Henipavirus-induced neuropathogenesis in mice.

Hendra virus (HeV) and Nipah virus (NiV) are henipaviruses that can cause fatal encephalitis in humans. Many animal models have been used to study henipavirus pathogenesis. In the mouse, HeV infection has previously shown that intranasal challenge can lead to neurological infection, however mice similarly challenged with NiV show no evidence of virus infecting the brain. We generated recombinant HeV (rHeV) and NiV (rNiV) where selected proteins were switched to examine their role in neuroinvasion in the mouse. These viruses displayed similar growth kinetics when compared to wildtype in vitro. In the mouse, infection outcomes with recombinant virus did not differ to infection outcomes of wildtype viruses. Virus was detected in the brain of 5/30 rHeV-challenged mice, but not rNiV-challenged mice. To confirm the permissiveness of mouse neurons to these viruses, primary mouse neurons were successfully infected in vitro, suggesting that other pathobiological factors contribute to the differences in disease outcomes in mice.

Comparative genomic analysis of the first Ehrlichia canis detections in Australia.

Ehrlichia canis (Rickettsiales; Anaplasmataceae) is one of the most prevalent tick-borne pathogens of dogs globally. The bacterium infects monocytes and is the aetiological agent of canine monocytic ehrlichiosis. For many decades Australia was thought to be free of the pathogen, but this abruptly changed in May 2020 when E. canis was detected in several dogs from Kununurra, Western Australia. Subsequent surveillance activities found unexpectedly large scale spread of E. canis throughout much of northern Australia. To gain insight into the genetic relationships of the Australian strain and its potential origin, we undertook a genomic analysis of E. canis positive domestic dog and tick (Rhipicephalus linnaei) samples from the north of Western Australia, the far north of South Australia and the Northern Territory, covering thousands of square kilometres. We obtained complete E. canis genomes from each of the three states, plus an additional 16 partial genomes, substantially increasing publicly available E. canis genetic resources. The Australian E. canis genomes were highly conserved across large geographic distances. Outside of Australia, the genomes were most similar to E. canis YZ-1 from China, although few reference sequences were available. We analysed the variable trp36 gene to obtain greater phylogenetic signal, which demonstrated that the Australian E. canis belonged to the Taiwan genotype, comprised of samples from Taiwan, China, Thailand and Turkey. Taken together, our findings suggest that E. canis in Australia may have originated from Asia or the Middle East and spread throughout northern and central Australia following its introduction.

Animals and SARS-CoV-2: Species susceptibility and viral transmission in experimental and natural conditions, and the potential implications for community transmission.

The current COVID-19 global pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) of probable bat origin, has highlighted the ongoing need for a One Health response to emerging zoonotic disease events. Understanding the human-animal interface and its relevance to disease transmission remains a critical control point for many emerging zoonoses. Determination of the susceptibility of various animal species to infection with SARS-CoV-2 and the role of animals in the epidemiology of the disease will be critical to informing appropriate human and veterinary public health responses to this pandemic. A scoping literature review was conducted to collect, evaluate and present the available research evidence regarding SARS-CoV-2 infections in animals. Experimental studies have successfully demonstrated SARS-CoV-2 infection and transmission in cats, ferrets, hamsters, bats and non-human primates under experimental settings. Dogs appear to have limited susceptibility to SARS-CoV-2, while other domestic species including pigs and poultry do not appear susceptible. Naturally occurring SARS-CoV-2 infections in animals appear uncommon, with 14 pets, 8 captive big cats and an unreported number of farmed mink testing positive at the time of writing (early July 2020). Infections typically appear asymptomatic in dogs, while clinical signs of respiratory and/or gastrointestinal disease tend to be mild to moderate in felines, and severe to fatal in mink. Most animals are presumed to have been infected by close contact with COVID-19 patients. In domestic settings, viral transmission is self-limiting; however in high-density animal environments, there can be sustained between-animal transmission. To date, two potential cases of animal-to-human transmission are being investigated, on infected mink farms. Given the millions of COVID-19 cases worldwide and ongoing potential for further zoonotic and anthroponotic viral transmission, further research and surveillance activities are needed to definitively determine the role of animals in community transmission of SARS-CoV-2.