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Rat Mycoplasma pulmonis Fact
Sheet
Background
Information
Muridae is the family name given to
mice and rats by taxonomists. The order is Rodentia. The genus name of mice is
Mus, the species is musculus and they are Mus musculus. The genus of pet
rats is Rattus species is norvegicus, they are Rattus norvegicus. Roof
rats are Rattus rattus, and are seldom seen as pets. Taxonomy can be
confusing; here is how it works. A number of species makes up the genus,
related genera make up a family. A group of similar families constitutes an
order and a group of similar orders make up a class, related classes make up a
phylum. All phyla that are related make up a kingdom. Rats and mice are part of
Animalia so it goes in order for pet rats:
Animalia, (kingdom), Phylum (related
classes), Class (mammal), Order (Rodentia) Family (Muridae), Genus (Rattus),
Species (norvegicus).
Rats & mice are closely related,
their relationship ends at the genus and species level. Even though they are
different species, this close relationship is why certain diseases that are
considered species specific affect them both!
Acute Disease vs
Chronic Disease
Acute disease is characterized as a
disease of rapid onset, severe symptoms and brief duration.
Chronic disease is characterized as a
disease of long duration that may involve slow changes, with gradual onset. It
may or may not be severe.
Mycoplasma
pulmonis Facts
Murine Mycoplasmosis is the condition caused by Mycoplasma pulmonis
& is the most common respiratory disease of pet rats. When not in the
subclinical stage it is usually a chronic disease. Exceptions are the very
young or very susceptible due to compromised immunes systems, then it may be
acute. It is not curable, but this does not mean it is an immediate death
sentence. With antibiotic treatment it is controllable. Some rats will live a
full and happy life with the disease in control, but usually these rats will
not live to be 3-5 years old, as some rats do.
Mycoplasmas are the smallest known
bacteria that can grow and reproduce outside living host cells. They have no
rigid cell wall, and are pleomorphic organisms. Because there is no cell wall
they were at first thought to be virus, but are now considered primitive
bacteria. Wall-less bacteria are much more difficult to kill because they lack
the lipid layer surrounding them. This is not the same thing as Mycobacterium.
Mycoplasma is a Gram negative aerobic bacteria; whereas, Mycobacteria are Gram
positive aerobic bacteria. The difference between Gram negative and Gram
positive determines the type of antibiotic to use.
In the rat the Mycoplasma may
accompany the Sendai virus or other bacterial infections, such as Pasteurella
pneumotropica, Actinobacillus spp. Streptococcus pneumoniae,
(which we may pass to them) Bordetella bronchiseptica, cilia-associated
respiratory bacillus (CAR) and Corynebacterium kutscheri. What does this
mean to you? Just that M.pulmonis may not be alone in causing
respiratory disease in your rat, it may be more of a combination of bacteria or
in other words a syndrome causing the illness.
Mycoplasma can be identified with an
ELISA test, but most vets won't bother with that because of the expense. Often
times treating it as a syndrome will work well enough for your rat, and if the M.pulmonis
were identified it wouldn't matter because it cannot be cured. Rats and mice
both are the principal natural hosts for Mycoplasma pulmonis. Which
means they are the main carriers of the disease. These other bacteria are also
endemic in rats and are sensitive to the antibiotics your vet will prescribe,
so through treatment with the antibiotics you'll usually manage to keep your
rat living for quite some time. M. pulmonis lowers the resistance of the
rat's immune system allowing these other bacteria that are often opportunistic
to take hold.
How Does Your Rat
Catch Mycoplasma?
It's carried in the upper respiratory
system of rats & mice. Transmission is by direct contact between mother and
babies, aerosol over short distances, sexual transfer, in the birth canal, and
other animal carriers, INCLUDING HUMANS! We are capable of carrying it in our
nasal passages. It is not pathogenic to humans, but WE may infect THEM! Just as
we can pass Strep. infections to them.
Predisposing
factors
Conditions or agents that damage the
protective epithelium of the respiratory tract invite M. pulmonis to cause
illness in your rat. These conditions are, over crowding, poor ventilation, and
high ammonia levels in an unclean cage. Urine and feces raise the ammonia levels
dramatically, this is why it is extremely important to keep that cage
disinfected and ventilated well.
Agents that predispose are other
bacterial infections as mentioned above and the Sendai virus.
Clinical Signs and
Symptoms
The first clinical signs usually go
unnoticed by the less experienced rat owners. M.pulmonis affects three
major areas of the body, the upper respiratory system, the bronchopulmonary
system, and the genitals.
The upper respiratory tract includes
the nasal passages and the inner ear. The first symptom in the upper
respiratory tract is sneezing. Any number of reasons may cause rat sneezing,
such as allergy to poor quality bedding. It is normal for rats to sneeze now
and then as we do. If you are hearing sneezing often and if it responds to
antibiotic treatment, it more than likely is the M. pulmonis causing it.
Other symptoms are sniffling, rough hair coat, and torticollis (head tilt). If
aggressive treatment is not started at the first sign of head tilt, head tilt
can become a permanent condition.
In the bronchopulmonary syndrome
clinical signs are brought on or worsened by high ammonia levels, the bacterial
infections, and /or the Sendai virus. When in this stage it can be a bit more
devastating to them. Signs are lethargy, rough hair coat, hunched posture,
chattering (as in shivering from the chills), weight loss, labored and raspy
breathing, and breathing that sounds congested. Antibiotic treatment at this
point is helpful but they begin a downward spiral that leads to eventual death.
With treatment they may hang on for several months without suffering.
In the ascending genital infection it
causes infertility, small litters, and resorption of embryos. This is how the
mother infects the babies as they pass through the birth canal. It's thought
that tylosin given to the mother while she is carrying the litter may help to
boost the immune systems of the babies, leaving them more resistant to the
disease. The antibiotic does need to build up in the mother's colostrum so that
when the babies are born they get the antibiotic through mama's milk. This is
probably not a reliable method for the breeder of pets, but it couldn't hurt to
try it.
How to Fight it
You can't prevent this disease.
Scientific laboratories are able to produce Mycoplasma free strains, however
that is basically impossible to do with a pet. The only way to stop it would be
for medical science to develop a cure or a vaccine. It could be done but more
than likely won't be done because it wouldn't be economical for the drug
manufacturers.
What you can do is not breed any rats
that are not extremely healthy in the first place. Provide a clean,
well-ventilated home for your rats. Use quality bedding such as Care-Fresh,
Sani-Chips, or aspen. Never use pine or cedar. Feed them lab blocks as the
staple diet with daily servings of fresh or frozen vegetables, cereals, grains,
a small amount of fruit. By starting them out with a nutritious diet they will
build a stronger immune system making them better able to fight off the
disease.
Don't ignore those little sneezes and
that raspy breathing. Normal rat sounds are a variety of squeaks, not
congestion. See a veterinarian when you hear it, don't wait for it to get them
down because once they are down it's harder for them to come back. Don't waste
time or money on the pet store bird or fish antibiotics, they are not going to
help. You need real drugs prescribed by a doctor.
Many veterinarians are not experienced
in treating "pocket pets", try to find one who is.
Home Care
Keep them warm, use a heating pad if
you must, but be sure the cage has a warm side and a cool side. They often
won't eat their regular food so use anything you can find that they'll take.
This can be apple-cinnamon oatmeal, human baby foods, yogurt, chicken soup,
just about anything you would eat if you were sick. Always remember to stay
away from junk food.
Make sure they get plenty of fluids.
You can use Pedia-Lyte, Gatorade, or electrolytes made for animals. Do not let
them become dehydrated even if you have to give fluids with an eyedropper. To
induce them to drink you can add a sweetener to their water or add a salty food
to the diet.
If your vet doesn't give you an
aminophylline drug to open up those breathing passages you can use a couple of
chocolate chips each day. Chocolate is a natural aminophylline and in small
amounts is not toxic to rats as it is to dogs.
If you feed any type of dairy food do
so only if the medication prescribed is not a tetracycline. The molecules of
dairy products compete with the tetracycline molecules and will cancel out the
antibiotic.
Give the sick rat that is on
antibiotics Bene-Bac, an acidophilus product made for animals to keep the
beneficial bacteria in their system that the antibiotics kill. Bene-Bac can be
purchased from vets or ordered from pet catalogs.
Written by Jan
McArthur, RVT
References used:
Microbiology by Tortora, Funke &
Case
The Biology & Medicine of Rabbits
and Rodents by John E. Harkness & Joseph E. Wagner
Ferrets, Rabbits, & Rodents,
Clinical Medicine and Surgery by Hillyer & Quesenberry