Heartworm Disease Flashcards
How is heartworm disease transmitted?
Transmitted by many mosquito species.
What is the cause of heartworm disease?
Dirofilaria immitis- a nematode.
What are the wildlife reservoirs of heartworm disease?
- Foxes.
- Racoons.
- Seals.
- Sea lions.
- Wolves.
- Coyotes.
What are the domestic reservoirs of heartworm disease?
- Ferrets.
- Cats.
- Dogs.
What climates has heartworm disease been reported in?
- Temperate.
- Semi-tropical.
- Tropical.
*Has been reported in all 50 U.S. States.
What is the first step of the heartworm lifecycle?
Mosquitos ingest microfilaria.
What is the second step of the heartworm lifecycle?
The microfilaria molt into the L1 stage, then the L2 stage, and finally the L3 stage in the mosquito. Takes 2 weeks.
What is the third step of the heartworm lifecycle?
The mosquito bites a mammal and the L3 larvae enters the tissues of the host.
What is the fourth step of the heartworm lifecycle?
The L3 larvae mature to L4 larvae in the tissue of the host. 3-12 days post-infection.
What is the fifth step of the heartworm lifecycle?
The L4 larvae develop into immature adults. 50-70 days post-infection.
What is the sixth step of the heartworm lifecycle?
The immature adults migrate to the heart (specifically the pulmonary artery and right ventricle) and develop into sexually mature adults. 70-120 days post-infection.
What is the seventh step of the heartworm lifecycle?
The mature adults produce microfilaria. Happens 6-months post-infection.
How long are adult heartworms?
15 cm.
What does the presence of adults in the pulmonary vasculature cause?
- Direct mechanical trauma.
- Immune system stimulation.
- Inflammation (thickening of the vessel walls).
What do the symptoms of heartworm disease result in?
- Inflammation in the lungs.
- Pulmonary hypertension.
- R. side heart failure.
What are the clinical signs of heartworm disease in canines?
- Ascites.
- Cough.
- Collapse.
- Decreased activity.
- Syncope.
- Unthrifty appearance.
- Cyanosis.
- Dyspnea.
What are the signs of heartworm disease in cats?
- Vomiting.
- Dyspnea.
- Diarrhea.
- Cough.
- Weight loss.
- Heartworm associated respiratory disease (HARD): Asthma-like symptoms secondary to allergic responses to the heartworms.
What are the methods used to diagnose heartworm disease in dogs?
- Microfilaria test.
- Antigen test (ELISA).
*Radiographs to determine the stage of the disease.
What is the antigen test (ELISA) being used to detect?
A protein produced by mature female heartworms.
*A strictly male heartworm infection would be undetectable using this method.
At what point in a heartworm infection can an antigen test (ELISA) first be used?
5-6 months post-infection.
What are the 3 methods used to conduct a microfilaria test?
- Modified Knott’s test.
- Millipore filter test.
- Direct blood smear.
What methods are used to diagnose heartworm disease in cats?
- Radiographs.
- Ultrasound/echocardiogram.
- Antibody tests: indicates exposure, but is not definitive.
- Antigen tests: high false negative rate.
Why is heartworm disease difficult to diagnose in cats?
- Small worm burden.
- Can have male heartworms only infections.
What is the treatment plan for a heartworm positive dog?
Melarsomine and doxycycline.
*After using radiographs and lab work to determine the stage of heartworm disease the patient is at.
What is melarsomine?
An arsenical compound that is used to poison the heartworms over the course of 3 injections in a 2 month period.
Why is doxycycline used as part of a heartworm treatment?
To kill the bacteria Wolbachia pipiens.
What is Wolbachia pipiens?
An intracellular bacteria that lives in the heartworm and is necessary for both the normal maturation and reproduction of the heartworm. Upon the death of the heartworm, the bacteria release endotoxins that exacerbate the symptoms of heartworm disease.
What is the treatment plan for a cat with heartworm disease?
No curative treatment for cats exists, so symptomatic treatment only.
How is heartworm disease prevented?
Year-round heartworm prevention for both indoor and outdoor animals.
ex: Ivermectin, Moxidectin, Selemectin, Milbemycin oxime. Macrocyclic lactones.
