Lumpy Skin 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. Secondary bacterial infection often aggravates the condition. Traditionally, lumpy skin disease is found in southern and eastern Africa, but in the 1970s it extended northwest through the continent into sub-Saharan west Africa. Since 2000, it has spread to several countries of the Middle East and in 2013 was confirmed in Turkey.
The causal virus is related to that of sheeppox. The prototype strain is known as the Neethling poxvirus. Lumpy skin disease appears epidemically or sporadically. Frequently, new foci of infection appear in areas far removed from the initial outbreak. Its incidence is highest in wet summer weather, but it may occur in winter. It is most prevalent along water courses and on low ground. Because quarantine restrictions designed to limit the spread of infection have failed, biting insects have been suspected as vectors; however, outbreaks have occurred under conditions in which insects practically could be excluded. Experimentally, three species of hard ticks found in Africa have been shown to biologically transmit the virus. Because the disease can be experimentally transmitted by infected saliva, contact infection is considered as another route of infection. African buffalo are suspected as maintenance hosts in Kenya.
A subcutaneous injection of infected material produces a painful swelling and then fever, lacrimation, nasal discharge, and hypersalivation, followed by the characteristic eruptions on the skin and other parts of the body in ~50% of susceptible cattle. The incubation period is 4–14 days.
The nodules are well circumscribed, round, slightly raised, firm, and painful and involve the entire cutis and the mucosa of the GI, respiratory, and genital tracts. Nodules may develop on the muzzle and within the nasal and buccal mucous membranes. The skin nodules contain a firm, creamy-gray or yellow mass of tissue. Regional lymph nodes are swollen, and edema develops in the udder, brisket, and legs. Secondary infection sometimes occurs and causes extensive suppuration and sloughing; as a result, the animal may become extremely emaciated, and euthanasia may be warranted. In time, the nodules either regress, or necrosis of the skin results in hard, raised areas (“sit-fasts”) clearly separated from the surrounding skin. These areas slough to leave ulcers, which heal and scar.
Morbidity is 5%–50%; mortality is usually low. The greatest loss is due to reduced milk yield, loss of condition, and rejection or reduced value of the hide.
The disease may be confused with pseudo-lumpy skin disease, which is caused by a herpesvirus (bovine herpesvirus 2). These diseases can be similar clinically, although in some parts of the world the herpesvirus lesions seem confined to the teats and udder of cows, and the disease is called bovine herpes mammillitis (see Diseases of Bovine Teats and Skin).
Pseudo-lumpy skin disease is a milder disease than true lumpy skin disease, but differentiation depends essentially on isolation and identification of the virus. Histologic and ultrastructural examination of nodules may be helpful. Poxlike intracytoplasmic inclusion bodies or eosinophilic intranuclear herpesvirus inclusions may be seen in the nodules.
Dermatophilus congolensis also causes skin nodules in cattle (see Dermatophilosis).
Quarantine restrictions are of limited use. Vaccination with attenuated virus offers the most promising method of control. The viruses of goatpox and sheeppox passed in tissue culture also have been used.
Administration of antibiotics to control secondary infection and good nursing care are recommended.