Parasites of the Cardiovascular System

Question 1

Canine and feline nematodes

Answer 1

Heartworm - Dirofilaria immitis

Question 2

Size and lifespan of adult heartworm - Dirofilaria immitis (3)

Answer 2

• Females: ~25 cm long
• Males: ~15 cm long
• Live up to 7.5 years in dog

Question 3

Microfilaria (3)

Answer 3

•Larval stage of Dirofilaria immitis - infectiuous stage, circulate canine blood
•~ 300 µm long
µm long
•Dogs can be patent for 5 years

Question 4

Wolbachia endosymbiont (5)

Answer 4

• Intracellular bacterium, found in many filarial worms
• Mutualistic or symbiotic relationship
• Harboured by all stages of Dirofilaria immitis
• Required for fertility, survival & development of D. immitis
• Role in pathogenesis unclear - offers potential therapeutic target of ABs

Question 5

Life cycle of Dirofilaria immitis (8)

Answer 5

• 1). Mosquito bites (vectorborne worm infection) infected dog and ignests larvae (L1).
• 2). Within the mosquito - larvae mature from L1 into L3.
• 3). Infected mosquito bites a healthy dog and transmits larvae (L3) to the dog’s subcutaneous tissues.
• 4). Larvae mature from L3 into L4 and infest the muscles and blood vessels.
• 5). Larvae mature into adult worms and infest the pulmonary artery and right heart.
• 6). Adult worms ate and produce larvae (L1) that are released into the blood (microfilaria)
• Dog = primary definitive host - maturation and reproduction
• Mosquito = intermediate host - where development occurs + vector

Question 6

Reservoirs of Dirofilaria immitis (2)

Answer 6

• Wild canids - coyotes in USA
• Red foxes in Europe

Question 7

PPP (pre-patent period) of Dirofilaria immitis

Answer 7

Greater than or equal to 6 months, time dog is infected to seeing microfilaria in bloodstream

Question 8

What are the intermediate hosts of Dirofilaria immitis? - Species (3)

Answer 8

Question 9

Geographical distribution of Dirofilaria immitis

Answer 9

Question 10

What are the drivers for the spread of Dirofilaria immitis? (4)

Answer 10

• Global warming - climate change - warmer = inc in mosquito vectors (25-27 degrees Celcius), mosquitoes lay eggs in water bodies
• Movement of pets - cats and dogs - bring infection to non-endemic areas
• Biting behaviour of mosquitoes (exophilic to endophilic) - more likely to live indoors rather than outdoors
• Urbanisation of vector - where higher dog density = inc in transmission

Question 11

What does the pathogenesis of Dirofilaria immitis depend on? (7)

Answer 11

Question 12

Pathogenesis of Dirofilaria immitis in pulmonary arteries (5)

Answer 12

Question 13

Pathogensis of Dirofilaria immitis - long-term sequelae (2)

Answer 13

Question 14

What is the pathogenesis of severe cases with Dirofilaria immitis? (2)

Answer 14

Question 15

Clinical signs - dogs, lighter infections (2)

Answer 15

• Asymptomatic
• Sustained exercise

Question 16

Clinical signs - heavier infections - dogs (3)

Answer 16

• Loss of condition & exercise intolerance
• Chronic cough, shortness of breath
• Oedema & ascites

Question 17

What are the clinical signs of vena cava syndrome in dogs with Dirofilaria immitis? (4)

Answer 17

• Haemoglobinuria
• Jaundice
• Collapse
• May be fatal

Question 18

Dirofilaria immitis in cats - facts (5)

Answer 18

Question 19

What is HARD (heartworm associated respiratory disease)? - Cats (3)

Answer 19

Question 20

What is chronic feline heartworm disease? (3)

Answer 20

Question 21

How is Dirofilaria immitis diagnosed? (9)

Answer 21

Question 22

Prevention and control of Dirofilaria immitis (4)

Answer 22

Question 23

Vector control of Dirofilaria immitis (3)

Answer 23

Question 24

Is Dirofilaria immitis resistant to chemoprophylaxis? (6)

Answer 24

Question 25

Treatment of Dirofilaria immitis adultworms (5)

Answer 25

Question 26

Dirofilaria immitis infection in humans (4)

Answer 26

Question 27

Give some examples of other parasites of the cardiovascular system and where they are located. (4)

Answer 27

Question 28

What is schistosomiasis? (3)

Answer 28

Question 29

Ruminant species of schistosomes and their locations. (5)

Answer 29

Question 30

Life cycle of Schistosoma japonicum (12)

Answer 30

1. Eggs in faeces of reservoir - water buffalo, cattle, rodents, dogs, sheep, pigs. 2. Ovum 3. Hatch out to miracidium stage 4. Oncomelania snail (water snail) = intermediate host 5. Shedding -\> cercariae 6. Cercariae penetrate skin - directly head-end allows digestion of skin and for them to pass through 7. Become schistosomula 8. Migration: veins -\> heart -\> lungs -\> heart -\> arteries -\> liver -\> hepatic portal vessels 9. Pairing of mature worms 10. Mesenteric vessels of bowel - egg produciton 11. Egg laying 12. Eggs retained in tissue cause disease

Question 31

Infection reservoirs of Schistosoma japonicum. (5)

Answer 31

Water buffalo, cattle, rodents, dogs, sheep, pigs

Question 32

Pathogenesis of Schistosoma spp. (6)

Answer 32

Question 33

Schistosoma granulomas (3)

Answer 33

Question 34

Where is schistosomiasis more serious?

Answer 34

In smaller ruminants

Question 35

Acute schistosomiasis (3) (sheep)

Answer 35

Question 36

Chronic schistosomiasis (sheep) (2)

Answer 36

Question 37

Points of control of schistosomiasis - intervening (7)

Answer 37

Question 38

Schistosoma blood flukes are important infections of...

Answer 38

Ruminants in Africa, Asia and South Europe