Integrated management of a bovine ephemeral fever outbreak in a Khuzestan dairy herd: a case study on practical control strategies

Bovine ephemeral fever (BEF), or “three-day sickness,” is an arthropod-borne viral disease of cattle that causes substantial economic losses in dairy production, particularly in tropical and subtropical regions. Khuzestan province in southwestern Iran is a high-risk area for BEF due to its hot climate, high humidity, and dense vector populations. Despite repeated outbreaks, there is limited field-level documentation describing practical, integrated outbreak management strategies. This case study reports the clinical, epidemiological, and management features of a BEF outbreak on a large commercial dairy farm in Khuzestan. In the summer of 2023, a bovine ephemeral fever (BEF) outbreak occurred in a commercial dairy herd comprising 2,100 Holstein-Friesian cows near Shushtar, Khuzestan Province, Iran. Affected animals exhibited an abrupt onset of high fever (40.5–41.5 °C), lameness, muscle rigidity, recumbency, and a marked decline in milk production. Prior to initiation of treatment, clinical deterioration progressed rapidly: by Day 3, 85 cows (4.0% of the herd) had developed clinical signs, approximately 30% of which were recumbent, and the average milk yield of affected cows had decreased by approximately 11–12 kg/cow/day compared with pre-outbreak levels. No fatalities were recorded before the initiation of supportive therapy. Over a two-week period, a total of 481 cows (22.9%) developed clinical signs consistent with BEF. Laboratory confirmation was obtained by reverse transcription nested polymerase chain reaction (RT-nested PCR), which detected bovine ephemeral fever virus (BEFV) RNA in sampled animals. Phylogenetic analysis of the viral glycoprotein gene demonstrated 98.02% nucleotide identity with previously reported Middle Eastern BEFV strains. An integrated outbreak management strategy was subsequently implemented, including administration of non-steroidal anti-inflammatory drugs (NSAIDs), selective antibiotic therapy for suspected secondary bacterial infections, intensified vector control measures (deltamethrin spraying and elimination of standing water sources), and vaccination of replacement heifers. Antibiotic therapy was restricted to clinically justified cases to minimize unnecessary antimicrobial use. Following implementation of these interventions, the incidence of new clinical cases declined markedly, and the outbreak resolved with three fatalities (0.14%). Milk production in affected cows gradually recovered, returning toward baseline levels within 10–14 days after clinical recovery. Timely implementation of coordinated clinical management, vector control, and herd-level preparedness measures can substantially reduce the impact of BEF outbreaks in endemic regions such as Khuzestan. This case highlights the importance of early detection, structured response protocols, and farm personnel training in mitigating production losses during vector-borne disease outbreaks.