Download Dirofilaria immitis

Dirofilaria immitis
Kristi Bjerke
&
Heather Lee
Taxonomy
CLASS: SECERNENTEA
• SUBCLASS: SPIRURIA
– ORDER: SPIRURIDA
• SUPERFAMILY: FILARIOIDEA
– FAMILY: ONCHOCERCIDAE
» Scientific name - Dirofilaria immitis
» Common name - Dog heartworm
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Hosts
• Definitive Host: dogs, foxes, wolves,
coyotes, cats, ferrets, sea lions
• Intermediate Host: Over 70 species of
mosquitoes
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Geographic Distribution
• Worldwide
– Most common in mild and warm climates
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Morphology
• Adults are long,
white, thread-like
worms
– Females 25 to
30cm long
– Males 12 to 16
cm long with
spirally coiled tail
Morphology
• give live birth and the baby worms
are called Microfilariae
• Microfilariae
– Sheathless
– 218 to 329µm long
– have a long pointed tail
Life Cycle
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Life Cycle
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• A dog infected by microfilariae is bitten by a
mosquito
• If the microfilariae is not picked up by a
mosquito after 2 years, they die of “old age.”
•Microfilariae can be
transmitted across the placenta.
•Puppies will not develop adult
heartworms because the
microfilariae didn’t go through
the intermediate
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Life Cycle
• Inside the mosquito, the microfilariae
develop to L2’s and finally to L3’s.
• The L3 is the infective stage for dogs.
– Takes a few weeks
– Temperature dependant
• Minimum of 57 ºF is required
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Life Cycle
• The L3 is deposited in mosquito saliva next to
the bite and then migrate into the body.
• The average mosquito can only transmit a
maximum of 10 infective larvae at one time
• The L3 larvae then live in the dogs skin where
they develop into an L4 stage.
• They then live in the subcutaneous tissues and
muscle for 3 months before they finally molt into
an adult.
Life Cycle
• Adults migrate to the right side of the
heart and into the pulmonary arteries and
lungs where they mate and produce
microfilariae.
–The overall maturation and
migration process until
mating takes approximately
5-7 months
–Adult worms can live in the
dog for up to 5 years
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Pathogenesis of the Heart
• Heavy infections(over 25 worms for
a 40 lb dog)
– worms begin to back up into the
right ventricle
• less blood pumped.
• Over 50 worms the ventricle is full
and the atrium begins to contain
worms.
• Over 100 worms the entire right side
of the heart is filled
– phenomenon is called "Caval
Syndrome" and most dogs do
not survive it.
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Canine Symptoms
•
•
•
•
•
Cough, exercise intolerance
dyspnea (difficulty breathing)
abnormal lung sounds
hepatomegaly (enlargement of the liver)
syncope (temporary loss of
consciousness due to poor blood flow to
the brain)
• ascites (fluid accumulation in the
abdominal cavity)
• abnormal heart sounds
• death
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Feline Symptoms
• Non-specific generic signs of illness
– Vomiting intermittently
– Lethargy
– Lack of appetite
– Weight loss
– Coughing
– Asthma-like signs
– Gagging
– Difficult or rapid breathing
• The early signs (when worms are carried to the pulmonary arteries) are
often misdiagnosed as asthma or allergic bronchitis
– Actually Heartworm Associated Respiratory Disease (HARD)
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Heartworm in Cats vs. Dogs
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Diagnosis
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• Blood Tests
– Filter test to look for microfilariae
• Doesn’t work well for small infections
– Antigen test screens for pieces of adult heartworm
skin in the blood
• Only works for female worms
• Need at least 3 for it to be detected
– Newer tests test for antibodies
• X-rays
– Enlargement of lobes of lungs or right side of heart
Treatment
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• Adulticide
– Melarsomine dihydrochloride (Immiticide®)
• Intramuscular injection into lumbar muscles
• Complications include thrombosis (clogging) of pulmonary
arteries due to dead worms
– No current treatment for cats
• Microfilaricide
– macrocyclic lactone (ML) anthelminthics, i.e.,milbemycin oxime,
selamectin, moxidectin and ivermectin
– Commonly used in heartworm preventative
Control/Prevention
• Can be given as
– Monthly Tablets
– Chewables
– Topicals
• Ivermectin
– Heartgard, Heartgard Plus, Tri-Heart, Iverheart Plus
• Milbemycin oxime
– Interceptor, Sentinel
• Selamectin
– Revolution
• Moxidectin
– Advantage Multi
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http://www.heartwormsociety.org/quiz.asp