Heartworm Disease Flashcards
What challenges are there with antigen tests in feline Heartworm disease?
Antigen tests are highly specific in detecting ADULT FEMALE. heartworm infection, but their sensitivity depends on sex, age, and number of worms, therefore Antigen tests are normally negative in cats. Cats have lower worm burdens. Also, AG tests can be variably positive 7 months after infection. During the first five months cats will often exhibit symptoms of HARD, during which time the antigen tests are negative.
If you have a suspected false negative on an antigen test, what measure can be taken to decrease false negatives?
Heating the sample, because it will break the Ag-Ab complexes.
Cats living strictly indoors account for ___% of all feline HW infections?
25%
Cats typically have a lower/higher worm burden vs dogs?
Lower. They are atypical hosts. A cat with 2-3 worms is still considered heavily infected.
Describe caval syndrome in a dog and how does it need to be treated?
Venous inflow to heart is obstructed by mass of worms leading to low cardiac output and CV shock. As worm burden increases worms migrate to RV, RA and caudal vena cava. Dogs with 40 plus worms are at increased risk. Worms have to be surgically removed to treat the condition. Reported survival is 50-80%
Pulmonary eosinophillic granulomatosis can be a complication of HW disease, describe the condition.
Hypersensitivity reaction to HW antigen or immune complexes. Commonly results in pulmonary granulomas, also can involve LN, trachea, tonsils, spleen and gastrointestinal tract. Lab work findings will often be a leukocytosis, neutrophillia, eosinophillia, hyperglobinemia. This disease is often treated initially with prednisone. Additional cytotoxic treatment may be needed with cyclophosphamide or azathioprine. Surgical removal can be considered.
Allergic/eosinophillic pneumonitis
Immune mediated reaction to dying larvae in pulmonary vasculature. Cough, crakles and dyspnea can be noted. Diffuse interstitial/alveolar infiltrates especially in caudal lung lobes. Prednisone often results in a rapid and marked improvement.
PTE is most likely to occur when in HW treatment?
7-10 days but can occur up to 4 weeks post. Treatment is rest, prednisone, oxygen, sildenafil, anticoagulant treatment +/- bronchodilators, cough suppressant
When do you retest after adulticidal treatment?
6 months. If positive it may be due to a latent worm die off. repeat in another 6 months, if positive at that point decide on if you will treat based on how patient is doing clinically
Describe recommended HW society adulticidal treatment?
3 dose split protocol with melarsomine dihydrochloride. Dose 1 administered, 1 month later perform 2 treatments 24 hours apart. First dose kills 50 percent of the worms, after the second/third 98%. 3 dose treatment acutally leads for a more gradual worm kill. Has greater potential for arsenic toxicity
Which prevention has the most mircrofilarcidal activity?
Milbemycine oxime (interceptor) If this is given to HW + dog, recommend monitoring in hospital
2 months prior to HW treatment, what medications do you start?
Macrocytic lactone. Watch in hospital if mircrofillaria positive. Doxycycline
Clinopathologic findings for HW disease
Eosinophillia, basophilia, neutrophilia, monocytosis. Mild regenerative anemia to sever anemia with intravascular hemolysis.
What are possible radiographic changes from HW disease?
PAH changes- RV enlargement with pulmonary trunk buldge. Patchy pulmonary infiltrates suggestive of pneumonitis, PTE, or fibrosis. Eospinophillic granulomatosis, right sided heart failure
Class I HW disease
Occasional cough, fatigue on exercise, no radiographic changes, no lab work changes
Class II HW disease
Occasional cough, fatigue on exercise, +/- RV enlargement, pulonary art enlargement, pnemonitis labs plus minus mild anemia and mild proteinemia
Class III HW disease
Loss of condition, fatigue on exercise/mild activity, occ persistant cough, dyspnea, +/- heart failure
Radiographs R ventricular enlargement, moderate to severe pul art enlargmeent, mixed alveolar opacities. Labs can have a PCV <30% and proteinuria
Class IV HW disease
Caval syndrome
Of all dogs diagnosed with heartworm disease, how many are asymptomatic?
70%
Dirofilaria immitus microfilaria VS acanthocheilonema microfilaria
Dirofilaria have a straight body with a taper head, >6 mm wide, Acanthocheilonema have a curved body with blunt head <6 mm sie
How do you test for microfilaria?
Non concentrated test, modified knott test
Why would you heat a HW antigen sample?
False negatives can occur due to antigen-antibody complexes. Heat blood for 10 minutes at 104, this can separate the complexes and make a previously false negative test postive. It is only recommended to do a heat test if you suspect HW disease and the test is negative
Mot HW antigen tests do not detect infections less than XX months old?
5
Male or female worms are NOT detected?
Male
