Genetic Characterization of Brucella Species in Some Dairy Farms of the Nile Delta, Egypt

Abstract

Brucellosis, as a highly zoonotic disease, has been endemic in Egypt's Nile Delta since 1939 and affects cattle, buffaloes, sheep, and goats, with severe economic losses, and continues to threaten livestock-based communities. This research investigated the seroprevalence of brucellosis in the organized dairy farms in different governorates of Egypt's Nile Delta. Milk Ring Test (MRT) was a screening test for the bulk milk tank, positive farms were investigated serologically using Rose Bengal Test (RBT) and Buffered Acidified Plate Antigen Test (BAPAT). Milk Ring Test (MRT) screening diagnosed brucellosis on 21 of 65 farms (32.31%), the positive farms being dispersed as follows: 40% in Damietta, 25% in Sharqia, and 30% in Behira. Individual animal serological tests confirmed infection levels of 10.7% in Damietta, 22.9% in Sharqia, and 16.4% in Behira with both RBT and BAPBT. Brucella organisms were cultured from 10 farms (47.6% of the seropositive farms). Molecular typing by Abortus, Melitensis, Ovis and Suis Polymerase Chain Reaction (AMOS-PCR) confirmed nine isolates as Brucella melitensis biovar 3 and one as Brucella abortus biovar 1. These findings highlight the diagnostic challenge of brucellosis in endemic settings, where there is no single definitive test. The prevalence of B. melitensis biovar 3 in Egypt's Delta region is fostered by mixed farming and poor hygiene and demands concerted control efforts using serological and molecular diagnostics, test and slaughter policies, and vaccination. Consumption of raw milk and dairy products from infected animals remains a key transmission mode, emphasizing the need for strict food safety policies to protect public health.