A potential health concern with owning a dog is intestinal parasites, specifically, worms. You may discover your dog has a problem by noticing worms in his poop. Even more concerning is that some of the worms that infect dogs can be transmitted to humans. There are several types of worms that can inhabit your dog’s intestinal tract; the most common are hookworms, roundworms, tapeworms, and whipworms. This article will cover each of those types of worms, how your dog can become infected with them, signs and symptoms of infection, how to treat them, and what you can do to prevent your dog (and you!) from getting them.
- Hookworm life cycle
- Signs and symptoms of hookworm infection
- Diagnosis of hookworm infection
- Treatment of hookworm infection
- Prevention of hookworm infection
- Hookworms in humans
- Roundworm life cycle
- Signs and symptoms of roundworm infection
- Diagnosis of roundworm infection
- Treatment of roundworm infection
- Prevention of roundworm infection
- Roundworms in humans
- Tapeworm life cycle
- Signs and symptoms of tapeworm infection
- Diagnosis of tapeworm infection
- Treatment of tapeworm infection
- Prevention of tapeworm infection
- Whipworm life cycle
- Signs and symptoms of whipworm infection
- Diagnosis of whipworm infection
- Treatment of whipworm infection
- Prevention of whipworm infection
- How to keep your dog safe from intestinal worms
Hookworms get their name because of the hook-like mouth parts that they use to attach themselves to the lining of the small intestine of dogs. Immature and adult worms attach to the lining of the small intestine, digest the tissue, inject anticoagulants (enzymes that prevent blood clotting), and suck blood. They do occasionally move from one site to another within the intestine, leaving behind small bleeding ulcers at their previous sites of attachment.
There are three species of hookworms that can infect dogs in the United States: Ancylostoma braziliense, Uncinaria stenocephala, and Ancylostoma caninum. A. caninum is the most common and has a fairly wide distribution across the south central and southeastern regions of the United States.
Hookworm life cycle
Adult hookworms are up to about a half inch in length and live 4-24 months firmly attached to the lining of the small intestine. About two to three weeks after attaching to the intestine, they begin producing and shedding eggs, which are passed into the environment through the dog’s stool. Once outside the dog’s body, the eggs hatch and mature into infective larvae. In warm, moist soil, this can occur within two to three days, but may take as long as nine days in less favorable conditions. The larvae can then remain in the environment for weeks or even a few months in warmer temperatures.
The dog can then become infected with the larvae by inadvertently eating something from the environment (such as by grooming a part of their body that has come in contact with the contaminated ground), sniffing at feces from an infected dog, eating another animal that is infected, or by larval penetration of the skin. If ingested, the larvae will then mature into adults and attach to the lining of the small intestine. Larvae that penetrate the skin of puppies will enter the bloodstream and migrate to the lungs where they are coughed up and swallowed by the dog. In dogs that are older than about three months of age, the larvae will still travel to the lungs, but from there, they will embed themselves in other tissues of the body and become dormant.
When a previously infected dog becomes pregnant, those dormant hookworm larvae will become active again and accumulate in the mammary glands. When puppies nurse, the larvae are able to pass from the mother to the puppies and thereby infect the puppies. Dormant larvae may also become active when the adult worms are killed off by treatment, thus making it extremely difficult to get rid of a hookworm infection.
Signs and symptoms of hookworm infection
The signs of a hookworm infection are different depending on the age of the affected dog. The infection is most dangerous in puppies that became infected by nursing. The most common hookworm is a particularly voracious bloodsucker and can actually bleed a puppy to death. Signs to look for in puppies include failure to thrive and gain weight, poor quality coat, pale gums, lethargy, and dark, tarry diarrhea.
In otherwise healthy mature dogs, the main clinical sign is diarrhea.
In dogs who have been infected by larval penetration of the skin, occasionally a skin irritation develops, especially on the dog’s feet and between their toes. The skin will be reddened, itchy, and have small raised bumps.
Diagnosis of hookworm infection
Most of the time, diagnosis of hookworm infection is done by examining the feces of the dog with the suspected infection, and can often be done in-house at your veterinarian’s office. If your veterinarian is not set up to perform fecal examinations, then the sample is sent off to an outside laboratory and results are back within 24 hours. The most common method of fecal examination includes taking a small sample of fresh fecal material, mixing it into a salt solution in a large test tube, and then spinning the sample down in a centrifuge. The fecal material will be pushed to the bottom of the test tube while any hookworm eggs that are present will float to the top. A microscope slide coverslip is placed on top of the tube so that it touches the salt solution, and any eggs at the surface will stick to the coverslip. The coverslip is then placed on a slide and examined under a microscope and any eggs are identified.
However, puppies often show signs of being infected even before they start shedding eggs in their feces since there is a 2-3 week delay between infection and egg shedding. So in puppies, one of the main diagnostic findings is anemia, which is a decrease in the amount of red blood cells in the bloodstream. A small blood sample is taken and run through a machine that identifies and counts all of the cellular components of the blood; the test is called a CBC, or complete blood count. This test is able to be done by your veterinarian, and results are often obtained within minutes.
Treatment of hookworm infection
Generally, a hookworm infection is treated by giving an oral dewormer such as fenbendazole or pyrantel. The dewormers only kill adult worms, however, so the medication must be repeated two to four weeks after the initial dose in order to kill any adult worms that were larvae at the time of the first dose. The dewormers are safe, and have few, if any, side effects. The most common side effects include a decreased appetite, mild lethargy, and diarrhea, but these are rarely observed.
For more severely affected dogs and especially severely affected puppies, hospitalization with supportive care may be required to keep the dog alive until the dewormer can take effect. Supportive care can include heat support, intravenous fluid therapy, iron supplementation, a high protein diet, and if the dog or puppy is severely anemic, a blood transfusion.
Recently, multi-drug resistant strains of hookworms have developed in the racing greyhound due to overly frequent deworming and the turnout pens at the farms and racing kennels in the southeastern United States providing an excellent environment for the infective larvae. Many greyhounds entering adoption groups are positive for hookworms despite all efforts, and those strains are starting to be seen in the rest of the pet population. They can be very difficult to get rid of, and usually require the use of multiple drugs for extended periods of time along with strict clean-up of the environment. Anecdotally, long-term use of [Advantage Multi] is working well to control hookworm infections in many retired racing greyhounds.
Prevention of hookworm infection
Dewormers should be administered routinely; most monthly heartworm preventatives also include a dewormer. Pregnant dogs should be dewormed shortly before giving birth and every two weeks after giving birth until the puppies are completely weaned; after that, the mother can be put back on her regular parasite preventative. Puppies should be dewormed every two weeks until 8 weeks of age, and then put on a monthly heartworm preventative that includes a dewormer.
Keeping the environment clean is vitally important – feces should be picked up immediately, before the eggs can hatch and produce infective larvae. Dogs should also be prevented from eating potentially infected animals (usually rodents) and kept away from environments that are contaminated with the feces of potentially infected dogs. Many veterinarians recommend a fecal examination at least once yearly, usually done as part of the dog’s annual physical exam – this will help monitor for any infections that don’t cause significant symptoms.
Hookworms in humans
Hookworms are considered a zoonotic disease, which means that humans can become infected with canine hookworms. Usually this happens when walking through a contaminated environment with bare feet, or by playing in a sandbox that has been used for elimination by a dog. The hookworm larvae will burrow into and migrate under the skin, causing an intensely itchy serpentine lesion. This condition is called cutaneous larva migrans. The larvae of canine hookworms are unable to mature in humans, but may become embedded in muscle tissue and become dormant. Hookworms in humans can be treated with dewormers that are safe for humans (don’t use your dog’s deworming medication!).
Prevention of transmission to humans include promptly picking up any dog stool, deworming your dog routinely, covering childrens’ sandboxes when not in use, wearing shoes and gloves while gardening, and using a blanket or chair while sunbathing on the beach.
Roundworms live freely in the intestines of dogs, eating the partially digested food that is making its way through the intestines. They are called roundworms because they are tubular in shape. There are two species of roundworms found in dogs: Toxocara canis and Toxascaris leonina; of the two, Toxocara canis causes more significant disease and may also be transmitted to humans. Roundworms are the most common intestinal worm found in dogs.
Roundworm life cycle
The roundworm life cycle is a bit complicated and there are multiple ways in which dogs can become infected. Dogs with an active infection will shed roundworm eggs in their feces. Dogs then become infected by sniffing at, licking, or eating infected feces. After that, the ingested eggs will go through several stages of development, moving through the liver and lungs. Once in the lungs, the roundworm larvae are coughed up and swallowed, and will then fully develop into adults in the small intestine. However, this portion of the life cycle generally only occurs in puppies less than six months of age, before their immune system is completely developed. Once the immune system is developed, the roundworm larvae will usually migrate into the dog’s tissues and encase themselves in a cyst and lie dormant until activated. Thus, adult dogs rarely have an active case of roundworm infection. Triggers for activation include going into heat, becoming pregnant, or developing an immune system disorder.
If a dog were to become pregnant, the dormant cysts from a previous infection of the mother are activated and the developing roundworms can actually cross the placenta and enter the unborn puppies. Thus the puppies can be born already infected with roundworms, and active adult worms may be seen in the puppies’ intestines as early as a week after birth, and eggs can be passed in the puppies’ stool as early as 11 days after birth. Roundworm larvae can also be passed into the puppies via the mother’s milk, and the mother will also start passing large numbers of eggs in her own feces. Therefore, it’s quite possible for puppies to develop a large load of roundworms through multiple methods of infection.
Other animals, such as rodents and birds, can also become infected with roundworm larvae, but since they are not the desired host for dog roundworm, the larvae build themselves a cyst within the animal’s muscle tissue and lay dormant until eaten by a dog. Once the dog eats the infected prey animal, the larvae in the prey’s muscle tissue come out of dormancy and develop into adults in the dog’s small intestine.
Signs and symptoms of roundworm infection
Puppies are much more likely to show signs of infection versus adults, since their immune system is not developed enough to prevent development of the larvae into adults. Because the adult worms are feeding off the food that the puppy is eating, the puppy will not be getting enough nutrients and therefore have stunted growth and poor haircoat. Puppies may have a “pot-bellied” appearance and vomit up worms or pass them in their feces. As the roundworm larvae make their way to the lungs, puppies may develop pneumonia and therefore coughing. Puppies may also have diarrhea with mucus. Some puppies with a very heavy roundworm load acquired before birth may actually die suddenly a few days after birth due to the large numbers of developing larvae crossing into the lungs.
In adults, since the vast majority of roundworm larvae become encysted in the muscle tissue and only a few actually develop to maturity in the small intestine, there is usually no sign of infection. Very occasionally, a mild diarrhea may be noted.
Diagnosis of roundworm infection
Roundworms are diagnosed using fecal analysis – examining the fecal material under a microscope after separating the eggs from the rest of the fecal material using a centrifuge. Roundworms are also fairly easy to identify in the vomitus – they are fairly large (4-5 inches in length), light tan to white in color and resemble cooked spaghetti noodles. Fecal antigen tests are also available – these laboratory tests detect the presence of proteins produced by adult roundworms. These tests are particularly helpful when not enough eggs are being produced to be seen in the routine fecal analysis.
Treatment of roundworm infection
Roundworms are treated with oral dewormers such as fenbendazole, milbemycin, moxidectin, or pyrantel; pyrantel comes in a liquid formulation that may be more easily administered to puppies.
Prevention of roundworm infection
Routine deworming using one of the combination heartworm/intestinal parasite preventatives will help keep roundworms at bay. Pregnant dogs should be dewormed shortly before giving birth, then dewormed again every time the puppies are dewormed. Puppies should be dewormed every two weeks until they are able to be placed on a monthly parasite preventative.
The environment should also be kept clean by promptly picking up feces. Dogs should be prevented from eating prey animals, especially rodents, who are potential carriers of the roundworm larvae. Children’s sandboxes should be covered when they are not in use. Once the environment is contaminated, the eggs are nearly impossible to get rid of, and they can remain infective for years. Generally, the only way to rid the environment of roundworm eggs is to pave over the surface with asphalt or concrete, completely remove the topsoil, perform a prescribed burn, or treat the entire area with steam. Thus it is vitally important to promptly pick up feces and keep your dog on a routine dewormer.
Roundworms in humans
Roundworm infection in humans is called toxocariasis. Infection is most likely to occur in children, and happens when children play in a contaminated environment and eat the dirt from that environment. When the eggs are ingested, they migrate through the tissues and can cause a variety of conditions, including liver enlargement, lung disease, progressive neurologic disease, eye inflammation, or chronic abdominal pain. Treatment for most of the signs is with a dewormer meant for humans; treatment of infected eyes is more difficult and is geared towards preventing further damage.
Children should be prevented from playing in areas where dog feces are present, prevented from eating dirt, and taught to carefully wash their hands after playing outside and before eating.
Tapeworms are long, flat, segmented worms that inhabit the small intestine. They use their hooked mouth parts to attach to the lining of the small intestine and absorb the nutrients in the intestine as the nutrients pass through the intestine. There are many different species of tapeworm that can infect dogs, but the Dipylidium caninum is the most common.
Tapeworm life cycle
As the tapeworms mature and grow (up to 11 inches in length!), individual segments, called proglottids, detach from the rest of the worm and are passed in the feces. The segments are about a half inch long and resemble grains of rice or cucumber seeds. As they dry out, they become a more golden color and eventually split open, releasing up to 20 fertilized eggs into the environment. The eggs are then eaten by a flea larva, and the egg continues to develop as the flea larva matures into an adult. The flea is then eaten by the dog as it grooms itself, and as the flea is digested by the dog’s gastrointestinal tract, the egg is released. It hatches and attaches to the lining of the small intestine and from there, grows into an adult.
Signs and symptoms of tapeworm infection
Tapeworms generally do not cause serious disease in dogs, but the degree of illness depends on such factors as the degree of infection, age, and overall condition of the dog. Signs, if present, will range from irritation around the anus, lethargy, failure to grow normally, variable appetite, and mild diarrhea. If enough tapeworms are present, particularly in a puppy, it is possible for them to cause a blockage of the intestine, severe weight loss, and perhaps even seizures. Usually owners are not aware their dog is infected until they see the tapeworm segments in the feces or moving around their dog’s anus.
Diagnosis of tapeworm infection
Diagnosis is usually done by observing the tapeworm segments in the feces or around the dog’s anus. It is possible to find the eggs by fecal analysis, but observation of the segments is the far more common way to diagnose the infection.
Treatment of tapeworm infection
Praziquantel is the dewormer of choice for tapeworm infection, which can be given orally or by injection under the skin. Treatment of tapeworm must also be combined with appropriate flea control or else the dog is likely to be reinfected.
Prevention of tapeworm infection
Since dogs get tapeworm infections by eating infected fleas, flea control is of vital importance to preventing tapeworm infections. There are many safe and effective flea control products out there, such as the Seresto collar (Check Price on Amazon), topicals such as K9 Advantix II (Check Price on Amazon), Vectra 3D (Check Price on Amazon), or Frontline Plus (Check Price on Amazon), or prescribe an oral medication such as NexGard, Simparica, or Bravecto. Dogs that frequently eat prey animals that may be flea-infested should be on a monthly heartworm preventative that includes praziquantel, such as Sentinel Spectrum, Interceptor Plus, or Iverhart Max for ongoing protection.
Whipworms are named for their characteristic whip-shaped body, consisting of a shorter, thicker end (the whip handle) and a longer, thinner section near the head (the whip). Whipworms embed themselves in the lining of an intestinal structure called the cecum, which is a pouch at the beginning of the large intestine, and feed upon the partially digested food that flows by. The species of whipworm that infects dogs is called Trichuris vulpis.
Whipworm life cycle
Adult whipworms shed eggs in the feces. The eggs become viable and infective in 9-21 days, depending on the temperature and humidity of the soil. The eggs are extremely resistant to drying out, extremes in temperature, and UV radiation, and can remain viable for years. Dogs become infected by eating soil in which the eggs are present. Once ingested, the eggs develop into larvae, which then penetrate the lining of the small intestine for 2-10 days before moving to the cecum where they will develop into adult worms.
Signs and symptoms of whipworm infection
Dogs rarely show any signs of a mild whipworm infection. When the worm burden becomes heavier, then infected dogs start to show weight loss, bloody diarrhea, dehydration, and possibly even anemia (reduced red blood cell count).
Diagnosis of whipworm infection
Whipworms are diagnosed by fecal analysis. However, adult worms don’t produce eggs for about 11 weeks after infection, so it is possible that an early infection will be missed by fecal analysis because the eggs aren’t being produced at that time. Whipworms also pass fairly small numbers of eggs on an inconsistent basis, so often serial fecal analyses are necessary to find the whipworm eggs. Some veterinarians will administer a dewormer for dogs with chronic diarrhea without an actual diagnosis; if the dog improves after the dewormer, it indicates whipworms were present but unable to be detected in the fecal sample.
Treatment of whipworm infection
Dewormers such as febantel or fenbendazole are used to treat whipworm infections; monthly heartworm preventatives that use moxidectin or milbemycin can also be used to treat and control whipworm infections. Treatment should be repeated at least one more time about a month after the initial dose in order to kill all of the worms as they develop into adults.
Prevention of whipworm infection
Since whipworm eggs are extremely hardy, it is quite easy for dogs to reinfect themselves, so dogs should be maintained on a monthly parasite preventative that is effective against whipworms. Feces should also be picked up promptly, before the eggs have a chance to develop into the infective stage.
How to keep your dog safe from intestinal worms
While the thought of worms living in your dog’s intestines can be a bit scary, there is a lot that you can do as a dog owner to help keep your dog safe from these parasites. In consultation with your veterinarian, you should pick a deworming protocol that works for you and your dog. Many monthly heartworm preventatives have deworming medications included that cover most or all of the intestinal worms discussed above; this is perhaps the easiest option to make sure your dog is covered. Other heartworm preventatives don’t have the intestinal worm coverage, so a separate deworming schedule may be necessary. Be sure to discuss all the options with your veterinarian.
The other key step in protecting your dog from intestinal worms is keeping your dog’s environment clean. Promptly pick up and dispose of feces before any eggs have a chance to mature into the infective stage. Keep your dog away from areas that are potentially contaminated with feces from untreated dogs. With a combination of routine deworming and a clean environment, the risk of infection is much less, and be sure to have a fecal analysis done at least once yearly to monitor for any asymptomatic infections.
Pets and Parasites: http://www.petsandparasites.org/dog-owners/roundworms/
Common Canine Worms and Intestinal Parasites: https://www.thespruce.com/common-canine-intestinal-parasites-1117426
Worms in Dogs: https://www.dogbreedinfo.com/worms.htm
Symptoms of Worms in Dogs: https://www.cesarsway.com/dog-care/other-worms/symptoms-of-worms-in-dogs