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There are 6 Types of Intestinal Parasites:
Hookworm infection has several special features that are of interest to us as the caretakers of dogs:
a. Hookworms suck blood by attaching to the intestinal wall like leaches.
b. Hookworms can be transmitted to unborn puppies.
c. Hookworms can infect humans.
Hookworms can be transmitted to dogs in 4 different ways:
1) Through the placenta.
2) Through the mothers milk.
3) By ingesting eggs from the soil usually during normal grooming.
4) By the larval stage penetrating the skin.
2. ROUND WORMS
Round worms can be transmitted to dogs in 4 different ways:
1) Through the placenta.
2) Through the mother’s milk.
3) By ingesting eggs from the soil usually during normal grooming.
4) Consuming a prey animal (usually rodent) that is carrying developing worms.
Toxocara canis has one of the most amazing life cycles in the animal kingdom. It is crucial to understand this life cycle if effective treatment is to be pursued.
STEP ONE: Toxocara eggs are passed in the host's feces. If a fecal sample is tested, the eggs can be detected. The embryonic worm develops in the outdoor environment inside its microscopic egg for one month before it becomes able to infect a new host. If environmental conditions are favorable, it takes about a month for the egg to become infective but Toxocara eggs are famous for weathering harsh environmental conditions. Eggs can remain infective for months to years. Note: Fresh feces are not infectious.
STEP TWO: The egg containing what is called a second stage larva is picked up by a dog or by some other animal. The egg hatches in the new host's intestinal tract and the young worm burrows its way out of the intestinal tract to encyst in the host's other body tissues. If the new host is a dog, the life cycle proceeds. If the new host is a member of another species, the larvae wait encysted until the new host is eaten by a dog.
STEP THREE: These second stage larvae can remain encysted happily for years. If the host is a dog, the larvae mostly encyst in the host's liver. When the time comes to move on, the larvae encyst and migrate to the host's lungs where they develop into third stage larvae. They burrow into the small airways and travel upward towards the host's throat. A heavy infection can produce a serious pneumonia. When they get to the upper airways, their presence generates coughing. The worms are coughed up into the host's throat where they are swallowed thus entering the intestinal tract for the second time in their development. If the host is pregnant, the larvae do not migrate to the lung after they encyst; instead they come to the uterus and infect the unborn puppies. The second stage larvae make their way to the puppy’s lungs to develop into third stage larvae. If the host is a nursing mother, second stage larvae can migrate to the mammary gland instead of the lung after encysting. Puppies can be infected by drinking their mother's milk, though, due to the intrauterine cycle described above, the litter would probably already be infected. Note: When dogs are dewormed, this affects only worms in the intestinal tract. It does not affect encysted larvae. It is very difficult to prevent mother to puppy transmission and routine deworming is not adequate.
STEP FOUR: Once back in the intestine, the larvae complete their maturation and begin to mate. The first eggs are laid about one week after the fourth stage larvae have arrived in the intestine and about 4 to 5 weeks after infection has first occurred. From here the cycle repeats.
WHY IS INFECTION BAD?
Roundworm infection can have numerous negative effects. It is a common cause of diarrhea in young animals and can cause vomiting as well. Sometimes the worms themselves are vomited up which can be alarming as they can be quite large with females reaching lengths of up to seven inches. The worms consume the host's food and can lead to unthriftiness and a classical pot-bellied appearance. Very heavy infections can lead to pneumonia as the worms migrate and, if there are enough worms, the intestine can actually become obstructed. It should also be noted that human infection by this parasite is especially serious (see below). It is important to minimize the contamination of environmental soil with the feces of infected animals so as to reduce the exposure hazard to both humans and other animals.
HOW DO WE KNOW IF OUR DOG IS INFECTED?
You may not know and this is one of the arguments in favor of regular deworming. Regular deworming is especially recommended for dogs that hunt and might consume the flesh of hosts carrying worm larvae. Puppies are often assumed to be infected and automatically dewormed.
Of course, there are ways to find out if your dog is infected. If a dog or puppy vomits up a worm, there is a good chance this is a roundworm (especially in a puppy). Roundworms are long, white and described as looking like spaghetti. Tapeworms can also be vomited up but these are flat and obviously segmented. If you are not sure what type of worm you are seeing, bring it to your veterinarian's office for identification. Fecal testing for worm eggs is a must for puppies and a good idea for adult dogs having their annual check up. Obviously, if there are worms present, they must be laying eggs in order to be detected but, by and large, fecal testing is a reliable method of detection.
HOW DO WE GET RID OF ROUNDWORMS?
Numerous deworming products are effective. See the end summary for a description.
There are two important concepts to keep in mind about deworming. Medications essentially anesthetize the worm so that it lets go of its grip on the host intestine and passes with the stool. Once it has been passed, it cannot survive in the environment and dies. This means that you will likely see the worms when they pass so be prepared as they can be quite long and may still be alive and moving when you see them. The other concept stems from the fact that larvae in migration cannot be killed by any of these products. After the worms are cleared from the intestine, they will be replaced by new worms completing their migration. This means that a second, and sometimes even a third deworming is needed to keep the intestine clear. The follow-up deworming is generally given several weeks following the first deworming to allow for migrating worms to arrive in the intestine where they are vulnerable. This is why we do multiple fecals during the puppy wellness visits and start them on Interceptor/Sentinel.
WHAT ABOUT TOXASCARIS LEONINA?
The life cycle of Toxascaris leonina is not nearly as complicated. They do not migrate through the body in the way that Toxocara does. Instead, the Toxascaris second stage larva is consumed and simply matures in the intestine, a process that takes 2 to 3 months. Like Toxocara, Toxascaris can infect hosts of other species, though with Toxascaris the larvae can develop into third stage larvae in these other hosts while with Toxocara larval development is arrested in species other than the dog.
Note: Toxascaris leonina can infect both dogs and cats alike.
Toxocara canis is the predominant cause of a serious condition called visceral larva migrans in humans. Most victims are children. They are infected by inadvertently consuming worm eggs in soil (typically by getting dirty fingers in their mouths). The worm is not present in its correct host but tries to complete its life cycle anyway. The worm gets lost in the human body (classically in the eye), dies, and generates an extreme inflammatory reaction. If the worm dies within the human eye, blindness usually results. For this reason, it is important for parents to be aware of this hazard. Proper hand washing will prevent infection. Monthly pet deworming will reduce environmental contamination. Public leash laws and restriction of dog walking are meant to reduce fecal contamination of public areas. Stray cats should be kept away from children's sandboxes. For more information on this subject, please visit one of the Centers for Disease Control web sites on visceral larva migrans at:
(For a fact sheet on Toxocariasis)
(How to Prevent Transmission of Intestinal Roundworms from Pets to People)
3. WHIP WORMS
This worm is one of the "big four" intestinal parasites with which our canine friends must contend: roundworms, tapeworms, hookworms, and whipworms. The whipworm of dogs (Trichuris vulpis) is substantially smaller than the other worms (a mere 30 to 50 mm in length, about a half inch maximum) and is rarely seen as it lives in the cecum (the part of the large intestine where the small and large intestines meet). The "head" (or more accurately the digestive end of the worm) is skinny vs. its stout tail (or reproductive end) which gives the worm a whip shape, hence the name.
In the digestive tract, food passes from mouth to esophagus to stomach to small intestine to large intestine to rectum and then to the outside world. This means the large intestine is one of the last stops for nutrients and by this point in the journey; nutrients have largely been broken down and absorbed. The large intestine (also called the "colon") serves to absorb water, to store fecal material, and to provide a home for a spectacular number of bacteria that are able to digest the leftover food that we cannot.
The large intestine is the home of the whipworm. The adult worms bite the tissue of the intestine, actually embedding their "heads" inside, and suck blood there. Eggs are laid inside the large intestine and pass with the stool. Once in the outside world, the eggs require about 2 to 4 weeks to form embryos and become capable of infecting a new host. (This means that contaminated soil is the source of infection, not fresh feces.) The new host is infected from consuming the egg. The egg hatches in the small intestine releasing a larva. The larva dives into the glandular tissue of the small intestine and after about a week emerges into the small intestine and is carried into the large intestine with the intestinal contents. Once in the cecum, its permanent home, it embeds in the tissue there, and after a total 74 to 87 days from the time the egg was swallowed, the young whipworm is ready to mate.
A few whipworms generally do not pose a problem for the host but if large numbers of worms are present embedding themselves in the large intestine tissue, tremendous inflammation can result leading to a bloody, gooey diarrhea. Usually there is not enough blood loss to be dangerous but the diarrhea readily becomes chronic and hard to control.
A second syndrome of infection has emerged but is not well understood, this being symptoms mimicking those of Addison's disease (hypoadrenocorticism). Here, a waxing and waning weakness with inability to conserve salt ultimately creates a dehydration crisis. The syndrome mimics Addison's disease in every way except that testing for Addison's disease will be negative and deworming yields a complete recovery. Because female whipworms only periodically lay eggs (whereas other worm females lay eggs continuously), a fecal sample tested may easily be negative for eggs. This makes the confirmation of a whipworm infection a challenge. It is common to deworm for whipworms if the symptoms are suggestive of the whipworm presence even if the fecal test is negative.
Most deworming agents do not work on whipworms and something special must be selected. The most common products are Fenbendazole (Panacur®), and febantel (Drontal Plus®). Milbemycin oxime, the active ingredient in Interceptor and Sentinel also helps prevent the infection with whipworms
Because of the long maturation cycle of young worms, a second deworming some 75 days or so after the first deworming is needed to fully clear the infection (easy to forget). Often another deworming in between these doses is recommended to further control the whipworm numbers. More recently, regular heartworm prevention products have been developed to remove and control whipworms: Sentinel and Interceptor both will cover whipworms and their regular use covers the second deworming as well. Heartgard products do not carry a high enough dose of ivermectin to kill whipworms, though at other doses ivermectin could be used. Soil contaminated by whipworm eggs is contaminated for years. It is virtually impossible to remove the eggs from the soil or kill them. Fortunately, this is one pet intestinal parasite that is not transmissible to humans.
Cats DO get whipworm infections but they are uncommon and not really significant
Biology of the Parasite (Dipylidium caninum) The adult Dipylidium caninum lives in the small intestine of the dog or cat. It is hooked onto the intestinal wall by a structure called a rostellum, which is sort of like a hat with hooks on it. The tapeworm also has six rows of teeth to grab on with. Most people are confused about the size of a tapeworm because they only see its segments, which are small; the entire tapeworm is usually 6 inches or more. Once docked like a boat to the host intestinal wall, the tapeworm begins to grow a long tail. (The tapeworm’s body is basically a head segment to hold on with, a neck, and many tail segments). Each segment making up the tail is like a separate independent body, with an independent digestive system and reproductive tract. The tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. When the segment drops off, it is basically just a sac of tapeworm eggs. As Rover sleeps, tapeworm segments are passed. The sac is passed from the host’s rectum and out into the world, either on the host’s stool or on the host’s rear end. The segment is the size of a grain of rice and is able to move. Eventually the segment will dry and look more like a sesame seed. The sac breaks and tapeworm eggs are released. Tapeworm segments and flea dirt are found together in Rover’s dog bed.
Larval fleas are generally hatching in this vicinity and these larvae are busy grazing on organic debris and flea dirt (the black specks of digested blood shed by adult fleas to nourish their larvae). The flea larvae do not pay close attention to what they eat and innocently consume tapeworm eggs. Tapeworm segment breaks, releasing eggs. Eggs are eaten by grazing flea larva. Flea larvae pupate. Rover licks himself and swallows fleas. As the larval flea progresses in its development; the tapeworm inside it is also progressing in development. By the time the flea is an adult, the tapeworm is ready to infect a dog or cat. The flea goes about its usual business, namely sucking its host’s blood, when to its horror, it is licked away by the host and swallowed. Inside the host’s stomach, the flea’s body is digested away and the young tapeworm is released. It finds a nice spot to attach and the life cycle begins again. It takes 3 weeks from the time the flea is swallowed to the time tapeworm segments appear on the pet’s rear end or stool. For more information on fleas and flea control, go to a special area prepared by the Iowa State Veterinary College:
WHY IS IT CALLED A TAPEWORM?
This creature gets its name because its segments and body are very flat (like a piece of tape).
WHAT DO THEY LOOK LIKE?
The adult tapeworm inside the pet can be a half a foot or more long. It is made of small segments, each about the size of a grain of rice. The tapeworm’s head hooks onto the dog’s intestine by tiny teeth and the worm absorbs nutrients through its skin. Each segment contains a complete set of organs but as new segments grow in at the neck area and older segments progress to the tip of the tail, the organs disintegrate except for the reproductive organs. When the segment drops off from the tail tip, it is only a sac of eggs. This segment is white and able to move when it is fresh and, at this time, looks like a grain of white rice. As the segment dries, it looks more like a sesame seed.
WHERE DO THEY COME FROM?
There is no other way for a pet to get tapeworms except from fleas. Many people who had thought their pet could not possibly have fleas find out about the infestation this way. The tapeworm segment breaks open releasing its eggs. A larval flea consumes the egg along with the flea dirt that it normally eats. As the larval flea matures, so does the baby tapeworm. When a grooming dog or cat licks the flea and swallows it, the dead flea is digested in the dog’s stomach releasing the baby tapeworm. The tapeworm is passed to its new home in the dog or cat’s small intestine where it attaches and lives its life. This parasite does not harm the pet in any way as there are plenty of nutrients passing by to serve both the host and its tapeworm (tapeworms require very little nutrients.) Still, high performance dogs, which need every Calorie working for them, may show a decrease in performance because of a tapeworm infection.
HOW DO YOU KNOW IF YOUR PET HAS THEM?
The presence of tapeworms can be diagnosed by finding the moving segments, dried segments, and occasionally by seeing eggs in the feces if the segment had ruptured. Occasionally active segments around your pet’s anal area will cause him to lick or ‘scoot’ on the floor.
WHY DO THEY SOMETIMES FAIL TO SHOW UP IN A FECAL TEST?
Because the eggs are passed by the pet in packets (segments), they often do not show up on the fecal exam. (The packet must break open for the eggs to be seen.) Consider that the pet has tapeworms if segments are seen under its tail, around its anus, or on its feces. Segments can be passed in small groups connected to each other leading the owner to describe a worm that sounds larger than a grain of rice. Tapeworm segments are also quite flat. Some people will mistake maggots in the stool for tapeworms. Maggots are not seen in freshly passed stool and are not flat.
CAN PEOPLE GET THEM?
Theoretically, yes, people can get them but they must be infected the same way dogs and cats are: by swallowing an infected flea.
HOW DO WE GET RID OF THEM?
Tapeworms are killed by different medications (one is called Droncit, brand name Praziquantel), which is administered by injection or tablet. The tapeworm is killed and digested with the pet’s food. It is not passed in the stool later.
WHY DO SOME VETERINARIANS RECOMMEND TWO TREATMENTS AND OTHERS ONLY RECOMMEND ONE TREATMENT?
Only one treatment is needed to kill tapeworms that are present; however, many clinics recommend a second injection in three weeks. The reason for the second injection is this: If the owner finds out at the time of their office visit that they need to control fleas to control tapeworms, they will need at least a month or so to control the fleas. After the first treatment is given, there is no reason why the pet cannot immediately re-infect itself. It probably will re-infect itself at some point. By seeing the animal in three weeks and giving another treatment after the fleas are controlled, there is a good chance that the tapeworms will not just be back three weeks later. It takes 3 weeks from the time tapeworms are swallowed by the pet to the time segments can be seen by the owner. On the other hand, who knows when the pet will swallow another infected flea? Our recommendation is that a single treatment be administered whenever segments are seen.
IF ONE PET HAS TAPEWORM SEGMENTS, CAN IT BE ASSUMED THAT THEY ALL DO?
No, just because one pet in the household has swallowed an infected flea does not mean they all have. Our recommendation is to deworm only the pets that have obvious tapeworms.
WHY MIGHT A PET CONTINUE TO GET TAPEWORM INFECTIONS?
While many people would like to blame the medication as ineffective, the truth is that there must be an on-going flea population in the pet’s environment. The key to eradicating tapeworms from the home is flea control.
There are many different species of Coccidia for dogs and cats, but the most common infections are with Coccidia of the genus Isospora. The information presented here pertains to Isospora species. What on Earth are Coccidia? Coccidia are single celled organisms that infect the intestine. They are microscopic parasites detectable on routine fecal tests in the same way that worms are but Coccidia are not worms and they are not visible to the naked eye. Coccidia infection causes a watery diarrhea that is sometimes bloody and can even be a life-threatening problem to an especially young or small pet.
Where does Coccidia Come From?
Oocysts (pronounced o'o-sists), like those mentioned above, are passed in the stool. In the outside world, the oocysts begin to mature or “sporulate.” After they have adequately matured, they become infective to any host (dog or cat) that accidentally swallows them. To be more precise, Coccidia come from fecal-contaminated ground. They are swallowed when a pet grooms/licks the dirt off itself. In some cases, sporulated oocysts are swallowed by mice and the host is infected when it eats the mouse.
Coccidia infection is especially common in young animals housed in groups (in shelters, rescue areas, kennels, etc.) This is a common parasite and is not necessarily a sign of poor husbandry.
What Happens Inside the Host?
The sporulated oocyst breaks open and releases eight sporozoites. These sporozoites each finds an intestinal cell and begins to reproduce inside it. Ultimately, the cell is so full of what are called “merozoites” that it bursts releasing the merozoites, which seek out their own intestinal cells, and the process begins again. It is important to note how thousands of intestinal cells can become infected and destroyed as a result of accidentally swallowing a single oocyst. As the intestinal cells are destroyed in larger and larger numbers, intestinal function is disrupted and a bloody, watery diarrhea results. The fluid loss can be dangerously dehydrating to a very young or small pet.
How Are Coccidia Detected?
A routine fecal test is a good idea for any new puppy or kitten whether there are signs of diarrhea or not as youngsters are commonly parasitized. This sort of test is also a good idea for any patient with diarrhea. Coccidia are microscopic and a test such as this is necessary to rule them in. It should be noted that small numbers of Coccidia can be hard to detect so just because a fecal sample tests negative, this does not mean that the pet is not infected. Sometimes several fecal tests are performed, especially in a young pet with a refractory diarrhea; parasites may not be evident until later in the course of the condition.
How is Coccidiosis Treated?
We do not have any medicine that will kill Coccidia; only the patient’s immune system can do that. But we can give medicines called “coccidiostats” (i.e. sulfa drugs) which can inhibit coccidial reproduction. Once the numbers stop expanding, it is easier for the patient’s immune system to “catch up” and wipe the infection out. This also means, though, that the time it takes to clear the infection depends on how many Coccidia organisms there are to start with and how strong the patient’s immune system is. A typical treatment course lasts about a week or two but it is important to realize that the medication should be given until the diarrhea resolves plus an extra couple of days. Medication should be given for at least five days total. Sometimes courses as long as a month are needed. The use of sulfa drugs in pregnancy can cause birth defects. Sulfa drug use can also lead to false positive test results for urine glucose.
Can People or Other Pets Become Infected?
While there are species of Coccidia that can infect people (Toxoplasma and Cryptosporidium, for example), the Isospora species of dogs and cats are not infective to people. Other pets may become infected from exposure to infected fecal matter but it is important to note that this is usually an infection of the young (i.e. the immature immune system tends to let the Coccidia infection reach large numbers where the mature immune system probably will not.) In most cases, the infected new puppy or kitten does not infect the resident adult animal.
Giardia is a flagellated protozoan parasite that colonizes the intestine.
This is a zoonotic problem.
Giardia has a simple direct life cycle.