Presenting problem: Dysecdysis in Reptiles

Introduction

Evidence of a difficult shed or dysecdysis is commonly seen in debilitated snake and lizard patients. Dysecdysis is not in itself a primary problem, but rather a sign of an underlying problem (Fig 1) (de la Navarre 2006).

Figure 1. Shed-related problems are common in captive snakes and some lizards. Image by Jaymis. Click on image to enlarge.

Understanding ecdysis or shedding

Scales

All reptiles are covered with scales that protect them from injury and desiccation. Derived from the epidermis, scales consist primarily of keratin and are attached to each other by soft skin (Fig 2). There are two basic types of scales. Relatively small scales that overlap like the shingles on a roof cover the dorsum and lateral surfaces of snakes and many lizards (Fig 3). Relatively short, wide scales called “scutes”, arranged like the rungs on a ladder, are found on the ventrum (Fig 4) (Cooper 2006, Mader year n/a).

Figure 2 Scales are attached to each other by soft skin (white in the shed skin shown here) . Image by Keri Leaman. Click on image to enlarge.

Figure 3. Relatively small scales that overlap like the shingles on a roof cover the dorsum and lateral surfaces of snakes and many lizards. Image by Roger Riera. Click on image to enlarge.

Figure 4. Shown here, scutes or belly scales in shed skin. Image by grongar. Click on image to enlarge.

Ecdysis

New scales grow beneath older, more superficial scales. In snakes, and some geckos, skin shedding, sloughing, or ecdysis is an active, complex process that occurs throughout the life of the animal (Box 1).

During the first 5 to 7 days of the renewal phase lymphatic fluid collects between the old and new skin. This causes the skin to appear very dull, markings become less distinct, and the spectacles appear opaque or milky blue. These changes begin on the ventral surface of the tail and moves craniad (Fitzgerald 2006, Mader n/a). Vision is dramatically impaired during this period, putting reptiles at increased risk for bite wounds from prey items. Snakes in this stage also appear to be much more sensitive to touch, becoming irritable and more likely to bite. At the conclusion of the renewal phase, the eyes clear and skin appears shiny. Shedding typically begins within 3 to 4 days after skin clears (Fitzgerald 2006). During shed, the skin is particularly susceptible to trauma, infection, and toxic exposure (Cooper 2006).

The length of the shedding cycle is affected by a number of factors including age and nutritional status (Navarre 2006). Young, actively growing reptiles shed more frequently than mature adults.

Complete sheds occur periodically in snakes and some lizards. The skin is normally shed in one piece, inverted like a sock pulled from the top down (Fig 5). Sheds are only partial in most lizards and crocodilians, and skin is shed in patches (Fig 6). When a snake sheds in patches this can signify an underlying problem. Geckos often ingest patches of shed skin, so it is not observed in the environment.

Figure 5. Snakes normally undergo a complete shed. The skin is shed in one piece, inverting like a sock pulled inside out. Image by Dave Parker. Click on image to enlarge.

Figure 6. Normal patchy shed in an iguana. Photograph provided by Jeannette Wyneken, Ph.D. Click image to enlarge.

Chelonians also shed the skin on their neck, legs, and tail and aquatic turtles shed the epithelial scutes on their carapace and plastron.

Key points of urgent care

Dysecdysis is not an emergency condition, however when a difficult shed is recognized, the problem should be addressed (de la Navarre 2006).

Case management

Signalment

Primarily a disease of captive reptiles, dysecdysis is sporadically seen in free-ranging reptiles. Among captive reptiles, difficult sheds are most common in those with a complete shedding cycle: snakes and some geckos such as the leopard gecko (Eublepharis macularius) and African fat-tailed gecko (Hemitheconyx caudicinctus) (Stahl 2013). Some skinks (Tiliqua spp.) with relatively tiny digits, are prone to retaining shed skin on the digits (Fig 7).

Figure 7. The relatively small digits of blue-tongued skinks (Tiliqua spp.) are at increased risk of retained shed. Image by Donald Hobern. Click on image to enlarge.

History

• Obtain detailed information on the patient’s medical history as well as husbandry, including cage temperature and relative humidity.
• When did the last shed occur?
• Is there a history of scar formation, thermal burns, or surgical incision? The presence of skin lesions increases the risk of dysecdysis dramatically.

Visual examination

Postpone physical examination if the reptile appears to be in the midst of a shedding cycle. Handling reptiles, particularly snakes and some geckos, during a shed can cause skin damage and subsequent dysecdysis (de la Navarre 2006).

Physical examination

Perform a complete physical exam. Retained shed is most commonly found on the tail, head, and spectacles. Patchy shed can also be found on ornamental appendages, such as the dorsal spines in lizards like iguanas, as well as the digits. Retained shed on distal extremities can serve as constrictive bands preventing normal blood flow and causing avascular necrosis and possibly secondary osteomyelitis possible (Stahl 2013).

Retained shed within or around the nares can cause wheezing or whistling sounds that can be mistaken for respiratory disease.

Also carefully screen the patient for evidence of ectoparasites and inflammation. Retained layers of keratinized epidermis can serve as a nidus of infection, particularly around the oral cavity and eyes, leading to stomatitis and conjunctivitis respectively. Blue-tongued skinks are particularly prone to retained shed around the oral cavity (Stahl 2013).

Underlying cause

In many cases, dysecdysis is directly associated with improper management or husbandry:

• Improper environmental temperature (too cold)
• Improper humidity (too dry or no access to bathing)
• Improper nutrition
• Improper handling (see visual exam above)
• Lack of cage furniture (e.g. rocks, branches, logs to rub against)
• Poor water quality, improper lighting, and/or lack of appropriate basking spots in semi-aquatic or aquatic turtles

Retained shed can also be associated with an underlying medical problem including:

• Fungal or bacterial skin disease
• Ectoparasites, such as mites, can interfere with the normal shed process as can thermal burns, old scars, and bite wounds (Fig 8)
• Hypoproteinemia (e.g. malnutrition, starvation)
• Hypovitaminosis A in chameleons (Stahl 1997)
• Systemic illness

Figure 8. Difficult shed (arrow) in a burmese python (Python bivittatus) with ectoparasites. Photograph provided by Dr. M. Scott Echols. Click image to enlarge.

Differential diagnoses

• Dermatitis
• Trauma
• Excessive shedding caused by thyroid disease

Diagnostics

If husbandry has been corrected yet dysecdysis persists or recurs, a complete diagnostic workup is generally indicated:

• Survey radiographs if there is evidence of avascular necrosis to evaluate underlying bone for evidence of osteomyelitis
• Cytology, C/S of inflamed/infected areas

Refer the patient to a reptile veterinarian whenever possible, as advanced diagnostic techniques such as biopsy, histopathology, and thyroid testing may be indicated (Dadone 2010).

An exception to this rule of thumb would be reptiles with scars, thermal burns, or surgical incisions as retained shed frequently recurs in affected regions.

Therapeutics

Employ a gentle, conservative approach to retained sheds. Attempts to prematurely remove retained skin can permanently damage and scar the new layer of skin that lies underneath.

1. 1. Hydrate the skin:  Warm water (85ºF or 29.4ºC) soaks are usually the best way to remove retained shed (Fitzgerald 2006, de la Navarre 2006) for approximately 15 to 30 minutes. Water should be deep enough to cover the reptile’s body but not so deep that the reptile must swim for its life. Soaking reptiles should never be left unattended (de la Navarre 2006). To reduce the risk of chills, air temperature should be warm and free of drafts. Addition of an appropriately sized cotton towel or terry cloth can gently remove retained shed as the reptile moves over the towel (de la Navarre 2006). Soaks can be repeated over a period of days until all retained skin is gone, however the length of time necessary will vary with the number of abnormally retained shed layers.Alternatively the reptile and its environment can be spritzed with fine mists of lukewarm water.Provision of a humid microhabitat or humidity box can also prove helpful. Place a plastic container with an entrance on one side and a thin layer of moistened sphagnum moss or vermiculite on the floor (Stahl 2013).
   2. Correct underlying husbandry problems:  Educate the owner on the proper relatively humidity, cage temperature, and cage furniture that should be provided. Ensure that semi-aquatic and aquatic turtles have adequate basking spots, lighting, and proper water quality.
   3. Provide antiseptics and antimicrobials as needed:  Generally water-only soaks are adequate but antiseptics are indicated if there is evidence of inflammation or superficial infection. Dilute chlorhexidine solution (1 part chlorhexidine to 50 parts saline) is commonly used (de la Navarre 2006, Fitzgerald 2006). Alternatively topical antimicrobial cream such as silver sulfadiazine cream () can be applied to focal, superficial lesions like ulcers.More extensive or severe infections will require systemic antibiotics. Secondary infections are usually caused by Gram-negative bacteria such as Pseudomonas spp., Aeromonas spp., Klebsiella spp., and Salmonella spp. as well as anaerobes like Bacteroides spp., Fusobacterium spp., and Clostridium spp. (Stahl 2013). Less commonly, fungal infection can also be associated with dysecdysis (Dadone 2010, Stahl 2013).

Prognosis

The prognosis for reptiles with dysecdysis is generally good. Once the underlying cause of retained shed has been identified and addressed, the shedding cycle usually returns to normal within two to four cycles (de la Navarre 2006).

One exception to this rule of thumb includes reptiles with scars or thermal burns frequently exhibit chronic, persistent shed-related problems. Owners of affected reptiles can be taught to assist shedding with soaks, sprays, and warm, wet towels (de la Navarre 2006).

Reptiles with retained shed on the digits can also have a more guarded prognosis if the problem is serious enough to cause constriction bands. Avascular necrosis can cause sloughing of skin and osteomyelitis of underlying bone.

References