Lecture 3: Nematodes (heartworms) Flashcards Preview

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Flashcards in Lecture 3: Nematodes (heartworms) Deck (54):
1

canine heartworm

dirofilaria immitis

2

adult dirofilaria immitis are found where

right ventricle, pulmonary arteries

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filaria do not produce eggs but

free living larval stages called microfilaria

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vector/IH of dirofilaria immitis

mosquitoes

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must differentiate heartworm MFF from

acanthocheilonema reconditum (filaria trans by fleas but not considered a pathogen)

6

number of MFF in blood of acanthocheilonema vs dirofilaria

few - acantho
many - dirofilaria

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motion of dirofilaria vs acanthocheilonema MFF

Dirofilaria are stationary, wiggle and stay in view

acanthocheilonema is progressive and will move out of view

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shape of dirofilaria vs acanthocheilonema

acantho is curved, thinner, shorter, has curved thin tail

dirofilaria is straight with a tapered head, longer

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occult infections

dog harbors male and/or female adults

single sex
low numbers

"hidden" infection = MFF NOT detectable in blood

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best way to dx occult HW infection

Ag test

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when are dirofilaria MFF most active in circulation

nocturnal and incomplete periodicity (never disappear from peripheral blood)

12

how many mosquito spp are common vectors for HW

14

13

__ are released by the female worm, mosquito feeds on dog and picks this stage up

MFF

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MFF develop to infective __ in the mosquito in about 8 days (temp dependent)

L3 larvae

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L3 larvae are deposited at the skin surface when mosquito takes blood meal; L3 enter DH via

mosquito's bite wound

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larvae migrate and molt and eventually mature in the

heart or lungs

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prepatent period for dirofilaria immitis

6-7mo

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what stage do the preventatives we give monthly affect

L3 the first 3d in circulation while molting to L4

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worms are not detectable consistently using most test procedures until they are __ old

6-6.5mo

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Ag positive test but do not see MFF

gravid female is detected by Ag test before birthing MFF

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how many spp of mosquitos are known to transmit HW

24

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Disease in dogs is mainly due to the

adult worms in the PA

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rough internal surface of PA is termed

villous endarteritis

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changes in circulation caused by HW

Vascular resistance (right ventricle hypertrophy)
decreased CO (exercise intoleracne, liver and kidney dz)

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overrun with worms, infect atrium and vena cava

vena cava syndrome

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diagnose HW

Detection of Ag and detection of circulating microfilariae

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when are most dogs Ag positive that are not on routine preventatives

~7mo PI, can be as early as 5mo

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when would dogs who missed a dose of preventative become Ag positive

~9mo PI

pets on macrocyclic lactones may never develop MFF or they are transient in small numbers

29

what sample do you need for SNAP, witness, Heska POC Ag test

serum, plasma, or whole blood

30

what is the gold standard HW Ag test

diroCHEK HW Ag test (serum or plasma)

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if get a positive on a POC test what should you do next

check for MFF and check a different POC test

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what test measures MFF present

modified knotts

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who should be tested for HW Ag and when

every dog annually
pets not on preventative dogs over 7mo , retest 7-12 mo after starting prevents
dog misses dose, retest 7-12 mo after restart

AHS guidelines suggest testing at 6 and 12 mo

34

if switch HW preventatives when should you retest for Ag

4.5 and 9 mo after switch

35

should you trust HW Ag test results

yes, high sensitivity and specificity

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What can cause a positive Ag test but negative MFF test

- young infection, no circ MFF yet
- using preventatives w/o removing adults
- female only infection
- immune mediated occult
- failure to use MFF concentration test

37

what can cause a negative Ag test but positive MFF test

- different spp of MFF
- MFF aquired transplacentally
- adults removed or died but still have circulating MFF
- contaminated test

38

if antigen test is variable and MFF is negative or positive

fluctuating Ag levels (# worms, age worms, quality sample)

39

what is the susceptibility gap

the early stages are suseptible to macrocyclic lactones
the later stages are susceptible to melarsomine
inbetween no treatment will touch "teenage stage" = susceptibility gap

40

symbiotic gram negative bacteria related to Ehrlichia that is present in ALL life stages of dirofilaria immitis

Wolbachia pipientis

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what do we know about Wolbachia and Dirofilaria

it contributes to pulmonary and renal inflammation, is important for biology and reproductive functions, necessary for worm survival

42

killing adult worms

melarsomine dihydrochloride (immiticide)

NO activity against worms <4mo
AHS recommends 3 dose protocol

43

what can help control clinical signs of PTE during HW tx

Steriods

44

What can help treat wolbachia and weaken HW before immiticide tx

doxycycline

45

What is a potent preventative that treats MFF but a modified knotts should always be done first to quantify MFF present

moxidectin (advantage multi)

46

cats infected with HW get what condition

heartworm associated respiratory dz (HARD); vascular and airway dz from death of IMMATURE HW in cats

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stage 1 of HARD in cats

immature adults in PA, immune rxn suppressed and cats tolerate the worms

48

Stage 2 of HARD in cats

worms dying = inflammation and PTE

worms rarely mature in cats

49

cats IS is killing the worms causing inflammation and death usually occurs from __ not the worms

PTE

50

dz in canines vs felines depends on

dogs: number of worms and size of dog
cat: few worms cause dz

51

worms are __ lived in dogs/cats

long (dogs)
short (cats)

52

MFF in cats

usually amicrofilaremic

53

what organs are affected in dogs v cats

dogs: hear and lungs
cats: lungs

54

treatment of HW in dogs vs cats

dogs: treatment available
cats: only symptomatic tx, cannot use melarsomine in cats