Aside from the itchy nuisance brought by fleas and ticks, dogs are also susceptible to a variety of intestinal parasites or worms. There are tapeworms, roundworms, hookworms, and whipworms as well as other types of intestinal worms. The unfortunate thing is that we don’t always see these worms as they invade the bodies of our beloved pets. We are only alerted to their presence when our dogs are already showing some of the classic symptoms of helminthic infections. That said, it is best that we increase our knowledge as to what causes worms in dogs and how best these can be treated and prevented.
Types and Causes of Worm Infestations in Dogs
There are thousands of species of worms of intestinal nature affecting pets, especially dogs. However, four of the most common ones include tapeworms, hookworms, roundworms, and whipworms. Our knowledge of these types of worms will help us better understand what causes such infections in our canine friends.
Tapeworms are transmitted to dogs by fleas. These parasites live inside fleas. When your dog accidentally ingests tapeworm-infested fleas during grooming, it breaks down the fleas and releases these parasites into its gut where they will grow into full-blown adult tapeworms. Once these tapeworms reach reproductive maturity, they start laying eggs or proglottids that eventually become larvae. These small tapeworm larvae eventually break off and are passed down with the stools. Since adult fleas and larvae rely on organic matter to grow, they feed on these tapeworm-infested feces, ingesting the tapeworm in the process.
There are numerous tapeworms that can infect dogs, but the really common ones include Dipylidium caninum, Taenia taeniaformis, Echinococcus granulosus, Echonococcus multiocularis, Taenia serialis, and Taenia pisiformis as well as the broad fish tapeworm, Diphyllobothrium latum. The important thing to remember is that, as the name suggests, tapeworms are flat worms that come in segments resembling a tape measure. Each of these segments or ‘glottids’ is fully capable of reproduction. Tapeworms are also some of the longest worms you’ll ever see; they can grow up to 6 inches long inside your dog’s gut.
Two of the most clinically-important roundworms in dogs are Toxocara canis and Toxascaris leonina. These are the canine equivalents to the Ascaris lumbricoides species that typically affects children. Roundworms can grow up to 5 inches long and are typically described by their physical appearance as resembling spaghetti noodles.
Roundworms can be transmitted in various ways. Adult roundworms are very prolific, fully capable of reproducing up to 200,000 eggs every single day. Each of these eggs is covered in a protective hard shell known as cyst, allowing them to thrive for many years. Many of these eggs are shed in the stool. When another dog eats something that has been contaminated with this roundworm-filled stool, it also ingests the eggs. These eggs hatch in the dog’s gut where some of them can migrate into the dog’s lungs. From there they can get coughed up only to be taken up again by another dog. If the dog is currently pregnant at the time of tapeworm infection, some of these tapeworms are transmitted to the growing puppies. So you can get puppies that are born with tapeworms already growing inside them.
Ancylostoma caninum and Ancylostoma, braziliense are the two most common hookworms known to infect dogs. Hookworms reside in the dog’s gut, especially the small intestines feeding off the blood supplying this region. Eggs are passed in the stool where they hatch into larvae. Hookworm larvae are excellent swimmers and can hide in raindrops and dewdrops hanging on vegetation and leaves.
It is this stage of the hookworm that makes its way into another dog’s body through a variety of ways. First, larvae can penetrate a dog’s skin when it steps on soil that contains the larvae, burrowing through the dog’s skin. If the dog drinks or even licks contaminated water or soil, it also introduces hookworms into its body. Larvae can also migrate to the dog’s mammary glands and get ingested by nursing puppies. These parasites are also known to cross the placenta and infect unborn puppies in pregnant dogs.
Growing only up to about a quarter of an inch long, whipworms are one of the smallest intestinal worms known to affect dogs. Trichuris vulpis is the most common and it’s known to live in the dog’s cecum, the very first section of the dog’s large intestines. Vets consider whipworms to be highly pathogenic as they can cause bloody, rice-watery diarrhea.
Whipworm eggs are microscopic. They are passed in the dog’s stool and are exceptionally resistant against heat and drying. Whipworm eggs can remain viable in the external environment for as long as 5 years. These eggs mature into the infective stage of whipworms and can get swallowed by dogs ingesting contaminated materials.
Signs and Symptoms of Worm Infestations in Dogs
Spotting worm infections in dogs can be tricky since many of the clinical manifestations are shared across organisms. These can include the following:
Roundworms and hookworms are known to travel to the lungs where they can get expectorated. Coughing is thus considered a defense mechanism that works by expelling these unwanted organisms in the pulmonary tree. While not all worms will cause coughing, this manifestation is always often considered as a sign of a serious worm infestation. Since intestinal worms are generally confined in the dog’s gut, having respiratory symptoms can mean trouble.
- Soft or watery stools
Whipworms have this uncanny ability to cause massive loss of fluids and electrolytes in the stool. Because whipworms reside in the region of the dog’s gut where water reabsorption takes place, rice-watery diarrhea occurs because not enough water is reabsorbed back into the system. Additionally, the whipworms latching onto the intestinal walls perforate the walls causing blood to leak out and producing bloody diarrhoea.
Most experts don’t look at vomiting as essentially bad. It is a defense mechanism whereby the dog is trying to get rid of the worms that are present in its digestive tract. In some cases, you might even see roundworms in the vomitus. Vomiting can be caused by the growing bolus of worms in the dog’s intestines, causing the gut to expand. This leads to an increase in the pressure inside the gut forcing gastric contents out.
- Decreased energy
Regardless of the type of worm infecting your pet, one of the most important manifestations is decreased energy. This is due to the fact that the calories and nutrients that are supposed to be used by the dog are now used up by these worms. In other words, your dog doesn’t have enough calories left to burn as energy. Whipworms also cause bloody diarrhea, leading to anemia which can further reduce the dog’s energy levels.
- Weight loss
Whipworm and tapeworm infections in dogs are known to produce massive weight loss. This is especially true for whipworms as they tend to produce copious watery, bloody diarrhea. Weight loss can also be due to the loss of nutrients and calories that are now being used by the intestinal worms.
- Changes in appetite
Dogs that are infected with roundworms typically lose their appetite, leading to a reduction in food consumption. Over time, however, this loss of appetite gradually makes way for increased appetite in an effort to compensate for the loss of nutrients that are now being consumed by these worms.
- Pot-bellied appearance
Roundworms and hookworms are especially notorious for producing a pot-bellied appearance especially in young puppies. Tapeworms that have grown and have already formed a large ball of parasitic mass inside the gut can also produce pot-bellied appearance in dogs.
- Itching and other signs of irritation on the skin
Hookworms get transmitted by burrowing through the skin of the dog. This can cause inflammatory reactions leading to itching as well as other signs of skin irritation. Other worms also tend to invade skin tissues.
- Dull coat
This is often the result of malnutrition caused by intestinal worms utilizing the nutrients that are supposed to be distributed to the dog’s cells and tissues.
- Frequent rubbing of its bottom or ‘scooting’
Some worms tend to migrate through the anal canal. The gravid segments of tapeworms are known to ‘crawl’ up the dog’s anus in an attempt to get back into the system. Some roundworms and whipworms are also known for such behavior. These produce itching in your dog’s bottom. Unfortunately, your pet cannot scratch its behind so it rubs it or go on a ‘scooting’ behavior.
- Worms in the stool or on dog’s fur
Larger worms can be readily seen in the dog’s stool. For example, roundworms are typically passed in dogs’ feces. So you can actually see these worms squirming like mad in your pet’s stool. As for tapeworms, you won’t see entire worms in the stool. Instead, you may see broken off segments or glottids which can be very tricky to spot. You can also see adult hookworms in dogs’ stools.
Treatment of Worms in Dogs
Treating intestinal parasitism in dogs can be especially challenging since the different species of helminthes respond differently to certain anthelminthic medications. Some of the life stages of these parasites are also heavily protected by cysts, making it virtually impossible to kill them. As such it is important to choose the right kind of dewormer or anthelminthic agent that is appropriate for the kind of intestinal worm in your dog.
For example, when it comes to roundworms, whipworms, and hookworms, dewormers that contain febantel, fenbendazole, and other benzimidazoles are generally effective. However, pyrantel pamoate has also been extensively used in the control and management of roundworms and hookworms. As for tapeworms, the dewormers of choice are those that contain praziquantel. Recent developments in anthelminthic preparations have shown that Milbemycin oxime can help control the 4 different types of intestinal parasites affecting dogs.
It is also important to understand that these drugs kill only certain life stages of the parasite. Generally, they only kill the adult worms that are currently present inside the dog’s intestines. Many of these drugs don’t have any effect on encysted roundworm larvae. Also, tapeworms are generally resistant against many types of medications, although praziquantel has been shown to be the most effective.
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Prevention of Worms in Dogs
Since roundworms and hookworms can be passed onto unborn puppies, one should always look at them as potentially having the intestinal worms. As such experts recommend treating all puppies with a broad-spectrum anthelminthic or dewormer at the age of 2, 4, 6, and 8 weeks. This dosing should then be continued every 3-6 months before being adjusted accordingly by your vet. However, it is important to realize that different products will come with different dosage schedule recommendations. It is, therefore imperative that these be considered.
The prevention of intestinal parasitism in dogs requires vigilance on the part of pet parents. Because these worms are passed in the stool, care should be taken not to expose our dogs to such conditions whenever they go outside the house. This can be difficult since there really is no way of telling if the soil upon which your dog is standing on is not already contaminated with the larvae of these worms. Moreover, these larvae are so hardy that conventional heat and chemicals cannot readily kill them.
For tapeworm infections, since these are mostly carried by fleas, protecting your dog with regular effective flea treatments should help in the prevention of such infections. Understand, however, that your dog can still lick dead fleas while it is grooming itself and this can still lead to the release of the tapeworm in its gut.
It is for this reason that regular deworming is still one of the most effective ways of preventing and controlling intestinal parasitism in dogs.
Worms in your dog’s poop can bring a lot of implications to your dog’s overall health. Knowing what causes the infestation and how best to manage them can help better care for your pet. This also paves the way for a generally worm-free lifestyle for your dog.
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- Dr. Hector Joy, How to Get Rid of Worms in Dogs – PetMD
- Worms in Dogs: Diagnosis, Prevention, and Treatment – The American Kennel Club
- Dr. Leslie Gillette, What to Do When Your Dog Has Worms – PetMD
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.