Bacterial diseases are common in reptiles, with most infections caused by opportunistic commensals that infect malnourished, poorly maintained, and immunosuppressed hosts. A comprehensive approach is required to ensure the success of a therapeutic plan. It is important not only to determine the causative agent but also to correct predisposing factors. Appropriate therapy in the absence of appropriate husbandry and nutrition will ultimately fail.
Cytological (or histological) examination, Gram staining, and culture and susceptibility testing are recommended to determine appropriate therapy. Many bacterial infections involve gram-negative bacteria, many of which are considered commensal. Anaerobic infections are not uncommon; however, organisms can be difficult to culture. Gram-positive bacteria on smears, in conjunction with a negative culture, may indicate an anaerobic infection. Alternatively, if a therapeutic choice was based on aerobic culture and susceptibility and response is poor, then the presence of an anaerobe should be considered.
The routine use of broad-spectrum antimicrobials implies a low level of skill on the part of the clinician and is not in keeping with current antimicrobial stewardship recommendations.
Septicemia in Reptiles
A number of infectious conditions are similar in appearance, regardless of species. Septicemia is a common cause of death. Systemic disease may be preceded by trauma, localized infection, parasitism, or environmental stressors. Aeromonas and Pseudomonas spp are frequently isolated; the former may be transmitted by ectoparasites.
Death may be peracute or follow a protracted course. Common terminal clinical signs are respiratory distress, lethargy, convulsions, and incoordination. Petechiae may be found on the ventrum, and chelonians develop erythema of the plastron. Sanitation and husbandry can be important factors in decreasing outbreaks. Affected reptiles should be isolated, and antimicrobial therapy initiated.
Septicemic Cutaneous Ulcerative Disease in Reptiles
Classically, septicemic cutaneous ulcerative disease (SCUD) is a shell disease of aquatic turtles caused by Citrobacter freundii; however, various bacteria have been isolated from diseased skin and shell. Serratia spp may act synergistically by facilitating entry of C freundii. The scutes are pitted and may slough with an underlying purulent discharge. Anorexia, lethargy, and petechial hemorrhages on the shell and skin are evident; liver necrosis and abscessation is also common (see image of SCUD in a turtle).
Courtesy of Dr. Stephen Divers.
Wound debridement and systemic antimicrobials are recommended. Good sanitation is paramount for prevention.
Another shell disease of turtles is caused by Vibrio chitinovora (syn Beneckea chitinovora), a common infectious agent of crustaceans. Erythema and pitting of the shell with ulceration occur. Septicemia is uncommon. Topical iodine is recommended in addition to antimicrobials. The practice of feeding turtles crayfish is often implicated in this condition and should be discouraged.
Ulcerative or Necrotic Dermatitis in Reptiles
Ulcerative dermatitis (scale rot) occurs in snakes and lizards kept in unhygienic conditions with excessive humidity and moisture. Moist, contaminated bedding allows bacterial and fungal growth that, when coupled with exposure to fecal degradation products and skin damage from inappropriate floor heating, can predispose snakes and lizards to small cutaneous erosions. Secondary infection with Aeromonas spp, Pseudomonas spp, and a number of other bacteria may result in septicemia and death if untreated.
Erythema, necrosis, and ulceration of the dermis and an exudative discharge are common (see ulcerative dermatitis image). Although lesions are often sequelae of skin injuries, they more often develop from within, as is the case with classic necrotic dermatitis in the ball python. The disease can develop even when animals are maintained under pristine conditions, so it is not simply a matter of excessive moisture and poor hygiene. The condition starts with hemorrhage into scales, followed by pustules that eventually lead to open and ulcerated lesions. Debridement and treatment with systemic antimicrobials, topical antimicrobial ointment, and excellent hygiene and husbandry are essential.
Courtesy of Dr. Stephen Divers.
Blister disease has traditionally been considered a separate entity but is simply an early stage of ulcerative (necrotic) dermatitis. Cutaneous involvement is characterized by pustules or blisters that may resolve without development of ulcerative lesions if treatment is started early. A low-grade thermal injury may mimic blister disease because of the potential development of fluid-filled vesicles.
Abscesses in Reptiles
Focal infections, which occur in all orders of reptiles, are caused by traumatic injuries or bite wounds and often made more likely by poor management.
Subcutaneous abscesses are present as nodules or swellings. Differential diagnoses include parasitic nodules, tumors, and hematomas. Isolates of the anaerobic organism Peptostreptococcus and of the aerobes Pseudomonas, Aeromonas, Serratia, Salmonella, Micrococcus, Erysipelothrix, Citrobacter freundii, Morganella morganii, Proteus, Staphylococcus, Streptococcus, Escherichia coli, Klebsiella, and Dermatophilus have been recovered from reptilian abscesses, often in combinations.
Small, localized abscesses should be completely excised to avoid recurrence. Larger abscesses should be marsupialized, followed by aggressive local wound treatment, including daily antiseptic lavage. The lining of the abscess must be thoroughly scraped to remove as much material as possible. Systemic antimicrobials are seldom necessary after complete excision. Anaerobic bacteria are common in these lesions. See image of subcutaneous facial abscess, plumed basilisk.
Courtesy of Dr. Stephen Divers.
Pearls & Pitfalls
|
Visceral abscessation may occur as a result of hematogenous infection or intestinal translocation. Abscesses of the female reproductive system and liver are common and often result in coelomitis. Surgical intervention is indicated; systemic antimicrobials alone are rarely, if ever, successful.
Subspectacular abscessation occurs in snakes, and conjunctivitis occurs in other reptile orders. Severity ranges from mild inflammation to panophthalmitis and may occur as a result of ascending infectious stomatitis. Topical antimicrobial ointments are used in turtles, lizards without spectacles, and crocodilians.
In snakes and lizards with spectacles, drainage is achieved by surgically removing a small wedge from the spectacle and flushing the subspectacular space and lacrimal duct with an antimicrobial solution (eg, gentamicin) (see subspectacle abscessation image). Some affected reptiles, especially turtles, may need supplemental vitamin A.
Courtesy of Dr. Stephen Divers.
Infectious Stomatitis in Reptiles
Infectious stomatitis (mouth rot) is reported in snakes, lizards, and turtles and is characterized early by petechiae in the oral cavity; caseous material develops along the dental arcades as the condition worsens (see infectious stomatitis image). In severe cases, infection spreads to cause osteomyelitis of the mandible and maxilla.
Courtesy of Dr. Stephen Divers.
Aeromonas and Pseudomonas spp, common oral inhabitants, are most frequently isolated in infectious stomatitis, along with a variety of other gram-negative and gram-positive aerobic and anaerobic bacteria. Respiratory or intestinal infection may develop in poorly managed cases. Surgical debridement, repeated irrigation with antiseptics, systemic antimicrobials, and supportive therapy are indicated. In severe cases with ulceration or granuloma formation, aggressive surgery may be indicated. Vitamin supplementation, especially with vitamins A and C, has been advocated but does not always affect the disease course.
Pneumonia in Reptiles
Courtesy of Dr. Stephen Divers.
Respiratory infections are common; their incidence can be influenced by respiratory or systemic parasitism, unfavorable environmental temperatures or humidity, insufficient ventilation, unsanitary conditions, concurrent disease, and malnutrition.
Open-mouth breathing, nasal or glottal discharge, and dyspnea are frequent clinical signs. Aeromonas and Pseudomonas spp are frequently isolated; however, many respiratory infections are mixed. Septicemia may develop in severe or protracted cases.
Treatment consists of improving husbandry and initiating systemic antimicrobial therapy after the collection of diagnostic material. Nebulization with antimicrobials diluted in saline, in combination with acetylcysteine, has been used together with parenteral antimicrobials. Reptiles with respiratory infections should be maintained at the mid to upper range of their preferred optimal temperature zone. Increased temperatures are important not only to stimulate the immune system but also to help mobilize respiratory secretions and to help ensure proper drug metabolism for effective treatment. Turtles and lizards with respiratory infections often have an underlying vitamin A deficiency and require dietary correction.
Mycoplasmosis in Reptiles
Mycoplasmosis is a known cause of rhinitis and upper respiratory tract disease in chelonians and polyserositis in crocodilians. In chelonians, mycoplasmosis has been associated with population declines, and the disease is often chronic and/or intermittent (see image of upper respiratory tract disease in a tortoise).
Courtesy of Dr. Stephen Divers.
In American alligators, mycoplasmosis results in severe systemic disease and frequently death. A variety of Mycoplasma spp have been isolated. PCR assay and serological diagnostic aids have been developed to confirm infection, and treatment using tetracyclines and macrolides has been advocated.
Otitis in Reptiles
Ear infections occur frequently in turtles, especially box turtles and aquatic turtles. Marked swelling occurs at the tympanic membrane, and caseous material is present (see aural abscess image). Proteus spp, Pseudomonas spp, Citrobacter spp, Morganella morganii, Enterobacter spp, and other bacteria have been isolated.
Courtesy of Dr. Stephen Divers.
The tympanic membrane must be incised, followed by complete removal of all inspissated material. Surgical treatment is usually curative as long as all infection is removed and the eustachian tube is patent. The open area should be flushed with diluted povidone-iodine until the area heals by second intention. Systemic antimicrobials are rarely, if ever, required after aural abscesses have been completely debrided.
Ear infections may be secondary to hypovitaminosis A or ascending infection from the oral cavity. Many chelonians with aural abscesses require oral vitamin A supplementation if hypovitaminosis A is considered a predisposing factor.
Cloacitis in Reptiles
Often traumatic in origin, infectious cloacitis is characterized by edema and hemopurulent discharge (see cloacitis image). Cloacal calculi may lodge in the cloaca and predispose to local inflammation and swelling unless removed. In pericloacal abscesses, the infection often migrates craniad. Ascending urinary or genital tract infections are common sequelae.
Courtesy of Dr. Stephen Divers.
Aggressive therapy, including surgical debridement, local wound treatment, and administration of appropriate systemic antimicrobials, is indicated. Fecal examination should be performed to identify potential parasitic causes, and radiography may help identify causes of tenesmus.
Spinal Osteopathy/Osteomyelitis in Reptiles
The condition previously reported in the reptile literature as Paget disease is now thought to be a chronic bacterial osteomyelitis of the spine (see spinal osteomyelitis image). Traditionally, Paget disease has been characterized by repeated episodes of osteoclastic bone resorption and deposition leading to dense, brittle bones. Commonly reported in snakes, these proliferative and progressive spinal lesions have been investigated and are now thought to be associated with chronic bacterial infections, most commonly involving Salmonella spp.
Diagnosis is by biopsy or blood culture. Long-term antimicrobial therapy may be helpful; however, the prognosis is typically guarded to poor.
Courtesy of Dr. Stephen Divers.
Mycobacteriosis in Reptiles
Mycobacterial infections are more often associated with chronic wasting in wild, imported reptiles and are observed as granulomatous lesions at necropsy; however, infections also occur in captive-bred animals. Chelonians generally exhibit pulmonary involvement, whereas lizards, snakes, and crocodilians commonly show visceral granulomas (see pulmonary mycobacteriosis image).
Courtesy of Dr. Stephen Divers.
The common species isolated are Mycobacterium ulcerans, M chelonae, M haemophilum, and M marinum. All are cultured at decreased temperatures and may require months for growth. Rifampin and isoniazid are hepatotoxic, and the long-term administration required is unlikely to be safe. There are no reports of successful treatment, and most cases are euthanized at an advanced stage of presentation.
Salmonella enterica Infection in Reptiles
Salmonella have been frequently isolated from clinically healthy reptiles and should be considered part of their normal GI flora. The zoonotic nature of these commensal organisms must be considered when handling or treating reptiles. Attempts to eliminate these microorganisms from reptiles and their eggs have been unsuccessful and are not recommended. Veterinarians and reptile owners should be aware of the guidelines available from the Association of Reptile and Amphibian Veterinarians.
Pearls & Pitfalls
|
For More Information
Salmonella and reptiles: veterinary guidelines. Association of Reptile and Amphibian Veterinarians.
Divers SJ, Stahl SJ. Mader's Reptile and Amphibian Medicine and Surgery. 3rd ed. Elsevier; 2019.
Divers SJ, Burgess BA. ARAV antimicrobial stewardship policy. J Herpetol Med Surg. 2023;33(1):61-64.
