Heartworm gray seals, sea lions, and raccoons. In companion

 

            Heartworm disease is a serious and sometimes fatal
condition that affects a variety of mammalian species, though is found predominantly
in canines, and is caused by the organism known as Dirofilaria immitis (Atkins, 2018).  Heartworm is spread by female mosquitoes as
the intermediate host, who carry the microfilaria (the immature worm larvae) in
the residue on her mouthpiece from an infected animal to a new host (AKC, 2015).  Heartworm disease can lead to the damage of a
multitude of vital organs, including the heart, lungs, liver, and kidneys (FDA, 2017).  “Heartworm infection is generally completely
preventable with macrolide prophylaxis” (Atkins, 2018). Treatment is based on
the presence of adult worms, the stage of disease, the state the animal is in, the
species, and can be both expensive and dangerous (FDA, 2017).

Heartworms
have been known to infect many different species, including “wolves, coyotes,
foxes, California gray seals, sea lions, and raccoons. In companion animals, HW
infection is diagnosed primarily in dogs and less commonly in cats and ferrets”
(Atkins, 2018). There have also been some reported
instances of humans becoming infected, though cases are few and far between and
humans appear to be dead end hosts, with infective larvae progressing to the
lungs and becoming encapsulated and dying, where they then “precipitate
granulomatous reactions called “coin lesions” (Atkins, 2018).

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Mosquitoes
are more than just pesky insects, being the intermediate hosts of a variety of
diseases, particularly heartworm disease. The microfilariae of the organism
Dirofilaria immitis is ingested by a mosquito when it consumes a blood meal
from an infected animal, where the larvae develop in the mosquito for 2-2.5
weeks, which then emerge from the mouthparts of the mosquito as she feeds on
another animal and ejects the larvae into its skin (Summers, 2014). Within the new host, the infective
larvae migrate through the skin and towards the heart and cardiovascular
system, maturing as they go, eventually settling amongst the pulmonary blood
vessels, veins, arteries, and/or the right side of the heart(AVMA, 2018) (Atkins, 2018). It takes 6 to 7
months in a host for the worm to become a fully mature heartworm, at up to 14
inches in length (Summers, 2014). Adult heartworms are white roundworms and
are likened to “cooked spaghetti,” and an infected dog may have anywhere from 1
to 250 worms (FDA, 2017).

            Clinical signs: Clinical signs vary in respect to the
severity of the case. Heartworm disease is