HEARTWORMS;
How Heartworm is Transmitted to
Dogs and
Cats
Heartworm (Dirofilaria immitis) is a parasite that can infect
both dogs and cats. Transmitted by mosquitoes, D. immitis can be found
in most areas of the country where mosquitoes breed. Infected dogs can carry the
parasite to areas where it normally is
uncommon.
Adult heartworms reside in the
heart's right ventricle and pulmonary arteries, and can grow to a length of
5-to-12 inches in dogs and 5-to-8 inches in cats. When adult heartworms living
in animals mate and produce offspring or microscopic heartworm larvae
(microfilariae), the offspring can live in an animal's bloodstream for three
years.
Heartworm disease is caused by adult
heartworms and fragments of dead worms obstructing the normal blood flow through
the heart and can lead to congestive heart failure and obstruction of the
pulmonary blood vessels which carry blood to the
lungs.
Mosquitoes transmit heartworm. When a
mosquito bites an infected animal, the heartworm microfilariae are ingested
along with the blood. In the mosquito, these microscopic pests develop into
infective larvae, which are transmitted back to an animal through another
mosquito bite. During the microfilariae maturation process in the animal (which
lasts about six-to-seven months in dogs), the heartworms travel to the lungs and
the right side of the heart, where they can grow and mate for several
years.
Treating all animals in a household is
essential. Both dogs and cats often show no signs in the early stages of
heartworm disease. Treating dogs for heartworm disease can be lengthy, expensive
and life threatening. Currently, there is no approved treatment for heartworm
disease in cats. For these reasons, prevention is the key. While fewer cats than
dogs contract heartworm disease, those that do are prone to blockage of an
artery and subsequent death. Whereas normally 10 or more adult heartworms need
to be present before dogs exhibit severe heartworm disease, just one adult
heartworm can be fatal to
cats.
Signs in Dogs
Heartworm signs
can take years to appear in infected animals. Early canine signs often are
easily attributed to other conditions or diseases. Those signs can include
fatigue, non-productive cough, difficulty breathing, exercise intolerance,
coughing up blood, weight loss and fluid accumulation in the abdominal cavity.
Untreated heartworm disease can result in death. Testing for heartworm most
often involves a blood test that indicates whether microfilariae are present in
blood. In recent years, more veterinarians have begun to use antigen testing to
detect and confirm whether adult heartworms are present in the
heart.
Signs in Cats
In cats,
heartworm signs can include chronic vomiting, coughing, difficulty breathing,
collapse, weight loss, lethargy, rapid heart rate, diarrhea, convulsions,
asthma-like signs or sudden death. Because heartworm blood tests in cats rarely
uncover microfilariae, veterinarians must rely on other methods such as testing
for certain antibodies in the cat's
blood.
Treatment and Treatment
Outcomes
Treating dogs for heartworm
disease is a multi-step process that is both costly and very risky for the
animal. Successfully treating heartworm disease involves a multi-step program to
kill the adult worms and microfilariae, followed by additional ongoing treatment
to prevent future infections. While heartworm disease is less prevalent in cats
than in dogs, there currently is no approved treatment for heartworm disease in
cats. Deadly side effects to treatment in cats are common. Prevention should be
ongoing in areas where mosquitoes live and breed year-round and seasonal in
other areas depending on the length of the mosquito season. Blood tests to check
for existing heartworm infection are recommended before administering prevention
therapy. Because heartworms are sometimes difficult to detect in various stages
of their life cycle, periodic blood tests also are recommended in areas where
animals receive heartworm prevention medicine.
Human Health
Connections/Concerns
Incidents of humans
being affected by Dirofilaria immitis are rare. In humans, the disease
can cause small pulmonary lesions, which may be confused with other serious
diseases (Archives of Internal Medicine;
Sep. 22, 1997, James S. Tan, author)
Dogs and
Cats
Heartworm (Dirofilaria immitis) is a parasite that can infect
both dogs and cats. Transmitted by mosquitoes, D. immitis can be found
in most areas of the country where mosquitoes breed. Infected dogs can carry the
parasite to areas where it normally is
uncommon.
Adult heartworms reside in the
heart's right ventricle and pulmonary arteries, and can grow to a length of
5-to-12 inches in dogs and 5-to-8 inches in cats. When adult heartworms living
in animals mate and produce offspring or microscopic heartworm larvae
(microfilariae), the offspring can live in an animal's bloodstream for three
years.
Heartworm disease is caused by adult
heartworms and fragments of dead worms obstructing the normal blood flow through
the heart and can lead to congestive heart failure and obstruction of the
pulmonary blood vessels which carry blood to the
lungs.
Mosquitoes transmit heartworm. When a
mosquito bites an infected animal, the heartworm microfilariae are ingested
along with the blood. In the mosquito, these microscopic pests develop into
infective larvae, which are transmitted back to an animal through another
mosquito bite. During the microfilariae maturation process in the animal (which
lasts about six-to-seven months in dogs), the heartworms travel to the lungs and
the right side of the heart, where they can grow and mate for several
years.
Treating all animals in a household is
essential. Both dogs and cats often show no signs in the early stages of
heartworm disease. Treating dogs for heartworm disease can be lengthy, expensive
and life threatening. Currently, there is no approved treatment for heartworm
disease in cats. For these reasons, prevention is the key. While fewer cats than
dogs contract heartworm disease, those that do are prone to blockage of an
artery and subsequent death. Whereas normally 10 or more adult heartworms need
to be present before dogs exhibit severe heartworm disease, just one adult
heartworm can be fatal to
cats.
Signs in Dogs
Heartworm signs
can take years to appear in infected animals. Early canine signs often are
easily attributed to other conditions or diseases. Those signs can include
fatigue, non-productive cough, difficulty breathing, exercise intolerance,
coughing up blood, weight loss and fluid accumulation in the abdominal cavity.
Untreated heartworm disease can result in death. Testing for heartworm most
often involves a blood test that indicates whether microfilariae are present in
blood. In recent years, more veterinarians have begun to use antigen testing to
detect and confirm whether adult heartworms are present in the
heart.
Signs in Cats
In cats,
heartworm signs can include chronic vomiting, coughing, difficulty breathing,
collapse, weight loss, lethargy, rapid heart rate, diarrhea, convulsions,
asthma-like signs or sudden death. Because heartworm blood tests in cats rarely
uncover microfilariae, veterinarians must rely on other methods such as testing
for certain antibodies in the cat's
blood.
Treatment and Treatment
Outcomes
Treating dogs for heartworm
disease is a multi-step process that is both costly and very risky for the
animal. Successfully treating heartworm disease involves a multi-step program to
kill the adult worms and microfilariae, followed by additional ongoing treatment
to prevent future infections. While heartworm disease is less prevalent in cats
than in dogs, there currently is no approved treatment for heartworm disease in
cats. Deadly side effects to treatment in cats are common. Prevention should be
ongoing in areas where mosquitoes live and breed year-round and seasonal in
other areas depending on the length of the mosquito season. Blood tests to check
for existing heartworm infection are recommended before administering prevention
therapy. Because heartworms are sometimes difficult to detect in various stages
of their life cycle, periodic blood tests also are recommended in areas where
animals receive heartworm prevention medicine.
Human Health
Connections/Concerns
Incidents of humans
being affected by Dirofilaria immitis are rare. In humans, the disease
can cause small pulmonary lesions, which may be confused with other serious
diseases (Archives of Internal Medicine;
Sep. 22, 1997, James S. Tan, author)