Lumpy Skin Disease: An emerging threat for the dairy farmers of North East India
Dr. Rajat Buragohain
Department of Animal Nutrition
College of Veterinary Sciences & Animal Husbandry
CAU (I), Selesih, Aizawl, Mizoram – 796014
Background
Dairy farming significantly contributes to the livelihood of the people of North East (NE) India. This sector plays important role in generating employment and providing a regular source of income for rural households. The small and marginal farmers utilize bulls and bullocks for various draught purposes. In recent years, popularity of dairy farming is increasing as demands for milk and milk products are increasing in the NE states including the hilly states. Knowing as ‘Meat eating bowl’ to rest of India, people of North East region are blamed for reluctance in drinking milk and its products, but with the increasing health awareness about the benefits of consuming milk and milk products, demands for milk and milk products are increasing manifolds than before. This has encouraged the farmers for opting dairy farming as the profitable business enterprise in recent years.
Proper management is the key for successful dairy enterprise. Health management is very important as good health can only ensure optimum productivity. In the early months of 2020, simultaneously with the COVID-19 pandemic, a viral disease has emerged in some parts of the NE India among the cattle population causing concerns among the dairy farmers. Recognized as Lumpy Skin Disease (LSD), a less prevalent viral disease in India, was first reported in Odisha in its four districts namely, Mayurbhang, Balasore, Bhadrak, Kendrapara and Cuttack in August, 2019. It was subsequently transmitted to the cattle population other states including the NE. In Assam, cases of LSD were diagnosed in Kamrup district of Brahmaputra valley and Cachar, Karimgang, and Hailakandi district of Barak velly in the month of June, 2020 among the cattle population. It was then spread to other districts of the state. Subsequently, the disease is also spreading to other states of the NE India and if not, likely to spread unless controlled and restrictions are not imposed.
Lumpy Skin Disease (LSD) is a viral disease of cattle caused by LSD virus. The virus is generally transmitted by arthropod vectors such as house flies etc. and the disease is more prevalent during the warm and humid months of the year. Community grazing and watering in the same place helps in transmission of LSD virus. The characteristics lesions of the disease are firm, circumscribed, few (mild forms) to multiple (severe forms) skin nodules, visible in the mucous membranes of respiratory, urogenital system and other internal organs. In severe cases, there will be continuous high fever (40-41.5°C), depression and anorexia. Milk production will be reduced in lactating animals. Abortion may occur in pregnant animals and there may be temporary or permanent sterility, damages to hide. Death may also occur in severe and untreated cases.
The virus and the susceptible hosts
The lumpy skin disease virus (LSDV) is a member of the genus Capripoxvirus within the family Poxviridae, which is closely related to the capripoxvirus causing sheep and goat pox. It is a large stable DNA virus. The most susceptible animal is cattle and Asian water buffaloes. However, morbidity rate is significantly lower in buffalo (1.6%) than in cattle (30.8%). The susceptibility of wild ruminants or their possible role in the transmission of LSD is not known. Lumpy skin disease does not affect humans.
The LSD was first reported in Zambia of South Africa in 1929, after which it was spread slowly to other states of the continent. Besides the African continent, the disease was also reported in Egypt and Israel between 1988 and 1989 and again in 2006. During 1991-2000, LSD was reported in the Middle Eastern, European and West Asian regions. It then slowly invaded the new territories like the Middle East and Turkey. It was reported in most of the Balkan countries, the Caucasus, and the Russian Federation since 2015. In India, LSD was first reported in Odisha in 2019 in four of its districts namely, Mayurbhang, Balasore, Bhadrak, Kendrapara and Cuttack and then slowly spread to other states including the North Eastern states.
Transmission
The LSD is transmitted by vectors which vary depending on the geographical regions and ecosystems. Therefore, outbreaks of LSD are usually seasonal, but may occur at any time of the year depending on vector prevalence. The common stable fly (Stomoxys calcitrans), the Aedes aegypti mosquito, and some tick species of the Rhipicephalus and Amblyomma spp. have the ability to spread the LSD virus from animals to animals. Direct contact is considered ineffective as a source of infection, but may occur as the infected animals excrete infectious LSD virus in the saliva, nasal and ocular discharges, which may contaminate feeding and drinking sites as well feeds and water. The natural or farm environments may remain contaminated for a long time without thorough cleaning and disinfection. The virus also persists in the semen of infected bulls and therefore, natural mating or artificial insemination may be a source of infection for females. Infected pregnant cows may also deliver calves with skin lesions. The virus may be transmitted to suckling calves through infected milk, or from skin lesions in the teats of infected cows. LSD transmission may also occur via contaminated needles during vaccination or other injections if needles are not changed between animals or herds.
Incubation period
The incubation period may vary from 4 to 7 days, but may extend up to five weeks. Morbidity rate varies between 2 to 45%, however the mortality rate is generally less than 10%. Susceptibility to LSD infection depends on immune status, age, and breed of the animals. High yielding cattle are highly susceptible than the indigenous cattle. Asymptomatic animals are capable of transmitting the virus via blood-sucking vectors.
Symptoms of the LSD
- Ocular (Eye) and nasal (Nose) discharges are generally observed first.
- Subscapular and prefemoral lymph nodes become enlarged and are easily palpable.
- High fever (>40.50C) may persist for approximately a week.
- There will be visible sharp drop in milk yield.
- Appearance of nodular skin lesions of 10-50 mm in diameter varying from a few in mild cases to multiple lesions in severely infected animals.
- Nodules are mostly seen on the skin of the head, neck, perineum, genitalia, udder and limbs.
- Nodules involve all layers of the skin, subcutaneous tissue and sometimes even the underlying muscles.
- Necrotic plaques in the mucous membranes of the oral and nasal cavities cause purulent or muco-purulent nasal discharge and excessive salivation, containing high concentrations of virus.
- The centre of the lesion ulcerates and a scab forms on top.
- Skin nodules may persist for several months. Sometimes, painful ulcerative lesions develop in the cornea of one or both eyes, leading to blindness in worst cases.
- Skin lesions in the legs and on top of the joints may lead to deep subcutaneous infections complicated by secondary bacterial infections and lameness.
- Pneumonia caused by the virus itself or secondary bacterial infections, and mastitis are common complications.
- Sub-clinical infections are also common.
Treatments for LSD
There is no specific treatment for LSD virus infection. Timely vaccination is the only solution to get rid of the disease. Baring the pregnant animals, animals of all age groups can be vaccinated against LSD virus throughout the year. Vaccination should be done once in a year.
Once animals of a herd are infected, they should immediately be segregated and quarantined in separate shed away from the other animals. The infected animal shed should be disinfected with commonly available disinfectants like potassium permanganate, bleaching powder, phenyl etc. Phenyl can be used @ 2-3 ml/100 ml of water for disinfecting the animal shed.
Periodic deworming of the animals is necessary as the anthropods are the common transmitting vectors of LSD virus. The infected animals may be bathed with disinfectant solutions. The animals should not be allowed for grazing in disease prevalent areas. It is also important to avoid transporting animals during LSD pandemic and upmost care should be taken to avoid contamination of feed and water with the LSD virus.
In case of fever, antipyretic, anti-inflammatory drugs along with antibiotic therapy are indicated. Supportive therapy like provision for vitamin-mineral supplementation is also indicated depending on the severity of the disease. Diseased animals should always be provided with easily digestible balanced ration.
Preventive measures for LSD
- Separation of the diseased/suspected animals from the rest of the herd.
- A veterinarian should be called and the disease may be confirmed with the help of blood test.
- Infected animals must be fed separately and communal grazing must be avoided.
- Neighbouring farmers and those who have bought or sold animals from/to the affected farm recently, should be notified and be placed under intensified surveillance.
- Cattle with or without clinical signs should be also be tested for LSD virus.
- Cattle movement from/to the farm should immediately be stopped and visitors’ entry should be prohibited except for essential services.
- Clinical examinations on the rest of the animals of the herd should be carried out and records of rectal temperature should be kept for detection of fever.
- The equipment and materials used in the affected shed should be disinfected as well as the wheels of vehicles at the entry and exit points of the farm should also be disinfected.
LSD virus is very stable and can survive for long in extremely cold and dry environments. Scabs from skin lesions of infected animals may remain infectious for several months. Thorough cleaning and disinfection should be carried out in the affected farms, trucks, premises and potentially contaminated environments. Although LSD virus is sensitive to most disinfectants and detergents, in order to effectively decontaminate animal facilities and holdings, mechanical removal of surface material such as dirt, manure, hay and straw is essential beforehand. The disinfectant selected must be able to penetrate any organic material surrounding the infectious virus in the environment.
Efficient insect control reduces the rate of mechanical transmission. Anti-mosquito nets can be considered in cases when cattle are permanently kept indoors. The application of repellents can protect cattle from insects and ticks for short periods. When insecticides are used, withdrawal times for milk and meat need to be considered. Large-scale use of insecticides in the environment is not recommended as it may be harmful for human as well as other species. Limiting vector breeding sites such as standing water sources, slurry and manure can reduce the number of vectors on and around cattle.
Farm bio-security should be raised to the highest feasible level. As the disease is spread by vectors, such measures may not totally prevent an incursion, but the risk can be reduced. Purchase of new animals and introduction of new animals into herds should be minimised. If at all necessary, stock should be bought only from trusted sources. New animals should be separated/quarantined from the herd for at least 28 days. Farm visits should be restricted to essential services. All visitor vehicles and equipments should be cleaned while entering farms. Visitors entering farms should wear clean protective clothing.
Conclusion
Out of the many challenges faced by the cattle rearing communities, outbreak of LSD bears significance as it leads to huge economic losses for reduced milk production, reduced reproductive ability of the animals and by causing significant growth retardation in growing animals affecting their future performances. Timely vaccination is very important along with strict bio-security measures, optimum feeding, scientific management and other health care measures for controlling as well as preventing LSD infection.
Sources of Photograph: https://nenow.in/north-east-news/assam/lumpy-skin-disease-hits-cattle-of-assam-government-urged-to-raise-awareness.html.
References
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Feyisa, A.F. (2018). A case report on clinical management of lumpy skin disease in bull. Journal of Veterinary Science and Technology. 9(3): 538 (DOI: 10.4172/2157-7579.1000538).
Sudhakar, S.B., Mishra, N., Kalaiyarasu, S., Jhade, S.K., Hemadri, D., Sood, R., Bal, G.C., Nayak, M.K., Pradhan, S.K. and Singh V.P. (2020). Lumpy skin disease (LSD) outbreaks in cattle in Odisha state, India in August 2019: Epidemiological features and molecular studies. Transbound Emerging Diseases.00:1–15. (https://doi.org/10.1111/tbed.13579).
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LUMPY SKIN DISEASE : Emerging Threat to Livestock Industry
LUMPY SKIN DISEASE – Emerging Threat to Livestock Industry
