Heartworm Disease

Question 1

What species are the definitive hosts for dirofilaria immitis?

Answer 1

Canids (wolves, foxes, coyotes)
They are also the main reservoir for infection

Other species that can become infected: domestic cats, ferrets, muskrats, sea lions, humans, etc

Question 2

What is the vector for transmission of heart worm and how does this vector transmit the disease?

Answer 2

Mosquito

Becomes infected by blood meal from microfilaremic host
Within mosquito, microfilaria becomes L!, then molts into L2, then L3

L3 = infective stage, which migrates to the head and mouthparts of the mosquito
Time required for development of microfilaria to infective stage is temperature dependent (10-14 days or longer)

Infective L3 enters host body via blood meal —> molts into L4 in 3-12 days, then travels between sQ tissue and muscle fibers

The final molt into juvenile/immature adults (Between 50-70 days) occurs while they migrate through the body, enter the circulatory system, and then are transported to heart and lungs

Sexual maturity occurs about 120 days post infection with dogs developing circulating microfilaria as early as 6 months but usually by 7-9 months post infection

Question 3

What is wolbachia?

Answer 3

Obligate intracellular gram negative bacteria harbored by HW

Wolbachia surface proteins have been identified in the glomerulus and lung of HW infected dogs