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.

In 2019, LSD was reported for the first time in Bangladesh, China and India. In July 2020, it was reported in Nepal and in a territory of Taiwan close to China. The most recent outbreaks were reported in Bhutan (October 2020), Vietnam, Hong Kong and Myanmar (November 2020), Sri Lanka (January 2021), Thailand (April 2021), Cambodia (June 2021), Malaysia (June 2021), Laos (July 2021), Pakistan, Singapore and Indonesia (March 2022).

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 OIE Terrestrial Animal Health Code describes the incubation period as 28 days.

LSD-infected animals may produce clinical signs ranging 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, and 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 and consequently the numbers of animals infected and showing clinical signs. Reduced numbers of infected animals following cold weather supports the association of cold weather with a lower prevalence of insect vectors.

Direct contact between infected animals is considered to play a minor or negligible 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.

Both of these introduction pathways are considered to be low likelihood because:

• Australia does not import live cattle or their germplasm from LSD-infected countries
• the numbers of arthropod vectors entering via aircraft is very low.

The Australian Department of Agriculture, Fisheries and Forestry constantly monitors the disease status of trading partners to manage the risk of importing products that may harbour lumpy skin disease. The department conducts 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.

Producers are reminded to be aware of the clinical signs of LSD. If LSD is introduced to Australia, it is critically important to identify it quickly and therefore minimise the impacts. If you suspect the presence of this disease in any cattle or water buffalo, you must report it to Biosecurity Queensland on 13 25 23 or contact 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 (PDF, 630KB) 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, and skin scrapings from lesions or 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.