FieldDxWesselsbron diseaseClinical signs, differential diagnosis, treatment and prevention in cattle, goats, sheep and horses.
Overview
A mosquito-borne viral disease of sheep, cattle and goats in sub-Saharan Africa, most severe in newborn lambs and kids. Wesselsbron virus, a flavivirus transmitted by Aedes mosquitoes.
Clinical signs
- Newborn lambs under 8 days old are highly susceptible, with mortality rates around 25-30%.
- After a 1-3 day incubation, they show fever, anorexia, listlessness, weakness, increased respiration, and severe jaundice/icterus.
- Pregnant ewes: acute abortion storms, birth of weak/stillborn lambs, hydrops amnii, and ewe mortality.
- Aborted fetuses show congenital central nervous system malformations, hydrocephalus, and arthrogryposis.
- Adult sheep, cattle, and goats: mostly inapparent or mild transient febrile episodes.
- Humans: nonfatal influenza-like symptoms.
- Necropsy shows moderate to severe icterus, yellowish-orange hepatomegaly with diffuse necrosis, and abomasal mucosa petechiae with chocolate-brown contents.
Predisposing factors
- Enzootic in moist and warm coastal regions of sub-Saharan Africa, where activity occurs year-round.
- Transmitted by mosquitoes of the genus Aedes.
- Outbreaks in drier inland regions are linked to abnormally heavy rains and floods that expand vector numbers, often occurring in conjunction with Rift Valley fever.
- Preexisting liver pathology increases severity.
Treatment
- No specific antiviral treatment is available.
- Supportive and symptomatic care is indicated to manage dehydration, electrolyte loss, and secondary complications.
Prevention
1. Vector control (mosquito abatement) is of little practical value in extensive range settings. 2. Attenuated live vaccines were discontinued before 2000 because they induced embryonic death, severe CNS teratology, arthrogryposis, hydrops amnii, and abortion if administered to pregnant ewes.
Source
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Pages 128–135) 44-46, 49, 52, 56-58; The Merck Veterinary Manual 11th Edition (Pages 775–776) 47, 48, 50, 51, 53, 54.
MSD Veterinary Manual — Wesselsbron Disease in Animals (accessed 2026-08-11)
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