2. RIFT VALLEY VIRUS
It is virus of Bunyavirales family
It causes Viral Zoonotic disease
Affects primarily livestock (cattle,
sheep, goats, camels, etc.) are spread
mostly by mosquitoes.
Can be transmitted to humans
Infection can lead to high rates of
disease and death in animals and
humans.
The Disease Classified as an OIE List A
disease (A080)
3. Origin
In September 2000, an outbreak
was confirmed in Saudi Arabia and
Yemen, marking the first reported
occurrence of the disease outside
the African continent and raising
concerns that it could extend to
other parts of Asia and Europe
The total case fatality rate has varied
widely between different epidemics
but, overall, has been less than 1% in
those documented.
Most fatalities occur in patients who
develop the Hemorrhagic jaundice
form.
The virus was first identified in 1931 during an investigation into an
epidemic among sheep on a farm in the Rift Valley of Kenya. Since
then, outbreaks have been reported in sub-Saharan and North Africa.
5. Structure of the Virus
RVFV belongs to the genus Phlebovirus, family Bunyaviridae.
Bunyaviruses are enveloped and have a tri-segmented single-
stranded RNA genome of negative or ambisense polarity.
The envelope is composed of a lipid bilayer containing the Gn
and Gc glycoproteins forming surface subunits.
Transcription and replication take place in the cytoplasm
The viral genome has three segments which are L,M and S.
The L and M segments are of negative polarity while the S
segment utilizes an ambisense strategy to code for both N and
NSs.
6. ETIOLOGY
Causative agent: The
Rift Valley Fever Virus
A family of enveloped
negative strand RNA
viruses
RVF is an Arborvirus
which means it is
transmitted by
arthropod (insects,
arachnids, centipedes,
crustaceans) vectors
and vertebrates
Transmitted by
mosquito vectors to
livestock
There is only one
serotype of RVF virus.
Stable at 60 C to 23 C
*Lipid solvents
*Detergents *Low pH
7. Mode of
Action
There is no direct person-to-person
transmission.
Human can be infected in RVF by handling
of animal tissues during slaughtering &
butchering.
By Vector: RVF virus is transmitted primarily
by infected mosquitoe bites, mainly the
Aedes species, which can acquire the virus
from feeding on infected animals.
The female mosquito is also able to
transmitted the virus directly to her
offspring via eggs leading to new generations
of infected mosquitoes hatching from eggs.
8. Transmission Via Mosquito to Animal &
Human
Heavy Rainfall,
flooding leads to
high Mosquito
abundance
Endemic
transmission cycle
(rare)
Epizootic
transmission cycle at
the, “Dambo”
Endemic
transmission cycle
at the, “Dambo”
9. Mode Of Action (Human)
The virus infects humans through inoculation, for example
via a wound from an infected knife or through contact
with broken skin, or through inhalation of aerosols
produced during the slaughter of infected animals.
Caused by a cytopathic virus that targets the liver and the
brain
It is suspected that the virus moves from the skin to
draining lymph nodes, where it replicates and spreads
throughout the body.
It may also cross the blood-brain barrier and infect
neurons and glia, leading to meningoencephalitis and
retinitis two to three weeks after onset of infection
10. Susceptibility
Susceptibility appears to be general in both sexes
at all ages.
Humans are highly susceptible to infection but
represent dead end hosts.
Inapparent infections and mild disease are
common. Since infection leads to immunity,
susceptible in endemic areas are mainly young
children.
11. Incubation Period
Experimentally, incubation period of this virus in new-born
lambs, kids, calves, and puppies, is about 12 hours.
The incubation period in adult sheep, cattle, goats, and
dogs may be as long as 3 days.
In humans, the incubation period is 4 to 6 days.
12. SIGNS AND SYMPTOMPS IN ANIMAL
Fever
Listlessness
Weight loss
Loss of Appetite
Bloody Diarrhea
Increased respiratory rate
Blood tinged nasal discharge
13. SIGNS AND SYMPTOMPS IN ANIMAL
Majority have mild symptoms or no
symptoms at all.
Flu like symptoms: fever, headache,
muscle pain, joint pain, etc.
Other symptoms that may occur are
neck stiffness, sensitivity to light, loss
of appetite, and vomiting.
Symptoms usually last 4 to 7 days
14. Pathogenesis of RVF in Animal
• Most of the mice infected with wild-type (wt) RVFV ZH548 or ZH501
strains die in 3 to 5 days.
• The symptom is often followed by death within one hour
Mouse:
Hamster:
• The Syrian hamster is one of the most susceptible rodents to RVFV.
• Death occurs in 2 to 3 days after intraperitoneal inoculation with
massive liver necrosis
Sheep:
• Sheep with more than one week old were relatively resistant to RVFV
infection, yet did exhibit fever (39 to 40 °C), viremia, diarrhea, nasal
discharge, and decreased activity.
15. Pathogenesis of RVF in Humans
Patients suffer
from a self-
limiting, febrile
illness.
Some patients
develop
neurological
disorders,vision
loss, hemorrhagic
fever or
thrombosis.
Figure: The pathological forms of Rift Valley fever in humans.
17. Diagnosis
There are several different
methods:
Serological tests such as
enzyme-linked immunoassay
(the "ELISA" or "EIA" methods)
may confirm the presence of
specific IgM & IgG antibodies
to the virus.
Antigen detection tests and
RT-PCR.
Virus isolation by cell
culture.
FIG: RIFT Valley Fever Virus Diagnosis
18. Differential Diagnosis
Nairobi Sheep diseases:
No Hepatitis,not in new born lambs
Bluetongue:
Foot lesions, also no hepatitis
Heartwater:
Serous fluid in body Cavities and Neurological Sign
Ephemeral fever:
Rapid recovery
19. Treatment and Vaccines
As most human cases of RVF are relatively
mild and of short duration.
No specific treatment is required for
these patients.
In severe cases, the predominant
treatment is general supportive therapy.
Experimentally vaccine has been
developed for human use.
• However, this vaccine is not
licensed and is not commercially
available.
20. Prevention and control
Controlling RVF in animals
• Rift Valley Fever can be controlled by restricting or banning the
movement of livestock may be effective in slowing the expansion of
the virus from infected to uninfected areas.
• Animals can be prevented by a sustained programme of animal
vaccination.
Public health education and risk reduction
• Practicing hand hygiene, wearing gloves and other appropriate
individual protective equipment when handling sick animals or their
tissues or when slaughtering animals.
Infection control in health care settings
21. Prevention and control
Vector control:
Other ways in which to control the spread of RVF involve control of the
vector and protection against their bites.
RVF forecasting and climatic models: Forecasting can predict climatic
conditions that are frequently associated with an increased risk of
outbreaks, and may improve disease control.
Strategic larvicidal treatment of mosquito breeding habitats is
recommended.
