Emergence of Canine Distemper Virus Strains With Modified Molecular Signature and Enhanced Neuronal Tropism Leading to High Mortality in Wild Carnivores

An ongoing canine distemper epidemic was first detected in Switzerland in the spring of 2009. Compared to previous local canine distemper outbreaks, it was characterized by unusually high morbidity and mortality, rapid spread over the country, and susceptibility of several wild carnivore species. Here, the authors describe the associated pathologic changes and phylogenetic and biological features of a multiple highly virulent canine distemper virus (CDV) strain detected in and/or isolated from red foxes (Vulpes vulpes), Eurasian badgers (Meles meles), stone (Martes foina) and pine (Martes martes) martens, from a Eurasian lynx (Lynx lynx), and a domestic dog. The main lesions included interstitial to bronchointerstitial pneumonia and meningopolioencephalitis, whereas demyelination-the classic presentation of CDV infection-was observed in few cases only. In the brain lesions, viral inclusions were mainly in the nuclei of the neurons. Some significant differences in brain and lung lesions were observed between foxes and mustelids. Swiss CDV isolates shared together with a Hungarian CDV strain detected in 2004. In vitro analysis of the hemagglutinin protein from one of the Swiss CDV strains revealed functional and structural differences from that of the reference strain A75/17, with the Swiss strain showing increased surface expression and binding efficiency to the signaling lymphocyte activation molecule (SLAM). These features might be part of a novel molecular signature, which might have contributed to an increase in virus pathogenicity, partially explaining the high morbidity and mortality, the rapid spread, and the large host spectrum observed in this outbreak.

The loss of indirect interactions leads to cascading extinctions of carnivores

Species extinctions are biased towards higher trophic levels, and primary extinctions are often followed by unexpected secondary extinctions. Currently, predictions on the vulnerability of ecological communities to extinction cascades are based on models that focus on bottom-up effects, which cannot capture the effects of extinctions at higher trophic levels. We show, in experimental insect communities, that harvesting of single carnivorous parasitoid species led to a significant increase in extinction rate of other parasitoid species, separated by four trophic links. Harvesting resulted in the release of prey from top-down control, leading to increased interspecific competition at the herbivore trophic level. This resulted in increased extinction rates of non-harvested parasitoid species when their host had become rare relative to other herbivores. The results demonstrate a mechanism for horizontal extinction cascades, and illustrate that altering the relationship between a predator and its prey can cause wide-ranging ripple effects through ecosystems, including unexpected extinctions.

Recovery of large carnivores in Europe's modern human-dominated landscapes.

The conservation of large carnivores is a formidable challenge for biodiversity conservation. Using a data set on the past and current status of brown bears (Ursus arctos), Eurasian lynx (Lynx lynx), gray wolves (Canis lupus), and wolverines (Gulo gulo) in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible. The European situation reveals that large carnivores and people can share the same landscape.

Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment

Biodiversity is rapidly declining, and this may negatively affect ecosystem processes, including economically important ecosystem services. Previous studies have shown that biodiversity has positive effects on organisms and processes across trophic levels. However, only a few studies have so far incorporated an explicit food-web perspective. In an eight-year biodiversity experiment, we studied an unprecedented range of above- and below-ground organisms and multitrophic interactions. A multitrophic data set originating from a single long-term experiment allows mechanistic insights that would not be gained from meta-analysis of different experiments. Here we show that plant diversity effects dampen with increasing trophic level and degree of omnivory. This was true both for abundance and species richness of organisms. Furthermore, we present comprehensive above-ground/below-ground biodiversity food webs. Both above ground and below ground, herbivores responded more strongly to changes in plant diversity than did carnivores or omnivores. Density and richness of carnivorous taxa was independent of vegetation structure. Below-ground responses to plant diversity were consistently weaker than above-ground responses. Responses to increasing plant diversity were generally positive, but were negative for biological invasion, pathogen infestation and hyperparasitism. Our results suggest that plant diversity has strong bottom-up effects on multitrophic interaction networks, with particularly strong effects on lower trophic levels. Effects on higher trophic levels are indirectly mediated through bottom-up trophic cascades.

[Occurrence of Trichinella spp. in wild boar in Switzerland]

Trichinellosis is a worldwide occurring zoonosis caused by the intracellular nematode Trichinella spp. One of the main infection sources in Europe is raw or undercooked meat from wild boar. Trichinella britovi is prevalent in wild carnivores in Switzerland, thus a possible inclusion of wild boar in this wildlife cycle cannot be excluded. In order to assess the prevalence of Trichinella infection in wild boar, we tested 1,458 animals with both parasitological and serological methods. In none of the animals Trichinella-larvae could be recovered by the artificial digestion method (prevalence of larvae: 0 %; 95 % CI 0.0 - 0.3). Antibodies in meat juice were detected in 57 animals using a standardized E/S-Ag-ELISA. However, in the confirmatory westernblot, only 3 animals remained seropositive (seroprevalence: 0.2 %; 95 % CI 0.07 %-0.60 %). The occurrence of wild boar positive for anti-Trichinella-antibodies indicates that meat inspection for Trichinella-larvae in this species is important to prevent human infections.

The EG95 antigen of Echinococcus spp. contains positively selected amino acids, which may influence host specificity and vaccine efficacy

Echinococcosis is a worldwide zoonotic parasitic disease of humans and various herbivorous domestic animals (intermediate hosts) transmitted by the contact with wild and domestic carnivores (definitive hosts), mainly foxes and dogs. Recently, a vaccine was developed showing high levels of protection against one parasite haplotype (G1) of Echinococcus granulosus, and its potential efficacy against distinct parasite variants or species is still unclear. Interestingly, the EG95 vaccine antigen is a secreted glycosylphosphatydilinositol (GPI)-anchored protein containing a fibronectin type III domain, which is ubiquitous in modular proteins involved in cell adhesion. EG95 is highly expressed in oncospheres, the parasite life cycle stage which actively invades the intermediate hosts. After amplifying and sequencing the complete CDS of 57 Echinococcus isolates belonging to 7 distinct species, we uncovered a large amount of genetic variability, which may influence protein folding. Two positively selected sites are outside the vaccine epitopes, but are predicted to alter protein conformation. Moreover, phylogenetic analyses indicate that EG95 isoform evolution is convergent with regard to the number of beta-sheets and alpha-helices. We conclude that having a variety of EG95 isoforms is adaptive for Echinococcus parasites, in terms of their ability to invade different hosts, and we propose that a mixture of isoforms could possibly maximize vaccine efficacy.

Fatal combined infection with canine distemper virus and orthopoxvirus in a group of Asian marmots (Marmota caudata)

A fatal combined infection with canine distemper virus (CDV) and orthopoxvirus (OPXV) in Asian marmots (Marmota caudata) is reported in this article. A total of 7 Asian marmots from a small zoological garden in Switzerland were found dead in hibernation during a routine check in the winter of 2011. The marmots died in February 2011. No clinical signs of disease were observed at any time. The viruses were detected in all individuals for which the tissues were available (n = 3). Detection of the viruses was performed by reverse transcription polymerase chain reaction. The most consistent gross lesion was a neck and thorax edema. A necrotizing pharyngitis and a multifocal necrotizing pneumonia were observed histologically. Numerous large intracytoplasmic eosinophilic inclusions were seen in the epithelial cells of the pharynx, of the airways, and in the skin keratinocytes. Brain lesions were limited to mild multifocal gliosis. Phylogenetic analysis revealed that the marmot CDV strain was closely related to the clusters of CDVs detected in Switzerland in wild carnivores during a local outbreak in 2002 and the 2009-2010 nationwide epidemic, suggesting a spillover of this virus from wildlife. The OPXV was most closely related to a strain of cowpoxvirus, a poxvirus species considered endemic in Europe. This is the first reported instance of CDV infection in a rodent species and of a combined CDV and OPXV infection.

Herbivore identity mediates the strength of trophic cascades on individual plants

The strength of top-down indirect effects of carnivores on plants (trophic cascades) varies greatly and may depend on the identity of the intermediate (herbivore) species. If the effect strength is linked to functional traits of the herbivores then this would allow for more general predictions. Due to the generally sub-lethal effects of herbivory in terrestrial systems, trophic cascades manifest themselves in the first instance in the fitness of individual plants, affecting both their numerical and genetic contributions to the population. We directly compare the indirect predator effects on growth and reproductive output of individual Vicia faba plants mediated by the presence of two aphid species: Acyrtosiphon pisum is characterised by a boom and bust strategy whereby colonies grow fast and overexploit their host plant individual while Megoura viciae appear to follow a more prudent strategy that avoids over-exploitation and death of the host plant.Plants in the field were infested with A. pisum, M. viciae or both and half the plants were protected from predators. Exposure to predators had a strong impact on the biomass of individual plants and the strength of this effect differed significantly between the different herbivore treatments.A. pisum had a greater direct impact on plants and this was coupled with a significantly stronger indirect predator effect on plant biomass.Although the direct impact of predators was strongest on M. viciae, this was not transmitted to the plant level, indicating that the predator-prey interactions strength is not as important as the plant-herbivore link for the magnitude of the indirect predator impact. At the individual plant level, the indirect predator effect was purely due to consumptive effects on herbivore densities with no evidence for increased herbivore dispersal in response to presence of predators. The nature of plant-herbivore interactions is the key to terrestrial trophic cascade strength. The two herbivores that we compared were similar in feeding mode and body size but differed their way how they exploit host plants, which was the important trait explaining the strength of the trophic cascade.

Herbivory in Spiders: The Importance of Pollen for Orb-Weavers

Orb-weaving spiders (Araneidae) are commonly regarded as generalist insect predators but resources provided by plants such as pollen may be an important dietary supplementation. Their webs snare insect prey, but can also trap aerial plankton like pollen and fungal spores. When recycling their orb webs, the spiders may therefore also feed on adhering pollen grains or fungal spores via extraoral digestion. In this study we measured stable isotope ratios in the bodies of two araneid species (Aculepeira ceropegia and Araneus diadematus), their potential prey and pollen to determine the relative contribution of pollen to their diet. We found that about 25% of juvenile orb-weaving spiders’ diet consisted of pollen, the other 75% of flying insects, mainly small dipterans and hymenopterans. The pollen grains in our study were too large to be taken up accidentally by the spiders and had first to be digested extraorally by enzymes in an active act of consumption. Therefore, pollen can be seen as a substantial component of the spiders’ diet. This finding suggests that these spiders need to be classified as omnivores rather than pure carnivores.

Vultures vs livestock: conservation relationships in an emerging conflict between humans and wildlife

Human–wildlife conflict is emerging as an important topic in conservation. Carnivores and birds of prey are responsible for most conflicts with livestock and game but since the mid 1990s a new conflict is emerging in south-west Europe: the presumed killing of livestock by griffon vultures Gyps fulvus. Lack of scientific data and magnification of the problem by the media are increasing alarm amongst the public, and political pressures to implement management decisions have not been based on scientific evidence. We compiled information on 1,793 complaints about attacks by griffon vultures on livestock, lodged with Spanish authorities from 1996 to 2010. Spain is home to the majority (95%) of griffon vultures and other scavengers in the European Union. Most of the cases occurred in areas of high livestock density, affected principally sheep (49%) and cows (31%), and were associated with spring birthing times (April–June). On average 69% of the complaints made annually were rejected because of a lack of evidence about whether the animal was alive before being eaten. The total economic cost of compensation was EUR 278,590 from 2004 to 2010. We discuss possible ways to mitigate this emerging human–wildlife conflict. These need to include the participation of livestock farmers, authorities, scientists and conservation groups.

First detection of sarcoptic mange in free-ranging wild boar (Sus scrofa) in Switzerland.

In Switzerland sarcoptic mange is frequent in free-ranging wild carnivores but until recent years no cases had been recorded in wild ungulates. Since 2010, cases have been observed in wild boar in the cantons of Solothurn, Tessin and Thurgau. Here, we report the detection of mange-like skin lesions in wild boars by photo-trapping and the post-mortem findings in 6 culled animals presenting different stages of the disease. Potential sources of infection include mangy red foxes, outdoor domestic pigs and wild boars from surrounding countries. Disease spread in the wild boar population may become relevant not only for wildlife but also for domestic pig health in the future if piggeries' biosecurity is insufficient to prevent interactions with wild boar.