Lumpy Skin Disease (LSD) is a non-zoonotic viral infection that mainly affects cattle and is uncommon in buffaloes. It was first reported in Zambia in 1929, and primarily thought to be the result of poisoning or hypersensitivity reaction to insect bites. The cause was later identified as Lumpy Skin Disease Virus (LSDV) after the viral strain was first isolated in Kenya in 1958. Until the 1980s the disease was confined within the continent of Africa. The first reported infections outside the mainland were 1989 from Israel and later in 2016 in South East European Nations. In the Indian subcontinent, the disease was first seen in Bangladesh in September 2019, immediately followed by India in November 2019. The first case of LSD in Nepal was reported on 24th June 2020 in Morang[2]. It is prevalent in every 77 districts, with morbidity of 4-45% and a mortality rate of less than 10%[1]. World Organisation for Animal Health (WOAH) has identified it as a transborder communicable disease that must be reported.
Lumpy Skin Disease Virus (LSDV) is a member of the Capripoxvirus genus from the family Poxviridae. Poxviridae is the family of the largest viruses consisting of a single, linear molecule of double-stranded DNA coding for around 200 proteins which can cause disease in most domestic animals. Nepal LSDVs resemble the Bangladesh and Indian isolates and the historic isolates from Kenya.[3] LSDV can be destroyed at 55°C for 2 hours and 65°C for 30 minutes.Virus can also be recovered from skin nodules kept at –80°C for ten years and infected tissue culture fluid stored at four °C for 6 months. It demonstrates high susceptibility to the ether, chloroform, formalin, and some detergents, e.g. sodium dodecyl sulfate, phenol, sodium hypochlorite, Virkon® (2%) and quaternary ammonium compounds.
Insect vectors (mosquitoes, flies, ticks, etc.), contaminated needles, and vehicles from the infected area play a significant role in the transmission of this virus. LSD can spread rapidly during summer and autumn seasons. The moist and warm environment favours the growth and reproduction of houseflies, mosquitoes, etc. Stomoxys, Biomyia fasciata, Tabanidae, Glossina, and Culicoides species are considered to be the main vector for transmission.Transmammary infections are found to be common while some experimental case show the vertical transmission from mother to offsprings.[5]
Cattle infected with LSD show the following symptoms:• Firm circumscribed skin nodules (1-5 cm) that undergo necrosis and brust.
• Firm circumscribed skin nodules (1-5 cm) that undergo necrosis and brust.
• Biphasic fever (40-410C) .
• Subcutaneous edema of the limbs and ventral parts of the body.
• Watery secretions from eyes.
• Lymph nodes enlargement, profuse salivation, pneumonia.
• Marked reduction in milk ( upto 80%) and meat production.
• Pregnancy termination is probable.
• Nodular lesions and ulcerations on intestinal mucosa in severe cases.
• Emaciation, lethargy, recumbency and death.
• Long-term symptoms of mastitis,pneumonia and deep holes in the hide in recovered cattle.
The severity of animals infected with the disease can be predicted by the following symptoms pattern;
Very mild Cases: Only skin nodules(1-3cm), no fever
Mild Cases: Skin nodules (3-5 cm) + fever (40-410C)
Moderate Cases: Skin nodules + fever + not responding to treatment.
Severe Cases: Skin nodules + fever + not responding to treatment , lymph nodes enlargement, dependent oedema, salivation, pneumonia etc.
Extreme Case: High emaciation, lethargy, recumbency and death.
Being a viral disease it doesn’t have any specific drug for treatment. Different allopathic and herbal medications are being used for symptomatic treatment along with supportive therapy.Majority of treatment protocols include:
• Isolation of infected animals and resting the working animals with symptoms.
• Enough fresh feed, clean water and electrolyte should be provided.
Following drugs can be used to ease animal and to reduce complication;
• Anitpyretics (paracetamol/meloxicam) to reduce fever.
• Chloropheniramine maleate/ Pheniramine maleate for the itchy skin nodules.
• 20% Dextrose saline/ Ringer’s lactate if the animal is too weak or is not taking feed and water.
• Ivermectin- 1% (avoid in case of fever)
• Antiseptics and fly repellent in the brust skin nodules.
• Vitamin E and Selenium supplement.
• Use antibiotics if infection spreads over Skin, GI tract, Urinary tract, Lungs;
(oxytetracyclin/ tetracyclin) – for non pregnant and non lactating animals
(procaine Penicillin) – for pregnant and lactating animals.
The treatment protocols should be followed under the supervision of veterinarian.
The preventive actions against LSD include;
• Vaccination of cattle (above 3 months) on yearly basis. This should be done in the areas free from LSD prior to its arrival.
• The offspring from the infected mother should be vaccinated after 4 months.
• Animals recovered from LSD should be vaccinated only after one year.
• Infected bulls should not be used for breeding until it is fully recovered.
• Killing mosquitoes, flies, bugs and fleas around the farm premises.
• Isolate the new animal for 28 days before introducing it to the herd.
• Restricting the animal movement and trading to and from epidemic areas.
• Regular disinfection of farm atleast by phenol water.
• The carcass of an animal should be properly disposed of by deep buring or burning.
Vaccination is the only measure to prevent LSD. Various vaccines are made available which show variability in quality, cost and efficacy. It may not be economically feasible or the vaccine may not be sufficienly available to fully vaccinate and eradicate disease, but vaccinated cattle should be marked. These vaccinated and non vaccinated cattle can be managed together, and using herd immunity to reduce losses from outbreak.Presently live attenuated vaccines are more commonly used. However such vaccines have high risk of homologous recombination with other viruses causing animals to be infected with other new viruses. An inactivated vaccine targeting LSDV has not been developed yet.
The on field diagnosis of LSD relies on clinical symptoms to determine whether the cattle are infected. However early stages of infection only show fever and some skin lesions. This may be misinterpret as other similar disease like bovine herpesvirus infection, demodicosis, bovine viral diarrhoea, mucosal disease and bovine malignant catarrhal fever which limits the chances of early diagnosis demanding the reliable diagnostic kits.Research activities are focused on developing more effective vaccines and development of diagnostic kits.
References:
1. Central Veterinary Laboratory https://cvl.gov.np/public/uploads/downloads/179749733-1636443287-1214080433.pdf
2. Sagar Regmi. Lumpy skin disease (LSD) outbreak in Nepal. Authorea. September 11, 2020.
3 Koirala P, Meki IK, Maharjan M, Settypalli BK, Manandhar S, Yadav SK, Cattoli G, Lamien CE. Molecular Characterization of the 2020 Outbreak of Lumpy Skin Disease in Nepal. Microorganisms. 2022 Feb 28;10(3):539. doi: 10.3390/microorganisms10030539. PMID: 35336114; PMCID: PMC8954389.
4. Liang Z, Yao K, Wang S, Yin J, Ma X, Yin X, Wang X and Sun Y (2022) Understanding the research advances on lumpy skin disease: A comprehensive literature review of experimental evidence. Front. Microbiol. 13:1065894. doi: 10.3389/fmicb.2022.1065894
5. Şevik, M., and Doğan, M. (2017). Epidemiological and molecular studies on lumpy skin disease outbreaks in Turkey during 2014-2015. Transbound. Emerg. Dis. 64, 1268–1279. doi: 10.1111/tbed.12501
6. Treatment guidelines for LSD issued by Nepal government, Department of livestock services: http://dls.gov.np/noticefiles/Treatment-Guidelines-LSD-1687262199.pdf .
