Lumpy Skin Disease
Lumpy Skin Disease
The most important role for the spread of lumpy skin disease is indirect pathogen spread by insects and mites (vectors), e.g. horseflies, flies, midges, mosquitoes, mites. Transmission is also possible through direct contact, infected semen, untreated animal hides and skins and their products (e.g. hunting trophies), raw meat products, raw milk products and through animal feed obtained from them, including colostrum.
Due to the diversity of vectors and the resulting control methods, the control of LSD vectors represents a major challenge for the EU countries concerned, which is almost impossible to overcome. So far, only few scientifically sound data on vectors in Europe are available.
Apart from the killing of infected and susceptible animals in the herd ("total stamping out") and movement restrictions on susceptible animals and animal products, blanket vaccination (coverage at 95 %) with a homologous, attenuated strain of LSDV (Neethling) is considered to be the most effective measure to control the disease. The vaccine is not licensed in Europe; its use requires approval by the competent authorities.
Lumpy skin disease virus (LSDV) belongs to the genus Capripoxvirus, along with sheep pox virus, Sheeppox virus (SPV), and goat pox virus, Goatpox virus (GPV). Host animals in Europe are mainly bovine ruminants (cattle, buffalo, bison, zebu) kept as livestock. Despite communal husbandry with small ruminants and New World camelids, no clinical case of LSD has occurred in Europe in sheep, goats, alpacas, or llamas. Wild ruminants have also not been affected. Testing on roe deer in epidemic areas of Bulgaria has been negative to date. The first detection of Lumpy Skin Disease in the EU occurred in August 2015 in Greece, in the Evros Delta near the Turkish-Greek border. Starting in Greece, the disease spread to southeastern Europe. In 2016, there were numerous outbreaks in Bulgaria, northern Macedonia, Greece, Albania, Montenegro, Kosovo, and southern Serbia. In Europe, several measures succeeded in controlling the animal disease, mainly with comprehensive vaccination measures. In the Balkan region, outbreak numbers of Lumpy Skin Disease decreased from 7,483 in 2016 to 385 in 2017; as of 2018, no case of LSD was reported in Europe. LSD outbreaks have been reported in Asia Minor, Russia, Israel, East Africa, China, Bangladesh, and India, among other countries. In these countries, heterologous vaccines against LSD were often used or the vaccination requirement was lifted. European figures confirm that vaccinating cattle with a homologous vaccine - recommended by EFSA in 2016 - is the most effective way to control the disease.
Transmission by vectors, blood-sucking insects and mites, is cited as the main cause of the spread of the animal disease in Europe, along with the movement of subclinically diseased animals. Since vector research is costly and direct control of the animal disease was the first priority in the affected countries, only few scientifically sound data on vectors in Europe have been collected so far. Transmission of the disease by Culicidae(Aedes aegyptii) and Muscidae(Stomoxys calcitrans, Haematobia irritans) as well as by mites(Rhipicephalus appendiculatus, R. decoloratus and Amblyomma hebraeum) is considered scientifically proven. Other possible vectors are bloodsucking mites(Ixodidae), Culicidae (mosquitoes), Culicoides (e.g., the gnat Culicoides punctatus), and Muscidae (e.g., Stomoxys calcitrans). The pathogens can also be spread by indirect contact, e.g., through infected semen, through stable equipment or transport vehicles that have come into contact with pathogens (e.g., through infected insects in the loading area, through tire contact with crusts that have fallen off infected animals), and iatrogenically. Direct contact between infected and healthy adult animals plays a rather minor role in the transmission of the disease. Calves can become infected by sucking on the udder of infected dams. Infected dams can give birth to infected calves with skin lesions. Capripox viruses have been detected in untreated animal hides and skins and their products (e.g., hunting trophies), in raw meat products and raw milk products, and in animal feed derived from them.
Most outbreaks of LSD in Europe have occurred between May and August - the time of year with the highest vector density. Vaccination should therefore be carried out before vectors appear. Since no season in Europe is free of vectors or many vectors are also present in stables, LSD outbreaks have also occurred in some cases outside the specified period. Areas with high cattle density, common pastures and water points increased the risk of spreading the disease. Standing small water bodies adjacent to farms should therefore be avoided, as they are breeding sites for insects. Geographic topography mattered only insofar as arthropod assemblages were greater along water bodies. Infections with LSD occurred even in areas with altitudes up to 1500 meters (Montenegro, Turkey). High vector density, high population density of livestock, outbreak foci around agricultural farm aggregations as well as a convenient geographical location of outbreak foci was beneficial for the spread of LSD. Mortality and morbidity in infected European cattle herds varied regionally from 0-100% in the 2016 and 2017 epidemic years; on average, morbidity was 0.8-7.2% in Albania, for example, and mortality was 0.3-2.9%.
The course of the disease in cattle is acute to subacute, sometimes chronic. Typical symptoms are:
- a papulo-vesicular exanthema, which may appear in the form of 0.5-5cm skin nodules, preferentially on the head, neck, tail area, perineum, external genital organs (udder mastitis!) and extremities. Only 40-50% of cattle develop generalized skin swelling.
- biphasic fever episodes of up to 41 °C
- severely enlarged lymph nodes
- necrotic lesions in the organs of the respiratory tract (trachea, lungs), skeletal muscles, subcutaneous tissue, stomach and uterus
- increased salivary and lacrimal flow
- dullness, loss of appetite, weight loss
- conjunctivitis (can lead to blindness)
- lack of acquiescence reflex in female animals
- abortions due to infection
Differential diagnoses include infection with BHV-2 (syn. Pseudo lumpy skin disease), parapoxia, demodicosis and dermatophilosis, an infection with the bacterium Dermatophilus congolensis.
Samples (skin necrosis, tear fluid, salivary fluid, serum and EDTA blood) should be taken by the official veterinarian if there is the slightest suspicion.
Control / Prevention
Due to the diversity of the vectors and the resulting control methods, the control of LSD vectors has been a major challenge for the affected countries of the EU, which can hardly be overcome. To date, therefore, few scientifically sound data on vectors in Europe are available. In addition to the killing of infected and susceptible animals in the herd ("total stamping out") and movement restrictions on susceptible animals and animal products, blanket vaccination (coverage at 95%) with a homologous, attenuated strain of LSDV (Neethling) is considered the most effective measure to control the disease. The vaccine is not licensed in Europe; use requires approval by the relevant authorities. At 28 days after vaccination, most cattle were protected by antibodies. A small percentage of cattle developed symptoms such as fever, milk drop, edema, and skin nodules near the injection site 2 weeks after vaccination. The symptoms disappeared after a short time. Vaccination in Asia with a heterologous vaccine strain, a sheep or goat pox virus strain, has lower efficacy. In these countries (e.g., Turkey), the disease has not been completely eliminated to date. The compliance with biosecurity, targeted timely information campaigns, the care of the agricultural population, the culling of all animals of an infected farm as well as the disease-relevant disposal of carcasses were a major challenge in the affected regions during the epidemic. The application of repellents in the barn, disinfection of farm vehicles used in the epidemic area, affected barns and farm tools also contributed significantly to vector control.
Skin lesions, blood and excretions (tear fluid, saliva) are used for diagnostic examinations. The samples are analyzed using internationally recognized molecular biological (PCR and sequencing), electron microscopic, virological (isolation by cell culture) and serological methods (SNT, ELISA). The National Reference Laboratory for Capripox can distinguish between field and vaccine virus by PCR. The diagnostic methods are also used in exclusion diagnostics. Exclusion diagnostics can be used not only to record the early detection of an epidemic event; it is also used to maintain the competence of laboratory diagnostic tests and the emergency plan. For example, in 2017 and 2018, 15 cattle each with mostly conspicuous skin symptoms were examined as part of the exclusion diagnostics. All cases were LSD negative.
Sample type for sample collection:
- Skin lesions and/or skin crusts
- Salivary fluid (native in tubes or swabs possible - no bacteriological swab transport)
- Nasal and ocular fluid (with swab - no bacteriological swab transport media)
- Blood (EDTA/Heparin) and serum
- Skin lesions and/or skin crusts
- Lymph nodes
- Lungs and altered regions of the respiratory tract
- Nasal fluid (with swab - no bacteriological swab transport)
Institut für veterinärmedizinische Untersuchungen Mödling
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