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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
Are precardiac larval HW detectable with Ag tests
No
26
How are precardiac larval HW likely to be killed
SINGLE dose of preventatives (depending on product)
27
Subadult immature HW Reproductive Age
Reproductively immature | 70-180 days
28
Are immature HW Ag detectable
No
29
How are immature HW likely to be killed
MULTIPLE doses of preventatives
30
Mature HW Reproductive Age
Reproductively active 6-8 mo
31
Mature HW detectable with Ag test?
Yes. BUT ONLY FEMALES. AND ONLY IF SUFFICIENT AG PRESENT
32
When does MF production and release begin in adult HW?
6 mo but may be delayed
33
Forms of HW diseases (5)
- Live HW - Dead HW - MF - Immune mediated occult disease (including IM pneumonitis) - Caval syndrome
34
T/F Disease is due primarily to adult HW in right atrium and pulmonary arteries
F Right ventricle and pulmonary arteries
35
Villous endarteritis
When worms irritate vessel walls and produce pro-inflamm molecules that induce proliferation and inflammation of vessels
36
Emboli
Fragments of dead worms lodged in vessels
37
Vascular resistance associated with villous endarteritis causes
Increase in cardiac workload Right ventricular hypertrophy (enlargement) Coughing and hemoptysis (blood in sputum)
38
Decreased cardiac output results in
Decreased blood flow to organs - ->causes exercise intolerance - ->can see liver and kidney disease
39
T/F many HW infected dogs appear asymptomatic
T Depends on your HW tolerance. (like alcohol) Severity of canine HW disease varies
40
Mild to moderate HW disease Sx
Slight RV enlargement Mild proteinuria (indicates kidney damage) Exercise intolerance Intermittent cough
41
Severe HW disease Sx Disease
``` Severe RV enlargement Severe proteinuria Constant fatigue Persistent cough Dyspnea Acites ```
42
Vena cava sydrome or Caval syndrome
With severe HW disease Worms in vena cava and RA Worms obstruct blood flow through tricuspid valve - ->heart murmur - ->lethargy
43
How to diagnose HW infection
- Get history/clinical signs - Detect MF in blood - Detect HW Ag - ECG - Imaging - CBC
44
Tests to detect MF in blood (3)
Direct smear Modified knott's test Filter test
45
Sensitivity vs specificity
Ability to detect true (+)=sensitivity | Ability to detect true (-)=specificity
46
What if Ag test (+) but MF test (-) | 6
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
What if Ag test (-) but MF (+)
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
If you have MF (-) test, what can you do to make sure it's a true negative?
Heat treat serum and then test again to see if the blood is still (-) for MF
49
T/F Caninum serum and plasma samples contain inhibitors of D.immitis Ag detection
T
50
What is Ag test is variable and MF test is variable
``` Fluctuating Ag level due to # of female worms ``` ages of worms:metabollicaly active? quality of sample
51
Rx/Prevention of HW infection (3)
Removal of adult HW (surgical extraction) Removal of MF Place on preventatve (slow kill)
52
Immiticide get rid of
Adult worms
53
Preventatives have what type of adulticidal properties
Slow
54
Ivermectin adulticidal effectiveness
95-995 if administered continuously for 30 months+
55
Why should you remove MF?
They can cause disease They're a source of infection and can become resistance
56
How to get rid of MF?
Eliminated after monthly use of preventives.
57
Explain HW in cats lifecycle
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
Canine vs feline | More susceptible to HW infection
Dogs=high | cats=low
59
Canine vs feline | Many worms? Fewer worms?
Dogs=more | cats=fewer
60
Canine vs feline | Disease depends on
Dogs= disease depends on dog size and # of worms | Cats=few worms can cause disease
61
Canine vs feline | Lives of worms
Dogs=long lived worms | Cats=short lived worms
62
Canine vs feline | MF
Dogs=usually microfilaremic | Cats=usually amicrofilaremic
63
Canine vs feline | Organs affected
Dogs=heart and lungs | Cats=lungs most often affected
64
Canine vs feline | Diagnosis
Dogs=generally easy to diagnose | Cats=usually requires multiple tests
65
Canine vs feline | Rx
Dogs=Rx available Cats=only symptomatic Rx `
66
Canine vs feline | Ectopic infections
Dogs=less common | Cats=more common
67
Canine vs feline | Preventatives
Preventatives available for both
68
Canine vs feline | Ab test/Ag test
Dogs=don't have Ab test. Have Ag test | Cats=have Ab test. Can't use Ag test
69
Circulating MF in cats
Takes longer to develop in cats
70
Cat HR disease symptoms (3)
Asymptomatic (90%) Chronic (10%) Peracute (1%)
71
Wolbachia - What is it - Type of parasite - Habitat - Importance
- 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
Wolbachia is related to
Ehrlichia and Anaplasma sp
73
Will pretreatment of wolbachia with tetracyclines or doxycycline reduce post-adulticidal rxns in lungs ?
Research says yes
74
Will combinations of preventatives and doxycycline (for Wolbachia) expedite elimination of adult worms and MF
Research says yes
75
Acanthocheilonema reconditum - Host - Location - Structure
-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
Acanthocheilonema reconditum life cycle
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
Acanthocheilonema reconditum - pathogenesis - Rx - Importance
- No path - No Rx needed - MF can be confused w/D. immitis.

Parasitology (6 decks)

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