Lumpy skin disease

Lumpy skin disease (LSD) or nodular dermatosis is a notifiable viral disease of cattle. The disease is caused by a pox virus of the genus Capripox virus. Spread through (in)direct contact with body fluids is the main route of infection, and biting insects can also transmit the virus. Wageningen Bioveterinary Research (WBVR) conducts research into this disease.

Notifiable means that suspicions of lumpy skin disease infection must be reported to the NVWA (Netherlands Food and Consumer Product Safety Authority). Lumpy skin disease is a “Categorie A” disease (Animal Health Law).

The disease is caused by the lumpy skin disease virus (LSDV, Family of Poxviridae, genus Capripox virus). Cattle and the African Cape buffalo are the most susceptible to the disease. Morbidity can be as high as 50% of the flock, while mortality is usually limited to a maximum of 10%. The disease also occurs in oryx, giraffe, and impala. The virus is harmless to humans.

Lumpy skin disease has never been reported in the Netherlands. The Netherlands is therefore historically free of lumpy skin disease.

Clinical signs lumpy skin disease

The severity of the disease can vary greatly per animal species, but the virus also varies in virulence, the pathogenic capacity. The course of the disease generally has two phases in which fever occurs.

First stage

In the first phase, in addition to fever, a poor appetite, drooling and reduction in milk yield are also observed. Eye infections also occur that can even lead to blindness. In this phase, several lymph nodes are also enlarged.

Second stage

The second stage begins with the appearance of painful smallpox (nodules) with a diameter of 1-2 centimeters. In this phase inflammation also develops in the mouth and the airways. The smallpox often becomes inflamed and may later fall off, leaving deep scars.

Oedema in the legs is also common. Additional bacterial infections in the udder (mastitis) and tendons and joints (lame) are reported complications of this disease. Lumpy skin disease virus infection can sometimes lead to abortion and (temporary) infertility.

Spread of lumpy skin disease

Lumpy skin disease was first reported in Zambia in 1929. Reports from other countries soon followed, and from the 1950s onwards, it occurs in all countries south of the Sahara and the island of Madagascar. In 1988, the disease broke out in Egypt and spread to Israel. The disease also occurs in Asia. In 2017, LSD was found in Greece and spread throughout the Balkans.

Bodily fluids

Infected animals excrete the virus in bodily fluids such as nasal discharges, saliva, milk and semen. Large amounts of virus are also found in open wounds from smallpox. Spread through direct contact or indirect contact with these bodily fluids are the main routes of infection. Biting insects, for example the stable fly Stomyxos calcitrans, can also transmit the virus through their mouthparts. This is mechanical transfer, whereby the virus does not multiply in the insect. Lumpy skin disease virus is very stable in tissue and body fluids and can survive for a long time in the absence of daylight, for example in bedding in dark stables.

Infections in and the role of wild ruminants are not well known, but several species are susceptible to the virus. Imports of cattle and wild ruminants from infected areas are prohibited.

Diagnostics lumpy skin disease

Lumpy skin disease is a notifiable animal disease. Wageningen Bioveterinary Research (WBVR) is the national reference laboratory for sheep-and-goat pox and has ISO-certified tests to diagnose suspected lumpy skin disease.

Serological test

Antibodies against lumpy skin disease virus (LSDV) after infection or vaccination can be detected with the ELISA, the ImmunoPeroxidase Monolayer Assay (IPMA) or the serum neutralization test (SNT). The ELISA is the first choice for detecting antibodies. The IPMA is more sensitive than the ELISA and particularly suitable for serological confirmation of recent LSDV infections. The SNT can confirm positive ELISA or IPMA results, although the SNT is less sensitive. Clot blood (serum blood) is used in these serological tests.

PCR test

The virus can be detected by the PCR test for Capripox viruses, LSDV and Sheep and Goat pox virus. LSDV is only found in cattle. Positive results for material from large ruminants is therefore LSDV. This can also be confirmed with the PCR test specific for LSDV. There is also a PCR test that distinguishes between LSDV and live attenuated (LAV; live-attenuated vaccine) LSDV (DIVA PCR test for LSDV). Nasal and eye discharges and skin biopsies of smallpox or lymph nodes are very suitable for detecting virus. Whole blood (EDTA blood) is less suitable. Samples of blood or organs must be transported on ice (not frozen).

Vaccine lumpy skin disease

Live attenuated (LAV; live-attenuated vaccine) lumpy skin disease virus is a DIVA vaccine, but is not registered in Europe. LAV for lumpy skin disease is not available in the Netherlands. A vaccine based on the sheep-and-goatpox virus elicits cross-immunity against lumpy skin disease. After vaccination, the animals are protected for at least two years and probably for the rest of their lives.

Prevention and control of lumpy skin disease

To prevent is better than to cure, but preventive vaccination against lumpy skin disease is not applied due to financial considerations. To prevent the disease from breaking out in Europe, animals are banned from infected regions or checked extensively before they are allowed. In an outbreak of lumpy skin disease, vaccination is given to prevent further spread of the disease.

During the outbreak in 2017, the European Commission gave permission to vaccinate with an unregistered lumpy skin disease vaccine in several Balkan countries. Vaccination has completely eradicated the disease, but it does have negative (temporary) consequences for exports. In countries where lumpy skin disease is prevalent, insect control in addition to vaccination is an important way of limiting introduction to a company and limiting damage.