Rift Valley Fever - Fact Sheet

What is Rift Valley fever?

Rift valley fever (RVF) is a viral disease that affects sheep, cattle and goats as well as humans. It is transmitted by mosquitoes.

Is RVF a risk to human health?

Yes. Humans are highly susceptible to the virus that causes RVF.

What are the clinical signs of RVF?

RVF affects animals and humans differently.

Animals: Clinical signs depend on the species affected and conditions such as age.

Most animals develop severe illness that may cause:

  • fever;
  • abortions;
  • high rates of mortality (approximately 80% in young lambs and calves, 20% in adult sheep and 10% in adult cattle).

In addition, adult sheep and cattle may show:

  • excess salivation;
  • loss of appetite;
  • nasal discharge; and
  • weakness or diarrhea.

Humans: Some humans will either show no symptoms or develop an influenza like illness.

Signs of illness in humans include:

  • back pain;
  • dizziness;
  • fever;
  • liver abnormalities;
  • weakness; and
  • weight loss.

In other human patients, the illness can progress to:

  • encephalitis (inflammation of the brain);
  • fever;
  • disease affecting the eyes; or
  • haemorrhagic fever.

Approximately one per cent of humans infected with the disease die; most people recover within four to seven days.

Where is RVF found?

The disease is recognized exclusively in Africa, most commonly sub-Saharan Africa, including Madagascar.

In 2007, numerous outbreaks occurred in the Congo, Kenya, and Tanzania.

RVF has never been found in Canada.

How is RVF transmitted and spread?

RVF is carried by mosquitoes, which act as vectors to transmit the virus to livestock. Infected livestock can in turn infect other mosquitoes.

The presence of an epidemic among animals can lead to illness among humans who are exposed to the diseased animals and infected mosquitoes. It is also possible for humans to be infected by other bloodsucking insects.

Laboratory tests have shown that a few of the mosquito species that can transmit the virus are found in certain regions in Canada. Thus, potential vectors for RVF exist in Canada but the risk of these mosquitoes naturally transmitting the virus is low.

How is RVF diagnosed?

While RVF can be suspected based on clinical signs in areas where the disease is known to occur, insect activity or recent rainfall, laboratory tests are required to confirm the diagnosis.

How is RVF treated?

There is no specific treatment for the disease. Vaccines can be used for prevention in animals and humans in areas where the disease is endemic.

What is done to protect Canadian livestock from RVF?

The Canadian Food Inspection Agency (CFIA) imposes strict regulations on the import of animals and animal products from countries where RVF is known to occur. These regulations are enforced through port-of-entry inspections done either by the Canada Border Services Agency or the CFIA.

RVF is a "reportable disease" under the Health of Animals Act. This means that all suspected cases must be reported to the CFIA for immediate investigation by inspectors.

How would the CFIA respond to an outbreak of RVF in Canada?

Canada's emergency response strategy to an outbreak of RVF would be to:

  • eradicate the disease; and
  • re-establish Canada's disease-free status as quickly as possible.

In an effort to eradicate RVF, the CFIA would use its "stamping out" policy, which includes:

  • humane destruction of all infected and exposed animals;
  • surveillance and tracing of potentially infected or exposed animals;
  • quarantine and animal movement controls to prevent spread;
  • decontamination of infected premises; and
  • zoning to define infected and disease-free areas.

In some cases, if the disease is not detected before the virus becomes widespread in the insect population, the strategy could be modified to include vaccinating animals that may be at risk of infection, as well as implementing insect control measures. Owners whose animals are ordered destroyed may be eligible for compensation.

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