Term Test 2 Flashcards
what is the name for the causative agent of lyme disease
borrelia burgdorferi
what is the name for heartworm
Dirofilaria immitis
what is the name of the non-pathogenic filarid nematode in dogs
Acanthoceilonema reconditum
heartworm (dirofilaria immitis) infects (2)
dogs and cats
what is the lifecycle of filarid nematodes
adult female -> lays microfilariae (pre-L1) -> ingested by a blood-sucking insect -> mature to a L3 in the insect -> infect definitive host when insect feeds -> migrate to predilection site
how do you differentiate drofilaria immitis from acanthocheilonema reconditum
dirofilaria immitis has tapering at the anterior end; acanthocheilonema reconditum is shorter and narrower
what are characteristics of adult acanthocheilonema reconditum
slender, > 5cm long
where do adult acanthocheilonema reconditum live
in connective tissue
what is the intermediate host of acanthocheilonema reconditum
fleas (lice)
what is the life cycle of acanthocheilonema reconditum
adult nematodes in the connective tissue release microfilariae -> flea feeds on dog and ingests microfilariae -> microfilariae develop to infective larvae in the flea -> flea feeds on dog, transmitting infective larvae
what are the two ways that dogs can become infected with acanthocheilonema reconditum
1) by an infected flea feeding on the dog and transmitting L3 larvae
2) by dog ingesting an infected flea
what are the definitive hosts for dirofilaria immitis
dogs, cats, ferrets, wild canids (foxes, coyotes), people
what are the intermediate hosts for dirofilaria immitis
mosquitoes
where is the predilection site for dirofilaria immitis
right caudal lobar artery
the antigen tests for dirofilaria immitis test what antigen
of adult females
how can we tell apart a male from a female adult dirofilaria immitis
males have squiggly tail
how big are adult female dirofilaria immitis
20-30 cm
are male dirofilaria immitis bigger or smaller than the females
smaller (also have tail spiral)
_____ + ______ = diagnostic for heartworm
size + site
site: right caudal lobar artery (vs. connective tissue)
size: larger and wider (vs. smaller and more narrow)
what is the heartworm life cycle
1) mosquito bites an infected dog and ingests microfilariae (pre-L1)
2) microfilariae mature to larvae in the mosquito (4-5 weeks)
3) mosquito bites a dog, transmitting heartworm larvae (L3)
4) larvae enter bloodstream, migrate to heart and lungs, grow and become sexually mature (7-9m)
5) adult heartworms can live in the heart and lungs for 5-7 years
what is the minimum age to test puppies for heartworm and why
7 months; this is the minimum age at which a dog could have adult, sexually active heartworm present in their body
summarize the following information about heartworm:
- larvae in pulmonary arterioles by ~
- pre-patent period ~
- adults live ~
- ~70d
- ~7-9m
- ~5-7y
what is the earliest start for heartworm transmission
June-July
how long does it take heartworm microfilaria to mature in mosquitos at the following temperatures:
18C:
26C:
30C:
18C: 29 days
26C: 12 days
30C: 8 days
what is the latest end for heartworm transmission
August-October
in Ontario, when does the ability to transmit L3 to dogs START and END
START: June 1
END: October 8
A survey done in 2010 found that the prevalence of heartworm infections in dogs is _____ and the prevalence of disease is _____
0.13%; 12%
____% of cases in Ontario are south of highways 401/402/403
80%
The prevalence of heartworm south of the 401/402/403 is highest in ________ at _____% and the prevalence north of the 401/402/403 is about ____%
Caledonia; 15.5%; 0.1%
how long do adult HW live in cats and how long are cats microfilaremic
adults: 1-2 years
microfilaremic: 1 month
the secretory products of adult heartworm have mechanical activity that can cause
proliferative pulmonary endarteritis
what happens if a large number of heartworm parasites start dying
pulmonary embolism
what is the pathogenesis of a large heartworm parasite burden
pulmonary hypertension -> right ventricular hypertrophy -> heart failure
heartworm is often (clinical/subclinical) in Ontario
often subclinical
the severity of clinical signs associated with heartworm depends on
- burden (# of adult parasites)
- size of dog
- exercise level
what are usual signs of heartworm
exercise intolerance, coughing, dyspnea
what are severe signs of heartworm
hydrothorax, ascites, loss of condition, hemoptysis
what are the blood examination test methods for heartworm?
- wet blood film
- stained blood smear
- concentration methods (Knotts, Difil)
what is the sensitivity and specificity of blood examination tests for heartworm
Sn: 75%
Sp: 90%
what is the sensitivity and specificity for heartworm antigen tests
Sn: 99%
Sp: 99.3%
what is the primary diagnostic and screening method for heartworm
antigen tests (ex. 4Dx, DiroCHEK)
are heartworm DNA tests useful? why or why not
No; no described Sn or Sp
how do we use radiographs to diagnose heartworm
- enlarged, tortuose pulmonary vessels
- right ventricular hypertrophy
what tests for heartworm are only useful if the animal has a large burden
radiographs and ultrasound (very specific in this case)
what sorts of history questions are important to determine heartworm risk and likelihood of a positive test
- location
- travel history
- prevention use
- compliance
what is sensitivity
proportion of infected animals that test positive
what is specificity
proportion of uninfected animals that test negative
Fill in the following for Ontario heartworm cases:
- never left the province
- imported from Southern USA
- imported from elsewhere in USA
- 51%
- 11%
- 13%
what percentage of HW+ dogs were not on prevention in the previous year
89%
what are the 6 reasons we screen dogs in Ontario
1) to rule out HW before giving a dog prevention
2) label recommendation
3) for safety reasons when using diethylcarbamazine (Decacide)
4) concern about reactions in microfilaremic dogs
5) to remove reservoir at the start of the transmission season
6) recommended by the American Heartworm Association
we want a PPV or NPV of at least ____ or ideally ____ to be confident that the animal truly is or is not infected
90%; 95%
overall, HW tests are useful if the dog is ________________ and not useful if the dog is ________________
at risk (travelled to an endemic area, not on prevention); not at risk (not in a high risk area, on prevention)
HW +ve screening tests are “certain” only for __________ dogs in _______________ areas
unprotected; high prevalence
how should you handle screening of healthy dogs in low risk areas
1) get a benchmark negative before you initially start on prevention
2) evaluate need annually for dogs on prevention (i.e did you travel to an endemic area or did you stop the prevention)
3) discuss risk and comfort level with owner
heartworm prevention targets
immature larvae
most prevention today are
macrocytic lactones
what was the first monthly heartworm prevention and what is the active ingredient? how is it taken?
Heartgard (ivermectin); orally
what was the second and third monthly prevention to be created and what is the active ingredient
interceptor and interceptor plus; milbemycin; orally
what was the 4th monthly heartworm prevention and what is the active ingredient
Revolution; selamectin; topical
what is the 5th monthly prevention? what is the active ingredient? how is it taken
Advantage multi; moxidectin; topical
what is the active ingredient in Nexgard Spectra
milbemycin
what is the active ingredient in Simparica Trio and how is it taken
moxidectin; oral
what is the active ingredient in Credelio +
milbemycin
what is the injectable heartworm prevention and how long does it last for in Canada
Proheart 6 (6 months)
what do we use to treat heartworm positive drugs? how many injections? what is the average cost?
immiticide; 3 injections; $2000-$3000
what preventative is safe for potentially positive dogs, why and for how long?
Advantage multi (moxidectin); has slow killing capacity; can give for up to 18 months
4Dx tests for what 4 diseases
1) heartworm (dirofilaria immitis)
2) erlichia canis
3) lyme antibody
4) anaplasma phagocytophilum
what tick carries lyme disease and how can we identify it
Ixodes scapularis (black-legged tick or deer tick); all dark brown plate on top
what transmits erlichia canis
rhipicephalus sanguineus
what regions of Ontario and the USA have a higher prevalence of lyme disease
- the western end of Lake Ontario and eastern Ontario
- Northeastern USA
what regions of Ontario and the USA have a higher prevalence of E. canis disease
- Southeastern USA
if a dog tests positive on 4Dx for lyme disease, what would increase the PPV
- recent travel to the western end of Lake Ontario or eastern Ontario
- recent travel to the Northeastern USA
- clinical signs consistent with lyme disease
If a dog tests positive for E. canis on 4Dx, what would increase the PPV
- recent travel to Southeastern USA or a tropical location
- clinical signs consistent with E. canis
What are clinical signs of lyme disease
fever, anorexia, lymphadenomegaly, polyarthritis, shifting leg lameness, swollen joints
what are clinical signs of E. canis
fever, anorexia, lymphadenomegaly, polyarthritis, weight loss, CNS signs, dermal petechiae/ecchymoses
