Cattle in Kashmir valley have been devastated by the outbreak of a serious viral infectious disease known as Lumpy Skin Disease (LSD). It is a notifiable transboundry vector borne viral disease that affects cattle and is caused by Lumpy skin disease virus (LSDV) belonging to Poxviridae family of genus Capripoxvirus. The disease is characterised by fever, lethargy, nodules on the skin, mucous membranes and internal organs, emaciation, enlarged lymph nodes, oedema of the skin, and sometimes death. Though the morbidity rate usually varies between 10 to 20% but morbidity as high as 100% has been noted in current outbreaks from different states of India. Mortality rates has gone upto 10%. In Jammu and Kashmir, last year 72,728 cattle were affected with this disease and 3,015 had died however this year many more are affected with severe signs and higher mortality due to re-emergence of LSD. This disease has caused severe losses to cattle farmers and has become cause of concern due to unusual nodular disease in animals, decrease in milk production, economic losses and deaths in cattle. Hence awareness about the disease and management of affected cattle is necessary.
History of disease
The disease originated in Zambia in 1929. Being a transboundry disease it has spread across borders. Since 2012 it has spread rapidly through the Middle East, southeast Europe and West and Central Asia. The disease first appeared in South Asia in July 2019, with Bangladesh reporting an outbreak. India reported its first ever Lumpy skin disease outbreak in August 2019. Since May 2022 regular outbreaks of LSD have affected cattle sector in the country with more than 22 states being affected. The current outbreak in India has a wide range of morbidity rates affecting more than 29 lakh cattle, and higher range of mortality rates among cattle killing around 2 lakh animals, comparing to the previous outbreak.
LSD Disease
It is a contagious epizootic disease and has affected numerous cattle herds across the country. In the acutely infected animal, there is an initial pyrexia, which may exceed 41°C and persist for 1 week. All the superficial lymph nodes become enlarged. In lactating cattle there is a marked reduction in milk yield. Lesions develop over the body, particularly on the head, neck, udder, scrotum, vulva and perineum between 7 and 19 days after virus inoculation. The characteristic integumentary lesions are multiple, well circumscribed to coalescing, 0.5–5 cm in diameter, firm, flat-topped papules and nodules. The nodules involve the dermis and epidermis, and may extend to the underlying subcutis and occasionally to the adjacent striated muscle. These nodules have a creamy grey to white colour on cut section, which may initially exude serum, but over the ensuing 2 weeks a cone-shaped central core or sequestrum of necrotic material/necrotic plug (“sit-fast”) may appear within the nodule. Complications included ulceration of nodules, sloughing, suppuration, maggot infestation, pneumonia, and mastitis.
Cause of the disease (Etiology)
LSD is caused by Lumpy skin disease virus (LSDV) which belongs to the family Poxviridae, subfamily Chordopoxviridae, and genus Capripoxvirus. The various strains of capripoxvirus responsible for the disease are antigenically indistinguishable from strains causing sheep pox and goat pox yet distinct at the genetic level.
Transmission
LSD is a vector borne disease and is transmitted by blood-feeding insects, such as certain species of flies and mosquitoes, or ticks. Transmission of LSD virus (LSDV) is thought to be predominantly by arthropods, natural contact transmission in the absence of vectors being inefficient. Mosquitoes (Aedes aegypti, Culex mirificens, Aedes natrionus), biting flies (Stomoxys calcitrans, Haematopota spp., Biomyia fasciata), Culicoides and ticks (Riphicephalus appendiculatus, Amblyomma hebraeum) are few arthropods responsible for transmission.
Direct contact with an infected animal is considered to play a minor role in the transmission of the virus. It is not known if transmission can occur via fomites, for example ingestion of feed and water contaminated with infected saliva, but the occurrence of newly detected recombinant field strains suggests these routes may be at play. Infected bulls can excrete the virus in their semen and transmission of LSD via infected semen has been demonstrated. There has been one report of placental transmission of LSD. Iatrogenic intra- or inter-herd transmission may occur via contaminated needles during vaccination or other injections if needles are not changed between animals or herds.
Susceptibility of hosts
Exotic (Bos taurus) and crossbred cattle are generally more susceptible to clinical disease than local cattle (Bos indicus); the Asian buffalo (Bubalus spp.) has also been reported to be susceptible. Virus has also been isolated from few wildlife species. LSDV is not zoonotic, so humans cannot get affected by the disease. There are no reports of LSD in sheep and goats or of their epidemiological involvement in the disease despite being kept in close proximity to cattle.
Sources of virus
Skin nodules, scabs and crusts contain relatively high amounts of LSDV. Virus can remain in these substance for upto a month. LSDV is also present in blood, saliva, ocular and nasal discharge, and semen of infected bulls. Shedding in semen may be prolonged approximately upto one and half month.
Virus is susceptible to higher temperatures and can survive for months to years at low temperatures (4°C degrees to –80°C). It is susceptible to chemicals or disinfectants including ether (20%), chloroform, formalin (1%), and some detergents, e.g. sodium dodecyl sulphate. LSDV is also susceptible to phenol (2%/15 minutes), sodium hypochlorite (2–3%), iodine compounds (1:33 dilution), Virkon® (2%), and quarternary ammonium compounds (0.5%).
Economic losses
The disease is of economic importance causing huge economic losses to farmers. It can cause a temporary reduction in milk production, temporary or permanent sterility in bulls, damage to hides and, occasionally, death. The economic implications for dairy farmers, have been exacerbated by the spread of misinformation through social media.
LSD outbreaks in various states of India resulted in an estimated economic loss of INR 18337.76 crores (USD 2217.26 million) in current outbreak. Milk production has decreased by 26% in affected areas. From September 2022, LSD has spread from 251 districts in 15 states to more than 22 states infecting more than 29.45 lakh cattle and causing death to more than 1.84 lakh animals.
Management
Treatment of affected animals, isolation of diseased animals, control of vector parasites, movement control, cleaning and disinfection is of utmost importance along with vaccination.
Generally it is considered that there is no specific treatment for LSD and usually symptomatic treatment is provided to affected cattle. Antibiotics are used against secondary bacterial infections. Antipyretics (paracetamol) are used for reducing fever, analgesics and antiinflammatory drugs (preferably non steroids) for minimising inflammation and pain, antihistamines for allergy, and ectoparasiticides against parasites. Through a letter D.O No. K-11053/69/2019-LH Dated August 31, 2022, Ministry of Fisheries, Animal Husbandry and Dairying, Govt. of India issued advisory/guidelines for control and treatment of LSD which included oral use of 0.1% Methylene Blue (MB) solution (1 gram of MB powder in 1 liter of water) at a dose of 300 ml at 8 hourly interval (thrice in a day) for 4 days for adult cows (of approximately 350 Kg body weight) and approximately half dose for calves. A milk withholding interval of 96 hours and a meat withdrawal interval of 14 days was recommended. Considering the gravity of situation and current severe LSD cases, use of other antiviral drugs (e.g. acyclovir) or drugs having antiviral activity (e.g. ivermectin) requires investigations under proper control.
The current preventive measure include vaccination, movement control of bovine animals, restriction with affected animals and persons dealing with such animals, quarantining, implementing biosecurity measures, vector control, disinfection and cleaning measures with above mentioned chemicals or disinfectants, and extension awareness and training programmes.
Ring vaccination in villages upto 5 km around the affected village is recommended. Cattle and buffaloes should be vaccinated with available Goat pox vaccine (cattle and buffalo at the age of 4 months and above through S/C route) with GTPV vaccine (Uttarkashi strain) as per the guidelines. However, affected animals should not be vaccinated. Vaccination of healthy cattle should be completed at the earliest with proper documentation in the high risk areas like borders of affected districts/states. Lumpi-ProVacind, a homologous live-attenuated LSD vaccine (Ranchi strain) has been developed by National Centre for Veterinary Type Culture, ICAR-National Research Centre on Equines (ICAR-NRCE), Hisar (Haryana), in collaboration with ICAR-Indian Veterinary Research Institute (IVRI), Izatnagar (UP) against LSD and is expected to be available soon for farmers.
Biosecurity measures
· Immediate isolation of sick animal from the healthy animals. Symptomatic treatment of affected animals may be carried out with all precautions and biosecurity measures. Feeding of liquid feed, soft feed and fodder is recommended
· Clinical surveillance against LSD in affected districts and around surrounding villages should be intensified. .
· The buffaloes should be kept separately till complete recovery of the affected animals, if reared together.
· Dis-infection of premises at regular intervals. Ecto-parasiticide should also be applied to healthy animals on the infected and on surrounding farms. Hygiene practices should be followed at the animal farm and by the people in area where animals are infected.
· The persons dealing with the infected animal should wear gloves and face mask and carry out hygienic and disinfection measures at all time.
· Care should be taken to report any unusual sickness of other animals to nearest veterinary Hospital/ Dispensary.
· Farms with affected animals should be visited regularly by the field veterinarians until all the cases are recovered. The veterinary staff should take all precautionary hygiene measures to avoid further spread of disease to other farms/households.
· In case mortality, carcass should be disposed of by deep burial method observing all hygienic measures.
· Cattle markets located within 10 km radius the epicentre of infection should be closed.
· Trade of live cattle, participation in fairs/shows should be banned immediately, upon confirmation of the disease in the affected areas.
· Semen from LSD affected animals should not be collected and processed for production and distribution.
Besides, administrative initiatives should be taken including formation of rapid response teams, trainers, monitoring committees, liaison with departments, and awareness programmes on disease prevention and control.
The opinions and observations are of the author and not the institute he works for.
Dr. Mohammad Iqbal Yatoo, Assistant Professor, FVSc and AH Shuhama, SKUAST-K. Principal Investigator of SERB, DST and BIRAC projects on infectious diseases of livestock