Heartworm life cycle chart illustration

Understanding Internal and External Parasites in Dogs and Cats: The Menace of Heartworm

Pets, much like their human counterparts, can fall prey to various internal and external parasites that threaten their health and wellbeing. For dog and cat owners, it’s crucial to understand these parasitic threats to ensure our furry friends remain healthy and happy. We will delve into the common parasites that affect dogs and cats, with a special focus on the potentially deadly heartworm.

External Parasites: Fleas and Ticks

Fleas are small, wingless insects that thrive by consuming the blood of their hosts. They can cause severe itching, irritation, and in extreme cases, lead to hair loss and secondary skin infections. Fleas are also capable of spreading other parasites like tapeworms and diseases such as flea allergy dermatitis.

Ticks are another notorious parasite, known for their ability to transmit diseases such as Lyme disease, ehrlichiosis, and Rocky Mountain spotted fever. These arachnids latch onto the skin of pets, feeding on their blood and can remain undetected for several days. Anaplasmosis and babesiosis are other serious conditions spread by ticks, leading to symptoms ranging from fever and lethargy to severe anemia.

Preventatives: The most common external parasite prevention that we use that ONLY gets fleas and ticks, in dogs is called Bravecto. It is an oral treat that you give once every 3 months. In cats we like to use Revolution Plus, which is a topical medication that last 1 month.

Internal Parasites: Worms

The most common internal parasites are worms, including roundworms, hookworms, tapeworms, and whipworms. These parasites reside in the gastrointestinal tract and can cause a variety of symptoms from mild discomfort to severe digestive issues or even death if left untreated.

Deworming Treatments

Effective deworming treatments vary depending on the type of worm and the specific needs of the pet. The most Common dewormers include:

  • Pyrantel Pamoate: Often used for roundworms and hookworms.
  • Fenbendazole: Effective against several parasites, including some tapeworms, roundworms, hookworms, and whipworms.
  • Praziquantel: Specifically targets tapeworms.
  • Milbemycin Oxime: Can be used against a variety of worms and is also employed in some heartworm preventatives.

These medications are typically administered orally, and many are combined into broad-spectrum products that can treat multiple types of worms at once.

Tapeworms are treated with a completely different medication so we generally just treat that when we see it.

Heartworm: A Special Concern

Among the internal parasites, heartworm stands out due to its severity and complex life cycle. Transmitted through the bite of an infected mosquito, heartworms are a serious and potentially fatal threat to both dogs and cats.

Lifecycle of Heartworm

  • Transmission: It starts when a mosquito feeds on an infected animal, ingesting microfilariae, which are baby worms.
  • Development: Inside the mosquito, these microfilariae develop into infective larvae over 10 to 14 days.
  • Infection: When the infected mosquito bites another pet, the larvae are deposited onto the surface of the animal’s skin, from where they enter the new host.
  • Maturation: Once inside the host, the larvae migrate to the heart and major blood vessels of the lungs, where they mature into adults, which can grow up to 12 inches long.

Impact on Health

In dogs, heartworms can cause a condition known as heartworm disease, impacting the heart, lungs, liver, and kidneys, and can be fatal if untreated. Symptoms may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss.

Cats can also suffer from heartworm disease, though they are an atypical host for these parasites. Symptoms in cats can be very nonspecific and may mimic many other cat diseases. Unfortunately, in cats, the first sign of heartworm disease could be sudden collapse or death.

Prevention and Treatment

Preventing heartworm disease is much safer, easier, and more economical than treating the advanced stage of the disease. Prevention typically involves administering a monthly heartworm preventive medication, which can be in the form of pills, topical liquids, or injections administered by a veterinarian. Before starting your pet on a preventative we will perform a heartworm test. This test is a simple blood draw which then takes 10 minutes to run. This is performed to ensure that your dog doesn’t already have heartworm. The preventative that we recommend and use the most is Simparica Trio. Which is a medicated treat that they take once a month. We love this one because this preventative will take care of all the internal and external parasites we’ve talked about, along with heartworm. Their are other preventatives that we use, and we can discuss the best plan for you and your pet.

For dogs diagnosed with heartworm disease, the treatment can be risky and involves administering medication to kill the worms over a period of time. The process must be closely monitored by a veterinarian because as the worms die, they can cause blockages in the pulmonary vessels.

Cats do not have an approved treatment for heartworm infection, which underscores the importance of prevention.

Final Thoughts

Regular check-ups with a veterinarian, routine use of preventives, and maintaining a clean environment for your pets are the best strategies to prevent these parasites from becoming a serious health issue. Remember, the health and happiness of your pets largely depend on the proactive steps you take to protect them. All inside and outside dogs and cats can be affected by this. Call us today do to make a detailed health plan that will work best for you and your pets, to keep them protected.


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