Cardiovascular parasites

Question 1

What is the lifecycle & clinical features of Dirofilaria immitis (canine heart worm)

Answer 1

Endemic in warm countries (L3 require >27ºC to mature)

1. Mosquito ingests L1 when biting infected dog
2. L1 develops into L3 in mosquito
3. L3 transmitted to new dog when mosquito bites dog
4. L3 migrate to heart & lungs
5. L3 develop into adult worms in pulmonary arteries & right ventricle
6. Adult worms produce eggs

Symptoms:
Narrowing of pulmonary artery
Exercise intolerance
Hydrothorax (fluid in thorax)
Hydroperitoneum (fluid in peritoneum)
Chronic cough

Question 2

What is caval syndrome

Answer 2

Dirofilaria immitis emergency
Large worm burden in right atrium & posterior vena cava
Dogs may suddenly collapse/die

Question 3

What are common diagnostic tests & their limitations for canine heart worm

Answer 3

Complete blood count
Some other diseases will give similar results

Thoracic radiographs
Enlarged right side of heart
Signs may be similar to other diseases

Electrocardiogram (ECG)

Echocardiogram
White spots are worms

ELISA
Only adult female antigens detected

Tracheal wash

Question 4

How is canine heart worm treated

Answer 4

Adult worms – Melarsomine dihydrochloride
Microfilariae – Ivermectin or Milbemycin

Surgical removal:
If large dead worm burden, surgery may be necessary as dead worms can cause thromboembolism (clot in pulmonary artery)
Done during caval syndrome

Question 5

What is the lifecycle of gastrointestinal parasites

Answer 5

1. Ingestion of infective eggs/larvae
2. Penetration of intestinal wall & migration to lungs
3. Migration through lungs
4. Maturation & reproduction in intestine