|Internal Parasites – Worms|
This page is based on an episode of The Woof Meow Show which aired on April 26th, 2014. Don Hanson and Kate Dutra talk with Dr. Dave Cloutier from the Veazie Veterinary Clinic about hookworms, whipworms, roundworms, tapeworms and the scariest of all the internal parasites; heartworm. We discuss the importance of protecting your pet and your family from these parasites and the safest and most effective means of accomplishing this protection. You can listen to the show by <clicking here>
Internal parasites that affect our pets may pose a significant problem for our four legged friends and can also be contagious to humans. There are two main types of parasites; those that live in the GI tract and those that live in other parts of the body. When considering worms in the intestinal tracts of dogs and cats, we are usually referring to the following types; hook worms, round worms, whip worms, and tape worms. The other worm we will be discussing is the heartworm, which migrates through the body and into the heart.
While both dogs and cats may host the whipworm parasite, feline whipworms are uncommon in North America. Whipworms are typically contracted through the ingestion of contaminated matter (soil, food, water, feces and animal flesh) and can survive in the environment from months to years. Whipworms may cause significant damage to the intestinal tract resulting in bowel inflammation and bloody diarrhea, or it can also be asymptomatic. It is often associated with dehydration, anemia and weight loss in dogs.
Hookworms are very small and barely visible to the naked eye. They typically attach to the small intestine and feed on blood and tissue fluids from the host animal. The primary concern for hookworms is the development of anemia and weight loss. As with whipworms, hookworms are more prevalent in our canine companions and often result in more damage to our pet’s GI tract.
More commonly known but less harmful internal parasites are the tapeworms and roundworms. Tapeworms are the size of a grain of rice and are often spotted under our pet’s tail, near the anus or in their fecal matter. Several segments can come out together, in which case they look more like a piece of linguine with horizontal lines running through it. Our pets can get tapeworms two different ways; from ingesting prey that has tapeworms, such as a mouse, or from ingesting fleas, which carry the tapeworm egg. If our pet has fleas and they groom or bite at themselves, they may inadvertently ingest the fleas thus becoming infected with tapeworms. While it is rare for humans to get tapeworms, as it requires the ingestion of a flea, it does sometimes occur, primarily in children.
To continue with the food analogies, roundworms look similar to a piece of spaghetti. Tapeworms and roundworms don’t usually cause a lot of weight loss unless your pet is very infected; butt scooting may be a sign if your pet’s anus is irritated by tapeworms. The primary concern for roundworms is the possibility of stunting growth in puppies as the roundworms eat the partially digested food in the intestinal tract. Humans can contract roundworms if the eggs are inadvertently swallowed. Once an animal has a round worm in their body, some of the worms will move from the intestinal tract into muscle tissue where they remain dormant and inactive until the hormone levels change during pregnancy. The newly awakened worms may then transfer into the offspring through the placenta before they are even born or via the mammary glands during nursing.
All of these worms produce microscopic eggs that are shed in your pet’s feces in the litterbox or in your yard. Even if you cleanup after your pet religiously, there will still be some of these eggs in the environment in incredibly large numbers. Roundworms can shed up to 1,000,000 eggs per gram of feces. The FDA estimates that the average dog excretes 0.75lbs of feces per day. That’s 340 grams which means your dog may shed as many as 340 million roundworm eggs per day!
The fact is, in most cases if you took a shovel full of dirt from anywhere in your yard and analyzed it, you would find eggs for these parasitic worms. In almost all cases puppies and kittens are born with worms, which is why they are routinely wormed when you first get them.
Dr. Cloutier recommends that puppies be wormed at 2, 4, 6, 8, 10, 12 and 16 weeks of age to make sure that the worms are “wiped out” and so that your yard does not become contaminated with worm eggs. While no one intentionally ingests worm eggs, if you are playing in the yard, pick up a ball that lands in the grass, and then pickup and eat or drink something, there is an excellent chance you will ingest some worm eggs.
Statistics indicate that 1 in 7 people in the US will show an exposure to roundworms if they are tested. In poorer countries it is estimated that 50% of the population would test positive for roundworms. Since round worms can migrate through the body, they can also cause severe liver damage, blindness and other life threatening problems.
Intestinal worms in our pets are very easy to prevent, if we do it faithfully. A simple once a month treatment can prevent against all types of worms. Why do we need to do this every month? Because our dogs are outside every day, walking barefoot on the ground and picking up things on the ground with their mouth. They’re not only in our backyard, but we take them other places as well; the dog park, Bangor Forest, hiking trails and many other areas where other people take their dogs. All of those places carry parasites in the soil, and more so if some of the dogs that visit there are not on a monthly worm preventative. If you cat is an indoor only cat and you have no other pets, you may want to talk to your veterinarian and see if they believe a monthly worm preventative is necessary.
Heartworm falls into the category of worms that exist outside of the GI tract and is a scary internal parasite. Heartworm can be transmitted across species, including but not limited to dogs, cats and humans. It is transmitted via a mosquito that has become infected when they bit wildlife or a pet that is already infected. An infected mosquito typically deposits about four microfilariae (worm larva) when they bite. Statistically one of those four worms will make it to the heart of our pet where it will grow to be an adult worm, growing to about a foot long and living in the right side of our pet’s heart. The migration to the heart and development into adult heartworms typically takes about six months.
If your pet’s heart has both male and female worms, they will start to reproduce, which then means they can infect mosquitoes that bite them and then those mosquitoes can go on and infect other animals. As the worm population grows it can cause problems in the heart and pulmonary arteries; killing the worms to get rid of them is not a simple matter because of where they are located. The dead worms will pass into our pet’s lungs where they can cause additional problems. While heartworm is usually treatable, it can take several months.
We are seeing more and more heartworm in Maine. In certain areas of the southern United States it is estimated that fifty percent of all animals not on a preventative have heartworm. We currently don’t have that high of an incidence in Maine because many pet parents do use a preventative but also because our climate limits the amount of time mosquitoes are active. However, as well-meaning people and rescue groups bring more dogs up from the South, we bring some dogs into Maine with heartworm.
If no dogs in a neighborhood are carrying heartworm, the percentage of mosquitoes in that community carrying heartworm will be less than 1%. However, if there is a dog that is positive for heartworm in your neighbor’s yard, research suggests that 60% of the mosquitoes in that yard will be carrying heartworm and just a couple houses away, 20% to 30% of the mosquitoes will be carrying heartworm. This is very much a community problem.
If you are adopting a pet from the South, you want to make sure that they are tested for heartworm before they are transported to Maine and again after they have been in Maine for 6 months, and then annually. This is necessary, because there is a period of time where a dog can test negative for heartworm but still have it.
Treating heartworm is a serious issue. It requires a very toxic, arsenic type compound, and your pet needs to be in otherwise good health before being treated. It takes a couple of months to treat and then you must keep your dog quiet for a month during the treatment. It is much easier to prevent heartworm than treat it, so why not just use a preventative?
Heartworm can be prevented by a monthly treatment for both dogs and cats, often with the same treatment you give them for intestinal worms. In Maine, it was typically recommended that a heartworm treatment be given monthly for six months. However, some of the heartworms have become resistant to the preventatives, so manufacturers have had to change their labels to read “Use for six months after the last possible exposure” which effectively means, to be most effective we should be using a heartworm preventative 12 months out of the year even in our cold, frigid state. The heartworm preventatives are very safe, very effective and easy to do. One is even listed as safe for pregnant and lactating animals which suggests a very high degree of safety.
Even indoor cats require protection from heartworm. There is a certain species of mosquito that prefers to get into our homes and also tends to bite cats and carry heartworm. There was a year at the Veazie Veterinary Clinic, probably about ten years ago, where they actually saw more indoor cats test positive for heartworm than dogs.
It should be noted that in the South, in the Mississippi River Valley, there is a type of heartworm that is completely resistant to the heartworm preventatives. Fortunately, it has not moved beyond that area yet.
Although not common, heartworm can be transmitted to people. Since humans are not natural hosts for the heartworm, the heartworm do not fully develop to the full size worms as they do in our pets, but they can pass to the lung and are sometimes mistaken for lung cancer.