DR SHABIR AHMAD BHAT
DR PERVAIZ AHMAD DAR
India is home to the largest livestock population in the world, including cattle, buffalo, sheep and goat constituting 31 percent of the world animal population. The livestock sector contributes 4.11% of GDP and plays an important role in the national economy. In India, the livestock sector has continuously been growing at a compound annual growth rate (CAGR) of 7.93% (at constant price) from 2014-15 to 2020-21, which is above the CAGR of manufacturing at 4.93% and services at 4.82% and agriculture (crop sector) at 2.05%. As reported in the economic survey 2021-2022, dairy is the single largest agricultural commodity employing more than 8 crore farmers directly. India is ranked first in milk production, contributing 23 percent of global milk production. Milk production in the country has grown at a compound annual growth rate of about 6.2 % to reach 209.96 million tons in 2020-21 from 146.31 million tons in 2014-15. Currently, a new contagious disease known as lumpy skin disease (LSD) is emerging a major threat to the dairy sector in the country. The disease has a potential to reduce milk productivity and perpetuates the vicious cycle of hunger, poverty, and malnutrition.
LSD is a viral disease of cattle and buffalo caused by a virus closely related to sheep-pox virus and goat-pox virus. LSD is a notifiable disease according to the World Animal Health Organization (OIE) due to its potential of rapid spread and severe economic consequences. The death rate is usually around 5 % to 10%, whereas the morbidity rate ranges 5% to 45%. Although the disease is not contagious to humans, it can jeopardize the livelihoods of dairy farmers. Affected nations have suffered significant economic losses as a result of the LSD. Due to a high fever and subsequent mastitis, the disease dramatically reduces milk production by 10% to 85%. Other consequences of the disease include damaged hides, a decline in the growth rate of beef cattle, temporary or permanent infertility, abortion, treatment and vaccination costs, and the death of infected animals.
LSD was first detected in Zambia in 1929 and since then the disease spread to other sub-Saharan Africa countries. Outside Africa the disease has been gradually spreading since 1990. In Asia and the Pacific the disease was first reported in 2019 and has since spread across the region including India. Skin lesions are considered to be the primary sources of infection because the virus can survive for a long time in lesions or scabs. The virus is also excreted through the blood, milk, saliva, semen, nasal, and lachrymal discharges. The virus spread mainly occurs through mechanical transmission by insect vectors such as flies, mosquitoes, and ticks. Also, communal grazing and watering have been linked to higher rates of LSD, most likely as a result of the increased likelihood of mosquitoes and other insects transmitting the virus. Transhumance and other reasons for animal movements have also been associated with an increased risk of the outbreaks. Other risk factors associated with the spread of LSD include a warm and humid climate, a condition supporting an abundance of vector populations, such as those seen after seasonal rains. LSDV can persist in the environment for extended periods of time at room temperature, particularly in dried scabs. The virus reportedly survives in dried crusts for up to 35 days, and in air-dried hides for at least 18 days. The virus can be destroyed by disinfectants like Phenol, Chloroform, Detergents, and Bleach.
The line of treatment for LSD is only symptomatic and is targeted at preventing secondary bacterial complications using a combination of antimicrobials, anti-inflammatory, supportive therapy, and antiseptic solutions. Awareness among livestock farmers regarding the preventive measures to be adopted at individual and village level regarding control and eradication of the disease should be the top priority in any control program. In the event of an LSDV intrusion into a previously free area, control strategies may include a strict quarantine; restrictions on animal movement; reactive vaccination; culling of affected animals; safe disposal of carcasses; cleaning and disinfection of facilities; and insect control. In endemic areas, vaccination, along with travel restrictions and animal culling, can efficiently control the disease. The control and eradication of LSD can be achieved by stamping out policy, slaughter campaigns and vaccination. In stamping out policy, all the affected animals and in-contact animals are killed and the farmers are compensated by the government. Since stamping out or slaughter campaigns are not permitted in India, vaccination is the only option with us for effectively controlling LSD in the country.
The majority of currently available vaccines are live attenuated and contain either LSDV (homologous) or sheep and goat pox strains (heterologous). In India currently, heterologous live-attenuated vaccines, especially goat pox vaccine, are being used to immunize cattle against LSD. However, homologous vaccines provide good protection compared to heterologous vaccines against the virulent field strains. Also, it is not advisable to use these heterologous vaccines in goat pox or sheep pox-free regions. One of the major limitations in using live attenuated vaccines is the risk of recombination between virulent field strains and vaccine strains. Since the LSD virus is a DNA virus, the possibility of recombination is low.
India is a world leader in vaccine manufacturing capacity as evident during the COVID-19 pandemic. The infrastructure and the technology available with the country can be used for the large-scale production of vaccines against LSD. Recently, ICAR-National Research Center on Equines (ICAR-NRCE), Hisar (Haryana), in collaboration with ICAR-Indian Veterinary Research Institute (IVRI), Izatnagar, Uttar Pradesh, has developed a homologous live-attenuated LSD vaccine “Lumpi-ProVacInd’’ for the prevention and control of LSD. To control LSD in the country, the need of the hour is to commercialize this indigenous vaccine and expand its production. Till that time, control strategies including use of goat pox vaccine, restriction of animal movement, isolation of infected animals, monitoring of stray animals, and safe disposal of carcasses should be fully implemented.
Dr Shabir Ahmad Bhat (Virologist), Presently deployed at IAH & BP, Zakura, DAHK
Dr Pervaiz Ahmad Dar, Scientist, Krishi Vigyan Kendra, Ganderbal, SKUAST-K
Disclaimer: The views and opinions expressed in this article are the personal opinions of the author. The facts, analysis, assumptions and perspective appearing in the article do not reflect the views of GK.