Summary Rabies is one of the most deadly infectious diseases, with a case-fatality rate approaching 100%. The disease is established on all continents apart from Antarctica; most cases are reported ...in Africa and Asia, with thousands of deaths recorded annually. However, the estimated annual figure of almost 60 000 human rabies fatalities is probably an underestimate. Almost all cases of human rabies result from bites from infected dogs. Therefore, the most cost-effective approach to elimination of the global burden of human rabies is to control canine rabies rather than expansion of the availability of human prophylaxis. Mass vaccination campaigns with parenteral vaccines, and advances in oral vaccines for wildlife, have allowed the elimination of rabies in terrestrial carnivores in several countries worldwide. The subsequent reduction in cases of human rabies in such regions advocates the multidisciplinary One Health approach to rabies control through the mass vaccination of dogs and control of canine populations.
•This review provides an overview of Japanese encephalitis virus (JEV) infection in livestock.•It discusses the virus vectors, their distribution and role in future spread of disease.•A comprehensive ...review of diagnostic methods including both veterinary and human testing regimes.•A section also deals with disease control and the importance of reducing disease in livestock to interrupt transmission to human populations.
Japanese encephalitis virus (JEV) is a significant cause of neurological disease in humans throughout Asia causing an estimated 70,000 human cases each year with approximately 10,000 fatalities. The virus contains a positive sense RNA genome within a host-derived membrane and is classified within the family Flaviviridae. Like many flaviviruses, it is transmitted by mosquitoes, particularly those of the genus Culex in a natural cycle involving birds and some livestock species. Spill-over into domestic animals results in a spectrum of disease ranging from asymptomatic infection in some species to acute neurological signs in others. The impact of JEV infection is particularly apparent in pigs. Although infection in adult swine does not result in symptomatic disease, it is considered a significant reproductive problem causing abortion, still-birth and birth defects. Infected piglets can display fatal neurological disease. Equines are also infected, resulting in non-specific signs including pyrexia, but occasionally leading to overt neurological disease that in extreme cases can lead to death. Veterinary vaccination is available for both pigs and horses. This review of JEV disease in livestock considers the current diagnostic techniques available for detection of the virus. Options for disease control and prevention within the veterinary sector are discussed. Such measures are critical in breaking the link to zoonotic transmission into the human population where humans are dead-end hosts.
Bats are the natural reservoirs of a number of high-impact viral zoonoses. We present a quantitative analysis to address the hypothesis that bats are unique in their propensity to host zoonotic ...viruses based on a comparison with rodents, another important host order. We found that bats indeed host more zoonotic viruses per species than rodents, and we identified life-history and ecological factors that promote zoonotic viral richness. More zoonotic viruses are hosted by species whose distributions overlap with a greater number of other species in the same taxonomic order (sympatry). Specifically in bats, there was evidence for increased zoonotic viral richness in species with smaller litters (one young), greater longevity and more litters per year. Furthermore, our results point to a new hypothesis to explain in part why bats host more zoonotic viruses per species: the stronger effect of sympatry in bats and more viruses shared between bat species suggests that interspecific transmission is more prevalent among bats than among rodents. Although bats host more zoonotic viruses per species, the total number of zoonotic viruses identified in bats (61) was lower than in rodents (68), a result of there being approximately twice the number of rodent species as bat species. Therefore, rodents should still be a serious concern as reservoirs of emerging viruses. These findings shed light on disease emergence and perpetuation mechanisms and may help lead to a predictive framework for identifying future emerging infectious virus reservoirs.
Bat flight and zoonotic viruses O'Shea, Thomas J; Cryan, Paul M; Cunningham, Andrew A ...
Emerging infectious diseases,
05/2014, Volume:
20, Issue:
5
Journal Article
Peer reviewed
Open access
Bats are sources of high viral diversity and high-profile zoonotic viruses worldwide. Although apparently not pathogenic in their reservoir hosts, some viruses from bats severely affect other ...mammals, including humans. Examples include severe acute respiratory syndrome coronaviruses, Ebola and Marburg viruses, and Nipah and Hendra viruses. Factors underlying high viral diversity in bats are the subject of speculation. We hypothesize that flight, a factor common to all bats but to no other mammals, provides an intensive selective force for coexistence with viral parasites through a daily cycle that elevates metabolism and body temperature analogous to the febrile response in other mammals. On an evolutionary scale, this host-virus interaction might have resulted in the large diversity of zoonotic viruses in bats, possibly through bat viruses adapting to be more tolerant of the fever response and less virulent to their natural hosts.
Microbiologic infections acquired from animals, known as zoonoses, pose a risk to public health. An estimated 60% of emerging human pathogens are zoonotic. Of these pathogens, >71% have wildlife ...origins. These pathogens can switch hosts by acquiring new genetic combinations that have altered pathogenic potential or by changes in behavior or socioeconomic, environmental, or ecologic characteristics of the hosts. We discuss causal factors that influence the dynamics associated with emergence or reemergence of zoonoses, particularly in the industrialized world, and highlight selected examples to provide a comprehensive view of their range and diversity.
Ebolaviruses (EBOV) (family Filoviridae) cause viral hemorrhagic fevers in humans and non-human primates when they spill over from their wildlife reservoir hosts with case fatality rates of up to ...90%. Fruit bats may act as reservoirs of the Filoviridae. The migratory fruit bat, Eidolon helvum, is common across sub-Saharan Africa and lives in large colonies, often situated in cities. We screened sera from 262 E. helvum using indirect fluorescent tests for antibodies against EBOV subtype Zaire. We detected a seropositive bat from Accra, Ghana, and confirmed this using western blot analysis. The bat was also seropositive for Lagos bat virus, a Lyssavirus, by virus neutralization test. The bat was fitted with a radio transmitter and was last detected in Accra 13 months after release post-sampling, demonstrating long-term survival. Antibodies to filoviruses have not been previously demonstrated in E. helvum. Radio-telemetry data demonstrates long-term survival of an individual bat following exposure to viruses of families that can be highly pathogenic to other mammal species. Because E. helvum typically lives in large urban colonies and is a source of bushmeat in some regions, further studies should determine if this species forms a reservoir for EBOV from which spillover infections into the human population may occur.
Domestic dogs are responsible for nearly all the »59,000 global human rabies deaths that occur annually. Numerous control measures have been successful at eliminating dog-mediated human rabies deaths ...in upper-income countries, including dog population management, parenteral dog vaccination programs, access to human rabies vaccines, and education programs for bite prevention and wound treatment. Implementing these techniques in resource-poor settings can be challenging; perhaps the greatest challenge is maintaining adequate herd immunity in free-roaming dog populations. Oral rabies vaccines have been a cornerstone in rabies virus elimination from wildlife populations; however, oral vaccines have never been effectively used to control dog-mediated rabies. Here, we convey the perspectives of the World Organisation for Animal Health Rabies Reference Laboratory Directors, the World Organisation for Animal Health expert committee on dog rabies control, and World Health Organization regarding the role of oral vaccines for dogs. We also issue recommendations for overcoming hesitations to expedited field use of appropriate oral vaccines.
The continued detection of zoonotic viral infections in bats has led to the microbial fauna of these mammals being studied at a greater level than ever before. Whilst numerous pathogens have been ...discovered in bat species, infection with lyssaviruses is of particular significance from a zoonotic perspective as, where human infection has been reported, it is invariably fatal. Here we review the detection of lyssaviruses within different bat species and overview what is understood regarding their maintenance and transmission following both experimental and natural infection. We discuss the relevance of these pathogens as zoonotic agents and the threat of newly discovered viruses to human populations.
Ticks and the pathogens they transmit constitute a growing burden for human and animal health worldwide. Vector competence is a component of vectorial capacity and depends on genetic determinants ...affecting the ability of a vector to transmit a pathogen. These determinants affect traits such as tick-host-pathogen and susceptibility to pathogen infection. Therefore, the elucidation of the mechanisms involved in tick-pathogen interactions that affect vector competence is essential for the identification of molecular drivers for tick-borne diseases. In this review, we provide a comprehensive overview of tick-pathogen molecular interactions for bacteria, viruses, and protozoa affecting human and animal health. Additionally, the impact of tick microbiome on these interactions was considered. Results show that different pathogens evolved similar strategies such as manipulation of the immune response to infect vectors and facilitate multiplication and transmission. Furthermore, some of these strategies may be used by pathogens to infect both tick and mammalian hosts. Identification of interactions that promote tick survival, spread, and pathogen transmission provides the opportunity to disrupt these interactions and lead to a reduction in tick burden and the prevalence of tick-borne diseases. Targeting some of the similar mechanisms used by the pathogens for infection and transmission by ticks may assist in development of preventative strategies against multiple tick-borne diseases.
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