Lumpy Skin Disease (LSD): An Emerging Transboundary Viral Disease
Dr. Ragini Mishra1, Dr. Vivek Gairola1 and, Dr. Sonam Bhardwaj1
ICAR-IVRI, Izatnagar-243122, Bareilly (U.P.)
Introduction
Lumpy skin disease (LSD) is an infectious illness of cattle which is characterized by eruptive lesions, greatly reduced milk production, poor growth, reduced fertility, sometimes abortion and rarely death. It is caused by the lumpy skin disease virus (LSDV), belongs to the genus Capripoxvirus in the Poxviridae family and shows close antigenic relationship with sheep and goat pox virus. LSDV can be distinguished by their distinctive brick-shaped appearance using electron microscopy. It is an enveloped DNA virus measuring approximately 294nm × 262nm in size, with a 151-kbp genome. The disease is notifiable by OIE, as it can spread quickly across borders (transboundary) and results in significant losses in the production of cattle. Zambia was the first nation to suffer a lumpy skin disease pandemic in 1929. LSD has recently been identified as a severe concern to cattle in Southeast Asia. The first country on the Asian continent to report an LSD incidence was Bangladesh. According to the OIE, India has seen three significant LSD epidemics. The first one was found in five coastal districts of the state of Odisha in August 2019. From August to December 2019, LSD outbreaks followed in various parts of Odisha and the neighbouring state West Bengal. According to latest information provided by the Ministry of Fisheries, Animal Husbandry, and Dairy, the lumpy skin disease has infected more than 20 lakhs animals and now it has spread to 251 districts across 15 states as of 23 September 2022. Cases have been documented in Rajasthan, Gujarat, Punjab, Haryana, Uttar Pradesh, Jammu and Kashmir, Himachal Pradesh, Madhya Pradesh, Uttarakhand, Maharashtra, Goa and Andaman and Nicobar Islands.
Transmission
LSD is a vector-borne disease that affects cattle and water buffalo. It is transmitted by a variety of blood-feeding and biting arthropods, including Stomoxys calcitrans and Biomyia fasciata. Additionally, Ixodid hard ticks like Rhipicephalus appendiculatus are also capable of mechanically transmitting LSDV to other animals. Less commonly, LSDV can be directly transmitted through skin lesions, saliva, and respiratory secretions. All of these insects’ contributions to LSD transmission need yet to be investigated in laboratory setting and in the field. All age groups of cattle of both the sexes are vulnerable to LSD infection; however, exotic cattle breeds are more sensitive than native cattle, and younger animals exhibit more severe illness than older ones.
Symptoms
The incubation period of the disease ranges from 2-5 weeks. The illness takes about two to five weeks to fully develop. The virus’s inoculation dosage, method, and host susceptibility all affect the disease’s severity. LSD may present with acute, subacute, or inapparent clinical presentations and can be divided into moderate and severe types depending on the quantity of lumps (nodules), the frequency of problems, overall dose of the inoculum, the host’s susceptibility, and the number of vector populations. When compared to native breeds, clinical indications brought on by LSDV in high-yielding dairy cattle like Holstein Friesian were observed to be significantly more severe. The initial sign of the illness is fever (40-41.5°C) along with lachrymation, inappetence, depression, and lethargy. Following experimental inoculation, fever appears roughly 5 days later and lasts for several days. Following the commencement of fever, skin lesions described as “nodules” start to appear. The typical symptoms of LSD include high body temperatures and skin nodules (10–50 mm in diameter) that often necrotize and affect the head, internal ear, eyelids, nose, neck, udder, limbs, perineum, genitalia, and other areas.
Treatment and Preparedness
No precise antiviral drugs are available for the treatment of LSD till now, thus prevention through vaccination is the only effective and efficient way of restraining the disease. Strong antibiotic therapy to avoid secondary bacterial infection is recommended. The best protection comes from prophylactic vaccination of the entire cattle population, carried out well in advance in at-risk areas. Movements of cattle inside the country and across borders should be strictly controlled or totally banned. Authorized cattle movements should be accompanied by a veterinary certificate including all data concerning the animals’ origins, and animal health guarantees. In affected villages, cattle herds should be kept separate from other herds by avoiding communal grazing, if possible without animal welfare issues. However, in some cases the whole village forms a single epidemiological unit and then the feasibility of separation has to be evaluated on a case-by-case basis. Movements of vaccinated animals can be allowed within a restricted zone within a country after it has been established that full immunity has been provided by a vaccine with proven efficacy (28 days after vaccination). Cattle should be treated regularly with insect repellents to minimize the risk of vector transmission of the disease. This measure cannot fully prevent transmission but may reduce the risk. Lumpy skin disease virus is very stable and survives well in extremely cold and dry environments within the pH range 6.3-8.3. Infected animals shed scabs from skin lesions. Inside the scabs, the virus may remain infectious for several months. Thorough cleaning and disinfection with appropriate products should be performed on affected farms, trucks, premises and potentially contaminated environments. Personnel should also undergo disinfection.
Currently available vaccines
Only live vaccines are currently available against LSDV. No Differentiation of Infected from Vaccinated Animals (DIVA) vaccines have been developed against LSD. Annual vaccination is recommended in affected countries, and harmonized vaccination campaigns across regions provide the best protection. Calves from naive mothers should be vaccinated at any age, while calves from vaccinated or naturally infected mothers should be vaccinated at 3-6 months of age. Regional harmonized vaccinations are recommended and should be carried out before large-scale movements of cattle, for example prior to the onset of seasonal grazing. Live, attenuated LSDV vaccines may cause mild adverse reactions in cattle. Local reaction at the vaccination site is common and acceptable as it shows that the attenuated vaccine virus is replicating and producing good protection. Currently, there are three vaccine producers manufacturing attenuated LSDV vaccines. Live, attenuated LSDV vaccines provide good protection in cattle if 80 percent vaccination coverage is attained. In practice, all animals need to be vaccinated including small calves and pregnant cows. Regional vaccination campaigns should be preferred to ring vaccination. Sheep pox virus vaccines have been used in cattle against LSDV in those regions where LSD and SPP are both present. Commercially available GTPV Gorgan strain has been demonstrated to provide equal protection against LSD as the LSDV vaccines. Recently Lumpi-ProVacInd, an indigenously made homologous, live attenuated vaccine for cattle has been developed by National Research Centre (NRC) on equines, Haryana in collaboration with the Indian Veterinary Research Institute (IVRI), Bareilly using a LSDV strain isolated from an affected cow in Jharkhand. The process is now underway to ensure the commercial availability of India’s indigenous vaccine to combat Lumpy skin disease.
Dr. Ragini Mishra1 (Division of Veterinary Microbiology)
Dr. Vivek Gairola1 (Division of Veterinary Microbiology)
Dr. Sonam Bhardwaj1 (Division of Livestock Production and Management)
