Transcript Zoonotic Pathogens

Zoonotic Pathogens:
An Introduction
Dr. Emilo DeBess
Oregon Health Division
Dr. McKinley Thomas
Augusta State University
Zoonotic Diseases
• ...cause infections in animals and can be
transmitted to humans
• …are typically endemic and occur in a
natural foci
– However, ecologic changes and
meteriologic or climate events can
promote epidemic expansion of the host
and geographic range.
History
• Interactions between animals and
humans have occurred since the
beginning of time.
• As animals became domesticated and a
close bonds developed between
animals and humans, the occurrence of
zoonotic diseases increased.
Significant Zoonitic Pandemics
• 1700s, Mongols invaded Europe
• Mongols carried plague with them
• This lead to “black death” or plague
pandemic
• Killed 1/3 of European population
Significant Zoonitic Pandemics
• Early 1900’s
• “Spanish flu” transmitted from pigs to
humans
• Decimated 20 million people worldwide
• Continues to pose a threat to humans
Contemporary Threats
• Potential Human Pathogens
– E. coli 0157H7
– Caliciviruses (evolved from the sea)
– Bovine Spongiform Encephalopathy
(BSE) also known as “mad cow
disease”
Etiology
• Today’s threat involving zoonotic
diseases is considered to be partly
due to human involvement in
which the artificial multiplication
of these pathogens can be used as
biological terrorism.
Prevalence
• Largely Unknown
• Both serological studies and anecdotal
discussion have been used to generate
estimates
– 1997 a study trying to asses the prevalence
of antibodies against Bartonella henselae
and B. quintana was done at a veterinary
conference. The results indicated that 7.1%
of the veterinary population had antibodies
which was no different from the general
population studies at an earlier time.
Believed More Common
• Ringworm caused by Trychophitum
species. believed to be heavily under
diagnosed / not reported
• More prevalent among children
Common Zoonotic Diseases
• Bacterial
– Plague
– Cat Scratch Fever
– Salmonellosis
• Parasitic
– Toxoplasmosis
– Ring Worm
• Viral
– Hantavirus
– Prion
• BSE
Plague in Domestic Animals
• Exudates from buboes or
respiratory secretions and
sputum are highly
contagious to humans
• Most cases of human
pneumonic plague in the last
two decades were acquired
from infected cats
• Owners should control fleas
on their pets and keep pets
away from wildlife
Plague in History
• Pandemics in history
involving Europe, Asia,
Africa
• “The Black Death,”
thought to be caused by
displeasure of the gods or
other supernatural
powers, heavenly
disturbances
• The etiologic agent,
Yersinia pestis, first
isolated in 1894 (Yersin
and Kitasato)
Cat Scratch Disease
• One estimate by the Centers for Disease Control
found that there were 2.5 cases of CSD per
100,000 people per year in the United States.
• In recent years, many studies have implicated
the gram negative bacterium Bartonella
henselae as the primary (but not the sole) cause
of CSD
• Typically, a small skin lesion (resembling an
insect bite) develops at the site of a cat scratch or
(less commonly) a bite, followed within two weeks
by swollen lymph nodes and sometimes a fever.
Cat Scratch Disease
• Cats are the main reservoir for B. henselae.
Surveys for B. henselae antibodies in cats in the
United States have found average infection rates
to be from 25% to 41% in clinically healthy cats.
• The lowest rates were in the Midwest and great
plains regions (4-7%) and the highest were in the
southeast (60%). Warmer, more humid climates
are most supportive of fleas, which have been
shown to transmit B. henselae from cat to cat.
• It appears that the majority of cats do not
become ill when they are infected with this
bacterium and kittens are more commonly
infected than adults.
Cat Scratch Disease
• CSD is primarily a concern in homes
with immunosuppressed people.
• Since kittens are more likely to carry B.
henselae than adult cats, it is
recommended that people with
compromised immune systems adopt cats
older than 1 year of age to reduce the risk
of contracting CSD.
Cat Scratch Disease
• Since carrier cats are always healthy and multiple
• cases of CSD within a household are rare,
euthanasia of a suspected carrier is not warranted.
• Onychectomy (declawing) is also not
recommended, since infection can occur without a
cat scratch.
• As is always the case, any cut or scratch should be
promptly washed with soap and water.
Reptile-Associated
Salmonellosis
Reptile-associated Human Salmonella
History
1944
1946
1963
1972
First Salmonella sp. isolate from snakes.
First Salmonella sp. isolate from turtles and lizards.
Turtle-associated salmonellosis first described.
FDA regulation requiring certification of turtles for sale as
"Salmonella-free."
1974 Study shows 300,000 turtle-associated human
salmonellosis cases per year in U.S.
1975 FDA bans sale of viable turtle eggs or live turtles with
carapace length < 10.2 cm.
1977 CA State regulations ban sale, as above.
Reptile-Associated
Salmonellosis
• In the United States, pet turtles were an
important source of salmonellosis until
commercial distribution of pet turtles less
than 4 inches long was banned in 1975.
• This ban led to a 77% reduction in the
frequency of turtle-associated Salmonella
serotypes isolated from humans during
1970-1976.
Reptile-Associated
Salmonellosis
• Approximately 93,000 (7%) cases per
year of Salmonella infections are
attributable to pet reptile or amphibian
contact.
• An estimated 3% of households in the
United States have a reptile (CDC,
unpublished data, 1999)
Reptile-Associated
Salmonellosis
• Kansas. During April 1997, a 6-year-old boy
had bloody diarrhea of 10 days' duration,
abdominal cramps,vomiting, and fever (104.9 F
[41 C]). Stool culture yielded Salmonella
serotype Typhimurium. The child was treated
with ceftriaxone and amoxicillin / clavulanate.
• Nine days after the boy started therapy, his 3year-old brother also developed diarrhea, and a
stool sample yielded S. Typhimurium..
Reptile-Associated
Salmonellosis
• No other family members became ill. The
two boys shared a room with two corn
snakes that they handled regularly. Stool
cultures from the corn snakes yielded S.
Typhimurium.
• The parents reported to health
department staff that they were unaware
that snakes are a source of salmonellosis
Salmonella Infection in Reptiles
• Numerous serotypes reported (5 or more may be isolated
from a single reptile specimen).
• Latent infections with reactivation resulting in intermittent
shedding
• Usually asymptomatic (wound infections, septic arthritis,
endocarditis reported after inoculation via bites/scratches).
DIFFICULT TO IDENTIFY OR ELIMINATE CARRIERS.
Chiodini RJ, Am J Epidemiol 1981.
MMWR November 12, 1999
Recommendations to Prevent Human
Reptile-associated Salmonellosis
• Do not keep reptiles as pets where high risk individuals may
be exposed such as infants, the elderly, and people with
compromised immune systems.
• Thoroughly wash hands after any contact with reptiles,
including handling of the animal or its cage.
• Confine reptiles to prevent environmental contamination. For
example, keep reptiles off of floors and rugs where infants crawl
and out of tubs and sinks where infants are bathed.
Toxoplasmosis
• Toxoplasmosis is a disease caused by microscopic
parasite called Toxoplasma gondii.
• It is not a new disease, having first been
discovered in 1908. Since its discovery,
toxoplasmosis has been found in virtually all
warm-blooded animals including most pets,
livestock, and human beings.
• Nearly one-third of all adults in the U.S. and in
Europe have antibodies to Toxoplasma, which
means they have been exposed to this parasite.
Toxoplasmosis
• There are 3 principal ways Toxoplasmosis is
transmitted:
• 1.Directly from pregnant mother to unborn child
when the mother becomes infected with
Toxoplasmosis during pregnancy.
• 2.Consumption and handling of undercooked or
raw meat from infected animals.
• 3.Ingestion of food or water or inhalation of dust
contaminated with a very resistant form of
Toxoplasmosis called the oocyst.
Toxoplasmosis
• Toxoplasma in meat can be killed by
cooking at 152ºF (66ºC) or higher or
freezing for a day in a household freezer.
• Of all the infected animals tested, only
cats are the perfect hosts for the
production of the infectious and resistant
Toxoplasma oocysts.
Toxoplasmosis
• There are two populations at high risk for
infection with Toxoplasma; pregnant women and
immunosuppressed individuals. In the United
States it is estimated that approximately 3,000
children are born infected with toxoplasmosis
every year.
• Although the majority of infected infants show no
symptoms of toxoplasmosis at birth, many are
likely to develop signs of infection later in life.
Loss of vision, mental retardation, loss of
hearing, and death in severe cases, are the
symptoms of toxoplasmosis in congenitally
Toxoplasmosis
Hantavirus Pulmonary Syndrome Cases
by State of Residence
22
14
5
14
12
7
1
2
6
2
24
33
31
41
3
5
1
14
2
1
1 2
14
1 1
1
1
13
1
1
1
1 - 5 cases
6 - 10 cases
11 -15 cases
>15 cases
277 cases in 31 states
10/4/2000
Transmission of Hantaviruses
Chronically infected
rodent
Horizontal transmission of
infection by intraspecific
aggressive behavior
Virus also present in
Virus is present in
throat swab and feces
aerosolized excreta,
particularly urine
Secondary aerosols, mucous
membrane contact, and skin
breaches are also a consideration
Clinical Manifestations of
Hantavirus
Hantavirus
• Non-specific flu-like prodrome
– fever, headache, myalgia, malaise,
GI, respiratory signs
• Thoracic radiographs: interstitial infiltrates
• Rapid progression to respiratory failure
– "leaky capillaries" -> noncardiogenic pulmonary
edema
BSE
•Since 1996, evidence has been increasing for a causal
relationship between ongoing outbreaks in Europe of a disease
in cattle, called Bovine Spongiform Encephalopathy (BSE, or
"mad cow disease"), and a disease in humans, called new variant
Creutzfeldt-Jakob disease (nvCJD).
•Both disorders are invariably fatal brain diseases with
unusually long incubation periods measured in years, and are
caused by an unconventional transmissible agent.
Ringworm
• Ringworm is a fungus infection of the scalp
or skin. Symptoms include a rash that is often
itchy and flaky
• Ringworm is spread by direct contact with a
person or animal infected with the fungus.
• The same fungi that infect humans can also
infect animals such as dogs, and cats, and
infections may be acquired from pets as well
as from infected children.
Bibliography
• Swedish Institute of Infectious Disease
Control. (2001). Available:
http://www.smittskyddsinstitutet.se/
• Control of Communicable Diseases Manual
James Chin, MD 17th edition
Centers for Disease Control and Prevention
www.cdc.gov
We would like to acknowledge Michelle Jay, DVM,
MPVM for providing materials for this presentation.