This presentation will show you the risk analysis procedure

1. CVASUChittagong
Veterinary &
Animal Sciences
University
Bangladesh
Risk Analysis on West Nile
Virus infection in Bangladesh
Dr. Md. Abu Sayeed
Course: Risk Analysis and Policy Making
Roll: 0214/04; Regi no: 212
Session: 2014-15
MS in Epidemiology (Fellow)
Dept of Medicine & Surgery
Chittagong Veterinary & Animal Sciences University

2. CVASU
West Nile Virus
• West Nile virus (WNV) is an
arthropod-borne flavivirus
transmitted to humans and
horses by the bite of an
infected mosquito. West Nile
Virus (WNV) is also belongs
to the Japanese encephalitis
antigenic complex of the
family Flaviviridae.

3. CVASU
Discovery
• In 1937; West Nile virus was first isolated from the
blood of a febrile woman from the West Nile region
of Uganda (Smithburn et al, 1940).
• In 1950; WNV isolates were obtained from the
blood of three apparently healthy children in Egypt
(Melnick et al, 1951).
• In the summer of 1999; West Nile virus was
recognized in the western hemisphere for the first
time when it caused an epidemic of encephalitis
and meningitis in the metropolitan area of New
York City, NY, USA.

4. CVASU
Distribution of WNV
Source: http://ecdc.europa.eu/en/healthtopics/west_nile_fever/West-Nile-fever-maps/Pages/index.aspx
Russia
Eastern
Europe
Middle East
North America
Africa

5. CVASU
Vector
• WNV has been isolated
from more than 40
mosquito species
• Culex antennatus, Culex
univittatus, Culex pipiens,
Culex nigripalpus, Culex
salinarius, Culex restuans
and Culex
quinquefasciatus
Host
• Reservoir Hosts
– migratory Passeriformes
(perching birds/songbirds)
– Strigiformes (owls)
– Falconiformes (hawks)
– Charadriiformes
(shorebirds)
– Alligators and Lake Frogs
• Incidental Hosts
– Horse
– Human

6. CVASU
Mode of Transmission
• Direct biting by mosquito
• Additional transmission routes
– trans-placental and breast milk transmission
– infected blood transfusion and organ
transplantation
– urinary excretion of the virus (human)
– experimental oral transmission (birds)
(King et al, 2007).

7. CVASU
Transmission Cycle

8. CVASU
Pathogenesis in Incidental Host
Inoculation into the skin Langerhans cells lymph nodes
LymphaticsDifferent tissues
Thoracic duct
Bloodstream

9. CVASU
Encephalitis form
• The exact mechanism by which encephalitic flaviviruses
enter the central nervous system (CNS) is unclear.
• High viremia, development of brain infection and
appearance of viral antigen in nervous tissue leads to
the hematogenous spread into the CNS.
• Artificial disruption of the blood-brain barrier (by
underlying infection) may also lead to encephalitis and
neuroinvasion. Mainly olfactory neuronal infection has
also been suggested as a route of neuroinvasion.
• The incubation period is usually 3 to 14 days

10. CVASU
Signs and symptoms
• About 80% cases infection with WNV is either asymptomatic (no
symptoms) or severe West Nile disease.
• About 20% cases will develop West Nile fever. Symptoms include
– fever
– vomiting
– occasionally skin rash with swollen lymph glands.
• The symptoms of as West Nile encephalitis include
– high fever
– neck stiffness followed by disorientation
– coma, tremors, convulsions, muscle weakness, and paralysis.
• In case of human, serious illness can occur in any age, however
people over the age of 50 and some immunocompromised persons
are at the highest risk.
• Approximately 1 in 150 persons infected with the West Nile virus will
develop West Nile encephalitis.

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Diagnosis
ELISA Neutralization assays
Virus isolation by cell culture

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Treatment
Hospitalization Intravenous fluids
Respiratory supportAntibiotics
Supportive
Therapy

13. CVASU
Risk Question
• What is the probability of introducing
West Nile virus in Bangladesh
through an infected host (mammal,
avian or insect) from current affected
countries?
• What is the probability of West Nile
virus becoming established in
Bangladesh in the local mosquito
and avian population?
• What is the probability of a
Bangladeshi resident horse
becoming infected with West Nile
virus given contact with an infected
host?

14. CVASU
Risk Assessment Indicators
• Presence of the vector species
• Abundance and dynamics of vector and
reservoir hosts population
• Detection and/or isolation of the virus and
mosquito infection rate
• Characterization of viral strains by sequencing
• Identifying the larval habitats, adult resting
places and flight activity of the detected
vector species

15. CVASU
Key starting assumptions
• Undisclosed infection may be present in live
equidae that may be imported to Bangladesh via
legal trade or illegal movements from the currently
known affected areas;
• The virus may also enter in Bangladesh via
migratory wild birds or by infected vectors being
brought in by prevailing winds or some other
means;
• Favorable ecological conditions may exist in
Bangladesh and would support the establishment
and further spread of the virus should it be
introduced.

16. CVASU
Risk Pathway
Migratory
Birds
Legal and illegal
movement from
affected countries
Accidental import
of biological
vectors
Live
equidae
Live poultry /
captive birds
Non-Avian
non-Equidae
species
Research
Samples
Tourists
No riskIntroduction of disease into
human population of Bangladesh
Possible conceptual pathways for the introduction of WN
virus in Bangladesh from the currently known affected areas

17. CVASU Release Assessment
Major birds are water birds
like Black faced spoon
bill and Spoonbilled
Sandpiper
Not act as reservoir host
for WNV (CDC: 99-12)
Negligible
•Good quarantine facility and less importation of horses
•Presence of good Vector (Mosquitoes) control strategy
and less horse population

18. CVASU
Exposure Assessment
• Horses and humans are dead-end hosts with very low
short lived viremia and therefore even if an infected
horse or human arrive in Bangladesh, it would not be
involved in onward transmission.
• An infected wild bird arrive in Bangladesh, the
potential for WNV transmission to a competent vector
in Bangladesh would be determined by potential for
contact with and the abundance of competent vectors.
• WNV competent vectors of several Culex spp. are not
available in Bangladesh

19. CVASU
Consequence Assessment
• Therefore a good quarantine system of
Bangladesh with low horse population in
the area as well as lack of competent
migratory birds and vectors lead the
introduction of WNV is in negligible
condition.
Release status= Negligible
Exposure status=Negligible
Probability (P)= Release × Exposure
= Negligible × Negligible
= Negligible

20. CVASU
Risk Management
• Surveillance activities
– Human: passive surveillance
– Veterinary: passive surveillance for horses and migratory birds with
vector control strategy
• Suggested public health actions and interventions
• Health sector
– Increase awareness amongst healthcare professionals about WNV so
as it will be considered in the differential diagnosis of travelers returning
from affected areas.
• Education of travelers to affected areas on how to reduce the risk.
• Ensure there are laboratory capabilities within the country for
diagnosis.
• Ensure Gov. and others donation authorities have implemented
measures to prevent transmission through travelers returning from
affected areas

21. CVASU
Risk communication
• Communicating risk assessment results and
explanation of the risk management measures
• Health care professionals and Veterinarians
• Local Law enforcing authority
• Mass media
• Government and Non-Government disease
control authority
• CDC, USA

22. CVASU
Conclusion
• The release and exposure of WNV in
Bangladesh is negligible. So, don’t need to
drop it or take it seriously. Only sincere
activities should develop for preventing
this infection in our country.

23. CVASU
Acknowledgement
• My supervisor
– (Prof. Ahasanul Hoque, Dean FVM)
• All Epi members CVASU

24. CVASU
References
• http://ecdc.europa.eu/en/healthtopics/west_nile_fever/ris
k-assessment-tool/Pages/risk-assessment-tool.aspx
• http://ecdc.europa.eu/en/healthtopics/west_nile_fever/ris
k-assessment-tool/Pages/risk-assessment-tool.aspx
• http://scholarcommons.usf.edu/cgi/viewcontent.cgi?articl
e=1437&context=etd
• Mainali et al. Journal of Medical Case Reports 2011,
5:204http://www.jmedicalcasereports.com/content/5/1/20
4
• http://www.who.int/mediacentre/factsheets/fs354/en/
• https://www.michigan.gov/documents/Cooleywnvinwildlif
e_77045_7.pdf

25. CVASU

26. CVASU