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Pulmonology > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What is dirofilaria immitis?

A

Parasitic roundworm spread through mosquito bites

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2
Q

Describe the heartworm life cycle

A
  1. A HW positive dog is bitten by a mosquito. The mosquito picks up the microfilaria (L1).
  2. The L1 larva mature through L2 and L3 in the mosquito.
  3. The mosquito bites a dog and deposits L3 larva onto the skin which enter the body through the puncture wound.
  4. The L3 larve mature through L4 and L5 and migrate through tissues to reach lungs.
  5. L5 penetrate blood vessels and enter the pulmonary arteries.
  6. Adults in the pulmonary arteries mate and produce L1 microfilaria which can be picked up by another mosquito.
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3
Q

What are the pulmonary vascular responses to the heartworms?

A

Endothelial irritation from direct contact

Inflammatory mediators will be released

Ag-Ab complexes will be formed

Pulmonary arteries will become dilated and blunted

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4
Q

What are the pulmonary parenchymal responses to the heartworms?

A

Local inflammation
Pulmonary fibrosis
Thromboembolism of dead worms

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5
Q

How do you diagnose heartworms in dogs?

A

Blood tests- microfilarial, antigen, and antibody tests

Thoracic radiographs

ECG- maybe

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6
Q

What is the most common test in dogs?

A

Antigen test (snap 4Dx test)

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7
Q

How long does it take for the life cycle to be completed?

A

6-7 months

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8
Q

What does the anitgen test detect?

A

Mature, gravid females only

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9
Q

When should you perform an antigen test?

A

Before staring prophylaxis (unless the dog is less than 6 months old)

If they haven’t had prophylaxis/they’ve had inadequate prophylaxis

Annually in case of errors in owner compliance or dog being sneaky and spitting pill out

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10
Q

What worm might you see on a blood smear that is NOT dirofilaria immitis?

When would you suspect this worm?

A

Acanthocheilonema Reconditum- need to send to a parasitologist to confirm

Would suspect this if you have a negative antigen test but see “microfilaria” on blood smear

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11
Q

What are the advantages of testing for microfilaria in the blood?

A

It validates a (+) antigen test

It identifies a patient as a reservoir of infection

Alerts you to the possibility of a reaction when you using a microfilaricide

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12
Q

What is an occult infestation?

When would you have an occult infestation?

A

Worm infestation without microfilaria

Would have if

  1. Only have L5 worms and younger
  2. Immune destruction of microfilaria (cats)
  3. Macrocyclic lactone administration post infection
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13
Q

If you see a puppy less than 6 months old with microfilaria, what does that mean?

A

Maternal transmission of L1 and HW infestation is not present

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14
Q

How do most dogs present with HW?

A

Asymptomatic

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15
Q

What are some symptoms a dog with HW may have

A

Cough
Exercise intolerance
Lethargy
Caval syndrome

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16
Q

What is caval syndrome?

What does it result in?

A

When worms become entwined in the tricuspid apparatus

Results in tricuspid regurgitation, volume overloaded right heart resulting in right sided CHF, volume underloaded left heart resulting in decreased CO and shock, IV hemolysis, hemoglobinemia and hemoglobinuria

17
Q

What are some clinical signs of caval syndrome?

A 
Sudden onset of severe lethargy
Right sided systolic heart murmur
Dyspnea
Pale mm
Hemoglobinemia/uria
Jugular pulsations
Shock
Might have ascites/liver enlargement
18
Q

When diagnosing heartworms, what might you see on thoracic radiographs?

A

May be normal

May have enlarged, tortuous pulmonary arteries

MPA bulge

Interstitial/alveolar patterns

Right sided cardiomegaly (reverse D)

19
Q

ECG

A

Not necessary of work-up of HW

Not efficient method of diagnosis but can confirm caval syndrome

20
Q

Class 1 HW

A

Clinical signs:none/ occasional cough

Exam: normal

Rads: normal

21
Q

Class 2 HW

A

Clinical signs: occasional cough, mild to moderate exercise intolerance

Exam: increased lung sounds, fair general condition

Rads: mild PA enlargement; mixed interstitial/alveolar patterns

22
Q

Class 3 HW

A

Clinical signs: persistent cough, increased respiratory effort, moderate to severe exercise intolerance, weight loss

Exam: tachypnea, dyspnea, split S2, gallop, increased lung sounds

Rads: moderate to severe PA enlargment, RV enlargement, diffuse, severe pulmonary lesions

23
Q

Class 4 HW

A

Caval syndrome

24
Q

What is the only FDA approved adulticide

A

Melarsomine (Immiticide)

25
Q

What is fast kill?

A

Previously recommended for class 1-2 dogs, but no longer recommended because it only kills 90% of worms as opposed to 98%

26
Q

What are some side effects of melarsomine?

A

Pain/inflammation at injection site- can treat with NSAIDS
Allergic reaction- All dogs should be treated with benadryl
Pulmonary inflammation/edema
Mild cough/lethargy/fever
Pulmonary thromboembolism

27
Q

Why give doxycycline for one month before treating heartworms?

A

Kills wolbachia- an intracellular symbiotic bacteria with D. Immitis

This suppresses microfilaremia

28
Q

Why give macrocyclic lactones for two months prior to adulticide?

A

It eliminates the susceptibility gap caused by neither immiticide nor macrocyclic lactones not killing late L4-early L5

29
Q

Which macrocyclic lactone kills microfilaria the slowest?

A

Heartguard does of ivermectin

30
Q

What other medications might you give prior to adulticide therapy

A

Steroids- if clinical signs warrant

Antihistamines- if giving MLs and microfilaria +

Aspirin- NOT INDICATED

31
Q

What is the major post adulticide consequence we worry about?

A

Pulmonary thromboembolism (can’t see on radiographs)

32
Q

When is surgical extraction of the worms indicated?ca

A

Life threatening caval syndrome

33
Q

What is the controversy surrounding long term macrocyclic lactones in HW positive dogs with no adulticide?

A

Can lead to resistant strains

34
Q

When should a puppy be started on prevention

A

No later than 8 weeks old

35
Q

What HW preventions are available

A

All are macrocyclic lactones

Ivermectin (heartguard)
Milbemycin (Sentinel, Trifexis)
Moxidectin (Proheart, advantage multi)
Selamectin (revolution)

36
Q

Can you use cattle ivermectin to prevent HW in dogs?

A

Yes, but it is off label and must be careful about dosing. DON’T use in MDR1 gene deficient dogs

Pulmonology (10 decks)

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