Transcript Dirofilaria immitis

DIROFILARIA IMMITIS
By Ryan Hamm and Carolynn Peter
TAXONOMY
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Kingdom: Animalia
• Phylum: Nematoda
• Class: Secernentea
• Order: Spirurida
• Family: Onchocercidae
• Genus: Dirofilaria
• Species: immitis
GEOGRAPHIC RANGE
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At one time it was confined to the Southern US,
it is now found where ever the mosquito vector
is found
Worldwide
In US highest infection rates
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Along the Gulf and Atlantic coast
Along the Mississippi River
US DISTRIBUTION
HOSTS
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Definitive Hosts:
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Canines
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Dogs, Foxes, Wolves, Coyotes,
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Accidental Hosts:
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Occasionally cats, rodents, horses, and birds
Humans
Intermediate Host:
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Mosquitoes
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Culex pipiens (often infects cats), Anopheles maculipennis,
Coquillettidia richiardii, Aedes triseriatus, Ochlerotatus
notoscriptus (prevalent in Australia), Aedes albopictus, Aedes
aegypti, Culex quinquefasciatus, Aedes taeniorhynchus, Aedes
scapularis, Aedes trivittatus
MORPHOLOGY
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Males
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Females
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12-26 cm long
Have a coiled, spiral tail
25 to 30 cm long
Vulva opening just behind the
posterior end of the
esophagus
Are ovoviviparous
Microfilariae
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218-329 um long
Have a pointed tail
LIFE CYCLE
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Mosquito becomes infected during a blood meal taken from a host containing
microfilariae
Microfilarae develop into L3 in the Malpighian tubules and then migrates
through the body cavity to the head and mouthparts where they become
infective.
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In the mosquito’s next blood meal L3 larvae are deposited into the host.
The molt from L3 to L4 occurs between days 3-12 post infection
L4 molt to final stage occurs at day 50-70 post infection
Worms enter the pulmonary vasculature as early as day 70 and have all
arrived by day 90-120.
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The amount of time that this takes depends on temperature
As they increase in size they occupy larger and larger arteries until they are fully
mature
In the right side of the heart, pulmonary arteries, and lungs they mate and
produce microfilariae (6-7 months post infection)
The final location of the adult worms depends on the size of the dog and the
number of worms present
In humans the worms migrate only to the lungs and forms a lesion.
PATHOGENESIS
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On the outside
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Loss of appetite
Weight loss
Lethargic
Bulging in the chest
Wheezing and
coughing
Vomiting
Diarrhea
Bloody stool
Jaundice
Collapse
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On the inside
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Large worms
extend through the
openings of the
tricuspid and
semilunar valves
Pulmonary arteries
show thickening
and inflammation
of their inner walls
Death occurs from
cardiopulmonary
failure
PATHOGENESIS IN OTHER HOSTS
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Cats
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only a few worms can be
fatal
no treatment
In humans symptoms are
unpredictable and vague
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Chest pain
Cough
Coughing up blood
Fever
Malaise
WOLBACHIA
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Gram negative bacteria
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Needed for reproduction
and embryogenesis
Pathogenesis of disease
Antibiotic treatment
results in sterility of adult
worms
DIAGNOSIS
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Blood test to detect the
female worm antigen
Blood smear to look for
microfilariae
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ELISA for confirmation
Neither test is consistently
positive until 7 months
after
Worms in the heart
X-ray or ultrasound of
heart and lungs
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Usually done after animal
is known to be infected
Heartworm removal
TREATMENT
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Larval worms (L3 and L4)
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Ivermectin, milbemycin,
selamectin
Must be given every month to
prevent the maturation to adult
worms
Kills microfilariae if present in
infected dog
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Suppresses female reproduction
Adults
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Melarsomine dihydrochloride
Given IM in the lower back
Can be given in 2 or 3 dose sets
Must be done slowly because
killing of too many adult worms
can cause circulatory shock
Dog can not go for walks or
exercise for a month after
treatment
CONTROL
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Use monthly
chemoprophylaxis
during mosquito season
Get your dog a yearly
heartworm test to
ensure that no doses
were missed and adult
worms have not
progressed
4Dx Test
PUBLIC HEALTH CONCERNS
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Can result in death for
highly infected dogs
High cost of treatment
and preventions for
pet owners
Has the ability,
although rare, to
infection humans
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Not life threatening,
but often confused
with lung cancer
QUESTIONS?
QUIZ
What life stages are present in the mosquito?
L1, L2, L3
What life stage is infective to the definitive host?
L3
Where are infections most prevalent in US?
Along the Gulf and Atlantic Coast and the Mississippi
What bacteria is needed for heartworm to reproduce?
Wolbachia
Ivermectin and milbemycin target what life stages?
Larval worms (L3 and L4), microfilariae if present
In what part of the body do the adult worms live?
Right side of the heart and right pulmonary arteries
SOURCES
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http://plpnemweb.ucdavis.edu/nemaplex/Taxadat
a/Dimmitis.htm
http://plpnemweb.ucdavis.edu/nemaplex/Taxadat
a/Dimmitis.htm
http://www.marvistavet.com/html/body_heartwor
m_treatment.html
http://www.wolbachia.sols.uq.edu.au/about.cfm
http://www.heartwormsociety.org/
Foundations of Parasitology by Gerald Schmidt
and Larry S. Roberts