The study of parasites is called parasitology. It is an important discipline because internal parasites cause death and disease worth billions of dollars in animals each year. These parasites have highly evolved life cycles that make their elimination impossible. In addition, many internal parasites affect people with the potential for serious consequences.
Dogs and cats (especially puppies and kittens) are routinely infected with internal parasites, sometimes without apparent evidence of the infestation until it is too late. This means that a pet can have internal parasites even though the fecal sample is negative. It is suspected that internal parasites predispose your pet to IBD (Inflammatory Bowel Disease) later in life.
Fortunately, we have effective medications to treat most parasites. Many of the medications we use to treat internal parasites, called anthelmintics, treat more than one parasite. The advent of these broad spectrum anthelminitcs makes treatment much more effective. We recommend all dogs and cats get a treatment for internal parasites every 6 months.
This best method for treatment is to use flea products on a monthly basis that also kill internal parasites and prevent heart worms. We have several medications, some oral and some topical, to achieve this.
This section will discuss internal parasites that are commonly found in dogs and cats in our area. This includes:
These internal parasites differ from external parasites, which usually affect the skin and ears of dogs and cats. Click here to learn more about external parasites.
Symptoms manifested by pets that are infected with internal parasites can vary, and depend on a pet’s age, nutritional status, parasite load, duration of infestation, etc. One of the most common symptoms of internal parasitism is diarrhea. Other symptoms include poor appetite, lethargy, coughing, and abdominal distention. Some pets don’t show any symptoms while others can die from their infestation. Internal parasites tend to infest older and younger animals most commonly. Internal parasites can also make a pet more susceptible to other diseases. It is not uncommon for a puppy with Parvo virus to have internal parasites simultaneously.
Due to the prevalence of internal parasites in dogs and cats, their lack of symptoms in some cases, and the potential for humans to become infested also, your pets feces should be checked for internal parasites twice a year. Dogs and cats that are outside and exposed to other animals should have their feces checked more often. Routine worming should be performed on all dogs and cats every 6 months, even if the stool check for parasites is negative.
The majority of internal parasites are diagnosed by microscopic examination of the feces for eggs that are released by the adult female in your pet’s intestine. The number of eggs released in a given fecal sample can be variable, sometimes there aren’t any even though your pet has an adult female parasite in its intestines. This means that a negative fecal report does not guarantee that your pet is free from internal parasites. In many cases we need to run numerous samples to feel comfortable that your pet is free of internal parasites. In some cases our doctor’s will treat for a specific parasite, even on a negative fecal sample, when they feel there is a likelihood of infestation, because some internal parasites eggs are notoriously hard to detect.
In some parasites a diagnosis is made by observation of the mature parasite in your pet’s feces or during an autopsy in your pet’s intestines. This is especially true for Tapeworms. Tapeworm eggs are difficult to detect during microscopic fecal analysis, so observation of the actual worm is how they are routinely diagnosed.
The two primary methods of fecal analysis are direct observation and fecal flotation. In direct observation a smear is made of some fecal material on a microscope slide and the slide is analyzed by one of our nurses for parasite eggs. It is used to detect eggs that don’t show up well during the fecal flotation.
Fecal flotation is the most accurate way to detect most internal parasites. A sample of fresh feces is put into a special solution that causes any eggs that might be present to float to the top and adhere to a cover slip. The cover slip is put on a microscope slide for analysis. This concentration of eggs substantially increases the chance of finding any eggs that might be present. Some eggs, notably Tapeworm eggs, dissolve during this process and might be undetected. This is the reason you can see Tapeworms in your pets stool yet the fecal analysis came back negative.
We have sanitary containers for you to use to obtain a fecal sample from your pet. Once the sample is obtained it should be kept cool until we analyze it. Analysis should be within 12 hours to increase accuracy.
The flotation solution has been added to the fecal container and a cover slip has been placed on the top to collect any eggs that float to the surface after a 5 minute wait
The cover slip is put on a microscope slide and carefully scanned for the eggs of any parasite. High magnification is needed because the eggs are microscopic in size.
Internal parasites have very sophisticated life cycles that can make treatment difficult. Some of these life cycles involve mandatory maturation processes in other animals, including insects. Specific treatment modalities are set up to address these life cycles and will be discussed for each individual parasite in the following sections. It is important to follow these treatment regimens precisely.
Some parasites can only be controlled, not eliminated. In these cases it is important to check your pet’s feces routinely and to use medication on a long term basis.
There are new treatments for internal parasites that are very broad spectrum. They kill a wide variety of parasites, and are the medications we use as a routine wormer.
Trifexis kills internal parasites, heartworms, and fleas, and is recommended for dogs.
Please ask our receptionist for brochures on these products.
By far the most common internal parasite we encounter is Tapeworms. The scientific name for the Tapeworm we encounter in our area is called Dipylidium.
The source of the infestation is a flea that has been swallowed by your pet or a cat that eats infected rodents. The flea gets the Tapeworm in its system by swallowing it during its larval stages, when the larvae eat the eggs that have been passed from pets that are already infested with Tapeworms.
The lifecycle of the Tapeworm is simple compared to other internal parasites
In spite of their prevalence Tapeworms are not a significant cause of disease in dogs and cats. Most pets do not have any symptoms, and if symptoms are present, are mild in nature. Some pets will itch at their anus or scoot on the ground when the worms cause irritation as they pass.
Most Tapeworms are diagnosed by visualizing the worm in your pets feces, crawling around its anus, or in its bedding. Tapeworms segments crawling on your dog’s anus might cause scooting, although full anal sacs are a much more common cause of scooting. They come in long attachments that usually break off into individual pieces when they exit from your pet. They usually look like pieces of white rice and turn yellow after they have been out of the body for a while.
This is a packet of Tapeworm eggs as viewed under a microscope. It is rare for us to see them in this packet because the fecal flotation solution causes this packet to burst.
Several medications are available that are highly effective at ridding you pet of Tapeworms. The most common treatment is an oral medication that rids your pet of all Tapeworms within 24 hours. This medication also kills rounds, hooks, and whipworms. It does nothing to prevent your pet from re-infecting itself. Proper flea control does.
Since fleas are directly responsible for this infestation their control is apparent. We recommend advantage and Program for safe, economical, convenient, and highly effective flea prevention. A new product, called Revolution, will kill fleas, heartworms, ear mites, and even internal parasites. Please ask our receptionist for a brochure.
Public Health Significance
Children can pick up Tapeworms from eating fleas, but it rarely causes any problem. Other species of Tapeworms exist that have significant potential to cause serious disease in people. Fortunately, we do not encounter them in our local area in dogs and cats.
A common parasite of dogs and cats, especially puppies and kittens, is Roundworms. The scientific name for their group is called ascarids. We routinely treat puppies and kittens for this parasite for 2 reasons. The first is their prevalence, the second is their potential to infest humans. The larval form of this parasite has the potential to cause serious disease in children. Fortunately it is a rare problem, and can be prevented by worming all puppies and kittens early in life. It is all prevented by monthly use of flea and heart worm prevention products like Trifexis for dogs and Revolution for cats, since these products also kill roundworms.
The life cycle of this parasite almost ensures that a puppy or a kitten will be exposed. They can get it from their mother while they are in the uterus (dogs), during nursing, and through contamination with infected feces. Larval forms of this parasite migrate through internal organs, get coughed up and swallowed, and become mature parasites in the small intestines. Intermediate hosts like rodents can become infected by eating eggs, and can then infect a dog or cat when they are eaten. Some larvae migrate to the tissues of internal organs and remain dormant until pregnancy where they become active and infect the developing puppies in the uterus.
Common symptoms are a distended abdomen and diarrhea. Some puppies and kittens will be vomiting, lethargic and not eating well, while others will not show any symptoms. On rare occasions the parasite load can be so heavy that the intestines become obstructed. Coughing, fever, nasal discharge and even pneumonia can occur in pups that have large numbers of larvae migrating through their respiratory tract.
In some cases the Roundworm will be present in your pet’s feces, vomitus or crawling around its ansu. This is not a consistent finding, and worms that might be present one day might not be there the next.
It looks like a curled up piece of spaghetti
The vast majority of Roundworm infestations are diagnosed on fecal analysis for eggs. Young puppies can be infected before the eggs of the parasite appear in the feces.
This is one type of Roundworm egg when viewed under the microscope. The thick membrane around the eggs prevent them from drying out when they are laid in the environment.
There are several effective treatments for Roundworms. We can easily treat your pet with an oral version given during a routine office visit. It has to be retreated in 2 weeks due to the migrating larvae since the medication does not kill the larvae. Some pets require several more treatments for a full cure. If you keep your pet on Trifexis or Revolution year round you are treating for this problem monthly. This is the best way to go.
Roundworm eggs can remain viable for a long time in the environment. Children will get this parasite by eating dirt contaminated with the eggs, therefore cleaning up your pet’s feces immediately, and eliminating exposure to the feces of other animals when your pet goes for a walk, are important treatment modalities. Litter pans should be changed frequently and washed thoroughly and then allowed to dry in the sun. Keeping cats indoors also eliminates exposure to the feces of infected pets and the eating of infected rodents.
Public Health Significance
Children are of particular vulnerability to infestation because of their propensity to put things in their mouths and their attractions towards puppies. areas that might be contaminated with dog or cat feces should be off limits to children. This might include public areas such as parks or playgrounds. Even though these infestations in children are relatively uncommon, if they occur there can be significant damage to the internal organs like the liver, heart, brain, lungs, and eyes. This reason alone is why all puppies and kittens should be routinely treated for Roundworms, whether or not their fecal exam indicates they have parasites. also, teach your children to wash their hands frequently after handling pets, and not to put anything unnecessary in thier mouths.
Hookworms are blood sucking parasites that live in the small intestine. The scientific name for the Hookworm we encounter in our area is called Ancylostoma. They can be very pathogenic and even cause death due to anemia and low protein level.
Hookworms are spread by eating infected larvae that are in the environment. These infective larvae can also penetrate the skin and enter the blood stream where they mature into adult Hookworms in the small intestine. Puppies can also get infected while nursing or in the uterus prior to birth. Some Hookworm larvae migrate to muscles where they serve as a source of future infections.
Pets with Hookworms have the potential to be very ill,especially in dogs. Symptoms include lethargy, dark stools or diarrhea, weakness and vomiting. In severe cases they are anemic and debilitated, especially the older and younger pets. The larvae might even irritate the skin when they penetrate between the toes and pads.
Adult Hookworms are small so they are usually not seen passed in the feces. This diagnosis is made primarily by finding the distinctive egg in your pet’s feces. Any pet that is anemic should have its feces checked for this parasite.
These eggs are more oval than Roundworms, and the membrane is thinner
Infected pets might require hospitalization and even a blood transfusion if their symptoms are severe. There are different types of worming medications used, some require retreatment several weeks after the initial treatment because of the larvae that migrate through the body. All require checking your pet’s feces to make sure the parasite has been eliminated. Long term treatment and surveillance in the form of fecal exams are necessary. Dogs with chronic problems are put on heartworm preventive medication on a monthly basis since this medication also kills Hookworms. Any dog put on heartworm preventive medication needs to be checked for heartworm disease before we start preventive medication.
If you keep your pet on Trifexis or Revolution year round you are treating for this problem monthly. This is the best way to go.
Fecal exams should be performed frequently on pets that have a history of Hookworm infestation. Prompt removal of feces helps prevent contamination of the yard with larvae. Larvae are killed in cold climates when exposed to freezing temperatures.
Public Health Significance
Hookworm larvae can penetrate the skin of people and cause significant irritation. These larvae can migrate through the body and cause damage to internal organs. Just like in Roundworms discussed above, puppies should be routinely treated for this parasite at a young age.
Whipworms are blood sucking parasites that live in the large intestine, usually only in dogs. They are called Whipworms because they have a slender end and a thick end, hence the appearance of a whip. The scientific name for the Whipworm we encounter in our area is called Trichuris. They can be as pathogenic as Hookworms, and also cause death due to anemia and low protein level.
Female Whipworms lay eggs in the environment that eventually turn into larvae. Pets ingest these larvae when they ingest soil that is contaminated. These larvae take 3 months to develop into adults capable of causing disease.
Symptoms of Whipworm infestation include chronic diarrhea, anemia, and weight loss.
Like most internal parasites Whipworms are diagnosed by looking for the eggs in the feces. They are oval in shape and have a plug at each end that aids in identification. Their thick membrane gives them significant protection. The eggs are shed intermittently, so a negative fecal sample does not guarantee that your dog is free of Whipworms. Adult Whipworms can sometimes be visualized when an endoscope is passed into the rectum of a pet with chronic diarrhea.
Various oral medication are also used to treat Whipworms. Treatment is commonly repeated in 3 weeks and 3 months due to the life cycle of this parasite. If you keep your pet on Trifexis or Revolution year round you are treating for this problem monthly. This is the best way to go.
Control of reinfections is difficult because eggs that have been laid in the environment are very resistant. Feces need to be rechecked and a long term plan for surveillance and treatment needs to be initiated.
Public Health Significance
Human infections with this parasite might occur, although this controversial. Common sense dictates prompt removal of feces from your pet’s environment and washing your hands any time there is a potential exposure.
Coccidia are not technically a worm, but a protozoan parasite that infect dogs and cats primarily, but can be seen in other species.
Coccidia life cycles are complex and involve many stages of development. Coccidia produce cysts instead of larvae and eggs. Dogs and cats usually get the infection from ingesting the cysts in the environment or eating animals like mice that are already infected.
Symptoms usually occur in young animals and include diarrhea and abdominal pain. These young animals can become severely dehydrated and the infection can be life threatening. This is especially true in pets that are stressed or have other parasites. Many pets, especially the older ones, do not show any symptoms when infected.
Diagnosis of Coccidia infection is made by identifying the very small eggs in a fecal sample. They can be very difficult to detect due to their small nature and variable shedding by a pet. This is why our doctors will occasionally treat a pet for Coccidia even though the fecal exam is negative for this parasite.
Sulfa type medications or sulfa and antibiotic combinations are used to affect a cure. They need to be given for up to 3 weeks. There is also a medication that requires only 3 days of treatment. Kittens that are very ill require hospitalization and intravenous fluids to help them fight off the infection.
Prompt removal of feces helps prevent continued environmental contamination.
Public Health Significance
A version of Coccidia, called Toxoplasmosis, is of particular significance to pregnant women since it can cause disease in unborn children. The most common source of infection for pregnant women is eating improperly cooked meat (especially pork, lamb, and venison), not necessarily from the feces of cats. In a cat that does have Toxoplasmosis, the eggs that are laid in the environment (litter pan) do not become infective until 24 hours have passed. If the litter pan is cleaned twice daily the eggs will not have time to become infective to pregnant women. Wear gloves when you change the litter pan. Better yet,have someone else clean the litter pan. When you garden you should also wear gloves since stray cats may use the soil as a litter pan. Keeping your cat indoors and not feeding it raw meat will prevent it from getting Toxoplasmosis and passing it on.
According to the Centers for Disease Control and Prevention more than 60 million people in the United States are infected with the Toxoplasmosis parasite. Few have symptoms because a healthy immune systems keeps it in check. You may feel like you have the “flu,” swollen lymph glands, or muscle aches and pains that last for a few days to several weeks. However, most people who become infected with toxoplasmosis don’t know it. On the other hand, people with immune system problems, such as those with HIV/AIDS, those taking certain types of chemotherapy, or persons who have recently received an organ transplant, and infants, may develop severe toxoplasmosis, which results in damage to the eye or the brain. Infants who became infected before birth can be born retarded or with several other serious mental or physical problems.
Giardia are also protozoal parasites that live in the small intestines. Giarida are found every where in the world, Infection rates are variable, with younger animals having a higher rate of infection. There are various strains that differ in their potential to cause disease. The strain called Giarda lamblis (also called intestinalis or duodenalis) is the primary strain of people, companion animals. and livestock.
This parasite can be found on fecal exams of healthy pets that don’t have any symptoms. It is probably under diagnosed due to the chronic nature of the problem it presents and the difficulty of coming up with a positive diagnosis.
Giardia exists in 2 forms; trophozoites and cysts. The active and motile form, called trophozoites, are the stage which lives in the intestines of an affected mammal. These trophozoites produce non-motile cysts which are shed into the environment. The cysts remain viable in the environment for months, especially in cool and moist areas. They thrive in clear and cool water, a good reason not to drink running water in the outdoors, no matter how pristine it looks. The cysts are killed by freezing, boiling, and extended contact with disinfectants.
It is theorized that giardia make pets prone to food allergies. By interfering with the intestinal lining they let in proteins that stimulate the immune system to cause an allergic reaction.
The cysts in a contaminated environment are transmitted to mammals or birds upon ingestion. Gastric acid and pancreatic enzymes work on these cysts in the stomach and intestines, causing them to release 2 trophozoites. These motile trophozoites attach to the lining of the small intestine where they interfere with digestion. Within 2 weeks they encyst and are passed in the feces to contaminate the environment and await another host.
In many pets there aren’t any symptoms, while in others that do show symptoms, the problem might resolve by itself. The most susceptible pets are puppies and kittens, pets with other internal parasites, and debilitated pets. Diarrhea that occurs can be severe and can be accompanied by poor appetite and dehydration. Vomiting, weight loss and blood in the stool are occasional symptoms.
Giardia can be hard to diagnose because the parasite cysts become shriveled in the routine fecal solution that is used to bring eggs to the surface and adhere to the cover slip. Special fecal flotation solutions (zinc sulfate) are a more accurate manner to make the diagnosis. Cysts can be shed intermittently, so several samples are sometimes needed to make this diagnosis.
Fresh fecal samples that are not put in the fecal solution can sometimes show the parasite. We sometimes send fecal solutions to our outside lab for special tests when we suspect the problem yet we don’t find the parasite. Just like Coccidia, our doctors might treat for this disease even on negative fecal samples.
Flagyl is the drug routinely used to treat Giardia, although it does not cure all Giardia infections. The usual course of therapy is for 5 days, although our doctors will vary this dose depending on specific circumstances. Other medications are sometimes used if the Flagyl is not effective. There is no drug that is 100% effective against Giardia.
We recommend treating pets that are positive for Giardia even if they don’t have any symptoms. This helps eliminate environmental contamination, and helps minimize spread to people. If one pet in a household has Giardia we recommend treating all pets.
Giardia cysts in a kennel are relatively easy to destroy with routine disinfectants, and are susceptible to drying and heat. Once an environment like a lawn is contaminated though, it can be almost impossible to eliminate this parasite.
- Treat all in contact animals in the household.
- Recommend to bathe all pets every 7-14 days with mild hypoallergenic shampoo like Hilyte or and oatmeal shampoo. If unable to bathe then to wipe down with separate clean damp cloths/towels once a day or once every other day especially around the anal area (please save this area for last).
- Wipe feet and anal area of affected pet at least once a day especially after going outside with a clean damp cloth/towel. OK to use baby wipes around anal area.
- Prevent licking on surfaces outside, prevent from eating grass, and prevent from drinking water from communal water dishes at dog parks or from ponds or ditches as much as possible.
- Give bottle water or filtered water or water that has been boiled. This filters should filter out up to Giardia and Cryptococcus organisms from tap water. Boiling the water will kill any organisms present in the tap water.
- Thoroughly clean food and water dishes daily with soap and hot water and sterilize the food and water dishes weekly.
- Pick up feces immediately or as soon as possible. Recommend to thoroughly clean out litter boxes daily and to disinfect and sterilize the boxes at least once a week.
- Once done with medications bathe all pets or at least bathe both dogs and wipe down all feline pets in the house with separate clean damp cloths/towels. Also clean and vacuum entire house and clean all bedding.
- Once done with course of medications please bring a fecal sample the same day or the next day that the medications are finished. If the fecal results are negative then do another fecal analysis in 30 days post-treatment. If the fecal results are still positive for Giardia then will recommend to proceed with other possible causes of this persistently high infestation with Giardia i.e. immune system problems that are preventing her from getting rid of this protozoal parasite.
Good nutrition, avoiding overcrowding, general parasite control, and proper sanitation procedures are all critical in prevention. Cleaning up feces on a daily basis goes a long way to preventing contamination.
A vaccine available for dogs is very helpful in persistent infections
Public Health Significance
According to the Centers for Disease Control and Prevention, Giardia is one of the most common causes of waterborne diseases in humans in the United States. Many people get Giardia from other people and and contaminated water. Symptoms in people include diarrhea, abdominal cramps and nausea. They appear within 2 weeks of exposure to the parasite.
Exposure comes from many sources. They include swallowing water from swimming pools, lakes, rivers or streams that have been contaminated with animal or human feces. Fruits and vegetables that have not been washed (with Giardia free water!), along with accidental ingestion from hands contaminated by using toys, bathrooms, changing tables, etc., are also sources of infection. This emphasizes the importance of routine washing of hands. Boiling drinking water for one minute will kill this parasite.
We routinely treat pets with Giardia in their feces, even if they are not showing any symptoms, because of the potential for people to pick up this disease. Washing your hands frequently after touching your pet and bathing your pet frequently will help minimize exposure. We have a vaccine for dogs that do not respond to routine treatment. This will help prevent human exposure.