections with those two species were detected in lungs of all animals. The macroscopic lesions found in the lungs parasitized by those helminths were classified as follows: gray, dark-red to black stained portions on the lungs surface varying in shape and size; brown-black nodes clearly differentiated from the surrounding tissue; small, hard subserous nodules. The most frequently observed microscopic abnormalities were desquamatous bronchitis, alveolitis associated with accumulations of alveolar macrophages and eosinophilic granulocytes, haemorrhages in the alveoli and the alveolar septa, development of parasitic granulomas in the interstitium as well as a peribronchial, perilobular, disseminated and intralobular hyperplasia of the lymphoid tissue. The macroscopic and microscopic alterations depended on the species of the parasites found in the inflammatory areas. The infections withE. cerviwere most often associated with the lesions on the lungs surface varying in color, shape and size and with the small, hard subserous nodules, and those withV. sagittatus– with the brown-black nodes clearly differentiated from the surrounding tissue.

Elaphostrongylus cervi in a population of red deer (Cervus elaphus) and evidence of cerebrospinal nematodiasis in small ruminants in the province of Varese, Italy

Thirty-one faecal samples were collected from red deer in the northern area of Varese, in the Italian region of Lombardy, between August and October 2008. The animals had either been hunted or accidently killed. Examination for internal parasites showed a prevalence of 45.2% for Elaphostrongylus cervi larvae and species identification was confirmed by polymerase chain reaction (PCR). Ninety-seven faecal samples were also collected from two goat flocks grazing in the same area between December 2007 and May 2008. These showed a prevalence of 74.7% for lungworms. Furthermore, the central nervous systems from five goats and one sheep from this area with a history of neurologically related lameness were examined. Histopathology confirmed E. cervi cerebro-spinal nematodiasis in five cases out of six. This study demonstrates E. cervi transmission from wild to domestic ruminants when the animals graze in the same area, and the possible occurrence of clinical disease in infected goats and sheep associated with high prevalence in deer.

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.

What does testosterone do for red deer males?

Testosterone has been proposed to have a dual effect, enhancing sexual traits while depressing parasite resistance in males. Here, we test this hypothesis in red deer, examining males from captive populations during the whole annual cycle and males from natural populations during the breeding season. We first explored the effects of body size, age and sampling date on testosterone to avoid confounding effects. Our results show that in captive populations seasonal changes in testosterone levels were mirrored by changes in testes size, and that during the rut there was a strong correlation between both. In natural populations, males with higher testosterone levels had larger testes, improved sperm quality, smaller burr diameter, stronger antlers, higher haematocrit levels, and increased nematode parasite load. By contrast, no significant relationship was found between testosterone and spleen size or tick parasite load. We conclude that testosterone (i) improves males' reproductive investment and physical stamina, (ii) improves antler strength but reduces burr diameter, and (iii) imposes a cost in terms of depressed parasite resistance.

Minimum sampling effort for reliable non-invasive estimations of excretion abundance of Elaphostrongylus cervi L1 in red deer (Cervus elaphus) populations

Faecal surveys are commonly used as non-invasive means to evaluate population abundance of animals as well as comparable indexes of prevalence and intensity of diseases between populations, especially macroparasites. While faecal surveys are among one of the simplest means to perform these evaluations, they are time consuming and labour intensive. The present study evaluated 80 red deer (Cervus elaphus) faecal samples collected in two study sites for the presence and abundance of first-stage larvae of the nematode Elaphostrongylus cervi and established pools of samples for epidemiological analysis. The analysis of 20–30 individual samples would produce a reliable estimate of the ‘true’ prevalence, and the error of the smaller sample size only doubled that of the 80 reference samples. The analysis of 5 pools of 5 pellet groups each, or of 4 pools of 10 pellet groups each, provided a reliable estimation of the ‘true’ excretion abundance estimated by the analysis of all 80 samples. These pools comprise a cost-effective and dependable alternative for measuring and obtaining comparable abundances of parasitic faecal excretion stages in red deer populations, which is very valuable for epidemiological and ecological research as well as for management purposes.

The importance of parasite life history and host density in predicting the impact of infections in red deer

We studied a macroparasite (Elaphostrongylus cervi, Nematoda) and a microparasite infection (tuberculosis, TB) in red deer (Cervus elaphus) across different populations where managers manipulated host condition, density and aggregation by providing supplemental food. We aimed to test whether and, if so, how persistence and transmission of both parasites differentially varied as host body condition and population density varied. We took account of sex, as red deer life history greatly concerns sex-related traits. Changes in host factors had different consequences for the spread of each parasite type. Individual presence of tuberculosis was positively associated with host density, whereas E. cervi abundance negatively related to host density and enhanced body condition. There was lack of body condition density dependence; and body condition was mainly dependent on the amount of supplemental food provided, but also on habitat quality descriptors. Overall, our results suggest that body condition was improved at the cost of increased host contact rates, which implied an ecological trade-off between acquiring resources to cope with E. cervi, a macroparasite, and concurrent exposure to mycobacteria. By the simultaneous study of both infections, this research suggests that the effects of changes in host number and population structure on disease spread and persistence need to take into account variation in life histories of the parasites. These findings also raise concern about the ecological consequences of diseases and management of wildlife on host life history.

Sex, age, spleen size, and kidney fat of red deer relative to infection intensities of the lungworm Elaphostrongylus cervi

We analyzed the relationships among spleen size, body condition (measured as kidney fat), and larval counts of the nematode Elaphostrongylus cervi in red deer (Cervus elaphus). The aim was to investigate the interaction between host body condition and intensity of infection with parasites. As red deer are highly polygynous, we also tested whether these relationships varied with sex and age of the hosts. Kidney fat and spleen size were positively correlated in subadults (2-3 years old) and adults (>3 years old), but not in calves (<1 year old) or yearlings (1-2 years old). Spleen size was negatively associated with nematode load in subadult females and in adult males. These two age classes are potentially the most nutritionally stressed, as subadult hinds are still growing and often engaging in rearing their first calf, and adult stags were sampled just after the rut, which is recognized as a substantial energy drain in this age-sex class, as they compete to hold females during the mating season. Body condition related negatively to parasite count only in adult males. In the context of red deer life history, these findings suggest that spleen size is dependent on body condition and that it could be affected by variation in resource partitioning among immune defense, growth, and reproductive effort in red deer. For the first time in a wild mammal, the spleen mass is shown to be positively related to body condition and negatively related to parasite infection. We conclude that elucidating whether spleen mass reflects immune defense investment or a measure of general body condition should contribute to understanding topical issues in mammal ecology.

Epidemiology and risk factors analysis of elaphostrongylosis in red deer (Cervus elaphus) from Spain

We studied the distribution and faecal shedding pattern of the first-stage larvae (L1) of Elaphostrongylus cervi (Nematoda: Protostrongylidae) in the red deer (Cervus elaphus) across Spain, where excretion was widespread. We evaluated the effects of individual, population and environmental factors on E. cervi L1 counts in 18 free-ranging red deer populations in South Central Spain. In this area, prevalence was 71.42+/-2.14% (n = 448) and mean intensity (n = 320) was 74.50+/-10.35. Aggregation of deer at water-holes was positively associated with E. cervi L1 prevalence, possibly due to spatial and temporal odds of infected gastropods, red deer and infective E. cervi L1 larvae being encountered. Prevalence increased with age, and there was also a trend towards males having higher intensities than females. A slightly decreasing age-intensity profile was identified for females, which may suggest a role of acquired immunity.

Relationship between bronchopulmonary nematode larvae and relative abundances of Spanish ibex (Capra pyrenaica hispanica) from Castilla-La Mancha, Spain

The excretion of bronchopulmonary nematode infective larvae was evaluated in 160 faecal samples of Spanish ibex (Capra pyrenaica hispanica) collected from 13 populations in Castilla-La Mancha, south-central Spain in September 2003. Intensities and prevalences were compared with pasture availability, abundances of wild and domestic ungulates at both levels, i.e. for populations and for faeces in a two-step procedure. Protostrongylid larvae showed similar infection rates (mean intensity: 1.56+/-0.12, n=94; mean prevalence: 25.62+/-6.86%, n=160) to Dictyocaulus spp. (mean intensity: 1.03+/-0.11, n=48; mean prevalence: 30.00+/-7.11%, n=160). At the population level, positive correlations were found between the prevalences of both bronchopulmonary taxa. The prevalence in both groups, but not intensity, also correlated positively with Spanish ibex abundance indexes both for the populations and individual faeces. These findings suggest that: (i) parasite spreading across Spanish ibex populations in Castilla-La Mancha could respond to host density-dependent processes; and (ii) these populations may have similar exposition and/or susceptibility to both bronchopulmonary taxa resulting in similar host-parasite patterns, despite their different life cycles. Bronchopulmonary outputs in the Spanish ibex from Castilla-La Mancha seems not to represent a health risk for this endemic wild ungulate but may be useful in any health surveillance scheme for the increasing populations of Spanish ibex.

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.

Epidemiology of cerebrospinal Elaphostrongylus cervi infection in red deer in central Spain

Elaphostrongylus cervi produces a subclinical cerebrospinal disease in many wild and domestic ruminants from Europe, North America and New Zealand and has recently been described in Spain. To determine some aspects of its epidemiology, 121 red deer (Cervus elaphus) from central Spain were sampled during 2000. The prevalence (7%) and mean worm burden (3.8 worms per brain) were similar to the values previously recorded in other European areas. The infection was only detected in young deer during the winter. The estimation of larval production in the faeces was not a reliable method of diagnosing E. cervi infection.