Long term stability and infectivity of herpesviruses in water

Evaluation of Non-Invasive Sampling Techniques for the Molecular Surveillance of Equid Herpesviruses in Yearling Horses

BACKGROUND

Equid alphaherpesvirus 1 (EHV-1) is a highly contagious respiratory tract pathogen of horses, and infection may be followed by myeloencephalopathy or abortion. Surveillance and early detection have focused on PCR assays using less tolerated nasal swabs. Here, we assess non-invasive non-contact sampling techniques as surveillance tools in naturally equid gammaherpesvirus 2-shedding horses as surrogates for EHV-1.

METHODS

Horses were individually housed for 10 h periods on 2 consecutive days. Sampling included nasal swabs, nostril wipes, environmental swabs, droplet-catching devices, and air sampling. The latter was completed via two strategies: a combined air sample collected while going from horse to horse and a collective air sample collected at a stationary central point for 6 h. Samples were screened through quantitative PCR and digital PCR.

RESULTS

Nine horses on day 1 and 11 horses on day 2 were positive for EHV-1; overall, 90.9% of the nostril wipes, 81.8% of the environmental surfaces, and 90.9% of the droplet-catching devices were found to be positive. Quantitative analysis showed that the mean DNA copies detection per cm2 of nostril wipe sampled concentration (4.3 × 105 per day) was significantly (p < 0.05) comparable to that of nasal swabs (3.6 × 105 per day) followed by environmental swabs (4.3 × 105 per day) and droplet catchers (3.5 × 103 per day), respectively. Overall, 100% of the air samples collected were positive on both qPCR and dPCR. In individual air samples, a mean concentration of 1.0 × 104 copies of DNA were detected in per m3 air sampled per day, while in the collective air samples, the mean concentration was 1.1 × 103.

CONCLUSIONS

Environmental samples look promising in replacing direct contact sampling. Environmental and air sampling could become efficient surveillance tools at equestrian events; however, it needs threshold calculations for minimum detection levels.

Updated ACVIM consensus statement on equine herpesvirus-1

Equine herpesvirus-1 (EHV-1) is a highly prevalent and frequently pathogenic infection of equids. The most serious clinical consequences of infection are abortion and equine herpesvirus myeloencephalopathy (EHM). The previous consensus statement was published in 2009 and considered pathogenesis, strain variation, epidemiology, diagnostic testing, vaccination, outbreak prevention and control, and treatment. A recent survey of American College of Veterinary Internal Medicine large animal diplomates identified the need for a revision to this original consensus statement. This updated consensus statement is underpinned by 4 systematic reviews that addressed key questions concerning vaccination, pharmaceutical treatment, pathogenesis, and diagnostic testing. Evidence for successful vaccination against, or effective treatment of EHV-1 infection was limited, and improvements in experimental design and reporting of results are needed in future studies of this important disease. This consensus statement also updates the topics considered previously in 2009.

Medical management and positive outcome after prolonged recumbency in a case of equine herpesvirus myeloencephalopathy

A 17-year-old mare presenting with acute fever, weakness and bladder dysfunction was diagnosed with equine herpesvirus myeloencephalopathy (EHM). The mare become transiently recumbent, underwent parenteral fluid therapy, plasma infusion, steroidal/nonsteroidal anti-inflammatory drugs (SAID/NSAIDs) and bladder catheterization. After 10 days the mare was hospitalized. Neurological evaluation revealed ataxia and proprioceptive deficits mainly in the hind limbs. The mare was able to stand but unable to rise from recumbency or walk. Secondary complications included Escherichia coli cystitis, corneal ulcers and pressure sores. A full-body support sling was used for 21 days. Medical treatment included systemic antimicrobials, NSAIDs, gradual discontinuation of SAIDs, parenteral fluid therapy and bladder lavage. The mare tested positive for Varicellovirus equidalpha 1 (EHV-1) DNA in nasal swab and blood samples on day 13 and in urine samples on days 13 and 25 after the onset of fever. Neurological signs improved over a period of 34 days and the mare was discharged with mild hind limb weakness/ataxia. Secondary complications resolved within 2 weeks. At the eight-month follow-up, marked improvement in locomotory function had been achieved.

Detection and Phylogenetic Analysis of Orf Virus and Muskox Rhadinovirus 1 from Muskoxen (Ovibos moschatus) in the Canadian Arctic

Orf virus (genus Parapoxvirus) has been associated with gross skin lesions on muskoxen (Ovibos moschatus) from Victoria Island, Nunavut, Canada, where muskox populations are experiencing population declines. Orf virus causes painful proliferative and necrotizing dermatitis upon viral replication and shedding, which may lead to animal morbidity or mortality through secondary infections and starvation. Herpesvirus, known to cause gross lesions on skin and mucosa during active viral replication, has also been documented in muskoxen but to date has not been associated with clinical disease. Our objective was to characterize the variation of orf virus and herpesvirus in wild muskoxen of the Canadian Arctic. Tissue samples including gross skin lesions from the nose, lips, and/or legs were opportunistically collected from muskoxen on Victoria Island, Nunavut and Northwest Territories, and mainland Nunavut, Canada, from 2015 to 2017. Sampled muskoxen varied in age, sex, location, hunt type, and body condition. Tissues from 60 muskoxen were tested for genetic evidence of orf virus and herpesvirus infection using PCR targeting key viral genes. Tissues from 38 muskoxen, including 15 with gross lesions, were also examined for histological evidence of orf virus and herpesvirus infection. Eleven muskoxen (10 from Victoria Island and one from mainland Nunavut) with gross lesions had microscopic lesions consistent with orf virus infection. Muskox rhadinovirus 1, a gammaherpesvirus endemic to muskoxen, was detected in 33 (55%) muskoxen including 17 with gross lesions. In all tissues examined, there was no histological evidence of herpesvirus-specific disease. Sequencing and characterization of amplified PCR products using phylogenetic analysis indicated that a strain of orf virus, which appears to be unique, is likely to be endemic in muskoxen from Victoria Island and mainland Nunavut. Many of the muskoxen are also subclinically infected with a known muskox-endemic strain of herpesvirus.

Detection of Selected Equine Respiratory Pathogens in Stall Samples Collected at a Multi-Week Equestrian Show during the Winter Months

The aim of this study was to use environmental sampling to determine the frequency of detection of selected equine respiratory viruses and bacteria in horses attending a multi-week equestrian show during the winter months. At four time points during showing, environmental sponge samples were collected from all stalls on the property and tested for the presence of equine herpesvirus-1 (EHV-1), EHV-2, EHV-4, equine influenza virus (EIV), equine rhinitis B virus (ERBV), Streptococcus equi ss. equi (S. equi), and S. equi ss. zooepidemicus (S. zooepidemicus) using real-time PCR (PCR). Environmental sponges were collected from all 53 barns by using one sponge for up to 10 stalls. Further, 2/53 barns were randomly selected for individual stall sampling in order to compare the results between individual and pooled stall samples. A total of 333/948 (35.13%, 95% CI 32.09-38.26%) pooled environmental stall sponges tested PCR-positive for at least one of the selected respiratory pathogens. Streptococcus zooepidemicus was the most commonly detected pathogen in pooled samples (28.69%, 95% CI 25.83-31.69%), followed by EHV-2 (14.45%, 95% CI 12.27-16.85%), EHV-4 (1.37%, 95% CI 0.73-2.33%), and a very small percentage of pooled stall sponges tested PCR-positive for EHV-1, ERBV, EIV, and S. equi. In individual samples, 171/464 (36.85%, 95% CI 32.45-41.42%) environmental stall sponges tested PCR-positive for at least one of the selected pathogens, following a similar frequency of pathogen detection as pooled samples. The detection frequency of true respiratory pathogens from environmental samples was higher during the winter months compared to previous studies performed during spring and summer, and this testing highlights that such pathogens circulate with greater frequency during the colder months of the year. The strategy of monitoring environmental stall samples for respiratory pathogens circumvents the often labor-intensive collection of respiratory secretions from healthy horses and allows for a more efficient assessment of pathogen buildup over time. However, environmental stall testing for respiratory pathogens should not replace proper biosecurity protocols, but it should instead be considered as an additional tool to monitor the silent circulation of respiratory pathogens in at-risk horses.

First description of a lesion in the upper digestive mucosa associated with a novel gammaherpesvirus in a striped dolphin (Stenella coeruleoalba) stranded in the Western Mediterranean Sea

BACKGROUND

A wide variety of lesions have been associated with herpesvirus in cetaceans. However, descriptions of herpesvirus infections in the digestive system of cetaceans are scarce.

CASE REPORT

A young female striped dolphin stranded in the Valencian Community (Spain) on the 6th August 2021. The animal showed external macroscopic lesions suggestive of an aggressive interaction with bottlenose dolphins (rake marks in the epidermis). Internally, the main findings included congestion of the central nervous system and multiple, well-defined, whitish, irregularly shaped, proliferative lesions on the oropharyngeal and laryngopharyngeal mucosa. Histopathology revealed lymphoplasmacytic and histiocytic meningoencephalitis, consistent with neuro brucellosis. The oropharyngeal and laryngopharyngeal plaques were comprised histologically of focally extensive epithelial hyperplasia. As part of the health surveillance program tissue samples were tested for cetacean morbillivirus using a real-time reverse transcription-PCR, for Brucella spp. using a real-time PCR, and for herpesvirus using a conventional nested PCR. All samples were negative for cetacean morbillivirus; molecular positivity for Brucella spp. was obtained in pharyngeal tonsils and cerebrospinal fluid; herpesvirus was detected in a proliferative lesion in the upper digestive mucosa. Phylogenetic analysis showed that the herpesvirus sequence was included in the Gammaherpesvirinae subfamily. This novel sequence showed the greatest identity with other Herpesvirus sequences detected in skin, pharyngeal and genital lesions in five different species.

CONCLUSIONS

To the best of the authors' knowledge, this is the first report of a proliferative lesion in the upper digestive mucosa associated with gammaherpesvirus posititvity in a striped dolphin (Stenella coeruleoalba).

Molecular Monitoring of EHV-1 in Silently Infected Performance Horses through Nasal and Environmental Sample Testing

While the main goal in the management of an EHM outbreak focuses on identifying early clinical disease in order to physically separate infected horses, little effort is placed towards monitoring healthy horses. The assumption that EHV-1 shedding parallels clinical disease is erroneous, as subclinical shedders have been shown to be actively involved in viral spread. In an attempt to document the frequency of EHV-1 shedders and their impact on environmental contamination, we collected nasal swabs from 231 healthy horses and 203 environmental samples for the testing of EHV-1 by qPCR. Six horses and 28 stalls tested qPCR-positive for EHV-1. There was no association in the EHV-1 qPCR-positive status between nasal and stall swabs. While testing nasal secretions of healthy at-risk horses can detect active shedding at a specific time point, the testing of stall swabs allows to assess the temporal EHV-1 shedding status of a horse. The study results highlight the risk of subclinical EHV-1 shedders and stalls occupied by these horses as sources of infection for susceptible horses. The testing of individual stalls for the presence of EHV-1 may be a more practical approach than the collection of individual nasal swabs for the monitoring and early detection of the circulating virus. The results also highlight the need to improve the cleanliness and disinfection of stalls utilized by performance horses during show events.

Investigation of the Use of Non-Invasive Samples for the Molecular Detection of EHV-1 in Horses with and without Clinical Infection

The purpose of this study was to explore sampling options for a reliable and logistically more feasible protocol during a large EHV-1 outbreak. Seventeen horses with clinical infection as well as nineteen healthy herdmates, all part of an EHM outbreak, were enrolled in the study. Each horse was sampled two–four times at intervals of 2–6 days during the outbreak. All samples were collected using 6′′ rayon-tipped swabs. Nasal secretions were used as the diagnostic sample of choice. Additional samples, including swabs from the muzzle/nares, swabs from the front limbs, rectal swabs, swabs of the feed bin, and swabs of the water troughs were collected as well. All swabs were tested for the presence of EHV-1 by qPCR. With the exception of two EHV-1 qPCR-positive swabs from two different horses, all remaining swabs collected from healthy herdmates tested qPCR-negative for EHV-1. For horses with clinical infection, EHV-1 was detected in 31 nasal swabs, 30 muzzle/nares swabs, 7 front limb swabs, 7 feeders, 6 water troughs and 6 rectal swabs. Not all positive muzzle/nares swabs correlated with a positive nasal swab from the same set, however, and all other positive swabs did correlate with a positive nasal swab in their respective set. The agreement between nasal swabs and muzzle/nares swabs was 74%. The sampling of non-invasive swabs from the muzzle/nares should facilitate the identification of EHV-1 shedders during an outbreak, allowing for prompt isolation and implementation of biosecurity measures.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): infection with Equine Herpesvirus-1

Equine Herpesvirus-1 infection has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of: Article 7 on disease profile and impacts, Article 5 on the eligibility of the disease to be listed, Article 9 for the categorisation of the disease according to disease prevention and control measures as in Annex IV and Article 8 on the list of animal species related to Equine Herpesvirus-1 infection. The assessment has been performed following a methodology composed of information collection and compilation, and expert judgement on each criterion at individual and collective level. The outcome is the median of the probability ranges provided by the experts, which indicates whether the criterion is fulfilled (66-100%) or not (0-33%), or whether there is uncertainty about fulfilment (33-66%). For the questions where no consensus was reached, the different supporting views are reported. According to the assessment performed, Equine Herpesvirus-1 infection can be considered eligible to be listed for Union intervention according to Article 5 of the Animal Health Law with 33-90% certainty. According to the criteria as in Annex IV of the AHL related to Article 9 of the AHL for the categorisation of diseases according to the level of prevention and control, it was assessed with less than 1% certainty that EHV-1 fulfils the criteria as in Section 1 (category A), 1-5% for the criteria as in Section 2 (category B), 10-66% for the criteria as in Section 3 (category C), 66-90% for the criteria as in Section 4 (category D) and 33-90% for the criteria as in Section 5 (category E). The animal species to be listed for EHV-1 infection according to Article 8(3) criteria are the species belonging to the families of Equidae, Bovidae, Camelidae, Caviidae, Cervidae, Cricetidae, Felidae, Giraffidae, Leporidae, Muridae, Rhinocerontidae, Tapiridae and Ursidae.

Systematic Review and Meta-Analysis of the Persistence of Enveloped Viruses in Environmental Waters and Wastewater in the Absence of Disinfectants

Enveloped viruses are characterized by a lipid-containing envelope that encapsulates the virion, and they have been the cause of major outbreaks and pandemics. Some enveloped viruses are excreted in feces and other bodily fluids of infected people and animals, raising the question of their fate in the aquatic environment. Consequently, we conducted a systematic review and meta-analysis of the decay rate constants (k) of enveloped viruses from 12 families (i.e., Coronaviridae, Cystoviridae (specifically Phi6), Filoviridae, Hepadnaviridae, Herpesviridae, Orthomyxoviridae, Paramyxoviridae, Pneumoviridae, Poxviridae, Retroviridae, Rhabdoviridae, Togaviridae) in environmental waters and wastewater to evaluate their decay kinetics and identify the environmental and virus characteristics that influence k. A total of 812 k that met inclusion criteria were identified in the literature, with the number of k for each family ranging from 0 to 560, and the virus family averaged values of k ranging from 0.11 d^-1 and 1.85 d^-1. Virus type (i.e., genus, species, subspecies, or subtype), method of virus enumeration (i.e., culture-based or (RT-)QPCR), and experimental water matrix type, temperature and sterility were found to have significant effects on k. Additionally, enveloped viruses were found to have statistically significantly greater k than nonenveloped viruses. Multiple linear regression models that allow prediction of log₁₀k as a function of virus type, enumeration method, water temperature, and water type are provided for six virus families that had sufficient data available for model fitting (i.e., Coronaviridae, Phi6, Herpesviridae, Orthomyxoviridae, Rhabdoviridae, Togaviridae). Compiled log₁₀k and multiple regression models can be used to inform management of human and animal waste, operation of water and wastewater facilities, and exposure risks to treatment plant workers and communities living in regions that lack treatment facilities. Given limited data available for some enveloped virus families with a potential water-related transmission route, there is need for additional data collection to aid academic researchers, public health agencies, and water and wastewater professionals involved in outbreak response.

Equine Coital Exanthema: New Insights on the Knowledge and Leading Perspectives for Treatment and Prevention

Equine coital exanthema (ECE) is a highly contagious, venereally-transmitted mucocutaneous disease, characterized by the formation of papules, vesicles, pustules and ulcers on the external genital organs of mares and stallions, and caused by equid alphaherpesvirus 3 (EHV-3). The infection is endemic worldwide and the virus is transmitted mainly through direct contact during sexual intercourse and by contaminated instruments during reproductive maneuvers in breeding facilities. The disease does not result in systemic illness, infertility or abortion, yet it does have a negative impact on the equine industry as it forces the temporary withdrawal of affected animals with the consequent disruption of mating activities in breeding facilities. The purpose of this review is to provide up-to-date relevant information on the knowledge of EHV-3 infection and to analyze new approaches on diagnostics, treatment and prevention in the interest of minimizing the negative consequences of ECE in light of the current situation of the equine industry.

Coronavirus: occurrence, surveillance, and persistence in wastewater

The coronavirus disease (COVID-19) outbreak reported in China in December 2019 has spread throughout the world. The WHO declared it as a pandemic in March 2020. The pandemic severely affected public health and the global economy. Many studies conducted on the coronavirus have helped us to elucidate its pathogenicity and pathophysiology. However, it is important to study the behavior of the pathogen in the environment to develop effective control measures. While studying the persistence and transmission of viruses in drinking water and wastewater systems, a low concentration of coronavirus and its nucleic acids have been detected in municipal wastewaters. This could be due to their high susceptibilities to degradation in aqueous environments. Epidemiological study on coronaviruses in wastewater will serve two purposes, i.e., in early detection of outbreak and in identifying asymptomatic carriers. In such cases, the epidemiological study will help in early detection of the presence of the virus in the community. Secondly, it will help in knowing if there are asymptomatic carriers, as such people do not show any signs of symptoms but shed the viruses in feces. The present review focuses on the epidemiological surveillance of wastewater for coronaviruses, as in recent years these are increasingly causing global pandemics. In this review we have discussed, the four pertinent areas of coronavirus study: (1) occurrence of coronavirus in wastewater, (2) wastewater based epidemiological surveillance of coronaviruses, (3) epidemiological surveillance tools used for detection of coronaviruses in sewage, and (4) persistence and sustainability of coronaviruses in wastewater.

Seasonal host and ecological drivers may promote restricted water as a viral vector

In climates with seasonally limited precipitation, terrestrial animals congregate at high densities at scarce water sources. We hypothesize that viruses can exploit the recurrence of these diverse animal congregations to spread. In this study, we test the central prediction of this hypothesis - that viruses employing this transmission strategy remain stable and infectious in water. Equid herpesviruses (EHVs) were chosen as a model as they have been shown to remain stable and infectious in water for weeks under laboratory conditions. Using fecal data from wild equids from a previous study, we establish that EHVs are shed more frequently by their hosts during the dry season, increasing the probability of water source contamination with EHV. We document the presence of several strains of EHVs present in high genome copy number from the surface water and sediments of waterholes sampled across a variety of mammalian assemblages, locations, temperatures and pH. Phylogenetic analysis reveals that the different EHV strains found exhibit little divergence despite representing ancient lineages. We employed molecular approaches to show that EHVs shed remain stable in waterholes with detection decreasing with increasing temperature in sediments. Infectivity experiments using cell culture reveals that EHVs remain infectious in water derived from waterholes. The results are supportive of water as an abiotic viral vector for EHV.

Environmental Detection and Potential Transmission of Equine Herpesviruses

Equine herpesviruses (EHV) are a major health concern for domestic and wild equids and represent one of the most economically important disease agents of horses. Most known EHVs are transmitted directly between individuals as a result of direct exposure to exudates and aerosols. However, accumulating evidence suggests that environmental transmission may play a role including air, water, and fomites. Here, we reviewed studies on environmental stability and transmission of EHVs, which may influence viral dynamics and the use of environmental samples for monitoring EHV shedding.

Natural Host-Environmental Media-Human: A New Potential Pathway of COVID-19 Outbreak

Identifying the first infected case (patient zero) is key in tracing the origin of a virus; however, doing so is extremely challenging. Patient zero for coronavirus disease 2019 (COVID-19) is likely to be permanently unknown. Here, we propose a new viral transmission route by focusing on the environmental media containing viruses of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or RaTG3-related bat-borne coronavirus (Bat-CoV), which we term the "environmental quasi-host." We reason that the environmental quasi-host is likely to be a key node in helping recognize the origin of SARS-CoV-2; thus, SARS-CoV-2 might be transmitted along the route of natural host-environmental media-human. Reflecting upon viral outbreaks in the history of humanity, we realize that many epidemic events are caused by direct contact between humans and environmental media containing infectious viruses. Indeed, contacts between humans and environmental quasi-hosts are greatly increasing as the space of human activity incrementally overlaps with animals' living spaces, due to the rapid development and population growth of human society. Moreover, viruses can survive for a long time in environmental media. Therefore, we propose a new potential mechanism to trace the origin of the COVID-19 outbreak.

Hidden treasure of the Gobi: understanding how water limits range use of khulan in the Mongolian Gobi

Most large herbivores in arid landscapes need to drink which constrains their movements and makes them vulnerable to disturbance. Asiatic wild ass or khulan (Equus hemionus) were widespread and abundant throughout the arid landscapes of Central Asia and Mongolia, but have undergone dramatic population declines and range constrictions; denying khulan access to water is believed to have played a major role. Mongolia's South Gobi Region now houses the world largest remaining khulan population, but is undergoing rapid land use changes. Khulan water use is poorly understood, largely due to the difficulty of mapping waterpoints used by khulan throughout their exceptionally large ranges, prone to high variations in precipitation. We used the special movement path characteristics of GPS tagged khulan to show us where water is located. We identified 367 waterpoints, 53 of which were of population importance, characterized the seasonal and circadian use, and identified snow cover as the most important variable predicting khulan visits during the non-growing season, and vegetation greenness during the growing season. Our results provide a data layer to help guide a regional khulan conservation strategy, allow predictions for other part of the global khulan range, and illustrates the overall importance of waterpoints for dryland herbivores.

Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe?

Neurological disorders represent an important sanitary and economic threat for the equine industry worldwide. Among nervous diseases, viral encephalitis is of growing concern, due to the emergence of arboviruses and to the high contagiosity of herpesvirus-infected horses. The nature, severity and duration of the clinical signs could be different depending on the etiological agent and its virulence. However, definite diagnosis generally requires the implementation of combinations of direct and/or indirect screening assays in specialized laboratories. The equine practitioner, involved in a mission of prevention and surveillance, plays an important role in the clinical diagnosis of viral encephalitis. The general management of the horse is essentially supportive, focused on controlling pain and inflammation within the central nervous system, preventing injuries and providing supportive care. Despite its high medical relevance and economic impact in the equine industry, vaccines are not always available and there is no specific antiviral therapy. In this review, the major virological, clinical and epidemiological features of the main neuropathogenic viruses inducing encephalitis in equids in Europe, including rabies virus (Rhabdoviridae), Equid herpesviruses (Herpesviridae), Borna disease virus (Bornaviridae) and West Nile virus (Flaviviridae), as well as exotic viruses, will be presented.

Molecular Surveillance of EHV-1 Strains Circulating in France during and after the Major 2009 Outbreak in Normandy Involving Respiratory Infection, Neurological Disorder, and Abortion

Equine herpesvirus 1 (EHV-1) is an Alphaherpesvirus infecting not only horses but also other equid and non-equid mammals. It can cause respiratory distress, stillbirth and neonatal death, abortion, and neurological disease. The different forms of disease induced by EHV-1 infection can have dramatic consequences on the equine industry, and thus the virus represents a great challenge for the equine and scientific community. This report describes the progress of a major EHV-1 outbreak that took place in Normandy in 2009, during which the three forms of disease were observed. A collection of EHV-1 strains isolated in France and Belgium from 2012 to 2018 were subsequently genetically analysed in order to characterise EHV-1 strain circulation. The open reading frame 30 (ORF30) non-neuropathogenic associated mutation A₂₂₅₄ was the most represented among 148 samples analysed in this study. ORF30 was also sequenced for 14 strains and compared to previously published sequences. Finally, a more global phylogenetic approach was performed based on a recently described Multilocus Sequence Typing (MLST) method. French and Belgian strains were clustered with known strains isolated in United Kingdom and Ireland, with no correlation between the phylogeny and the time of collection or location. This new MLST approach could be a tool to help understand epidemics in stud farms.

Shedding of the Salmonid Herpesvirus-3 by Infected Lake Trout (Salvelinus namaycush)

Salmonid Herpesvirus-3, commonly known as the Epizootic Epitheliotropic Disease virus (EEDV), causes a disease of lake trout (Salvelinus namaycush) that has killed millions of fish over the past several decades. Currently, most aspects of EEDV disease ecology remain unknown. In this study, we investigated EEDV shedding in experimentally challenged (intracoelomic injection) lake trout that were individually microchipped. In order to assess viral shedding, each infected fish was placed in individual static, aerated aquaria for a period of 8 h, after which the water was assessed for the presence of EEDV DNA using quantitative PCR. Water sampling was conducted every seven days for 93 days post-infection (pi), followed by additional sampling after one year. Results demonstrated that lake trout began shedding EEDV into the water as early as 9 days pi. Shedding peaked approximately three weeks pi and ceased after nine weeks pi. In contrast, mortalities did not occur until 40 days pi. Although mortality reached 73.9%, surviving fish ceased shedding and continued to grow. However, additional shedding was detected 58 weeks after infection in 66% of surviving fish. Findings of this study demonstrate that EEDV is shed into the water by infected lake trout hosts for extended periods of time, a mechanism that favors virus dissemination.

Detection of equid herpesviruses among different Arabian horse populations in Egypt

Equid herpesviruses (EHVs) threaten equine health and can cause significant economic losses to the equine industry worldwide. Different equid herpesviruses, EHV-1, EHV-2, EHV-4 and EHV5 are regularly detected among horse populations. In Egypt, monitoring is sporadic but EHV-1 or EHV-4 have been reported to circulate in the horse population. However, there is a lack of reports related to infection and health status of horses, likely due to the absence of regular diagnostic procedures. In the current study, the circulation of four infectious equid herpesviruses (EHV-1, EHV-2, EHV-4 and EHV-5) among different Arabian horse populations and donkeys residing the same farm was monitored. Different samples were collected and DNA was extracted and subjected to quantitative (q)-PCR to detect the four equid herpesviruses using specific primers and probes. Antibody titres against EHV-1 and EHV-4 were tested using virus neutralization test and type-specific ELISA. The results showed that EHV-1, EHV-2, EHV-4 and EHV-5 are endemic and can be a continuous threat for horses in the absence of vaccination programs and frequent virus reactivation. There is an urgent need for introduction of active regular surveillance measures to investigate the presence of different equid herpesviruses, and other equine viral pathogens, in various horse populations around Egypt and to establish a standardized cataloguing of equine health status.

Noninvasive Detection of Equid Herpesviruses in Fecal Samples

Equid herpesviruses (EHVs) are pathogens of equid and nonequid hosts that can cause disease and fatalities in captivity and in the wild. EHVs establish latent infections but can reactivate, and most EHVs are shed via the nasal passage. Therefore, nasal swabs are generally used for EHV monitoring. However, invasive sampling of wild equids is difficult. While feces is a commonly used substrate for detecting other pathogens, to our knowledge, EHVs have never been detected in feces of naturally infected equids. We systematically tested zebra feces for EHV presence by (i) establishing nested PCR conditions for fecal DNA extracts, (ii) controlling for environmental EHV contamination, and (iii) large-scale testing on a free-ranging zebra population. A dilution minimizing inhibition while maximizing viral DNA concentrations was determined in captive Grévy's zebra (Equus grevyi) fecal samples from individuals shedding EHV nasally. Sixteen of 42 fecal samples (38%) were EHV positive. To demonstrate that the EHV positivity was not a result of environmental contamination, rectal swabs of wild zebras were screened (n = 18 [Equus quagga and E. zebra]), and 50% were EHV positive, indicating that the source of EHV in feces is likely the intestinal mucosa and not postdefecation contamination. Out of 270 fecal samples of wild zebras, 26% were EHV positive. Quantitative PCRs showed that the amount of virus DNA in feces was not significantly smaller than that in other samples. In summary, fecal sampling facilitates large-scale screening and may be useful to noninvasively investigate phylogenetic EHV diversity in wild and domestic equids.IMPORTANCE Equid herpesviruses (EHVs) establish latent infections, and many EHVs are shed and transmitted via nasal discharge primarily through droplet and aerosol infection. Obtaining nasal swabs and other invasive samples from wildlife is often not possible without capture and physical restraint of individuals, which are resource intensive and a health risk for the captured animals. Fecal EHV shedding has never been demonstrated for naturally infected equids. We established the conditions for fecal EHV screening, and our results suggest that testing fecal samples is an effective noninvasive approach for monitoring acute EHV shedding in equids.

Molecular Characterisation of Equine Herpesvirus 1 Isolates from Cases of Abortion, Respiratory and Neurological Disease in Ireland between 1990 and 2017

Multiple locus typing based on sequencing heterologous regions in 26 open reading frames (ORFs) of equine herpesvirus 1 (EHV-1) strains Ab4 and V592 was used to characterise 272 EHV-1 isolates from 238 outbreaks of abortion, respiratory or neurological disease over a 28-year period. The analysis grouped the 272 viruses into at least 10 of the 13 unique long region (U_L) clades previously recognised. Viruses from the same outbreak had identical multi-locus profiles. Sequencing of the ORF68 region of EHV-1 isolates from 222 outbreaks established a divergence into seven groups and network analysis demonstrated that Irish genotypes were not geographically restricted but clustered with viruses from all over the world. Multi-locus analysis proved a more comprehensive method of strain typing than ORF68 sequencing. It was demonstrated that when interpreted in combination with epidemiological data, this type of analysis has a potential role in tracking virus between premises and therefore in the implementation of targeted control measures. Viruses from 31 of 238 outbreaks analysed had the proposed ORF30 G2254/D752 neuropathogenic marker. There was a statistically significant association between viruses of the G2254/D752 genotype and both neurological disease and hypervirulence as defined by outbreaks involving multiple abortion or neurological cases. The association of neurological disease in those with the G2254/D752 genotype was estimated as 27 times greater than in those with the A2254/N752 genotype.

How Host Specific Are Herpesviruses? Lessons from Herpesviruses Infecting Wild and Endangered Mammals

Herpesviruses are ubiquitous and can cause disease in all classes of vertebrates but also in animals of lower taxa, including molluscs. It is generally accepted that herpesviruses are primarily species specific, although a species can be infected by different herpesviruses. Species specificity is thought to result from host-virus coevolutionary processes over the long term. Even with this general concept in mind, investigators have recognized interspecies transmission of several members of the Herpesviridae family, often with fatal outcomes in non-definitive hosts-that is, animals that have no or only a limited role in virus transmission. We here summarize herpesvirus infections in wild mammals that in many cases are endangered, in both natural and captive settings. Some infections result from herpesviruses that are endemic in the species that is primarily affected, and some result from herpesviruses that cause fatal disease after infection of non-definitive hosts. We discuss the challenges of such infections in several endangered species in the absence of efficient immunization or therapeutic options.

Equid herpesvirus 8: Complete genome sequence and association with abortion in mares

Equid herpesvirus 8 (EHV-8), formerly known as asinine herpesvirus 3, is an alphaherpesvirus that is closely related to equid herpesviruses 1 and 9 (EHV-1 and EHV-9). The pathogenesis of EHV-8 is relatively little studied and to date has only been associated with respiratory disease in donkeys in Australia and horses in China. A single EHV-8 genome sequence has been generated for strain Wh in China, but is apparently incomplete and contains frameshifts in two genes. In this study, the complete genome sequences of four EHV-8 strains isolated in Ireland between 2003 and 2015 were determined by Illumina sequencing. Two of these strains were isolated from cases of abortion in horses, and were misdiagnosed initially as EHV-1, and two were isolated from donkeys, one with neurological disease. The four genome sequences are very similar to each other, exhibiting greater than 98.4% nucleotide identity, and their phylogenetic clustering together demonstrated that genomic diversity is not dependent on the host. Comparative genomic analysis revealed 24 of the 76 predicted protein sequences are completely conserved among the Irish EHV-8 strains. Evolutionary comparisons indicate that EHV-8 is phylogenetically closer to EHV-9 than it is to EHV-1. In summary, the first complete genome sequences of EHV-8 isolates from two host species over a twelve year period are reported. The current study suggests that EHV-8 can cause abortion in horses. The potential threat of EHV-8 to the horse industry and the possibility that donkeys may act as reservoirs of infection warrant further investigation.

Access to a main alphaherpesvirus receptor, located basolaterally in the respiratory epithelium, is masked by intercellular junctions

The respiratory epithelium of humans and animals is frequently exposed to alphaherpesviruses, originating from either external exposure or reactivation from latency. To date, the polarity of alphaherpesvirus infection in the respiratory epithelium and the role of respiratory epithelial integrity herein has not been studied. Equine herpesvirus type 1 (EHV1), a well-known member of the alphaherpesvirus family, was used to infect equine respiratory mucosal explants and primary equine respiratory epithelial cells (EREC), grown at the air-liquid interface. EHV1 binding to and infection of mucosal explants was greatly enhanced upon destruction of the respiratory epithelium integrity with EGTA or N-acetylcysteine. EHV1 preferentially bound to and entered EREC at basolateral cell surfaces. Restriction of infection via apical inoculation was overcome by disruption of intercellular junctions. Finally, basolateral but not apical EHV1 infection of EREC was dependent on cellular N-linked glycans. Overall, our findings demonstrate that integrity of the respiratory epithelium is crucial in the host’s innate defence against primary alphaherpesvirus infections. In addition, by targeting a basolaterally located receptor in the respiratory epithelium, alphaherpesviruses have generated a strategy to efficiently escape from host defence mechanisms during reactivation from latency.