Hepatitis E virus as an emerging zoonotic pathogen

Hepatitis E outbreaks are a serious public health concern in developing countries. The disease causes acute infections, primarily in young adults. The mortality rate is approximately 2%; however, it can exceed 20% in pregnant women in some regions in India. The causative agent, hepatitis E virus (HEV), has been isolated from several animal species, including pigs. HEV genotypes 3 and 4 have been isolated from both humans and animals, and are recognized as zoonotic pathogens. Seroprevalence studies in animals and humans indirectly suggest that HEV infections occur worldwide. The virus is primarily transmitted to humans via undercooked animal meats in developed countries. Moreover, transfusion- and transplantation-mediated HEV infections have recently been reported. This review summarizes the general characteristics of hepatitis E, HEV infection status in animals and humans, the zoonotic transmission modes of HEV, and HEV vaccine development status.     

First report of Enterocytozoon bieneusi infection on a pig farm in the Czech Republic

Enterocytozoon bieneusi infects humans and animals and can cause life-threatening diarrhea in immunocompromised people. The routes of transmission and its zoonotic potential are not fully understood. Pigs have been frequently reported to have E. bieneusi; therefore, we surveyed farm-raised pigs in the Czech Republic to determine its presence and genetic diversity. Spores were detected by microscopy in the faeces of 65 out of 79 examined animals (82%). A species-specific polymerase chain reaction (PCR) identified E. bieneusi in 94% of samples. Genotyping based on the ITS regions of the SSU rRNA gene identified that most pigs were infected with the species-specific genotype F, while two animals had the zoonotic genotype D and two had genotype Peru 9. This is the first report of E. bieneusi in swine in the Czech Republic, and demonstrated that most infections were with pig-specific genotypes. Nonetheless, swine may still play a role in the transmission of E. bieneusi to humans.     

Zoonotic aspects of Mycobacterium bovis and Mycobacterium avium-intracellulare complex (MAC)

Pathogens that are transmitted between the environment, wildlife, livestock and humans represent major challenges for the protection of human and domestic animal health, the economic sustainability of agriculture, and the conservation of wildlife. Among such pathogens, the genus Mycobacterium is well represented by M. bovis, the etiological agent of bovine tuberculosis, M. avium ssp. paratuberculosis (Map) the etiological agent of Johne disease, M. avium ssp. avium (Maa) and in a few common cases by other emergent environmental mycobacteria. Epidemiologic surveys performed in Europe, North America and New Zealand have demonstrated the existence and importance of environmental and wildlife reservoirs of mycobacterial infections that limit the attempts of disease control programmes. The aim of this review is to examine the zoonotic aspects of mycobacteria transmitted from the environment and wildlife. This work is focused on the species of two main groups of mycobacteria classified as important pathogens for humans and animals: first, M. bovis, the causative agent of bovine tuberculosis, which belongs to the M. tuberculosis complex and has a broad host range including wildlife, captive wildlife, domestic livestock, non-human primates and humans; the second group examined, is the M. avium-intracellulare complex (MAC) which includes M. avium ssp. avium causing major health problems in AIDS patients and M. avium ssp. paratuberculosis the etiological agent of Johne disease in cattle and identified in patients with Crohn disease. MAC agents, in addition to a broad host range, are environmental mycobacteria found in numerous biotopes including the soil, water, aerosols, protozoa, deep litter and fresh tropical vegetation. This review examines the possible reservoirs of these pathogens in the environment and in wildlife, their role as sources of infection in humans and animals and their health impact on humans. The possibilities of control and management programmes for these mycobacterial infections are examined with regards to the importance of their natural reservoirs.     

Prevalence and molecular characterization of Giardia duodenalis and Cryptosporidium spp. in dairy cattle in Ontario, Canada

Giardia duodenalis and Cryptosporidium spp. are intestinal protozoan parasites that infect a wide range of host species, including humans. Molecular characterization of these parasites has demonstrated that a number of genotypes and species are common to both humans and animals, and that zoonotic transmission may occur. Numerous studies have reported a high prevalence of G. duodenalis and Cryptosporidium spp. in cattle, particularly calves, and these animals are frequently associated with zoonotic transmission. In the present study, a total of 143 faecal samples from adults, heifers and calves were collected from two dairy cattle farms in eastern Ontario, Canada. The prevalence and molecular characteristics of G. duodenalis and Cryptosporidium spp. in these animals were determined in order to investigate the potential for transmission between cattle and humans in this region. Following DNA extractions from faecal samples, nested-PCR protocols were used to amplify fragments of the 16S rRNA gene and the heat-shock protein 70 (HSP-70) gene for determining the prevalence of G. duodenalis and Cryptosporidium spp. infections, respectively. Genotypes of G. duodenalis, and species of Cryptosporidium, were determined by means of DNA sequencing of amplicons, and subsequent sequence alignment. Cattle on both farms showed a high prevalence of G. duodenalis (42.0%) and Cryptosporidium spp. (27.3%). G. duodenalis infections were more prevalent in calves and heifers than in adults, and Cryptosporidium spp. infections were only observed in calves and heifers. The zoonotic genotype, G. duodenalis Assemblage B was isolated from 24.5% of the cattle tested, while G. duodenalis Assemblage E was found in 17.5% of the cattle tested. The overall prevalence of the zoonotic species Cryptosporidium parvum in the animals tested was found to be 21.7%, while only 1.4% were infected with C. bovis. These findings suggest that there is a potential risk of zoonotic and/or zooanthroponotic transmission of G. duodenalis and C. parvum infections between cattle and humans in eastern Ontario, likely by means of contaminated water or food, or through direct faecal-oral transmission in the case of farmers and veterinary staff.     

Comparative immunological and microbiological aspects of paratuberculosis as a model mycobacterial infection

Paratuberculosis or Johne's disease of livestock, which is caused by Mycobacterium avium subsp. paratuberculosis (MAP), has increased in prevalence and expanded in geographic and host ranges over about 100 years. The slow and progressive spread of MAP reflects its substantial adaptation to its hosts, the technical limitations of diagnosis, the lack of practical therapeutic approaches, the lack of a vaccine that prevents transmission and the complexity and difficulty of the on-farm control strategies needed to prevent infection. More recently evidence has accumulated for an association of MAP with Crohn's disease in humans, adding to the pressure on animal health authorities to take precautions by controlling paratuberculosis. Mycobacterial infections invoke complex immune responses but the essential determinants of virulence and pathogenesis are far from clear. In this review we compare the features of major diseases in humans and animals that are caused by the pathogenic mycobacteria M. ulcerans, M. avium subsp. avium, M. leprae, M. tuberculosis and MAP. We seek to answer key questions: are the common mycobacterial infections of humans and animals useful "models" for each other, or are the differences between them too great to enable meaningful extrapolation? To simplify this, the immunopathogenesis of mycobacterial infections will be defined at cellular, tissue, animal and population levels and the key events at each level will be discussed. Many pathogenic processes are similar between divergent mycobacterial diseases, and at variance between virulent and avirulent isolates of mycobacteria, suggesting that the research on the pathogenesis of one mycobacterial disease will be informative for the others.     

Zoonotic poxviruses

Poxviruses compromise a group of long known important pathogens including some zoonotic members affecting lifestock animals and humans. While whole genome sequence analysis started to shed light into the molecular mechanisms underlying host cell infection, viral replication as well as virulence, our understanding of poxvirus maintenance in nature and their transmission to humans is still poor. During the last two decades, reports on emerging human monkeypox outbreaks in Africa and North America, the increasing number of cowpox virus infections in cats, exotic animals and humans and cases of vaccinia virus infections in humans in South America and India reminded us that – beside the eradicated smallpox virus – there are other poxviruses that can cause harm to men. We start to learn that the host range of some poxviruses is way broader than initially thought and that mainly rodents seem to function as virus reservoir. The following review is aiming to provide an up-to-date overview on the epidemiology of zoonotic poxviruses, emphasizing orthopoxviruses. By outlining the current knowledge of poxvirus transmission, we hope to raise the awareness about modes of acquisition of infections and their proper diagnosis.     

Emerging enterohaemorrhagic Escherichia coli, causes and effects of the rise of a human pathogen

Shiga toxin (Stx) [Verotoxin (VT)]-producing Escherichia coli (STEC), also called enterohaemorrhagic E. coli or VTEC are emerging zoonotic agents and became most important as human pathogens, particularly in the industrialized countries. Production of cytotoxins, also called Stx or VT, is the major pathogenicity determinant of STEC, which can cause life-threatening haemorrhagic diseases in humans. The spectrum of STEC phenotypes is diverse and domestic and wildlife animals constitute important reservoirs for these bacteria. STEC are spread from animal faeces to the environment, water and food. Ingestion of contaminated foodstuff and water, as well as contact with the environment, STEC-excreting animals or humans are the major sources of human infection. Economical changes in animal and food production, alteration of consumer habits and lack of specific immune response, particularly in urbanized populations, have contributed to the recent spread of STEC as a zoonotic agent. Supranational surveillance networks as well as national reference laboratories as sentinels play an important role in the prevention and control of STEC infections in humans. Development of new vaccines and probiotics may serve as future tools to control the spread of STEC in animals and humans.     

Survey and molecular characterization of Cryptosporidium and Giardia spp. in owned companion animal, dogs and cats, in Japan

Compared with other countries, surveys of these parasites have been rarely performed in companion animals of Japan in spite of their significance for public health. Here, we investigated pet dogs and cats in Japan for the first time, and genetically analyzed the isolates to evaluate the risk of zoonotic infections. Seventy-seven fecal samples were collected from privately owned dogs and 55 samples from owned cats in Osaka city, Japan. Cryptosporidium oocysts were identified in 3/77 dogs (3.9%) and 7/55 cats (12.7%), and Giardia infection in 2/77 dogs (2.6%) and 1/55 cats (1.8%). Amplification of the target regions for genotyping was successful, Cryptosporidium isolates in dogs and cats were identified as C. canis and C. felis, respectively, and those of Giardia in dogs and cats were G. intestinalis Assemblages D and F. The discharge period of the oocysts varied within 3-16 weeks and that of the cysts was 12 weeks. To date, zoonotic types of both parasites have been identified in other animals in Japan, and further large-scale studies are needed to determine the distribution of zoonotic genotypes in these animals, especially those closely associated with humans.     

DNA-based detection of Leptospira wolffii,Giardia intestinalis and Toxoplasma gondii in environmental feces of wild animals in Korea

Leptospira, Giardia intestinalis and Toxoplasma gondii infections are reported in humans and animals worldwide, but molecular surveillance of these pathogens in Korean wildlife is still limited. Here, we examined the prevalence of these pathogens in environmental feces of Eurasian otters, leopard cats and raccoon dogs using nested PCR followed by DNA sequencing. G. intestinalis was detected in all of three animals, while T. gondii was detected only in leopard cats. Leptospira wolffii was detected in raccoon dog and Eurasian otter. Our results suggest that these animals can act as a reservoir of these zoonotic pathogens. Consistent monitoring of these pathogens in wildlife is needed to prevent from their infections in humans and livestock in Korea.     

The zoonotic significance and molecular epidemiology of Giardia and giardiasis

The taxonomy and molecular epidemiology of Giardia and Giardia infections are reviewed in the context of zoonotic and waterborne transmission. Evidence to support the zoonotic transmission of Giardia is very strong, but how frequent such transmission occurs and under what circumstances, have yet to be determined. Zoonotic origin for waterborne outbreaks of Giardia infection appears to be uncommon. Similarly, livestock are unlikely to be an important source of infection in humans. The greatest risk of zoonotic transmission appears to be from companion animals such as dogs and cats, although further studies are required in different endemic foci in order to determine the frequency of such transmission.     

Zoonotic aspects of infections with noroviruses and sapoviruses

The close genetic relationship of noroviruses and sapoviruses found in animals and humans has raised the question whether these viruses have a zoonotic potential. Transmission from animals to humans and vice versa would have far-reaching consequences for epidemiology and food safety. So far animal noro- and sapoviruses have not been found in humans. However detection of human noroviruses in animals as well as simultaneous presence of animal and human viruses in bivalve molluscs suggest a risk of transmission. Furthermore, antibodies against animal noroviruses were detected in humans as well as antibodies against human noroviruses in swine. Experimental infection of gnotobiotic calves and pigs with human noroviruses demonstrated that virus replication and seroconversion can occur. Accordingly the possible role of noro- and sapoviruses as zoonotic agents needs to be further investigated.     

动物脑多头蚴病研究进展

脑多头蚴病是由多头绦虫的幼虫寄生于家畜所引起的疾病,人也可感染,但相对较少。该病通常对动物是致命的,给世界许多地区的养殖业造成了巨大的经济损失。论文主要介绍了不同药物对该病的疗效,以及脑多头蚴不同抗原成分免疫原性、分子分类和相关抗原基因的研究进展。     

Discussion of the Compendium of Veterinary Standard Precautions: preventing zoonotic disease transmission in veterinary personnel

Veterinary practices are unique environments that bring humans into close contact with many different species of animals; therefore, the risk of exposure to infectious pathogens is inherently different in veterinary medicine than in human medicine. In contrast to the risk of exposure to blood in human medicine, infections from zoonotic diseases in veterinary personnel are primarily related to exposure to animal faeces, infected skin, wounds, droplets and puncture wounds. Infection-control measures in veterinary practices are often insufficient to prevent zoonotic disease transmission. The Veterinary Standard Precautions (VSP) Compendium is designed to help prevent transmission of zoonotic pathogens from animal patients to veterinary personnel in private practice.     

Methicillin‐resistant Staphylococcus aureus in dogs and cats: an emerging problem?

There is concern over transmission of methicillin-resistant Staphylococcus aureus (MRSA) between animals and humans. The spread of hospital-acquired and community-acquired MRSA is a major challenge in human medicine. MRSA is rarely isolated from animals but methicillin resistance occurs in staphylococci that are more prevalent in animals. MRSA infections in animals are uncommon and most are associated with exposure to medical hospitals, extensive wounds, prolonged hospitalisation and immunosuppression. The risk to human health appears to be small but a survey of methicillin-resistant staphylococci in animals is required. Thorough investigation of possible zoonotic infections to establish linkage is encouraged. Medical and veterinary staff should appreciate that animals can carry MRSA, cooperate in eliminating infections and monitor animals in medical environments. Veterinary clinics should implement guidelines for dealing with MRSA. Responsible antibiotic use should minimise the spread of antibiotic resistance but a UK monitoring scheme is desirable.     

The management of risk arising from the use of antimicrobial agents in veterinary medicine in EU/EEA countries – a review

Antimicrobials are essential medicines for the treatment of many microbial infections in humans and animals. Only a small number of antimicrobial agents with new mechanisms of action have been authorized in recent years for use in either humans or animals. Antimicrobial resistance (AMR) arising from the use of antimicrobial agents in veterinary medicine is a concern for public health due to the detection of increasing levels of resistance in foodborne zoonotic bacteria, particularly gram‐negative bacteria, and due to the detection of determinants of resistance such as Extended‐spectrum beta‐lactamases (ESBL) in bacteria from animals and in foodstuffs of animal origin. The importance and the extent of the emergence and spread of AMR from animals to humans has yet to be quantified. Likewise, the relative contribution that the use of antimicrobial agents in animals makes to the overall risk to human from AMR is currently a subject of debate that can only be resolved through further research. Nevertheless, risk managers have agreed that the impact on public health of the use of antimicrobials in animals should be minimized as far as possible and a variety of measures have been introduced by different authorities in the EU to achieve this objective. This article reviews a range of measures that have been implemented within European countries to reduce the occurrence and the risk of transmission of AMR to humans following the use of antimicrobial agents in animals and briefly describes some of the alternatives to the use of antimicrobial agents that are being developed.     

The socioeconomic burden of parasitic zoonoses: global trends

Diseases resulting from zoonotic transmission of parasites are common. Humans become infected through food, water, soil and close contact with animals. Most parasitic zoonoses are neglected diseases despite causing a considerable global burden of ill health in humans and having a substantial financial burden on livestock industries. This review aims to bring together the current data available on global burden estimates of parasitic zoonoses and indicate any changes in the trends of these diseases. There is a clear need of such information as interventions to control zoonoses are often in their animal hosts. The costs of such interventions together with animal health issues will drive the cost effectiveness of intervention strategies. What is apparent is that collectively, parasitic zoonoses probably have a similar human disease burden to any one of the big three human infectious diseases: malaria, tuberculosis or HIV in addition to animal health burden. Although the global burden for most parasitic zoonoses is not yet known, the major contributors to the global burden of parasitic zoonoses are toxoplasmosis, food borne trematode infections, cysticercosis, echinococcosis, leishmaniosis and zoonotic schistosomosis. In addition, diarrhoea resulting from zoonotic protozoa may have a significant impact.     

One Health as a moral dilemma: Towards a socially responsible zoonotic disease control

During the last decade, the concept of One Health has become the international standard for zoonotic disease control. This call for transdisciplinary collaboration between professionals in human, animal and environmental health has produced several successes in zoonotic disease control, surveillance and research. Despite the lack of a clear definition, a shared agenda or institutional governance, One Health has proven to be a fruitful idea. Due to its ambiguity, the One Health concept functions as a boundary object: by leaving room for interpretation to fit different purposes, it facilitates cooperation. In many cases, this results in the promotion of health of humans, animals and the environment. However, there are also situations in which this mutual benefit of a One Health approach is not that evident, for instance, when healthy animals are culled to protect public health. Although such a strategy could well be part of a One Health approach, it is hard to understand how this contributes to the health of concerning animals. Consequently, these practices often lead to public debate. This raises questions on how we should understand the One Health concept in zoonotic disease control. Is it really about equally improving the health of humans, animals and the environment and is this even possible? Or is it ultimately just public health that counts? In cases of conflict between different values, the lack of a universal definition of the One Health concept contributes to this complexity. Although boundary objects have many positive aspects, in the context of One Health and zoonotic disease control, this conception seems to conceal underlying normative differences. To address moral dilemmas related to a One Health approach in zoonotic disease control, it is important to reflect on moral status and the meaning of health for humans, animals and the environment.     

Hepatitis E in southern Vietnam: Seroepidemiology in humans and molecular epidemiology in pigs

Viral pathogens account for a significant proportion of the burden of emerging infectious diseases in humans. The Wellcome Trust‐Vietnamese Initiative on Zoonotic Infections (WT‐VIZIONS) is aiming to understand the circulation of viral zoonotic pathogens in animals that pose a potential risk to human health. Evidence suggests that human exposure and infections with hepatitis E virus (HEV) genotypes (GT) 3 and 4 results from zoonotic transmission. Hypothesising that HEV GT3 and GT4 are circulating in the Vietnamese pig population and can be transmitted to humans, we aimed to estimate the seroprevalence of HEV exposure in a population of farmers and the general population. We additionally performed sequence analysis of HEV in pig populations in the same region to address knowledge gaps regarding HEV circulation and to evaluate if pigs were a potential source of HEV exposure. We found a high prevalence of HEV GT3 viral RNA in pigs (19.1% in faecal samples and 8.2% in rectal swabs) and a high HEV seroprevalence in pig farmers (16.0%) and a hospital‐attending population (31.7%) in southern Vietnam. The hospital population was recruited as a general‐population proxy even though this particular population subgroup may introduce bias. The detection of HEV RNA in pigs indicates that HEV may be a zoonotic disease risk in this location, although a larger sample size is required to infer an association between HEV positivity in pigs and seroprevalence in humans.     

Molecular and phylogenetic analysis of Blastocystis isolates from various hosts

Blastocystis hominis is a protozoan parasite found in humans. B. hominis-like organisms have been found in a variety of animals, but have been called Blastocystis sp. because the isolates from animals were indistinguishable from B. hominis morphologically. Recent molecular studies show that some isolates from animals have genetic similarity with B. hominis. However, it has been unclear whether the isolates from animals have zoonotic potential or not. In the present study, the SSUrDNA of 19 Blastocystis isolates from these animals was sequenced in its entirety, and the phylogenetic relationship among isolates from humans and animals was clarified using available nucleotide sequences of the same locus. Phylogenetic analysis showed that the 19 isolates analyzed in the present study could be classified into seven groups (I-VII): Group I consisted of the isolates from humans, primates, cattle, pigs and birds; Group II of the isolates from humans and primates; Group III of the isolates from humans, cattle and pigs; Group IV of the isolates from primates, birds and rodents; Group V of the isolates from cattle and pigs; Groups VI and VII of the isolates from humans and birds. These results indicate that many of the isolates harboring in animals have zoonotic potential, or have cross-transmissibility among heterogeneous hosts.     

Epidemiological study of people living in rural North Carolina for novel respiratory viruses

During the last 10 years, scientists have grown increasingly aware that emerging respiratory viruses are often zoonotic in their origin. These infections can originate from or be amplified in livestock. Less commonly recognized are instances when humans have transmitted their respiratory pathogens to animals (reverse zoonoses). Even with this knowledge of viral exchange at the human–livestock interface, few studies have been conducted to understand this cross‐over. In this pilot study, we examined persons with influenza‐like illness at an outpatient clinic for evidence of infection with novel zoonotic respiratory pathogens in rural North Carolina where there are dense swine and poultry farming. Environmental air sampling was also conducted. From July 2016 to March 2017, a total of 14 human subjects were enrolled and sampled, and 192 bioaerosol samples were collected. Of the 14 human subject samples molecularly tested, three (21.4%) were positive for influenza A, one (7.1%) for influenza B and one (7.1%) for human enterovirus. Of the 192 bioaerosol samples collected and tested by real‐time RT‐PCR or PCR, three (1.6%) were positive for influenza A and two (1.0%) for adenovirus. No evidence was found for novel zoonotic respiratory viruses.