Transcript The Epidemiology of Tick-transmitted Zoonotic Disease

Tularemia
• This is an infectious disease caused by the
organism Francisella tularensis.
• The disease this organism causes has a
large range of hosts, methods of
transmission, portals of entry, and
clinical syndromes.
• There are two main types- A and B.
– Type A appears to be more virulent in
animals and man. 90% of reported cases in
North America are type A.
– Type B is less severe and may therefore be
less likely to be reported.
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Tularemia
• Tick-borne tularemia is more common in
the spring and early summer among
persons who have visited tick-infested
areas.
• A small wound develops at the site of
attachment.
• Later, the regional lymph nodes enlarges
and becomes tender.
• Fever and chills are common.
• Serious complications leading to death are
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rare.
Tularemia
Route
Syndrome
1. Integumental invasions by Ulceroglandular,
arthropod, arthropod
adenopathy proximal to the
bite (ticks), knife, ect.
point of entry.
2. Exposure to eye.
3. Ingestion
4. Disseminated
Oculoglandular, cephalic,
and cervical nodes involved.
Typhoidal forms- oral and
GI symptoms, stomatitis and
pharyngitis.
All forms may disseminate
to the spleen, liver, lungs and
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pleura.
Tularemia
• Transmission for this disease is very
diverse
1. Mechanical vectors. Usually this is through
either ticks (many species) or deer flies.
Mechanical vector means
no reactivation period.
Sheep and dogs can bring ticks to man.
• Tick borne transmission is the most important
form in the US.
• Tick-borne tularemia is usually type A and has
an ulceroglandular presentation.
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Tularemia
• 2. “Rabbit fever”
– As hunting rabbits has become less
common, transmission by direct
contact with infected game has
decreased.
– It is advised that hunters avoid rabbits
which are sluggish or apathetic.
– I personally never understood this
recommendation. I think it means that
you should not eat rabbits that are
slow enough for you to shoot.
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Tularemia
2. “Rabbit fever”
• Only in the advanced stages of the disease
do the rabbits become lethargic, as such
advice to avoid animals with “spots on the
liver” may give hunters a false sense of
security.
• Human infection is usually through direct
exposure through wounds or conjunctiva
while cleaning and dressing wild game.
• The ulceroglandular clinical syndrome
is the most common clinical presentation.
• Game reservation – cancelled hunt
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Tularemia
• Transmission cont…
3. Inhalation: This is a problem in
Scandinavia. Where voles carrying the
bacterium invade hay and create infective
dust, which infects the people who breath.
This also occurs as laboratory accidents.
4. Water-borne: This is usually type B, it is
common in the Russia and associated
with small rodents.
• Host range:
– Incredibly wide - some mammals, birds,
and aquatic animals.
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Tularemia ulcer at site of exposure
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Tularemia – Think “Arkansas”
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Tularemia
• Prevention and Control:
– Report animal die-offs.
– Ectoparasite control of domestic animals.
– Avoid ticks. Check yourself for ticks after working
with tick-infested domestic animals and after trips
to tick-infested areas.
– Education of hunters. Use gloves for cleaning game.
Cook wild game well before eating.
– A vaccine is available in the US for persons at high
risk. This vaccine is extensively used in some parts
of the world (Russia).
– Avoid drinking water directly from “clean”
mountain streams.
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Q Fever
• Agent:
– Coxiella burneti
– It has a very good viability in the free state.
– It is very resistant to desiccation and
disintegration.
– Extremely infectious!! A single organism
can cause disease.
– Airborne transmission over long distances is
possible.
– High potential for use as a biological
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weapon.
• Distribution:
Q Fever
– Worldwide in animals and man, the reservoirs are
cattle, goats and sheep.
• Incidence:
– About half of goats and sheep in Michigan show
evidence of previous exposure. Cattle and wild
animals are also susceptible.
• Transmission:
– Airborne - this the most common.
– Direct contact - with infected animals. Also infected
milk, rarely.
– Tick transmission
– Fomites - contaminated clothing, wool or hair. 17
Q Fever
• Pathology and clinical signs in
animals
– Classically, Q fever in animals has
been reported to be only subclinical.
However, recent reports of abortions
in goats and sheep have been
substantiated.
– 1978 - Colorado outbreak of abortions
in goats
– 1980 - Ontario outbreaks of abortions
in goats and sheep herds.
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• Outbreaks:
Q Fever
– Ontario, 1981- Ontario has the first human
case ever reported. This coincides with the
first reports of outbreaks of goat and sheep
abortions. Q fever is now the leading cause
of granulomatous hepatitis in the province.
– Great Britain, between 1975 and 1981there were 839 human cases and
endocarditis was reported from 11%.
– Michigan, 1984 - The first two human cases
were reported in southwestern Michigan.
None have been reported since.
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Q Fever
• A case control study among goat owners
in two adjacent counties was preformed.
– 42% of family members were seropostive.
– 13% of community controls were
seropostive.
– 40% (49/123) of goats were positive.
– 44% (10/23) of sheep were positive.
• Seropositivity (in people) was statistically
associated with number of goat births on
the farm, assisting at goat births and the
total number of goats on the farm.
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Q Fever
• In laboratories around the world, there are
lots of work-place outbreaks.
– Most of these were through airborne exposure
and have occurred in both hospital and
research laboratories.
– Lambing taking place in the basement of
research facilities causes the bacteria to
become airborne and spread throughout the
building.
– Germany, 1996 - After a large outdoor
lambing, many people in a nearby town were
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infected with the bacterium.
Q Fever
• Diagnosis- This is done through history, serology
(CF test), and through isolation of the organism.
• Treatment - it responds well to chloramphenicol and
tetracycline.
• Prevention:
– Avoid birthing fluid of ruminants!!
• Wear gloves and mask when assisting birthing.
• Dispose of placentas and aborted fetus.
– Environmental contamination is mainly due to
infected placenta and postpartum discharges.
– Transmission is mainly through inhalation of
Coxiella-laden dust .
– Vaccination is possible, but it is not practiced in
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this country.
Significance for Bioterrorism
• Coxiella burnetii is a highly infectious
agent that is rather resistant to heat and
drying.
– It can become airborne and inhaled by
humans.
– A single C. burnetii organism may cause
disease in a susceptible person.
• This agent could be developed for use in
biological warfare and is considered a
potential terrorist threat.
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