HEARTWORM ALERT (10.14.09)
Disease Overview. Heartworm disease is caused by a
mosquito-borne parasite called Dirofilaria immitis. This
parasite infects dogs, ferrets, wolves, coyotes, seals,
sea lions and, occasionally, cats. Heartworms live
inside in the large blood vessels leading from the heart
to the lungs. Animals may become infected when bitten by
mosquitoes that are carrying the parasite. Mosquitoes
pick up the parasite when they bite an animal that has
an active infection. Infection can be present for awhile
before symptoms appear. Symptoms may include tiredness,
problems breathing, coughing, and heart failure.
Infected dogs and coyotes are a reservoir for the
disease.
Local Data, 2005-2009
Since 2005, forty-six cases of heartworm infection have
been reported in Los Angeles County pets, with two cases
in cats and forty-four in dogs. Seventeen infections
(37%) were considered locally-acquired because these
pets had no recent travel outside of Southern
California. Twenty-one cases (46%) were considered
imported, with the animal likely being infected outside
of Southern California. In eight cases (17%) the pet was
a stray and the location where the infection was
contracted was unknown. The majority of the cases (65%)
had no symptoms on presentation. In the other cases,
symptoms included cough (24%), fatigue (20%), and heart
failure (9%).
Trends in 2009
So far in 2009, sixteen reports of heartworm disease
have been received, with ten suspected of being locally
acquired. This makes 2009 the year with the most
reported local cases. A geographic cluster of six
infected dogs was found in the western part of the San
Gabriel Valley. This was especially suggestive of local
disease transmission (see map next page). Therefore
Dirofilaria immitis likely exists in mosquitoes in
that area.
Untreated animals
Of special concern is that in 7 out of 16 cases in dogs
this year, the owner declined treatment. Untreated
animals may act as reservoirs for the disease, infecting
more mosquitoes. A 2004 study found that 5-20% of
Southern California coyotes are infected with
heartworms1 Coyotes can also act as a reservoir for the
disease.
Human Health Risk
Human infections with Dirofilaria immitis are rare, and
most commonly have involved for the formation of nodules
in the lungs or under the skin.
Recommendations
Mosquito Control. Help reduce mosquito breeding
by dumping any standing water on your property every 48
hours. Mosquitoes feed the most at dawn, dusk and at
night, so it is best to keep your pet indoors at night.
Consider Heartworm Preventative Medication.
Heartworm preventative medications are generally
regarded as safe and some help prevent infection with
additional parasites. Discuss the issue with your pet’s
veterinarian.
For a PRINTABLE
VERSION of this report click
here
(pdf).
Report a case of heartworm disease by using
this pdf form or by using the
online reporting portal.
More Information
American
Heartworm Society (find "Pet Owner Resources"
section at bottom of main page)
Scientific
Articles - Heartworm in California Coyotes
2004 - Modeling the Distribution and Abundance of the
Non-native Parasite, Canine Heartworm, in California
Coyotes.(abstract)
2003 - Reconstructing the Spread of Dirofilaria immitis
in California Coyotes (fullt text, pdf)
1998 - Increasing prevalence of canine heartworm in
coyotes from California (full text, pdf)
Scientific Articles -
Heartworm Infection in Humans
2005 - Public Health Aspects of Dirofilariasis in the
United States (abstract)
2002 - Human Pulmonary Dirofilariasis:
Uncommon Cause of Pulmonary Coin-lesion
(abstract)
2001 - Heartworm in a 28 Year-old-man in California
(full text, pdf)
