Heartworm Disease and Infection In Pets
Wed, April 21, 2021

Heartworm Disease and Infection In Pets


Heartworm is a serious and potentially fatal parasite that infects dogs, cats, and ferrets, explained the American Veterinary Medical Association (AVMA), a not-for-profit association. Although it is preventable, it can also infect foxes, tigers, raccoons, and other animals.

Heartworms can be found in many countries across the globe. Dogs, regardless of age, sex, or living environment, are vulnerable to heartworms. Indoor and outdoor cats are also susceptible to these parasites. A human can also get infected with heartworms, but such cases are rare and do not usually cause them to fall ill

Studies Detail the Prevalence of Filarial Parasites In Dogs and Cats

Chandana H. Mallawarachchi and colleagues of biomedical and life sciences journal PMC said a total of 250 dogs and 134 cats in Sri Lanka were screened for filarial parasites. They found that the overall rates of microfilaremia were high in both dogs (68.8%) and cats (47.8%). D. (N.) repens was more common in dogs and cats (17.2% of dogs and 17.2% of cats) than B. malayi (14.4% and 13.4%). Co-infections were at 37.2% and 17.2% for dogs and cats, respectively.

Area-wise, 81.82% of dogs in Madampe, Sri Lanka were infected with microfilaraemia (versus 75% of cats). More dogs (62.39%) than cats (26%) were infected in Wattala. 64.06% of dogs and 37.50% of cats were infected in Welieriya. Overall, the prevalence of microfilaraemia was 68.80% for dogs and 47.76 for cats.

Regarding the prevalence of individual zoonotic filarial species, particularly B. malayi and D. (N.) repens, in the three study areas, Madampe had higher rates of malayi infections (68.8% of dogs and 55.8% of cats) than Wattala (49.5% and 20%) and Weliweriya (34.4% and 6.3%). D. (N.) repens infections were also higher in Madampe (63.6% of dogs and 51.9% of cats) than Wattala (46.8% and 16%) and Weliweriya (56.3% and 34.4%).

In another study about the prevalence of filarial parasites among domestic and stray cats in Selangor State, Malaysia, Nazeh M. Al-Abd and colleagues collected a total of 170 blood samples, finding that the overall prevalence of infection was 23.5%. Of these, 35% of cats with a filarial parasite infection were infected with B. pahangi. All of them were from Pulau Carey, Selangor, Malaysia, and all were domestic cats.

Published in Science Direct, a database of scientific and medical research, about 50% of the cats were infected with D. repens. D. repens was detected in eight domestic cats and two stray cats in Pulau Carey, while two domestic cats and eight stray cats were infected with it in Bukit Gasing, Selangor, Malaysia. Mixed infections of D. repens and B. pahangi was detected in 15% of cats. All of the cats were domestic and from Pulau Carey.

40% of infected cats were male and 60% were female. Domestic cats (75%) were more likely than stray cats (25%) to have higher infection rates. None of the cats were infected with B. malayi and D. immitis.



Testing Your Pet for Heartworms

Heartworms are spread by mosquitoes and if your pet is exposed to them, you should have it tested by a veterinarian. If your dog has been recently or mildly infected with heartworms, it may show no signs of illness until the worms grow into adults in the lungs. This is when the signs of heartworm diseases are detected. As the disease escalates, your dog may become lethargic, lose its appetite, cough, or tire rapidly after engaging in moderate exercises.

Your veterinarian will perform blood tests to detect the signs of adult heartworm infection. Antigen tests help detect adult female heartworms, while antibody tests determine if it has been exposed to heartworms.

Antigen tests are commonly performed in dogs too. These tests are also accurate. However, further tests such as x-rays, a blood profile, and echocardiogram may be needed to confirm the diagnosis, determine the severity of the disease, formulate an appropriate treatment plan. For cats, signs include respiratory distress, vomiting, and coughing. Be warned that your cat may suddenly die from heartworm disease.



Treatment for Heartworms

The earlier heartworm disease is detected, the higher the success rate of your pet’s treatment. Early detection also helps your pet endure fewer complications. For dogs, there are substantial risks in treating them. Bear in mind that serious complications occur less if your dog is healthy and when you strictly your veterinarian’s instructions.

The objective is to kill the adult worms and microfilariae in your dog as safely as possible. Heartworm treatment also requires hospitalization following your dog’s last treatment. Other medications may be prescribed to control its body’s inflammatory reaction as the worms die or broken down in its lungs.  

There is currently no effective and safe treatment option for cats. If your cat is diagnosed, your veterinarian may recommend medications to minimize the inflammatory response and curb heartworm disease. Surgery may also be needed to remove the heartworms from your cat’s body.  Surgery is a high-risk procedure and is usually reserved for severe cases of heartworms in dogs and cats. Surgery also increases your pet’s survival.



Preventing Heartworms

You can use a heartworm preventive, said Catherine Barnette, DVM, and Ernest Ward, DVM, of VCA Hospitals, an operator of over 1,000 animal hospitals in the US and Canada. When your dog has been successfully treated, it is important to begin a heartworm prevention program to prevent reinfection.

Presently, veterinarians recommend all cats receive year-round monthly heartworm preventives in areas where mosquitoes are active, according to Barnette and Ward. If you live in colder areas, where mosquitoes are seasonal, it is recommended to have your cat on a monthly heartworm preventive program for at least six months of the year.

There are excellent heartworm preventives for dogs and cats. Consult your veterinarian to help you determine which heartworm preventive is best for your dog or cat. Note that the preventives do not kill adult heartworms, will not eliminate heartworm infection, or prevent the symptoms of heartworm disease if adults are present in your pet’s body.  A blood test for existing heartworm is needed before starting a preventive program to evaluate your dog or cat’s current heartworm status.

Dogs and cats are vulnerable to heartworms, especially when they live in areas where mosquitoes are active all year round. Owners are strongly recommended to have their pet undergo a heartworm preventive program to prevent heartworm disease.