Vectors borne diseases 1

This lecture was given as a part of the Introduction to Epidemiology & Community Medicine Course given for third-year medical students.

1. Major vectors-borne diseases in
KSA(1): Viral Hemorrhagic Fevers

2. Objectives
Define vectors and vector-borne diseases.
List the common vectors that can transmit
infectious diseases to human.
Define and discuss the importance of Viral
Hemorrhagic Fevers(VHFs).
Discuss the epidemiology of viral H fevers in KSA.
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3. Vector-borne Diseases-
(Introduction)
Vector-borne diseases are considered the most
serious diseases.
The seriousness of vectors because of their ability
to transmit the disease at a large scale in shorter
time, than other infectious diseases that
necessitate human-to-human contact.
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4. Vector-borne Diseases-
(Introduction)
Vectors can transmit diseases among different
living beings (mice, rats, monkeys, birds, dogs,
etc.) and humans.
Treatment of vector-borne diseases is difficult,
and the prevention essentially necessitates the
elimination of the vector.
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5. Vector-borne Diseases
What are vectors?
Vectors are living organisms that can transmit
infectious diseases between humans, or from animals to
humans.
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6. Vector-Borne Biseases
Vector-borne diseases:-
 Are the diseases caused by disease-vectors.
Often found in tropical regions, where insects prevail,
and access to drinking water and sanitation is not safe.
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7. Disease-vectors
The common vectors that can transmit infectious
diseases to human are:-

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Vector Disease Transmitted(E.g.)
1- Mosquito Malaria, viral hemorrhagic fever(yellow fever and dengue
HF).
2- housefly Typhoid ,diarrheal diseases ,cholera ,poliomyelitis
,conjunctivitis ,… etc.
3- louse(lice)Epidemic typhus ,Relapsing fever
4- sand fly Kala-azar
5- Hard tickTick typhus ,viral encephalitis ,viral hemorrhagic fever.
6- Itch-miteScabies
7- tsetse flySleeping sickness

8. Mosquito
Constitute the most important vector from all vectors
that transmit disease to human.
They are found all over the world.
The four important groups of mosquitoes which are
related to disease transmission are:-
1.1.Anopheles.Anopheles.
2.2.Culex.Culex.
3.3.Aedes.Aedes.
4.4.Mansonia. Mansonia.
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9. Mosquito-borne diseases
Type of mosquito Disease
1- Anopheles. Malaria
2- Culex West Nile fever
3- Aedes Yellow fever
Dengue , Dengue hemorrhagic fever
Rift valley fever.
4- Mansonia Malayan filariasis.
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10. Viral Hemorrhagic Fevers(VHFs)
VHFs refers to a group of diseases, Caused by several
families of viruses that affect humans and animals.
characterized by:-
oAcute febrile syndrome.
oHemorrhagic manifestations.
oHigh mortality rates.
oEndemic in certain geographical regions.
oSometimes cause major outbreaks.
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11. Viral Hemorrhagic Fevers(VHFs)
The VHFs include infections caused by viruses of the
families :
Flaviviridae (dengue fever, yellow fever, Omsk
hemorrhagic fever, Kyasanur Forest disease, Alkhurma
hemorrhagic fever [AHF]).
Bunyaviridae (Crimean-Congo hemorrhagic fever
[CCHF], Rift Valley fever [RVF], and Hantavirus
diseases).
Arenaviridae (Argentine, Bolivian, Brazilian, and
Venezuelan hemorrhagic fevers and Lassa fever),
Filoviridae (Ebola and Marburg hemorrhagic fevers).
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12. Viral Hemorrhagic Fevers in KSA
The history of hemorrhagic fevers in the Arabian
Peninsula refers to 19th century . The first
recorded outbreak of a dengue-like disease, which
occurred from 1870 to 1873.
Most outbreaks were reported in the :Tihamah
region—The Red Sea coastal plain in the west and
southwest of Saudi Arabia and Yemen.
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13. Viral Hemorrhagic Fevers in KSA
The most common in Saudi Arabia are:-
Dengue fever.
Rift Valley fever.
Alkhurma hemorrhagic fever.
And Crimean-Congo hemorrhagic fever
(CCHF).
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15. Dengue fever and dengue
hemorrhagic fever
 Are cosmopolitan vector-borne diseases.
Currently present in more than 100
countries.
And poses a public health threat to more
than 2.5 billion people worldwide.
With around 80 million people being
reported infected annually at an attack rate
of 4%.
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16. Dengue fever and dengue
hemorrhagic fever
Dengue virus is the most common arbovirus infection that
belongs to the family Flaviviridae/genus Flavivirus .
Can be transmitted by the bite of infective female
mosquitoes of the species Aedes aegypti ; and, to a lesser
extent, A. albopictus.
There are four serotypes dengue virus (DENV1–4).
But infection with one of them does not provide cross-
protective immunity against the other serotypes.
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17. Dengue fever and dengue
hemorrhagic fever
After an incubation period of two to five
days, dengue virus may cause:
Mild flu-like illness.
Or quickly progresses to serious dengue
hemorrhagic fever–dengue shock syndrome.
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18. Dengue fever and dengue
hemorrhagic fever in KSA
In the some parts of Saudi Arabia, Dengue fever
has:
Major effect on human populations' wellbeing.
 And the country's economy.
Specifically in Jeddah city, which is one of the
main entry points to Saudi Arabia.
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19. History of Dengue in KSA
In 1990 an outbreak was reported for the first time in
Jeddah.
From 1994 to 2002,the refer laboratory in Jeddah reported
319 cases.
Next , two peaks were reported in 2005/2006,and another
two in 2008.
Dengue is now endemic in the western and southern
regions of KSA.
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20. Alkhurma hemorrhagic fever
Alkhurma hemorrhagic fever is caused by Alkhurma
hemorrhagic fever virus (AHFV) which is :-
A tick-borne encephalitis Flavivirus .
Can be transmitted by the bite of soft and
hard ticks (found in camels and sheep) .
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21. Alkhurma hemorrhagic fever
Alkhurma hemorrhagic fever virus (AHFV) :-
It was first isolated in Saudi Arabia and described
as a unique viral agent of Arabian Peninsula .
Significantly, AHFV shares a high similarity with
Kyasanur Forest disease virus, which was isolated in
India
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22. Alkhurma hemorrhagic fever
AHF is a zoonotic disease and clinical cases
have been attributed to exposure to
livestock (camels and sheep).
AHFV is not isolated yet from such
animals.
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23. Alkhurma hemorrhagic fever
After an incubation period of two to four days, the
disease presents initially with nonspecific influenza
like symptoms, including fever, anorexia, malaise,
diarrhea, and vomiting.
A second phase includes neurologic and hemorrhagic
symptoms in severe form.
Multi-organ failure leads to fatal outcomes.
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24. Alkhurma hemorrhagic fever
in KSA
It was isolated for the first time in 1995 in Jeddah from six
patients in Alkhurma district .
Since its first description, several hundred cases have been
reported in different western Saudi governorates.
AHFV was identified in Mecca from 2001 to 2003.
Several sporadic cases were recorded in Najran from 2003
to 2009.
Cases peaking in spring and summer.
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25. Bobbie Rae Erickson (center, in black) of CDC's Special Pathogens
Branch meets with Saudi and other scientists near a goat pen to learn
about Alkhurma virus transmission in livestock.
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26. Pierre Rollin (center) and Adam MacNeil (right) of CDC's Special
Pathogens Branch inspect a camel for ticks carrying the Alkhurma
virus.
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27. Crimean-Congo hemorrhagic fever
CCHF is caused by infection with a tick-borne
virus Nairovirus.
It is the most widespread tick-borne viral infection of
humans.
And the second most widespread of all medically
important arboviruses after dengue viruses.
CCHFV causes a subclinical disease in most livestock.
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28. Crimean-Congo hemorrhagic fever
CCHF virus was first recognized in Crimea in southeastern
in the mid-1940s and named Crimean hemorrhagic fever .
Then, it was isolated in Congo in 1969.
Thus resulting in the name of the disease.
Currently, CCHF is endemic in many countries in Africa,
Europe, and Asia.
The CCHF is related to Eid-al-Adha feast due to lack of
controlling livestock movements in and between countries
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29. Crimean-Congo hemorrhagic fever
in KSA
Outbreaks of CCHF have been reported in western
Saudi Arabia (1989–1990) .
It was suspected that the CCHF virus was introduced
to Saudi Arabia by infected ticks on imported
livestock (camels, cattle, sheep, goats, and buffaloes),
arriving to the Jeddah seaport.
The main risk factor was the exposure to the blood or
tissue of livestock in abattoirs, but not tick bites .
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30. Rift Valley fever
RVF is a vector-borne zoonotic disease .
Caused by a Phlebovirus .
RVF virus is:
Transmitted by Culex and A. aegypti mosquitoes.
 resulting in large epizootics in livestock, which causes
abortion in pregnant ruminants and rapid death in
neonates.
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31. Rift Valley fever
Humans are incidentally infected when:-
They are bitten by infected mosquitoes.
Contact with aborted or infected animal tissues.
Or drink unpasteurized milk.
RVF virus is also a potential bioterrorism agent.
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32. Rift Valley fever
Humans suffering from RVF suffer influenza-like
symptoms .
After the initial febrile stage, in some cases, can
develop into ;
hemorrhagic fever.
 encephalitis.
 and death.
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33. Rift Valley fever in KSA
RVF was historically restricted to the Africa.
In 2000, RVF virus caused two simultaneous outbreaks in
Yemen and Saudi Arabia.
On September 15, 2000, the US Centers for Disease
Control and Prevention (CDC) isolated RVF virus from
Saudi Arabia.
Saudi Arabia reported 882 human cases and 124 deaths.
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34. Prevention of vector borne
diseases
Precautions for Protection against Disease-vectors:
Fight the vectors that transmit such diseases, as well as the
places where their larvae exist, by using proper insecticides.
Removing things that could probably provide a place for
water rafting.
Putting on long-sleeved wears, and covering legs at places
where insects exist, and using insect repellants.
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35. Prevention of vector borne
diseases
Precautions for Protection against Disease-vectors:
 Using nets at doors and windows to prevent the entrance
of insects.
Using mosquito nets when sleeping outdoors.
Paying attention to the cleanliness of animals and animal
pens.
Maintaining personal hygiene .
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36. Prevention of vector borne
diseases
Precautions for Protection against Disease-vectors:
Avoiding travelling to the countries / places
stricken by vector-borne diseases
And making sure to take the necessary preventive
drugs and vaccines when travelling .
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37. References
Preventive and social medicine- k . PARK.
Epidemiology Leon Gordis .
https://www.cdc.gov.
https://www.moh.gov.sa.
https:// www.who.int.
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