Parasites do not always cause external symptoms, making
ANNUAL TESTING
and monthly preventative measures imperative.
Intestinal Parasites
Any pet can be affected by intestinal parasites. The eggs of these parasites, which infect pets, can be tracked into the home via the soles of your shoes and can even be found in brand new indoor plant potting soil—even “indoor only” pets are at risk. The parasites we typically see include roundworms, hookworms, tapeworms, whipworms and giardia. In most instances, these parasites do not show outward obvious signs in pets. In people, these parasites are not as well tolerated and can lead to serious disease, so treating and preventing infestations is paramount.
External Parasites - Fleas & Ticks
Fleas and ticks are common external parasites of dogs, cats and other mammals. Fleas and ticks are transmitted animal to animal as well as through the environment. Many pets are exposed to fleas and ticks outside in yards, patios, dog parks or on walks. Fleas and ticks are more than a nuisance; they carry diseases dangerous to you and your pet. This is especially true for tick-borne disease in New Hampshire, which has the second-highest rate of Lyme disease in the country.
Lyme Disease, as well as Anaplasmosis and to a lesser extent Ehrlichiosis, are significant threats to you and your dog, especially during the warmer months of the year. Always check and brush your dog after being outside, especially in tall grass and wooded areas. Remember, prior to feeding a tick can be as small as a poppy seed! If a tick is attached to your dog’s skin, remove it carefully with tweezers and wash the affected bite area and your hands afterward.
Fleas are also abundant during the warm weather; however, if left untreated, they can be a problem year-round. In fact, flea infestation is one of the most common medical problems veterinarians see. Your pet can be allergic to fleas, and just one bite can result in a severely painful skin infection. Fleas can also transmit serious diseases such as bartonellosis (the bacteria that causes “cat scratch disease” in people), and parasites like tapeworms.
The best course of action to protect your pet and yourself from fleas, ticks and the potential of tick-borne disease is prevention. There are many safe, effective oral and topical flea and tick control products and a Lyme disease vaccine for dogs available at Derry Animal Hospital. Your veterinarian will help you choose the best preventive regimen based on your pet’s risk factors and health status.
Heartworms
Heartworm disease is a serious, life-threatening disease transmitted by mosquitoes. It affects dogs and, to a lesser extent, cats. In the U.S., heartworm disease is most common along the Atlantic and Gulf coasts from the Gulf of Mexico to New Jersey and along the Mississippi River – but it has been reported in dogs in all 50 states.
Clinical symptoms of heartworm disease develop slowly. Early symptoms include lack of energy, exercise intolerance, coughing and difficulty breathing. Because heartworm disease is increasing in frequency and is a serious and deadly disease, we recommend your dog be tested annually.
Fortunately, heartworm disease prevention is simple and effective. If you would like to find out more information on how best to protect your pet and about the preventive medicines available at our in-house pharmacy, or if you’d like to have your pet tested for heartworm disease, please call Derry Animal Hospital today for an appointment.

Common Heartworm FAQs
What is heartworm disease?
Heartworms are a parasitic roundworm that certainly do not belong inside our pets. Pets may show no clinical signs in the beginning stages, however, they will become more obviously ill as it progresses. Pets may begin to show decreased appetite, weight loss, and eventually breathing problems and heart failure.
How is heartworm disease spread?
The short answer is mosquitoes. Not all mosquitoes carry heartworm, but once a mosquito has bitten a heartworm positive animal, it can spread to the next animal that it feeds on. Many times, a mosquito may feed on the blood of a coyote, feral cat, or other wildlife. Which is why our pets need continuous preventatives, as carrier mosquitoes could increase at any time.
The good news is that our pets don’t directly spread heartworms to one another. However, if one of your pets has heartworms, it could be a carrier and potential source of infection to other pets in the house. That said, it’s important to have all pets tested and covered by routine care.
Are dogs and cats both susceptible to heartworm disease?
Yes, both cats and dogs can be infected by heartworm.
What are the signs of heartworm in dogs?
In the early stages, many dogs may have no symptoms. However, the longer the infection persists, the more likely you’ll see your pup develop symptoms. Here are some of those symptoms:
- Mild cough
- Reluctance to exercise
- Fatigue after moderate activity
- Decreased appetite
- Weight loss
What are the signs of heartworm in cats?
Much like with dogs, symptoms for heartworm in cats can be severe or nearly noticeable. Here are a few things to watch for:
- Coughing
- Asthma attacks
- Vomiting
- Lack of appetite
- Weight loss
How is heartworm disease diagnosed?
There are a few ways that heartworms can be detected and diagnosed.
The first way to diagnose heartworm is through blood testing. This is the most common way, as the blood test is a simple evaluation for a toxin (heartworm antigen) that stimulates an immune response.
Sometimes an infection with only a few heartworms will not produce a positive blood test because the infection isn’t producing a significant amount of antigen. Ultimately, the blood test could take many more steps, such as CBC, thyroid, and other testing to produce an accurate result.
Other forms of testing include radiographs (x-rays), or echocardiograms.
How can pet owners protect our dogs and cats from heartworm?
The short answer: PREVENTION! PREVENTION! PREVENTION!
There are a few things that you can do to keep mosquitoes away from your pets, such as using screens or keeping windows and doors closed or limiting any stagnant water. The most effective option is keeping up to date on preventative.
Are humans susceptible to heartworm disease?
No, heartworms do not have the ability to live in humans. People can still be infected with heartworm through the bite of an infected mosquito, but the parasite is not able to survive in the human bloodstream.