L19 - HW Infection in Cats

How is HW infection different in cats?

1. Low parasite load → only 1-2 worms

2. Microfilaria are usually not produced

3. Adults are short-lived

“Suitable host, but not a preferred host” → doesn’t significantly contribute to maintenance of parasite in host populations

What causes HARD?

• Heartworm Associated Respiratory Disease

• Inflammation of pulmonary vasculature → occlusion of airways

• Asthma-like dyspnea, coughing, vomiting, tachypnea

• Basophilia

What is the problem with using serology to diagnose feline HW?

• Can be falsely negative!

What is the facilitating factor for bronchial reactivity with HARD?

Wolbachia

What are the three phases of HARD?

• Phase 1: with clinical signs

• Phase 2: no clinical signs due to immunomodulatory activity by the parasite (downregulates immune system)

• Phase 3: clinical signs reappear as the adults are dying and no longer has control over the immune system

What’s the benefits of serologic testing in cats?

• Antibody Testing → high sensitivity (can have false +)

  • Good for early stage disease

  • Not good for late stage disease

• Antigen Testing → high specificity (can have false -, up to 50% of the time)

  • Good for Phase 2 and 3 disease

  • Does require adult worms to be present

How do you treat and prevent feline HW?

• No adulticidal regimen

• Manage symptoms → steroids to alleviate inflammation of pulmonary vasculature

• Monthly HW prophylaxis

  • Don’t matter what kind!

  • Ivermectin → minor long-term adulticidal

  • Doxycycline → manages Wolbachia

Why should felines be on HW prophylaxis?

• HW disease in cats is more severe than dogs and often fatal

• No safe and effective adulticide therapy

Why don’t we typically test for feline HW?

• Don’t have microfilaremia

What HW products are toxic to cats?

Pyrethrin-based products

What causes HW in ferrets?

Dirofilaria immitis → same as dogs/cats

What are the microfilaremia levels in ferrets? Worm load?

Low and transient → similiar to cats

Similiar adult worm levels as dogs

Are cats a competent host for the transfer of the disease to dogs?

No, HW in cats are primarily single sex infections and don’t have microfilariae to transfer to dogs (but dogs can transfer to cats)