Parasites & Worms in Animals

Heartworm

Heartworm has been diagnosed in dogs in all parts of the world and is actually very common. This may be due to the fact that heartworm has a virtual 100% prevalence rate in unprotected dogs living in highly endemic areas. Heartworm, also known as Dirofilaria immitis, is transmitted by mosquitoes. The mosquito injects a microscopic larvae which grows into an adult worm six to eighteen inches long inside the heart of the affected dog.

The worms can cause mild symptoms, such as coughing, but with time, more severe symptoms such as congestive heart failure, weight loss, fluid build up in the abdomen, fainting spells, anemia, collapse, and death usually occur.

Luckily we have several excellent medications which can prevent heartworm if given as directed. There are oral medications which need to be given monthly, and which also help protect against some intestinal parasites. There is one topical medication which is also applied monthly. An injectable medication, ProHeart, which is administered every six months, is back on the market after being withdrawn for several years.

Even if a dog has been given preventatives, it is still important to have annual checkups for heartworms by doing a blood test. Many people are not totally compliant about giving the preventive medication on time, and no medication works perfectly. If a dog has heartworms and it is given a dose of preventative, there can be a reaction that is detrimental to the dog, even deadly.

Heartworms were once thought to be rare in cats. Now we know the incidence is anywhere from 10% to 50% of the canine rate. Heartworm disease in cats is different than in dogs. Cats usually test negative on the routine blood test done in the hospital, the worms are smaller and usually do not produce microfilaria which are like baby heartworms that circulate in the bloodstream. Veterinarians have to do different tests, sometimes more than one, to diagnose heartworms in cats.

The symptoms in cats are different also. Cats usually have asthma signs or cough, even vomit. Cats can die acutely. The treatment for adult heartworms in dogs is expensive and potentially harmful to the dog. This is why it is much better to just prevent them in the first place. There is not a treatment for adult heartworms in cats. Many veterinarians are now recommending monthly heartworms preventative for cats in addition to dogs, since heartworm can be such a serious problem.

Hookworms

Hookworms are small, thread- like parasites of the small intestine where they attach and suck large amounts of blood. These parasites are found in almost all parts of the world, being common in dogs, and occasionally seen in cats.

Symptoms are usually diarrhea and weight loss. The parasites can actually suck so much blood that they cause pale gums from anemia, and black and tarry stools. Young puppies can be so severely affected that they die. Infection can be by ingestion of breast milk from an infected mother, by ingestion of infective eggs, or by skin penetration of infective larvae.

Since the adult parasites are so small, they are rarely seen in the stool. Diagnosis of these parasites is by the veterinarian or laboratory finding the microscopic eggs in the stool.

There are a variety of medications that can kill hookworms. The important point to know is that there is no one medicine that will kill all the types of intestinal parasites that exist. Some of the monthly “heartworm preventatives” will also work to treat hookworms.

People exposed to hookworms can develop a rash called cutaneous larval migrans. Infective larvae, usually from contaminated yards, can penetrate human skin and cause red tracts.

Roundworms

There are many types of roundworms, but some of the most common are intestinal parasites of dogs, cats, and raccoons. Puppies are frequently born with roundworms, and kittens can be infected via the mother’s milk or feces. Adult roundworms are ivory colored, four to six inches long, and round (not flat ) in shape. These parasites can cause diarrhea, vomiting, weight loss, and even coughing in these young patients. In the usual case, the owner will not see the adult roundworms passed in the stool. This is why it is important for the veterinarian to do a laboratory test to check for any parasites that might be present. We check for parasite eggs with a microscope. You should bring a fresh stool sample (one that was produced that day) to your puppy or kitten’s appointment.

It is important to know that animal roundworms can be transmitted to people, and in some cases can cause serious disease. In a recent study from the Center for Disease Control (CDC), it was reported that almost 14 % of all Americans are infected with Toxocara, the most common roundworm of pets. Although most people infected have no symptoms, the parasite is capable of causing blindness (especially in children) and other systemic illness. The infective agent is the microscopic egg in the animal’s stool. It is known that these eggs are very resistant to environmental conditions. They have been shown to live in yards, playgrounds, and fields for up to 10 years.

The most dangerous roundworm is Baylisascaris, a parasite of raccoons that has an affinity for brain tissue. Children infected with this parasite have suffered severe, permanent mental retardation. The majority of raccoons carry this parasite. If wildlife is present on your property, you should patrol the grounds and any raccoon stools should be treated as hazardous waste. Wear disposable gloves to double bag and dispose of the feces. The only thing that will kill the remaining eggs in the soil is fire.

The CDC recommends regular deworming of all puppies and kittens to try to reduce the exposure to people. A medication will be dispensed when your puppy or kitten is first seen. Another important measure is monthly parasite preventative, or what we sometimes call “heartworm preventative”. Many of these drugs are also effective for roundworms, and are an important part of a wellness program.

Tapeworms

Tapeworms live in the digestive tracts of vertebrates as adults and often in the bodies of various animals as juveniles. In a tapeworm infection, adults absorb food predigested by the host, so the worms have no need for a digestive tract or a mouth. Large tapeworms are made almost entirely of reproductive structures with a small “head” for attachment. Symptoms vary widely, depending on the species causing the infection. The largest tapeworms can be 20 m or longer. Tapeworm awareness is importance to humans because they infect people and livestock. Two important tapeworms are the pork tapeworm, and the beef tapeworm.