What You Should Know About Heartworms in Dogs & Cats.

What Are Heartworms?

Heartworms are parasitic worms. When mosquitos feed off the blood of an animal already infected by heartworms, they become the host of young heartworms called microfilariae. In about two weeks, the microfilariae develop into infective larvae. These larvae are then transmitted into whatever animal serves as that mosquito’s next blood meal. After six months or so, the infective larvae develop into adult heartworms.  

Mature heartworms can cause severe lung disease and heart failure while damaging other organs in the infected animal. Heartworms in dogs can also multiply by the hundreds if left untreated. Preventatives do not stop your pet from getting infected. What the medication does is eliminate microfilariae before they become adults and damage your pet’s heart, lungs and blood vessels. 

The Difference Between a Heartworm Infection & Heartworm Disease

Your pet has a heartworm infection when immature larvae are in your dog or cat’s body. At this stage, you would normally not see any signs of illness. An animal has heartworm disease when it shows clinical signs caused by an adult heartworm infection. 

The silver lining (if any) is that heartworms are not contagious. They can only be passed from one animal to another by mosquitoes. Nevertheless, it’s important to get your dog or cat regularly tested for heartworms by a veterinarian or at one of the community clinics at Pet Supplies Plus. You can also get your prescription for a preventative filled by our online pharmacy. 

Heartworm Symptoms in Dogs

Signs of heartworm disease can include decreased appetite, weight loss, swollen belly (caused by excess fluid in their abdomen), constant exhaustion and a persistent cough. If your dog is having difficulty breathing, has pale gums and dark bloody or coffee-colored urine, they may have caval syndrome. This is a life-threatening condition caused by heartworms blocking the flow of blood into your pet’s heart.  

Heartworm Symptoms in Cats

Some of the clinical signs include coughing, difficulty walking, fainting or seizures, recurrent vomiting, lack of appetite, weight loss, lethargy or a bloated belly (due to fluid accumulation in their abdomen).  

Compared to dogs, cats are fairly resistant to heartworm infections. In fact, heartworm disease in cats is rare because only a few infective larvae (usually less than 4) ever make it to the adult stage. That doesn’t necessarily mean cats are in the clear. When an immature worm dies in a cat’s blood vessels, it can cause an illness called Heartworm Associated Respiratory Disease (HARD).  

Heartworm Testing

The goal of a heartworm test is to detect the presence of heartworm proteins in your pet’s blood. Once a dog is infected, they may not test positive for at least 6 months because the heartworms are still in their larval stage. An infection is even harder to detect in cats and often requires a battery of clinical and diagnostic tests. For these reasons, it’s important to get your pet tested early and often and put them on some sort of preventative as soon as possible.  

After their first test, your dog or cat needs to be tested again 6 months later. From then on, they’ll need a heartworm test every 12 months to ensure their medication is working. If your pet is given preventatives before they’re 6 to 8 months old, a test is not needed before taking their first dose. On the other hand, any dog or cat older than 8 months old should get a heartworm test prior to starting a preventative. Even at a young age, they could already be infected. If they are, they’ll need to be treated first before going on any sort of prevention medication.   

Once your pet starts taking monthly preventatives, it’s important they don’t miss a dose or take it late. If they go off schedule, you should get your dog or cat re-tested 6 months from when you restart their heartworm medication.  

Conclusion

Heartworm Awareness Month is a good reminder that you need to be diligent about protecting your dog or cat from heartworm disease. By the time you see symptoms caused by a heartworm infection, the adult worms are now in your pet’s heart, lungs and blood vessels—and your dog or cat has heartworm disease. That’s why animals must be tested every 12 months after their first 2 heartworm tests. They also need to be put on a monthly preventative. The medication helps prevent the larvae from becoming adult heartworms all year round.

If you have any further questions or concerns about heartworm disease, please talk with your veterinarian.