In reptiles, respiratory tract infections (RTI) are caused by a bacterial infection in the lungs. RTI is generally related to improper environmental conditions, such as being kept too cold, too wet, prolonged stress due to enclosure being kept at a single temperature rather than the species' required thermal gradient, prolonged psychosocial stress, etc. If the reptile is not otherwise being cared for properly (dirty enclosure, inadequate feedings, etc.), this can exacerbate the condition, making it more severe and prolonging recovery.
Symptoms and Diagnosis
Symptoms include listlessness, weight loss due to decreased appetite, swollen or bloated body, gaping, open mouth breathing, often with audible exhalations when in an advanced state. Wheezing may be heard, or clicking noises when breathing. Bubbly, stringy, or sheeting mucous appears in the mouth. The head may be held in a raised position to facilitate breathing. In snakes, the tines of the forked tongue may be stuck together. Respiratory infections in snakes are especially dangerous in those snakes who have only one functioning lung (colubrids, etc.).
When you notice signs of a respiratory infection, not only must you evaluate and correct the environmental problems, but also you must take the reptile to a reptile veterinarian to be evaluated for systemic antibiotic therapy and possibly fluid and nutritional support. If the reptile does not respond to environmental correction and the antibiotic therapy, a culture and sensitivity should be done to determine exactly what the organism(s) is and the best antibiotic to combat it. The sample is easily taken by the vet in the form of a choanal swab or, in more difficult cases, a lung washing. In rare cases, the infection may be due to a fungal infection, which requires different medications than bacterial infections.
Treatment
Treating a respiratory infection requires two things: an immediate evaluation of the day and night temperatures in the reptile's enclosure, with additional heat sources added or broken/malfunctioning equipment replaced, and the attention of a reptile veterinarian who will evaluate the reptile for systemic antibiotics and fluid replacement. In addition, if the reptile has cage mates or lives in a room where he is in line-of-sight of other reptiles or household pets, an overall psychosocial evaluation needs to be made.
Reptiles with respiratory infections should be kept in draft-free but well-ventilated enclosures maintained at the species' daytime temperature gradient both during the day and at night. For reptiles who require a hotter basking area, the basking area temperatures do not need to be provided at night, but the higher overall gradient does. This will not only enable the reptile's own immune system to function better, but increases the efficacy of the antibiotics.
Anorectic lizards and chelonians will need to be hand- or force-fed during this time. Snakes may be able to do fine without food over the short term, but if they begin to show signs of weight loss (a loss in mass) then they, too, will need to be force-fed. See the article on Emaciation (Starvation) Protocol for force-feeding slurry recipes.
Winter Respiratory Infections in Snakes
In the case of snakes with respiratory infection, there is one thing you can try first. Unfortunately, respiratory infections are all too common in captive snakes during the winter because their keepers fail to realize that as the outside temperatures drop, the temperatures inside the building drop, and so the heating equipment that provided sufficient heat during the summer cannot provide sufficient heat during the winter. If caught in time, just boosting the heat into the species' proper thermal range will often take care of the respiratory infection by providing a boost to the reptile's own immune system. If the snake was in a weakened condition to begin with, however, is coming out of hibernation, or is gravid, merely boosting the heat may not be enough. If the symptoms of infection do not disappear completely within 24 to 48 hours, get the snake to the veterinarian.
RTI Mimics
Other situations and conditions that may cause symptoms similar to respiratory infections are inclusion body disease in boas and pythons and ingestion of toxic substances - both of which require veterinary diagnosis and, in the latter case, intervention.
Choking or gagging on a piece of food or foreign object may result in temporary excess saliva. Being handled too soon after eating or drinking may result in water being regurgitated and spit out; since it is now mixed with saliva, it will be rather viscous rather than thin like plain water. If it's too soon after eating, some food may be partially regurgitated and stuck in the throat, which may cause increased salivation. No other signs of RTI occur in these instances, so they are easily told apart from an RTI.
Some reptiles may exhibit signs of respiratory infection as a signal to you that they have been handled enough or want (or need) to be put down. My female Burmese python would start dripping saliva from her mouth in copious amounts when she'd decided she had had enough out and handling time at education events. When I saw the saliva start oozing from her mouth, I knew I needed to put her away off exhibit immediately. (An interesting note: my male Burmese would erect his anal spurs, digging them into my arm, when he was tired.)
Bottom Line
If you see the signs of respiratory infection, and it is not related to being handled too soon after eating or drinking, get your reptile to a reptile vet now - delays will result in a weaker reptile, and depending on why the RTI was allowed to set in to begin with, may prolong recovery and stress.