No Evidence of Hendra Virus Infection in the Australian Flying‐fox Ectoparasite Genus Cyclopodia

Hendra virus (HeV) causes potentially fatal respiratory and/or neurological disease in both horses and humans. Although Australian flying‐foxes of the genus Pteropus have been identified as reservoir hosts, the precise mechanism of HeV transmission has yet to be elucidated. To date, there has been limited investigation into the role of haematophagous insects as vectors of HeV. This mode of transmission is particularly relevant because Australian flying‐foxes host the bat‐specific blood‐feeding ectoparasites of the genus Cyclopodia (Diptera: Nycteribiidae), also known as bat flies. Using molecular detection methods, we screened for HeV RNA in 183 bat flies collected from flying‐foxes inhabiting a roost in Boonah, Queensland, Australia. It was subsequently demonstrated that during the study period, Pteropus alecto in this roost had a HeV RNA prevalence between 2 and 15% (95% CI [1, 6] to [8, 26], respectively). We found no evidence of HeV in any bat flies tested, including 10 bat flies collected from P. alecto in which we detected HeV RNA. Our negative findings are consistent with previous findings and provide additional evidence that bat flies do not play a primary role in HeV transmission.     

Kunjin flaviviral encephalomyelitis in an Arabian gelding in New South Wales, Australia

Flaviviruses, including Kunjin virus, are arboviruses that cause encephalomyelitis in humans and horses. This case report describes an Arabian gelding exhibiting neurological signs of flavivirus encephalomyelitis, the diagnostic investigation and confirmation of an unreported case of Kunjin virus equine encephalomyelitis in Australia.     

Transmission studies of Hendra virus (equine morbilli-virus) in fruit bats, horses and cats

Objective To determine the infectivity and transmissibility of Hendra virus (HeV). Design A disease transmission study using fruit bats, horses and cats. Procedure Eight grey-headed fruit bats (Pteropus poliocephalus) were inoculated and housed in contact with three uninfected bats and two uninfected horses. In a second exper iment, four horses were inoculated by subcutaneous injection and intranasal inoculation and housed in contact with three uninfected horses and six uninfected cats. In a third experi ment, 12 cats were inoculated and housed in contact with three uninfected horses. Two surviving horses were inoculated at the conclusion of the third experiment: the first orally and the second by nasal swabbing. All animals were necropsied and examined by gross and microscopic pathological methods, immunoperoxidase to detect viral antigen in formalin-fixed tissues, virus isolation was attempted on tissues and SNT and ELISA methods were used to detect HeV-specific antibody. Results Clinical disease was not observed in the fruit bats, although six of eight inoculated bats developed antibody against HeV, and two of six developed vascular lesions which contained viral antigen. The in-contact bats and horses did not seroconvert. Three of four horses that were inoculated devel oped acute disease, but in-contact horses and cats were not infected. In the third experiment, one of three in-contact horses contracted disease. At the time of necropsy, high titres of HeV were detected in the kidneys of six acutely infected horses, in the urine of four horses and the mouth of two, but not in the nasal cavities or tracheas. Conclusions Grey-headed fruit bats seroconvert and develop subclinical disease when inoculated with HeV. Horses can be infected by oronasal routes and can excrete HeV in urine and saliva. It is possible to transmit HeV from cats to horses. Transmission from P poliocephalus t o horses could not be proven and neither could transmission from horses to horses or horses to cats. Under the experimental conditions of the study the virus is not highly contagious.     

Hendra Virus Infection in Horses: A Review on Emerging Mystery Paramyxovirus

Hendra virus (HeV) is a zoonotic paramyxovirus which causes acute and deadly infection in horses (Equus caballus). It is a rare and unmanaged emerging viral infection in horses which is harbored by bats of the genus Pteropus (Australian flying foxes or fruit bats). The virus is pleomorphic in shape and its genome contains nonsegmented negative-stranded RNA with 18234 nucleotides in length. The virus is transmitted from flying foxes to horses, horse to horse, and horse to humans. Human-to-human transmission of HeV infection is not reported yet. The infection of HeV in horses is highly variable and shows broad range of signs and lesions including distinct respiratory and neurological disorders. Currently, there are no specific antiviral drugs available for the treatment of HeV infection in horses. Vaccination is considered as prime option to prevent HeV infection in horses. A subunit vaccine, called as “Equivac HeV vaccine” has been approved recently for preventing this viral infection in horses. In addition, a plethora of common preventive strategies could help restrict the inter- and intra-species transmission of HeV. Considering the scanty but severe fatality cases of this mystery virus as well as lack of proper attention by veterinary scientists, this review article spotlights not only on the clinical signs, transmission, epidemiology, biology, pathogenesis, and diagnosis of HeV but also the preventive managements of this uncommon infection in horses by vaccination and other precautious strategies.     

Infection with Menangle virus in flying foxes (Pteropus spp.) in Australia

Objective To examine flying foxes (Pteropus spp.) for evidence of infection with Menangle virus. Design Clustered non‐random sampling for serology, virus isolation and electron microscopy (EM). Procedure Serum samples were collected from 306 Pteropus spp. in northern and eastern Australia and tested for antibodies against Menangle virus (MenV) using a virus neutralisation test (VNT). Virus isolation was attempted from tissues and faeces collected from 215 Pteropus spp. in New South Wales. Faecal samples from 68 individual Pteropus spp. and four pools of faeces were examined by transmission EM following routine negative staining and immunogold labelling. Results Neutralising antibodies (VNT titres ≥ 8) against MenV were detected in 46% of black flying foxes (P. alecto), 41% of grey‐headed flying foxes (P. poliocephalus), 25% of spectacled flying foxes (P. conspicillatus) and 1% of little red flying foxes (P. scapulatus) in Australia. Positive sera included samples collected from P. poliocephalus in a colony adjacent to a piggery that had experienced reproductive disease caused by MenV. Virus‐like particles were observed by EM in faeces from Pteropus spp. and reactivity was detected in pooled faeces and urine by immunogold EM using sera from sows that had been exposed to MenV. Attempts to isolate the virus from the faeces and tissues from Pteropus spp. were unsuccessful. Conclusion Serological evidence of infection with MenV was detected in Pteropus spp. in Australia. Although virus‐like particles were detected in faeces, no viruses were isolated from faeces, urine or tissues of Pteropus spp.     

Disease suspected to be caused by Ross River virus infection of horses

Ross River Virus (RRV) was believed to be the cause of acute illness in four horses around the Bellarine peninsula in south-west Victoria, Australia. The horses presented with clinical signs including petechial haemorrhages, lymphadenopathy, distal limb swelling and reluctance to move. Fibrinogen was also elevated in three of the four horses. Whilst no virus was isolated, serological testing revealed elevated RRV IgM titres in all horses indicating acute infection. The outbreak occurred at a time when a known RRV vector, the mosquito Aedes camptorhynchus was recorded at very high levels in the region. This report is one of very few to attribute specific signs of disease to RRV in horses in conjunction with serological evidence of infection. Aust Vet J 2008;86:367-370.     

Hendra virus in Queensland,Australia, during the winter of 2011: Veterinarians on the path to better management strategies

Following the emergence of Hendra virus (HeV), private veterinarians have had to adopt additional infection control strategies to manage this zoonosis. Between 1994 and 2010, seven people became infected with HeV, four fatally. All infected people were at a higher risk of exposure from contact with horses as they were either veterinary personnel, assisting veterinarians, or working in the horse industry. The management of emerging zoonoses is best approached from a One Health perspective as it benefits biosecurity as well as a public health, including the health of those most at risk, in this case private veterinarians. In 2011 we conducted a cross-sectional study of private veterinarians registered in Queensland and providing veterinary services to horses. The aim of this study was to gauge if participants had adopted recommendations for improved infection control, including the use of personal protective equipment (PPE), and the development of HeV specific management strategies during the winter of 2011. A majority of participants worked in practices that had a formal HeV management plan, mostly based on the perusal of official guidelines and an HeV field kit. The use of PPE increased as the health status of an equine patient decreased, demonstrating that many participants evaluated the risk of exposure to HeV appropriately; while others remained at risk of HeV infection by not using the appropriate PPE even when attending a sick horse. This study took place after Biosecurity Queensland had sent a comprehensive package about HeV management to all private veterinarians working in Queensland. However, those who had previous HeV experience through the management of suspected cases or had attended a HeV specific professional education programme in the previous 12 months were more likely to use PPE than those who had not. This may indicate that for private veterinarians in Queensland personal experience and face-to-face professional education sessions may be more effective in the improvement of HeV management than passive education via information packages. The role of different education pathways in the sustainable adoption of veterinary infection control measures should be further investigated.     

Serological examination for evidence of infection with Hendra and Nipah viruses in Queensland piggeries

OBJECTIVE: To examine piggeries in Queensland for evidence of infection with Hendra virus and Nipah virus. DESIGN: A serological survey was designed to provide 99% confidence of detecting at least one infected pig herd in Queensland, assuming that for each virus, at least 5% of herds would have been exposed to virus and that at least 40% of the finisher pigs in these herds would have detectable antibodies to virus. PROCEDURE: A two stage sampling regimen was used. All samples were tested with serum neutralisation tests developed and performed at the Australian Animal Health Laboratory. RESULTS: There was no evidence of antibody to either virus in the 500 samples collected from 100 herds. CONCLUSION: The results of the survey support a case that commercial pigs in Queensland are free of both Hendra virus and Nipah virus infections.     

Investigation of the effect of Equivac® HeV Hendra virus vaccination on Thoroughbred racing performance

Objective

To evaluate the effect of Equivac® HeV Hendra virus vaccine on Thoroughbred racing performance.

Design

Retrospective pre‐post intervention study.

Methods

Thoroughbreds with at least one start at one of six major south‐eastern Queensland race tracks between 1 July 2012 and 31 December 2016 and with starts in the 3‐month periods before and after Hendra virus vaccinations were identified. Piecewise linear mixed models compared the trends in ‘Timeform rating’ and ‘margin to winner’ before and after initial Hendra virus vaccination. Generalised linear mixed models similarly compared the odds of ‘winning’, ‘placing’ (1st–3rd) and ‘winning any prize money’. Timeform rating trends were also compared before and after the second and subsequent vaccinations.

Results

Analysis of data from 4208 race starts by 755 horses revealed no significant difference in performance in the 3 months before versus 3 months after initial Hendra vaccination for Timeform rating (P = 0.32), ‘Margin to winner’ (P = 0.45), prize money won (P = 0.25), wins (P = 0.64) or placings (P = 0.77). Further analysis for Timeform rating for 7844 race starts by 928 horses failed to identify any significant change in Timeform rating trends before versus after the second and subsequent vaccinations (P = 0.16) or any evidence of a cumulative effect for the number of vaccines received (P = 0.22).

Conclusion

No evidence of an effect of Hendra virus vaccination on racing performance was found. The findings allow owners, trainers, industry regulators and animal health authorities to make informed decisions about vaccination.     

Animal models of henipavirus infection: A review

Hendra virus (HeV) and Nipah virus (NiV) form a separate genus Henipavirus within the family Paramyxoviridae, and are classified as biosafety level four pathogens due to their high case fatality rate following human infection and because of the lack of effective vaccines or therapy. Both viruses emerged from their natural reservoir during the last decade of the 20th century, causing severe disease in humans, horses and swine, and infecting a number of other mammalian species. The current review summarises current published data relating to experimental infection of small and large animals, including the natural reservoir species, the Pteropus bat, with HeV or NiV. Susceptibility to infection and virus distribution in the individual species is discussed, along with the pathogenesis, pathological changes, and potential routes of transmission.