Biological agents

1. Chapter 5: Agents of Environmental Disease
1. Biological agents of diseases

2. Learning objectives
1-Vector borne disease (they need to come from someone to you)
1) Malaria (Parasite)
2) Leishmania (Parasite)
3) Plague (Bacteria)
4) Lyme disease (Bacteria)
2-Zoonoses (From the zoo of the animals)
1) Avian Influenza Virus
2) Ebola Virus
3) Hantaviruses

3. Spread of Disease
Endemic: ”Constant presence of a disease or infectious agent
within a given geographic area. The usually prevalence of a
given disease within such an area.” Not everywhere only in one
place where the disease is well known.
Epidemic: “Occurrence in a community or region of cases of an
illness or outbreak clearly in excess of expectancy.”
Pandemic: ”Occurring over a wide geographic area and
affecting an exceptionally high proportion of the population,
i.e. malaria.” All of the place like covid-19.

4. 1-Vector borne disease

5. Vector borne diseases:
Vector-borne diseases are human illnesses caused by
parasites, viruses and bacteria that are transmitted by
vectors.
Most of the time they are flies.
Vector :
A carrier, especially the animal (usually an arthropod)
that can transfer an infective agent from one host to
another.
Remark: Arthopods are over three-fourths of all
currently known living and fossil organisms
Definition of Vector borne disease:

6. 1-Malaria
Malaria is a serious and sometimes
fatal disease caused by a parasite
that commonly infects a certain type
of mosquito which feeds on humans.
Globally, the World Health
Organization estimates that in 2019,
229 million clinical cases of malaria
occurred, and 409,000 people died of
malaria, most of them children in
Africa. Because malaria causes so
much illness and death.

7. How is malaria transmitted?
Usually, people get malaria by being bitten by an infective
female Anopheles mosquito. Only Anopheles mosquitoes can
transmit malaria and they must have been infected through a
previous blood meal taken from an infected person.
malaria can also be transmitted through blood transfusion,
organ transplant, or the shared use of needles or syringes
contaminated with blood.
Malaria may also be transmitted from a mother to her unborn
infant before or during delivery (“congenital” malaria).
Is malaria a contagious disease?
No. Malaria is not spread from person to person like a cold or
the flu, and it cannot be sexually transmitted.
‫المالريا‬
‫ليس‬
‫مرض‬
‫معدي‬
‫النه‬
‫ينتقل‬
‫عبر‬
‫الدم‬
‫فقط‬
‫ليس‬
‫الكحه‬
.
‫معدي‬
‫من‬
‫بطن‬
‫االم‬
‫اذا‬
‫كان‬
‫الطفل‬
‫في‬
‫بطن‬
‫االم‬

8. symptoms of malaria?
Symptoms of malaria include fever and
flu-like illness, including shaking chills,
headache, muscle aches, and tiredness.
Nausea, vomiting, and diarrhea may
also occur. Malaria may cause anemia
and jaundice (yellow coloring of the skin
and eyes)
https://www.youtube.com/watch?v=OEDhe4MPEMc

9. 2-Leishmania
Leishmaniasis is a parasitic disease that is
found in parts of the tropics, subtropics,
and southern Europe.
Leishmaniasis is caused by infection with
Leishmania parasites, which are spread by
the bite of phlebotomine sand flies.
We find it in a trophical areas.

10. Leishmaniasis is a vectorborne disease that is
transmitted by sand flies and caused by
obligate intracellular protozoa of the genus
Leishmania..

11. Leishmaniasis
Leishmaniasis cycle

12. 3-Plague
Plague is a disease that affects humans and other mammals.
It is caused by the bacterium, Yersinia pestis.
Humans usually get plague after being bitten by a rodent
flea that is carrying the plague bacterium or by handling an
animal infected with plague.
 Plague is infamous for killing millions of people in Europe
during the Middle Ages. Today, modern antibiotics are
effective in treating plague.
 ‫مرض‬
‫الطاعون‬

13. Transmission
The plague bacteria can be transmitted to humans in the following
ways:
Flea bites. Plague bacteria are most often transmitted by the bite of
an infected flea.
Contact with contaminated fluid or tissue. Humans can become
infected when handling tissue or body fluids of a plague-infected
animal.
Infectious droplets. When a person has plague pneumonia, they may
cough droplets containing the plague bacteria into air. If these
bacteria-containing droplets are breathed in by another person they
can cause pneumonic plague.
‫مرض‬
‫معدي‬
‫يأثر‬
‫في‬
‫الصدر‬
‫عن‬
‫طريق‬
‫الكحه‬
Inside
betwee
n the
mice
only
With
different
animals

14. Symptoms
Plague can take different clinical forms, but the most common are bubonic,
pneumonic, and septicemic.
Bubonic plague: Patients develop sudden onset of fever, headache, chills,
and weakness and one or more swollen, tender and painful lymph nodes
(called buboes).
Septicemic plague: Patients develop fever, chills, extreme weakness,
abdominal pain, shock, and possibly bleeding into the skin and other organs.
Skin and other tissues may turn black and die, especially on fingers, toes, and
the nose.
Septicemic plague can occur as the first symptom of plague, or may develop
from untreated bubonic plague. This form results from bites of infected fleas
or from handling an infected animal.
Pneumonic plague:may develop from inhaling infectious droplets or may
develop from untreated bubonic or septicemic plague after the bacteria
spread to the lungs Patients develop fever, headache, weakness.

15. 4-Lyme disease
Lyme disease is the most common vector-
borne disease in the United States. Lyme
disease is caused by the bacterium Borrelia
burgdorferi and rarely, Borrelia mayonii. It is
transmitted to humans through the bite of
infected blacklegged ticks.

16. Signs and Symptoms (days to months after tick bite)
Severe headaches and neck stiffness.
Arthritis with severe joint pain and swelling, particularly the
knees and other large joints.
Intermittent pain in tendons, muscles, joints, and bones.
Heart palpitations or an irregular heart beat (Lyme carditis).
Episodes of dizziness or shortness of breath.
Inflammation of the brain and spinal cord.
Nerve pain.
Shooting pains, numbness, or tingling in the hands or feet.

17. 2-Zoonoses

18. Definition Zoonotic Disease:
A zoonosis is an infectious disease that has jumped from a
non-human animal to humans. Zoonotic pathogens may be
bacterial, viral or parasitic.
There are over 200 known types of zoonoses.
Zoonoses comprise a large percentage of new and existing
diseases in humans.
Some zoonoses, such as rabies, are 100% preventable
through vaccination and other methods.
•Avian Influenza
•Severe Acute Respiratory Syndrome
(SARS)
•Monkeypox virus
•Rabies virus
•Brucellosis
•West Nile virus
•Nipah virus
•Bovine tuberculosis (mycobacterium
bovis)

19. • Approximately 75% of recent emerging infectious diseases have
been zoonoses
Ebola Virus Hantaviruses
Avian Influenza Virus

20. 1-Ebola
Viral: EBOLA Virus caused by Filo virus and other African Hemorrhagic
Fevers. These are marked by severe bleeding, organ failure and often
death.
**One of the most pathogenic viruses known to science, causing 50-90%
fatalities in all clinically ill cases.
Its has the capability to go through the immune systems, that’s why its could kill
about 90% of people.

21. Ebola
This virus lives in animal hosts and can be contracted through contact
with blood and waste products.
It is then spread through person
to person contact with body fluids
or contaminated needles of those
infected.
Cases of transmission included direct contact with blood, secretions,
organs or semen of infected persons and by handling ill or infected
chimps.

22. Ebola
Symptoms: Fever, weakness, muscle pain, headache, sore throat. Then
vomiting, diarrhea, rash, limited kidney and liver functions & both
internal & external bleeding.
Incubation:2-21 days, 5th day: hemorrhagic symptoms
Fatality: 50-90%
Treatment: Supportive care.
https://www.youtube.com/watch?v=3IFX9LHcnyg

23.  Hantaviruses are a family of viruses
spread mainly by rodents and can cause
varied disease syndromes in people
worldwide.
 Each hantavirus serotype has a
specific rodent host species and is
spread to people via aerosolized virus
that is shed in urine, feces, and saliva,
and less frequently by a bite from an
infected host.
2-Hantaviruses

24. Signs &
Symptoms
Early Symptoms
Early symptoms include fatigue, fever and muscle aches, especially in the large
muscle groups—thighs, hips, back, and sometimes shoulders. These symptoms are
universal.
There may also be headaches, dizziness, chills, and abdominal problems, such as
nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients
experience these symptoms.
Late Symptoms
Four to 10 days after the initial phase of illness, the late symptoms of HPS appear.
These include coughing and shortness of breath, with the sensation of, as one survivor
put it, a “…tight band around my chest and a pillow over my face” as the lungs fill with
fluid.
Is the Disease Fatal?
Yes. HPS can be fatal. It has a mortality rate of 38%.

25. 3-Avian Influenza
 20th century pandemics:
 1918 (~50 million deaths globally)
 1957 (~1 million)
 1968 (~750,000)
 1997: currently circulating H5N1 strain

26. Avian Influenza
• Influenza A, H5N1
• Extensive list of susceptible hosts
• Currently Bird  Bird and Bird  human transmission
• No demonstrated, sustained human to human transmission to
date

27. Avian Influenza
• Pandemic potential:
– Rapid viral mutation rates
– Recombination event between HPAI and seasonal flu
• Pandemic influenza poses significant public health risk
– No pre-existing immunity to H5N1 in human population
– Isolates have demonstrated some anti-viral resistance
– Vaccine has been developed, but may not cover pandemic strain
– Difficulty of containment
• Projected Pandemic Costs:
– 10-180 million deaths worldwide
– Economic Impact: 2-3.1 % of global GDP (>2 trillion USD) (World Bank)

28. Cull (FAO)
a selective slaughter of
animals
Vaccination
(FAO)

29. Tools:
Community Based Surveillance
• Train community members to detect and report cases using standard
diagnostic criteria
• Strengths:
– Improves diagnostic sensitivity
– Allows real-time ongoing monitoring with minimal resources at minimal cost
– Fosters community education and awareness
• Weaknesses:
– First stage in outbreak detection: laboratory or health worker confirmation
needed
– Requires good communication/chain-of-command

30. Tools:
Outbreak Control and Response
• Confirmatory Diagnosis
• Case Identification
• Quarantine and perimeter control
• Livestock culls and destruction of contaminated livestock
products
• Compensation
• Disinfection of premises
• Vaccination Decisions

31. The Way Forward
• Understanding the complex factors that lead to disease
emergence
– Social (poverty & instability).
– Economic (livestock & wildlife trade).
– Environmental (ecosystem degradation & climate change).
• Improve data collection/analysis/sharing.
• Empower communities to proactively monitor and rapidly respond.
• Multi-disciplinary approach.