Evolution of Lumpy Skin Disease virus

Evolution of Lumpy Skin Disease virus

Subject : Science and technology

Context:

• The virus that causes Lumpy Skin Disease (LSD) primarily affects cattle. The LSD virus (LSDV) is a poxvirus of the genus It was first identified after an outbreak in Zambia in 1929. Prior to the 1980s, repeated LSD outbreaks were exclusive to the African continent. Israel reported the first cases of HIV outside of Africa in 1989.
• It is not a zoonotic disease, meaning the disease cannot spread to humans.
• It is a contagious vector borne disease spread by vectors like mosquitoes, some butter flies and usually affects the host animal like cow and water buffaloes.
• It primarily consists of fever, fluid excretion from eyes and nose, dribbling of saliva from the mouth and blisters on the body. The animal stops eating and faces problems while chewing or eating, resulting in a sharp drop in milk production. However it is safe to consume milk from the infected cattle.

Recombinant viruses

• In Russia,epidemics of LSD were reported between 2015 and The virus genomes isolated in 2015 and 2016 were similar to those from preceding years. In spite of the introduction of homologous (attenuated) LSDV vaccination in 2016, the outbreak continued, and in 2017 vaccine-like isolates were obtained from infected cattle. By 2018, all LSDV field isolates in Russia had been replaced by viruses expressing genetic signatures of the LSDV vaccine, suggesting that the 2017-2019 LSD outbreak in Russia  was caused by an unique LSDV recombinant strain.
• In 2019, LSDV infections were first confirmed in China following outbreaks in multiple regions. Another vaccine-recombinant strain with 25 recombination events between a field strain and a vaccination strain was identified by whole-genome sequencing. However, the strain from China was notably divergent from the vaccine-recombinants discovered in Russia, indicating that a virulent recombinant of LSDV of unknown origin was responsible for the 2019 and 2020 LSD outbreaks in China.
• In cells co-infected by viruses of the same or a different genus, recombination events are mediated by the poxvirus DNA polymerases. Therefore, recombination of pathogenic and vaccine strains is probable when an infected animal is immunised or when infection develops in the pre-immune phase following vaccination. Prior to the widespread distribution of homologous attenuated vaccines, utmost vigilance and genetic follow-up studies are necessary.
• Additionally, there is evidence for existence of an additional mutation in two samples from the same animal found in India and the high number of mutations suggest that LSDV may be able to rapidly evolve within its host.
• Attenuated Vaccine: Attenuated vaccines can be made in several different ways. Some of the most common methods involve passing the disease-causing virus through a series of cell cultures or animal embryos (typically chick embryos). When the resulting vaccine virus is given to a human, it will be unable to replicate enough to cause illness, but will still provoke an immune response that can protect against future infection.