|
CANINE TAPE WORMS
|
|
Tapeworms are strings of long
flat segments, the most common is dipylidium caninum, which can grow up
to 70cm in length. Using sharp teeth they attatch themselves to
the gut wall of the dog. They continually produce new segments
that are packed with eggs and which gradually break off, and are
excreted in the dogs feaces. They look like grains of rice and
once excreted are capable of moving like maggots for a short time
before they dry up. Sometimes they become stuck around the anus
which causes some irritation to the dog who will then scoot along the
ground. The eggs of an adult tapeworm need to be eaten by an
intermediate host, in the case of dipylidium caninum this is the
flea. When the dog then swallows the infected flea, the lifecycle
continues. There is a less common type of tapeworm which lies
dormant in the muscle or organs of rodents and rabbits which can infect
dogs if they eat the infected meat.
THE PET
HEALTH LIBRARY
Tapeworms
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 larva pupate.
As the larval flea progresses in its development, the tapeworm inside
it is also
|
Rover
licks himself and swallows fleas
|
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, click here to go to a
special area prepared by the Iowa State Veterinary College: http://www.vetmed.iastate.edu/services/vth/clinical/derm/flea.html
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 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 Dipylidium caninum 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, who need every
calorie
working for them, may show a decrease in performance because of a
tapeworm
infection.
There is another type of tapeworm that may be confused with Dipylidium
caninum and that is the Taenia genus of tapeworms. This is a different
type of tapeworm with a different appearing segment and a different
mechanism of infection.
How do you Know if Your Pet Has Them? 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 , 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 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 reinfect itself. It probably will reinfect 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 who 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.
Copyright
2001 - 2007 by the Veterinary Information Network, Inc. All rights
reserved.
This work was originally published by Veterinary Information Network,
Inc. (VIN)
and is republished with VIN's permission.
The above information is simply
informational. It's intent is not to replace the advice of a
veterinarian nor to assist you in making a diagnosis of your pet.
Please consult with your own veterinarian for confirmation of any
diagnosis. Your pets life may depend on it.
