Heartworm Disease in Dogs and Cats: Diagnosis, Treatment, and Prevention

Where do adult heartworms reside in dogs?

Heart and pulmonary arteries

What is the scientific name for the heartworm?

Dirofilaria immitis

How long can adult heartworms live in dogs?

5-7 years

What is the infective stage of heartworm larvae?

L3

What is the prepatent period for heartworm in dogs?

6-7 months

How long does it take for L1 to develop into L3 inside the mosquito?

13-30 days

What diagnostic test detects antigens from adult female worms?

Antigen test (ELISA)

When should efficacy be confirmed post-treatment?

6 months.

What are the main monthly preventives for dogs?

Ivermectin, Milbemycin, Selamectin, Moxidectin

What wild species serves as a major heartworm reservoir?

Coyotes

What percent of coyotes are heartworm positive?

~70%

Where is canine heartworm most prevalent geographically?

Gulf Coast, Atlantic Coast, Mississippi River

What type of microfilaria is nonpathogenic?

Dipetalonema

What are typical radiographic findings in heartworm disease?

Enlarged pulmonary arteries; right heart enlargement

What diagnostic imaging confirms pulmonary vessel damage?

Thoracic radiographs

What is the recommended post-adulticide care?

Strict exercise restriction

Q: What medication is used for post-treatment inflammation?

: Corticosteroids

Q: What case in the lecture showed lapse in prevention?

: Mr. Smith's "Buddy"

Q: What was the outcome of Buddy's case?

: Heartworm positive after missed prevention doses

What percent of infected cats may experience sudden death?

10-20%

What does HARD stand for?

Heartworm-Associated Respiratory Disease

Q: What is the primary supportive treatment?

: Corticosteroids, bronchodilators

Why are adulticides not recommended?

Risk of thromboembolism

What are surgical options?

Worm removal via jugular vein

What are approved feline preventives?

Moxidectin, Selamectin, Ivermectin, Milbemycin

Why do cats rarely show microfilaremia?

Strong immune response

What larval stages cause disease?

L4, L5

What does the antibody test detect?

Exposure to larvae/immature worms

Q: When do antibodies appear?

: ~2 months post-infection

When does antigen appear?

7-8 months post-infection

Q: Why can antigen tests be negative in infection?

Male-only or low worm burden

Q: What radiographic signs suggest heartworm?

: Enlarged/tortuous pulmonary arteries

What percent of b+ cats have normal radiographs?

~45%

Where are worms seen on echo?

Pulmonary arteries

Why is echo less reliable in cats?

Low worm numbers or ectopic sites

How often repeat serology?

Every 6-12 months.

What percent of infected cats are indoor only?

25%

Q: What organs make up the GI tract?

: Mouth, esophagus, stomach, intestines, rectum

What accessory organs aid digestion?

Liver, pancreas, salivary glands

What is peristalsis?

Movement of ingesta through GI tract

What can cause impaired motility?

Obstruction, ileus, systemic disease

What detects circulating toxins triggering vomiting?

Chemoreceptor trigger zone (CTZ)

What receptors mediate emesis?

Dopamine, serotonin, histamine, muscarinic

What are complications of chronic vomiting?

Dehydration, electrolyte loss, aspiration pneumonia

What defines constipation?

Infrequent, difficult defecation with hard feces

What is megacolon?

Dilated, atonic colon

What species often develop megacolon?

Cats

Treatment for megacolon?

Stool softeners, fluids, colectomy

What is anorexia?

Loss of appetite

Common causes of anorexia?

Systemic illness, oral pain, stress

Q: Which breeds at risk for parvo?

: Rottweiler, Pit Bull, Doberman, GSD

Q: What causes HGE?

: Unknown, possibly Clostridium

Treatment for HGE?

IV fluids, supportive care

GDV is also called?

Bloat or gastric torsion

Q: Treatment for GDV?

: Gastric decompression and gastropexy

Difference between small and large bowel diarrhea?

Small = high volume; Large = mucus/blood

Common chronic GI disease in cats?

IBD

First-line drug for IBD?

Prednisone

How many permanent teeth do dogs have?

42

How many permanent teeth do cats have?

30

Q: What is the most common disease over 3 years?

: Periodontal disease

Q: What causes periodontal disease?

: Plaque accumulation

Stages of periodontal disease?

I-IV (gingivitis to bone loss)

What are tooth tissues?

Enamel, dentin, pulp, cementum

What anchors teeth?

Periodontal ligament

Occlusion types in dogs?

Mesaticephalic, brachycephalic, dolichocephalic

Example mesaticephalic breed?

Labrador Retriever

Q: Example brachycephalic breed?

: Bulldog

Q: Example dolichocephalic breed?

: Greyhound

What initiates periodontal disease?

Bacterial plaque

Q: What follows gingivitis?

: Bone and attachment loss

Stage I periodontal disease?

Gingivitis only

Q: Stage IV periodontal disease?

: Severe bone loss

Dental exam frequency?

Every 6-12 months

Q: Radiograph for bone loss?

: Dental radiograph

Signs of dental disease?

Halitosis, drooling, difficulty eating

Most effective home care?

Daily brushing

Non-anesthetic dentals are?

Unsafe and ineffective

Q: Multimodal pain management?

: Opioids, NSAIDs, local blocks

Q: Feline resorptive lesions?

: Painful tooth erosion

Q: Treatment for resorptive lesions?

: Extraction

Q: CUPS stands for?

: Chronic Ulcerative Paradental Stomatitis

Case with severe tartar and tooth loss?

Paintbrush (Aussie Shepherd)

Case with retained roots?

Cooper (Yorkie)

Q: Device to fix mild malocclusion?

: Incline plane

Dental procedure for fractures?

Root canal

Common cause of fractures?

Chewing hard objects

Why avoid bones?

Cause fractures

Q: Treatment for stomatitis?

: Extractions and anti-inflammatories

Q: What test detects microfilariae in the blood?

: Modified Knott's test or Difil™ filter test

What are the four clinical stages of heartworm disease?

Stage I-IV (I = minimal signs; IV = Caval Syndrome)

What are the hallmark signs of Caval Syndrome?

Collapse, pallor, weak pulses, hemoglobinuria, sudden death

What antibiotic is used to target Wolbachia bacteria in heartworm-positive dogs?

Doxycycline

What is the recommended adulticide for heartworm treatment?

Melarsomine

When should you confirm adulticide efficacy post-treatment?

6 months post-treatment via antigen test

Why are cats poor hosts for heartworms?

They have strong immune responses and low adult worm survival

What does HARD stand for in feline heartworm disease?

Heartworm-Associated Respiratory Disease.

Q: Why is heartworm testing in cats unreliable?

Antigen tests only detect adult female worms, and microfilaremia is rare

What combination of tests helps diagnose feline heartworm disease?

Antigen, antibody, radiographs, and echocardiogram

What is the primary supportive treatment for feline heartworm disease?

Corticosteroids and bronchodilators