Lumpy Skin Disease
Dr. Warsha Chaudhary1 and Dr Hemant Fagna2
PhD SCHOLAR , Department of Veterinary Medicine1, Department of Veterinary Surgery and Radiology2
Post Graduate Institute of Veterinary Education and Research, Jaipur
Abstract
Lumpy Skin Disease (LSD) is a highly contagious viral disease affecting cattle, caused by the Lumpy Skin Disease Virus (LSDV), a member of the Capripoxvirus genus under the Poxviridae family. LSD is characterized by fever, enlarged lymph nodes, and the appearance of nodules on the skin and mucous membranes. This results in reduced milk production, potential abortion in pregnant cows, and sterility in bulls, leading to significant economic losses. Initially endemic to Africa, LSD has spread rapidly across Europe and Asia since 2012, with severe outbreaks reported in India, particularly in 2022. Transmission primarily occurs through blood-feeding vectors like flies, mosquitoes, and ticks, as well as through direct contact and contaminated semen. Clinical symptoms include fever, skin nodules, ocular discharge, and severe complications such as pneumonia and mastitis. Diagnosis relies on clinical signs, supported by laboratory tests like PCR and ELISA. While no specific antiviral treatment exists, supportive care and the use of live attenuated vaccines, particularly based on the Neethling strain, are the primary methods of control. Effective management strategies also include vector control, movement restrictions, and biosecurity measures to prevent the spread of the virus.
Introduction–
Lumpy skin disease (LSD) is a notifiable disease caused by the LSD virus (LSDV), which belongs to the Capripoxvirus genus under the family Poxviridae (Gupta et al., 2020). The disease in cattle is characterized by fever, enlargement of lymph nodes, edematous swelling of the legs, and the development of multiple nodules on the body surface, also be found on the mucosae of the respiratory and digestive tracts, as well as on skeletal muscles. The affected animals undergo a drastic reduction in milk production, pregnant cattle may abort, and bulls may become sterile. The recovered animals tend to have permanent damage to their skin, lowering the commercial value of their hide. The LSD results in high morbidity and mortality in cattle which serve as the principal host for LSDV infection.
Epidemiology
LSD was confined to African countries for many decades. Since 2012, LSD has spread from Africa into several countries in Europe. In Asia, it was first reported in 2019 in north-west China, Bangladesh and India (Kumar et al., 2021; Roche et al., 2020; Tran et al., 2021). Since 2019, LSD has been reported in most Asian countries and has caused economic devastation to the livestock industry. The LSD outbreaks in 2022 in Western part of India (Gujarat/Rajasthan) have been highly lethal.
LSD is primarily a disease of cattle. Buffaloes are relatively resistant to LSD, however, a mild illness can occasionally be observed. The LSD results in high morbidity and mortality in cattle which serve as the principal host for LSDV infection (Kumar et al., 2023a). Recently evidence of LSDV infection has been observed in several other domestic/wild animals, such as camels (Kumar et al., 2023a), giraffes (Dao et al., 2022), Arabian oryxes (Greth et al., 1992) and African buffaloes (Fagbo et al., 2014; Hedger and Hamblin, 1983). However, the disease in these unnatural hosts is usually mild in nature (Dao et al., 2022; Fagbo et al., 2014; Greth et al., 1992; Hedger and Hamblin, 1983; Kumar et al., 2023a; Kumar and Tripathi, 2022).
Causative Agents
Lumpy skin disease (LSD) is a viral infection caused by the lumpy skin disease virus (LSDV) of the capripox virus genus in the poxviridae family. LSD virus is identical to sheep pox virus (SPV), and goat pox viruses (GPV) which are closely related although differ phyto-genetically. LSD virus is also known as Neethling virus.
Transmission
During the summer, LSD is transmitted by blood-feeding insects. The virus is present in several tick organs, including the salivary glands, mid gut, and hemocytes, hard ticks play a part in viral transmission.
- The virus primarily transmitted by arthropod vectors like common biting flies (Stomoxys and Biomjie), mosquitoes (Aedes and Culex) and some ticks (Rhiphicephalus appendiculatus and Ambylomma hebraem) are mainly responsible for its spread. The multiplication of vectors during the monsoon months causes faster spread of the disease (Sevik and Dogan 2017).
- The virus transmission occurs through the movement of animals or unrestricted movement of stray animals. Infected animals excrete viruses in saliva as well as in nasal and ocular discharges. It can remain in saliva for 11 days (after the development of fever). The virus can be found in skin nodules even after 33 days of infection.
The virus also persists in the semen of infected bulls, so natural mating and artificial insemination can also spread the disease so the virus has been found in bovine semen using PCR and viral isolation techniques (Annandale et al 2014).
Predisposing factors
warm and humid climate, herd size, vector populations, distance to the water bodies, migration of herd, transport of infected animals into disease-free areas, Cattle markets, All breeds and stages of the animals, as well as both sexes, are susceptible to the LSD.
Clinical sign
Fever, nasal discharge, salivation, lachrymation, aberrant lymph nodes, reduced milk production, and weight loss are some of the clinical signs of LSDV.
The neck, tail, and legs may also develop 2–7 cm skin nodules shortly after a fever 9Beard,2016). While there were no nodules seen on the skin of the foetus.
It can result in serious illnesses such keratitis, diarrhoea, lameness, pneumonia, mastitis, and myiasis (Sevik and Dogan 2017).
Blindness occurs in worst cases due to ulcerative lesions in cornea in one or both eyes.
Pregnant cows may abort and remain in anoestrous for several months.
Diagnosis
While clinical characteristics like skin nodules are sufficient for LSDV diagnosis, real-time PCR and conventional techniques can be employed for confirmation. It is possible to build a real-time methodology to distinguish LSDV from sheep and goat poxviruses (Lamien et al 2011).
LSDV and vaccination strains may also be distinguished using the Restricted Fragment Length Polymorphism method (Menasherow et al 2014).
Although molecular approaches are more accurate and quick, other diagnostic methods can also be used to identify viruses, including viral neutralization, electron microscopy, virus isolation, and serological techniques like ELISA and fast antibody or antigen.
Although though western blotting is extremely sensitive and specific, the viral neutralization is only verified using serological methods, which are employed for LSDV detection [Babiuk et al 2008].
Differential Diagnosis
LSD can be confused with many diseases like Pseudo-lumpy-skin disease, Bovine viral diarrhoea/mucosal disease, Demodicosis (Demodex), Bovine malignant catarrhal fever, Rinderpest, Insect bite allergies, Pseudo cowpox, Photosensitization, Urticaria, Contageous TB, Vaccinia/Cowpox Virus.
Treatment
Lumpy skin disease virus has no known cures, it is important to use effective vaccinations to protect against dangerous diseases (Babiuk, 2018). Apart than warning signs and supportive care like wound-healing sprays and antibiotic medicines to control the peripheral bacterial infections of the skin erosion, LSD prevention measures are seldom used in epidemic scenarios. Essentially, there are no effective antiviral medications that can be used to treat LSD, therefore immunisation is the only reliable method of controlling the condition (Das et al, 2021). Therapy options include vaccination, non-steroidal anti-inflammatory pain reliever use to treat the inflammatory disease, paracetamol usage for high fevers, antiviral treatment with methylene blue, antibiotic use to treat secondary infections.
Control
Quarantines, killing or depopulating affected and exposed animals, appropriate case disposal, cleaning and disinfecting the base, and bug control can all be used to suppress LSD outbreaks [Al-Salihi et al, 2014].
Movement restriction: In order to stop the transmission of the illness across borders, it is imperative that LSD infected animals not be moved at all. If an animal with the disease is found within a nation, it should be isolated for examination to stop the sickness from spreading quickly.
Prevent vector movement: vector control techniques including the use of vector traps and pesticides.
Vaccination: There is currently an LSD live-attenuated vaccine on the market. It is either based on SIS Neethling type or on Neethling strains like Lumpy Skin Disease Vaccination for Cattle or Bovivax. Vaccines for sheep pox and goat pox can also be used to prevent LSD since the two viruses are closely related.
Conclusion
Lumpy Skin Disease poses a significant threat to the cattle industry due to its high morbidity and economic impact. The rapid spread of LSD in recent years, especially across new regions like Asia, highlights the importance of implementing robust control measures. Vaccination remains the most effective strategy for preventing outbreaks, with live attenuated vaccines offering protection against the virus. Additionally, integrated approaches, including strict movement controls, vector management, and enhanced biosecurity practices, are crucial in mitigating the spread of LSD. Continued research and surveillance are essential to improve diagnostic methods and develop more effective treatment options to combat this economically devastating disease.
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