Explained | What is lumpy skin disease in cattle? Does it affect milk we consume?
The viral infection has killed nearly 75,000 cattle in India and spread to more than 10 States and UTs, hitting Rajasthan the worst
The story so far: The Mumbai Police have ordered the prohibition of cattle transportation in the city to prevent the spread of the lumpy skin disease. This means cattle cannot be moved out of the place they are being raised or transported to marketplaces. The order came into force on September 14 and will stay in place till October 13. The disease has killed 127 cattle in Maharashtra, having spread to 25 districts. The contagious viral infection has spread in cattle in more than 10 States and Union Territories so far. Prime Minister Narendra Modi informed last week that the Centre and States are working together to control the spread of the disease, which has emerged as a concern for the dairy sector.
What is the lumpy skin disease and how does it spread?
Lumpy skin disease is caused by the lumpy skin disease virus (LSDV), which belongs to the genus capripoxvirus, a part of the poxviridae family (smallpox and monkeypox viruses are also a part of the same family). The LSDV shares antigenic similarities with the sheeppox virus (SPPV) and the goatpox virus (GTPV) or is similar in the immune response to those viruses. It is not a zoonotic virus, meaning the disease cannot spread to humans. It is a contagious vector-borne disease spread by vectors like mosquitoes, some biting flies, and ticks and usually affects host animals like cows and water buffaloes. According to the United Nations Food and Agriculture Organisation (FAO), infected animals shed the virus through oral and nasal secretions which may contaminate common feeding and water troughs. Thus, the disease can either spread through direct contact with the vectors or through contaminated fodder and water. Studies have also shown that it can spread through animal semen during artificial insemination.
LSD affects the lymph nodes of the infected animal, causing the nodes to enlarge and appear like lumps on the skin, which is where it derives its name from. The cutaneous nodules, 2–5 cm in diameter, appear on the infected cattle’s head, neck, limbs, udder, genitalia, and perineum. The nodules may later turn into ulcers and eventually develop scabs over the skin. The other symptoms include high fever, sharp drop in milk yield, discharge from the eyes and nose, salivation, loss of appetite, depression, damaged hides, emaciation (thinness or weakness) of animals, infertility and abortions. The incubation period or the time between infection and symptoms is about 28 days according to the FAO, and 4 to 14 days according to some other estimates.
The morbidity of the disease varies between two to 45% and mortality or rate of death is less than 10%, however, the reported mortality of the current outbreak in India is up to 15%, particularly in cases being reported in the western part (Rajasthan) of the country.
What is the geographical distribution and how did it spread to India?
The disease was first observed in Zambia in 1929, subsequently spreading to most African countries extensively, followed by West Asia, Southeastern Europe, and Central Asia, and more recently spreading to South Asia and China in 2019. As per the FAO, the LSD disease is currently endemic in several countries across Africa, parts of West Asia (Iraq, Saudi Arabia, Syrian Arab Republic), and Turkey.