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Heartworms: Dogs & Cats
Picture courtesy of www.placevillevets.com
Adult heartworms, about six inches long, live in the heart and large blood vessels. The adult male and female worms produce thousands of microscopic baby worms. These baby heartworms do not grow up in the dog where they were born. (If they did, the dog would immediately die and that would be the end of the heartworms.) Before baby worms can develop further, they must be inside a mosquito.
Next, a mosquito comes along and bites the infected dog, sucking up baby heartworms. This probably isn't too good for the mosquito, but it is what the worms have been waiting for. During the next month, the heartworm babies grow into heartworm teenagers, a stage partway between baby and adult.
Now, the mosquito bites another dog, infecting the new dog with teenage heartworms, ready to develop into adults. After six or seven more months, the life cycle is complete: new adult male and female heartworms are busily producing thousands of baby heartworms.
Canine heartworm disease
Symptoms
There are no symptoms at all until the disease is very advanced. Then, the symptoms are those of congestive heart failure: dull coat, lack of energy, coughing, difficulty breathing, perhaps fainting spells and an enlarged abdomen. Waiting for symptoms to develop and then treating is not a realistic alternative to prevention.
Prevention
There are three different drugs used for once-a-month heartworm prevention, plus a new one that is applied to the skin and also kills fleas. In cold climates, prevention medication is not necessary in the wintertime. Prevention recommendation is once a month, year 'round, permanently.
Heartworm treatment
Although heartworms can be fatal and treatment for the disease involves risk, the condition is nearly always curable. Treatment requires careful medical care and complete rest at home afterwards.
Adult heartworms are about six inches long and live mostly inside the heart. Baby heartworms are microscopic and live within blood vessels throughout the body. Each stage must be treated separately.
When the treatment is finished, your dog's heartworms will be dead or dying. That's good, but the heart is still full of worms. The worms gradually break into smaller and smaller pieces until the fragments are tiny enough for the body to eliminate them. The critical period is when worm fragments are small enough to disperse into the body but still large enough to plug small arteries in the lungs. Vigorous activity makes the heart pump faster, pushing bits of dead heartworm out into small blood vessels where they can cause trouble, so vigorous activity must be avoided.
This information was provided by: http://www.placervillevet.com
Feline Heartworm Disease
Cats have historically been considered susceptible, but somewhat resistant hosts to heartworms. In experimental infections of D. immitis in cats, the percentage of infective larvae developing to adult D. immitis is low (0% to 25%) compared to dogs (40% to 90%). However, the percentage of experimentally-infected cats from which adult worms are recovered is generally high (61% to 90%), but still different from dogs, where adult worms are recovered in virtually 100% of infected dogs. The worm burden in cats is usually low, as most have fewer than 10 worms, although there have been documented cases of worm burdens as high as 45 and 65 in two different male cats. Although heartworms reach a substantial size in cats, they are somewhat smaller than those of similar age in dogs. The life span of the worms in cats appears to be about 2 to 3 years, compared to 5 to 7 years in dogs.
The average prepatent period (the time elapsed from when the larvae enter the host until the adult female worms begin to produce microfilariae) in cats is about 8 months, which is 1 to 2 months longer than that seen in dogs. Microfilaremia is uncommon in cats (usually less than 20% of cases), and when present, it is inconsistent and transient in nature. As such, cats are poor reservoirs of infection, as heartworms are less likely to mature to adults in cats than in dogs and are short-lived when present. There is no age predilection to D. immitis infection in cats, and cases have been reported in cats from 9 months to 17 years of age, with a median age at diagnosis or death of approximately 4 years of age.
Some cats appear to be able to rid themselves of the infection spontaneously. It is assumed that the cat develops a strong immune response to the worms which causes their death, or perhaps the parasite dies as a result of physiologic maladaptation and the intense immune response occurs only after worm death. Single sex heartworm infections are also more common in cats.
This information was provided by: http://www.heartwormsociety.org
