Lumpy skin disease outbreak: challenges and strategies for control and eradication

Lumpy skin disease (LSD) is surging across the country.

A notifiable vector-borne disease in cattle and domestic water buffalo caused by lumpy skin disease virus (LSDV) belonging to the family Poxviridae, the disease is an eruptive, occasionally fatal for cattle characterised by nodules on the skin and other parts of the body, according to Central Veterinary Laboratory (CVL).

The animal disease, first identified in Nepal in June 2020 at Sundarharaicha (Morang, Koshi Province), infected 3,301 cattle across 16 districts killing 13 cattle then till 2022. The occurrence can be attributed to the continuous influx of unauthorised cattle migrations through long porous borders from India to eastern Nepal.

It re-emerged in March 2023 infecting 682,080 cattle so far — 25,408 dead, 247,497 infected, while 409,175 cattle have received treatment, says the Department of Livestock Services LSD press release. A total of 172,128 cattle have been vaccinated out of 737,000 imported vaccines that were dispersed in all seven provinces.

As per Economic Survey 2021/22, the number of cattle and buffaloes reared in the country stands at 7,497,030 and 5,155,966 respectively.

On July 14, Dev Raj Ghimire, Speaker of the House of Representatives, issued a ruling seeking clarification with the government about the preventive measures to curtail the spread of the disease.

The first lumpy skin disease epidemic was discovered in 1929 in Zambia which quickly spread throughout Africa. In July 2019, the disease first appeared in South Asia, and by July 2020, it had spread quickly throughout Southeast Asia.

The disease is primarily transmitted through blood-feeding insects, such as mosquitoes, flies, midges, and ticks.

The virus can also spread through direct contact with the saliva and nasal secretions of infected animals, and indirect contact via contaminants of the owner of the animals and items (vehicle, equipment, etc.), contaminated feed and water, and artificial insemination.

The LSDV can survive in skin nodules for a month and in air-dried skins for at least three weeks.

The clinical signs of the disease include — fever (40°C to 41.5°C), flow of tears, nasal discharge, hypersalivation, lethargy, anorexia, sharp decrease in milk yield, necrotic plaques in oral and nasal mucous membranes, and then the development of distinctive nodular lesions on the head, neck, chest, abdomen, perineum, genitalia, udder, and limbs. In addition, these lesions may develop into the muscular layer.

Economic impact

Lumpy skin disease can cause significant direct losses due to death, decreased milk production, damaged hides, poor growth, decreased draught power capability, and reproductive issues such as abortions, infertility, and a lack of semen for artificial insemination. 

In India, a net economic loss of USD 2,217.26 million was estimated when bovines were infected with the disease.

According to estimates, the direct losses of livestock and production caused by the disease in South, East, and Southeast Asian countries could reach USD 1.45 billion.

As per the World Food and Agriculture — Statistical Yearbook 2022, in 2020, Asia shared 42.2% (374,075.8 kilotons) of global milk production and 22.6% (15,310 kilotons) of global cattle meat production.

According to the Economic Survey 2021/22, Nepal produced 1739.66 metric tons of milk and 127,167 metric tons of buffalo meat by the mid-March of FY 2021/22. The country exported Rs 18 million worth of meat and Rs 53 million worth of dairy and livestock food products.

When the response is taken into account, the costs of the outbreak investigation, eradication of the disease, compensation, cleaning and disinfection, treatment, immunisation, surveillance, and awareness campaigns can significantly increase the short-term costs associated with the level of LSD spread.

Trade embargoes or mobility limitations in affected countries place an economic strain on the cattle industry, severely impacting all actors along the value chain.

The disease may also have an influence that transcends beyond the economic sphere. Smallholders that depend on milk production for their own food security and for the provision of cash may face threats to their way of life due to skin disease. Compared to eggs or meat, dairy products make a bigger difference in preventing stunting. According to World Food and Agriculture, up to 50% of the milk produced is used for household consumption in some areas of Asia, meaning the disease may have a profound indirect impact on individual health.

Prevention

The lack of well-regulated and biosecure livestock production and market chains, as well as a lack of traceability and certification procedures, can hasten the spread of lumpy skin disease both domestically and internationally.

The control and eradication procedures must be tailored to local conditions in each country and region where the disease outbreaks, taking into account the size of the susceptible cattle population and local cattle husbandry practices.

Early outbreaks can be addressed through biosafety, equipment cleanliness, and quarantining the animal population.

The primary carriers of the disease — blood-sucking insects — are responsible for its rapid spread; as a result, constant use of pesticides to sanitise the area and eradicate vectors, removing dung, and destroying breeding grounds are advised.

To stop fly infestation and subsequent infections, animals are typically treated with supportive therapy for their local wounds. For more severe disease scenarios, systemic antibiotics may be used.

Effective treatment against lumpy skin disease has not been recognised yet. Nevertheless, vaccination of cattle is the best option for controlling the spread of skin disease. A live attenuated vaccine is commercially available for disease eradication. Sheep pox vaccine from SPPV and GTPV is used for control in countries with high outbreaks.

The Nepal government has recommended the use of the Neethling strain vaccine against the ongoing outbreak.

The recurring annual immunisation for several years after the discontinuation of clinical cases was the key to achieving control and eradication of the disease in Israel and the Balkan region of Europe.

Similarly, veterinary education for livestock workers — to be able to recognise diseases quickly and stop their spread — is pertinent.