Prevalence of tick-borne pathogens in ixodid ticks (Acari: Ixodidae) collected from European wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>) and Iberian red deer (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>) in central Spain

Emerging tick-borne diseases of humans and animals have occurred frequently during the past 30 years. These disease outbreaks appear to result from changes in the distribution of tick and vertebrate hosts, and the introduction of humans and domestic animals into tick–pathogen–wildlife cycles. Use of molecular technologies now available for identification of pathogens in ticks can provide valuable information that allows for risk analysis of emerging tick-borne diseases. In this study, the prevalence of selected pathogens in ticks collected in six locations in central Spain from the major wild ungulate species, European wild boar (Sus scrofa) and Iberian red deer (Cervus elaphus hispanicus), was determined by PCR. Tick species collected included Ixodes ricinus, Dermacentor marginatus, Rhipicephalus bursa and Hyalomma m. marginatum. Pathogens identified in ticks included piroplasmids, Anaplasma spp., Ehrlichia spp. and Rickettsia spp. Piroplasmids were identified in all tick species except I. ricinus. Ehrlichia spp. were detected in all tick species and collection locations, while Rickettsia spp., which proved to be R. slovaca and a recently identified Rickettsia sp. DnS28, were identified only in D. marginatus. A. marginale and A. phagocytophilum were detected in D. marginatus, R. bursa and Hy. m. marginatum. Concurrent infections of these pathogens were frequently observed in ticks. Notably, A. phagocytophilum, which is infective for a broad host range that includes humans and domestic and wild animals, was identified in ticks from all collection locations. The variety of ticks and tick-borne pathogens demonstrated in this study suggests a risk in central Spain for the emergence of tick-borne diseases in humans and domestic animals.     

Reservoirs of <Emphasis Type="Italic">Brucella</Emphasis> infection in nature

Brucellosis is a zoonosis caused by bacteria of the genus Brucella, which includes nine species: B. melitensis (goats and sheep as the main reservoir hosts), B. abortus (cattle), B. suis (pigs), B. neotomae (desert woodrats), B. ovis (sheep), B. canis (dogs), B. ceti (whales), B. pinnipedialis (pinnipeds), and B. microti (Microtus voles). The epidemic and epizootic situation with brucellosis is accounted for by farm animals, which are the carriers of three main pathogens (B. melitensis, B. abortus, and B. suis). Their ubiquitous distribution is the factor determining global prevalence of the above Brucella species on all continents and in the overwhelming majority of countries. Consistent with the expansion of the pathogen ecological range are the 1990s findings of new Brucella species in marine mammals (whales and pinnipeds) and in some rodents. These bacteria proved to be also pathogenic for terrestrial mammals and humans. All Brucella-infected animals considered in the paper are tentatively divided into two groups. The first includes most of the wild and domestic animal species, birds, and ticks that acquire the infection farm animals, the main hosts of Brucella. The second group includes animals (wild reindeer, hares, bison, and probably saiga antelopes, dogs, and marine mammals) which may carry Brucella regardless of infection prevalence in the main hosts.     

The origin of human pathogens: evaluating the role of agriculture and domestic animals in the evolution of human disease

Many significant diseases of human civilization are thought to have arisen concurrently with the advent of agriculture in human society. It has been hypothesised that the food produced by farming increased population sizes to allow the maintenance of virulent pathogens, i.e. civilization pathogens, while domestic animals provided sources of disease to humans. To determine the relationship between pathogens in humans and domestic animals, I examined phylogenetic data for several human pathogens that are commonly evolutionarily linked to domestic animals: measles, pertussis, smallpox, tuberculosis, taenid worms, and falciparal malaria. The majority are civilization pathogens, although I have included others whose evolutionary origins have traditionally been ascribed to domestic animals. The strongest evidence for a domestic-animal origin exists for measles and pertussis, although the data do not exclude a non-domestic origin. As for the other pathogens, the evidence currently available makes it difficult to determine if the domestic-origin hypothesis is supported or refuted; in fact, intriguing data for tuberculosis and taenid worms suggests that transmission may occur as easily from humans to domestic animals. These findings do not abrogate the importance of agriculture in disease transmission; rather, if anything, they suggest an alternative, more complex series of effects than previously elucidated. Rather than domestication, the broader force for human pathogen evolution could be ecological change, namely anthropogenic modification of the environment. This is supported by evidence that many current emerging infectious diseases are associated with human modification of the environment. Agriculture may have changed the transmission ecology of pre-existing human pathogens, increased the success of pre-existing pathogen vectors, resulted in novel interactions between humans and wildlife, and, through the domestication of animals, provided a stable conduit for human infection by wildlife diseases.     

The immunotoxicity of environmental contaminants to marine wildlife: A review

Virus-associated mass mortalities among several marine mammal populations inhabiting industrialized coastal areas have generated an interest in wildlife immunotoxicology. Despite the isolation of previously uncharacterized viruses from victims, a contribution of immunotoxic contaminants to the severity of the outbreaks could not be ruled out. Fish-eating marine mammals, including seals, occupy high trophic levels in the aquatic food chain, and accumulate high levels of contaminants including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychorinated dibenzofurans (PCDFs). Such chemicals have been found to be immunotoxic at low doses in studies of laboratory animals. While associations have been established between environmental contaminants and various adverse biological effects in certain free-ranging seal populations, evidence for immunotoxicity has, until recently, been lacking. To this end, we carried out an immunotoxicological study, in which captive harbor seals were fed herring from either relatively uncontaminated sites of the Atlantic Ocean, or from the highly contaminated Baltic Sea. In this review, we summarize the contaminant-related immunosuppression observed in the captive group of seals fed herring from the Baltic Sea, and discuss these results in the context of what is currently known about outbreaks of virus infection, comparative immunology, and environmental contaminants. We also describe two parallel studies, in which laboratory rats exposed as adults or perinatally to the contaminants in the Baltic Sea herring, exhibited immunotoxicity. On the basis of these and other studies, we conclude that complex mixtures of environmental contaminants may represent a real immunotoxic risk to free-ranging marine mammals in many areas of Europe and North America.     

Diseases of humans and their domestic mammals: pathogen characteristics, host range and the risk of emergence

Pathogens that can be transmitted between different host species are of fundamental interest and importance from public health, conservation and economic perspectives, yet systematic quantification of these pathogens is lacking. Here, pathogen characteristics, host range and risk factors determining disease emergence were analysed by constructing a database of disease-causing pathogens of humans and domestic mammals. The database consisted of 1415 pathogens causing disease in humans, 616 in livestock and 374 in domestic carnivores. Multihost pathogens were very prevalent among human pathogens (61.6%) and even more so among domestic mammal pathogens (livestock 77.3%, carnivores 90.0%). Pathogens able to infect human, domestic and wildlife hosts contained a similar proportion of disease-causing pathogens for all three host groups. One hundred and ninety-six pathogens were associated with emerging diseases, 175 in humans, 29 in livestock and 12 in domestic carnivores. Across all these groups, helminths and fungi were relatively unlikely to emerge whereas viruses, particularly RNA viruses, were highly likely to emerge. The ability of a pathogen to infect multiple hosts, particularly hosts in other taxonomic orders or wildlife, were also risk factors for emergence in human and livestock pathogens. There is clearly a need to understand the dynamics of infectious diseases in complex multihost communities in order to mitigate disease threats to public health, livestock economies and wildlife.     

Metacommunity and phylogenetic structure determine wildlife and zoonotic infectious disease patterns in time and space

The potential for disease transmission at the interface of wildlife, domestic animals and humans has become a major concern for public health and conservation biology. Research in this subject is commonly conducted at local scales while the regional context is neglected. We argue that prevalence of infection at local and regional levels is influenced by three mechanisms occurring at the landscape level in a metacommunity context. First, (1) dispersal, colonization, and extinction of pathogens, reservoir or vector hosts, and nonreservoir hosts, may be due to stochastic and niche‐based processes, thus determining distribution of all species, and then their potential interactions, across local communities (metacommunity structure). Second, (2) anthropogenic processes may drive environmental filtering of hosts, nonhosts, and pathogens. Finally, (3) phylogenetic diversity relative to reservoir or vector host(s), within and between local communities may facilitate pathogen persistence and circulation. Using a metacommunity approach, public heath scientists may better evaluate the factors that predispose certain times and places for the origin and emergence of infectious diseases. The multidisciplinary approach we describe fits within a comprehensive One Health and Ecohealth framework addressing zoonotic infectious disease outbreaks and their relationship to their hosts, other animals, humans, and the environment.     

Marked host specificity and lack of phylogeographic population structure of Campylobacter jejuni in wild birds

Zoonotic pathogens often infect several animal species, and gene flow among populations infecting different host species may affect the biological traits of the pathogen including host specificity, transmissibility and virulence. The bacterium Campylobacter jejuni is a widespread zoonotic multihost pathogen, which frequently causes gastroenteritis in humans. Poultry products are important transmission vehicles to humans, but the bacterium is common in other domestic and wild animals, particularly birds, which are a potential infection source. Population genetic studies of C. jejuni have mainly investigated isolates from humans and domestic animals, so to assess C. jejuni population structure more broadly and investigate host adaptation, 928 wild bird isolates from Europe and Australia were genotyped by multilocus sequencing and compared to the genotypes recovered from 1366 domestic animal and human isolates. Campylobacter jejuni populations from different wild bird species were distinct from each other and from those from domestic animals and humans, and the host species of wild bird was the major determinant of C. jejuni genotype, while geographic origin was of little importance. By comparison, C. jejuni differentiation was restricted between more phylogenetically diverse farm animals, indicating that domesticated animals may represent a novel niche for C. jejuni and thereby driving the evolution of those bacteria as they exploit this niche. Human disease is dominated by isolates from this novel domesticated animal niche.     

Transmission or Within-Host Dynamics Driving Pulses of Zoonotic Viruses in Reservoir–Host Populations

Progress in combatting zoonoses that emerge from wildlife is often constrained by limited knowledge of the biology of pathogens within reservoir hosts. We focus on the host–pathogen dynamics of four emerging viruses associated with bats: Hendra, Nipah, Ebola, and Marburg viruses. Spillover of bat infections to humans and domestic animals often coincides with pulses of viral excretion within bat populations, but the mechanisms driving such pulses are unclear. Three hypotheses dominate current research on these emerging bat infections. First, pulses of viral excretion could reflect seasonal epidemic cycles driven by natural variations in population densities and contact rates among hosts. If lifelong immunity follows recovery, viruses may disappear locally but persist globally through migration; in either case, new outbreaks occur once births replenish the susceptible pool. Second, epidemic cycles could be the result of waning immunity within bats, allowing local circulation of viruses through oscillating herd immunity. Third, pulses could be generated by episodic shedding from persistently infected bats through a combination of physiological and ecological factors. The three scenarios can yield similar patterns in epidemiological surveys, but strategies to predict or manage spillover risk resulting from each scenario will be different. We outline an agenda for research on viruses emerging from bats that would allow for differentiation among the scenarios and inform development of evidence-based interventions to limit threats to human and animal health. These concepts and methods are applicable to a wide range of pathogens that affect humans, domestic animals, and wildlife.     

Emerging infectious disease: what are the relative roles of ecology and evolution?

The increasing threat of infectious diseases in humans has renewed interest in factors leading to the emergence of new diseases and the re-emergence of familiar diseases. Examples of seemingly novel diseases currently spreading in human populations include HIV, dengue hemorrhagic fever and Lyme disease; drug-resistant forms of well-known diseases such as tuberculosis are also increasing. The problem of disease emergence also extends to other animal and plant populations. In most current epidemics, ecological factors (e.g. migration, climate, agricultural practices) play a more significant role in disease emergence than evolutionary changes in pathogens or hosts. Evolutionary biologists and ecologists have much to offer to the development of strategies for the control of emerging diseases.     

Resistance to essential oils affects survival of Salmonella enterica serovars in growing and harvested basil

The number of outbreaks of food‐borne illness associated with consumption of fresh products has increased. A recent and noteworthy outbreak occurred in 2007. Basil contaminated with Salmonella enterica serovar Senftenberg was the source of this outbreak. Since basil produces high levels of antibacterial compounds the aim of this study was to investigate if the emerging outbreak reflects ecological changes that occurred as a result of development of resistance to ingredients of the basil oil. We irrigated basil plants with contaminated water containing two Salmonella serovars, Typhimurium and Senftenberg, and showed that Salmonella can survive on the basil plants for at least 100 days. S. Senftenberg counts in the phyllosphere were significantly higher than S. Typhimurium, moreover, S. Senftenberg was able to grow on stored harvested basil leaves. Susceptibility experiments demonstrated that S. Senftenberg is more resistant to basil oil and to its antimicrobial constituents: linalool, estragole and eugenol. This may indicate that S. Senftenberg had adapted to the basil environment by developing resistance to the basil oil. The emergence of resistant pathogens has a significant potential to change the ecology, and opens the way for pathogens to survive in new niches in the environment such as basil and other plants.     

Does human proximity affect antibody prevalence in marine-foraging river otters (Lontra canadensis)?

The investigation of diseases of free-ranging river otters (Lontra canadensis) is a primary conservation priority for this species; however, very little is known about diseases of river otters that forage in marine environments. To identify and better understand pathogens that could be important to marine-foraging river otters, other wildlife species, domestic animals, and humans and to determine if proximity to human population could be a factor in disease exposure, serum samples from 55 free-ranging marine-foraging river otters were tested for antibodies to selected pathogens. Thirty-five animals were captured in Prince William Sound, Alaska (USA), an area of low human density, and 20 were captured in the San Juan Islands, Washington State (USA), an area characterized by higher human density. Of 40 river otters tested by indirect immunofluorescent antibody test, 17.5% were seropositive (titer > or =320) for Toxoplasma gondii. All positive animals came from Washington. Of 35 river otters tested for antibodies to Leptospira interrogans using the microscopic agglutination test, 10 of 20 (50%) from Washington were seropositive (titer > or =200). None of the 15 tested animals from Alaska were positive. Antibodies to Neospora caninum (n=40), Sarcocystis neurona (n=40), Brucella abortus (n=55), avian influenza (n=40), canine distemper virus (n=55), phocine distemper virus (n=55), dolphin morbillivirus (n=55), porpoise morbillivirus (n=55), and Aleutian disease parvovirus (n=46) were not detected. Identifying exposure to T. gondii and L. interrogans in otters from Washington State but not in otters from Alaska suggests that living proximal to higher human density and its associated agricultural activities, domestic animals, and rodent populations could enhance river otter exposure to these pathogens.     

Epidemiology,Evolution, and Recent Outbreaks of Avian Influenza Virus in China

Novel reassortants of H7N9, H10N8, and H5N6 avian influenza viruses (AIVs) are currently circulating in China''s poultry flocks, occasionally infecting humans and other mammals. Combined with the sometimes enzootic H5N1 and H9N2 strains, this cauldron of genetically diverse AIVs pose significant risks to public health. Here, we review the epidemiology, evolution, and recent outbreaks of AIVs in China, discuss reasons behind the recent increase in the emergence of novel AIVs, and identify warning signs which may point to the emergence of a potentially virulent and highly transmissible AIV to humans. This review will be useful to authorities who consider options for the detection and control of AIV transmission in animals and humans, with the goal of preventing future epidemics and pandemics.     

Infectious disease and amphibian population declines

Abstract. A series of recent papers have implicated pathogens and parasites in amphibian population declines. Here, we review evidence on the link between infectious disease and amphibian population declines. We conclude that available data provide the clearest link for the fungal disease amphibian chytridiomycosis, although other pathogens are also implicated. We suggest additional experimental and observational data that need to be collected to provide further support that these other pathogens are associated with declines. We suggest that, in common with many emerging infectious diseases (EIDs) of humans, domestic animals and other wildlife species, emergence of chytridiomycosis may be driven by anthropogenic introduction (pathogen pollution). Finally, we review a number of recent advances in the host–parasite ecology of chytridiomycosis that help explain its emergence and impact.     

Circulating glutathione concentrations in marine,semiaquatic, and terrestrial mammals

An important low molecular weight antioxidant in biological systems is glutathione; its efficiency depends on the equilibrium between its reduced (GSH) and oxidized (GSSG) forms. The oxidized:total glutathione (GSSG:GSH‐Eq) ratio can be used as an indicator of oxidative stress. Previous studies suggest that marine mammals, unlike terrestrial mammals, do not show adverse effects in tissues exposed to ischemia/reperfusion during the peripheral vasoconstriction associated with breath‐hold diving. This is due, in part, to higher antioxidant enzyme activities in marine mammals compared with terrestrial mammals. The objective of this study was to compare circulating glutathione levels among mammals with different diving capacities. Circulating GSH‐Eq, GSH, and GSSG concentrations in erythrocyte samples from northern elephant seals (Mirounga angustirostris), bottlenose dolphins (Tursiops truncatus), neotropical otters (Lontra longicaudis annectens), domestic pigs (Sus scrofa), and humans were quantified using spectrophotometry. Higher GSH‐Eq and GSH concentrations and a lower GSSG:GSH‐Eq index were found in erythrocytes from northern elephant seals and bottlenose dolphins as compared to otters, domestic pigs, and humans. Results suggest that marine mammals, independent of their diving capacity, possess a highly developed antioxidant system, including GSH; continuous availability of GSH could allow these species to avoid oxidative damage and tolerate ischemia/reperfusion and hypoxia/reoxygenation events associated with diving.     

Qualitative risk assessment of the role of the feral wild boar (Sus scrofa) in the likelihood of incursion and the impacts on effective disease control of selected exotic diseases in England

A qualitative risk assessment was undertaken to analyse the likelihood of the incursion of selected exotic infectious disease into England’s small populations of feral boar and the potential impacts these animals could have on effective disease control. In order to identify the exposure pathways, it was necessary to consider not only the epidemiology of the pathogens but also to understand how the ecology and behaviour of wild boar would affect disease transmission. It was concluded that the greatest risks of exotic disease incursion into the UK were associated with disease entering through the consumption of infected pork meat or meat products by either wild boar or domestic swine and thus the diseases of highest risk are classic swine fever, foot and mouth disease and Trichinella sp. It should be noted that much of the peer review publications used as the scientific evidence base for this assessment describes disease outbreaks in boar populations in countries which have the disease endemically or have been previously exposed to the disease. In the UK, disease may act differently as the UK population of boar will be naïve to the exotic notifiable diseases.

     

Pathogenic fungi of marine animals: A taxonomic perspective

Fungi cause diseases in a variety of marine animal hosts. After a thorough review of published literature, we identified 225 fungal species causing infections of 193 animal species, for a total of 357 combinations of pathogenic fungi and marine animal hosts. Among the 193 animal host species, Chordata (100 species, 51.8 %) and Arthropoda (68 species, 35.2 %) were discovered to be the most frequently reported hosts of fungal pathogens. Microsporidia (111 species, 49.3 %) constitutes over half of the described pathogenic fungal species of marine animals, followed by Ascomycota (85 species, 37.8 %), Mucoromycota (22 species, 9.8 %), Basidiomycota (6 species, 2.7 %) and Chytridiomycota (1 species, 0.4 %). Microsporidia primarily parasitize marine arthropods and Teleostei fish, while Basidiomycota are primarily known to cause respiratory diseases of marine mammals. Ascomycota has a diverse host range, from mammals, fish, crustaceans, soft corals and sea turtle. Few Mucoromycota and Chytridiomycota were reported to infect marine animals. Fungal diseases documented in this review likely represent a fraction of fungal diseases in the ocean, where it was estimated to be inhabited by 2.15 million animal species. Intensification of aquaculture practices, global warming and marine pollution may increase fungal disease outbreak of marine animals. All the topics mentioned above will be discussed in greater details in this review.     

Spatial variation and low diversity in the major histocompatibility complex in walrus (Odobenus rosmarus)

Increased global temperature and associated changes to Arctic habitats will likely result in the northward advance of species, including an influx of pathogens novel to the Arctic. How species respond to these immunological challenges will depend in part on the adaptive potential of their immune response system. We compared levels of genetic diversity at a gene associated with adaptive immune response [Class II major histocompatibility complex (MHC), DQB exon 2] between populations of walrus (Odobenus rosmarus), a sea ice-dependent Arctic species. Walrus was represented by only five MHC DQB alleles, with frequency differences observed between Pacific and Atlantic populations. MHC DQB alleles appear to be under balancing selection, and most (80 %; n = 4/5) of the alleles were observed in walruses from both oceans, suggesting broad scale differences in the frequency of exposure and diversity of pathogens may be influencing levels of heterozygosity at DQB in walruses. Limited genetic diversity at MHC, however, suggests that walrus may have a reduced capacity to respond to novel immunological challenges associated with shifts in ecological communities and environmental stressors predicted for changing climates. This is particularly pertinent for walrus, since reductions in summer sea ice may facilitate both northward expansion of marine species and associated pathogens from more temperate regions, and exchange of marine mammals and associated pathogens through the recently opened Northwest Passage between the Atlantic and Pacific Oceans in the Canadian high Arctic.     

Risks of endemicity, morbidity and perspectives regarding the control of Chagas disease in the Amazon Region

Chagas disease, in the Amazon Region as elsewhere, can be considered an enzootic disease of wild animals or an anthropozoonosis, an accidental disease of humans that is acquired when humans penetrate a wild ecosystem or when wild triatomines invade human dwellings attracted by light or searching for human blood. The risk of endemic Chagas disease in the Amazon Region is associated with the following phenomena: (i) extensive deforestation associated with the displacement of wild mammals, which are the normal sources of blood for triatomines, (ii) adaptation of wild triatomines to human dwellings due to the need for a new source of blood for feeding and (iii) uncontrolled migration of human populations and domestic animals that are already infected with Trypanosoma cruzi from areas endemic for Chagas disease to the Amazon Region. Several outbreaks of severe acute cases of Chagas disease, as well as chronic cases, have been described in the Amazon Region. Control measures targeted to avoiding endemic Chagas disease in the Amazon Region should be the following: improving health education in communities, training public health officials and communities for vector and Chagas disease surveillance and training local physicians to recognise and treat acute and chronic cases of Chagas diseases as soon as possible.     

Bloodmeal analysis reveals avian Plasmodium infections and broad host preferences of Culicoides (Diptera: Ceratopogonidae) vectors

Changing environmental conditions and human encroachment on natural habitats bring human populations closer to novel sources of parasites, which might then develop into new emerging diseases. Diseases transmitted by host generalist vectors are of special interest due to their capacity to move pathogens into novel hosts. We hypothesize that humans using forests for recreation are exposed to a broad range of parasites from wild animals and their vectors. A corollary of this is that new vector-host, parasite-host, and vector-parasite associations could eventually develop. Thus, we expect to observe atypical vector-host associations. Using molecular bloodmeal analysis via amplification of the mtDNA COI gene we identified the vertebrate hosts of Culicoides (Diptera: Ceratopogonidae) species in a sub-urban forest of Southwestern Germany. Bloodmeals were also checked for haemosporidian infections by amplifying a fragment of the mtDNA cyt b gene. We identified a total of 20 Culicoides species, thirteen of which fed on humans. From 105 screened bloodmeals we obtained high quality sequences for 77 samples, 73 (94.8%) originated from humans, two from livestock (Bos taurus and Equus caballus), and two from wild birds (Sylvia atricapilla and Turdus merula). We found that four Culicoides species previously assumed to feed exclusively on either birds (C. kibunensis) or domestic mammals (C. chiopterus, C. deltus, C. scoticus) fed also on humans. A total of six Culicoides abdomens were infected with avian haemosporidian parasites (Plasmodium or Haemoproteus), four of those abdomens contained blood derived from humans. Our results suggest that parasites of wild animals may be transferred to humans through infectious bites of Culicoides vectors. Further, we show that Culicoides vectors believed to be a specialist on specific vertebrate groups can have plastic feeding preferences, and that Culicoides are susceptible to infection by Plasmodium parasites, though vector viability must still be experimentally demonstrated.