Sporadic Bovine Leukosis

The most common form of internal spontaneous cancer in cattle. A rare form of malignant neoplasia in cattle, affecting the lymphatic system. It is completely separate entity from the enzootic bovine leucosis.

Common synonyms

SBL. Sporadic leukaemia/lymphoma.

Aetiology

The cause of SBL is not known. It is taught that arises from a combination of environmental and genetic factors. Of the environmental factors, the potential role of carcinogens has been cited.

Epidemiology

Usually, individual cattle.  Mostly in cattle younger than 3 years.  Three forms:

·      Cutaneous lymphoma (1 - 3 up to 4 years of age)

·      Juvenile multicentric (mostly 4 - 8 months of age, although others state <6 months of age)

·      Thymic (0.5 - 2 years of age)

Pathophysiology

T-cell tumour in origin.

Clinical findings

Non-specific signs that differ dependent on the organs affected by the tumours.

Cutaneous form - cutaneous plaques (1 - 5 cm) on neck, back, rump, thighs. May regress spontaneously, followed by remission or death from the generalised form.

Juvenile form - progressive to fatal weight loss, accompanied by lymphadenopathy and obtundancy. Sometimes, dyspnoea, fever, posterior paralysis, and recurrent bloat. About half develop lymphoid leukaemia.

Thymic form - bloat, dyspnoea, fever, jugular distention, local oedema, and muffled heart sounds. Sometimes, swelling of the cervical thymus and/or lymphoid leukaemia.

Post-mortem findings

Lymphadenopathy.

Diagnosis

Clinical signs. Post-mortem findings. Histopathology. Lymph node/Thymic biopsy.

Principal differential diagnosis

It is essential to differentiate it from the enzootic bovine leucosis.

Treatment

No treatment. Generally associated with a very poor prognosis.

Cutaneous form may regress with corticosteroid treatment.

Advanced cases are invariably fatal.