Presentation by Dr Peter Ithondeka, Director of Veterinary Services,Kenya, at the Enhancing Safe Inter-regional Livestock Trade workshop held at Dubai, UAE, 13-16 June 2011.

1. Practical Considerations in the Control of
a Rift Valley Fever Epizootic
Presented at OIE Regional Conference Nairobi
SAMAYA HOTEL UNITED ARAB EMIRATE
by
Dr Peter Maina Ithondeka PhD, MBS
Director of Veterinary Services, Kenya
14th June 2011

2. Introduction
 Rift Valley Fever (RVF) is a viral haemorrhagic disease
primarily of cattle, sheep, goats, camels, wildlife and
humans
 Spread: - Aedes mosquitoes, other blood-sucking
insects and through skin abrasions
 Maintenance of virus between outbreaks remains
unclear
 One of the most significant zoonotic disease
problems in Africa
 The haemorrhagic human disease syndrome
generates a high degree of panic among the human
populations at risk

3. RVF occurrence in Kenya
• A disease fitting RVF description was first described in
Kenya in 1912 by Montgomery.
• It is believed that the disease might have occurred in
1913 because an outbreak fitting the description of RVF
was associated with heavy mortalities of sheep in the
Rift Valley (Bres, 1981).
• Described as a specific viral entity in 1931
• Since then the disease has occurred in 5-15 year cycles
– 1926, 1931, 1936, 1944, 1951, 1960/63, 1967/68,
1978/79, 1997/98 and 2006/07
• Refer to MS Word tabulation of outbreaks

4. RVF antibody to virus studies in camels
• Study carried out in 1979 after the 1978/79
RVF epizootic in Kenya (Davis, Koros and
Mbugua, 1984)
• 571 camel sera samples were collected and
analysed
• 22% of these had high titers of the RVFV
neutralizing antibodies

5. RVF antibody to virus studies in birds
–Carried out in 1979 using 171 bird sera
(Davies, 1979)
–Study was to check if RVF produced
viraemia or neutralizing antibodies in birds
–Only 3 of Ploceus weavers tested
contained specific antibodies to RVF

6. Role of primates in spread of RVF
• To find the natural reservoir to RVF has been the
subject of several studies
• Smithburn et al.,(1948) failed to detect antibodies in
sera from 72 wild monkeys trapped in Uganda in an
area where RVFV was isolated in mosquitoes
• Pellisier&Rousselet (1954) reported the presence of
antibodies in 12 out of 122 monkeys kept in captivity
in Brazzaville

7. Role of primates in spread of RVF(2)
• Davies et al.,(1972) failed to detect antibodies from
baboon (Papio anubis) in Kenya most of which were
from an area where an epizootic of RVF had recently
occurred
• Davies et al.,(1975) failed to detect antibodies in
1304 velvet monkeys) in Kenya most of which were
again from an area where an epizootic of RVF had
recently occurred

8. RVF antibody to virus studies in wildlife
 Study carried out in 2007 on 896 sera collected from
16 Kenyan wildlife species (Evans et al., 2007)
 Specimen from 7 species had detectable neutralizing
antibodies against RVFV i.e. African buffalo, black
rhino, lesser kudu, impala, African elephant, Kongoni
and waterbuck.

9. Flooded Dambo North Eastern Province, Kenya

10. Number of RVF outbreaks in Kenya from 1912-2002 (5-15 year cycles)
45
40
35
No.of outbreaks
30
25
20
15
10
5
0
12
31
51
60
62
64
67
69
71
78
83
89
91
93
98
02
19
19
19
19
19
19
19
19
19
19
19
19
19
19
19
20
Year

11. contingency plans
• Preparedness planning, including the
development and approval of contingency
plans
• Prior approval of plans will allow decisions to
be made at a political level more rapidly

12. Response to the 2006/07 RVF outbreak
 Veterinary department formed a technical
committee to advice on control strategy
 The committee composed of experts from other
institutions, development partners, ministry of
health and Meteorological department.
 Departmental management committee for
coordination of activities for prevention and control
of RVF
 Zoonotic committee composed of CDC, MOH, FAO,
Veterinary Department and WHO

13. 1. Quarantines and slaughter bans
 Quarantines were imposed in infected districts (livestock
movement controls)
 Livestock slaughterhouses were closed and home slaughters
banned
 Enforcement of quarantine/slaughter bans was through
education, use of imams and other law enforcers
 The quarantine and slaughter bans were lifted based on
absence of clinical disease
 preventive action by moving livestock to high altitude areas to
avoid Aedes infested areas

14. 2006/2007 Outbreak: Intervention
activities
1. Quarantines and
slaughter bans
2. Surveillance
3. Vaccination
4. Vector control (insect
repellants, sythetic
pyrethroids)
5. Public education and
awareness

15. 2. RVF Surveillance in livestock
• Immediately carried out in districts adjacent to
the outbreak area to determine the spread
• Later extended to areas with known endemic foci
- based on
– Previous infections
– Areas ecologically conducive for vector
habitation e.g. thick vegetation cover, swampy
and flooded grounds
• Veterinary field personnel continuously searched
for the disease and collected samples

16. RVF Surveillance in livestock (2)
• In cattle, sheep, goats and camels assessment
of titers of anti–RVF virus IgM antibody
relative to anti–RVF virus IgG antibody can be
used to differentiate recent from historical
RVF virus infection.
• This is because the duration of detectable
anti-RVF IgM antibody in these animals is
transient, approximately 60 to 90 days (Bird et
al.,2009)

17. 2006/2007 Outbreak: RVF surveillance sites
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0 300 Kilometers N
W E
S

18. 2006/2007 RVF wildlife surveillance
• Serum samples collected
from buffaloes, Giraffes,
warthogs, Elands,
Gerenuks
• Surveillance done in
areas where outbreaks
had occurred
• Opportunistically during
Rinderpest surveillance
• In all areas where
unusual wildlife deaths
were reported

19. Distribution of sentinel herds to
monitor disease
# Japata
Salabani
# #
Ngambo # Shantabak
# Naivasha
Marey
## Sangailu
Kotile#
#
Bachuma
N
W E
S
200 0 200 400 Kilometers

20. 3. Vaccination against RVF
• Vaccinations were carried out in goats, sheep, cattle and
camels
• Started in January 2007 in the North Eastern Province
• Later focus shifted to known endemic districts
• A total of 2,550,300 doses of RVF vaccine were used in
control efforts
• Type of vaccine: Smithburn live attenuated vaccine

21. 2006/2007 Outbreak: Vaccinated areas
N
W E
200 0 200 Kilometers
S

22. 4. Vector control
• Reduction of vector population using
insecticides (pyrethroids) on livestock –- pour-
on preparations and spray wash
• All herds visited were treated
• A total of 5,890 liters of insecticide Pour-on
preparation and 632 liters of insecticide spray
were used in 14 districts as part of integrated
RVF vector control activities.

23. 5. Public awareness and training
 Press conferences
 Ministers for Livestock and Fisheries Development and
Health
 DVS on the updates of the disease
 Radio interviews to educate , inform the public
and increase compliance with legal requirements
 Newspaper advertisements, brochures, radio
announcements and television infomercials
 Training of department field staff on RVF
recognition, surveillance and bio- security
measures

24. Impacts of RVF outbreak
• Financial losses due to:
– Livestock deaths
– Abortions
– Trade restrictions
– Slaughter restrictions
• Food insecurity
• Decreased demand and prices of meat
• Loss of stock

25. Decision Making Tool for Kenya
 The department of veterinary services has come
up with a contingency plan for RVF outbreaks in
Kenya.
 This plan covers issues such as:
 RVF preparedness protocols
 Surveillance protocol (including sentinel herd)
 Personal protection protocol
 SOPs for sample collection and storage
 SOPs for RVF laboratory bio-safety

26. Contingency plan in RVF control
 Pre-outbreak protocols
 Monitoring of weather patterns
 Passive surveillance
 Rumor and outbreak investigation
 Management, maintenance and monitoring of sentinel
herds
 Risk analysis
 Maintenance of RVF database
 Outbreak protocols
 Risk assessment
 Active surveillance
 Collection of samples
 Wildlife surveillance
 Investigating of disease reports

27. Decision Making in RVF control (2)
 RVF simulation protocol
 Vaccination protocol
 Vector control protocol
 Protocol on imposition and management of RVF
quarantine measures
 Protocol for RVF outbreak communication

28. Phased out decision making
• based on using key events as triggers or decision
points for partial responses reduce the risk of
inappropriate decisions and assure better
preparation.
• decision-making process involves balancing the lack
of perfect information with the need to take a
decision to avert losses due to failure to take action.
• If the decision is taken too early with scant
information, the likelihood of taking a wrong decision
is increased and costs will result from inappropriate
or unnecessary activities.

29. Phased out decision making (2)
• if a decision is taken too late, the opportunity to
intervene effectively may be lost.
• Thus, the decision-maker has to balance the risks of
over-reacting against those of under-reacting.
• effectiveness of phased decision making rests heavily
on the trust of its predictive value.

30. RVF hot spots vaccination strategy
• Kenya currently adopts vaccinations in the
known RVF hot spots when never the flooding
is predicted.
• However, it is difficult to gauge the ideal point,
in terms of information availability, where a
decision should be taken.

31. Cumulative RVF Vaccination
Year Doses
• 2007 2,077,000
• 2008 1,500,000
• 2009 1,199,600
• 2010 600,000
• Vaccinations have been carried out in RVF
outbreak hotspots.

32. Time lines based on DVS/ILRI 2007 study
Risk Factors Cases Response
Rains Vectors Livestock Human Human Vet
33.1 days 19.2 days 21 days 35.6 days 12.3 days 68.9 days

34. Thank you for Listening