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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
(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. 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
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
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.
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 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.
Treatment
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.
A new product, called Revolution, will kill fleas, heartworms, ear mites, and even internal parasites. Please ask our receptionist for a brochure.
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. Some pets will itch at their
anus when the worms cause irritation as they pass.
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. Proper flea control does.
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. 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.
Roundworms
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.
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 (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.
Symptoms
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.
Diagnosis In some cases the Roundworm will be present in your pet's feces or vomitus. 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. 
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. Some pets require several more
treatments for a full cure.
Prevention 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
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
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.
Symptoms 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.
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
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. 
Treatment 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.
Prevention 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
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.
Life cycle 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. 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.
Treatment 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.
Prevention 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
Coccidia
are not technically a worm, but a protozoan parasite that infect dogs
and cats primarily, but can be seen in other species.
Life cycle
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
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
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.
Treatment
Sulfa type medications or sulfa and antibiotic combinations are used to
affect a cure. They need to be given for up to 3 weeks. Kittens that
are very ill require hospitalization and intravenous fluids to help them fight off the infection.
Prevention
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
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 underdiagnosed 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 intetstinal lining they let in proteins that
stimulate the immune system to cause an allergic reaction.
Life cycle
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.
Symptoms
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.
Diagnosis
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.
Treatment 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.
Prevention
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. 1. Treat all in contact animals in the household.
2.
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).
3.
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.
4. 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.
5.
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.
6.
Thoroughly clean food and water dishes daily with soap and hot water
and sterilize the food and water
dishes weekly.
7. 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.
8.
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.
9. 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 availabe 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
nasuea. 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 contaminted 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.
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