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Many dog owners have questions about heartworms when they enter TCAP clinics. Concerns about heartworms seem to peak during the summer months, but in the North Texas climate, heartworms are a threat to dogs year-round. Two common misconceptions we hear are that “dogs do not need heartworm prevention during colder months” and that “inside dogs don’t need heartworm prevention”. Both of these beliefs contribute to the 10-20 heartworm positive dogs that we see each month at TCAP clinics.

What Are Heartworms?

Heartworms are parasites (also known as Dirofilaria immitis) that live in the heart and pulmonary arteries of an infected animal. Adult heartworms can reach up to 1 foot in length and mainly use dogs as their host. If left untreated in dogs, heartworms reproduce in number up to several hundred worms.

Where Do Heartworms Come From?

Heartworms are transferred by mosquito bites. Adult heartworms produce microscopic baby worms (also known as microfilaria) and distribute them through an infected dog’s bloodstream. Mosquitos that bite heartworm-infected dogs will drink in these baby heartworms. Over the next 14 days, these microfilaria develop into “infective stage” larvae. When infected mosquitos bite healthy dogs, they will then transfer larvae into the dog’s bloodstream. Once inside a new host, the microfilaria mature into adult heartworms.

Signs of Heartworms in Dogs

When a dog is first infected with heartworms, there are no visible or detectable signs. As the heartworms grow, dogs begin to cough, have shortness of breath, and experience lethargy. As heartworms become worse, dogs will experience weight loss, kidney damage, and liver damage. In many cases, there are no signs of heartworms before an infected dog collapses due to blood flow blockage. Oftentimes, if an infected dog is left untreated, it will die from damage to the heart and lungs or from complete blood flow blockage.

Treatment and Prevention

Heartworms are easily diagnosed through a heartworm test. This test requires a blood sample from a dog and takes approximately 5 minutes.

Heartworms can be very expensive and time consuming to treat. The process varies depending on the severity of a dog’s heartworm problem and the severity of the side effects from treatment. Most treatments require close monitoring and can cause damage to a dog’s liver and kidneys.

The best approach to heartworms is prevention. No heartworm testing is required for pets under 6 months of age, and it is recommended that they begin heartworm prevention before they reach that age. At TCAP, pets over 6 months of age must receive a heartworm test prior to receiving any prevention. Dogs also must be retested on a yearly basis. Dogs that are heartworm positive may be injured or even killed by taking heartworm prevention. It is important to ensure that your pet is clear of heartworms with a heartworm test prior to giving it any prevention.

Only veterinarians can provide heartworm tests/prevention. Year-round prevention is essential if your pet lives in a climate that is beneficial for mosquitos, like North Texas. TCAP provides heartworm testing and prevention during vaccine hours on a walk-in basis. To find a clinic close to you, visit TCAP’s vaccination schedule below.

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