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Parasitology 2018 > Lecture 3: Nematodes (heartworms) > Flashcards

Lecture 3: Nematodes (heartworms) Flashcards

1
Q

canine heartworm

A

dirofilaria immitis

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2
Q

adult dirofilaria immitis are found where

A

right ventricle, pulmonary arteries

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3
Q

filaria do not produce eggs but

A

free living larval stages called microfilaria

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4
Q

vector/IH of dirofilaria immitis

A

mosquitoes

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5
Q

must differentiate heartworm MFF from

A

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

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6
Q

number of MFF in blood of acanthocheilonema vs dirofilaria

A

few - acantho

many - dirofilaria

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7
Q

motion of dirofilaria vs acanthocheilonema MFF

A

Dirofilaria are stationary, wiggle and stay in view

acanthocheilonema is progressive and will move out of view

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8
Q

shape of dirofilaria vs acanthocheilonema

A

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

dirofilaria is straight with a tapered head, longer

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9
Q

occult infections

A

dog harbors male and/or female adults

single sex
low numbers

“hidden” infection = MFF NOT detectable in blood

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10
Q

best way to dx occult HW infection

A

Ag test

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11
Q

when are dirofilaria MFF most active in circulation

A

nocturnal and incomplete periodicity (never disappear from peripheral blood)

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12
Q

how many mosquito spp are common vectors for HW

A

14

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13
Q

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

A

MFF

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14
Q

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

A

L3 larvae

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15
Q

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

A

mosquito’s bite wound

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16
Q

larvae migrate and molt and eventually mature in the

A

heart or lungs

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17
Q

prepatent period for dirofilaria immitis

A

6-7mo

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18
Q

what stage do the preventatives we give monthly affect

A

L3 the first 3d in circulation while molting to L4

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19
Q

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

A

6-6.5mo

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20
Q

Ag positive test but do not see MFF

A

gravid female is detected by Ag test before birthing MFF

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21
Q

how many spp of mosquitos are known to transmit HW

A

24

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22
Q

Disease in dogs is mainly due to the

A

adult worms in the PA

23
Q

rough internal surface of PA is termed

A

villous endarteritis

24
Q

changes in circulation caused by HW

A 
Vascular resistance (right ventricle hypertrophy) 
decreased CO (exercise intoleracne, liver and kidney dz)
25
Q

overrun with worms, infect atrium and vena cava

A

vena cava syndrome

26
Q

diagnose HW

A

Detection of Ag and detection of circulating microfilariae

27
Q

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

A

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

28
Q

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

A

~9mo PI

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

29
Q

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

A

serum, plasma, or whole blood

30
Q

what is the gold standard HW Ag test

A

diroCHEK HW Ag test (serum or plasma)

31
Q

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

A

check for MFF and check a different POC test

32
Q

what test measures MFF present

A

modified knotts

33
Q

who should be tested for HW Ag and when

A

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
Q

if switch HW preventatives when should you retest for Ag

A

4.5 and 9 mo after switch

35
Q

should you trust HW Ag test results

A

yes, high sensitivity and specificity

36
Q

What can cause a positive Ag test but negative MFF test

A
  • 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
Q

what can cause a negative Ag test but positive MFF test

A
  • different spp of MFF
  • MFF aquired transplacentally
  • adults removed or died but still have circulating MFF
  • contaminated test
38
Q

if antigen test is variable and MFF is negative or positive

A

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

39
Q

what is the susceptibility gap

A

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
Q

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

A

Wolbachia pipientis

41
Q

what do we know about Wolbachia and Dirofilaria

A

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

42
Q

killing adult worms

A

melarsomine dihydrochloride (immiticide)

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

43
Q

what can help control clinical signs of PTE during HW tx

A

Steriods

44
Q

What can help treat wolbachia and weaken HW before immiticide tx

A

doxycycline

45
Q

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

A

moxidectin (advantage multi)

46
Q

cats infected with HW get what condition

A

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

47
Q

stage 1 of HARD in cats

A

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

48
Q

Stage 2 of HARD in cats

A

worms dying = inflammation and PTE

worms rarely mature in cats

49
Q

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

A

PTE

50
Q

dz in canines vs felines depends on

A

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

51
Q

worms are __ lived in dogs/cats

A

long (dogs)

short (cats)

52
Q

MFF in cats

A

usually amicrofilaremic

53
Q

what organs are affected in dogs v cats

A

dogs: hear and lungs
cats: lungs

54
Q

treatment of HW in dogs vs cats

A

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

Parasitology 2018 (8 decks)

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