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Very little therapeutic
knowledge exists for diseases of reptiles and many medicines known to be
effective in treatment are not generally available, so the key to keeping a boa
constrictor healthy is prevention. A
captive-born animal is advantageous in that one starts off with a clean slate,
but they are nevertheless subject to a wide range of ailments. The discussion below covers most commonly
encountered problems. Hoff et al.
(1984) have presented a recent comprehensive review of reptilian diseases. Frye (1973) provides an excellent practical
guide to medical treatment of captive reptiles.
Since they are
tropical animals, boa constrictors are highly susceptible to colds. Symptoms are mostly as in people: lethargy, depressed appetite, labored
open-mouth breathing, wheezing, congestion, and oral discharge. Simply raising the temperature to the 27 to
30°C (81 to 86°F) range solves the problem.
My two wild caught constrictors,
like myself, often developed sporadic colds during the winter. However, the imperator from Mexico
and all of the captive-born individuals never catch colds, even when kept
around 24°C (75°F). Place of origin and
amount of acclimation apparently play a part in determining degree of
susceptibility to colds.
Pneumonia is
very serious and requires treatment with antibiotics. An infected animal exhibits extremely severe cold symptoms and
will be too weak to shed or eat. It should
be isolated immediately and given intramuscular injections of ampicillin
trihydrate (Polyflex, 3-6 mg/kg), oxytetracycline HCl (Liquamycin, 6-10 mg/kg),
or chloramphenicol (Chloromycetin, 10-15 mg/kg) once a day (Frye 1973). Murphy (1973) has reported that tylosin is
extremely effective for respiratory problems in a wide variety of
reptiles. It is administered in a daily
25 mg/kg dose as either an oral solution (Tylan) or intramuscular injection
(Tylocine) for seven days. Well stocked
ranch and feed stores generally carry both Liquamycin and Tylan. Force-feeding as described below under Starvation may be
required. Snakes that are kept warm and
well fed will not contract pneumonia.
Mouth rot can
be disfiguring and, if it leads to starvation, lethal. The oral mucosa presents a cottony
appearance and swells till the animal cannot fully close its mouth. This bacterial infection (Aeromonas, Pseudomonas,
Pasteurella) is treated effectively by swabbing the oral cavity twice a
day with mild antiseptic solutions such as Listerine, 3% hydrogen peroxide,
thimerosal (Merthiolate), benzalkonium chloride, or Betadine (Frye 1973, Marcus
1980). Severe cases may require
antibiotics. Force-feeding as described
below may be necessary if the condition has progressed far enough. Mouth rot is prevented easily by proper cage
construction and hygiene (see under Housing).
Starvation is
usually a secondary effect of another disease but frequently the primary cause
of death. A thin snake will be
lethargic and weak. An emaciated snake
will exhibit prominent bones, sunken eyes, and a shriveled skin as well. Curing the disease and force-feeding, if
necessary, comprise the treatment.
Diluted and beaten egg yolk mixed with canned cat food or a commercial
nutritional replacement product such as PetKalorie or Nutrical (Frye 1973) is
tube fed to the snake to gain back or maintain body weight. A flexible tube attached to a syringe filled
with food is passed down the esophagus and the food is then injected into the
stomach. Force-feeding small food items
to a sick snake is a last resort. The
food should be lubricated with beaten egg yolk and pushed down the throat with
a flexible blunt probe. Injuring the
snake's cervical vertebra is easy to do when force-feeding. Sometimes a nonfeeding animal will complete
eating unassisted if the food item simply is pushed into its mouth.
Inclusion
Body Disease (Schumacher et
al. 1994; Klingenberg 1996, 1997a, 1997b)
This viral
disease has only recently been characterized and little is known about it. Clinical symptoms include poor condition,
weight loss, anorexia, regurgitation, chronic secondary infections, and
neurological problems such as tremors and stargazing. Many other reptile diseases also can cause these symptoms, but
inclusion body disease appears to be much more common in collections than
previously hoped. The pathogen is
thought to be a retrovirus that is transmitted primarily by mites and ticks. Diagnosis requires blood analysis and organ
biopsy. No treatment exists for the
disease. Infected animals that show
symptoms can be given supportive care, but remission has never been observed. Because of the deadly nature of this
disease, the lack of any effective treatment, and the high chance that it will
spread to other snakes in a collection, infected individuals should be
euthanized.
By the time amoebiasis can be diagnosed, it
is usually too late to save the individual.
The rear half of an infected animal's body may swell greatly, movement
becomes difficult, a hard plug may form in the colon anterior to the cloaca,
anorexia develops, and the snake can only pass blood-tinged mucus. The snake generally can only drag the rear half
of its body around. After diagnosis,
animals usually die a few days later from gastrointestinal enteritis and liver
abscesses. Infected individuals should
be isolated immediately, preferably to a different room. The cage must be disinfected
thoroughly. Since the pathogen, Entamoeba
invadens, occurs in a cyst form, it is extremely infectious and can be
transported in bedding or on the hands.
Amoebiasis is the worst infectious disease of herpetological collections
(Donaldson et al. 1975, Bihn and Napolitano 1980).
Metronidazole
(Flagyl) is given orally at a dosage of 250 mg/kg (Donaldson et al.
1975, Napolitano et al. 1979).
Another drug that has been used is emetine HCl as a daily 0.5 mg/kg
intramuscular injection for ten days (Frye 1973, Napolitano et al.
1979). High temperatures in the 35 to
37°C (95 to 99°F) range evidently cause Entamoeba invadens infections to
die out (Barrow and Stockton 1960; Meerovitch 1960, 1961; Bihn and Napolitano
1980). Control and eradication of
infection may be possible by holding animals at this temperature range for one
to two days. Conversely, quick drops in
temperature to around 25°C (77°F) such as occur in the Fall, may trigger a
latent infection into the full blown disease (Meerovitch 1961). Prevention requires avoidance of crowded
community cages with many snakes, an appropriate temperature regime, good cage
hygiene, and food that is not old or refrozen.
Lesions of the intestinal wall caused by ingestion of shavings or other
rough indigestible matter may increase susceptibility to infection.
Cryptosporidium
spp. (McAllister et al. 1995)
Cryptosporidium infections in reptiles have only been
described in the past twenty years.
Snakes become infected through oral ingestion of oocysts in the
environment. As in people, reptiles may
become resistant to infection or may simple tolerate the parasite. Snakes with moderate to severe
cryptosporidiosis exhibit anorexia, pneumonia, gastroenteritis, lethargy,
midbody swelling, weight loss, and regurgitation. No effective medicinal treatment for Cryptosporidium has
been found. Oral hydration and tube
feeding (see Starvation
above) represent the only supportive therapeutic intervention.
Cestodes,
Nematodes, Trematodes, and Lingulatids
These parasites usually never become a
problem unless the infected animal becomes weakened for some other reason. Use of some cat or dog medicines can kill
snakes. My original male constrictor
regularly used to pass tapeworms, but never seemed to be bothered by them. He eventually appeared to become clear of
them. Captive-born boa constrictors
will never have tapeworms or other similar types of parasites, unless they are
fed a wild-caught animal or bird that is infected, or a cross-infection occurs
with a cagemate. Only domesticated
animals should be used for snake food.
Captive-born boa constrictors should not be kept with other snakes that
may have a parasitic infestation.
If a boa
constrictor somehow gets internal parasites, I recommend that nothing is done
unless the animal shows chronic weight loss.
Zoo and veterinary personnel may be of some help for diagnosis,
treatment, and medicines such as niclosamide (Yomesan, 150 mg/kg orally) or
bunamidine HCl (Scolaban, 25-50 mg/kg orally) for cestodes, piperazine citrate
(40-60 mg/kg orally) or thiabendazole (Thibenzole, 50 mg/kg orally) for
nematodes, and emetine HCl (0.5 mg/kg/day intramuscularly for ten days) for
trematodes (Frye 1973). I have also
noted that snakes sometimes pass tapeworms when treated with DDVP (phosphoric
acid 2,2-dichlorovinyl dimethyl ester) for mites. The standard veterinary use for DDVP turns out to be as a
gastrointestinal wormer for livestock.
Ranch and feed stores may stock some of these drugs. No treatment is available currently for
lingulatid (tongue or lung worms of the Genus Armillifer) infestations.
Mites (Ophionyssus) and ticks (Ornithodoros
and Amblyomma) are parasitic arachnids dangerous for their ability to
transmit viral and bacterial pathogens.
Book and wood lice (Psocoptera), however, are only nuisance insect
pests. Unfortunately, keeping snakes
free of mites can be like trying to keep mammals free of fleas. The ideal solution is prevention through the
strict quarantine of any new incoming animals.
Rubbing snakes with paraffin oil does not kill eggs in the cage and the
desiccant silica-aerogel powder Dri-Die 67 has been unavailable for a long time
to my knowledge. Silica-aerogel
products also are reported to cause longterm pulmonary problems (Frye
1973). DDVP (phosphoric acid
2,2-dichlorovinyl dimethyl ester), better known as Vapona in No-Pest Strips and
others, has been used as an airborne miticide to control mites and ticks, but
reptiles and people are known to be sensitive to DDVP, a cholinesterase
inhibitor with cumulative effects, and must be kept out of contact with the
strips if they are used. If mites or
lice get out of hand, small pieces of a pest strip can be enclosed in
containers punched with holes and placed in the cage for several days. A thorough cleaning of the cage and soaking
of its occupants in water should also be carried out at the end of this period.
My strategy has been to keep the arthropod
populations as low as possible (preferably at zero) by using pine shavings and
keeping the cages clean, dry, and uncrowded.
Prompt removal of feces and sheds also prevents conditions conducive to
their reproduction. Rarely do I have to
resort to pest strips and soaking. The
presence of mites and lice can be determined most easily by examining the inner
surface of a recent shed (actually the outer surface of the skin). Since they will be moving around and are whitish
gray (lice) to black (mites) in color, even small mites and lice will be
visible against the light background of the shed. They also turn up in the water container after an infested boa
has been soaking in it. Large mites can
be seen easily when they are running around on the head and other body parts of
a captive snake. Some of the most
impressive mite and lice populations I have ever seen were on snakes kept on
damp, dirty newspaper.
Large ticks
usually survive exposure to DDVP and must be removed manually. Very hot forceps are the only way I have
found to convince ticks to back out; yanking out ticks without heating the
forceps usually leaves the mouthparts in place where they can cause infections. The wound should be treated with an
antibacterial cream or solution such as Neosporin, hydrogen peroxide,
thimerosal (Merthiolate), benzalkonium chloride, or Betadine.
Scale
Infections (Blister Disease or Vesicular Dermatitis) (Wright 1995)
Bacterial or
fungal scale infections result from the combined effects of high mite
populations, cool temperature, and damp, dirty cage conditions. In some circumstances, low humidity can also
cause this condition. The infections
themselves are small upraised areas covering one or two scales. Severe infections are suppurating. In combination with the conditions causing
them, the infections cause an animal to weaken, stop eating, and forego
shedding. The cage must be cleaned and
dried out. The snake can be soaked in a
fifty percent Listerine or dilute organic iodine solutions for an hour a
day. Very weak snakes must be given
something to support their head out of the solution and should be monitored so
they do not drown. Scarring usually
does not result from scale infections.
Force-feeding as described under Starvation may aid recovery in weakened snakes
that refuse food.
Problems with
Shedding (Dysecdysis)
The reason that snakes shed their skins often
is said to be that shedding permits growth.
This idea has arisen because they shed their skins as a single piece and
the situation has been analogized with the molting of insects and
crustaceans. Snakes actually grow in
the same way as the majority of other organisms, i.e., cell
division. The true reason they shed
their skins is the same one that people have for shedding: to replace the outer damaged layer of the
skin. The only difference is that
snakes do it all at once; people and other animals tend to do it in patches
(dandruff is the most visible evidence of this).
Boa constrictors undergo a well defined
physiological sequence when they shed their skins. The first indication is dulling of the overall pattern. The snake may refuse to feed from this point
until after it has shed. Animals should
not be fed or handled during the shedding period, as the skin is very soft and
susceptible to injuries causing scars.
Within a few days, the skin becomes quite dull and the eye spectacles
assume an opaque milky appearance for a day or two. Snakes can be quite nervous during this period when they cannot
see well. They often develop a
proclivity for soaking in the water container at this time. The skin and spectacles then clear up. Shedding occurs three to seven days
later. As mentioned before, sheds
should be removed promptly to prevent mite infestations. The new skin exhibits bright vivid markings.
Unhealthy snakes or those under poor cage
conditions often have problems with shedding their skins. Low humidity and/or temperature can cause a
boa constrictor to forego shedding its skin even though it has completed the
preparatory stages. Shedding boa
constrictors should be kept warm and under high humidity with daily spraying,
if necessary. Recalcitrant individuals
can be soaked in an appropriate container to keep the old skin from drying and
adhering to the new one. Wetting of the
snake and shedding by hand should be done when areas of old skin have loosened
and the snake still refuses to shed on its own. Even healthy individuals occasionally have difficulties with
certain areas, usually the spectacles and the tail. If patches of old skin are still adhering to the new one after a
snake sheds out, removing the old skin is a fairly simple procedure. A finger moistened with water or mineral oil
is rubbed over the free anterior edge of the old skin toward the tail. The old skin should come off fairly
easily. Care must be taken with
removing an old spectacle, since the edges of it may be adhering tightly and
trauma to the underlying new spectacle and eye may occur. Very rarely, it is better just to leave the
old spectacle or other unshed skin in place until the next shedding.
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