Lumpy Skin Disease (LSD)…. An Emerging Bovine Viral Disease

Lumpy skin disease is an infectious, eruptive, occasionally fatal disease of cattle characterized by nodules on the skin and other parts of the body.

BY Dr. Aisha Khatoon, Sadaf Faiz

 Lumpy skin disease is also referred to as Pseudourticaria, Neethling virus disease, Exanthema nodularis bovis, and Knopvelsiekte.

History

LSD was first ever reported in Zambia in 1929. However, in three years that followed, LSD spread like wildfire to other southern and northern African countries. LSD was first reported in Asia and the Pacific region in 2019 in north west China, Bangladesh and India. During 2020, LSD continued to spread across continental Asia with many countries.

On 2 February 2022, The Dairy and Cattle Farm Association said that the disease of lumps and boiled skin of dairy animals has entered Landhi Dairy Colony, Karachi and other enclosures.

Etiology

LSD is caused by s double-stranded DNA, brick shaped virus. The virus is one of three closely related species within the genus capripoxvirus, the other two species being Sheep pox virus and Goat pox virus.

Economic Impact

Although the mortality rate is usually low, the disease is of major economic importance due to production losses resulting from severe emaciation, lowered milk production, abortion, secondary mastitis, loss of fertility, extensive damage to hides, and a loss of draft from lameness.

Morbidity/ Mortality

The morbidity rate in cattle can vary from 4 to 45% (sometimes up to 100%), depending on the presence of insect vectors and host susceptibility. Mortality is low in most cases (1 to 3%), but can be as high as 20 to 85%.

Transmission

Transmission of the LSD virus is primarily by biting flies (Stomoxy calictrans and Biomyia fasciata), ticks and particularly mosquitoes (e.g. Culex mirificens and Aedes natrionus). Epidemics occur in the rainy seasons. Direct contact is also a minor source of infections. Virus can be present in cutaneous lesions, saliva, nasal discharge, milk and semen. The virus can survive in desiccated crusts for up to 35 days. There is no carrier state. The spread of the disease is often related to the movement of cattle.

A schematic diagram of LSD pathogenesis

Clinical Signs

The incubation period varies from 2 to 5 weeks however, under experimental conditions incubation period has been observed lessen from 7 to 14 days. Clinical signs can range from in-apparent to severe. Host susceptibility, dose, and route of virus inoculation affect the severity of disease. Young calves often have more severe disease.

• High body temperature (>40.5℃)                         •Lacrimation
• Nasal discharge and hypersalivation •Nodule development
• Raised, circular, firm, coalescing nodules – Common on head, neck, udder, perineum, legs – Cores of necrotic material called “sit-fasts” •Decreased milk yield
• Enlargement of superficial lymph nodes. • Rhinitis, conjunctivitis
• Lameness • Abortion and sterility

Post mortem lesions

Post mortem lesions can be extensive. Characteristic deep nodules are found in the skin which penetrate into the subcutaneous tissues and muscle with congestion, hemorrhage, and edema. Lesions may also be found in the mucous membranes of the oral and nasal cavities as well as the gastrointestinal tract, lungs, testicles, and urinary bladder. Bronchopneumonia may be present, and enlarged superficial lymph nodes are common. Synovitis and tenosynovitis may be seen with fibrin in the synovial fluid.

Distinguishing lesions of LSD: Raised and separated narrow ring of hemorrhage” (A), Skin lesions leaving ulcer (B) and “sit fast” like “inverted conical zone” of necrosis (C).

Differential Diagnosis

• Pseudo-lumpy skin disease • Bovine herpes mammillitis
• Dermatophilosis • Ringworm
• Insect or tick bites • Rinderpest
• Demodicosis • Hypoderma bovis infestation
• Photosensitization • Bovine papular stomatitis
• Urticaria • Cutaneous tuberculosis
• Onchocercosis

Diagnosis

LSD can be suspected when characteristic skin nodules, fever, and swollen lymph nodes are seen. Confirmation of lumpy skin disease in a new area requires virus isolation and dentification. Antigen testing can be done using direct immunofluorescent staining, virus neutralization, or ELISA. Typical capripox (genus) virions can be seen using transmission electron microscopy of biopsy samples or desiccated crusts. This finding, in combination with a history of generalized nodular skin lesions and lymph node enlargement in cattle, can be diagnostic. Serological tests include an indirect fluorescent antibody test, virus neutralization, Western blot, and ELISA. Cross-reactions may occur with other poxviruses.

Treatment

There is no specific treatment of Lumpy Skin Disease. Different antibiotics and supportive therapy are given to treat secondary bacterial infections. It may take up to 6 months for animals severely affected by LSD virus to recover fully. Animals infected with LSD virus generally recover.

Prevention from Lumpy Skin Disease in Cattle

There is a famous line called “Prevention Is Better Than Cure”.

Lumpy Skin Disease in Cattle can be kept away by different method of prevention. Some of the preventive methods are: –

➡️Most effective way is to restrict the import of animals from infected countries. The animals which are imported should be kept in Quarantine and properly tested.

➡️Different insects like mosquitoes should be effectively controlled using insecticides.

➡️There should be good provision of drainage and channels should be made for the urine also.

➡️The shed of cattle should be cleaned regularly and try to make shed dry.

➡️Regularly monitoring of animals to detect the symptoms earlier.

➡️Vaccination can be given to healthy animal. The vaccine called “Neethling” which contain the strain of LSD are injected in blood of animal. It is effective to control the LSD.

Zoonotic Importance

The virus appears to be highly host specific. LSDV is not zoonotic.

Authors:

Dr. Aisha Khatoon, Sadaf Faiz

Department of Pathology, UAF