Although healthy reptiles in the wild tend to harbor high numbers of
internal parasites, we as caretakers like to make an ideal environment for
our pets in captivity, so any potentially harmful internal parasites should
be eliminated. Parasites can live in many different parts of the body,
including the eyes and brain, but here I will discuss some of the more
common reptile parasites that inhabit the digestive tract which can be
identified upon fecal examination.
When you take a fecal sample to the vet, have you ever wondered what
they do with it and how they identify the parasites that may be inside your
pet iguana? There are many different types of fecal tests that are used
today, with certain tests being more appropriate to identify certain
parasites. The two most commonly performed tests are the "Fecal Float" and
"Fecal Smear". Most vets will perform one or both of these tests when you
present them with your pet’s fecal sample. Some parasites, particularly
smaller one-celled protozoa, do not show up well using the fecal float or
smear techniques, but can be identified using other methods such as the
"acid fast" test. Sometimes cloacal or stomach smears or flushes can be
performed as well, but these procedures should only be attempted by a
veterinarian or other specially trained person. For the sake of simplicity,
I will only discuss the Fecal Float and Smear on this page.
The Fecal Float
This test is more helpful when trying to find the larger parasites, such
as nematodes. The idea is to take a small amount of feces, mix it with a
solution, and allow the nematode eggs to float to the top. These eggs can
then be collected by placing a slip cover over the top of the solution and
then placing that side of the slip cover face down onto a slide. The
solution many vets use to dissolve the feces in is Sodium Nitrate, but a
fully saturated sugar water solution will work as well.
The Fecal Smear
This test is used more often to find parasites that are too small or do
not float well enough to collect using the Fecal Float method. The Fecal
Smear is prepared by taking a small amount of feces, putting it onto a
slide, and mixing it with a few drops of saline or other solution. Then
place the slip cover over the slide to observe under the microscope.
How to Prepare a Slide
The first thing I do when I am going to perform a fecal test is wash my
hands thoroughly. Never touch the feces directly with your hands. Use a
toothpick or two toothpicks to get a small sample of fecal matter.
Put the feces onto a clean, white, thick paper plate. Never allow the
feces to touch any other object. When you are done with the fecal tests,
throw out the entire plate and toothpicks and wash you hands thoroughly
again, even though you have taken special care not to touch the feces.
After you put the feces onto a thick paper plate, observe them closely
with your naked eyes. You may see worms already. If you see some thin,
white worms that are about 1-2 inches (or more) long, these could be
roundworms. Roundworms (and many other parasites like Cestodes(tapeworm)
and Trematodes (flukes)) tend to be found in *carnivorous* reptiles.
Animals infected with these parasites need to ingest an intermediate host
of some kind, like a mouse or fish, bug or snail, etc. I will try to keep
this discussion centered on parasites with direct life cycles that do not
need an intermediate host, since these are the parasites that iguanas and
other vegetarian reptiles are more susceptible to.
If you watch the feces for about one minute and see no worms, take two
toothpicks and "open up" a piece of feces. Take a close look inside, do you
see any very tiny, thin, white worms that look like a thin piece of thread
that is 2-3 millimeters long? If you see anything suspicious, put it onto a
clean, dust free slide for further observation. If you see any other tiny
2-3 mm long threads, put them on the slide with some space between them.
Sometimes these thin threads will be Strongyloid worms, and sometimes they
will be vegetable fibers. Be very gentle so as not to break apart the
"thread" as you coax it out. If you are very gentle and the "thread" still
breaks apart, it is probably not a Strongyloid worm.
Now take a tiny amount of feces and smear it gently onto any
remaining area on your prepared slide, away from the area you have placed
your suspicious "threads". With a CLEAN eyedropper, place a few drops of
saline solution onto the slide. You do not want to put so many drops that
it will overflow when you place the cover slip over the slide. In case
anything does drip off the slide, it is a good idea to keep the slide on
the paper plate until it is completely prepared and ready for viewing under
the microscope. Place a drop or two of saline solution over the "threads"
on your slide too. Now place the cover slip over the slide, and place it
onto the microscope.
Looking for Nematodes
It is easiest to start viewing with the lowest magnification, which is
usually the 4x Objective Lens. This will give you a magnification of 40
times. This lens should be clearly marked on your microscope, so you will
know which lens is the 4x Objective. Use the coarse and fine focus to bring
your slide to a sharp image. I like to start at the lower left hand corner
of my slide and move from left to right to view the entire slide
thoroughly. This way, I know I am not missing any areas of my prepared slide.
As you view your slide, you may see some very interesting things. If
you look at one of the "threads", you will know immediately if it is a
worm. It may even be moving quite a bit which will tell you for sure it is
a worm of some type, probably a strongyloid. Here is a picture of a
strongyloid nematode for comparison, 4x Obj. lens used:
This is a picture of a vegetable fiber. Notice how it looks very
different from a worm, even though with the naked eye they looked the same!
4x Obj lens used.
Here is a picture of a carpet fiber. Do not mistake these or other
foreign objects for nematode worm or larvae. 4x Obj. lens used.
If you search the entire slide and do not see anything, try moving up
one higher magnification by switching to the 10x Objective Lens to get 100x
magnification. At this magnification, you should be able to see nematode
eggs easily. Picture of nematode eggs using 10x Obj, lens.
Sometimes you will see eggs developing inside a female nematode. 4x
Obj. lens used.
Be careful not to mistake air bubbles for nematode eggs. An egg with
have something developing inside it, but an air bubble is usually empty.
Here is an air bubble for comparison.
NOTE: One of the most common nematode parasites in iguanas is
Strongyloides spp. I have seen these parasites in *every* green iguana that
has not been previously treated for internal parasites. Other common
nematode parasites in iguanas include hookworm, pinworm, and lungworm. They
all have an oval shaped egg, and can all be easily seen with the 10X Obj.
Hookworm and Pinworm egg photos coming soon.
Dosages for Nematodes
Before you attempt to give your iguana any kind of medication for
internal parasites, you will need to get an accurate scale, as all
medications are based on weight. NEVER guess the weight of your animal, and
be extremely careful when calculating the amount of drug. It is very easy
to make a mistake with a decimal point and give you iguana ten, or even one
hundred or more times over the recommended dose. If you are the least bit
unsure about the dose, consult your veterinarian for advice. Panacur and
Flagyl are both safe drugs and can be given many times over the recommended
dose without many problems, however overdosing is always a concern you
should have. ***If you are administering a drug to your pet, ONLY YOU can
be responsible for the outcome.***
Klingenberg recommends nematodes to be treated with Fenbendazole (brand
name Panacur or other) at 25-50 mg/kg orally every 7-10 days for three
weeks. Perform another fecal exam after three weeks to make sure there are
no nematodes left. For some nematodes, you may even have to do two follow
up fecal exams to be extra sure there are none left. See references at
bottom of page for more details.
NOTE: Contrary to popular belief, Panacur does not "kill" nematode worms.
It affects the adult worms by encouraging them to release their hold on the
intestinal wall and thus to leave the iguana’s body in the feces. The worms
are still very much alive and have the ability to re-infect the iguana, or
infect other iguanas. Some nematodes, like Strongyloides, Hookworm, and
Lungworm, can enter their host via the skin, so take special care to not
leave ANY fecal matter in your iguana’s cage even after giving Panacur, and
do not allow any uninfected animals near your iguana. Panacur has also been
known to have a sterilization effect on adult worms*, however in my
experience, adult female worms would still produce many eggs even after
Looking for Protozoa
The most common internal parasites of an iguana can be divided into two
major groups. We have already introduced the NEMATODE group. The second
group of common internal parasites for iguanas is PROTOZOA. These are
single celled eukaryotes and much more simple in function than the
nematode. There are many types of protozoa, and these can be difficult to
identify from one another and take more practice. They are generally much
smaller than nematode eggs, with some exceptions.
Balantidium are one of the easiest protozoa to identify. They are
quite active and easy to see with the 4x obj lens. These are ciliated
protozoa that reproduce by fission. Every book on reptile parasites seems
to have a different opinion as to how pathogenic Balantidium are. My
opinion is these parasites are generally not a problem, and Balantiduim
seem to be difficult to pass on to other iguanas. I personally know some
iguanas that have lived for over 5 years with a Balantidium-infected
iguana, and have never tested positive for the Balantiduim themselves. The
iguana with Balantidum has grown normally and even lay eggs every year
without problems. Balantidium is not so common in iguanas, but I have seen
them in fecal exams before. Usually, tortoises tend to be infected with
this parasite. If you choose to treat Balantidium, Barnard and Upton
recommend 125 mg/kg Metronidazole (brand name Flagyl or other) orally every
day for three days, followed by tetracycline orally for 5-8 days at 25-50
mg/kg. Please see references below for more details.
Ameobae are more difficult to identify than Balantidium, but are much
more common. You can see them with the 10x Objective lens, but they are
extremely tiny. Try using the 40x Objective lens to get 400 times
magnification. The movement of these protozoa is smoother and not jerky
like the flagellate. They do not swim all over the place and leave your
viewing screen area like Balantidium. They tend to "turn" in their movement
and the single cell sometimes looks like a cat or other animal that is
trying to get out of a bag. They move slower than flagellates and are
easier to follow, even in an active individual. Barnard and Upton recommend
treatment of 125 mg/kg Metronidazole (brand name Flagyl or other) orally
every day for three days.
Flagellates are perhaps the most common protozoa of all, and almost
every iguana will have these protozoa, unless perhaps they have been given
antibiotics for a prolonged period of time. Unlike Ameoba, these are
generally not a problem in most reptiles, and there are some sources that
feel these protozoa may have a symbiotic relationship with the iguana, and
aid the animal in digestion. See references below for more infomation and
then form your own opinion.
Although in a still picture a Flagellate looks very much like Ameoba,
their movement is quite different. You will need a very fresh fecal sample
to see their movements, and once they die, they can be difficult to
identify. Using Lugol’s iodine or other stain may help to highlight protozoa.
Unlike ameobae, flagellates move in very jerky, fast motions. They look
like someone has given them an electric shock. Do not try to see the long,
thin flagellum, as they are impossible to see in an active specimen using
the 40x Obj lens. The flagellum move too fast. Flagellate picture using 40x
Giardia, Coccidia, and other protozoa pictures coming soon.
There are many other types of internal parasites that can infect an
iguana, but are less common. It would be impossible to list all of them
here. Depending on what they have been fed in the past, some newly obtained
iguanas may have roundworm, tapeworm, or other nematodes that tend to be
found in carnivorous reptiles. Check with your veterinarian if you are
unsure about what you are seeing. Never administer medication unless you
are absolutely sure you have identified the correct parasite and are
treating it accordingly.
*Klingenberg, Roger. 1993. Understanding Reptile Parasites.
Barnard and Upton. 1994. A Veterinary Guide to the Parasites of Reptiles.
James Smyth. 1995. Introduction to Animal Parasitology.
Copyright(c)1999 Marie EGURO