Dr. Sagar R. Surjagade, Dr. Lakshmikant, Dr. Ashvini P Bansod and Dr. Abhilash D. Jadhao
INTRODUCTION
Lumpy skin disease (LSD) is an infectious disease caused by Lumpy skin disease virus (LSDV) of the genus Capripox virus, its strain ‘Neethling’ was first to be isolated in South Africa. The disease is mainly characterized by sudden appearance of fever and skin lesions in several animals in the herd. It leads to decrease in milk and meat production, Abortions, majorly damage of skins and hides as well as death or direct losses like culling of sick cattle. This is a major setback for the livelihoods of poor smallholders and backyard farmers.
EPIDEMIOLOGY:
The disease was first reported in Zambia in 1949 and it continued to spread towards north, at present it is everywhere in Africa (World Animal Health Information database, OIE WAHID Interface). Only Libya, Algeria, Morocco and Tunisia are still officially free of lumpy skin disease. It is believed that the spread of LSD into Egypt, Israel and the rest of the middle-east is majorly due to import of live cattle from Africa both legally and illegally. From 2000 Outbreaks were reported in Israel (2012), Lebanon (2013) and Jordan (2013). The major outbreak in the recent times occurred in Turkey where LSD swept across the whole territory between 2013 and 2015. Outbreaks were also detected in multiple Russian states and fast-moving LSDV poses serious risk in the central and southern Asia. LSDV causes diseases only in cattle and water buffalo and it is highly host specific hence LSDV is not zoonotic. Evidences from studies suggest that the disease exhibits higher morbidity and mortality to Holstein Friesian and Cross bred cattle than local zebu cattle. Similarly, animals of all age-groups are susceptible, of which cows in the time of lactation and young animals usually exhibit severe clinical symptoms.
TRANSMISSION:
The primary mode of transmission is through blood sucking arthropod, direct transmission of LSDV amongst the animals is inefficient. The disease is also transmissible through infected milk to suckling calves and the virus is excreted from the semen of infected bulls. LSDV is a highly stable virus, withstanding for prolonged periods. It can survive in the necrotic nodules of skin for up to 33 days or more, desiccated crusts around 35 days and can also stay in the environment for long time. The virus is sensitive to sunlight hence the vaccines are also contained in dark bottles. So, the virus persists for very long time in dark environmental conditions such as enclosed animal sheds.
CLINICAL FINDINGS:
Typically, animal develops a biphasic febrile response 2-4 weeks post exposure to the virus. Animal remains in the febrile phase for 4-14 days. The characteristic feature of the disease is skin nodules which appear before or during the second rise in body temperature, four to ten days after the initial febrile response. The size of the nodules is usually uniform but multiple nodules may fuse to form large, irregularly circumscribed plaques.
These nodules appear around the head initially, including the mouth, nose and eyes, followed by the neck, body, udder, genitals, legs and tail. Later, the skin lesions often become necrotic plugs or so-called sit-fast which then slough off, leaving large ulcers in the skin. The secondary bacterial infections usually take rise from these necrotic cores and are attractive for flies which may cause myasis. When these skin nodules heal, they eventually leave permanent scars on the hides.
In severe condition, the ventral parts of the body like dewlap and legs may become slightly edematous before the appearance of the nodules. In some cases the animal suffers from lameness that results from the rise of nodular skin lesions may extending into underlying tissue such as tendons and tendon sheaths.
Initially rhinitis and nasal discharge start as serous but later on they become mucopurulent. Conjunctivitis and ocular discharge can occur and sometimes keratitis is observed. In addition, profuse salivation, loss of appetite, weight loss because of the characteristic pox lesions developing in the mucous membranes of the mouth as well as the digestive tract and depression may also occur. Pock lesions can also be found in the mucous membranes of respiratory tract leading to infection in the lung subsequently to primary or secondary pneumonia and respiratory distress.
The studies in the recent outbreak suggested that a high percentage of the LSD infected cows suffered from ovarian inactivity and showed no signs of oestrus, with smaller than average ovaries. In bulls, the scrotum, glans penis, preputial mucosa and parenchyma of the testes can be affected.
Even though the mortality of animals due to LSD virus is low, the affected cattle become debilitated and can remain in poor condition for many months following infection. The hide value will be reduced remarkably in the leather industry due the scars left behind by the nodules. Milk yield is reduced in lactating cattle and mastitis can occur leading to damage of economic stability of the farmer.
DIAGNOSIS:
Presumptive diagnosis is by clinical signs, by observing the characteristic nodules. Conventional and real-time polymerase chain reaction (PCR) methods are developed for the detection of three members of the genus Capripoxvirus. Virus isolation followed by PCR to confirm is the confirmatory test that can be done and virus neutralization test is regarded to be the most reliable serological test.
TREATMENT AND CONTROL :
There is no specific antiviral drug available for the treatment of LSD. The only treatment available is supportive care by administering antibiotics to prevent secondary bacterial infections. Anti-inflammatory drugs to be given to alleviate the pain and to enhance its appetite.
Quarantine is of little use because the major transmission is by insect vectors. Multiple studies reported a sharp fall in the disease occurrence when stringent measures were taken regarding the control of arthropod vectors.
Control includes vaccination using live attenuated vaccines are used to control the disease. However, currently there is no universal vaccine available. “Neethling” strain of virus was attenuated and used as vaccine. Other sheep pox vaccines used against LSDV are Yugoslavian RM-65 strain and Romanian sheep pox strains.
