An outbreak of psittacosis at a veterinary school demonstrating a novel source of infection.

In November 2014, New South Wales Health was notified of a cluster of respiratory illness in a veterinary school. Active case finding identified another case at a local equine stud. All cases had exposure to the equine fetal membranes of Mare A. This tissue subsequently tested positive for Chlamydia psittaci using quantitative real-time polymerase chain reaction. We conducted a cohort study of the university and stud farm staff to determine risk factors for disease. Nine people were exposed to the fetal membranes of Mare A. Of these, five cases of psittacosis were identified. Two required hospital admission. Contact with birds was not associated with illness (RR = 0.5, 95% CI = 0.09-2.73). People who had direct contact with the abnormal fetal membranes were more likely to develop disease (RR = 11.77, 95% CI = 1.02-∞). The emergence of an association between horse exposure and C. psittaci infection has important implications for the prevention and control of psittacosis. Article summary line: Investigation of an outbreak of psittacosis in a rural veterinary school demonstrates novel source of infection for psittacosis through exposure to abnormal equine fetal membranes.

Hendra Virus Infection in Dog, Australia, 2013.

Hendra virus occasionally causes severe disease in horses and humans. In Australia in 2013, infection was detected in a dog that had been in contact with an infected horse. Abnormalities and viral RNA were found in the dog's kidney, brain, lymph nodes, spleen, and liver. Dogs should be kept away from infected horses.

Longitudinal study of winter mortality disease in Sydney rock oysters Saccostrea glomerata.

Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomerata in estuaries in New South Wales, Australia, where it can cause significant losses. WM is more severe in oysters cultured deeper in the water column and appears linked to higher salinities. Current dogma is that WM is caused by the microcell parasite Bonamia roughleyi, but evidence linking clinical signs and histopathology to molecular data identifying bonamiasis is lacking. We conducted a longitudinal study between February and November 2010 in 2 estuaries where WM has occurred (Georges and Shoalhaven Rivers). Results from molecular testing of experimental oysters for Bonamia spp. were compared to clinical disease signs and histopathology. Available environmental data from the study sites were also collated and compared. Oyster condition declined over the study period, coinciding with decreasing water temperatures, and was inversely correlated with the presence of histological lesions. While mortalities occurred in both estuaries, only oysters from the Georges River study site showed gross clinical signs and histological changes characteristic of WM (lesions were prevalent and intralesional microcell-like structures were sometimes noted). PCR testing for Bonamia spp. revealed the presence of an organism belonging to the B. exitiosa-B. roughleyi clade in some samples; however, the very low prevalence of this organism relative to histological changes and the lack of reactivity of affected oysters in subsequent in situ hybridisation experiments led us to conclude that this Bonamia sp. is not responsible for WM. Another aetiological agent and a confluence of environmental factors are a more likely explanation for the disease.

Identification and characterisation of an ostreid herpesvirus-1 microvariant (OsHV-1 µ-var) in Crassostrea gigas (Pacific oysters) in Australia.

Between November 2010 and January 2011, triploid Crassostrea gigas (Pacific oysters) cultivated in the Georges River, New South Wales, experienced >95% mortality. Mortalities also occurred in wild diploid C. gigas in the Georges River and shortly thereafter in the adjacent Parramatta River estuary upstream from Sydney Harbour. Neighbouring Saccostrea glomerata (Sydney rock oysters) did not experience mortalities in either estuary. Surviving oysters were collected to investigate the cause of mortalities. Histologically all oysters displayed significant pathology, and molecular testing revealed a high prevalence of ostreid herpesvirus-1 (OsHV-1). Quantitative PCR indicated that many C. gigas were carrying a high viral load at the time of sampling, while the load in S. glomerata was significantly lower (p < 0.001). Subsequent in situ hybridisation experiments confirmed the presence of a herpesvirus in C. gigas but not S. glomerata tissues, suggesting that S. glomerata is not susceptible to infection with OsHV-1. Naïve sentinel triploid C. gigas placed in the Georges River estuary in January 2011 quickly became infected and experienced nearly 100% mortality within 2 wk of exposure, indicating the persistence of the virus in the environment. Phylogenetic analysis of sequences derived from the C2/C6 region of the virus revealed that the Australian strain of OsHV-1 belongs to the microvariant (µ-var) cluster, which has been associated with severe mortalities in C. gigas in other countries since 2008. Environmental data revealed that the Woolooware Bay outbreaks occurred during a time of considerable environmental disturbance, with increased water temperatures, heavy rainfall, a toxic phytoplankton bloom and the presence of a pathogenic Vibrio sp. all potentially contributing to oyster stress. This is the first confirmed report of OsHV-1 µ-var related C. gigas mortalities in Australia.

An experimental study of Bungowannah virus infection in weaner aged pigs.

Bungowannah virus is a pestivirus identified from an outbreak of stillbirth and increased mortality in the first 3-4 weeks of life on a piggery in New South Wales, Australia in June 2003. The aims of this study were to determine if post-natal infection results in any clinical abnormalities and quantify the amount of Bungowannah virus RNA in blood, oropharyngeal, nasal and conjunctival excretions and faeces during the course of infection. Thirty pigs were infected intra-nasally with one of six different doses of Bungowannah virus or a control inoculum and clinical signs and rectal temperatures monitored. Sera, leukocytes and oropharyngeal, nasal, conjunctival, rectal and tissue swabs were tested for Bungowannah virus by qRT-PCR and sera for antibody by peroxidase linked assay and virus neutralisation test. The infectious dose by the intra-nasal route in weaner pigs was determined to be between 1.6 and 3.2 log(10) TCID(50). Few clinical signs could be attributed to infection. Viraemia and viral excretion in oropharyngeal secretions were detected from 3 days post-inoculation and seroconversion from 10 days post-inoculation. Viral shedding was greatest and most frequently detected in oropharyngeal, and to a lesser extent, nasal secretions, and generally detected in lower amounts and less frequently in conjunctival secretions and faeces.

Emergence of epizootic ulcerative syndrome in native fish of the Murray-Darling River System, Australia: hosts, distribution and possible vectors.

Epizootic ulcerative syndrome (EUS) is a fish disease of international significance and reportable to the Office International des Epizootics. In June 2010, bony herring Nematalosa erebi, golden perch Macquaria ambigua, Murray cod Maccullochella peelii and spangled perch Leiopotherapon unicolor with severe ulcers were sampled from the Murray-Darling River System (MDRS) between Bourke and Brewarrina, New South Wales Australia. Histopathology and polymerase chain reaction identified the fungus-like oomycete Aphanomyces invadans, the causative agent of EUS. Apart from one previous record in N. erebi, EUS has been recorded in the wild only from coastal drainages in Australia. This study is the first published account of A. invadans in the wild fish populations of the MDRS, and is the first confirmed record of EUS in M. ambigua, M. peelii and L. unicolor. Ulcerated carp Cyprinus carpio collected at the time of the same epizootic were not found to be infected by EUS, supporting previous accounts of resistance against the disease by this species. The lack of previous clinical evidence, the large number of new hosts (n = 3), the geographic extent (200 km) of this epizootic, the severity of ulceration and apparent high pathogenicity suggest a relatively recent invasion by A. invadans. The epizootic and associated environmental factors are documented and discussed within the context of possible vectors for its entry into the MDRS and recommendations regarding continued surveillance, research and biosecurity are made.

Cryptosporidiosis in intensively reared Barramundi (Lates calcarifer).

Two outbreaks of mortality in juvenile barramundi (Lates calcarifer) with a high prevalence of gastrointestinal cryptosporidiosis are described. Juvenile barramundi at a separate hatchery and grow-out facility were demonstrating markedly increased mortality rates. Histological examination in all cases indicated a heavy infection of Cryptosporidium-like organisms within the distal stomach and proximal small intestine. Electron microscopy confirmed a diagnosis of cryptosporidiosis; however, speciation was not possible.

Tonsillitis in a weaner pig associated with Geotrichum candidum.

Geotrichum candidum was cultured from the tonsils of a free-ranging weaner pig that was presented with lethargy and inappetence. Histopathology indicated pyogranulomatous tonsillitis with intralesional fungal hyphae and arthrospores. Geotrichosis is a rare, opportunistic mycosis of immunocompromised hosts, usually human beings.

Chronic myositis in an Australian alpaca (Llama pacos) associated with Sarcocystis spp.

An alpaca (Llama pacos), born and raised in Australia, was presented with multiple subcutaneous abscesses. Histological findings indicated a severe necrotizing and histiocytic myositis and cellulitis associated with central caseation and multiple sarcocysts. Ultrastructural examination supported the diagnosis; however, cyst wall characteristics were not consistent with the 2 known species found in alpacas. While seroconversion in camelids is reported to be near ubiquitous, myositis is rare, and this is the first case reported outside of the Americas.