Canine Parasites

Canine Heartworms

Heartworm disease is caused by Dirofilaria immitis, a 3-6 inch long worm about the diameter of pencil lead. The worm lives in the heart and major blood vessels of the lungs. This eventually causes heart failure and death if untreated. Heartworms love to live in dogs and wild canines such as wolves, coyotes and fox, but can also be found in cats (rare), ferrets, and even sea lions. When an animal gets heartworms, it causes an elevated pressure in the pulmonary arteries (pulmonary hypertension), which increases the workload of the right side of the heart. If the heartworms continue to go untreated (they can live 5-7 years), the right side of the heart eventually fails. Heartworms can also cause inflammation in the lungs.

Heartworm disease is transmitted from one infected dog to another by mosquitoes. A mosquito bites a dog who is already infected and picks up the microflaria (baby heartworms). The mosquito incubates them for 1 to 2 weeks and then when it bites another dog it passes them into the blood stream of the new dog. The larvae have to spend time in a mosquito; heartworms cannot be transmitted by a blood transfusion or an injection. The larvae then travel through the bloodstream to the heart where they anchor themselves and start to grow. It takes about six months after becoming infected before a dog will have the clinical disease and test positive.

Heartworm disease is easily detected via a blood test that is run right here in the clinic. Results are available within as little as 15 minutes. Treatment of infected dogs is risky and expensive ($400 - $700). Occasionally a severely infected animal will die during treatment and many have residual heart disease due to the damage caused by the parasite.

Heartworm disease is readily preventable by giving a monthly preventative. We highly recommend that dogs in this area should receive preventive all year round. If you travel south with your pet they must be given all year round. There are currently many highly effective preventatives on the market some oral, some topical and even a six-month injectable. Choosing which preventive is right for you and your dog is a decision to be made with the help of your veterinarian. Heartworm disease is very common in Monroe and Juneau counties, so your dog should be tested every one to two years depending on your veterinarian’s recommendations. Even dogs that “hardly ever” go outside need to be on Heartworm preventive. Heartworm preventives are prescription medications that must be prescribed by a licensed veterinarian.

For more information and to see the interactive parasite prevalence map that shows the risks of heartworm and other parasite exposure in the United States check out:

Number of cases of Canine Heartworm Diagnosed at Tomah Veterinary Clinic:
2009 10
2010 19
2011 18
2012 17

Please do not let your dog be the next statistic. Call and ask our staff about getting your dog on prevention.

Dogs and Fleas

Fleas are small insects that live on the blood of mammals. Dogs and cats commonly get fleas from other dogs and cats and some wildlife—they do not come from sand. Since fleas can live for a long time off of an animal, your pet can also get them by being in an area where an animal with fleas has been, e.g., new apartment, park, wayside, boarding / grooming / veterinary facility, etc. Fleas can also be brought into the home by owners who move through areas with large amounts of fleas, e.g. Your front lawn if you have stray cats in the area, or large amounts of wild animals such as rabbits.

Fleas cause itching, dermatitis, blood loss, and tapeworms. If you get enough of them in a house, they may bite people. Flea infestations are much more easily prevented than treated. The most effective preventives are the topical and oral products that contain insect growth regulators. These kill adult fleas as well as preventing the development of juvenile fleas. Other less effective products are sprays, powders, collars, and dips. For best effect it is recommended to apply flea prevention every month all year round or at minimum when the daily temperature is routinely over 50 degrees Fahrenheit.

If your pets do get fleas, you can expect it to take 3-4 months to fully treat the infestation. All animals with fur in the house will need a high quality topical and oral flea prevention every 30 days for a minimum of 3 treatments to break the lifecycle. A newer product available is Capstar™, an oral tablet that kills most adult fleas on the pet within 4-6 hours, which when used in combination with topical flea preventives is a quick way to begin eliminating flea infestation. As well as medications given to your pet, you may need to treat your house or kennel area with flea bombs or contact a pest control service in the face of an active infestation. Fleas are most prevalent in summer and fall in our area but can survive year round on untreated animals.

Always make sure you are using the appropriate size and age product for your pet. Never put cat or any other species flea product on your dog.

Dogs and Ear Mites

Ear mites are small parasites (Otodectes cynotis) related to ticks that enjoy living in and sometimes around the ears of pets. Ear mites are a common problem in cats and kittens, particularly those that go outdoors and those that hunt. Although dogs are significantly less likely to have ear mites then cats we do see them occasionally in puppies from crowded kennels, humane societies, or pet shops that may have ear mites. If your dog is having an ear infection it is more likely due to bacteria or yeast. Have your veterinarian perform an ear exam and smear to determine an appropriate treatment.

Dogs and Ticks

Ticks are small parasites that live on the blood of animals. It is common knowledge that ticks are in wooded areas where deer and other wildlife live. What many people don’t realize is that ticks can also be found in open grassy areas such as lawns. The ticks can arrive and be carried into yards by wildlife (such as deer, raccoons, opossums, turkey, and coyotes) and even stray cats and dogs. Ticks also don’t feed on just one animal in their adult life, they feed off multiple species in one life cycle which allow them to travel to many locations and to effectively spread disease. Ticks transmit diseases including Anaplasmosis, Ehrlichiosis, Lyme Disease, Rocky Mountain Spotted Fever and many others.

Tick activity peaks in spring and fall but they can be active in remotely warm weather (> 40 degrees). Topical tick preventatives are good but not 100% effective. Most preventatives kill the tick after it attaches but before it transmits disease. A good rule of thumb for tick preventions is if a dog walks through a hundred ticks, the prevention should stop all but one from attaching. If you live in a heavily infested region or your dog swims a lot, you should discuss vaccination for Lyme Disease with your veterinarian.

Always make sure you are using the appropriate size and age product for your pet. Never put cat or any other species flea product on your dog.

For more information on tick borne disease such as Lyme and Anaplasma and to see the interactive disease prevalence map that shows the risks of tick borne disease and other parasite exposure in the United States check out:


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