Lumpy skin disease is an infectious, highly contagious occasionally fatal disease of cattle characterized by nodules on the skin and other parts of the body, both internally and externally. Lumpy skin disease is most often found in southern and eastern Africa, but in the 1970s it extended northwest through into middle and northern Africa as well as the middle east.
Lumpy skin disease appears epidemically or sporadically its incidence is highest in wet summer weather, but it may occur in winter because of global warming. Temperatures are not dropping low enough to remove the responsible vector population Since it is largely a vector-borne disease, environmental conditions need to be right for the disease to occur. There are many mechanisms of transmission in this disease
- Ticks– R.appendiculatus
- Biting flies -Tabanid species and stomoxys calcitrans
The incubation period is 4–14 days. Infected cattle develop primary viremia which presents with a fever. Lethargy, inappetence, and malaise are also common clinical signs seen at this stage of infection.
The nodules are well-circumscribed, round, slightly raised, and full thickness through the skin. Nodules may develop in the respiratory tract as well as along the digestive system on any of the epithelial surfaces. Distal limb swelling is also a common occurrence because of the impedance of lymphatic drainage from the distal limbs.
In time, the nodules either regress or necrosis of the skin results in hard, raised areas known as sit-fasts. These areas slough to leave ulcers, which heal and scar.
A diagnosis of LSDV is often made on clinical signs. However, histopathology, virus isolation, or PCR are diagnostic tools that will confirm infection of LSDV. The disease may be confused with the less clinically important pseudo-lumpy skin disease, which is caused by a herpes virus (bovine herpesvirus 2). These diseases can be similar clinically, but pseudo-lumpy skin disease is less severe clinically as compared to LSDV.
Treatment and prevention:
Administration of broad-spectrum antibiotics to control secondary infections, anti-inflammatories to reduce pyrexia and improve clinical scores, good nursing care, and isolating the animal from the main herd are recommended.
Vaccinating the animal is the best method of prevention. The vaccine should be administered annually in a commercial herd and at feedlot entry for every calf regardless of the season. A very important note to make is to never vaccinate in the face of a lumpy skin outbreak. This will only perpetuate the disease spread and worse the outbreak. Vaccination can be continued two weeks after the last clinical case has been seen.
Pseudo-lumpy skin disease is a milder disease than a true lumpy skin disease, but differentiation depends essentially on isolation and/or identification of the causal virus. The pox virus of lumpy skin disease can be demonstrated by electron microscopy in early skin lesions. The two diseases can be distinguished by PCR.