Lumpy skin disease

LSD virus, which belongs to the genus Capripoxvirus of the family Poxviridae.

Before 2012, the distribution of LSD had been limited to Africa and Israel. Since then, LSD has spread to many parts of the Middle East, southeast Europe, the Balkans, the Caucuses, the Russian Federation and Kazakhstan.

Since 2019, LSD has spread throughout Asia and has been reported in:

• Bangladesh (2019)
• China (2019)
• India (2019)
• Nepal (July 2020)
• Kinmen County, Taiwan (July 2020)
• Bhutan (October 2020)
• Vietnam (November 2020)
• Hong Kong (November 2020)
• Myanmar (November 2020)
• Sri Lanka (January 2021)
• Thailand (April 2021)
• Cambodia (June 2021)
• Malaysia (June 2021)
• Laos (July 2021)
• Pakistan (March 2022)
• Singapore (March 2022)
• Indonesia (March 2022).

Further regional detections of LSD are likely.

LSD affects:

• cattle (Bos inducis and Bos taurus)
• water buffalo (Bubalis bubalis).

Bos taurus cattle are generally more susceptible than Bos indicus cattle.

Jersey, Guernsey, Friesian and Ayrshire breeds are particularly susceptible.

LSD virus does not affect humans.

The World Organisation for Animal Health Terrestrial Animal Health Code describes the incubation period as 28 days.

Clinical signs in cattle may range from inapparent to severe.

Infected animals can have a fever which may exceed 41°C.

It is frequently accompanied by:

• watering eyes
• increased nasal and salivary secretions
• loss of appetite
• reduction in milk production
• depression
• enlarged superficial lymph nodes.

Within 1–2 days of the onset of fever, skin nodules of 2–5cm in diameter develop, particularly on the head, neck, limbs, udder, genitalia and perineum. These nodules are circumscribed, firm, round and raised, and involve the skin, subcutaneous tissue and sometimes even the underlying muscles.

Skin nodules may become necrotic (localised dead tissue). Some nodules may remain in place, while others slough, leaving a hole of full-skin thickness, which may become infected by bacteria or maggots.

Limbs, brisket and genitals can become swollen.

Lesions can also be found in the mouth, gastrointestinal system, trachea and lungs occasionally resulting in secondary pneumonia.

Animal production implications include:

• emaciation
• decreased milk production
• damaged hides
• reproductive losses.

Animals that recover may remain in extremely poor condition for some time.

Morbidity rates vary greatly and typically range between 10–20%. Mortality rates of 1–5% are usual.

The response to an outbreak in Australia would have social, environmental and economic impacts, including substantial export implications.

If LSD becomes established in Australia, economic losses would be expected due to stock losses and reduced production, including reduced milk yield, loss of animal body condition and rejection or reduced value of the hide.

The transmission of LSD virus is not completely understood.

The main route of transmission between animals is thought to be mechanical transmission by arthropod vectors such as biting flies, mosquitoes and possibly ticks.

The prevalence of insect vectors may affect the rate of transmission of the virus. This is supported by the observed reduction in LSD transmission after cold weather, which is often associated with reduced insect vector populations.

Direct contact between infected animals is considered to play a minor role in virus transmission.

Infected bulls can excrete the virus in semen and experimental transmission has been demonstrated.

The role of fomites (inanimate objects that could carry the virus) in transmission is unknown, though it is thought that contaminated equipment (e.g. re-used hypodermic needles) may contribute to virus spread.

The greatest period of risk is when:

• infected arthropod vectors are prevalent
• a naïve susceptible population exists (as it does in Australia)
• vaccination is not practised (as in Australia).

Risk of entry into Australia

Potential pathways of introduction to Australia include:

• movement of infected animals
• introduction of the virus via arthropod vectors.

LSD is unlikely to enter Australia through the import of live cattle or their germplasm as we do not import these from LSD-infected countries.

The most likely route for LSD to enter Australia is through the virus being carried by vectors into northern Australia from neighbouring countries where the disease is present either by:

• moving across the seas north of Australia
• entering through international ports.

The Australian Government constantly monitors the disease status of trading partners to manage the risk of importing products that may harbour LSD. They conduct evidence-based risk assessments which are used to set import requirements. This mitigates the disease risk associated with certain imported products including bovine genetic material and dairy.

Be aware of the clinical signs of LSD. If LSD is introduced to Australia, it is critically important to identify it quickly and minimise the impacts. If you suspect the presence of this disease in any cattle or water buffalo, you must report it to either:

• Biosecurity Queensland on 13 25 23
• the Emergency Animal Disease Hotline on 1800 675 888.

Suspect cases of LSD should be investigated. Where appropriate, diagnostic samples should be collected from representative animals and submitted to the Biosecurity Sciences Laboratory (BSL), including the specimen advice sheet for appropriate analysis and assessment of whether further testing will be required at the Australian Centre for Disease Preparedness at Geelong.

Diagnosis of LSD is based primarily on detection of the virus in lesions. Detection of antibody in serum may also aid diagnosis.

Specimens that should be collected from live animals include:

• blood (EDTA – from animals with fever)
• serum
• nodular fluid
• scabs
• skin scrapings from lesions
• skin biopsies.

At post-mortem, a range of samples, both fresh and fixed, should be taken from skin lesions, lesions in the respiratory and gastrointestinal tracts, and other internal organs.

Blood and unpreserved tissue should be chilled at 4°C and sent in an esky with frozen gel packs. Do not freeze samples. Formalin fixed tissue can be sent at room temperature.

Prevention

Vaccines are commercially available overseas. They are not currently available in Australia.

Treatment

There is no effective treatment for LSD. Treatment of secondary infections and supportive care may be necessary.