919 Percy Brown Road Thibodaux, LA 70301 (985) 446-8824 ridgefieldanimal@comcast.net

Heartworm Disease

Heartworms are a significant parasite of the gulf coast area, and indeed have become endemic in most areas of the U.S. However, here in Louisiana, heartworms cause more deaths in younger pets due to the fact that the mosquito is the vector and a host for the parasite, and the mosquito is present year-round in our area. We also have large populations of stray and wild dogs (coyotes) to complete the life cycle.

Heartworms can be prevented in dogs, cats, and ferrets by using a medication administered monthly or by injection to kill a certain stage of the parasite. It is important to maintain your pet on monthly heartworm prevention, with no gaps in protection, for the rest of its life. Annual heartworm testing is recommended to ensure a negative status and to help maintain the highest health standards of your pet.

1) What pets are affected?

Dogs are the primary host, and in our area, we see close to 100% of the outdoor dogs who are not on any preventive medication being positive for infection. Cats and ferrets are also at risk for the disease and should be on preventive medications as well.

2) How are heartworms spread?

Heartworms are spread by mosquitoes, which is a year-round problem in our area. Up to 7 larvae (immature heartworms) can be transmitted with each bite.

3) How do these worms cause disease in my pet?

Each of these larvae can mature into a worm in the blood vessels of the lungs and in the heart. These worms block the flow of blood once their numbers increase, causing right-sided heart failure. Dying worms and larvae release substances that can also cause severe allergic reactions in some animals, especially cats.

4) What are signs my pet has heartworms?

The signs most often cited in cases of canine heartworms are weight loss with a cough, and exercise intolerance. Cats often present differently with heartworms. In the cat, we can see asthma-like signs that can be permanent from even a transient infection with larva. If a cat does develop an adult heartworm infection, it is many times only one or two worms. However, when these worms die, the only sign the owner may see is sudden death due to severe allergic reaction.

5) Can I have my pet treated for heartworms?

Yes and no. Dogs can be treated with a drug that can kill adult heartworms if they are diagnosed early enough to survive the die-off of the heartworms in the heart and lungs. A heartworm test at the annual exam helps ensure that we diagnose any accidental cases as early as possible so the treatment can have an increased success rate and fewer complications. Pets who are very ill have a poorer prognosis for a straightforward treatment and cure. Unfortunately, there is no effective treatment for cats or ferrets at this time, so our treatment of these pets is to prevent reactions to the presence of the worms.

6) How can I prevent heartworm infection in my pet?

Heartworms can be prevented in dogs, cats, and ferrets by using a medication administered monthly or by injection to kill a certain stage of the parasite. These medications are very safe and over 99% effective. Three general categories are available, and all products prevent some intestinal parasites as well. Oral monthly medications are available as chewable or regular tablets (Heartgard Plus, Interceptor and others), and there are also liquid products that are applied to the skin (Advantage Multi, Imoxi and Revolution Plus). The third category is an injectable given twice a year (Proheart 6) or once a year (Proheart 12). Products are also available that include flea prevention (Advantage Multi, Imoxi, Revolution Plus, and Simparica Trio). Speak with your veterinarian to determine which product would be best for your pet and your lifestyle.

Great Tip:

Set the first of the month as a recurring appointment in your phone so you get a reminder alert at the first of every month to administer your pet's prevention!

7) How are dogs treated for heartworms?

There is some risk involved in treating dogs with heartworms, although fatalities are rare. In the past, the drug used to treat heartworms contained arsenic, so toxic effects and reactions occurred more frequently. A newer drug is now available that does not have the toxic side-effects, allowing successful treatment of more than 95% of dogs with heartworms. This injection kills the adult heartworms in the heart and adjacent vessels. Some dogs are diagnosed with advanced heartworm disease. This means that the heartworms have been present long enough to cause substantial damage to the heart, lungs, blood vessels, kidneys, and liver. A few of these cases will be so advanced that it will be safer to treat the organ damage rather than risk treatment to kill the heartworms. Dogs in this condition are not likely to live more than a few weeks or months. For complete details of the treatment, see the treatment outline below.

8) Is complete rest essential after treatment?

YES! The adult worms begin to die in a few days and start to decompose, thus making the first week critical for complete rest. As they break up, they are carried to the lungs, where they lodge in the small blood vessels and are eventually reabsorbed by the body. This can be a dangerous period, so it is absolutely essential that the dog be kept quiet and not be allowed to exercise for one month following treatment. A cough can be noticeable for seven to eight weeks after treatment in many heavily infected dogs. Prompt treatment is essential if the dog has a significant reaction in the weeks following the initial treatment, although such reactions are rare. If a dog shows loss of appetite, shortness of breath, severe coughing, coughing up blood, fever, and/or depression, you should notify us immediately. Response to antibiotics, cage rest, and supportive care and intravenous fluids is usually good in these cases.

9) What types of Heartworm prevention does Ridgefield Animal Hospital carry?

Simparica Trio, Imoxi , Proheart 6 and Proheart 12.

10) What is the best way to avoid the expense and stress of having a pet with heartworm disease?

Prevent it! Dogs on prevention have a positive rate in our hospital of less than 1%. That is equivalent to the success rate of the birth control pill. However, we do see failures. The alternative, not being on prevention, puts your pet at high risk of infection. A dog on heartworm prevention that is given properly and on time (with a purchase history in our records that matches this) will have most, if not all of their treatment subsidized by all of the major manufacturers. Problems with these limited guarantees arise when people use products obtained from friends (left over from a deceased pet), or some internet sources, or changing products without follow-up heartworm testing. Also, gaps in prevention are common, and the purchase history will show this as, say, a 6 months’ supply being sold, with the next one bought 9 months later = 3 months of the pet not being protected. Protect your pet and yourself by giving only heartworm prevention purchased through your regular veterinarian and giving it on time and by the correct weight of the pet.

Heartworm Treatment Outline

The following outlines the process of treating heartworms.

1. Diagnosis and Pre-treatment work-up:
   a) A repeat SNAP heartworm occult will be performed to confirm your pet's heartworm positive status (if not previously performed)
   b) Bloodwork is done to be sure there are no medical conditions that we should be aware ofand to assess the severity of heartworm disease.
   c) X-rays of the chest are done to show if your pet is at risk for certain complications related to dying heartworms and to assess the severity of your pet's heartworm disease.
   d) Your pet is started on a heartworm preventative that kills the microfilaria (heartworm larvae) over several months. Your pet is also started on Doxycycline, an antibiotic that aids in the treatment of heartworms.
   e) Re-check in 30 to 60 days. It is important to maintain your pet on monthly heartworm prevention. (Including during heartworm treatment) because a positive heartworm status does not prevent your pet from contracting more heartworms.

2. Initial Heartworm injection (1-2 months after the work-up)
   a) Your pet will receive an injection of Immiticide in the left lumbar (back) muscle and your pet is monitored throughout the day.
   b) Pain medication and steroids will be prescribed.
   c) You will need to monitor your pet and notify us if any coughing or lack of appetite occurs.
   d) Keep your pet strictly confined in a cool, quiet area until Second and Third injection. Sedatives can be prescribed to help keep them calm if needed.

3.) Second and Third injection series (1 month later)
   a) Your pet will be given 2 injections of Immiticide 24 hours apart in the left and right lumbar muscles. These areas may be sore for a few days.
   b) Steroids and pain medication will be prescribed.
   c) Monitor your pet for any signs of coughing or lack of appetite.
​   d) Keep your pet strictly confined in a cool, quiet area for another 4 weeks. Sedatives can be prescribed to help keep them calm if needed. Your pet can slowly return to regular activity after the 4-weeks of rest.

4) Final Heartworm check (nine months later)
   a) A blood sample will be drawn, and an occult heartworm test ran to confirm that the treatment has resulted in the complete removal of your pet's heartworms.
   b) Maintain your pet on heartworm preventative for the rest of their life.
   c) Annual heartworm testing is recommended to ensure a negative status and to help maintain the highest health standards of your pet.

5) Your veterinarian will discuss if a change in his/her heartworm preventative is deemed to be in your pet's best interest. Ease of medicating, cost and your pet's lifestyle will be taken into consideration.

It is important to note that when proper heartworm prevention is purchased from a veterinarian and given on a regular monthly schedule, all the major brands are covered under a limited product guarantee by the companies that produce them.

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After-Hours Emergencies

Our established clients, those who have been to Ridgefield within the last two years and are in good financial standing with Ridgefield Animal Hospital, should call our main telephone number (985) 446-8824.

***Non-Ridgefield Animal Hospital clients will be referred to an emergency hospital: ***

MedVet New Orleans
2315 N. Causeway Blvd.
Metairie, LA 70001

LSU School of Veterinary Medicine
Skip Bertman Dr.
Baton Rouge, LA 70803