Presentation by Dr Mohamed Hassan of the Ministry of Agriculture, Kingdom of Saudi Arabia, at the Enhancing Safe Inter-regional Livestock Trade held at Dubai, UAE, 13-16 June 2011.

3. Rift Valley Fever
RVF
Enhancing Safe Inter-Regional Livestock Trade
Dubai, United Arab Emirates
June 13-16, 2011

4. Definition
• Rift valley fever (RVF) is an acute
febrile arthropod-borne zoonotic
disease. It is characterized by high
rates of abortion and neonatal mortality
in sheep, goats and cattle. It causes
hemorrhagic fever, encephalitis,
blindness and sever liver damage in
man.

6. Rift Valley - Kenya, Africa
• 1900’s: First recognized in sheep
• 1930: Agent isolated
• Intermittent outbreaks in Kenya
– 1950-51, major epizootic
• 500,000 sheep abortions
• 100,000 sheep deaths

7. Egypt: 1977-1978
• Humans
– 18,000 cases
– 598 deaths
• Encephalitis and hemorrhagic
fever
• Case-fatality less than 1%
• Ruminants
– Abortions and deaths
• Sheep, cattle, goats
• Water buffalo, and camels

8. Other Important Outbreaks
• 1987: Senegal, Africa
– Differed from other outbreaks
• Not associated with rainfall
• 1997-98: Kenya, Africa
– Largest outbreak reported
– 89,000 humans cases - 478 deaths
• 2000-01: Saudi Arabia and Yemen
– First outbreak outside of Africa
• 2003: Egypt
– 45 cases; 17 deaths; All cases were
Egyptian farmers

9. • Transmission

10. • Arthropod vector
– Mosquitoes
• Aedes
• Anopheles
• Culex
• Others
• Biting flies possible vectors

11. Other Modes of Transmission
• Direct contact or Aerosol
– Tissues or body fluids of infected animals
• Aborted fetuses . During slaughtering and necropsy
– High levels of virus in blood
• Aerosol
• Amplify virus
– Infect other mosquitoes
– Establish disease in environment
– May lead to large outbreaks
• No person-to-person transmission
– Humans are a possible source of virus for
mosquitoes

12. Reservoir
• Mosquitoes – Aedes species
– Transovarial transmission
– Eggs dormant in soil
for long periods
– Heavy rainfall, eggs hatch
• Ruminant amplifying host
• Secondary vectors can be infected
– Culex and Anopheles mosquito species
– Biting flies: midges, phlebotomids, stomoxids.

13. Amplifying Hosts
• Infected livestock
• High levels of viremia
• Amplifying
– Sufficient to infect mosquito vectors
– Establishes disease in environment
– Leads to large epizootic epidemics
• Humans
– Viremia enough to amplify

14. • Animals and Rift Valley Fever

15. Sheep and Goats
• Incubation period: less than 3 days
– High rate of abortion (5-100%)
• Any stage of gestation
– Asymptomatic
– Foul diarrhea, icterus, mucopurulent
nasal discharge
– Acute death (20-30%).

16. Lambs and Kids
• Incubation period: 12-36 hrs
• Newborn deaths
– High fever, listless, anorexia
– Death - 12 hours to 2 days
– Less than 1 week old
• Mortality >90%
• Lambs and kids over 2 weeks old
– Mortality over 20%

17. Cattle
• Adults
– Fever, weakness,
anorexia, ptyalism,
fetid diarrhea, icterus
– Death - Mortality 10%
– Abortion can be up to 100%
• Calves
– Similar signs to lambs and kids
– Mortality 10-70%

18. • Prevention and Control

19. Prevention
• Vaccination of ruminants by using attenuated
virus vaccine prepared from Smith burn
strain which prohibited in pregnant animals
as it causes birth defects and abortions.
• Avoid and control vectors
• Personal protective equipment
– Aborted fetuses, necropsy
• Avoid contact with infected tissues
and blood
• Restrict movement of animals
• Precautions when traveling

20. Control
• Do not slaughter sick animals
– Bury or burn carcasses during an outbreak
• Personal protective equipment
– Gloves, coveralls, boots, eyewear, mask
• Avoid contact with infected tissues and
blood
– Aborted fetuses, necropsy
• Greatest risk to travelers

21. Control
• Clean animal housing areas
– Wear personal protective equipment
– Remove all organic materials from
surfaces (manure, feed, animal tissue)
– Use soap or detergent with warm water
– Let dry
• Disinfect animal housing areas
– 1 part bleach:10 parts water

23. Attenuated tissue culture
vaccine
• Vaccination of lambs with
attenuated virus vaccine prepared
from Smith burn strain at age less
than 6 months.
• it is not safe to use for
vaccination of pregnant animals
as it cause abortion.

25. • Endemic in
tropical Africa
– Cyclic epidemics
every 5-20 years
– Abnormally heavy rainfalls
– Peaks in late summer
• Outbreaks
– Saudi Arabia, Yemen, and Egypt

26. Distribution of Rift
Valley Fever

27. Saudi Arabia and Yemen
2000-2001
• 683 humans hospitalized
• 95 deaths (13.9% mortality)
• 82.7% male
• Median age: 50 years
• Youngest patient:
14 yrs. old
• 76% had close contact with animals

28. • An epizootic of Rift Valley fever
was identified in southwest
Saudi Arabia following the
confirmation of cases in
humans in the third week of
September 2000. These were
accompanied by human disease
and abortions in the livestock in
the affected villages.

29. Arabian
Gulf

30. Control during outbreak
In response to the Rift Valley Disease
“RVD” out break, the Ministry of Agriculture
applied the following measures:
1. Restriction of animal movement in the
affected area which include Gazan, Asir &
Tohamet Makah. Restriction also included a
surveillance Zoon in NAJRAN and Baha
regions.
2. Massive vaccination of all livestock in the
infected area  Smith burn attenuated
vaccine.

31. 3. Control of mosquito
A- filling of ponds and marshes.
B- Rainwater drainage.
C- Biocontrol  bacillus thuringiensis H14.
D- Chemical control  pesticides.
Aerial and ground spraying by
mosquito pesticides  codified
E-Assess the efficiency of mosquito
control  mosquito traps.

32. Control after the outbreak
After the end of the epidemic the program
continued with the following measures:
• Vaccination of animals at 6 month old.
• Active disease surveillance for suspected
cases in live stock (flocks with abortion
and or early newborn mortalities).
• Clinical and serological testing of
suspected smuggled animals at Al-Twal
quarantine station on the border with
Yemen Republic.

33. • Regular examination and serological testing
of sentinel herds distributed in different
localities of the infected zone.
• During the rainy season (August-October)
random serum samples from susceptible
animal were examined by both capture
ELISA kits for (IgM) and (IgG) RVF
antibodies for detection of early infection
"IgM" and monitoring the level of immunity
due to vaccination (prevalence study),
• Rt-PCR was also used for RV virus
detection in periodically collected
mosquitoes.

34. • Restriction of Animal’s movements:
Measures to control the transmission of
infected animals from infected regions to
other regions includes:
- Quarantine of animals for 30 days.
- Animal Marking.
- Testing animal’s serum for antibodies (IgG).
- Vaccination of animals within 7 days.

35. Post Epidemic Records Shows that
All the reported virus activity “ were Less
than 1%, which considered as a
characteristic features of RVFV epidemiology
in previously infected areas during the inter
epizootic period and prove the maintenance
cycle of the virus infection.
Studies showed no other foci of the
disease in non-infected regions (sentinel
studies)

36. * For this reason RVF disease control
program continued :
Mainly to increase the level of
animal immunity and increase
awareness of animal breeders
about the importance of
vaccination.