Exam 4 - Heartworm Disease Flashcards
what makes up adulticide therapy?
doxycycline for 1 month, macrocyclic lactone preventative for 3 months, & then 3 dose regimen of melarsomine + tapering steroids
what is the one state that may not have heartworms?
alaska
when is peak heartworm transmission?
july & august
what is the particular climate required for transmission of heartworms?
temperature with sustained heat for maturation of mosquito larvae
humidity
what habitats are required for mosquitos that have allowed heartworm disease to become so wide spread?
water sources, urban sprawl/heat islands, irrigation
mosquitos need water
what is the definitive host of heartworms? what are some less suitable hosts that can still become infected?
dogs!!!
cats & ferrets
can microfilaria become adults in a dog?
no - requires mosquitos
when should heartworm prevention be started? maintained?
puppies - 8 weeks old
standard prevention dose of macrocyclic lactones has been shown to be safe in all breeds, prevention recommended year round
multimodal prevention - mosquito control
T/F: there have been studies that have shown that repelling & killing mosquitoes is effective in prohibiting microfilariae transmission from dogs to mosquitoes
true
what is the difference in longevity in dogs vs cats with heartworm infections?
cats: 2-3 years
dogs: 5-7 years
T/F: there is no approved treatment for heartworms in cats & when treated, there is a high rate of complications
true
what makes up staging in a heartworm positive patient?
history - clinical signs, any preventative administered, activity level
physical exam - respiratory signs, ascites/abdominal distension, & right-sided heart murmur
diagnostics - rads & labwork
what are some mild signs of canine heartworm disease?
asymptomatic or cough
what are some moderate signs of canine heartworm disease?
cough, exercise intolerance, abnormal lung sounds
what is caval syndrome?
sudden onset of severe lethargy & weakness accompanied by hemoglobinemia & hemoglobinuria
what pathology to heartworms cause in the host?
primary damage to the pulmonary arteries & lungs, inflammation & fibrosis (eosinophilic pneumonitis), pulmonary embolization, pulmonary hypertension, right-sided heart failure, & potential glomerulonephritis from antigen/antibody complexes
do dead or live heartworms cause damage to the host?
both
what are some signs of right-sided heart failure?
ascites, jugular venous distension, & positive hepatojugular reflex
what are some differentials for a systolic right-sided heart murmur in a heartworm positive dog?
**
what may be seen on thoracic radiographs supportive of heartworm disease?
enlarged peripheral pulmonary arteries that are larger than the corresponding vein (unless there is concurrent venous distension), enlarged main pulmonary artery, & enlarged right atrium/ventricle
may have a bronchointerstitial pulmonary pattern
when would you potentially use an echo in a heartworm positive animal?
useful for patients with signs of right-sided heart failure, syncope, suspect pulmonary hypertension, or suspect caval syndrome
what may be seen on a CBC of a heartworm positive animal?
non-regenerative anemia, neutrophilia/eosinophilia/basophilia, thrombocytopenia, & microfilaria
what may be seen on a chem panel of a heartworm positive animal?
hyperglobulinemia, hypoalbuminemia, & pre-renal/renal azotemia
what may be seen on a urinalysis of a heartworm positive animal?
proteinuria
what are some reasons to test for microflaria?
identify reservoir host, identify dogs that may have a hypersensitivity reaction with preventatives, & confirming your diagnosis
what tests can be done for identifying microfilaria?
direct smear & modified knott test
why may you get a false negative heartworm antigen test in dogs & cats?
may be an all male infection, prepatent period (too early to detect), lone worm burdens (only a few females), & antigen & antibody are bound tightly
T/F: an antibody heartworm test may be positive for cats when their antigen test was negative
true
what are some examples of when you should antigen test dogs for heartworms?
newly acquired puppy - 6/7 months of age
adult dog of unknown origin - test today & in 6/7 months
following adulticide - 6/7 months after the last injection
if the owner was late or missed a preventative dose - test in 6/7 months
what is the historical therapy for microfilaricide?
single dose of ivermectin
what is the current therapy for microfilaricide?
macrocyclic lactone + doxycycline
how does ivermectin work for treating microfilaria?
takes several months to completely clear them but reduces potential adverse effects of fast kill
how does milbemycin work for treating microfilaria?
initial fast kill but takes several months to clear them out - pretreat with steroids & antihistamine
what is the FDA approved drug for microfilaricide?
topical moxidectin
T/F: if a heartworm positive animal has more worms and gets adulticide therapy, there is a higher risk of complications because there is more pathology caused by the infection
true
T/F: adulticide therapy is contraindicated in cats
true
when are adverse effects seen from adulticide therapy? what are the side effects?
7-10 days after the injection
tenderness at injection site, fever, cough, hemoptysis, anorexia
what drug is used for adulticide therapy?
melarsomine - split 3 doses
what is the split adulticide therapy protocol?
1 IM injection followed in 4-6 weeks by 2 IM injections 24 hours apart
what is the potential benefit of the split protocol for adulticide therapy?
slower kill results in less damage to pulmonary arteries
what is the potential benefit of the standard protocol for adulticide therapy?
lower cost for 2 injections & less time confined
what is the standard protocol for adulticide therapy?
2 IM injections 24 hours apart
when may slow kill be used instead of adulticide therapy?
dogs with co-morbidities preventing immiticide therapy & dogs that can’t be confined
what are the disadvantages of slow kill for adulticide therapy?
ongoing damage to the heart & lungs, patients can develop caval syndrome, dogs can develop false negative antigen tests, & it’s not typically recommended as the primary therapy
what is slow kill adulticide therapy?
heartgard plus - negative test after 3-4 year period
advantage multi + doxycycline - negative test after > 206 days
can you give 3 immiticide innjections 1 month apart so there is a lower probability of adverse effects? why?
no - 2 injections 24 hours apart are required to kill the female worms
in the split protocol, do the second set of injections have to be exactly 1 month after the first injection?
no - not if the dog had a reaction to the first injection
what is the potential benefit of using corticosteroids in heartworm treatment?
may help reduce pulmonary inflammation - pred at 0.5 mg/kg every 12 hours tapered over 3-4 weeks following each injection
what is wolbachia?
symbiotic intracellular parasite found in heartworms that has a surface protein that induces an inflammatory response in the host’s lungs & kidneys
what is the role of doxycycline in heartworm treatment?
eliminates wolbachia - 10mg/kg/day for 30 days, gets rid of them for 3-4 months
what is the benefit of combining doxycycline & monthly ivermectin for heartworm treatment?
sterilizes & damages the female worms, microfilaria removed from circulation in 9-12 weeks, & dogs had significantly less pulmonary arterial lesions & thrombi
what are the current recommendations for doxycycline in heartworm treatment?
doxycycline for 30 days prior to immiticide, macrocyclic lactone preventative at the time of diagnosis, & corticosteroids
T/F: there may be resistant microfilaria
true - but may be a lack of compliance or under-dosing, or re-infection
______ _____ is a differential diagnosis in dogs with exercise intolerance, cough, dyspnea, ascites, & dark colored urine
heartworm disease
what does a systolic right-sided heart murmur in a heartworm positive dog suggest? what diagnostic is required?
caval syndrome, pulmonary hypertension
echo is required to definitively diagnose
what should you consult for the most up to date information on heartworm disease?
american heartworm society
T/F: prevention is better than therapy for heartworm disease
true
what is the treatment for caval syndrome?
heartworm extraction & proceed with adulticide therapy
what is the prognosis of caval syndrome?
good if caught early
poor if: heart failure, renal failure, coagulopathy
what are the clues of caval syndrome?
evidence of hemolysis - anemia, dark red (port wine) colored urine
systolic right-sided heart murmur - tricuspid regurgitation
if an owner won’t confine their heartworm positive dog, what therapy are you less likely to pursue?
immiticide
what is the most important aspect of client education when doing immiticide therapy?
STRICT exercise restriction - all positive dogs for 4 weeks following each injection
why is strict exercise restriction required in all heatworm positive dogs especially those getting immiticide?
dead heartworms will embolixe the pulmonary vasculature - risk of sudden respiratory distress, pneumothorax, or sudden death is minimized when activity is limited
