Cardiovascular - Heartworm Flashcards
Heart worm species
Dirofilaria immitis
Life span of heart worm in dogs
6-7m, 184-210d
Life cycle of HW in dogs dependent on
ambient temperature ad Wolbachia
Life cycle of HW in dogs
adult worms live in PA
after mating female worms release microfilaria (mf) into circulation
mf ingested by female mosquitos - become L1
2 melts over 8-17d period to L3
L3 transmitted from mosquito to dog
L3 to L4 in Sc tissue over 1-12d, then final molt to immature adult (S5)
S5 migrates to vasculature then to PA to complete maturation
T/F: prevalence of HW disease in dogs is increasing
true
heart worm infection = heart worm disease?
no, heart worm disease occurs when heart worm infection is prolonged or severe
Features of heart worm disease in dogs
pulmonary artery and pulmonary parenchyma injury, pulmonary hypertension, R sided cardiac dysfunction, glomerulonephritis, anemia, thrombocytopenia, canal syndrome, DIC
What is considered the onset of heart worm disease in dogs?
damage to the pulmonary artery
What occurs in the pulmonary aa in dogs as a result of adult worms living there?
inflammation, endothelial damage, myointimal proliferation, disruption of vascular integrity, fibrosis, pulmonary hypertension
Living worms in dogs can create
mechanical obstruction within the pulmonary arteries
Dead worms in dogs induce
thrombosis and inflammation
Outcome of pathophysiology of HWD in dogs
decreased return to left artery and ventricle (preload) = low systemic pressure
What type of hypertrophy occurs in right ventricle in dogs?
concentric
2 things that result in increased pulmonary vascular resistance in dogs
structural changes causing narrowed pulmonary lumen
vasoactive substance from worms, endothelium, and platelets cause vasoconstriction
What sided heart failure may you see as a result of HW disease in dogs
right sided CHF
Which is FALSE regarding pulmonary parenchymal disease resulting from HWD?
A) decreased vascular permeability into surrounding tissue
B) eosinophilic granulomatosis as result from host response
C) pulmonary thromboembolism (PTE) seen
D) post PTE lung consolidation
A - increased vascular permeability to tissue (fluids, cells, toxins)
Wolbachia pipientis
intracellular, gram -, live in D. immitis
endotoxins and surface proteins have been implicated in pathogenesis and adverse reactions associated wth HWD
Doxy effective attracting Wolbachia
T/F: doxycycline is effective at reducing/eliminating wolbachia and reduces larval and adult stages of D. immitis in dogs
true
Heartworm disease and glomerulonephtitis in dogs
secondary to antigen-antibody deposition, results in albuminuria (and potentially hypoalbuminemia)
What is caval syndrome in dogs?
mechanical obstruction by worms of blood flow to R side of heart and vena cava, only occurs if worm burden is heavy
hemolytic anemia and cariogenic shock result (rare but lifethreatning)
T/F: aberrant migration of worms to other tissues (neuro, muscular, ocular, systemic aa.) more common in dogs than cats
false, more common in cats
Clinical signs of HWD in dogs
most dogs asymptomatic
exercise intolerance, weight loss, lethargy, cough, tachypnea, dyspnea, hemoptysis, abdominal distension, syncope or collapse, hematuria
PE findings on HWD dog
may be normal weight loss and poor BCS split S2 murmur due to tricuspid regurgitation (right apical systolic) gallop abnormal lung sounds tachypnea, dyspnea R sided CHF
T/F: thoracic rads are helpful to diagnose HWDin dogs
True! Look for large, dilated, tortuous pulmonary aa
look at lung parenchyma for interstitial infiltrates
look for R sided cardiac enlargement
CBC abnormalities associated with HWDin dogs
neutrophilic, eosinophilia, basophilia, anemia, thrombocytopenia
Why may you see elevated liver enzymes in a HWD dog?
hepatic congestion from R sided CHF
urinalysis of a dog w HWD may reveal
albuminuria
When is an echo indicated in a HW patient?
if there is concern for pulmonary hypertension and/or canal syndrome
What is the test of choice if an arrhythmia is ausculted on a HWD patient (dogs)?
echo
Best treatment for HWD in dogs?
macrocyclic lactone preventative
Doxycycline
Exercise restriction
adulticide therapy with melarsomine dihydrochloride
Macrocyclic lactone preventative in dogs
prevents further infection reduces or eliminates microfilaria destroys developing L3 and L4 started day HWI is diagnosed ivermectin, salamectin, moxidectin
Which would you NOT give to a microfilaremic dog? Why? A) ivermectin B) Milbemycin C) Moxidectin D) Selamectin
B - milbemycin
is a potent microfilaricide, death of too many worms at once can cause anaphylaxis
Two uses of doxycycline in dogs
reduce/eliminate Wolbachia
reduce Mf and other stages of D. immitis
Why is exercise restriction imperative in HWD dogs?
reduce risk of thromboembolic complications
3 dose “split dose” protocol in dogs
highly effective at eliminating adult worms
reduces risk of post-adulticidal complications
use melarsomine dihydrochloride, organic arsenical rapidly absorbed after IM injection
dogs with intra-cardiac worms/caval syndrome should not be treated with adulticide until worms. have been extracted
“slow kill” of adults with macrocyclic lactones in dogs
ongoing damage to pulmonary artery and lungs
method not recommended, could be used for a patient in which 3 dose with melarsomine is not an option
Adulticide drug of choice in canines with HWD
melarsomine dihydrochloride
Adjunct Tx for canines
analgesia for melarsomine injections (opioids, corticosteroids or NSAIDs)
corticosteroid therapy - prevent/tx adverse reactions to microfilaricides
What could you give a dog to treat pneumonitis, pulmonary granulomas, and pulmonary thromboembolism associated with HWD?
corticosteroids
Treatment of anaphylaxis associated with microfilaricidal therapy in dogs
uncommon except with milbemycin oxide
monitor dogs after preventative
consider pretreatment with corticosteroid and diphenhydramine
avoid milbemycin
Treatment of eiosinophilic pneumonitis or granulomatosis in dogs
corticosteroids (prednisone or prednisoloe)
often occurs early in disease course
treatment of pulmonary thrombosis or thromboembolism in dogs
supplemental O2, corticosteroid therapy, sildenafil if pulmonary hypertension severe
can cause sudden death
Treatment of pulmonary hypertension in dogs
sildenafil, supplemental O2
Treatment of congestive heart failure in dogs
(R sided)
- furosemide, sildenafil +/- pimobendan, ACE inhibitor if not hypotensive or dehydrated
abdominocentesis if ascites
delay adulticide therapy until CHF stabilized
Treatment of caval syndrome in dogs?
emergency worm extraction via jugular vein
delay adulticide therapy (at least 30 days)
Prognosis for dogs with HWD
good with asymptomatic infection
good in dogs w/ mild-moderate disease
guarded for severe HWD
Patients that develop CS, DIC, CHF, PTE, eosinophilic granulomatosis, PA disease = worse prognosis
prevention of HWD?
educate clients
T/F: cats are more resistant to heart worm infections than dogs
True, cats are unnatural host
T/F: aberrant migration of worms more common in cats
True
T/F: pulmonary disease can develop in cats even if mature adult worms never exist
true
Key differences of HWD in cats
not preferred target for mosquito
mosquito must have fed on infected dog first
unnatural host - resistant to HWI (no or few adults, often amicrofilaremic)
longer life cycle (7-8m)
aberrant migration more common
mature adults not needed for pulmonary disease to develop
If prevalence of HWI low in cats, why is it important we protect cats from D. immitis?
cats get HARD
What is HARD
Heartworm-associated respiratory disease
General info about HARD
inflammatory and proliferative disease of pulmonary aa, bronchioles and pulmonary parenchyma in cats without mature infections
Which is FALSE regarding HARD?
A) ~50% cats with immature infections develop HARD
B) HARD produces asthma like symptoms
C) HARD is a diagnosis of exclusion
D) HARD requires cats to have mature infections
D - HARD occurs in cats without mature infections
Role of PIMs in HARD?
pulmonary intravascular macrophages contribute to profound inflammatory reaction to immature and dead worms
Signalment of cats with HARD
male, 4-6y, exposure to outdoors
Acute signs of HARD
due to dead worm embolization
anaphylaxis, resp distress, dyspnea, coughing, shock, ptylism, vomiting and diarrhea, altered mentation, ataxia, vision loss, seizure, sudden death
Chronic signs of HARD
coughing, wheezing, dyspnea, lethargy, hyporexia, weight loss, exercise intolerance, vomiting, R sided CHF
PE on a HARD cat
may be normal
abnormal lung sounds, tachypnea/dyspnea, murmur, gallop, weight loss, ascites
Why is antigen test not ideal diagnostic for cat HWI?
because the antigen detected is in reproductive tract of adult female which is likely not in the cat
What diagnostic test is ideal to test cats for HWI?
antibody test
Treatment of HWI in cats
microfilaricidal not indicated because low #sadulticide therapy not recommended - high risk of mortality and morbidity
cats should receive short term corticosteroid therapy for HARD
supplemental O2, parenteral corticosteroid and bronchodilator if embolic/anaphylactic emergency
consider doxy for wolbachia and clopidogrel for PTE prevention
