Wesselsbron Disease
By Dr Mackie Hobson BSc(Agric),BVSc

1. Diseases

Wesselsbron disease is usually associated with Rift Valley Fever (RVF) as the conditions and vectors (mosquitos) are similar.

The disease was first identified in 1955 in Wesselsbron in the OFS during the RVF outbreak.

New-born Angora kids are most susceptible and deaths are seen whereas in adult goats cases are usually subclinical, although abortions may occur.

Wesselsbron disease is caused by a flavivirus.

Evidence of infection has been reported in cattle, sheep, goats, camels, pigs, donkeys, horses, ostriches, and wild ruminants.

How is Wesselsbron transmitted?

Wesselsbron virus is transmitted by mosquitoes. Aedes are thought to be the major vectors, but it has also been detected in other mosquitoes including Culex, Anopheles and Mansonia.

Clinical signs:

After an incubation period of 1–3 days in kids

• Non-specific signs of fever, anorexia, listlessness, weakness, and increased respiration.
• Icterus (jaundice)
• Death may occur within 72 hr (up to 30% of kids may die)

Adult goats:

•  
• Occasional abortions,
• Congenital CNS malformations with arthrogryposis, and hydrops amnii are seen in ewes.

Wesselsbron disease and Rift Valley fever share many clinical and pathologic features. However, Wesselsbron disease is usually milder, producing much lower mortality, fewer abortions, and less destructive liver lesions.

Post Mortem findings:

• Moderate to severe icterus and hepatomegaly (icterus more significant than RVF)
• Petechiae and ecchymoses (bleeding) are commonly found in the mucosa of the abomasum, the contents of which are chocolate-brown in colour.

 2 human cases of Wesselsbron disease that were laboratory confirmed during the 2010-2011 RVF outbreak.

Wesselsbron liver                              (Photo AfriVIP)

Diagnosis:

• The clinical signs and PM

Need to be distinguished from RVF

• The virus can be isolated from almost all organs of kids that have died during the clinical stage of the disease.
• Confirmation of the viral identity can be accomplished by virus neutralization.
• serology

Control:

• Only a live vaccine is available, which can be used in conjunction with the live Rift Valley vaccine, but not in pregnant animals.
• Spraying of goats with insecticidal solutions; especially parts not covered by mohair
• Moving goats away from river and vlei camps where mosquitoes breed, to higher ground

References:

Peter N. Thompson, BVSc, MMedVet, PhD, Professor of Veterinary Epidemiology, Faculty of Veterinary Science, University of Pretoria

Kleinvee-siektes,  J.De Wet & G. Bath

Human cases of Wesselsbron disease, South Africa 2010-2011. Weyer J1, Thomas J, Leman PA, Grobbelaar AA, Kemp A, Paweska JT.