How Do Dogs Get Worms -

How Do Dogs Get Worms?

It’s not a fun subject to talk about but it happens fairly frequently. You notice your dog scratching his rear end a lot, maybe scooting across the floor, and you naturally wonder if he has worms?


The most common means by which dogs get worms is from inadvertently eating their eggs in contaminated soil, stool, fleas, water, or rodents. Some worms can be transmitted through the skin or through a mosquito bite. Others are transferred to puppies from their mother or even from spores floating in the air.


Some parasitic diseases from worms are zoonotic, which means they can affect both humans and dogs and can be transferred from one species to another. Children are most susceptible to contracting these diseases as they tend to be in closer proximity with dogs and don’t always practice the best hygiene habits.


Fortunately, there are preventative medicines available for some of these diseases and most of the others are easy to diagnose and treat.


In this article we will be looking at the cause, symptoms, diagnosis, treatment, and prevention of the 6 most common parasitic infections for dogs and one common fungal infection:

  • Roundworm
  • Hookworm
  • Whipworm
  • Tapeworm
  • Heartworm
  • Giardia
  • Ringworm



Roundworm is the most common worm found in dogs. You may see these in your dog’s feces or vomit. These worms are white or light brown, look like spaghetti segments, and can grow to be a few inches long and. Roundworms are often passed from the mother to her puppies through the placenta before they are even born. They can also be transmitted through the mother’s milk. This is possible even if the mother has been dewormed.


They can be transmitted to adult dogs through eating soil or stool that has been contaminated by an infected dog, and occasionally by eating an infected rodent. After the dog ingests the eggs, they hatch inside the dog and turn into larvae. The larvae spread to the liver and into the windpipe. Once they are in the windpipe the dog coughs up the larvae and then swallows them into his intestinal area. They live in the intestines feeding off of them and the food the dog eats. Here they grow and lay their own eggs.


There are symptoms you can look for to help determine if your dog has roundworms. Your dog could possibly have a rough-feeling coat, bad breath, diarrhea, vomiting, or a potbelly. Another symptom is that the dog seems lethargic, having less energy than normal. Roundworms can be very dangerous to puppies and if untreated can even lead to death. However, in most adult dogs, they usually aren’t very harmful.


Roundworm is easy for your vet to diagnose by observing a fecal sample on a microscope slide. Once diagnosed, treatment is easy. There are several safe and effective deworming drugs. Puppies can start deworming treatments as early as 2 weeks old. An infected puppy should be treated at 2, 4, 6 and 8 weeks of age, or until there are no longer signs of eggs in its stool. Sometimes a follow-up dose will need to be administered for eggs that have matured after the first treatments were done.


It’s hard to completely prevent roundworm. However, it is helpful to keep your yard regularly cleared of dog droppings. Also try to prevent your dog from eating any wild animals that may be contaminated.


Keep in mind that you can get roundworms from your dog. If he has been cleaning his anal area and then licks you, he can transfer microscopic eggs onto you. If you happen to touch your mouth you can then accidentally ingest these eggs. The eggs will then make their way into your intestine and grow. You may notice long, spaghetti-like worms in your stool. If this happens, please contact your doctor. There are medications that can take care of it quickly.



Hookworms tend to be more abundant in warmer climates. They are quite small, usually only ⅛-¾ inches long. They have hook-like teeth that they use to attach to the intestinal wall.


Dogs can become infected with hookworms by ingesting the microscopic larvae by mouth or through the skin, usually through the pads on their feet. If they pick up the larvae in their fur they can also ingest them while they are cleaning themselves. Hookworm larvae can also be transmitted to puppies from their mothers through the placenta or through the mother’s milk.


If your dog has hookworms he will probably look unhealthy and have a poor appetite. He may be having intestinal distress and you may see blood in his stools. The linings of his nostrils, lips and ears may also be pale, and he may become anemic.


Even though they are small, hookworms can ingest enormous amounts of blood from your dog. The adult female hookworm can produce up to 20,000 eggs a day. If infected, your dog will become weak and malnourished. This can lead to death in weaker dogs and puppies.


Hookworms are easily detected by your vet through a microscopic examination of the stool.

There are oral and injectable medications to treat your dog for hookworms. Your dog will often require a second treatment in 2-4 weeks to make sure all of the worms are killed. Your dog may also need iron or nutritional supplements to help him recover from this parasite. In addition to these measures, you will need to treat your dog’s environment. Make sure feces are cleaned up and vacuum your house regularly and thoroughly.


Some heartworm preventatives contain a drug that will help prevent hookworms as well. However, keep in mind that this won’t kill any adult hookworms that are already present in your dog’s system. He must be treated for existing hookworms first before the heartworm medication will help prevent him from getting them again.


Adult hookworms do not infect humans. However, the larvae can burrow into human skin. This can cause a rash and strong itchiness at the site of entry. Humans can get hookworms by walking barefoot in contaminated sand or soil as well as from unwashed vegetables. The larvae will not mature into adults but they can still cause weight loss, diarrhea and sometimes anemia. Like roundworms, hookworms can be easily treated in humans.



Whipworms are a common parasite throughout North America. They are usually about 2-3 inches in length. They are tapered at one end like a whip.


Whipworms can affect dogs of all ages. Once a dog is infected, the female whipworm produces eggs that are shed in the dog’s stool. The eggs can be found in soil, food, water, feces, or even in animal flesh. These eggs can survive in the soil for up to 5 years waiting to infect any dog that comes along.


Whipworms attach to the mucous membrane in the large intestine and the cecum, a pouch located where the large and small intestines meet. They get their nourishment by stabbing through the intestine and sucking blood and fluids from their hosts.


If your dog is infected with whipworms he may become dehydrated, anemic, and show signs of pain. He may also have a significant loss in weight as well as bouts of smelly diarrhea. Conversely, some dogs show no signs at all when infected by hookworms.


Your vet can test for whipworms by doing a fecal flotation procedure. If parasitic eggs or adult whipworms are present, they will float to the surface on the microscope slide.


There is an effective oral dewormer that can be given to your dog to get rid of the infection. However, they can be reinfected. Since the eggs can live so long in the soil, whipworms can be hard to get rid of. There is no effective way to kill them in the soil and the eggs have proven resistant to most cleaning methods. The best thing to do is to clean up the feces in your yard daily. Also, there are some heartworm preventatives that are also effective against whipworms.


Thankfully, whipworms do not infect humans.



Tapeworms are a fairly common infection in dogs. Whole tapeworms are flat and can be up to 6 inches long. You will usually only see smaller segments that are off-white, ¼- to ½-inch long, and may expand and contract. If there are dead segments they will be darker in color and will look like pieces of rice or seeds. You may see these in the feces or in the fur around the anus.


Tapeworms are transmitted through infected fleas and sometimes through infected lice. The dog ingests these when he is cleaning himself or sometimes when licking or eating infected feces. They can be passed from pet to pet but not directly. An infected flea from one pet can infect another.


The main signs of a tapeworm are rice-like segments in the feces and/or clinging to the fur around the anus. When our dog, Trooper, had tapeworms we also found the darker rice-like segments inside our bathtub after bathing him. Tapeworms absorb some nutrients from your pet while living inside his intestine, but are typically not very harmful to your dog.


Tapeworms are very easily treated with an injection or tablet from your vet. When our dog, Trooper, had tapeworms he had to take 2 pills several weeks apart to make sure all of the adult tapeworms were eliminated.


While humans can contract tapeworms, it is very rare to get them from an infected pet. A person would have to swallow an infected flea. Make sure you don’t walk barefoot in the area your dog relieves himself and wash your hands after petting your dog.



Heartworms are found in dogs in all 50 states. These parasites can be 12-14 inches in length and can live 5-7 years.


Heartworms are transferred from one dog to another by mosquitos. When a mosquito bites an infected dog and ingests his blood he sucks up the small, immature heartworms called microfilariae. These immature worms develop into larvae inside the mosquitos. Once they become larvae they can then be transferred to any other dog that mosquito happens to bite. It only takes one bite for the dog to become infected.


Although it is transferred from one animal to another there does need to be an incubation period while inside the mosquito before the parasite can be passed on. Because of this, it is not likely for one pet to infect another in the same house.


Once inside the dog, it can take 6-7 months for the larvae to mature. One dog can end up with up to 250 worms in his system. Heartworms live and feed in the right side of the heart and in the connecting arteries and vessels. They affect how the heart functions and may cause blood clots in the pulmonary artery, the artery carrying blood from the right ventricle of the heart to the lungs. Heartworms can cause cardiovascular weakness and can also hinder lung capacity. This can lead to organ failure and even death.


Many dogs don’t show any symptoms until the disease is advanced. The first sign is usually a cough. The dog also tends to become winded easily and less active. He may even collapse.


Vets can test for heartworm by taking a small blood sample and testing it for specific proteins caused by heartworms.


Heartworm treatment is quite expensive and very hard on the pet. First, your vet needs to do a complete work up on the dog to determine how widespread the infestation is. Once that is complete there are only a few options and all are injectable. Some of these treatments are arsenic-based. The dog will be given 2-3 injections in order to kill the heartworms in the blood vessels. The whole treatment can end up costing up to $1000 or more.


For up to 2 months after the treatment you have to keep your dog very calm, maybe even on crate rest. The reason for this is that as the heartworms begin to die they break into pieces. These pieces will then float through the arteries and pulmonary vessels. If the dog becomes active the pieces can clump together and cause blockages which can lead to death. Once there are no more signs of these pieces, the dog can return to normal activity. However, your dog can be reinfected if bitten by another infected mosquito.


While treatment is expensive and very hard on your dog, prevention is easy. There are many preventatives available that your vet can provide. Some of them also help prevent other parasites mentioned earlier in this article. There are monthly topicals or pills available as well as a 6-month injectable.


It is very rare for heartworms to be passed on to humans, and if they are, they don’t complete their life cycle.



Giardia is a common protozoan parasite that can infect any mammal including humans. They have 2 life stages: the cyst and the trophozoite. Your dog can contract this parasite by ingesting the cyst through contaminated water, feces, or prey. Once inside the host, the cyst enters the gastrointestinal system and begins the trophozoite stage where they reproduce rapidly.


Giardia is easily transferred and very common in dogs. Up to 50% of puppies will develop it and up to 100% of dogs in shelters can contract it. The reason for this is because of the close, shared living conditions of these dogs.


Giardia can cause vomiting and diarrhea. Their diarrhea will be soft and frothy with a strong odor. It may even have a greasy appearance. You may also notice that your dog is losing weight.


Your vet can test for giardia with a stool sample but sometimes the results can be incorrect. The best way to test for it is with the ELISA (Enzyme-Linked Immunosorbent Assay) blood test. This test uses antibodies and color to test for specific substances. In this case, it would detect a specific protein that is particular to the giardia parasite. This test is quite conclusive but can also be expensive.


There are several drugs available that will treat your dog for a giardia infection. Repeat exams are usually necessary to make sure that the parasite is completely gone.


There are vaccines available to prevent Giardia. Another way to keep your dog safe is to bring clean water with you anytime you go camping or hunting. Even the most pristine looking stream can have the giardia organism in it.


Humans can contract giardia, although it is very rare to get it from a dog. The type that infects humans is usually a parasite of a different kind.



Ringworm is not actually a worm or a parasite. It is a fungal infection that can cause hair loss and produces a scaly area on your pet that is circular in shape. This area is not usually itchy.


Your dog can pick up this infection when his skin comes into contact with spores of the fungus. These spores are commonly found in soil and on cats. A cat can have these spores present even if it doesn’t show any signs of having ringworm. These spores can float in the air for years.


If your dog has ringworm you will probably notice dandruff within his coat. There can also be red lesions on the head, chest, forelegs, and on the ridge of his back. These lesions will often be circular in shape. You may also notice scaling, crusting, or thickening areas of skin.


Your vet can usually diagnose ringworm just by looking at it. Sometimes they may use a special ultra violet lamp called a wood lamp. If needed they can also do a fungal culture.


Ringworm usually goes away on its own but sometime the dog will need antifungal medications. You will also need to clean your house thoroughly to try to remove all the fungal spores. It is a good idea to change all air filters and disinfect all of your dog’s bedding, brushes, etc. If you have any other pets you should treat them as well since it is so easily spread.


The best way to prevent ringworm is to regularly clean your dog’s bedding and dispose of his hair when you brush and groom him. You should also vacuum your house on a regular basis and disinfect all pet areas.


Humans can catch ringworm from a pet. If your dog is infected, avoid touching the area. If you find a round, red lesion on yourself then it may need to be treated with an antifungal medication.


Natural Treatments and Preventatives

We have mentioned prescribed medications that can help prevent or kill a parasite infection, but there are also natural remedies available that can help prevent or even treat a parasite infection. Some of them are beneficial when given in proper amounts but can be dangerous if your dog receives too much of it. Always ask your vet for advice before trying any of these to make sure they are safe for your dog.


Garlic helps boost the immune system and also helps fight off parasitic worms and giardia. You can give your dog ½- to 2 cloves of garlic daily depending on his size.


Fruits and Vegetables

One benefit of feeding your dog fruits and vegetables is that it makes his intestinal tract less inviting to worms. You can give your dog grated raw carrots, fennel, shredded coconut, and papaya.


Oregon Grape

This is an herb that can be an antiparasitic and can also be an effective antibiotic. This is administered as a tincture (a medicine made by dissolving a drug in alcohol). You would usually use about 12 drops for every 20lbs of your dog’s weight, but as mentioned above, consult with your vet for the proper dosage and mixture. This can also work for giardia. Make sure you do not give this to dogs with liver disease or who are pregnant.



Chamomile is an herb that has been proven effective in preventing and expelling roundworms and whipworms.


Pumpkin Seeds

Raw, organic pumpkin seeds have been shown to help prevent and expel different parasitic worms. Some dogs will eat them like a treat, or you can grind them up and put them in their food bowl. You can give the dog about 1 tsp for every 10 pounds of his weight.


Concluding Thoughts

We hope this article has taught you many things you never knew about the different parasitic infections that are out there. You may have never realized how common some of them were or how easily they are transmitted. There are many ways to minimize the chance of your dog contracting a parasite – keep him and your house clean, pick up your yard regularly, and don’t skip the preventative medications that your dog needs.


Did you find this article helpful?
Click on one of the Share Links below to share it with a friend.