April showers bring May flowers—and, unfortunately, increased mosquito populations. Most areas across the United States deal with mosquitoes during the moist spring and summer months, but some warmer climates deal with them year-round. These pesky critters are not only an annoyance, but can also transmit heartworms to our pets. 

April is National Heartworm Awareness Month, and Animal Clinic of Council Bluffs wants to ensure pet owners understand how the disease can impact their pets, and how to effectively protect them.

Heartworm disease in pets—the basics

The heartworm parasite is transmitted through bites from infected mosquitoes, who pick up the heartworm larvae from other infected pets or wildlife reservoirs. Once inside a new host, commonly a dog, coyote, wolf, fox, ferret, or cat, the larvae migrate through tissues and the bloodstream to reach the heart, where they settle in and eventually grow up to a foot long. 

In dogs, multiple worms are usually transmitted at one time and begin reproducing once they reach adulthood. Over time, infected dogs can host hundreds of these large worms, which permanently damage the heart and lungs. Severe or long-standing infections can be fatal.

Cats are not the heartworms’ ideal host, so most infected cats harbor only one or two worms, which often cannot reproduce. However, one or two worms in a cat can cause serious heart and respiratory issues, and some infected cats may die suddenly. 

Heartworm diagnosis in pets

Most heartworm-infected pets do not show outward clinical signs for several months or years after infection, so an annual heartworm blood test, which detects that adult female worms are present, is recommended for all dogs. An infected dog can test negative for around six months after infection, because these worms are not yet mature—another reason why testing should be repeated annually, especially for pets adopted from areas with high infection rates.

Diagnosis in cats is difficult, and may require multiple blood tests and imaging, which are usually ordered only for symptomatic cats with respiratory problems that another diagnosis cannot explain. Most infected cats likely go undiagnosed, which means the true prevalence in this species is probably underestimated.

Heartworm disease signs in pets

Most pets do not show signs until infection has been present long-term. Signs they eventually show are related to heart or lung dysfunction and may include:

  • Coughing
  • Exercise intolerance
  • Fatigue
  • Decrease appetite
  • Weight loss
  • Vomiting—only in cats
  • Abdomen or lung fluid accumulation
  • Sudden death

Heartworm disease treatment in pets

Heartworm treatment is available for dogs, but can take several months. During treatment, affected dogs must remain on cage rest, because excitement or activity could cause dying worms to lodge in blood vessels and create dangerous blood clots. If infection is severe, pets will likely deal with lifelong heart or lung damage, despite treatment, which may include:

  • Heartworm-killing injections — An injection series is  given about a month apart to kill the adult worms. After each injection, your pet will require a hospital day-stay for observation and to alleviate any injection-site pain.
  • Antibiotics — Heartworms live closely with a certain bacteria that must be killed with oral antibiotics prior to the injections.
  • Steroids — Steroids reduce the chances of an anaphylactic-type reaction to the dying worms.
  • Surgery — Rarely, a severe infection requires manual, surgical worm removal.

Unfortunately for infected cats, no treatment options exist. The injectable medication used for dogs is unsafe for cats, so they are usually closely observed and given supportive medications for breathing or heart problems until the worms die on their own—which could take several years. Surgery may be an option for some cats.

The importance of heartworm prevention in pets

Heartworm disease can be completely avoided in most pets with a monthly medication that kills immature heartworms. This medication is inexpensive and easy to administer to dogs and cats, making prevention a significantly better option than treatment.

Here are a few facts about heartworm prevention:

  • All dogs and cats need heartworm prevention, because they are all exposed to mosquitoes—including indoor cats.
  • Monthly dosing is required, because after this time the worms become more difficult to kill.
  • Heartworm prevention should be used year-round, because mosquitoes can re-emerge at any time. Most heartworm products also help control intestinal parasites, which are active year-round.
  • A year of heartworm prevention for a mid-sized dog costs around $100, but heartworm treatment can cost an average $1,200 to $1,800.
  • Heartworm prevention medications are backed by a manufacturer guarantee—if you used them correctly and your pet is infected with heartworm, they will reimburse you for treatment costs.

Heartworm disease has been found in every state, and the incidence is rising in many areas as pets from heartworm-endemic Southern states are transported and adopted into Northern homes. No pet is safe from heartworm disease, but you can spare yourself and your pet from this parasite’s devastating effects with a simple prevention protocol. 

Animal Clinic of Council Bluffs offers multiple heartworm prevention options, so you’re sure to find one that suits your pet’s needs. Contact us to schedule an appointment for a wellness visit, heartworm test, or parasite control consultation.