Internal Parasites (Worms)

Introduction

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 are routinely infected with internal parasites, sometimes without apparent evidence of the infestation until it is too late. Fortunately, we have sophisticated diagnostic tests and 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.

This section will discuss internal parasites that are commonly found in dogs and cats in our area. 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

Symptoms manisfested by pets that are infected with internal parasites can vary depending 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 an 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.

Diagnosis

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 is should be kept cool until we analyze it. Analysis should be within 12 hours to increase accuracy.

 

 

This picture shows you how to obtain a proper sample. You only need a small amount of feces in the bottom of the container.

 

The flotation solution has been added and a cover slip has been placed on the top to collect any eggs that float to the surface after a 5 minute wait.

Treatment

Internal parastites 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 lifecycles 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 pets feces periodically and to use medication on a long term basis.

Tapeworms

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.

Life cycle

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.

 

Symptoms

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

Diagnosis

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.

 

Treatment

Several medications are available that are highly effective at ridding you pet of Tapeworms. The most common treatment is an injection that rids your pet of all Tapeworms within 24 hours. It does nothing to prevent your pet from re-infecting itself.

Prevention

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.

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.

Roundworms

A common parasite of dogs and cats, especially puppies and kittens is Roundoworms.. The scientific name for their group is called Ascarids. We routinely treat puppies and kittens for this parasite for 2 reasons. The first reason 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.

Life cycle

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, 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.

 

Symptoms

Common symptoms are a distended abdomen and diarrhea. Some puppies and kittens will be lethargic and not eating well, while others will not show any symptoms.

Diagnosis

In some cases the Roundworm will be present in your pet's feces. It looks like a curled up piece of spaghetti. The vast majority of Roundworm infestations are diagnosed on fecal analysis for eggs.

This is one type of roundworm egg, called Toxacara????, when viewed under the microscope. The thick membrane around the eggs prevent them from drying out when they are layed in the environment.

Treatment

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.

Prevention

Roundoworm 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 pets 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.

Hookworms

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.

Life cycle

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 an kittens can also get infected while nursing.

 

Symptoms

Pets with Hookworms have the potential to be very ill. Usually 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.

Diagnosis

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 pets feces.

These eggs are more oval than Roundworms, and the membrane is thinner.

 

 

Treatment

Infected pets might require hospitalization and even a blood transfusion. Many will have bloody diarrhea. There are different types of worming medication used. All require checking your pets feces to make sure the parasite has been eliminated. Long term treatment and surveillance in the form of fecal exams are necessary.

Prevention

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People can be infected by the larvae that penetrate their skin, especially between the toes when walking barefoot in heavily infested areas.

Whipworms

Whipworms are blood sucking parasites that live in the large intestine. 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.

Lifecycle

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

Symptoms of Whipworm infestation include chronic diarrhea, anemia, and weight loss.

Diagnosis

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.

Adult Whipworms can sometimes be visualized when an endoscope is passed into the rectum of a pet with chronic diarrhea.

Treatment

Various oral medication are also use to treat Whipworms.

 

Prevention

Control of reinfections is difficult because eggs that have been layed in the environment are very resistant. Feces need to be rechecked and a long term plan for surveillance and treatment needs to be initiated.

Coccidia

Coccidia are not technically a worm, but a protoazoan parasite. We encounter them in cats

Life cycle

Symptoms

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

Diagnosis

Most Tapeworms are diagnosed by visualizing the worm in your pets feces or crawling around its anus. TThey 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.

Treatment

 

Prevention

Giardia

Giardia are also protozoal parasites that live in the small intestines.

Life cycle

Symptoms

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

Diagnosis

Most Tapeworms are diagnosed by visualizing the worm in your pets feces or crawling around its anus. TThey 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.

Treatment

 

Prevention