What is Lumpy Virus?
Lumpy Virus is a virus of the family Poxviridae, also known as Neethling virus, species of CAPRIPOXVIRUS causing a cattle skin disease.
What is Lumpy skin Disease?
Lumpy skin disease (LSD) is a viral disease of cattle caused by lumpy skin disease virus (LSDV).
Lumpy Skin Disease: Over 1.5 lakh cattle died in India last year, nearly half of it in Rajasthan 2022
Resistance to physical and chemical action
Temperature: Susceptible to 55°C/2 hours, 65°C/30 minutes. Can be recovered from skin nodules kept at –80°C for 10 years and infected tissue culture fluid stored at 4°C for 6 months.
pH: Susceptible to alkaline or acid pH. No significant reduction in titre when held at
pH 6.6–8.6 for 5 days at 37°C.
Chemicals/Disinfectants: Susceptible to ether (20%), chloroform, formalin (1%), and some detergents,e.g. sodium dodecyl sulphate.
Susceptible to phenol (2%/15 minutes), sodium hypochlorite (2–3%), iodine compounds (1:33 dilution), Virkon® (2%), quarternary ammonium compounds(0.5%).
Survival: LSDV is remarkably stable, surviving for long periods at ambient temperature,especially in dried scabs. LSDV is very resistant to inactivation, surviving in necrotic skin nodules for up to 33 days or longer, desiccated crusts for up to 35 days, and at least 18 days in air-dried hides. It can remain viable for long periods in the environment. The virus is susceptible to sunlight and detergents containing lipid solvents, but in dark environmental conditions, such as contaminated animal sheds, it can persist for many months.
EPIDEMIOLOGY
• Morbidity rate varies between 10 and 20%.
• Mortality rates of 1 to 5% are considered usual.
Hosts
• LSDV is highly host specific and causes diseases only in cattle (Bos indicus and B. taurus) and water buffalo (Bubalus bubalis). There is evidence from a study in Ethiopia of differential breed susceptibility to LSD, with Holstein Friesian or crossbred cattle exhibiting higher morbidity and mortality due to LSD when compared with local zebu cattle
• Extensive serological surveys of wild ruminant species in Africa have not identified a wildlife reservoir of LSDV. The virus appears to be highly host specific.
• LSDV is not zoonotic.
Transmission
• The principal means of transmission is believed to be by arthropod vector. Though no specific vector has been identified to date, mosquitoes (e.g. Culex mirificens and Aedes natrionus), biting flies (e.g.Stomoxys calcitrans and Biomyia fasciata) and male ticks (Riphicephalus appendiculatus and Amblyomma hebraeum) could play a role in the transmission of the virus. The importance of different arthropod vectors is likely to vary in different areas depending on the abundance and feeding behaviour of the vector.
• Infected bulls can excrete the virus in the semen, however transmission of LSD via infected semen has not been demonstrated.
• It is not known if transmission can occur via fomites, for example ingestion of feed and water contaminated with infected saliva.
• Animals can be infected experimentally by inoculation with material from cutaneous nodules or blood.
•Direct contact is considered to play a minor, if any, role in the transmission of the virus.
DIAGNOSIS
Under experimental conditions, following the virus inoculation, the incubation period is between 4 and 14 days. For the Terrestrial Manual purposes, the incubation period is 28 days.
Clinical diagnosis
• Fever that may exceed 41°C.
• Marked reduction in milk yield in lactating cattle.
• Depression, anorexia and emaciation.
• Rhinitis, conjunctivitis and excessive salivation.
• Enlarged superficial lymph nodes
• Cutaneous nodules of 2–5 cm in diameter develop, particularly on the head, neck, limbs, udder,genitalia and perineum within 48 hours of onset of the febrile reaction. These nodules are Circumscribed, firm, round and raised, and involve the skin, subcutaneous tissue and sometimes even the underlying muscles.
• Large nodules may become necrotic and eventually fibrotic and persist for several months (“sit-fasts”); the scars may remain indefinitely. Small nodules may resolve spontaneously without consequences.
• Myiasis of the nodules may occur
• Vesicles, erosions and ulcers may develop in the mucous membranes of the mouth and alimentary tract and in the trachea and lungs.
• Limbs and other ventral parts of the body, such as the dewlap, brisket, scrotum and vulva, may be oedematous, causing the animal to be reluctant to move.
• Bulls may become permanently or temporarily infertile.
• Pregnant cows may abort and be in anoestrus for several months.
Laboratory diagnosis
Samples
Identification of the agent
• Polymerase chain reaction (PCR) is the least expensive and quickest method for detection of LSDV.Skin nodules and scabs, saliva, nasal secretions, and blood are suitable samples for PCR detection of LSDV.
• Virus isolation (VI) followed by PCR to confirm the virus identity takes longer and is more expensive but has the advantage of demonstrating the presence of live virus in the sample.
• Electron microscopy can be used to identify the classic poxvirus virion but cannot differentiate to genus or species level.
Serological tests
It is not possible to distinguish the three viruses in the Capripoxvirus genus (Sheeppox virus, Goatpox virus and LSD) using serological techniques.
• Virus neutralisation: this is currently the gold standard test for the detection of antibodies raised against capripoxviruses.
• Western blot: highly sensitive and specific but expensive and difficult to perform.
• Capripoxvirus antibody enzyme-linked immunosorbent assay: new commercial kits for detection of capripoxvirus antibodies are currently being developed and released on to the market.
PREVENTION AND CONTROL
Sanitary prophylaxis
•Free countries:
# Import restrictions on domestic cattle and water buffaloes, and selected products from these animals.
# Surveillance measures to detect LSD are recommended over a distance of at least 20 kilometres from an infected country or zone
• Infected countries:
# Control of LSD depends on restriction of movement of cattle in infected regions, removal of clinically affected animals, and vaccination. Movement restrictions and removal of affected animals alone without vaccination are usually not effective.
# Proper disposal of dead animals (e.g. incineration), and cleaning and disinfection of premises and implements are recommended for LSD.
# There is currently no evidence of the efficacy of vector control in preventing disease
# See OIE Terrestrial Animal Health Code for regulations covering the recovery of LSD-free status of a country or zone.
Medical prophylaxis
• “Homologous” LSDV live attenuated vaccine strain for example “Neethling” LSD strain
• “Heterologous” sheeppox or goatpox virus live attenuated vaccine strain.
• A local reaction at the site of inoculation, as well as fever and reduction in milk yield, may follow vaccination with live, attenuated capripox virus.
• Currently, no new generation recombinant capripox vaccines are commercially available.
• Secondary infections in the skin may be treated with Non-Steroidal Anti-Inflammatories (NSAIDs) and also antibiotics (topical +/- injectable) when appropriate.
