Heartworm Disease Part I

Question 1

what is the definitive host of Dirofilaria immitis?

Answer 1

dog

Question 2

what is the infective stage of Dirofilaria immitis?

Answer 2

L3 larvae

Question 3

what is class I of heartworm disease?

Answer 3

evidence of disease absent or mild
usually identified by routine screening

Question 4

what is class IV of heartworm disease?

Answer 4

caval syndrome

Question 5

what is class III of heartworm disease?

Answer 5

severe heartworm disease
typically with cor pulmonale

Question 6

“heartworm” is rpimarily a disease not of the hart but of the _____________________

Answer 6

pulmonary arteries

Question 7

when do vascular changes occur with heartworm disease?

Answer 7

within 3 weeks of adult heartworm transplantation

Question 8

what on pathology is pathognomonic of dirofiliriasis?

Answer 8

villous endarteritis

Question 9

what is villous endarteritis?

Answer 9

proliferation of smooth muscle cells of tunica media
migration of smooth muscle cells to intima and production of villi

Question 10

what is a common complication of adulticide therapy 1-3 weeks after treatment?

Answer 10

adult worm death catastrophic consequences

Question 11

why can pulmonary thromboembolism occur with heartworm disease independently of worms?

Answer 11

platelet activation
endothelial damage
chronic inflammation
glomerulonephropathy
blood stasis

Question 12

why can chronic pulmonary arterial disease result in cor pulmonale?

Answer 12

leads to pulmonary hypertension which leads to right ventricle pressure overload
this leads to right ventricle hypertrophy and right sided heart failure eventually

Question 13

what do microfilariae sequestered in the lungs cause?

Answer 13

intense eosinophilic infiltration

Question 14

what is happening in caval syndrome?

Answer 14

heartworms are present within the heart

Question 15

what does eosinophilic infiltration from microfilariaee sequestered in the lungs look like on chest radiographs?

Answer 15

diffuse interstitial to alveolar infiltrates
can progress to granulomatous-type reactions- looks like metastases

Question 16

what does caval syndrome require?

Answer 16

immediate surgical removal of adults

Question 17

what can cause glomerular disease from heartworm disease?

Answer 17

immune-mediated glomerulonephropathy: immune complexes
low cardiac output

Question 18

when can disseminated intravascular coagulation happen with heartworm disease?

Answer 18

endothelial damage with severe disease
caval syndrome
especially post-adulticide

Question 19

what can increase the host immune response to Dirofilaria immitis?

Answer 19

Wolbachia organisms

Question 20

what are Wolbachia organisms?

Answer 20

obligate, intracellular gram negative bacteria
critical for certain stages of filarial life cycle

Question 21

what decreases pulmonary pathology associated with adulticide?

Answer 21

pre-treatment with doxycycline and ivermectin

Question 22

what are aberrant heartworm infections characterized by?

Answer 22

ectopic migration of larvae

Question 23

are cats resistant to heartworm disease compared with dogs?

Answer 23

yes: 10% or canine infection rate

Question 24

how often are cats microfilaremic?

Answer 24

rarely

Question 25

what is feline heartworm-associated respiratory disease often confused with?

Answer 25

feline asthma

Question 26

what is important when considering a cat with heartworm compared to a dog?

Answer 26

cats have smaller pulmonary artery trees: embolizations, even small ones, can have disastrous effects

Question 27

what are consistent findings of feline heartworm disease?

Answer 27

dyspnea and cough

Question 28

what is class II of heartworm disease?

Answer 28

moderate disease with coughing and exercise intolerance but no heart failure radiographic changes evident

Question 29

what cells contribute acutely to pulmonary arterial disease?

Answer 29

neutrophils eosinophils

Question 30

what can adult worm death cause?

Answer 30

embolization: thrombosis, inflammatory pulmonary infarction, acute R-sided CHF, respiratory failure, vascular rupture

Question 31

why can pulmonary thromboembolism occur with heartworm disease?

Answer 31

death of adult worms: thrombus hypercoagulable state

Question 32

what can microfilariae sequestration in the lungs result in?

Answer 32

occult infections: no circulating microfilariae

Question 33

where might adult worms be present in caval syndrome?

Answer 33

right ventricle right atrium vena cavae hepatic veins

Question 34

what does research show with Wolbachia organisms and heartworm disease?

Answer 34

targeting Wolbachia in addition to D. immitis may greatly decrease pathology and improve outcome

Question 35

when might a systemic arterial thrombosis occur with aberrant heartworm infections?

Answer 35

if L5 stage migrates into arterial system