A dog heartworm infection is a complex process that begins when mosquitoes bite an heartworm infected animal. When these mosquitoes feed on the infected animal, they become infected with a tiny creature called microfilariae with their blood meal. These microfilariae migrate from the mosquito’s digestive tract to its abdominal region, where they undergo a transformation and reach the infective stage. At this point, the larvae are actually miniature adult heartworms, yet small enough to live inside the mosquito.
Heartworm Microfilariae
Next, the microfilariae break into the mosquito’s body cavity and migrate to its mouthparts. Then, when the mosquito bites your dog, the larvae (microfilariae) are deposited on the dog’s skin.
These microfilariae infect a dog by burrow into the dog and then migrate to the muscles of its chest and abdomen. Forty-five to 60 days after the initial infection, they molt to a fifth state. Between 75 and 120 days after infection, the immature heartworms enter the bloodstream and are carried through the heart to reside in the dog’s pulmonary artery. They greatly increase in size over the next three to four months. Female adult heartworms are about 30 centimeters long and males about 23 centimeters with a coiled tail often called a “pigtail.” Then, about six and a half to seven months after infection, the adult worms mate and the females being giving birth to live young called microfilariae and the circle begins again.
The period between when the dog receives its initial infection when bitten by the mosquito and the maturation of the worms into adults living in the heart takes six to seven months and is known as the “prepatent period”.
During the six-month long prepatent period, most dogs show no symptoms of the heartworm infection. For that matter, many dogs show little or no signs of infection even after the heartworms become mature – especially if they live a fairly sedentary lifestyle.
The Classic Symptoms Of Dog Heartworm
Dogs that lead an active lifestyle or are heavily infected may show the classic signs of heartworm disease. The early signs of a heartworm infection include coughing – especially when the dog is exercising – and early exhaustion. If your dog has a more advanced case of heartworm infection, it may also show severe weight loss, fainting, coughing up blood and, finally, congestive heart failure.
Dog heartworm treatment
If you believe your dog may be infected with heartworms, the first step is to get it to a veterinarian for a blood test, as this is the only way the disease can be diagnosed. If the test does indicate a heartworm infection, the vet will most likely evaluate your dog for secondary problems such as heart failure or liver or kidney problems. The reason for this is to make sure your dog can withstand the heartworm treatment.
If he or she finds such problems, they will be fixed before treating the dog for heartworms.
While a number of different medications have been used to treat heartworm infections in the past, the common treatment today is to inject an arsenic-containing drug deep into the muscles of the dog’s lower back. This is usually done as two doses each day for two days. The dog is then given rest time so its system can absorb the dead worms.
The dog may then be given more treatments to kill the microfilariae – daily doses for a week. Next, it will be given a blood test to see if microfilariae are still present in the dog. In this case, the dog will be given more treatments at higher dosage.
Preventing dog heartworms
Your dog should be given regular checkups and blood tests to spot any microfilariae before it can mature into adult heartworms, as this is the best way to prevent the disease. In addition, if you live in a warm weather area where heartworms are more prevalent, your vet may recommend a year-around program of heartworm prevention. For example, there is now a heartworm preventative drug available in tablet form that you can give your dog each month.
In any event, regular blood tests are the best way to spot potential bloodworm problems in your dog before they can become life threatening.
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