Heartworm Disease Part II

Question 1

what is the primary screening test for heartworm in dogs?

Answer 1

antigen tests

Question 2

what is the primary screening test for heartworm in cats?

Answer 2

antibody tests

Question 3

what does heartworm antigen testing test?

Answer 3

protein released from adult female reproductive tract

Question 4

why should cats be tested for both heartworm antigen and antibody?

Answer 4

much less sensitive due to low worm burdens

Question 5

what does a positive heartworm antibody test indicate?

Answer 5

exposure, not active infection necessarily

Question 6

how can you confirm diagnosis of heartworm in a cat after a positive antibody test?

Answer 6

antigen testing and/or echo

Question 7

what is the most sensitive microfilaria test?

Answer 7

modified Knott’s test or some other concentration test

Question 8

should you test dogs for microfilaria that are heartworm positive by antigen test?

Answer 8

yes- always

Question 9

how many cats with heartworm disease are amicrofilaremic?

Answer 9

more than 2/3

Question 10

if an animal is microfilaremic, what should you check?

Answer 10

confirm species as Dirofilaria immitis
rule out Acanthocheilonema reconditum

Question 11

what is the primary manifestation of heartworm disease on radiographs?

Answer 11

pulmonary disease

Question 12

what is the dose of ivermectin for heartworm?

Answer 12

6-12 microgram/kg

Question 13

what stages of larvae to macrolides kill?

Answer 13

L3 and L4

Question 14

which dogs should be on heartworm preventative?

Answer 14

every dog over 8 weeks of age

Question 15

what should felines be on to prevent heartworm disease?

Answer 15

macrolide preventative

Question 16

what are the goals of heartworm treatment?

Answer 16

kill Wolbachia
eliminate microfilaria
kill adult worms
minimize pulmonary parenchymal and arterial pathology
treat right CHF and significant PHTN if present

Question 17

why do we pre-treat for 1-2 months with doxycycline and a macrolide before giving melarsomine dihydrochloride?

Answer 17

melarsomine dihydrochloride only toxic to L5 and adults

Question 18

can melarsomine dihydrochloride be given to cats?

Answer 18

no

Question 19

when does peak worm death occur?

Answer 19

1-3 weeks post treatment of melarsomine dihydrochloride

Question 20

what are the ancillary therapies for heartworm?

Answer 20

exercise restriction
doxycycline
ivermectin
corticosteroids

Question 21

what can be found of physical exam with heartworm with the heart?

Answer 21

no abnormalities
weight loss and cachexia
loud and/or split S2
murmur of tricuspid valve regurgitation +/- right-sided thrill
S3 gallop
jugular venous distension, hepatosplenomegaly, abdominal effusion

Question 22

who cannot be antigen positive?

Answer 22

puppies <6 months old

Question 23

why is detection of microfilaria an insensitive method of diagnosis for heartworm?

Answer 23

prevalence of occult infection

Question 24

what are the causes of occult infection?

Answer 24

iatrogenic
immune-mediated
unisex infection
prepatent infection

Question 25

what is echo used to evaluate for in dogs with heartworm disease?

Answer 25

severity of pulmonary hypertension
caval syndrome
cor pulmonale
parasite burden
concurrent heart disease

Question 26

why is extra-label use of ivermectin at 50 microgram/kg not recommended?

Answer 26

anaphylactic shock: rapidly microfilaricidal

Question 27

can melarsomine dihydrochloride be given to dogs with caval syndrome?

Answer 27

no

Question 28

can you give melarsomine dihydrochloride to cats?

Answer 28

no

Question 29

what are the possible side effects of melarsomine dihydrochloride?

Answer 29

local pain/inflammation
GI signs
neurologic complications
pulmonary edema
renal and hepatic toxicity
pulmonary thromboembolism
death

Question 30

what are the ancillary therapies for heartworm in dogs?

Answer 30

exercise restriction
doxycycline
ivermectin
corticosteroids
heparin/antiplatelet agents
oxygen, phosphodiesterase inhibitors
RCHF therapy