Dr Mark Schipp on Japanese encephalitis and lumpy skin disease

Two significant animal diseases have come to prominence recently, with an outbreak of Japanese encephalitis affecting several states in Australia, and Lumpy skin disease being detected in Indonesia to our north – a disease which is a risk to Australia’s cattle industry.

As veterinarians we must all be vigilant against notifiable diseases such as Japanese encephalitis and Lumpy skin disease. We frequently interact with livestock producers, hobby farmers and animal-owners in the community. It is vital that each of us are aware of the presenting clinical signs of these and other notifiable diseases, and know how to respond if suspicious clinical signs are noticed or are reported by a livestock producer or animal-owner.

Japanese encephalitis outbreaks

Japanese encephalitis (JE) has recently been detected in southern Australia for the first time, with outbreaks reported in piggeries in Queensland, New South Wales, Victoria and South Australia. JE is a zoonotic disease and although severe disease is rare, there have already been several human deaths reported attributable to JE.

Regular updates about the JE outbreak are being provided on the Department of Agriculture, Water and the Environment’s Outbreak website and Australia’s JE response strategy is outlined in the AUSVETPLAN.

JE is an acute, mosquito-borne viral disease that can cause reproductive losses and encephalitis in susceptible species, with clinical signs of disease most common in pigs and horses, and rarely people.

Waterbirds act as natural reservoirs for the virus, and mosquitos can spread the virus to horses, pigs and other animals. Waterbirds and pigs are important amplifying hosts for JE, whereas people and horses are considered ‘dead end’ hosts. Other animals can be infected but typically do not show signs of illness, these include cattle, sheep, goats, dogs, cats, bats, rodents, reptiles, amphibians, and birds.

Veterinarians working with animals including pigs, horses and donkeys need to be alert to the clinical signs of JE, and as a nationally notifiable disease, any suspicions about the presence of JE must be reported by calling the Emergency Animal Disease Watch Hotline on 1800 675 888, which will connect you with your local department of agriculture or primary industries.

In horses, many cases of JE are subclinical with most clinically affected horses showing only mild signs of disease. The clinical signs of JE in horses can include pyrexia, jaundice, lethargy, anorexia and neurological signs, which can vary in severity. Neurological signs can include incoordination, difficulty swallowing, impaired vision, and rarely the horse becomes over-excited. In some cases, a more severe encephalitis can occur.

Prevention strategies in horses include controlling mosquitos through the use of safe insect repellents, and rugging and hooding horses with lightweight summer rugs and fly masks to help protect them against mosquito bites. Stabling horses between dusk and dawn may also be beneficial as the mosquito that transmits JE feeds at night and is reluctant to enter dwellings.

In pigs, the most common clinical signs are mummified and stillborn or weak piglets, sometimes displaying neurological signs. Piglets infected after birth can develop encephalitis which presents as paddling or other neurological signs in the first six months of life. In other cases, wasting, depression or hindlimb paralysis may be seen in suckling piglets and weaners.

Adult sows do not typically show overt signs of disease. If boars are present on farm, they may experience infertility and oedematous, congested testicles. Prevention strategies against JE in pigs include controlling mosquitoes and using effective biosecurity measures. There is further information in the National Pork Biosecurity Manual.

As JE is a zoonotic disease, veterinarians should consider getting a JE vaccination when these become available. It is important to also try to prevent mosquito bites by using an effective insect repellent, and wearing long loose-fitting clothing with covered footwear. Most JE infections in people are asymptomatic, however those with severe infection may experience neck stiffness, coma, and more rarely, potentially fatal neurological complications.

Lumpy skin disease in Asia

Lumpy skin disease (LSD) affects cattle and water buffalo. The disease has never occurred in Australia. LSD is an emerging threat as it continues to spread through Asia and in early March an outbreak was reported in Indonesia. More recently an outbreak was reported in Singapore. As the disease is spread by biting flies, mosquitos and possibly ticks, there is a possibility the disease will spread further and closer to our shores.

If an LSD incursion was to occur in Australia, this would jeopardise Australia’s access to economically important international markets particularly for live cattle and dairy products. The disease would be difficult and costly to eradicate as it requires extensive insect control, animal movement control and vaccination programs.

In cattle and water buffalo, LSD causes emaciation, infertility, mastitis and loss of production together with significant damage to their skin and hides caused by pox lesions. The department has developed a lumpy skin disease website resource to assist veterinarians and livestock producers with the identification of the disease.

If you work with cattle producers and animal owners, it is important to raise awareness of with them of the heightened risk of spread of LSD to Australia due to the current outbreak in Indonesia. If you suspect a disease outbreak or have seen something unusual and you’re not sure whether it’s an exotic pest or disease – please report it to the Emergency Animal Disease Watch Hotline on 1800 675 888. Funds for disease investigation are available through the National Significant Disease Investigation Program.

Some livestock producers and businesses may be reluctant to report signs of disease due to the fear of consequences, however it is important to reassure them that the government will work with business owners to identify whether a problem exists and how to manage it. The earlier a notifiable disease is reported, the greater the opportunity for quick and successful management resulting in less harm to businesses, livestock and Australia’s trade.

Vaccination against LSD is not currently available in Australia because the pre-emptive use of vaccination would mean that we lose our LSD-free status and the importation of LSD vaccine into Australia is not currently permitted. While vaccines are available overseas, and considered essential to managing LSD effectively, all commercially available vaccines contain live virus, and can cause some clinical signs of disease following vaccination.

I encourage you to download and familiarise yourself with the ‘Emergency animal disease field guide for Australian veterinarians’. Veterinarians play a vital role in monitoring and protecting animal health in Australia, and I would like to extend my gratitude to everyone in the veterinary community for your vigilance and support as we all work to counter the threat of diseases like Japanese encephalitis and Lumpy skin disease. Please follow my social media channels on LinkedIn and Twitter for the latest updates.