Heartworm disease in dogs is an infection that is brought about by an organism (Dirofilaria immitis). Though preventable, the disease can easily become fatal if not treated. The parasite is spread by mosquitoes, which transmit the larvae of the heartworm (microfilariae) from a diseased animal to a healthy animal. As soon as the larvae get into the new host, they quickly develop into mature worms, and within a couple of months they reside within the blood vessels of the heart and lungs. These mature heartworms can even enter the heart in cases where there is an advanced infection. The result is rapid swelling of the lungs and blood vessels primarily due to the stress placed on the dog’s heart by the parasites. The condition becomes more complicated and aggravated when the number of parasites in the heart reaches excessive proportions, or when the organisms die. It is also possible for one animal to be constantly re-infected, creating a situation where the heartworm exists in different phases of its life i.e. presence of mature and un-developed heartworms.
The heartworm parasite can be spread by almost 70 species of mosquitoes. Countries that have tropical, semitropical and temperate climates all over the globe have reported cases of this disease. These include Canada, southern Europe and USA. Although all dogs, regardless of whether they are kept inside or outside the home, are susceptible to heartworm infection, it is those which are kept outdoors that are at greatest risk of mosquito bites.
There are a number of factors to consider when assessing the signs of how severe an infection is. It all depends on how active is the animal, the infected dog’s immune reaction, the length of time it has been infected, and the number of worms it is carrying. Majority of dogs tend to be vulnerable to infection by heartworms, with most of the larvae maturing into adults. The affected animal’s blood vessels and heart will become inflamed and irritated, as long as there are heartworms within the heart and lung vessels. Heartworms have a life span of more than five years. Therefore, if an animal is infected for over a year, it will suffer decreased flexibility and scarring of the blood vessels due to the continual inflammation.
Smaller dog breeds usually don’t handle such infections or the corresponding treatment very well, compared to larger breeds. The reason is that they naturally have smaller heart chambers and blood vessels, thus cannot withstand the great number of worms that will cause clogged and damaged vessels
Symptoms Of Heartworm Disease in Dogs
The corresponding symptoms of heartworm infection include build-up of fluid in the stomach, coughing, bleeding from the nose, unwillingness to exercise, loss of consciousness, lack of growth, breathing problems, spitting blood, and a bluish-purple skin discoloration. How active or inactive a dog is will usually be indicative of the severity of the infection. The fact is, overly active dogs will display more severe symptoms of infection than inactive dogs, even though the sedentary ones may be carrying a higher number of worms
Out of all the available testing techniques, the antigen detection test is the most popular diagnostic method with regards to suspected heartworm infection. It is very sensitive to any present infections of heartworms in dogs. There are also other methods for diagnosis, like blood tests, echocardiography, and x-rays of the chest. The veterinarian usually settles on a particular method depending on the dog’s medical past and its overall health.
Management of Heartworms
A qualified veterinarian will always ask you to provide your dog’s complete medical history, before prescribing any kind of heartworm treatment. This process is important as the most suitable treatment will always depend on factors like the possibility of the dog having another kind of disease that could affect the treatment regimen.
Treatment of adult heartworm infection is only possible through the use of one specific medication, and that is melarsomine dihydrochloride, which is a compound of arsenic. This drug, if used appropriately, will destroy underdeveloped as well as adult heartworms. Two recommended treatment procedures exist; a 2-dose and a 3-dose protocol. The two protocols both involve injecting the medication deep into the muscles of the dog’s back, ensuring to use a different side with alternate treatments. Almost 33% of all dogs will develop swelling, irritation, and a sterile blister where they were injected. A 2‑dose protocol involves two doses administered 24 hours from each other. A 3-dose protocol consists of a single dose given, with the next dose administered a month later. The third dose is then given 24 hours after the second one. Majority of veterinarians opt for the 3-dose protocol due to its relative safety and efficiency in eliminating all the worms, irrespective of whatever stage the disease is at.
It should be mentioned that the treatment might cause some kind of breathing problem due to the dead heartworms, more so if the dog is not locked up to limit its movement. Such respiratory problems can crop up a few days to even six weeks after treating an infected dog. The symptoms to watch out for after treatment are fever, coughing, laziness, spitting up blood, loss of appetite, and breathing problems. There are some dogs that develop difficulties after the treatment. Such cases call for confinement within a cage, inflammation drugs and oxygen treatment, in order to relieve the problems. The confinement should be for at least one month after the last melarsomine injection. The dogs should also be tested after six months to ensure that all heartworms are dead. In case of any re-infection, the test should be repeated, and any positive results should automatically lead to another round of treatment. With adequate care, dogs start to get better from the complications within a day or so.
Prevention Of Heartworm Disease in Dogs
It is possible to keep heartworm infection at bay. Your veterinarian has access to some drugs that can safely and effectively prevent your dog from getting infected. This kind of treatment can begin when the dog is six to eight weeks old, without any prior tests. For more mature dogs, preventive treatment involves an antigen test, which determines whether there is existing infection. Consequently, another test is done six months later just to ascertain that there is no infection. This effort at prevention is a year-round treatment, although the best thing to do is to consult your veterinarian about the most appropriate plan for your dog.
There is simply no substitute when it comes to pet owners ensuring that their dogs receive the recommended dose at the right time. It is the best way to combat the heartworm infection. There are cases where the dog owner forgets to give the preventive drugs to their dogs, as this is supposed to be a monthly dosage. The simple solution might be to write down and stick the medication dates on a refrigerator door, then check off the dates every time a dose is administered. Some companies that manufacture these drugs even send free reminders via e-mail.
It is imperative that no dose is skipped or missed, as the consequences could be severe. In the event that you forget to administer a dose, you should call you veterinarian immediately so that they may advise you on how to proceed.