Emergency Animal Disease Alerts, Vol. 10 Issue 2

​May 2016

Rift Valley fever (RVF)

In March 2016, the first cases of Rift Valley fever (RVF) were confirmed in humans and small ruminants in Uganda’s south-western province of Kabale. RVF is a zoonotic disease of domestic ruminants caused by a vector-borne RNA virus of the family Bunyavirus, and is listed as a notifiable disease by the World Organisation for Animal Health (OIE). RVF causes severe disease in ruminants, with high mortality rates in young animals and abortions in adults. Human disease generally follows animal outbreaks through exposure to infected animal tissues, and via transmission from arthropod vectors.

RVF typically occurs in sub-Saharan Africa, but outbreaks in neighbouring regions such as Egypt, Saudi Arabia and Yemen have occurred. Movement of infected vectors, livestock and people are considered primary drivers of RVF emergence. The expanding distribution of vectors raises concerns over future disease spread.

There are currently no licensed vaccines against RVF virus for use in humans, and those used in livestock have been known to result in post-challenge viraemia, abortion and variable immunogenicity. A recent paper published in Scientific Reports describes a ‘One Health’ approach to the development and trial of a single vaccine against RVF virus for use in both livestock and humans. To date, results from vaccine trials with sheep, goats and cattle appear promising.

Would you be able to recognise the signs of Rift Valley Fever?

Variegated Squirrel 1 Bornavirus (VSBV-1)

A novel bornavirus detected in variegated squirrels was associated with three human cases of fatal encephalitis in Germany between 2011 and 2013. Further investigations by German authorities in January 2016 isolated Variegated Squirrel 1 Bornavirus (VSBV-1) from squirrels in zoos and breeding facilities in Germany. While the host range of VSBV-1 is incompletely understood, the virus is genetically similar to Borna disease virus, a nationally notifiable disease in Australia that is known to cause polioencephalomyelitis in a number of domestic species (primarily horses and sheep), and has been linked to neuropsychiatric disorders in humans.

Global AI Update

Since our last issue, Nigeria has experienced further outbreaks of H5N1 highly pathogenic avian influenza (HPAI). Along with recent outbreaks in Ghana and Cote d'Ivoire, these reports indicate a resurgence in H5N1 activity in Africa. As with previous outbreaks in Nigeria, poor farm biosecurity was cited as a contributing factor.

In Europe, both low pathogenic avian influenza (LPAI) and HPAI activity has continued. In France, outbreaks of H5N3 LPAI were reported in geese, H5N2 HPAI in guinea fowl and H5N1 HPAI in ducks. An increasing trend in H7N7 activity in Europe has continued, with outbreaks of H7N7 HPAI and LPAI in Italy.

In Asia, Vietnam was one of four countries to report outbreaks of H5N6 HPAI, in addition to China, Lao PDR and Hong Kong. China remains the only country to have reported human illness from the strain, with 12 human cases in total (9 of which have been reported since December 2015). Taiwan and the Republic of Korea continue to manage multiple outbreaks of H5N8 HPAI in poultry. A publication in Emerging Infectious Diseasessupports the hypothesis that asymptomatic migratory birds play a role in the geographic dissemination and reassortment of H5N8.

Seneca Valley virus (SVV)

Seneca Valley virus (SVV) is a non-enveloped picornavirus discovered incidentally in 2002 as a cell culture contaminant. The virus was recently recognised as the causative agent of porcine idiopathic vesicular disease outbreaks in the US and Brazil.

Studies with SVV have reproduced clinical vesicular disease in experimentally infected grower pigs, and associated lesions are clinically indistinguishable from those caused by other exotic vesicular diseases of pigs, such as foot-and-mouth disease, swine vesicular disease and vesicular stomatitis. Lameness is commonly observed and gross lesions include vesicles and ulcerative lesions on distal limbs, especially around the coronary bands; crusting and sloughing of the hoof; and vesicles and ulcers of the oral mucosa, snout and nares.

If you suspect vesicular disease in pigs, contact your local government vet or the Emergency Animal Disease Watch Hotline on 1800 675 888.

Varroa-vectored deformed wing virus (DWV)

The world’s honeybee populations are facing threats from changing land use, pesticides, climate change, introduced pests and diseases. The mite Varroa destructoris well-recognised as both an ectoparasite of honeybees, and as a vector for deformed wing virus (DWV). A phylogeographic analysis published in Science recognises a recent global epidemic of DWV in honeybees, driven by ecological change, the spread of Varroa as a vector, and increased global movement of infected bees and contaminated material such as pollen.

Australia is one of the few countries to remain free of Varroa. The Australian honey and bee products industry has an annual value of $90 million, with additional contributions to agricultural production through pollination services estimated at a minimum of $620 million per year. In order to protect Australia’s bee industry, the National Bee Pest Surveillance Program conducts surveillance activities at likely entry points for bee pests and diseases, and provides an early warning system to detect new incursions. More information on the range of activities undertaken to prevent introduction of bee pests and diseases can be found on the Department of Agriculture and Water Resources website.

Chronic Wasting Disease (CWD)

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy (TSE) of cervids, endemic to parts of North America. Like other TSEs such as scrapie and bovine spongiform encephalopathy, CWD is a progressive neurodegenerative prion disease.

Until recently only four species of cervids were known to be naturally susceptible to CWD: mule deer, white-tailed deer, Shiras moose and Rocky Mountain elk. While transmission risks to humans and domestic ruminants is incompletely understood, no human cases of prion disease have been associated with CWD and cattle appear to have natural resistance to infection.

In recent years the distribution of CWD has expanded within North America, and in March 2016 the Norwegian Veterinary Institute diagnosed CWD in a free-ranging reindeer in southern Norway. This report marks the first detection of CWD in Europe, as well as the first detection of natural infection in reindeer worldwide.

Trypanosoma evansi

Trypanosoma evansi is the causative agent of the haemoparasitic disease known as surra. T. evansi has a wide host spectrum, with acute disease most common in equids, camelids, domestic dogs and cats. Clinical signs of acute disease include an irregular pyrexia related to peaks in parasitaemia, progressive weight loss despite food intake, dependent oedema, anaemia, urticarial plaques and general ill-thrift. A report from Vietnam confirms the first human case of T. evansi infection in South-East Asia, through suspected exposure to infected raw meat. A subsequent epidemiological investigation identified a significant burden of T. evansi in local cattle, highlighting the importance of surveillance for animal trypanosomes in endemic areas. Atypical human infection with animal trypanosomes remain an emerging and potentially neglected disease of public health concern.

Recent publications

International Research Consortium for Animal Health

A new International Research Consortium for Animal Health (IRC) has been launched by the Global Strategic Alliances for the Coordination of Research on the Major Infectious Diseases of Animals and Zoonoses (STAR-IDAZ) to coordinate global research and develop new methods for controlling animal diseases. The IRC will advance strategies for over 30 priority diseases and animal health challenges, including antimicrobial resistance and vaccine development.

Japanese Encephalitis virus (JEV)

An in vivo study published in Nature Communicationsreports the first observed vector-free transmission of Japanese Encephalitis virus (JEV) via direct contact between pigs.

Guinea worm disease (GWD)

A report from the Carter Center has identified domestic free-roaming dogs as a key challenge for global eradication of Guinea worm disease (GWD) in the four remaining endemic countries of Chad, Ethiopia, Mali, and South Sudan. Enhanced health education to prevent infection of dogs and subsequent contamination of water sources is ongoing.

Remember

You may be looking at the first case and you do not want to become famous as the vet who missed it!

Use the hotline number 1800 675 888 or contact your local government vet.  You are not alone.