Term Test 2 Flashcards by Giselle Carter

what is the name for the causative agent of lyme disease

borrelia burgdorferi

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what is the name for heartworm

Dirofilaria immitis

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what is the name of the non-pathogenic filarid nematode in dogs

Acanthoceilonema reconditum

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heartworm (dirofilaria immitis) infects (2)

dogs and cats

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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

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how do you differentiate drofilaria immitis from acanthocheilonema reconditum

dirofilaria immitis has tapering at the anterior end; acanthocheilonema reconditum is shorter and narrower

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what are characteristics of adult acanthocheilonema reconditum

slender, > 5cm long

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where do adult acanthocheilonema reconditum live

in connective tissue

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what is the intermediate host of acanthocheilonema reconditum

fleas (lice)

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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

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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

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what are the definitive hosts for dirofilaria immitis

dogs, cats, ferrets, wild canids (foxes, coyotes), people

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what are the intermediate hosts for dirofilaria immitis

mosquitoes

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where is the predilection site for dirofilaria immitis

right caudal lobar artery

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the antigen tests for dirofilaria immitis test what antigen

of adult females

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how can we tell apart a male from a female adult dirofilaria immitis

males have squiggly tail

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how big are adult female dirofilaria immitis

20-30 cm

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are male dirofilaria immitis bigger or smaller than the females

smaller (also have tail spiral)

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_____ + ______ = diagnostic for heartworm

size + site

site: right caudal lobar artery (vs. connective tissue)
size: larger and wider (vs. smaller and more narrow)

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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

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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

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summarize the following information about heartworm:
- larvae in pulmonary arterioles by ~
- pre-patent period ~
- adults live ~

~70d
~7-9m
~5-7y

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what is the earliest start for heartworm transmission

June-July

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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

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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

Term Test 2 Flashcards

(75 cards)