Introduction

Lumpy Skin Disease (LSD) is one of the most important infectious diseases affecting cattle, and animals of all ages are susceptible. Outbreaks can result in significant financial losses, particularly for dairy farmers. Fortunately, the disease can be effectively prevented and controlled through annual vaccination.

The virus affects all breeds of cattle, although clinical signs are often more noticeable in dairy breeds such as Holstein-Friesians and Jerseys because of their thinner skin.

Lumpy Skin Disease is an acute, subacute, or sometimes mild viral disease characterised by:

• Fever
• Multiple firm skin nodules
• Lesions in the mouth and respiratory tract

The disease is caused by a poxvirus (the Neethling strain) and is widespread throughout Southern Africa.

Economic Importance of Lumpy Skin Disease

During an outbreak, between 1% and 20% of cattle on a farm or within a herd are typically affected. In severe outbreaks, up to 100% of the herd may become infected.

Although mortality generally remains below 3%, losses can vary from no deaths to as much as 40% of a herd under severe conditions.

Economic losses result from:

• Weight loss
• Dramatic reduction in milk production, with some cows stopping milk production completely
• Reduced fertility in both cows and bulls
• Abortions
• Permanent skin damage that lowers hide value
• Severely affected animals sometimes needing to be euthanised because full recovery is unlikely

Outbreaks in dairy and beef herds can therefore cost farmers thousands of rands.

Transmission and Spread

Lumpy Skin Disease usually occurs sporadically, although in some years it spreads rapidly and becomes epidemic.

Some cows may only develop mild disease, while their calves become severely affected with typical lesions.

Biting insects are believed to play a major role in introducing the virus into cattle populations. Once the disease is established on a farm, it spreads from infected to susceptible cattle through direct contact.

The virus is present in:

• Saliva
• Skin lesions

It spreads mainly through:

• Direct contact between animals
• Shared feed troughs
• Shared water sources

Some infected cattle show no clinical signs but still shed the virus in their saliva, making them an important source of infection.

The virus can also be transmitted through milk to suckling calves.

Outbreaks often follow roads, railway lines, and livestock movement routes as infected animals are transported between areas.

There is also some evidence suggesting that sheep may act as carriers of the virus.

When Does Lumpy Skin Disease Occur?

The disease is most common during the wet summer and autumn months, particularly in cattle grazing in low-lying, waterlogged areas.

However, outbreaks can also occur during dry seasons.

Clinical Signs

The incubation period is approximately 7 days.

This is followed by a two-phase fever lasting 4 to 14 days.

During this period cattle may develop:

• Mucous or pus-like nasal discharge
• Excessive salivation
• Reduced appetite

Typical raised skin nodules (5–10 mm in diameter) usually appear shortly before or during the second fever phase.

Other clinical signs include:

• Inflamed eyes with excessive tearing
• Deep skin nodules affecting the skin, underlying tissue, and sometimes muscle
• A few to hundreds of nodules covering the body
• Sharp drop in milk production in lactating cows, which may be temporary or permanent
• Temporary or permanent infertility in bulls
• Permanent skin damage
• Abortions in severely affected pregnant cows

Recovery

As animals recover:

• Nodules may disappear rapidly, or
• Harden and remain as firm lumps for several months.

Some lesions break open early, forming raw, infected ulcers and abscesses.

Soft yellow-grey ulcers may also develop in:

• The mouth
• Nose
• Respiratory tract
• Forestomachs
• Reproductive tract

Swelling beneath the skin of the legs may occur and is often mistakenly diagnosed as snakebite.

This swelling may cause:

• Lameness
• Paralysis of the affected limb

Secondary bacterial infections can lead to pneumonia.

Weeks or months after recovery, some animals develop narrowing (stenosis) of the trachea, resulting in breathing difficulties.

Diagnosis

Diagnosis is generally based on the characteristic skin lesions and clinical signs.

Laboratory confirmation can be obtained by isolating the virus from skin lesions.

Diseases That Should Be Differentiated from Lumpy Skin Disease

The mucosal lesions of Lumpy Skin Disease should be distinguished from those caused by:

• Rinderpest
• Bovine Viral Diarrhoea (BVD)
• Mucosal Disease
• Malignant Catarrhal Fever

The skin lesions should be differentiated from those caused by:

• Insect bites
• Mange
• Demodectic mange (Demodex infestation)
• Bovine besnoitiosis (“elephant skin disease”)

Prevention and Control

Because biting insects play a major role in transmitting the disease, quarantine measures and movement restrictions alone are generally not very effective.

However:

• Sick animals should be isolated immediately.
• They should not share feed or water troughs with healthy animals.
• Saliva and skin lesions are highly infectious.
• Semen from infected bulls also contains the virus.

Vaccination

Vaccinate all cattle older than 6 months every year during spring.

Important vaccination guidelines:

• Vaccination is safe for pregnant cows.
• Every animal should be vaccinated annually.
• During an outbreak, use a new sterile needle for each animal to avoid spreading the virus during vaccination.
• Calves younger than six months born to unvaccinated cows may not have protective colostral immunity and should be vaccinated as soon as possible if the disease is present in the area.

Following vaccination:

• Immunity begins developing after approximately 10 days.
• Full protection develops after 3 weeks.

The vaccine should be protected from direct sunlight, as ultraviolet (UV) light will inactivate it.

Vaccination generally provides excellent immunity.

Some cattle appear naturally resistant and may not develop measurable antibodies after vaccination. Their calves may therefore not receive adequate immunity through colostrum and remain susceptible to infection.

Treatment

Consult a veterinarian immediately.

Treatment consists mainly of supportive care, including:

• Good nursing and management
• Symptomatic treatment
• Antibiotics where necessary to prevent or treat secondary bacterial infections

Preventive vaccination remains the single most important method of controlling Lumpy Skin Disease, particularly given the increase in outbreaks seen in recent years.

For more information, or if you have any concerns or need assistance with disease prevention, treatment protocols, or selecting the correct products, don’t hesitate to reach out to our resident livestock vet, Dr. Izak van Rensburg, at:

WhatsApp: 081 031 4694

Email: izakjvr@hotmail.com

Original article written by Dr. Faffa Malan and Dr. Jan du Preez.