Rift Valley fever (RVF) is an acute viral hemorrhagic fever that is most commonly seen in domesticated animals such as cattle, buffalo, sheep, goats, and camels and can cause illness in people. The disease is caused by RVF virus.
RVF was first reported in livestock by Veterinary officers in Kenya’s Rift Valley in the early 1910s. It is generally found in regions of eastern and southern Africa, but exists in most of sub-Saharan Africa, including West Africa and Madagascar.
How it is transmitted?
People usually get Rift Valley fever through contact with blood, body fluids, or tissues of infected animals, mainly livestock such as cattle, sheep, goats, buffalo, and camels. This direct contact can occur during slaughter or butchering, while caring for sick animals, during veterinary procedures like assisting an animal with giving birth, and when consuming raw or undercooked animal products.
People can also get RVF through bites from infected mosquitoes.
RVF outbreaks are mostly linked to years of unusually heavy rainfall and flooding, because mosquitoes spread the disease and heavy rainfall allows more mosquito eggs to hatch.
How RFV spreads in animals?
Normally seen during periods of unusually heavy rainfall that cause localised flooding
Excessive rainfall allows mosquito eggs to hatch
The eggs are naturally infected with RVF virus and the resulting mosquitoes transmit this virus to livestock they feed on
Once the livestock are infected, other mosquitoes and biting insect can become infected by the animals
How Humans Get RVF?
Through bites from infected mosquitoes and other biting insects through the virus contaminated mouth parts
If exposed to blood, body fluids or tissues of the infected animals
Through direct exposure to infected animals during slaughter or veterinary clinical procedures
Signs in cattle
Fever, lack of appetite, bloody and dull coat, weakness and depression, dry diarrhoea, discharge from eyes and nose, fall in milk production in lactating cows and abortion exceeding 85 percent.
Signs in sheep and goats
Sudden death in youth lambs without signs, high fever lasting 24-96 hours, lack of appetite, abdominal pain, rapid breathing, bloody diarrhoea, vomiting, discharge from eyes and nose, death within 24-36hours, mortality rate in young lambs can be as high as 90percent and 100 percent abortion in pregnant animals.
Fatality among adult animals is significantly lower.
Prevention and Control
People living in or visiting areas with RVF can prevent infection with the following steps:
No vaccines are currently available for vaccination in people.
Different types of vaccines are available for use in animals. A modified live vaccine is used for controlling RVF in Africa. This vaccine only requires a single dose, but is known to cause birth defects and abortions in pregnant livestock and may only provide cattle with limited protection from infection with RVF.
Additionally, RVF can be controlled through: