Tim Hyndman

This chapter provides an overview of tests commonly described in reptile medicine and their interpretation. Diagnostic testing should always be interpreted together with other findings, including history, clinical signs and adjunct testing methods. In reptile practice, molecular diagnostics are usually used to detect the nucleic acids of infectious agents. Haematology can be used to provide physiological information regarding the health of reptile patients. Biochemical analyses can provide physiological information about a reptile patient's health status. Serological testing is used in reptile medicine to determine whether an animal has been exposed to certain infectious agents. Cytological examination of samples can be used to make a diagnosis or to guide a clinician to additional diagnostic tests. In reptiles, neutralization tests have been used for multiple viruses including herpesviruses, adenoviruses, reoviruses and picornaviruses. Viral cultures are rarely used in reptile diagnostics and generally require highly specialized laboratories.

The collective knowledge of the infectious diseases of reptiles has been rapidly expanding in the last few years. This chapter provides summaries of the infectious diseases. Rhinitis and upper respiratory tract illness is most commonly seen in chelonians. The infectious causes of lower respiratory tract disease seen in reptile practice include viruses, bacteria, fungi and parasites. Disease of this system is common in all reptile species. Bacterial and fungal infections of the alimentary tract can be very difficult to diagnose since the normal flora in reptiles can include multiple potential pathogens. Liver disease is relatively common in reptiles with many infectious agents, including viruses, bacteria, fungi and parasites capable of infecting the liver. In reptiles, the immune responses mounted against foreign antigens have not been fully mapped but it is suspected reptiles rely on nonspecific immunological defences more than mammals.

Injections administered into the muscle and the subcutaneous tissue are two common routes of drug administration for reptiles. Owing to the limited arsenal of drugs that are registered for use in reptiles, it can be tempting to obtain medicines from compounding pharmacists. Fungal infections in reptiles occur most commonly on the skin. The chapter presents some empirical antibiotic choices for a selection of common reptile. The most extensively studied antivirals in reptiles are all purine analogues and they have been associated with varying degrees of success in treating herpesvirus infections in tortoises. The majority of antiparasitics used in reptiles for internal helminths are administered orally and these include the benzimidazoles and the macrocyclic lactones. There are insufficient data to be able to recommend the use of corticosteroids as anti‐inflammatories and analgesics, and similarly, the efficacy of other analgesics such amantadine, gabapentin, ketamine and alpha‐2 agonists has not been properly substantiated.

Gastric cytoprotective agents are used when normal gastric defense mechanisms are disrupted, thereby exposing submucosal layers to damage from gastric acid, or when there is another need for reducing gastric acidity, such as esophageal disease. Signs of significant gastric ulceration are hematemesis and melena. Hematemesis refers to the vomiting of blood, which, when digested, may have the appearance of coffee grounds. Gross melena (digested blood in the feces) only occurs after significant volumes of blood have been lost into the intestinal lumen. The gastric mucosa has several intrinsic properties that protect it from autodigestion, including intact apical cell membranes, tight junctions, bicarbonate secretion, mucus production, rich blood supply, active cell renewal, surface active phospholipids, and endogenous prostaglandins. Gastric ulceration is believed to have its origins in the disruption of the mucosal barrier, or as a result of excessive acid secretion (Box 45-1), and is more commonly reported in dogs than in cats.1, 2, 3 and 4 History and physical examination, as well as full metabolic assessment, will help to rule out systemic disease and drug administration as the underlying cause. Strenuous exercise, particularly in sled dogs, is associated with increased intestinal permeability and gastrointestinal ulceration.5 and 6 The use of corticosteroids in dogs with intervertebral disk disease has been associated with severe gastrointestinal ulceration.7 If no underlying cause is identified abdominal ultrasound combined with further testing, such as endoscopy or gastric biopsy, may be required.