April is Pet First Aid Awareness Month:
Heartworms in Dogs
ANSWER Heartworm disease is one of the major health problems of
dogs in the United States and throughout the temperate and tropical areas of
the world. As well as being found in dogs and other species, it is now being
found in cats in ever increasing numbers. The disease develops when a pet
becomes infected with parasites called Dirofilaria immitis that are transmitted through the bite of an infected
mosquito. Heartworms are “foot long” worms that live in the heart and major blood
vessels of the lungs. Heartworm disease is spread by mosquitoes to dogs and
cats as well as other animals, such as foxes, coyotes, and wolves, which act as
reservoirs and help spread the disease. While dogs can be infected with just a
few to hundreds of worms, cats generally have low worm counts. Even one or two
heartworms, however, can be life threatening to a cat. While there is a
treatment for infected dogs it is time consuming and costly. There is NO
treatment approved for cats so prevention is critical. Heartworm infection
often leads to severe lung disease and heart failure and can damage other
organs in the body as well.
ANSWER Heartworm infection primarily affects dogs, but infection
also occurs in cats. In fact, diagnosis in cats is on the rise. Ferrets, as
well as other mammals, such as wolves, coyotes, foxes, and even sea lions, can
be infected with heartworms. Outdoor pets are at greatest risk for infection,
especially in regions of the world with high mosquito populations. However,
even indoor pets become infected by heartworms as infected mosquitoes can, and
do, get into houses. In addition, the disease has been found in all 50 states.
ANSWER Many factors must be considered even if heartworms do not
seem to be a problem in your local area. You may travel with your pet to an
area where heartworms are more common and not even know it. Heartworm disease
is spreading to new regions of the country each year. Stray and neglected dogs
and certain wildlife such as coyotes, wolves, and foxes can be carriers of
heartworms. Mosquitoes blown great distances by the wind and the relocation of
infected pets to previously uninfected areas all contribute to the spread of
heartworm disease. This happened following Hurricane Katrina when 250,000 pets,
many of them infected with heartworms, were “adopted” and shipped throughout
the country! The safest thing to do, and the best insurance against infection,
is to administer a year-round heartworm preventive as directed by your
veterinarian.
ANSWER Adult female heartworms living in
an infected dog, fox, coyote, or wolf produce microscopic baby worms called microfilaria
that circulate in the bloodstream. When a mosquito bites and takes a blood meal
from an infected animal it picks up these baby worms, which develop and mature
into “infective stage” larvae over a period of 10 to 14 days. Then, when the infected
mosquito bites another dog, cat, or susceptible wild animal the infective
larvae exit the mosquito's mouth parts and are deposited onto the surface of
the animal's skin. The infective larvae can then actively enter the new host through
the mosquito’s bite wound. Once inside a new host, it takes approximately 6
months for the larvae to mature into adult “foot long” heartworms. Once mature,
heartworms may live for 5 to 7 years, and because of their longevity,
each mosquito season can lead to an increasing number of worms in our pets.
