FieldDxBluetongueClinical signs, differential diagnosis, treatment and prevention in cattle, goats, sheep and dogs.
Overview
A viral disease of domestic and wild ruminants, most severe in sheep, spread by biting midges. Bluetongue virus (BTV), an RNA virus of the genus Orbivirus, transmitted by Culicoides midges.
Clinical signs
- Sheep: Incurs vascular endothelial damage, altered capillary permeability, intravascular coagulation, and necrosis.
- After a 4-6 day incubation period, a high fever (105°–107.5°F) is accompanied by listlessness and reluctance to move.
- About 2 days later, edema of the lips, nose, face, submandibular area, and eyelids develops.
- Nasal discharge is initially serous, turning mucopurulent and blood-stained.
- Buccal mucosa shows excoriation, frothy salivation, and a cyanotic ("blue") tongue, which may protrude.
- Coronary bands are hyperemic (purple-red band), leading to lameness, myositis, and torticollis.
- Cattle: Rarely symptomatic; signs may include fever, stiffness, laminitis, coronitis, oral vesicles/ulcers, hyperesthesia, and vesicular dermatitis.
- In Utero: Exposure can cause abortion, stillbirth, arthrogryposis, campylognathia, prognathia, hydranencephaly, and "dummy calf" syndrome.
Predisposing factors
- Transmitted by biting midges of the genus Culicoides.
- Endemic in tropical and subtropical regions.
- Epidemics occur when climatic conditions allow vector expansion or when naive animals are introduced to endemic zones.
- Cattle serve as the primary reservoir and amplifying host, attracting midges and maintaining high-titer viremia.
Look-alikes to rule out
Treatment
- There is no specific treatment available.
- Supportive and symptomatic care includes rest, housing protected from the weather and hot sun, local irrigations with mild disinfectants, fluid and electrolyte therapy, and treatment to control secondary bacterial infections.
Prevention
1. Control of vector midges via insecticides, repellents, or sheltering animals during peak vector feeding times. 2. Active immunization using inactivated or modified-live vaccines. 3.
Source
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Pages 107–118) 18-20, 22-24, 26, 28, 34, 38-40; The Merck Veterinary Manual 11th Edition (Pages 738–740) 21, 25, 27, 29, 35, 41; The Merck Veterinary Manual 11th Edition (Pages 852–854) 37, 42, 43.
MSD Veterinary Manual — Bluetongue in Ruminants (accessed 2026-08-11)
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