Melissa
Kaplan's
Herp Care Collection
Last updated
January 1, 2014
Dystocia in Reptiles
Egg-Binding / Fetal Retention
©1995, 2001 Melissa Kaplan
Dystocia is a relatively common malady in reptiles, occurring in lizards, snakes and chelonians.. There are many different causes, and in most cases, the cause goes undetected. DeNardo (1995) states that in his experience, dystocia occurs most often in first-time breeding females, females who have previously retained eggs, and female bearing infertile clutches. Dystocia can occur in live-bearing and ovoviviparous species; these are less common perhaps only because at this time there are fewer such species being bred in comparison with oviparous (egg-laying) species.
One general cause of dystocia may be due to the inability of the eggs to pass through the oviduct and cloaca. There may be an obstruction, the eggs may be too large or malpositioned, the pelvis may be misshapen, or there may be obstructive masses such as abscesses or cystic calculi. Two or more eggs may be bound together, or a single egg may be exceptionally large or misshapen.
Dystocias can occur in the absence of obstructions or malformations. It is theorized that such retentions may be the result of one or more factors including poor husbandry, improper nesting site, improper temperatures, poor or inadequate diet (malnutrition), dehydration, and poor physical condition of the female. This latter is easily caused in, and remedied, in captivity. Captive reptiles lead a very sedentary lifestyle compared to their wild counterparts, thus lack the muscle strength or tone to get all the eggs into position for laying and expelling them in a timely matter (from first egg to last). It is not uncommon, for example, for the last egg or two to be retained despite the successful and apparent ease with which the rest of the clutch was expelled by oviparous snakes. (In my experience, egg-binding in iguanas happens most frequently to females who are enclosed in cages that do not allow for sufficient climbing, being either too short or they are fed at their basking sites and often physically removed by the owner for defecation elsewhere. Iguanas housed in enclosures at least 5-6 ft high and who must climb up and down for eating, drinking and defecation appear to have fewer incidences of dystocia.)
Diagnosis
Snakes
In smaller
snakes, recent oviposition (the repositioning of the eggs prior to laying)
and the visible appearance of the swelling caused by the mass of eggs
is a clue to the presence of eggs. In larger species such as pythons,
eggs, especially retained eggs, are more difficult to see. It is more
difficult to determine the retention of fetuses especially since entire
clutches may be retained rather than just a few. Prolonged laying or birthing
efforts and cloacal or oviductal prolapse (eversion of cloacal or oviductal
tissue through the vent) are other signs of dystocia. Recently, improved
ultrasonography techniques have been successfully used to determine the
viability of fetuses in viviparous snakes, enabling the veterinarian to
take the steps necessary to alleviate the situation by removing the nonviable
tissue.
Lizards
The most common cause of dystocia in lizards is the absence of a suitable
nesting site and media. A lizard progressing normally through the period
of carrying gestating eggs or fetus will not be eating, but will be alert
and active. Their usually physical grace may be compromised, especially
as their lower half becomes swollen with the developing eggs or fetuses,
but they are able to move around, climbing and roosting as usual. A lizard
suffering from dystocia, on the other hand, will become lethargic, depressed,
nonresponsive. If the laying media is not of the right consistency, the
lizard may spend hours kicking the dirt out, then wandering around, making
digging attempts almost anywhere. This latter activity is more frenzied,
and the lizard grows weaker and more visibly stressed, as the pressure
to lay the eggs mounts. Straining may be seen, as may the prolapse of
cloacal or oviductal tissue. Lizards can tolerate dystocias for considerably
less time than can snakes, often only a matter of days, and so should
be evaluating medically soon after such signs are observed. Many lizards
can produce and lay eggs, just as can chickens and humans, without being
mated.
Chelonians
Egg masses are all but impossible to detect by the inexperienced,
and the presence of one or two retained eggs may not be felt even then.
Retention is very difficult to detect in chelonians due to their being
hidden not only within the turtle or tortoise's body, but the whole covered
by the shell. X-rays are often the only way to tell that eggs are involved.
It may be difficult with radiographs alone to tell if the eggs are being
retained or merely not ready to lay yet; the presence of other signs must
be used in conjunction with the radiographs to determine whether dystocia
is occurring and the urgency for resolution. Depression, straining and
cloacal swelling or prolapse, even respiratory distress, are signs that
should be watched for, and action taken to remove the eggs started.
Treatment
Instigating
treatment before it is necessary may cause more harm to the female and
to the developing clutch. Conversely, withholding treatment, or delaying
getting treatment may be injurious to the female and developing clutch,
especially in lizards. Once the female begins--but does not complete--laying
or birthing, treatment should be started within 48 hours. Females will
sometimes complete laying or birthing after a pause but generally within
the 48 hour window.
Physical
Manipulation
One common
way to induce laying is to gently but firmly massaging the eggs out, one
by one, by running the finger down the abdomen. This method is risky,
however, in that it may rupture or cause a prolapse in the oviduct, could
rupture the egg, and thus possibly cause death. If the egg can actually
be seen at the vent extreme care may be taken to try to remove the egg,
but such attempts may result in a broken egg with disastrous results for
the female.
Hormonal Stimulation
Posterior pituitary hormones have been used to start oviductal
contractions. It is not effective, and may be dangerous, in females who
are suffering from malformation of the pelvis or oviduct or who are carrying
malformed, misshapen, enlarged eggs or fetus or who are suffering from
an obstruction of the oviduct. Use of oxytocin (or the new experimental
arginine vasotocin or aminosuberic arginine vasotocin) in such cases may
cause egg or oviductal rupture or hemorrhage--and death.
The overall efficacy of oxytocin, the most commonly administered hormone, varies between species, and can be hampered the longer the retention; it is most effective when administered within the first 48 hours. Oxytocin is administered by intramuscular or intracoelomic injection (5-30 IU/kg, but reports of efficacy in doses as low as 1 IU/kg have been reported in turtles). A second dose is often given 20-60 minutes after the first injection. Oxytocin's effectiveness is increased by the provision of the proper temperatures, so the female should be kept at the preferred body temperature for the species. Oxytocin is most effective in chelonians, less effective in lizards, and not as effective in snakes, with DeNardo attaining less than 50% success rate in snakes, more than 90% in chelonians.
Arginine vasotocin, and aminosuberic arginine vasotocin, a less effective but more stable form of arginine vasotocin, is the natural reptilian oxytocin. It is thus more effective than oxytocin, but arginine vasotocin is available only as a research drug and is quite expensive than oxytocin. Other hormone treatments have been tried to increase the efficacy of oxytocin including the administration of progesterone and estrogen; there have been no studies to verify their usefulness. One recent study did show that pretreatment with propranolol may increase the efficacy of labor-inducing drugs.
Aspiration
A common treatment
for dystocia involves inserting a needle into the egg and aspirating the
contents. The result is a far smaller egg which may be more easily passed
through the oviduct and cloaca; oxytocin may be used to start contractions
if they do not start on their own within a few hours or even a couple
of days. Caution must be taken to not allow any of the egg contents to
escape into the coelomic cavity. Aspiration must be done within the 48
hour period after cessation of natural laying attempts. After than short
time, the contents of the eggs themselves begin to harden, making aspiration
impossible. If the eggs are not expelled within 48 hours of aspiration,
they must be surgically removed.
Surgery
If other attempts
at inducing laying have failed, the reptile must be anesthetized for surgical
removal. Before cutting, a final attempt at manually manipulating the
eggs may be tried owning to the reduced risk to the female due to the
relaxation of the oviductal sphincter from the anesthesia. As before,
care must be taken to not push hard enough to cause a prolapse or rupture.
Depending upon what is found when the vet goes inside, the eggs only may be removed, or some or all the reproductive tissues may be removed. If there is no intention of breeding the female, the owner may wish to have an ovariosalingectomy done at the same time to prevent future incidences of binding.
Chelonians present some additional difficulties. Egg extraction goes more quickly when done through the shell: part of the shell is cut off, epoxied back into place after surgery. Entry into the coelomic cavity can be made by going in near the hind leg but the restricted maneuverability makes it difficult to find and extract the eggs.
Viability of Removed
Eggs/Fetuses
Fertile eggs removed with oxytocin from non-dystocic females have
been successfully incubated; eggs from females suffering from dystocia
have generally not been successful. Fetuses removed through salpingotomy
have also been successful.
Down the line
The biggest
factors determining female post-retention survival is her overall physical
state. Most are severely weakened as the result of the dystocia. Those
who started out healthy, in good nutritional, hydration and physical states
are more likely to recover. Reptiles who have had only one of their reproductive
tracts removed may often successfully reproduce in the future.
Personally speaking, if you are concerned about dystocia, if you are not sure if your female is gravid or not, if you are not sure if she is in distress or not, I strongly recommend that you don't guess and try to wait it out: get her to a reptile vet and find out exactly (or as much as possible!) what you are dealing with.
Stephen J. Divers,
BSC, CBiol, MIBiol, BVetMed, on reptile dystocia:
"If there is no
indication of infection, metabolic disease, or obstruction (as determined
by radiography, digital palpation, and direct visualization of the cloaca,
and a limited hematological and biochemical assessment), conservative
treatment should be attempted. Provision of a suitable environment and
nesting site may be all that is required to persuade the reptile to produce
eggs or young naturally. If shell gland inertia is suspected, medical
treatment using oxytocin is indicated-1-5 IU/kg, IM, repeated after 60
minutes. In the author's experience, slow IV or intraosseous infusion
of oxytocin at 5 IU/kg, over 4-8 hours is more effective than a single
injection." The Capsule Report, January 1999
Sources include: DeNardo, D. (1995) Dystocias. In Mader, D. (Ed.), Reptile Medicine and Surgery (pp. 370-374). Philadelphia, PA: W.B. Saunders Company.
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