Tortuga Gazette 39(5): 4-6, May 2003
MYCOPLASMA LADY
Professor Mary Brown
Interviewed by Stephanie Pappas
PART 1
Facts on upper respiratory tract disease in tortoises and turtles are revealed in this exclusive interview with the world renowned scientist, Professor Mary B. Brown, Ph.D. She was part of a team that worked to identify Mycoplasma as the organism causing URTD in 1992. Professor Brown has continued to address new and difficult questions about the effects of this disease on tortoises and she contributes highly valued expertise to many organizations working to save tortoises. The interview took place in Palmdale on January 25, 2003 when Dr. Brown was visiting California and about to be honored by the Desert Tortoise Preserve Committee with the Golden Tortoise Award.
Stephanie Pappas
Dr. Brown, thank you for interviewing with the Tortuga Gazette. As a scientist and tortoise hobbyist, I have been
following your studies on Upper Respiratory Tract Disease (URTD) for several years. I consider you an expert on
Mycoplasma, the organism responsible for URTD and have the utmost respect for your colleagues, Dr. Elliot Jacobson
D.V.M., Ph.D, Dr. Paul Klein, Ph.D, and Dr. Dan Brown Ph.D, all of whom have dedicated many years of their careers to
studying disease transmission in tortoises. Can you comment on these individuals and where this research work is being
done?
Mary Brown
One of the important factors in studying URTD in Gopher tortoises is that this has been a team effort. I happen to be
the person that has the Mycoplasma expertise, Elliot Jacobson has the reptile medicine knowledge, Paul Kline has
the comparative immunology, and Dan Brown has the molecular biology tools. We accomplished what we have because we
worked together, as a team, with each person combining their knowledge. We learned from each other and the team learned
more together than we would have as individuals. Primarily, all the individuals I mentioned are currently working at the
University of Florida. However, we have trained many individuals over the years that are now at different places doing
similar work on the Gopher tortoise.
Stephanie Pappas
Dr. Brown, you mentioned that most of your disease work at the University of Florida is being done on the Gopher
tortoise, are you currently doing any studies on the desert tortoise (Gopherus agassizii)?
Mary Brown
An upper respiratory tract disease in Gopher tortoises is caused by the same organism, Mycoplasma agassizii (M.
agassizii) as URTD in the desert tortoises. Many of the things we learn from the Gopher tortoise help the California
desert tortoise, and vice versa. In fact, we just received a grant from a special joint program administered by the
National Institution of Health and the National Science Foundation called the Ecology of Infectious Diseases. This
five-year study will focus on factors that impact the severity of disease transmission in wild populations of the Gopher
tortoise. The major factors we will examine will be microbial virulent factors (which means how the bacteria makes the
animal sick and how the animal responds) and human impact on the habitats. We think this study on the Gopher tortoise
will assist in determining the cause of deaths and decreased reproduction, and tell us how it effects different sexes,
males versus females. The study of Gopher tortoise will also give clues as to what is happening with the California
desert tortoise.
Stephanie Pappas
For many years, I have heard a rumor that URTD originally spread in wild tortoise populations because someone released a
captive desert tortoise back into the wild population and that tortoise was carrying a domesticated disease, now known
as URTD, caused by M. agassizii. Do you believe this is a true fact?
Mary Brown
No, I believe that there is a lot of speculation and no scientific data. Clearly where you have captives released ,you
have a high prevalence of disease. Obviously, if you release a sick animal, you do not know where the disease
originated. We have seen M. agassizii disease in Gopher tortoises, Desert tortoises and Box turtles in wild
populations. For the most part, M. agassizii tend to be host specific. That means that a specific Mycoplasma
that will infect a cow will not infect a goat. Think of it as having a limited range of animals that a single
Mycoplasma species can infect. From that stand point, you would not expect the organism to arise from a pet dog, but
most likely evolved to fit inside the host, the tortoise. Mycoplasma lives very close to the host; these
organisms do not survive in the environment very well, as a result, they developed a very close attachment to the host
nasal surface.
Stephanie Pappas
How do scientists know this?
Mary Brown
There are ways to test the hypothesis, and the more clinical isolates we have, the more we can determine using molecular
tools. Molecular Epidemiology is a fancy way of saying we are going to look at what kind of chromosomes and genes there
are to trace the history. The problem is, in evolution terms, that period evolved very quickly. OH, NO, this is going to
be too complicated!
Stephanie Pappas
Can we simplify this for our readers?
Mary Brown
What I mean is, if the disease started five years ago it would be easier to track. The fact that we first saw this
disease 20 years ago means that too much time has passed and now it will be very difficult to determine exactly where it
originated. The important thing is not where it originated, but how do we contain it and prevent more disturbances in
the desert tortoise populations. The best way to contain and prevent the disease from spreading is NOT TO RELEASE
CAPTIVE TORTOISES. Captive tortoises that have URTD can survive for a long time, because the owners provide good care of
them and get them medication when clinical signs appear. The medication will not cure the disease, but will eliminate
the clinical signs. The bottom line is if you have captive tortoises, please do not release them! Another thing,
Mycoplasma is only one potential infectious agent causing clinical signs of URTD 's. One we know about! There may be
other infectious agents out there that we do not know about yet, therefore, you do not want to risk spreading new
disease to native, wild populations of tortoises.
Stephanie Pappas
Dr. Brown, obviously tracing the origin and history of the disease is quite complicated! So let 's move onto how the
etiology of this disease, M. agassizii, was discovered. Can you explain what etiology means to our readers?
Mary Brown
Etiology is a fancy way of saying what it is that makes the animal sick and causes the disease. There is a very defined
scientific way to determine this. It 's called Koch's postulate. To prove Koch's postulate, you find a sick animal and
isolate an organism. You put the organism that you isolated from the sick animal into a healthy animal, induce the
disease, and then get the organism back out of that animal. Basically, we have fulfilled Koch 's postulate in both the
Gopher and the desert tortoise confirming that M. agassizii causes URTD. What we are finding now is that we may
have a complex of several very closely related Mycoplasma that may be responsible for respiratory disease; it may
not just be M. agassizii. We have fairly good evidence that there is at least one additional organism,
Mycoplasma cheloniae, that maybe involved in causing respiratory disease in tortoises. Mycoplasma respiratory
disease is very common, it causes respiratory disease in humans, chickens, turkeys, pigs, rats, mice, goats, and cows.
Stephanie Pappas
Are these Mycoplasma strains interchangeable from animal to animal?
Mary Brown
No! They are unique species and each animal has it 's own Mycoplasma. It 's kind of an unhealthy marriage I
suppose!
Stephanie Pappas
Dr. Brown, earlier in this interview you stated that M. agassizii has been identified in California desert and
the Florida Gopher tortoises, as well as box turtles. Have any other wild populations of turtle or tortoise species been
studied?
Mary Brown
No! The only studies that have been done are on wild animal isolates in these three species of tortoises and turtles.
The other information we have on M. agassizii in tortoises is from Zoo's or private collections where we have
isolated the organism or screened for positives.
Stephanie Pappas
So, the tortoises have this unhealthy marriage with these bacteria that they are carrying around for life. How did this
unhealthy marriage of reptile and bacteria evolve?
Mary Brown
The main question is why would these bacteria colonize in reptiles and not in many other species of animals? This is a
difficult and interesting question and we do not know the answer, but we have a hypothesis that explains it. If you look
at how animals evolved, reptiles are very old, and birds come along and then mammals. What we think is happening is that
the animals earlier in the evolutionary chain do not have a lot of differences on their surfaces. As a result, bacteria
may not have to develop a specific recognition protein. Bacteria attach very closely and tightly on the surface and they
do this using a special recognition, called a receptor protein. Think of it as a lock and key, like your luggage lock,
where you have one key that fits several brands of luggage. Reptiles have a simple lock where it only takes one key to
fit many different species. So that is why M. agassizii can colonize in a number of turtle and tortoise species.
Stephanie Pappas
Several years ago, I recall reading that until proven otherwise, all species of tortoises and turtles should be
considered susceptible to Mycoplasma. Exactly how do tortoises and turtles transmit this disease to one another,
and what can we do as turtle and tortoise owners to prevent the spreading of URTD among our personal collections?
Mary Brown
The first and foremost ways that Mycoplasma spreads for all species is aerosol contact and direct nose to nose
contact.
Stephanie Pappas
Is that what is meant by horizontal transmission?
Mary Brown
Horizontal transmission means from one animal to another. Vertical transmission means from mom, through the egg, to the
hatchling. We know Mycoplasma can be spread by direct contact and we think it can probably be spread over short
distances if the animal sneezes and leaves mucus droplets. We also have fairly good evidence that if an animal is
clinically ill (showing active symptoms of nasal and ocular discharge, a runny or wet nose and eyes) that is the time
the disease is most likely to be transmitted, because there is a lot more Mycoplasma present in the secretion. In
order to get an infection you have to have a certain number of organisms that come in contact with a susceptible animal
and those Mycoplasma have to be able to attach to a host, the tortoise nose surface. Once these organisms attach,
they establish themselves and continue to multiply and grow. When the animal is not showing clinical signs, the numbers
of organisms are relatively low and you have more difficulty culturing the organism. When the animal starts to show
clinical signs, the number of organisms and the ability to recover them by culture goes up dramatically. Furthermore,
this is when Mycoplasma is readily transmissible. Therefore, my advice is, if you have a tortoise or turtle
showing clinical signs you should quarantine that one from all others. And never, ever mix species of turtles and
tortoises because you may run the risk of spreading the disease throughout your entire colony, or collection of
tortoises and turtles. The best thing to do is not house your turtles and tortoises together. In any kind of infectious
disease situation regardless if it is Mycoplasma or any other disease, we know that crowding increases the
chances of transmission. Transmission is the function of many conditions: of how many organisms are present; how many
times you come in contact with an animal that is carrying the organisms; and how long the organisms may survive on your
hands, the feeding areas and water bowls or the surface area and the enclosure where your animal is living. Fortunately,
Mycoplasma is very susceptible to disinfectants. Bleach solution works very well. Get disinfectant hand soap and
wash your hands several times. This will help between handling turtles and tortoises.
Stephanie Pappas
Actually, that was going to be my next question, what are the best disinfectants to use and can you transmit the disease
on your shoes when moving from one enclosure to another or from your hands when touching several tortoises and turtles
in a given period of time?
Mary Brown
Well, we certainly take precautions against it because if you do not know for sure you always want to err on the side of
extreme caution. For example, when we go out into the field, we use bleach on all of our equipment and on hands between
every animal. We also use gloves between each animal we touch. Don 't take the risk. It 's always better to go overboard
on caution than it is to put the Genie back in the bottle after you have let it out! The bigger problem is that
Mycoplasma is only one infectious agent. Of even greater concern are viruses that are more resistant to certain
types of disinfectants. Bleach is one of the agents that get almost all types of viruses and most effective.
Furthermore, it 's cheap but it is rough on your clothes! The other concern with bleach is that when you open and close
a concentrated bleach bottle, it will loss its effectiveness and concentration so if you buy large bottles divide it
into smaller bottles that are opaque so that light cannot get through or purchase smaller bottles. Not all commercial
bleaches are the same. You want a concentration that is about 5.5% sodium hypochlorite; and dilute it 1:30, one part
bleach and thirty parts water and use that as your disinfectant. Another thing you can do is always work with your
healthy animals first and then handle your ill animals and that way you minimize the possibility of tracking anything
in.