Intestinal Parasites In Your Cat And What To Do About Them

Ron Hines DVM PhD

Intestinal parasites are one of the most common problems veterinarians see in kittens. Although pets of any age can carry them, they are a health issue primarily in young cats, cats living in sub-standard or crowded conditions and cats with other health concerns. Felines and their parasites have had millions of years to evolve together. During that time, they have, begrudgingly, learned to tolerate each other. There are a large number of these worms and assorted freeloaders listed below, I’ll list them roughly in the order with which I run into them in practice.

How Will I Know If My Cat Has Worms?

Parasites are often “silent” and you will not know. The more common intestinal parasites have adapted so well to their hosts (your cat), that they are living in balance and cause no observable health issues. That can always change. It is when the parasites become too numerous for one reason or another that the pet’s health is affected. Because of their silent nature our best approach is to try to keep our pets completely free of them before the balance becomes disturbed.

The most common early signs of intestinal parasites in kitten are poor growth (stunting), dull hair coat, scrawniness (thin), lack of playful energy and diarrhea. Many of these kittens have bony bodies but potbellied, big tummies. Many are anemic. Kittens with parasite over-burden invariably grew up in poor sanitary conditions. They are often the offspring of feral or semi-feral cats, who are, themselves, nutritionally deprived, breeding at too young an age and too often.

It is exceedingly rare to find intestinal parasites in indoor cats living in a one or two-cat home. Cats are, by nature, very clean animals and parasites rely on poor sanitation to get around. However, when cats are forced into conditions that favor parasites, the most common signs of there presence in older pets are lack luster, brittle hair coat, boniness, listlessness and diarrhea. Some of these older pets become picky eaters; in some the opposite occurs and some show no change at all in their eating habits. In adult cats with parasite problems, multiple health issues are common. This is because the poor sanitation that leads to parasite-overload also increases the cat’s risk of exposure to other diseases and because their parasite burden lessens their resistance to other diseases (and vice versa).

How Will My Veterinarian Check For Worms In My Cat Or New Kitten?

Some parasites are large enough to be seen in the dog’s stool. When those are brought by owners to their veterinarian, the parasites can often be recognized and identified. This goes for tapeworms and roundworms. However, the rest of the common parasites of dogs are too small to be seen. In those cases, your veterinarian will look for the parasites, their eggs or cysts in stool specimens that you bring.

When parasites are in your cat in very large numbers, the veterinarian may be able to see them in a fresh suspension (“smears”) of the feces placed on a slide with some saline and examined under the microscope. That is the most rapid screening test a veterinarian can do.

But fresh direct suspensions (smears) miss over half the pets that carry parasites. They are quite good at detecting giardia and other protozoa that live within the intestine in vast numbers, but they often miss hookworms, roundworms, and whipworms. The later parasites are attached to your pet’s intestinal lining. The vet is looking for their eggs, not the worms, and those eggs are passed only in numbers reflecting the parasite # burden and even then, only intermittently. Direct suspension drops are best used to pass the time with clients while a fecal specimen floatation runs in the veterinarian’s laboratory (about 5-10 minutes). Even if the smear is positive for one parasite, there may be others found in the floatation. Multiple infections with several species of parasite is quite common in pets.

There are a few parasites (strongyloides) that do not float to the top of the liquids used to concentrate them in the flotation methods. The larva of some of those remain on the bottom of the floatation tube and can be found there, but most of those are picked up on the direct suspension.

Tapeworm segments and tapeworm eggs are rarely found mixed with feces. They pass out of your dog on the surface of the feces. So do not be surprised if your vet does not detect any . You need to specifically bring the suspicious objects in. Any time you bring in a suspected parasite, place it in a baggie with a moist paper towel. When they come to me shriveled and dry like a mummy, it can be quite hard to firmly identify them.

Fecal floatation is a way to concentrate parasite eggs and cysts on a slide to make it more likely they will be found. All use a solution that causes eggs to float to the top and most other debris to sink to the bottom of the container. Sometimes the passage of time is all that is required. In other cases the process can be speeded up by centrifugation. Some commonly used flotation liquids are sodium nitrite (Fecasol®), sugar and zinc sulfate. Saturated table salt will work, but it is less efficient.

When you collect fecal specimens from your cat, always wear gloves. Keep the stool specimen chilled with an ice pack if you can not get it to your veterinarian quickly – some parasite eggs hatch quickly and the resulting larva can be hard to find.

Are These Parasites A Serious Health Problem For My Cat?

A few of the common intestinal parasites of cats do not cause health issues. Some, like roundworms and tapeworms, absorb nutrients through their skin (cuticle) and do not normally injure the pet’s intestine. Others, however, like hookworms chew and erode the lining of your pet’s intestine. Strongyloides tunnels through the lining causing inflammation. Single-celled Giardia blocks nutrient absorption and is thought to produce a mild toxin while coccidia enter and destroy the cells of the finger-like projections (villi) that allow nutrient absorption from your dog’s intestine.

Your pet has great potential to brush off the effects of a few parasitic organisms, but when the number of these parasites is high, your pet’s health will suffer. Resultant diarrhea, gives less time for food absorption. Intestinal irritation lessens appetite and causes vomission (vomiting) and burrowing parasites cause blood loss and anemia.


Intestinal parasites are always worse when they affect young animals. The younger cats are when they are attacked, the worse the problem will be. That is because growing kittens have much higher nutrient needs and their inflamed intestines can not absorb nutrients. Their ulcerated intestines also leak precious blood. Tiny bodies lack the mass and reserves to deal with crisis and their parasitic immune systems (mucosal immunity) are not yet developed. That immunity relies on prior exposure to those parasites at low levels. In addition, these small creatures do not move about far from their birth/nest area – so feral liters can be continually re-exposed to parasite eggs. Some of these parasites, like hookworms are transferred to the pups through the queen’s milk (colostral transfer), and, possibly, while still in the womb (transplacental transfer) as well. Others, like roundworms, readily move from infected mothers to their babies while still in the womb. Many nematodes, such as hookworms and roundworms do not pass eggs immediately (their prepatent period). So just the fact that a kitten’s fecal exam was negative is no guarantee it is free of worms. Kittens with parasite problems tend to suffer from multiple problems, like rhinotracheitis (Herpes 1) virus, fleas, ear mites and nutritional deprivation. All these co-existing diseases weaken their ability to deal with intestinal parasites.

Adult Cats

Adult cats are much more resistant to most intestinal parasites. Given their natural tendency to cleanliness and private space they will clear themselves of intestinal parasites if given half a chance. But unlike dogs, adult cats are more likely to continue to shed parasite eggs when they remain infected.

However, when their environment is highly contaminated or their resistance is weakened , they too can become seriously ill. Much of age-related immunity is acquired by prior exposure to these common parasites. So cats that have not been exposed previously may react as ill as kittens if they are suddenly confined to shelter and group-home situations where large numbers of parasite eggs (ova) are found.

Many of these infections are said to be “compensated”. That is, the cat has adjusted to the parasite’s present with a natural immunity that keeps parasite numbers in check and shows no marked signs of illness. However, the general unthrifty nature of the cat will probably be noticeable to your veterinarian. You might not have noticed it because it came on very gradually.

A Bit More About Each Individual Intestinal Parasite:


Adult hookworms are quite small – barely visible to the naked eye. There are quite a few species of hookworm that can attack cats, but the most common and serious ones are Ancylostoma tubaeforme . and, to a lesser extent, A. braziliense.

The warm, humid conditions of the southeaster United States, Southern Europe, Central and South America favor its survival. Hookworms come in male and female.

The great majority of cats obtain hookworms through ingesting (eating) hookworm larva that have hatched on the ground from the parasite’s eggs. Stool from infected cats can contain millions of these, thin-shelled eggs. When that stool contaminates damp, cool soil, eggs adhere the pet’s fur and are licked off during grooming. Eggs must develop for a time before they become infective (1-2 days). When the hookworm eggs actually hatch into hookworm larva, they are capable of penetrating the pet’s intact skin and paw pads as well. Rodents that accidentally ingest hookworm larva become infested with dormant cat hookworms in their tissue. It is thought that cats eating these creatures is a second important way the parasite spreads. Cockroaches and other vermin that cats play with and eat are another possible source of infection. Not all locations harbor hookworm larva that are a threat to your cat. They persist best in warm, humid soil. Freezing, drying and temperatures over 98F quickly kill the eggs.

After hookworm 3rd stage larva are eaten, a complicated migration process begins leading to mature hookworm parasites arriving in the pet’s small intestine, approximately 10-14 days later. Eggs that have hatched in the pet’s stomach or hookworm larva that have penetrated its skin or mouth burrow into the pet’s circulatory system (blood and lymph). From there, they are carried to the lungs. Once in the lungs, the larva they escape and are coughed up and re-swallowed. (a cough may be present at this time) This time around, they attach to the walls of the pet’s small intestine where they feed on blood, mature, and eventually lay more eggs that repeat the cycle. They do not stay attached to one place, but move about causing tissue (mucosal) destruction and ulceration for all of their 4-24 month life span.

Most infected older cats show only mild, nondescript symptoms of mild anemia, weight loss, poor appetite and , perhaps intermittent vomiting and diarrhea. Some have elevated blood eosinophil counts.

But Kittens and younger cats with heavy hookworm loads can become quite ill. In young kittens, the infestation can be fatal. When kittens die from hookworms, they die from the anemia caused by the feeding worms. This can occur very suddenly in very young animals – sometimes before other symptoms occur. But in most cases, the infestation causes bloody diarrhea, weakness, and vomiting of varying intensity. It can be confused with panleukopenia another common disease that causes similar signs and the two diseases can co-exist.

Severely affected pets often require hospitalization, supportive care and medications to sooth and protect their traumatized digestive system. Supplemental Iron is also helpful, and, of course, a medication to kill the hookworms. In some cases, kittens and debilitated adult cats can only be saved through blood transfusions.

Worming medications kill only hookworms that have finished their journey to the intestine. Because the time that the parasites arrive in the intestine is staggered, a single worming is never enough. Kittens should receive those medications at 6 , 8 and 12 weeks of age – earlier when a particular litter is in danger. You can read more about hookworms here

Roundworms = Ascaridiasis, Toxocara cati, Toxascaris leonina

Roundworms and tapeworms are the largest parasites you are likely to see in your cat’s stool. If your pet is infested, the parasites will often appear in your pet’s vomit as well. These parasites are thin spaghetti-shaped critters, 3-12 cm long. When they are not surrounded by feces, they usually curl up in a spiral.

Unlike hookworms, cats become infected with roundworms by eating roundworm eggs – not larva. Kittens become infected within their first three weeks of life when their mother’s milk harbors the parasites. Cats that are out and about are more likely to encounter roundworms. Various varmints (rats, mice etc.) that come in contact with roundworm eggs end up with these parasites encysted in their bodies and can transmit them to adult cats if they are themselves consumed. Roundworm eggs are not immediately infective, they need about a week in the environment to activate.


Some studies have found that over a third of shelter kittens and young cats are infected with roundworms and shedding eggs. That is probably a low estimate, since eggs are not always present. The incidence is lower when cats are not forced into large-group situations.

Unlike puppies, most kittens show relatively few signs of ill health. It is very hard to decide when vague poor-health signs in kittens are really due to roundworms. That is because it is very rare for roundworm-positive kittens not to have other concurrent health problems such as virus infections, coccidiosis and malnutrition. But when the kittens carry large numbers of roundworms, their hair coat is often poor, they are less active and they do not grow as quickly. These large parasites thrash and move around in the kitten’s intestine causing intermittent colic, diarrhea, constipation, and vomission. On rare occasion, worms are so numerous that they block the intestine. Small kittens with large numbers of roundworms have a typical pot-belly.

Unsanitary conditions increase the likelihood of these parasites being around.

Roundworms have no mouth, so they do not chew and damage the kitten’s intestinal lining or cause anemia like hookworms do. But it is quite common for kittens that have roundworms to have hookworms as well. Luckily, medicines that destroy one, destroy the other.

Roundworms that hatch in your cat’s intestine do not stay there immediately. Instead, they migrate through the animals body (liver-lung migration) , congregate in its lungs where they are coughed up and re-swallowed. It is on this second pass that they set up housekeeping in the cat’s small intestine.

Because so many shelter kittens have roundworms, all should be treated for them. They need several wormings to destroy all the parasites. I generally worm kittens at 2, 4, 6 and 8 weeks of age and again when they receive their last kitten vaccinations (14 wks). The medication (pyrantel pamoate) costs only pennies and is not toxic. So use it liberally but according to dose directions.

Adult Cats

Adult cats do not appear to become as resistant to roundworms as adult dogs do. They are more likely than dogs to continue to shed parasite eggs in their stool and for the parasites to continue to live in their intestines rather than form dormant cysts in other tissues. That is probably why milk passage to kittens is uncommon.

Occasionally, one will obstruct the flow of bile from the liver but that problem is quite rare. Most adult cats that harbor roundworms show no visible health issues attributable to the parasites. But as in roundworm-infested kittens, the conditions that favor the parasites favor other diseases as well.

Because roundworm eggs are extremely resistant to drying, your cat will always be exposed to them if it is out-and-about. The outer shell of these eggs is quite sticky, so they cling to the cat’s coat and pads and get eaten during grooming. You can just assume that all outdoor cats are continually exposed to these resistant eggs.

Because many roundworms are dormant or shed eggs only intermittently, a negative fecal exam is no proof that they are not there. That is why some breeders periodically worm their pregnant and nursing cats. But that procedure must not be a crutch or substitute for good sanitation and health care. You can read more about roundworms here

Giardia = Giardia duodenalis G. intestinalis, G. lamblia

I see less Giardia problems in cats than I do in dogs – probably due to their more hygienic nature. When it does occur in cat it is usually sub clinical (no visible illness). It is also more common in high-density populations like coteries and shelter and in young animals.

Because this parasite produces a sold age-associated immunity, one rarely sees it cause a problem in mature pets unless they have another, underlying, intestinal disease. (ref)  This age-related immunity is incomplete and can be overwhelmed when pets are exposed to very high numbers of giardia. That is why a new puppy or pet in a multi-dog household often causes transient diarrhea in the other pets as well.

In addition to cats, most common household pets, as well as humans, are susceptible to giardia – related intestinal problems. But because so many distinct subspecies of the parasite exist, we are uncertain which can jump between species. Although humans, particularly children, regularly suffer from giardia-related diarrhea, the source is usually contaminated drinking or standing water or daycare facility exposure – not household cats.

Giardia living in your cat’s intestine are single-celled creatures (protozoa) that move about by means of long motile filaments (four pairs of flagella). This adult feeding form is called a trophozoites. It is a rather flattened organism with a broad “suction” disc on its bottom surface that holds it firm to the intestinal wall (proximal small intestine). After a period of time some of them release, rounds up and forms a resistant capsules. These are the giardia cysts that pass out in the pet’s feces to infect other animals. These cysts can survive for long periods (8wks) in cool contaminated water. Freezing, drying or strong sunlight kill them almost immediately as do most disinfectants.

When a new kitten or susceptible adult cat eats these cysts the cysts morph back into their trophozoites form where they multiply rapidly and may invade and irritate the lining of the animals small intestine. But most cats that are exposed to giardia never show symptoms or develop diarrhea. They may, however, pass the bug on to other pets.

In cats with diarrhea, the presence of giardia is quite easy to diagnose. Vets are likely to miss it if the stool sample is floated in standard flotation liquid. But when a drop of the stool is mixed with saline and examined under the microscope, the wriggling organisms are difficult to miss. They are much more difficult to locate in firm stool. There are veterinarians who claim to be able to identify the infectious cysts microscopically when they are present, but I am not one of them. A more accurate way to diagnose giardia when diarrhea is intermittent or when their numbers are low is to use the Idexx Elisa Snap Test. It is also a great way to identify pets that are still shedding the organism after treatment.

When the diagnosis of giardia in cats is made through microscopic identification, the vet must be very careful not to confuse them with T. foetusin. If there is any doubt, have your vet run the ELISA Snap test or send a fecal specimen to the UC Davis Taqman PCR lab.

When giardia infection causes illness, it is an effuse (watery) diarrhea that can lead to dehydration. Intestinal inflammation that accompanies severe diarrhea can cause secondary problems such as weight loss, intestinal ulcerations and rectal prolapse – particularly in young puppies. This can be life threatening in small kittens.

A vaccine against giardia is available – but I do not recommend it.

There are two medications that work well in controlling giardia, but most cases in half-grown and adult cats will clear up within a week without treatment. You can read more about giardia here. 

Coccidia, Coccidiosis, Isospora species

Coccidia, like giardia, are single celled organisms (protozoa) that have adapted to live within the cat’s body.

Virtually all cats encounter this organism sometime in their lives. In animal shelter situations, coccidia organisms are found up to 8% of the stool specimens of admitted animals. Like most parasites, they go hand in hand with poor sanitation, crowding and stress. As cats mature, the incidence of coccidiosis-related disease decreases significantly. Although mature cats may shed the infective stage of the parasite (oocyst) from time to time, it almost never causes disease symptoms in these animals.

There are many species of coccidia, but all are thought to be species-specific. So they are not a threat to your health. For instance, Isospora canis of dogs does not affect cats and Isospora felis of cats is not a problem in dogs.

Although coccidia primary spread between cats through fecal contamination, mice and other vermin can spread the parasite between cats when their bodies when they accidentally become contaminated. But the coccidia of mice, Eimeria, is not a threat to cats.

These organisms invade the lining of your cat’s intestine causing inflammation and diarrhea indistinguishable from giardia. They are only life-threatening in infant kittens and debilitated (weakened) animals where the diarrhea can lead to serious dehydration and colic prevent feeding.

The parasite encysted stage (oocysts) are easy to see and identify in fecal floatation tests and after the first few days, the number of coccidia seen correlate well with the severity of symptoms the pet is experiencing. Coccidia transfer from pet to pet through fecal contamination and oral ingestion. It takes about a week before symptoms begin and about five weeks after symptoms subside for the parasites to disappear from stool specimens. But some cats continue to shed a few parasites in their stools for long periods after recovery.
Early in the diarrhea stage, stool specimens can still be negative for coccidia oocysts. Veterinarians, particularly those working with shelters, sometimes begin treatment of these kittens with sulfa medications intuitively.
Small kittens often also need intravenous or subcutaneously-administered fluids as well as medications to calm and slow their intestines. TLC and supportive care for these infants is a very important aid to recovery.

Tritrichromonas = Trichomoniasis, Trichomonas foetus

A cousin of the Trichomonas that infects humans, this protozoan can cause chronic diarrhea in immature cats. It was only recently discovered as a pathogen of cats, although we have known for a long time that it infects swine and cattle. When it affects cats, they often have bouts of soft stools that come and go over long periods of time and occasionally contain flecks of blood and mucous. During bouts of this diarrhea, the cat’s anus is often painful and swollen. Some sources claim that up to 30% of cats carry this parasite.

Certain breeds (Bengals, Persians and Abyssinians) are, perhaps, particularly susceptible to it. During these bouts of diarrhea, the stool odor is intensely objectionable.

Unlike giardia and coccidia, Tritrichomonas lives in the lower intestinal tract (large bowel). So affected cats do not generally loose weight or condition.

We are uncertain how this parasite moves from cat to cat. But a fecal-to-oral rout is most likely.

These parasites are recognized through their characteristic motion (“barrel rolls”) so they will not be seen on an ordinary fecal floatation. When they are noticed in a direct microscopic examination of the cat’s stool, they are quite easy to mistake for giardia. So if your cat has a case of “chronic or reoccurring giardia” or giardia that is unresponsive to the two medications generally used to treat it, consider having a sample sent of the Davis or another similar RT-PCR lab for identification or an “InPouch” method. (ref) Since the same poor sanitation and environments that favor giardia seem to favor Tritrichomonas, it is conceivable that a cat could be infected with both at the same time.

One could also easily mistake this parasite for inflammatory bowel disease, so screen those cats for Tritrichomonas too. The standard medications used to treat diarrhea and intestinal parasites in cats has no effect on Tritrichomonas. Ronidazole is the only drug that appears effective. Untreated, most cats spontaneously recover after lengthy periods of time. (when suspected to be a mixed giardia/tritrichomonas infection, possibly metronidazole and enrofloxacin ?) (ref) You can read more about Tritrichomonas here.


Tapeworms are a very common intestinal parasite in dogs but they rarely if ever cause health issues. You can read more about them in another article of mine here and about the ones passed through raw meat here.

Toxoplasma = Toxoplasmosis, Toxoplasma gondii

You can read my article just about toxoplasma in cats here. You read a lot about toxoplasmosis, a disease caused by a little one-celled protozoan organism, when it gets into the wrong animal or humans. When it is living in the digestive system of cat, where it belongs, it rarely causes disease symptoms at all. However infected cats are Nature’s reservoir of this parasite. It’s natural life cycle is to move from cat to cat when they eat wild rodents. Normally, it is only when they are accidentally swallowed by humans, pets and other animals that they cause disease. Toxoplasma do rarely cause disease in immunosuppressed cats.

Human exposure to Toxoplasma is very common – about a third of the people in the world today have been exposed to it. (ref)

However, it is generally only people with immune system problems who become ill. Most folks never know they were exposed and their bodies quickly kill off these invaders. One exposure usually produced solid lifelong immunity to Toxoplasma. It is very rare for a person, once exposed, to become infected again. If you have your toxoplasmosis antibody  titer determined, you will know if you are already resistant to this parasite.

Most cats in the United States were exposed some time in their life to Toxoplasma and are now immune to it. When the parasite cysts are found in cat feces, it is usually in immature cats and kittens that have only recently been exposed. In those cats, they shed the parasite cysts in their stool for only 1-3 weeks and then also become immune.

The best way to avoid exposing your cat to Toxoplasma is to keep it indoors, not allow it to hunt and not feed it raw meat.

Toxoplasmosis is a threat to pregnant women and humans that are immunosuppressed from conditions such as HIV. You can read more about that here.  

Cryptosporidium = C. parvum, C. felis

This coccidia-like protozoan parasite is commonly found in the intestines of dogs, cats, humans and other animals. It occasionally causes a mild, transient (temporary) diarrhea. Cats become infected through fecal contamination or through consuming fecally contaminated food or water.

It’s telltale resistant cysts (sporulated oocysts) are hard to identify in the feces because they are exceedingly small. When it is suspected, it is best identified through laboratory PCR testing.

It is primarily a concern when cats are living with immunocompromised owners. If it spreads from the pet to humans with weak immune systems, it can cause serious intestinal inflammation, dehydration, fever and weight loss. You can read more about that here .

My Cat Scoots or Licks Its Rear . Is That A Sign It Has Worms?

Worms do not cause your cat to scoot or lick its rear end. That story originates with human pinworms, which do cause serious anal itching. However, dogs that have parasites often have loose stools. As normally-formed stools pass over the pet’s two anal glands, they naturally evacuate them of secretions. When your pet has persistently soft stools, these glands do not evacuate properly. That bothers your pet and causes it to scoot and lick its anal region. You can read about anal sac problems here. Persistent diarrhea also inflames the anus – compounding the problem.

Are Parasites A Concern If I Feed My Cat Raw Meat?

On of the reason humans have evolved to eat cooked meat is that it lessens exposure to disease. Parasites and bacteria are always looking for good ways to get around and infect new hosts. Traveling through their food supply is a very effective means of getting around.

Cats and humans have evolved together over the last 5,000 + years. Just like us, they do quite well when their diets are cooked. Some parasitic and bacterial diseases particularly associated with consuming raw meat are certain tapeworms, trichinosis, Echinococcus, Pathogenic E-coli, toxoplasmosis, listeriosis, etc .

I prefer feeding pets homemade diets because the quality of ingredients in most commercial pet foods is poor. But I suggest that the ingredients be heated to make them safe for your pet. If you feel you must feed raw mea to your dog, feed it supermarket meat that is safe for human consumption. Many, but not all, of the larger parasites that pose a threat to your pet’s health are destroyed by freezing (20 days @ -15C or 6 days @ -30C).   But those temperatures cannot be relied upon to kill bacteria. (ref)

I do not know of any beneficial health reasons owners would want to feed meat to their cats raw.

How Often Should My Healthy Cat Be Wormed – How Often Should Its Stool Be Checked For Parasites?

Many pet owners receive periodic reminder notices from their veterinarians that it is time to have their cat’s fecal checked for parasites. This is often done in conjunction with reminders that it is time for your pet’s yearly booster vaccinations. The typical practice model that veterinarians in the United States have followed for the last 70 years has been to derive the majority of their income from repeat, yearly services and the minority from required surgical and medical procedures. Fecal examinations, yearly vaccination boosters and the sale of medications and diets provide the bulk of their revenues. You can read a bit about that here. 

There will always be a rare pet that appears to the owner to be healthy but carries some form of parasite. But those cases are exceedingly rare in indoor cats. When was the last time you had your fecal checked? Your veterinarian works with parasite eggs day in and day out. When was the last time your veterinarian had his/her fecal checked? You alone can access the specific parasite risk in your pet. That is based primarily on its lifestyle and the sanitation of its environment. But considering the poor accuracy (ref) of veterinary fecal floatation methods when parasite numbers are few or moderate, it is much safer to just keep your pet on a monthly heartworm or flea preventative that also prevents intestinal parasites.

Most veterinarians send out their reminders every year; but some send them out every six months. Even if you depended on twice-a-year fecal exams, your pet could pick up a parasite egg the day after the examination. It is a bit like checking to see if your back door is locked, twice a year.

Fleas and intestinal parasites also use the similar methods to move from pet to pet. Pets in temperate climates that have no flea problem are considerably less likely to have intestinal parasites either.

My advice is for typical household pets in the Developed World. If your pet’s lifestyle differs from that, it does not apply to you. Pets that routinely enter contaminated areas, pets that are routinely boarded, pets with specific idiosyncrasies (quirky eating habits), pets that live in large groups or that range over large areas have different needs that may include routine fecal examinations and shorter vaccination intervals that I usually suggest.
Considering the poor accuracy (ref) of fecal floats, much better to keep your pet on a flea/heartworm preventative that also controls parasites.

Can Any Of These Parasites Infect Me Or My Children?

Yes, quite a few of them can. They often do not complete their life cycle normally when they infect humans, but they are a cause for concern. The problems is much more common when humans are exposed to parasitized dogs because cats are, by nature, more sanitary. But wear gloves when you change your cat’s litter box, do not use dusty products and change it frequently. Do not keep your litter boxes in kitchens, bedrooms or bathrooms – keep them in areas with less traffic. Use covered litter boxes and those with sides high enough to prevent scattering.

The greatest sources of exposure are to young children. They are the park sandboxes, which are choice placed for free-roaming cats to defecate. That is one of the many reasons I do not approve of establishing feral cat colonies or letting your cat go in and out as it pleases.

The most common human problem associated with intestinal parasites of pets are cutaneous and visceral larval migrans. This problem occurs when parasite larva penetrate human skin or when parasite eggs are accidentally consumed.

When people accidentally eat roundworm eggs, the migrating larva that hatch from those eggs usually do not find their way to the intestine. Instead, they wander lost through body tissues, causing inflammation wherever they pass. When they wind up in the liver (visceral larva migrans) or other abdominal organs they can produce fever and inflammation that can be quite hard to diagnose. If they enter the eye (ocular larva migrans) they may damage the retina and vision. A telltale sign of this problem is often an increased blood eosinophil count.

These problems are more common in children, due to their less-developed immune systems, their less developed hygienic habits and the likelihood they will play in contaminated areas.

Children are always attracted to cute kittens – another potential source of exposure. Supervise them and wash their hands

Dog and cat hookworms are the most common cause of cutaneous larval migrans – a rash that occurs when these parasites attempt to burrow through human skin. The symptoms are similar to those of chigger bites, but the red areas are streaky rather than round. Shady, moist and cool areas where grass has been denuded are the most common places these larva are picked up.

Giardia is a common cause of human diarrhea. Most cases result from drinking contaminated water or raw salads, but there is probably the potential of catching it from infected kittens as well. It is unclear whether the common strains of giardia found in cats have the potential to cause disease in humans. But be safe wear gloves and take simple precautions when you have contact with cat stool or kittens and cats with diarrhea.

One cat coccidia, Toxoplasma, is a particular threat to pregnant women. Most people in the US were exposed to Toxoplasma in their childhood and are resistant to it. However, if their resistance is low or they were never exposed, they can develop the disease, toxoplasmosis which has, on occasion affected their unborn children severely.

What Are The Medications Veterinarians Us To Rid My Cat Of Worms In Cats?

Piperazine = Hartz Once-A-Month, etc.

This product has been on the veterinary and human market longer than any other. It is effective only against roundworm and must be given several times. Piperazine will only kill roundworms that are living in the cat’s intestine. Those that are still migrating there are immune to its action. There is really no sense in giving it because cats that have roundworms often also have hookworms as well and this medication has no effect on hookworms at all. (ref)

Pyrantel Pamoate = Nemex®, Strongid®, etc.

This is a great, safe product for removing roundworms and hookworms. It is inexpensive, and easy to administer. In the correct dose, it is safe to give to pregnant and very young animals. One dose is rarely enough to remove every parasite.

Fenbendazole =Panacur®, etc

Fenbendazole kills many more species of parasites than pyrantel pamoate. It may be a better choice when diarrhea is suspected to be due to intestinal parasites but the identity of those parasites is unknown. Three consecutive days of treatment are generally required. It is labeled for dogs but frequently given to cats.

Praziquantel = Droncit® , etc.

This medication kills only tapeworms. It is extremely effective in doing so. It can be given orally or by injection. I prefer to inject it because then I am certain the pet did not spit it out or vomit it later. It should not be given to kittens under 4 weeks of age and I use it cautiously in debilitated animals of any age.

Praziquantel/pyrantel pamoate/febantel (Drontal Plus®, etc.) NOT FOR CATS
This combination kills a wide variety of intestinal parasites. The febantel portion is particularly effective in killing whipworms. It is not yet available for use in cats because , cats do not tolerate febantel as well as dogs. Also, the pyrantel portion of the dog tablet is too low for cats. Drontal cat tablets contain no febantel.

Epsiprantel = Cestex®

This medication, like praziquantel, is also effective against tapeworms. It appears to be equally effective (100%) as praziquantel in killing tapeworms.

Ponazuril = Marquis Paste® 

Some shelters have experimented in the use of this compound in pets to treat coccidiosis. It is approved only for horses. Its chief advantage over other products is its low per-dose cost. Mass puppy producers also us it to control coccidiosis (as a substitute for good sanitation). I have no personal experience using it but your veterinarian can access information on its use in pets through this link.

Metronidazole =Flagyl®

This compound is used to control giardia and , occasionally, to control bacterial overgrowth that accompanies other parasite infections.

Sulfadimethoxine = Albon®, etc.

This sulfa medication is given to control coccidiosis. I have not noticed that kittens rid themselves of these parasites any faster when given this medication, but I give it as well to prevent additional intestinal complications and deal with concurrent health issues.

Ivermectin = Ivomec®, etc

The bovine (cow) formulation is given subcutaneously to dogs for a variety of parasitic problems – including gastrointestinal parasites. Its chief advantage is its low cost when purchased for livestock.


This is one of the few effective medications against Tritrichomonas in cats.

What About Natural, Homeopathic, Herbal And Other New Age Worm Medicines I Read About?

These medications are based on folk remedies that were thought to aid parasitized human beings. That was before people understood enough about the difference between parasite physiology and the physiology of our bodies to select compounds that killed one without injuring the other. It was a time when humans also believed in dragons, unicorns and a sun revolving around the Earth. They knew nothing about sanitation and believed that parasites miraculously appeared in the body (spontaneous generation).

But there were some that did work. They relied on creating such severe diarrhea that the parasites were flushed out (for example  arecoline) or they were toxic plant compounds given in the hope that the amount necessary to kill the parasite was less than the amount able to kill the human (nicotine, tobacco, wormwood).  Your traditional veterinarian has very safe compounds (vermifuges, paraciticides) today that are much better. They home in on specific weaknesses in the parasites to kill them without hurting your cat.

There is very little reason to resort to these obsolete methods. At best, they will not harm your pet – but they are quite unlikely to cure your pet’s parasite problems either. The ones that cause severe diarrhea (purgatives) can cause problems of their own – such things as rectal prolapse and intestinal intussusceptions.

What Can I Do To Be Sure My Cat Never Gets Worms Again?

There are two things to be done to prevent your cat from ever having intestinal parasites again. You are safer with a combination of the two rather than either one alone.


Your pets rely on your judgment to prevent their exposure to parasites. If you have read this far, you already know that most of these parasites enter your pet through its mouth from infective eggs, cysts or larva that have exited in the stool of another infected pet. If you minimize your pets exposure to areas where this is likely to happen, you will minimize your pet’s chances of contracting these parasites. So:

Do not let your cat loose outdoors unsupervised.

Do not take your pet to areas frequented by cats and dogs whose parasite status is unknown

Hire pet sitters rather than boarding you dog at kennels or animal hospitals.

Do not bring additional cats of unknown parasite status into your household until they have been wormed several times and their fecal status is negative.

Remove stool promptly. Ware gloves, bag it and place it in your outside trash can

Use covered cat litter trays, clean and empty them frequently

Keep your cat from chewing and playing with objects that can not be easily sanitized or that do not come directly from the store.

Monthly Parasite Preventatives

Sanitation alone is usually sufficient to prevent intestinal parasites in your cat. If it is not, then keeping your cat on a monthly flea/tick/heartworm control product designed to also control intestinal parasites is a very good idea.

These products are all safe – when cat-use is listed on the label. Read the directions on the product insert and follow them carefully. If a particular parasite is a problem, your veterinarian may suggest one of these products over another. Your local veterinarian will also make that decision based on which parasites are most common in your area and the degree of drug resistance that those parasites have attained. Here in South Texas and Florida, my favorite is selamectin because our fleas appear to have become resistant to many products.

If you plan to breed your cat, and it is not on a monthly preventative, worm it several times before breeding and again, with a pregnancy-safe product, just before it gives birth.

Cleaning Up The House And Yard

Some parasite cysts and eggs, such as hookworms and giardia do not have protective coatings. Those eggs are die in a relatively short period when they are exposed to sunshine, warmth and drying. For those parasites, a good cleaning of the house and airing out are sufficient. Put all washable things through a hot-water washer-dryer cycle and let them sit for a week if possible before using them again. Fill a trash can with a 1:20 solution of household bleach and let any bleachable items, such as food and water bowels sit in it for an hour. Remove as much accumulated grime before the soaking. Vacuum rugs and throw away the vacuum cleaner bag.

Cats do quite well and are much safer from all dangers when they spend their lives indoors. But if you must allow your cat to go outdoors, mow your grass short, remove yard clutter and bring some sunlight into shaded areas. Keep your cat out of the yard for a week or two. Police up all areas where cats have defecated as best you can. I now of few cats that respect the borders of your yard – so you will not accomplish much.

Other parasites, such as roundworms, whipworms and coccidia produce eggs and cysts that make them very difficult to destroy and keep environments contaminated for long periods – even years. They are much harder to deal with.

Common disinfectants have no effect on them although all are killed by live steam. They and the grime that contains them must be physically removed. It is a lot of work, but it can be done when surfaces are smooth and washable. It is next to impossible on porous surfaces or on items that cannot be washed or heated without destroying them.

It is possible to encapsulate these eggs and cysts with a new coat of paint on paintable surfaces (the same techniques used for asbestos and lead paint) or to add a fresh layer of topsoil over contaminated areas of your yard. Even though sunlight and warm temperature do not kill resistant eggs, like roundworm and whipworm eggs immediately, they probably lessen the period of time they survive.

Bleach, diluted to reasonable strength, will not kill roundworms. But it is said to remove the sticky coating that make them cling to objects and make cleanup easier. Whenever working with bleach, it is much more effective if objects and surfaces are pre-cleaned of as much organic material and grime as possible.

If your yard is unfenced, consider fencing it to keep out stray animals. If you must feed pets outside of your house, remove the food at night. Feeding birds is fine. But feeding raccoons and other wildlife in areas that your pets frequent is not a good idea.

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