ZOONOTIC DISEASE HISTORY

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ZOONOTIC DISEASE HISTORY
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Of the worlds new and emerging diseases,
approximately 75 are zoonotic!! These emerging
infectious diseases make the role of the
veterinary health care professional extremely
important! Veterinary health care
professionals help prevent disease in animals and
humans.
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Besides producing diseases in humans, zoonotic
diseases can affect the food chain for example
Brucellosis. The environment may also affect
zoonotic diseases. For example, changing
ecosystems have resulted in an increase in
tropical diseases. With the domestication of
animals, changing culture has played a role in
the development of zoonotic diseases. Human
disease itself has played a role in the increase
of zoonotic disease!!! With the increase of
immunosuppressive conditions and drugs
(chemotherapy and HIV) physicians are concerned
that their patients with pets may be more
susceptible to zoonotic disease.
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There are more than 150 known zoonotic diseases,
however fewer than ½ of them are clinically
significant. (Think The Black Plague,
tuberculosis, Lyme disease)
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Term Sentinel A domestic animal host for a
particular disease that is placed at various
locations to determine the potential for human
exposure to a particular disease.
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Chain of Infection Pathogen Susceptible Host
Reservoir Portal of Entry Portal of
Exit Mode of Transmission
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Reservoir an animate (living) or inanimate
(non-living) object that serves as a long-term
habitat and focus of dissemination for an
infectious agent. Living reservoirs include
humans, animals and arthropods (insects,
arachnids, crustaceans) Vector any live animal
that transmits an infectious agent from one host
to the next (typically used to describe
arthropods) Biological Vectors actively
participate in a pathogens life cycle, serving
as a place where the pathogen
multiplies or completes its life cycle.
Infectious agents are spread via
injecting infected saliva into blood, defecating
around the wound, regurgitating blood into
the wound bite, aerosol formation or
touch Ex mosquitoes, fleas, ticks
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Mechanical Vectors are not necessary for the
life cycle of the pathogen and are
passive participants in the transmission
of disease. Spread disease when their
external body parts become contaminated
through contact with the pathogen.
Transferred to human or animals indirectly by
an intermediate such as contaminated
food or directly by contact between the
contaminated body part and a mucous
membrane or skin surface Ex
houseflies, cockroaches
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Non living reservoirs air soil dust
food milk water fomites (objects that
are able to transfer disease organisms)
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Transmission Direct transmission the
immediate transfer of an infectious
agent from a reservoir to a susceptible
host Ringworm
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Indirect transmission the transfer of an
infectious agent carried from a
reservoir to a susceptible host.
West Nile Virus
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Direct and Indirect transmission occurs by a
variety of mechanisms Contact occurs
through touch and may be either direct or
indirect Ex a human touches the skin lesions
of a ringworm positive cat and then
transfers the ringworm. (direct) Ex a person
touches the skin of a ringworm-positive cat
then touches another cat transferring
the fungal spores to the second cat
that then gets ringworm (indirect)
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Airborne droplets of respiratory secretions
may contain pathogens and have the ability
to spread disease via aerosol. Ex sneeze
or cough from the infected animal to an
uninfected animal (direct) Ex
sneeze that contaminates a ventilation system
that eventually infects an animal/human
(indirect)
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Placental transmission occurs from mother to
offspring and is form of direct
transmission. Fomites (or vehicles) such as
animal bedding that have become
contaminated by blood, saliva, urine, feces,
vomit, exudates, respiratory secretions, or
milk may be a source of indirect
transmission Arthropods such as fleas,
mosquitoes, lice, ticks, mites and flies
can indirectly transmit infectious agents.
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Classification of Diseases Acute diseases that
develop rapidly but last only a short time
(common cold) Chronic diseases that develop
slowly, usually with less severe clinical signs
and are continual or recurrent 9tuberculosis) Lat
ent diseases in which a pathogen remains
inactive for along periods fo time before
becoming active (herpes viral infections) Infecti
ous or communicable a disease that is acquired
from an infected host (flu) Contagious easily
transmitted communicable diseases (chickenpox
) Noncommunicable not spread from one host to
another and diseased individuals do not serve as
a source of contamination for others (tooth decay)
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Epidemiology The study of the effects of
diseases on the community. The frequency and
distribution of disease within a population is
studied. microbe virulence ports of
entry and exit course of disease Epidemiologi
sts are concerned with the who, what, where, when
, why and how of infectious diseases. They
monitor statistics to determine the frequency of
a particular disease in a given population.
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Endemic diseases that are always present within
a population of a particular geographic
area. Enzootic disease conditions affecting
animals of a specific geographic area
constantly present in a
specific animal community, but only occurs in a
small number of cases. (plague in prairie
dogs) Sporadic when there are a few isolated
cases of a disease, such as the plague in
humans, seen in widespread areas in an
unpredictable manner Epidemic a disease with a
sudden onset and widespread outbreak within a
group Epizootic widespread disease in
populations of animals spread rapidly,
simultaneously affecting a large number of
animals in a region Pandemic disease that is a
widespread epidemic and generally involves the
spread across continents. Panzootic
widespread epizootic disease.
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Agencies WHO (World Health Organization) a
specialized agency within the United
Nations. Missions 1. to
promote cooperation for health care among
nations 2. carry out disease control and
eradication programs 3. improve the quality
of human/animal life When epidemics occur, WHO
sends out teams of epidemiologists to investigate
the outbreak and to assist in bring the outbreak
under control.
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CDC (Centers for Disease Control and
Prevention a United States federal agency
under the control of the U.S. Department of
Health and Human Services. Function to
assist state and local health departments in all
aspects of epidemiology. to promote
disease prevention and health promotion goals
that will foster a safe and healthful
environment where health is protected,
nurtured, and promoted. One branch within
the CDC is the National Center for Infectious
Disease (NCID) and its mission is to prevent
illness, disability, and death caused by
infectious disease in the United States
and around the world.
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NIH National Institutes of Health a division
of the U.S. Department of Health and
Human Services the primary federal agency for
conducting and supporting medical
research. Publishes guidelines for
the care of animals in research facilities as
well as the prevention of disease
transmission among animals and between animals
and humans. NIH funds
research on a variety of disease topics including
zoonoses and ways to prevent their
spread. NIH also educates the public
and physicians about the role of zoonoses and
human health through providing information
such as the role of pets and the
immunocompromised person.
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At the federal level, the U.S. Department of
Agricultures (USDA) Animal and Plant Health
Inspection Service (APHIS) requires licensed
veterinary personnel to report diseases that pose
a significant threat to human health.
All information taken directly from
Understanding Zoonotic Diseases by Janet Amundson
Romich. Thomson Delmar publishing