Mosquitoes named serial killers of pets

By Beth Leermakers

April is Heartworm Awareness  month. I recently had a heart-breaking (pun intended) reminder of the devasting impact of heartworm disease. One of my foster dogs who was recently adopted was diagnosed with a grade 5 heart murmur (meaning he’s at high risk for congestive heart failure). When tested, Bosco was very high heartworm positive.

This young dog’s life will be shortened because his previous owners didn’t give him monthly heartworm preventive. If you’ve been tempted to skip this medication, please keep reading to learn why prevention is far better than treatment — and where to purchase affordable heartworm prevention. 

What is heartworm disease?

Heartworm disease is a serious, potentially fatal disease caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets. These parasites cause severe lung disease, heart failure and permanent damage to other vital organs in the body. While primarily associated with dogs, heartworm disease also affects cats and ferrets.

How is it transmitted?

Mosquitoes transmit heartworm disease. When a mosquito bites an infected animal, it ingests microscopic baby worms called microfilariae. Over a period of 10 to 14 days, these develop into an “infective stage” inside the mosquito.

When that mosquito bites another dog or cat, the infective larvae are deposited onto the surface of the skin and enter the new host through the bite wound. Once inside, it takes approximately six months for the larvae to develop into sexually mature adult heartworms. According to the American Heartworm Society (www.heartwormsociety.org), a single mosquito infected with heartworms can travel three miles and feed on multiple pets in one day.

Starting at what age and how often should pets be tested?

Because heartworms can live for five to seven years in dogs and up to two or three years in cats, the number of worms in an infected pet can increase with each passing mosquito season.

Dogs: Adult dogs over seven months of age and previously not on a preventive need to be tested prior to starting heartworm prevention. They need to be tested six months and 12 months later and annually after that.

Cats: Cats should be tested before being put on prevention and re-tested as the veterinarian deems appropriate to document continued exposure and risk.

Heartworm infection in cats is harder to detect than in dogs, because cats are much less likely than dogs to have adult heartworms. Screening cats typically includes the use of both an antigen and an antibody test (the latter detects exposure to heartworm larvae). Your veterinarian may also use x-rays or ultrasound to look for heartworm infection. 

How can you prevent heartworm disease?

Prevention is significantly easier, safer and more affordable than treating an active infection. Heartworm infection is almost 100 percent preventable in dogs and cats. The American Heartworm Society recommends giving preventives every month, year-round (unless you’re using an injection that lasts six or 12 months). 

When to start heartworm prevention: The American Heartworm Society recommends that puppies and kittens start taking heartworm preventive as early as the product label allows, and no later than eight weeks of age. 

Types of preventives: Heartworm preventives for dogs come in monthly chewable pills (e.g., Heartgard Plus, Tri-Heart Plus, Simparica TRIO, Trifexis or Sentinel), topical “spot on” medications (e.g., Advantage Multi, Revolution) and an injectable medication that is given every 6 or 12 months (ProHeart6 or Proheart12). For cats, there are pills (Interceptor, MilbeGuard) and topicals (Advantage Multi, Bravecto Plus, NexGard Combo, Revolution). Heartworm preventives require a prescription. 

Some preventives only prevent heartworms, while others protect pets from heartworms and intestinal parasites. Some preventives protect pets from many different parasites, including heartworms, intestinal worms, fleas, ticks and mites. 

Where to buy affordable preventives:

Chewy or a discount pet pharmacy (such as 1-800-PetMeds) may have lower prices than your vet clinic.

Texas Coalition for Animal Protection (TCAP; www.texasforthem.org; 940-566-5551). Required heartworm test: $20. Tri-Heart Plus (dogs): $30-$40 for a six-month supply (depending on the dog’s weight). Trifexis (six-month supply): $135.  

Premium Vaccine Package: Rabies, DAPPv, Bordetella, Lepto and Heartworm Testing: $60. Plus $60 – $80 for 12 months of Tri-Heart Plus. 

Spay Neuter Network; (SNN; www.spayneuternet.org; 972-472-3500). Required heartworm test: $25. 12-month supply of preventive: $55-$85 (depending on dog’s weight).

Dog vaccination package (Includes Rabies, DAV2PV, Bordetella (Kennel Cough), Heartworm test, one year supply of heartworm prevention): $126-$156 (depending on dog’s weight). 

How is heartworm 

disease treated?

The treatment process differs significantly between species:

In Dogs: Treatment involves a series of two or three injections of melarsomine (an arsenic-based drug), combined with antibiotics (Doxycycline), a steroid (Prednisone) and strict exercise restriction for several months. Physical activity must be limited because dying worms can lodge in the blood vessels, causing life-threatening complications.

In Cats: Unfortunately, there is currently no approved drug therapy for heartworm infection in cats. The drug used to treat infections in dogs is not safe for cats. Cats with heartworm disease can often be helped with good veterinary care. The goal is to stabilize your cat and determine a long-term management plan. If your cat is diagnosed with heartworms, your vet may recommend medications to reduce the inflammatory response and the resulting heartworm disease, or surgery to remove the heartworms.

Where to go for more affordable treatment:

CHEW Animal Clinic (www.chewac.org; 8484 Walnut Hill Ln, Dallas 75231; 469-620-2828). CHEW offers comprehensive medical, surgical and critical care services at affordable prices for qualified families. Chew’s Compassion Fund (funded by donations) helps provide veterinary care. People can apply for one-time assistance (https://www.chewac.org/compassion-fund-application). 

Texas Foundation for Animal Care (https://texasfoundationac.org/ ; 1120 South Henderson St., Fort Worth 76104; 817-586-5490). TFAC offers affordable heartworm treatment. 

Our cats and dogs depend on us to protect their hearts from serial killer mosquitoes.