Categories: How to Livestock

Rift Valley Fever in sheep and goats

Rift Valley Fever causes abortions and death of lambs, and can be fatal to humans. Vaccination is crucial.

Rift Valley fever (RVF) is caused by a virus transmitted by mosquitoes during summer after heavy rainfall and persistent flooding. Thereafter, RVF spreads along river courses. Infected animals transmit the disease to others by means of aborted foetuses. RVF can also be spread by needles during vaccination.

RVF is a zoonosis: humans can contract it when handling sick animals or aborted foetuses, or performing post-mortem investigations. In fact, any person who works closely with animals, including an abattoir employee, can become infected.
Symptoms include fever, muscle pains and headaches that often last for up to a week. It can lead to loss of sight three weeks after infection.

Signs in sheep and goats
The RVF virus causes abortions in sheep and goats, leading to large-scale deaths in young lambs. Up to 95% can die within days.

The incubation phase is very short, and lambs can show signs of illness within one to three days of infection. Some die within just 12 hours. Newborn lambs are prime targets as their wool or hair is very short. Adult sheep show signs of weakness and sometimes bloody diarrhoea.

Bleeding from the nose also occurs.

Preventing infection
Two effective RVF vaccines are available for sheep and goats.

Live vaccine
This provides long-lasting protection after a single vaccination. But it cannot be used in pregnant animals as it may cause abortions. The vaccine also affects brain tissue.

If a pregnant ewe is vaccinated with it before the foetus is three months old, the vaccine will attack the undeveloped brain of the lamb and cause malformation.
The lambs and kids of vaccinated sheep and goats should be vaccinated at six months or at weaning but not before, or natural immunity will be destroyed.

Inactivated vaccine
This was developed for pregnant sheep and goats. Its disadvantage is that immunity lasts for only one year at most.
Source: Mohale, D: ‘Abortions and causes of death in newborn sheep and goats’ (ARC-Onderstepoort Veterinary Institute).

Recent Posts

Learn about beef BLUP basics

Producers use breeding values to determine the long-term value of certain animals to their herds.

52 mins ago

Rethinking sustainable development

Growing awareness of the interconnectedness between water, energy and food security is resulting in a more holistic way of measuring…

21 hours ago

Taking steak to the next level

Steak can be cooked and served in a variety of ways, but this Asian-inspired marinade can turn even the tastiest…

1 day ago

Land: access vs ownership

The one crucial point that should not be forgotten by all the organisations and political parties representing, or claiming to…

2 days ago

Agri interventions key to Ramaphosa’s economic stimulus package

President Cyril Ramaphosa announced that government has reprioritised funding towards an economic stimulus package that would focus on agriculture, among…

3 days ago

Biosecurity: your first line of defence against disease

Dr Fambies van Biljon, veterinarian at Sovereign Foods, talks to Glenneis Kriel about the crucial need to establish a well-run…

3 days ago

This website uses cookies.