Tortoise Upper Respiratory Tract
Disease and why it is important that we support the staff at the Desert
Tortoise Conservation Center.
There has been quite a bit of chatter
about the Desert Tortoise Conservation Center and their tortoises. I think it
would be helpful for people to research what the DTCC does on a daily basis.
Their blog http://blogs.sandiegozoo.org/tag/san-diego-zoos-desert-tortoise-conservation-center/
would probably be a great place to start. Not only are they housing
displaced tortoises, they are also trying to address critical research needs, which
range from animal behavior to disease ecology.
I feel compelled to get some of this
information out there in hopes of helping the public understand what is going
on. I am writing from my experience with
the gopher tortoise, and I am in no way affiliated with the DTCC. I have, however, spent some time in the
desert, and I have interacted with the staff a number of times and have seen
their work presented at scientific conferences.
So what? The tortoises just have a “cold”!
This is not as simple as some are
making it sound. The primary disease we generally associate with our North
American tortoises is Mycoplasma-induced Upper Respiratory Tract Disease
(URTD). However, there are a suite of other pathogens that might be
impacting health and causing clinical disease, including herpes, ranavirus, and
fungal infections (the list goes on!). My research experience is with the
gopher tortoise (Gopherus polyphemus),
a species in the southeastern United States.
However, the effects of the disease are similar to those in the desert
tortoise.
External clinical signs include, but
are not limited to, nasal exudate (clear to thick mucus, i.e., runny noses);
weeping,red swollen eyes; encrusted or
sealed eyes; labored, wheezy breathing; lethargy; etc. In some cases these clinical signs
can be temporarily relieved, but in most cases clinical signs return. Some
tortoises get runny noses so often that the moisture actually scars their nares
and erodes the skin. Tortoises with chronic, weepy eyes might even get white
rings around the eyes over time as well. Therefore, it is inhumane to release
these tortoises into the wild (and dangerous to healthy animals in the wild) or
place them in captivity with inexperienced handlers.
Note the loss of pigment between the nares (nose holes) of the
tortoise on the left. The tortoise on
the right really needs no explanation as this tortoise has thick mucus discharge
from the nares.
The signs we can't see are the internal
effects of disease. An important part of what the DTCC is doing is documenting
these effects. Tortoises that experience recurrent clinical disease may have increased lung tissue scarring over time,
resulting in a decrease in lung function. In my experience with gopher
tortoises (Gopherus polyphemus) with URTD, infected individuals are
emaciated and have minimal fat tissue; this reduced fat might make it difficult
for tortoises to get through colder months and could decrease fitness. The
nasal cavity is often scarred and eroded,(which might decrease their sense of smell).
We also find mineral deposits, such as bladder stones, which might create a
blockage. There are still many things that we don't know about these
diseases or even how findings from necropsy relate to health. I am sure there are a number of pathogens
still left to discover!
Why can’t they just release all of the tortoises? Why are they being so strict about who can
adopt?
My next point pertains to releasing
pets. The origins of many tortoises in captivity are unknown (are they collected
from the wild? Bred in captivity?). There are hypotheses out there that some of
the disease we are seeing in our native tortoises (such as the desert tortoise and
gopher tortoise) is due to exotic tortoises being released into the wild;
however,this hasn't been proven. For
example, our native tortoises may have been exposed to new pathogens from other
countries through imported animals. That being said, how many times do we hear
reports of a tortoise or turtle that has escaped from the yard? I constantly get calls about “sulcatas” being
found: this is the African spurred tortoise (Geochelone
sulcata). There is no telling what conditions these escapees were kept in
or what pathogens they were exposed to in captivity. It is not uncommon for
people to keep different species of chelonians together. This poses a real
threat to our free-ranging chelonians should pets be released. The amphibian
decline due to the chytrid fungus, Batrachochytrium dendrobatidis, comes to mind. I am not
going to go into ranavirus or herpes, both of which are growing concerns,
especially for box turtles (Terrapene
carolina). There is currently no
cure for URTD. With the help from an
experienced veterinarian, the clinical signs from a bacterial infection (such
as from Mycoplasma sp.) can be
alleviated, but the tortoises will usually get sick again in the future. This kind
of care might be reasonable for a responsible pet owner, but will not be
possible for tortoises that are released in the wild.
When the DTCC is reporting that a
tortoise is sick, I have every confidence that they have done the best that they
could to evaluate the fitness of the individual for release. The people
at the DTCC are passionate and love the tortoises. URTD is not much different
than pneumonia in humans. Similarly in humans, the severity of disease can vary
among individuals. This ability to recover from disease can vary due to age,
stress, history, co-infection with other unknown pathogens, etc. What is
so concerning about URTD, particularly in free-ranging animals, is that we still
know so little. The DTCC is on a mission to answer some of the remaining
questions. URTD can be as simple as a pesky, lingering “cold” for some
tortoise or it can lead to death. In fact, tortoises might suffer with severe clinical
disease for months before dying: envision an emaciated, nearly blind,
runny-nose tortoise wandering around.
It’s disturbing and it is inhumane to release it to the wild. Imagine
the other animals this tortoise might come across in its aimless, disoriented
wandering!
This is a tortoise that I was
tracking as part of my dissertation work. You can see the transmitter epoxied
to the carapace. Note the swollen eye and
snotty nose. This tortoise was out
wandering in habitat that was not suitable for tortoises.
There are a number of things that we
need to do to help the plight of our North American tortoises. We need to
educate the public about the effects of taking tortoises out of the wild. We
also need to encourage people not to release pets into the wild under any
circumstances. There are networks of organizations out there that will
take these pets, and we need to make the list of organizations easily available.
If you are a local organization that will take unwanted pets, is your local
animal officer aware of this? Is your state wildlife agency aware of your
specialization with herptiles? (be sure to have the proper permits). We need to
spread the wordthat unless the exact location where the animal was found is
available, it should not be released, especially in cases of tortoises with
signs of illness. This decision should rest with the state agencies. We need to
act responsibly, and although the outcome might be sad for the individual, our
objective should be to protect the
species.
I hope this provides clarity
regarding the issues of disease and releasing tortoises. This is a
complex problem that needs attention.
For more information, please visit the Southeastern Partners in Amphibian
and Reptile Conservation Disease Task Team website to learn more about disease:
http://www.separc.org/products/diseases-and-parasites-of-herpetofauna For more information about the gopher
tortoise, visit the Gopher Tortoise Council main page: http://www.gophertortoisecouncil.org/. The Desert Tortoise Council also has a page
and can be found at http://www.deserttortoise.org/
Disclaimers: I am in no way
affiliated with the DTCC but I am familiar with their work. I have been
researching URTD in the gopher tortoise, but not in the desert tortoise. The
opinions expressed in this blog are my personal opinions and observations.
Jess Gonynor –McGuire, PhD
Wildlife Biologist
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