CLINICAL, SEROLOGICAL, AND ANATOMOPATHOLOGICAL ASPECTS OF ENZOOTIC BOVINE LEUKOSIS IN A BEEF CATTLE HERD FROM THE METROPOLITAN REGION OF RECIFE, PERNAMBUCO, BRAZIL

Abstract

This study describes the clinical, serological, and anatomopathological diagnosis of enzootic bovine leukosis (EBL) in a beef cattle herd raised in Abreu e Lima, Pernambuco, Brazil. The herd consisted of twenty animals of the Senepol, Limousin, and crossbred breeds, among which one cow showed progressive weight loss, was in permanent lateral recumbency, and presented cachexia, ocular tearing, and enlargement of the right prescapular lymph node. Two other apparently healthy cows showed enlarged parotid lymph nodes. Two serological tests using agar gel immunodiffusion (in-house kit) were performed at three-month intervals, resulting in a seropositivity frequency of 35% (7/20), with most positives being adults (85.7%; 6/7) and females (71.4%; 5/7). Half of the females (50%; 5/10) and 20% of the males (2/10) tested positive. The leukogram (× 10³/µL) of seropositive and seronegative animals showed no statistically significant difference (p > 0.05). The recumbent cow was necropsied, revealing generalized lymphadenomegaly (prescapular, submandibular, and mesenteric lymph nodes, pericardium, liver, intestine, and uterus) and histopathological lesions compatible with lymphosarcoma, characterized by loss of tissue architecture, intense proliferation of neoplastic lymphocytes, scant basophilic cytoplasm, nuclei with chromatin clumping, evident nucleoli, binucleations, and thin fibrovascular stroma. Clinical, serological, and anatomopathological findings confirmed the diagnosis of EBL. They highlighted the importance of integrated investigation and serological monitoring in beef cattle herds to identify carrier animals and control disease dissemination.