The lumpy skin disease virus (LSD), which has killed at least 50,000 cattle in India this year, may be structurally different from the version of the virus that was circulating in India in 2019, raising questions about whether the new vaccine , which is developed to protect cattle, can adequately protect .
Scientists from the Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology (CSIR-IGIB) and the State Disease Diagnostic Center, Jaipur, analyzed five animals showing symptoms of the disease and compared the genomes of the virus extracted from them. Six genomes (there were multiple genomes from a single animal) showed that it bore “little resemblance to global genomes” compared to genetic sequences from previous outbreaks of the disease.
Analysis of the genomes revealed 177 unique variants, none of which were found in four genome sequences from India associated with the 2019 outbreak of the disease and deposited in GenBank, a popular database.
“Analysis of the virus sequences suggests that the genomes of the 2022 outbreak harbor a large number of genetic variations compared to the reference genome, forming a clear lineage,” said authors Lenin Bhatt, Rahul C. Bhoyar, Bani Jolly, Ravi Israni and Harie Vignesh , say Vinod Scaria, Sridhar Sivasubbu, in their newspaper. The study appears on the preprint server Bioarxiv and has yet to be reviewed by experts.
This is significant because Lumpi-ProVacInd, a vaccine developed by the Indian Veterinary Research Institute and the Indian Council of Agricultural Research (ICAR) National Research Center on Equines, is based on LSD virus samples from ranchi cattle collected by outbreak in 2019. However, experimental trials conducted on animals infected with the vaccine during the ongoing outbreak in 2022 have shown encouraging results, ICAR and the Department of Agriculture have said.
The vaccine is a live, attenuated or weakened version of the virus, which is expected to stimulate the immune system and protect against possible infection when injected into animals. Currently, the only available vaccines against the disease are goatpox and sheeppox vaccines, which are related to the LSD virus.
“That’s the million-dollar question of what the implications of this genome sequencing mean for the vaccine,” said CSIR-IGIB’s Sridhar Sivasubbu, one of the scientists involved in the genome sequencing study.
That specific study, he said, shed no light because too few animals were tested and only a broader sample of viral genomes spanning multiple states could answer whether the variants identified and analyzed in Rajasthan as part of the study were widespread in India were common.
Another concern raised by the IGIB study is that one of the animals appeared to have two different variants of the LSD virus when the virus was extracted from both its nose and skin, suggesting that there is a difference the virus appeared to be able to develop inside a single host. This again speaks to the increased infectivity of the LSD virus in 2022 compared to 2019.
Lumpy skin disease is a contagious viral disease spread among cattle by mosquitoes, flies, lice and wasps through direct contact and through contaminated feed and water. The disease causes fever and skin lumps and can be fatal.
Symptoms include skin nodules about an inch to two inches in size, high fever, decreased milk production, loss of appetite, and watery eyes. The center recently said about 57,000 cattle have died so far from the disease, which has spread to Gujarat, Rajasthan, Punjab, Haryana, Uttar Pradesh and Andhra Pradesh.
The disease has raised concerns about its impact on the dairy business. With around 210 million tons annually, India is the largest milk producer in the world.