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Parasitology > Heartworms > Flashcards

Heartworms Flashcards

1
Q

In hyper endemic areas, the prevelance of HW infection is what in outdoor dogs?

A

40-60%

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2
Q

What are some signalments and habits that result in increase chance of getting HW?

A

Being male (4x more likely than female)
Being outdoor dog (5x more likely)
Being between ages of 3-15yrs old
Being a larger breed

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3
Q

What is the main parasite that causes HW

A

Dirofilaria immitis

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4
Q

Where is D. immitis found in US?

A

Everywhere

Particularly in regions with milder climates (S/SE)

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5
Q

Hosts of D. immitis

A

Dogs, cats, ferrets, sea lions, humans, etc

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6
Q

Habitat of D. immtis adults

Aberrant sites

A

Adult worms in right ventricle and pulmonary arteries

Aberrant: right atrium, vena cava, eye, skin, CNS
—————>caval syndrome

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7
Q

Habitat of D. immitis microfilariae

A

Pre-larval stages in circulating blood

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8
Q

What does it mean if dogs can be “occult”

A

Dogs can harbour adult worms but MF are not detectable in peripheral blood

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9
Q

How to ID D. immitis worms

A

Long, slender white worms

  • ->males are 5-7 inches with corkscrew tails
  • –>females are 10-12 inches
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10
Q

What stages are within the uterus of the female D. immitis

A

Developed embryo
Pretzel stage
Stretch MF

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11
Q

Where are MF tapered?
What’s generally at the head?
Tail of MF can be

A

anterior end

Visible cellularity

Straight or hooked

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12
Q

How can you differentiate D. immitis and Acanthocheilonema reconditum

A

D. immitis is longer and wider

D. immitis has tapered head while A. reconditum has blunted head

D. immitis has cellular end while A. reconditum has clear space

D. immtis has straight tail while A. reconditum has button hook shape

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13
Q

T/F MF of D. immitis are usually greater in number than other filarids that may produce MF in dogs

A

T

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14
Q

Describe movement of D.immitis and A. reconditum MF movement on microscopic field

A

D. immitis moves actively in one position

A. reconditum has progressive directional movement

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15
Q

What are the different types of MF periodicity in D. immtis and what is seen in dogs?

A

In dogs:

  • Nocturnal periodicity: MF are present in blood during evening hours
  • Incomplete periodicity: MF never disappear completely from peripheral blood during 24 hr period

Other types of periodicity

  • Diurnal periodicity: MF are present in blood during daylight hours
  • Complete periodicity: MF disappear from peripheral blood at some time during the 24 hr period
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16
Q

What type of MF infection in dogs are considered the main source of transmission for D.immitis?

A

Dogs with low MF numbers

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17
Q

What’s the drawback for D.immitis lifecycle if there are a high number of MF in dogs?

A

If mosQ picks up too many MF frmo a dog, the mosQ it more likely to die due to overload

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18
Q

MosQ vectors

  • L3 development
  • Species that can transmit HW
  • Common vectors
  • Variability
A

-L3 have been observed in 70 species of mosQ

23 species can transmit HW

14 species of mosQ are common vectors

Distribution of mosQ are highly variable and feeding habits of mosQ are variable( cats, dogs, humans,, etc)

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19
Q

Breeding sites among mosQ species

A

Aquatic environments
Flood plains
Tree holes
Discarded tires

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20
Q

MosQ activity and HR transmission are dependent on

Why

Transmission period relationship

A

Temperature.

MF and infective larvae in mosQ require minimum avg daily temperature for life cycle development

Transmission period increases as you go south

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21
Q

Predicted HW development units based on

A

average temperatures

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22
Q

Give overview of D. immits in dogs

A
  • MosQ feeds on dog with circulating MF
  • MF develop to infective larvae (temp dependent)
  • Infective larvae are deposited at the skin surface when mosQ takes another blood meal. Larvae enter mosQ bite wound
  • Larvae undergoes 2 molts during their migration to the heart and lungs
  • Adults mature in heart or lungs, mate, and produce MF

Repeat

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23
Q

Prepatent period of D. immitis in dogs

A

5.5-7 months

for MF to form into adult worm

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24
Q

Precardiac larval HW

  • Where they going
  • Age
A

Worms en route to hear

L3 in cutaneous tissue to 70 days (L4;early adult)

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25
Q

Are precardiac larval HW detectable with Ag tests

A

No

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26
Q

How are precardiac larval HW likely to be killed

A

SINGLE dose of preventatives (depending on product)

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27
Q

Subadult immature HW
Reproductive
Age

A

Reproductively immature

70-180 days

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28
Q

Are immature HW Ag detectable

A

No

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29
Q

How are immature HW likely to be killed

A

MULTIPLE doses of preventatives

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30
Q

Mature HW
Reproductive
Age

A

Reproductively active

6-8 mo

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31
Q

Mature HW detectable with Ag test?

A

Yes.

BUT ONLY FEMALES. AND ONLY IF SUFFICIENT AG PRESENT

32
Q

When does MF production and release begin in adult HW?

A

6 mo but may be delayed

33
Q

Forms of HW diseases (5)

A
  • Live HW
  • Dead HW
  • MF
  • Immune mediated occult disease (including IM pneumonitis)
  • Caval syndrome
34
Q

T/F Disease is due primarily to adult HW in right atrium and pulmonary arteries

A

F

Right ventricle and pulmonary arteries

35
Q

Villous endarteritis

A

When worms irritate vessel walls and produce pro-inflamm molecules that induce proliferation and inflammation of vessels

36
Q

Emboli

A

Fragments of dead worms lodged in vessels

37
Q

Vascular resistance associated with villous endarteritis causes

A

Increase in cardiac workload

Right ventricular hypertrophy (enlargement)

Coughing and hemoptysis (blood in sputum)

38
Q

Decreased cardiac output results in

A

Decreased blood flow to organs

  • ->causes exercise intolerance
  • ->can see liver and kidney disease
39
Q

T/F many HW infected dogs appear asymptomatic

A

T

Depends on your HW tolerance. (like alcohol)

Severity of canine HW disease varies

40
Q

Mild to moderate HW disease Sx

A

Slight RV enlargement
Mild proteinuria (indicates kidney damage)
Exercise intolerance
Intermittent cough

41
Q

Severe HW disease Sx

Disease

A 
Severe RV enlargement
Severe proteinuria
Constant fatigue
Persistent cough
Dyspnea
Acites
42
Q

Vena cava sydrome or Caval syndrome

A

With severe HW disease

Worms in vena cava and RA

Worms obstruct blood flow through tricuspid valve

  • ->heart murmur
  • ->lethargy
43
Q

How to diagnose HW infection

A
  • Get history/clinical signs
  • Detect MF in blood
  • Detect HW Ag
  • ECG
  • Imaging
  • CBC
44
Q

Tests to detect MF in blood (3)

A

Direct smear
Modified knott’s test
Filter test

45
Q

Sensitivity vs specificity

A

Ability to detect true (+)=sensitivity

Ability to detect true (-)=specificity

46
Q

What if Ag test (+) but MF test (-)

6

A

It’s a maturing infection: MF not yet in circulation.
OR
Macrolide preventative w/o removing adult worms
OR
Use of microfilaricide w/o removing adult worms
OR
Only female worms present, no males=Unisex infection
OR
Dog s true immune mediated occult
OR
Failure to use MF concentration test

47
Q

What if Ag test (-) but MF (+)

A

MF are those of another species such as D.reconditum or D.striata…usually in low number
OR
MF were aquired transplacentally (usually few in number and seen in young dogs)
OR
Adult worms were removed or have died but MF still persist
OR
Contamination of test materials from previous samples
OR
Ag blocking (heat treament recommended)

48
Q

If you have MF (-) test, what can you do to make sure it’s a true negative?

A

Heat treat serum and then test again to see if the blood is still (-) for MF

49
Q

T/F Caninum serum and plasma samples contain inhibitors of D.immitis Ag detection

A

T

50
Q

What is Ag test is variable and MF test is variable

A 
Fluctuating Ag level due to
 # of female worms

ages of worms:metabollicaly active?

quality of sample

51
Q

Rx/Prevention of HW infection (3)

A

Removal of adult HW (surgical extraction)
Removal of MF
Place on preventatve (slow kill)

52
Q

Immiticide get rid of

A

Adult worms

53
Q

Preventatives have what type of adulticidal properties

A

Slow

54
Q

Ivermectin adulticidal effectiveness

A

95-995 if administered continuously for 30 months+

55
Q

Why should you remove MF?

A

They can cause disease

They’re a source of infection and can become resistance

56
Q

How to get rid of MF?

A

Eliminated after monthly use of preventives.

57
Q

Explain HW in cats lifecycle

A

L3 deposited by mosQ

L3 molts to L4 (1-3 days) in SQ tissue

L4 molts to L5 (50-70 days) during migration to heart

L5 (immature HW) arrive in heart and carried with blood to lungs

Many L5 die in lungs and cause lesions in lungs (3 mo)
BUT
Some L5 go to heat and lungs and can survive or die causing pulmonary lesions (6 mo) This is rare for them to live.

58
Q

Canine vs feline

More susceptible to HW infection

A

Dogs=high

cats=low

59
Q

Canine vs feline

Many worms? Fewer worms?

A

Dogs=more

cats=fewer

60
Q

Canine vs feline

Disease depends on

A

Dogs= disease depends on dog size and # of worms

Cats=few worms can cause disease

61
Q

Canine vs feline

Lives of worms

A

Dogs=long lived worms

Cats=short lived worms

62
Q

Canine vs feline

MF

A

Dogs=usually microfilaremic

Cats=usually amicrofilaremic

63
Q

Canine vs feline

Organs affected

A

Dogs=heart and lungs

Cats=lungs most often affected

64
Q

Canine vs feline

Diagnosis

A

Dogs=generally easy to diagnose

Cats=usually requires multiple tests

65
Q

Canine vs feline

Rx

A

Dogs=Rx available
Cats=only symptomatic Rx
`

66
Q

Canine vs feline

Ectopic infections

A

Dogs=less common

Cats=more common

67
Q

Canine vs feline

Preventatives

A

Preventatives available for both

68
Q

Canine vs feline

Ab test/Ag test

A

Dogs=don’t have Ab test. Have Ag test

Cats=have Ab test. Can’t use Ag test

69
Q

Circulating MF in cats

A

Takes longer to develop in cats

70
Q

Cat HR disease symptoms (3)

A

Asymptomatic (90%)
Chronic (10%)
Peracute (1%)

71
Q

Wolbachia

  • What is it
  • Type of parasite
  • Habitat
  • Importance
A
  • G- bacteria= Wolbachia pipientis (only known sp)
  • Endosymbiont in invertebrates-including filarial worms
  • Located in hypodermis, ovaries, oocytes, and embryonic stages of D. immitis
  • Important in biological and reproductive functions of their host worms
72
Q

Wolbachia is related to

A

Ehrlichia and Anaplasma sp

73
Q

Will pretreatment of wolbachia with tetracyclines or doxycycline reduce post-adulticidal rxns in lungs ?

A

Research says yes

74
Q

Will combinations of preventatives and doxycycline (for Wolbachia) expedite elimination of adult worms and MF

A

Research says yes

75
Q

Acanthocheilonema reconditum

  • Host
  • Location
  • Structure
A

-Dogs

-Adults in SQ tissues or abdominal cavity.
MF in blood

-Males=1/2 inch
Females= 1 inch
(both different structure than D.immitis)

76
Q

Acanthocheilonema reconditum life cycle

A

MF taken up by fleas or lice

Develop to infective stage in 1-2 weeks

Flea feeds on dog and worms mature in 2-3 months

77
Q

Acanthocheilonema reconditum

  • pathogenesis
  • Rx
  • Importance
A
  • No path
  • No Rx needed
  • MF can be confused w/D. immitis.

Parasitology (6 decks)

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