By The Bethany Animal Hospital Team
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March 22, 2026
As spring arrives, warmer temperatures and longer days mean one thing for pet owners: mosquito season is starting. That’s why National Heartworm Awareness Month in April is the ideal time to focus on heartworm prevention and schedule a heartworm test for your dog or cat. At Bethany Animal Hospital, we see the impact of heartworm disease every year. This potentially fatal parasite is almost 100% preventable, yet cases continue to rise across the Midwest. Early testing and consistent prevention can protect your furry family member for life. What Is Heartworm Disease? Heartworm disease is caused by the parasitic worm Dirofilaria immitis. Adult worms (up to 12 inches long) live in the heart, lungs, and blood vessels of dogs and cats, causing severe damage to the cardiovascular and respiratory systems. Left untreated, it can lead to heart failure, lung disease, and even sudden death. Dogs are the primary hosts, but cats can also become infected (though their symptoms and treatment differ). The good news? With proper testing and prevention, heartworm disease is almost entirely avoidable. How Do Pets Get Heartworm? (Transmission Explained) Heartworms spread exclusively through mosquitoes—not through direct pet-to-pet contact. 1. A mosquito bites an infected animal and picks up microscopic heartworm larvae. 2. Inside the mosquito, larvae mature into an infectious stage (this takes about 2 weeks in warm weather). 3. The mosquito bites your pet, transmitting the larvae. 4. Larvae migrate through your pet’s body for 6–7 months before becoming adult worms in the heart and lungs. Why April is critical in Sycamore, IL: Mosquito activity ramps up as temperatures consistently hit 50–60°F and higher. In Northern Illinois (including DeKalb County), this often begins in late April or early May. The American Heartworm Society (AHS) reports heartworm transmission is possible wherever mosquitoes thrive—and with climate trends, the season is lengthening. Signs of Heartworm Infection in Pets Early stages are often silent, which is why annual testing is essential. Watch for these common heartworm symptoms: ● Mild, persistent cough (especially after exercise) ● Fatigue or reluctance to exercise ● Decreased appetite and weight loss ● Difficulty breathing or rapid breathing ● Swollen abdomen (in advanced cases) ● In cats: Vomiting, asthma-like symptoms, or sudden collapse Don’t wait for symptoms—heartworm testing catches it early. Why Annual Heartworm Testing Matters (Especially Now) The AHS recommends year-round heartworm prevention and annual testing for all dogs and cats in the continental U.S. ● A simple blood test detects heartworms before damage occurs. ● Testing is quick, inexpensive, and can be done during your pet’s annual wellness exam. ● Positive results allow early treatment, dramatically improving outcomes. Local note for Midwest pet owners: The AHS 2022 Incidence Map (latest available) shows heartworm cases rising nationwide, with endemic activity throughout Illinois and the Midwest. Northern Illinois, including the Chicago suburbs and Sycamore area, sees confirmed cases every year. Warmer springs and urban microclimates keep mosquitoes active longer—making consistent protection non-negotiable. Heartworm Prevention Options: Safe, Effective, and Year-Round At Bethany Animal Hospital, we tailor prevention to your pet’s lifestyle, age, and health. All options are FDA-approved and highly effective when given correctly: ● Monthly oral preventives — We offer Heartgard® and NexGard Plus® for in-hospital pick up, or a variety of other options on our online pharmacy: https://bethanyvet.bluerabbitrx.com/ ● Monthly topical preventives — We offer NexGard Combo® in-hospital for cats, or a variety of other options on our online pharmacy: https://bethanyvet.bluerabbitrx.com/ ● 12-month injectable for dogs — ProHeart® 12 (newer option for long-term protection) Pro tip: Year-round protocols are the AHS gold standard—even in “colder” Midwest winters. Gaps in protection (even one missed dose) can leave your pet vulnerable, especially with unpredictable Illinois weather. Protect Your Pet This National Heartworm Awareness Month April is the perfect reminder to act. Warmer weather is here, mosquitoes are waking up, and heartworm risk is rising across Illinois. Don’t gamble with your pet’s heart health. Schedule a heartworm test and prevention consultation at Bethany Animal Hospital today. Call us at (815) 756-8925 or (815) 239-6938 Visit us: 2400 Bethany Road, Sycamore, IL 60178 Online: bethanyvet.com – Request an appointment or shop our pharmacy for preventives. Our compassionate team has been serving Sycamore, DeKalb, and surrounding communities since 1959. We’ll help you choose the best heartworm prevention plan for your dog or cat and answer every question.
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