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Transverse section of raccoon first premolar. The thin section was cut from the intact tooth, without prior treatment, and mounted on a microscope slide. Microscopic examination with illumination by ultraviolet light reveals two fluorescing layers induced by tetracycline administration.
is administered to the animal either by injection or in
treated food. Action of the drug results in the formation
of an altered tissue layer in tooth and bone. This "biomarker"
can be seen in thin, calcified tooth and/or bone sections
viewed with a fluorescent microscope.
presence of biomarker is determined by studying the laboratory
preparation, a thin section of calcified tooth or bone.
The sectioning is done with a specially equipped saw, and
the sections are permanently mounted on a microscope slide.
of field collection, preservation, and shipment for analysis
are described in the "Preparation
of specimens..." and "Shipment
of specimens..." sections of this site.
POPULATION SIZE. The technique has been used as
a "mark-recapture" tool to estimate black bear
population size (Garshelis, D. L., and L. G. Visser. 1997.
Enumerating megapopulations of wild bears with an ingested
biomarker. J. Wildl. Manage. 61:466-480). Conditions necessary
for successful application of the technique are discussed
in the paper: "The data from Michigan demonstrate that
for megapopulations of 5,000 or more animals and annual
harvests near 15%, about 200 marks (roughly 600 baits) are
necessary to generate an estimate having 95% confidence
intervals within 25% of the estimated population size..."
EFFICACY OF VACCINATION OR CONTRACEPTION. Baits
contain tetracycline as well as vaccine or contraceptive.
After broad-scale application of baited treatments, efficacy
is evaluated by examining teeth and/or bone from animals
taken within the treated area.
POTENTIAL APPLICATIONS include animal identification.
For example, if a method of mass administration were feasible
for cloven hoofed animals (e.g. dosage via treated feed)
then a group could be "marked" to detect DISPERSAL.
In animals captured for RESEARCH, the permanent biomarker
may be useful as a supplemental or substitute identifier.
If recapture takes place during summer and after a long
enough interval (approximately a month), multiple biomarkers
will be detectable. When the tooth is large enough (bear
premolar, raccoon canine) a biomarker can sometimes be dated
by determining the cementum age at the time it was formed.
TETRACYCLINE DOES NOT INDUCE
FLUORESCING BIOMARKER IN HAIR.
Specimens: Seven hairs from Maine raccoons that
had tested positive for tetracycline biomarker, and one
hair that tested negative, were analyzed to detect the presence
of tetracycline fluorescence.
methods: Hairs from 8 raccoons were whole mounted
in glycerine jelly on microscope slides. Care was taken
to include the hair root bulb with each mount. The slide
mounting method used was the same used by Matson's for tooth
sections to be examined for tetracycline biomarker. Whole
mounts were examined under the fluorescent microscope, using
the standard tooth section analysis procedure.
No part of any hair in any of the 8 specimens showed tetracycline
Tooth sections from 7 of the animals had recent biomarkers
(formed within the past 4-8 weeks). If tetracycline or any
fluorescing by product was incorporated at all into the
hair, fluorescence should have been observed because hair
elements present in the specimens were being formed at the
time of tetracycline ingestion.
Tetracycline ingestion does not produce a visible fluorescent
biomarker in hair.
calcified tissue reaction with tetracycline produces a clearly
visible mark only during the season of most rapid growth.
In late fall, winter, and early spring cementum growth is
much reduced and there may be no induction of visible biomarker.
chief reason that attempts fail with biomarkers is inadequate
dosage. Evidence suggests that a dosage of 20mg/Kg is ample
to induce a clearly visible mark. Adequate dosage has been
achieved in studies of black bears by embedding tetracycline
capsules inside a 2-lb chunk of bacon. However, attempts
to administer adequate tetracycline to ungulates by treating
pelleted food have not been successful because the treatment
appears to render the food unpalatable. Syringe injections
may be effective, but the injected volume is large. Attempts
to inject tetracycline by a dart-gun syringe have not been
successful. The efficacy of multiple, simultaneous dart-gun
injections may deserve consideration and study.
black bears, the old animal may not reveal a biomarker even
if it received an adequate dosage. The rate of cementum
production in the old animal is greatly slowed, and may
not be great enough to incorporate the amount of reactive
material necessary for a clearly visible mark.
is also induced in bone but, unlike tooth, remodeling may
result in complete loss of the biomarker in 2-3 years.
an ADEQUATE DOSAGE of tetracycline during SUMMER.
PM1 tooth in bears is an acceptable specimen for biomarker
screening, but the third incisor (I3) and canine are larger
and may have greater biomarker visibility.
compensate for the potentially inadequate biomarker induction
in old bears, collect a segment of rib bone along with the
tooth. The bone may contain a more clearly visible biomarker
until 2-3 years after induction when it is lost because
of normal bone remodeling processes.