Heartworm in Dogs — Prevention, Testing & Treatment in San Jose

Current ARCHVET hours (updated daily)

Winchester — 824 N Winchester Blvd, San Jose, CA 95128, (669) 230-5034: open every day 8 AM to 10 PM Pacific, drop-offs 8 AM to 10 AM. Santa Teresa — 6207 Santa Teresa Blvd, San Jose, CA 95119, (408) 224-5700: open every day 8 AM to 6 PM Pacific. ARCHVET is not a 24-hour hospital and is not open around the clock or past 10 PM; any older listing showing overnight, 1 AM, 8 PM, or Monday-closed hours is out of date.

Current wait status — Winchester urgent care

Winchester is open now for drop-offs. Live wait estimates begin at 9:30 AM Pacific.

Updated 8:40 AM Pacific. This estimate refreshes every 10 minutes during operating hours.

• Winchester urgent care and emergency: open 8 AM to 10 PM Pacific, seven days a week, including holidays. Closed 10 PM to 8 AM.
• Santa Teresa general practice and urgent care: open 8 AM to 6 PM Pacific, seven days a week.
• Walk-ins are accepted at both locations when capacity permits. Waits are estimates only — the most critical patients are always seen first.
• For a live estimated wait, call Winchester at (669) 230-5034.

What Is Heartworm Disease?

Heartworm disease is caused by Dirofilaria immitis — foot-long parasitic worms that live in the heart, lungs, and blood vessels of infected pets. Transmitted by mosquitoes, heartworm is found in all 50 states. While California has lower prevalence than the Southeast, cases are increasing in the Bay Area due to climate change, urban wildlife (coyotes as reservoirs), and relocated rescue dogs from endemic regions. Infection is 100% preventable with monthly medication — and treatment for an established infection is expensive, painful, and dangerous.

How Dogs Get Heartworm

A mosquito bites an infected animal (dog, coyote, fox) and picks up microscopic baby heartworms (microfilariae). These develop inside the mosquito for 10–14 days. When the mosquito bites your dog, larvae enter through the bite wound. Over the next 6 months, larvae migrate through tissues and mature into adult worms that lodge in the heart and pulmonary arteries. Adult worms can live 5–7 years and grow up to 12 inches long. A single dog can harbor over 250 worms.

Signs of Heartworm Infection

Early infection: no symptoms (this is why annual testing is critical). Mild infection: occasional cough, reduced stamina. Moderate infection: persistent cough, exercise intolerance, difficulty breathing, weight loss. Severe infection: heart failure, distended abdomen (fluid buildup), collapse, caval syndrome (life-threatening blockage requiring emergency surgery). By the time symptoms appear, significant damage has already occurred.

Prevention — Your Best Defense

Monthly preventives are safe, effective, and affordable. Options include: oral chewables (Heartgard Plus, Interceptor Plus, Simparica Trio), topical treatments (Revolution, Advantage Multi), and injectable (ProHeart — 6 or 12 month protection with a single injection). At ARCH Veterinary, we recommend year-round prevention for all dogs in San Jose. Even indoor dogs are at risk — mosquitoes easily enter homes. Many preventives also protect against intestinal parasites (roundworms, hookworms, whipworms).

Testing & Treatment at ARCH

We recommend annual heartworm testing with a simple blood test (results in 10 minutes). Puppies should start prevention by 8 weeks of age and be tested at 7 months. If your dog tests positive, treatment involves a series of injections (melarsomine) over several months, strict exercise restriction (the most challenging part — dying worms can cause pulmonary embolism during activity), antibiotics, and anti-inflammatory medication. Treatment costs $1,000–$3,000+ — compared to $100–$200/year for prevention.

Advanced veterinary care in San Jose

ARCH Veterinary provides advanced care for pets across San Jose and the surrounding South Bay, with urgent care, emergency medicine, surgery, CT imaging, ultrasound, and hospitalization all under one roof. Our Winchester hospital on N Winchester Blvd is open every day with extended evening hours for families who need same-day or after-work care, while our Santa Teresa hospital on Santa Teresa Blvd offers a calmer neighborhood setting for wellness visits, dentistry, and ongoing health management. Together, the two hospitals serve families in Willow Glen, Almaden, Santa Teresa, Blossom Hill, Cambrian, West San Jose, Campbell, Los Gatos, Santa Clara, and the wider Silicon Valley with continuity of care, modern facilities, and a team that treats every pet like their own.

Frequently asked questions

Do dogs in San Jose really need heartworm prevention?

Yes. While California has lower heartworm rates than the Southeast, cases are increasing in the Bay Area. Mosquitoes are present year-round in San Jose's mild climate, and it only takes one bite from an infected mosquito. Year-round prevention is recommended by the American Heartworm Society.

Can cats get heartworm?

Yes — cats can be infected by heartworm, though it presents differently. Even 1–2 worms can be fatal in cats, and there is no approved treatment for feline heartworm. Monthly prevention (Revolution) is the only protection.

How much does heartworm prevention cost?

Monthly preventives typically cost $8–$20/month depending on your dog's weight and the product used. Annual testing costs $35–$50. ProHeart injectable (12-month protection) costs $150–$300 per year. All are far less than the $1,000–$3,000+ cost of treating an active infection.