What is a Gastrointestinal Parasite in Dogs?
What is it?
How is it Treated?
Breed Predispositions
Beagles Coonhounds Foxhounds German Shepherds Boxers Doberman Pinschers
Introduction
Olivia had been noticing that her beloved Australian Shepherd, Jasper, was experiencing some unusual digestive issues lately. He had been losing weight, had intermittent diarrhea, and seemed to have a decrease in energy. Concerned for Jasper’s well-being, Olivia promptly scheduled an appointment with her veterinarian. After a thorough examination and some lab tests, the vet informed Olivia that Jasper was suffering from a gastrointestinal parasite infection, something she had never considered as a possibility. In this blog post, we’ll take a closer look at gastrointestinal parasites in dogs.
Canine gastrointestinal parasites are intestinal worms that affect dogs. Parasites were also detected in intestines harvested from 102 of 120 (85.0%) stray dogs in Mexico City. They include roundworms (ascarids), hookworms (Ancylostoma spp.), whipworms (Trichuris vulpis), and tapeworms (Taenia spp.). The most common parasite in dogs is the roundworm. It affects dogs worldwide.
Types of Intestinal Parasites in Dogs
1. Roundworm
Roundworms are parasitic worms that live in the intestines of humans and animals. They are round because they look like a ring when seen through a microscope. Worms are segmented organisms made up of many cells called segments. Each segment contains one pair of germ cells (eggs) and somatic cells (body tissue). Most roundworms are intestinal parasites that feed off their host’s blood and tissues. Some species of roundworms cause disease in people, and some benefit their hosts’ health.
Types of Roundworms
The most common type of roundworm found in dogs is Toxocara Canis. This parasite lives in the intestine of puppies and adult dogs. It can infect humans if the dog eats contaminated soil or dirt. If this happens, the larvae enter the human body through the mouth. Once inside the body, the larvae travel to the lungs, where they mature into adults. Next, they move to the liver and brain, where they grow into eggs. When these eggs are passed out in feces, they contaminate the ground and become food for pets and children who play outside.
Infections are usually seen among puppies. They are passed via fecal matter. Puppies ingest the eggs while playing around in the yard. If you notice your puppy acting lethargic, vomiting, having diarrhea, or having difficulty defecating, it could be due to roundworm infection. A fecal test can determine whether or not your dog has been infected.
Toxascaris leonine is another parasitic nematode (roundworm) found in dogs. It causes toxocariasis, a disease characterized by inflammation of the eye and brain. The parasite lives in the small intestine and attaches itself to the wall of the intestines. When the dog eats grass containing eggs, larvae hatch and migrate through the intestinal tract into the lungs, where they mature and then travel to the liver.
They move back up the esophagus and out through the mouth. Once inside the body, the worms may cause severe damage to organs such as the eyes, heart, kidneys, and central nervous system.
2. Hookworms (Ancylostomatidae)
Hookworms are parasitic worms in the small intestine of humans and animals. The most common species found in dogs is Ancylostoma caninum. It is transmitted through contaminated feces from infected hosts. Infection occurs when the dog ingests the infective larvae (L3), which hatch from eggs in the host’s stool.
This process occurs when the dog defecates into the soil, where the larvae develop into adult worms. Adult worms reside in the intestinal wall and produce millions of eggs daily. Eggs are shed in the feces and contaminate the environment.
Infected dogs usually do not show any symptoms until adulthood. After that, however, some dogs may exhibit signs such as diarrhea, weight loss, vomiting, coughing, lethargy, weakness, fever, abdominal pain, and even death. If left untreated, the Infection can lead to severe complications, including malnutrition, dehydration, and potentially fatal disease.
3. Whipworms (Trichuris)
They are usually found in puppies and kittens under one year old. The most common species found in dogs is Tritrichuirus Canis, and one of the lowest parasite infection rates belonged to Trichuris Vulpis and Acanthocephalans (0.2% each). At the same time, in cats, it’s known as Tritrichuirus Felis. The worm lives in the small intestine and produces eggs by passing through feces.
The eggs hatch into larvae, which then enter the environment. They develop into adult worms when they contact soil, water, plants, etc.
The most common way for the dog to get whipworms is by eating contaminated food. Eating contaminated food is the most common way for the dog to get whipworms Food items such as grass, hay, or bedding can contain whipworm eggs. The eggs can penetrate the intestinal wall and become mature worms if the dog eats these items. Another way the dog can contract whipworms is if he ingests infected fleas or ticks. Fleas and ticks carry whipworm eggs. Once inside the body, the eggs hatch and produce larvae.
Infected animals can spread the disease to humans. For example, humans can get whipworms from ingesting contaminated food or drinking contaminated water. In addition, people who work closely with pets (such as veterinarians) are at risk because they may accidentally eat or handle infected material.
4. Tapeworms (Taeniidae)
Tapeworms are common parasites that live inside the intestines of animals. They cause severe health problems in their hosts. The most common type of tapeworm infection in dogs is called cysticercosis. This intestinal parasite lives in the small intestine, where it causes inflammation and swelling. It can lead to severe complications such as seizures, coma, blindness, paralysis, and death.
Symptoms include vomiting, diarrhea, weight loss, lethargy, fever, seizures, muscle tremors, stiffness, weakness, lack of coordination, depression, and aggression. Diagnostic tests include blood work, ultrasound, and X-rays. Treatment includes removing the worms surgically if they’re found early enough or administering anti-parasitic drugs.
5. Protozoan Parasites
Protozoan parasites are microscopic organisms that live inside animals’ bodies. They’re called protozoa because they resemble single-celled plants.
Most protozoans cause no harm, but some species can harm humans. For example, some protozoans can infect dogs through contact with infected feces.
Types of Protozoan Parasites
- Giardiasis
Giardiasis is a disease caused by internal parasites called Giardia lamblia (also known as Giardia intestinalis). The parasite lives in the intestines of infected animals and people. In some cases, the parasite can cause diarrhea, vomiting, weight loss, fatigue, abdominal pain, bloating, cramps, flatulence, gas, nausea, constipation, and dehydration. In addition, animals who drink untreated water from lakes, streams, rivers, ponds, or wells where Giardia is found may become infected.
The symptoms of Giardiasis usually appear 2–10 days after exposure to contaminated food or water. Symptoms include diarrhea, stomach cramping, and sometimes vomiting. However, some pets may show no signs at all. If your pet shows any of these symptoms, contact your veterinarian immediately. Your vet may prescribe medication to treat the Infection.
Giardiasis is often spread through direct fecal contamination of food or water. For example, if you feed raw meat scraps to your dog, this could contaminate their feces and make them sick. Therefore, you should wash your hands thoroughly before feeding your pet. Also, do not let your pet lick their feces off themselves. This can spread germs into the air and onto surfaces.
- Coccidia – Isospora spp.
Coccidia is a group of protozoa that causes coccidiosis in animals. It is one of the most common parasitic diseases of domestic animals worldwide. The disease occurs when the intestinal parasite enters the body through contaminated food or water. In humans, the Infection usually results from eating undercooked meat containing oocysts (eggs) shed by infected feces of birds or mammals.
The life cycle of this gastrointestinal parasite begins with the ingestion of sporulated oocysts into the host’s small intestine. Next, sporulation occurs in the intestinal lumen and releases thousands of infectious cyst stages. After several days, these cysts reach the large intestine, where they mature into unsporulated oocysts. Oocysts are then passed out in the feces.
Parasitic Infection occurs when the oocysts enter the environment via fecal contamination of soil, water, feed, bedding, etc., or by direct contact with feces. Once ingested, the oocysts hatch and release their sporozoites.
Sporozoites invade epithelial cells lining the digestive tract, liver, lungs, kidneys, brain, eyes, reproductive organs, and skin. They multiply rapidly and form tissue schizonts, which rupture, releasing merozoites. Merozoites infect new cells, causing further damage and inflammation. This process continues until the entire gastrointestinal tract is affected.
6. Cryptosporidia (Cryptosporidium spp.)
Cryptosporidium parvum (Cp) is a protozoan parasite that causes cryptosporidiosis in humans and animals. It is found worldwide and infects many species, including mammals, birds, reptiles, amphibians, fish, insects, crustaceans, mollusks, and plants. In addition, Cp is one of the domestic animals’ most common intestinal parasites.
The disease is usually mild and self-limiting in healthy individuals; however, severe cases can occur in immunocompromised people such as those infected with HIV/AIDS. In addition, young children and elderly persons have a huge potential zoonotic risk of developing life-threatening complications.
The transmission occurs when the oocysts from feces contaminate food or water sources. Oocysts are resistant to environmental conditions and remain viable for long periods. They are excreted in the environment through human and animal waste and can survive for months in soil and manure.
Infection occurs when contaminated fecal matter enters the body via the mouth, nose, eyes, or anus. After ingestion, the oocyst passes into the small intestine, releasing sporozoites that invade intestinal epithelial cells. Sporozoites then migrate to the liver, where they develop into infectious meronts. Meronts release new merozoites, which travel back to the intestines, where they cause Infection.
7. Sarcocystis spp.
Sarcocystis ssp. is a protozoan parasite that causes sarcocystosis (Sarco) in animals. It is a common disease in domestic and wild carnivores worldwide. The life cycle involves two hosts; the definitive host, usually a carnivore, and the intermediate host, usually a herbivorous animal. Definitive hosts ingest sporocysts from contaminated food or water. Inside the intestine, the sporozoite stage develops into merozoites which invade muscle cells and develop into cysts.
In some species, these cysts rupture, releasing thousands of bradyzoites that multiply inside the tissue and cause inflammation. This process results in clinical signs such as weight loss, fever, lameness, weakness, diarrhea, vomiting, abdominal pain, and death.
Sarcocystis ssp. is an internal parasite that lives in the muscle tissue of animals such as cats, dogs, horses, pigs, cattle, sheep, goats, deer, rabbits, birds, rodents, etc. It causes sarcocystosis, a disease characterized by cysts (Sarco) in muscles.
The most common symptoms include fever, weight loss, diarrhea, vomiting, weakness, lameness, and sometimes death. Dogs are commonly infected through contact with feces from infected wild carnivores, especially foxes. Other sources include eating undercooked meat containing Sarcocystis, drinking unpasteurized milk, or handling infected carcasses. Infected dogs can shed millions of sporozoites into their environment, including water.
Sporozoites remain infectious outside the intermediate host until they enter another animal’s body. Once inside the new host, the parasites develop into merozoites, infecting cells lining the small intestine. Finally, Merozoites mature into schizonts, which rupture and release thousands of daughter merozoites, called meronts, into the bloodstream.
Meronts invade red blood cells, where they undergo further development into bradyzoites, which form cysts in tissues. Bradyzoites can remain dormant for years before reemerging as tachyzoites, which cause acute parasitic Infection.
Symptoms of Intestinal Parasites in Dogs
It is estimated that one-third of dogs suffer from parasitic infections. Parasitic worms cause most cases of diarrhea in dogs. They live in the dog’s intestines and release toxins that irritate the intestinal lining, causing inflammation and diarrhea.
Symptoms include vomiting, loose stools, and sometimes bloody stool. If left untreated, these conditions may lead to dehydration and malnutrition.
To prevent such problems, it is recommended that pet owners treat their pets regularly for parasite infestations. Here are some tips on identifying the signs of GI parasites in dogs.

- Vomiting
Vomiting is an early sign of GI parasites in dogs, especially puppies. This condition usually occurs after feeding or playing. Puppies tend to vomit frequently due to incomplete digestion of food.
- Diarrhea
Diarrhea is another common symptom of GI parasites in dogs and cats. Usually, it starts suddenly and lasts for several days. Some dogs develop diarrhea after eating certain foods, such as raw meat.
- Bloody Stool
Bloody stool is a serious problem that can occur in dogs suffering from GI parasites. Sometimes, the blood appears blackish red. Other times, it turns brownish yellow.
- Loss of Appetite
Dogs with GI parasites often lose their appetite. Their stomachs become bloated and distended. As a result, they eat less than usual.
- Lack of Urination
Urinating becomes difficult for dogs with GI parasites. Often, they urinate excessively and pass small amounts of urine.
- Weakness
Weakness is another symptom of GI parasites in animals. For example, dogs with GI parasites tend to be tired and weak.
- Lethargy
Dogs with GI parasitic infections are often lethargic and unresponsive. In addition, they seem to need more interest in normal daily activities.
Diagnosis of Canine Intestinal Parasites
Diagnosing gastrointestinal parasites in dogs requires a veterinarian to obtain a complete medical history from the pet’s owner and examine the dog for signs of infestation. If a dog is suspected of having parasites, the vet usually performs one or more tests to identify which type of parasite is present.
The first test is fecal flotation, which involves examining a sample of the dog’s stool under a microscope. During the flotation, the vet looks for evidence of eggs associated with various parasites, such as roundworms and hookworms. The results are typically available within 24-48 hours.
Another test that can detect GI parasites in dogs is fecal antigen assays, which measure antibodies produced by worms in the feces. Veterinarians may also use blood tests to look for worms that cause preventable diseases, such as heartworms and Giardia infections.
If an x-ray examination reveals an abnormal presence of something resembling worms in an animal’s intestines, it could be due to an infestation or disease caused by GI parasites. Lastly, endoscopies allow veterinarians to perform illuminated visuals of large spaces in the body using small camera scopes attached to long tubes inserted through natural openings such as mouths or rectums; this allows them to see directly into dogs’ digestive tracts and locate any suspicious materials.
Treatment and Prevention for Common Canine Gastrointestinal Parasites

There are ways to treat these intestinal parasites in dogs:
First, you need to identify them. This involves taking a stool sample and sending it to a lab for analysis. The lab will tell you whether your dog has worms, tapeworms, roundworms, hookworms, whipworms, or any combination thereof.
Once you’ve identified the type of parasite, you can decide how to treat it. There are two main types of treatments: preventative medications and deworming pills. Preventive medications kill the parasites’ eggs, preventing them from hatching and developing into adult forms. Deworming pills kill the adult form of the parasites.
Preventative medication is usually recommended for puppies and kittens because it prevents the development of the parasitic life cycle. However, some veterinarians recommend it for older pets too.
Deworming pills should be used every three months. Some vets recommend monthly treatment, while others say once per month is sufficient.
If your pet doesn’t respond to preventative medication, he may require deworming pills instead. These are typically given twice a year.
Many different brands of deworming pills are available, each containing a diverse mixture of active ingredients. Be careful when selecting a brand. Ensure the product has at least one of the following active ingredients: ivermectin, pyrantel, febantel, fenbendazole, oxibendazole, albendazole, mebendazole, levamisole, morantel, selamectin, milbemycin, moxidectin, flubendazole, emodepside, doramectin, imidacloprid, eprinomectin, and Sarolaner.
Some of these drugs are approved for use in cats, while others are specifically designed for dogs. Check the label carefully to select the proper medication for your pet.
When treating parasites in dogs, it’s important to remember that the dosage varies depending on the animal’s year or month of age. For example, puppies and kittens receive lower doses than adults. Also, remember that most drugs are toxic to animals, especially young ones. So, be very cautious when administering medication to your dog or cat.
Frequently Asked Questions
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