Observations on Dehydration in Reptiles.

A.C.Highfield

Not infrequently, tortoise and reptile enthusiasts are confronted by acutely dehydrated specimens. Many leave dealers premises in this condition, and others are the result of poor husbandry on the part of previous keepers. Spontaneous dehydration may also occur as a result of illness, particularly protozoan infections of the G.I tract or pneumonia, both of which can cause acute dehydration to occur within a surprisingly short period of time. It is extremely important that persons who encounter dehydrated reptiles recognise the symptoms, metabolic implications and support therapy required to overcome the condition.

Symptoms: Dehydrated tortoises are usually underweight compared to a healthy specimen of similar proportions, although an obese animal may not be so. The eyes are almost always sunken, and in very acute cases, the centres of the cornea may be depressed. On manual examination, muscular tissue will lack resilience and the skin may also be unusually dry and the surface powdery. With the possible exception of cases of pneumonia, the oral mucous may be unusually viscous and turgid.

Metabolic implications: Terrestrial chelonians, lizards and snakes excrete nitrogenous waste products including ammonia (which is produced as a result of the protein metabolism) in the form of uric acid. Urates are transported from the liver in the blood to the renal glomeruli for filtration and then to the linings of the tubules where the water required for transportation is re-absorbed. In animals adapted to arid habitats such water being of far too much importance to waste. The concentrated uric acid, in the form of a crystaline deposit of low water content is then excreted via the cloaca. Should the animal suffer dehydration, the process of transporting nitrogenous waste products is the first major metabolic function to suffer. Blood urea levels rise and excess uric acid precipitates within the renal tubules and elsewhere throughout the body. The filtration function of the kidneys ceases, and necrotic degeneration of the renal system eventually follows. Post mortem, the kidneys are usually enlarged and infiltrated by yellowish-brown deposits of uric acid.

Prevention and supportive therapy: For practical purposes it can be useful to divide dehydrated reptiles into two groups. Group A animals may have acute dehydration but blood urea levels and uric acid precipitation has not yet reached a critical level. Renal function has not been impaired. Such dehydration is often encountered following a protozoan or similar G.I tract infection which has resulted in diarrhoea and excessive cloacal voiding. Animals of this group are also encountered following short-medium term failures of husbandry. The problem can usually be corrected by oral dosing with a compound sodium chloride, potassium chloride and glucose oral rehydration combination (e.g, 'Dioralyte' or ' Lectade').

Group B animals are much more problematic. Here, in addition to the usual external signs of dehydration, blood urea is elevated and renal function is impaired to a greater or lesser degree. Victims of long term neglect, inanition and dehydration or animals which have been on an excessively high protein diet for their species are those most likely to fall into this group. The first objective, even before inanition is dealt with, must be to restore renal function as quickly as possible. In herbivorous chelonia, oral dosing with Hartmann's Solution (compound sodium lactate) at up to 5% bodyweight daily has been highly successful. Where renal function is severely impaired and following fluid support therapy severe oedema manifests the use of a diuretic such as Frusemide may be warranted. Only when renal function and uric acid excretion has been restored should additional support therapy be administered in the form firstly of an oral rehydration compound followed within a week or two by 'Duphalyte' or similar combination electrolyte and amino-acid preparation.

It is a common mistake upon confronting an animal suffering from inanition and dehydration to overlook the dehydration and concentrate upon the inanition. In chelonians, large quantities of high protein force feeds are often administered. This is in fact extremely dangerous and can result in mortality. If renal function or nitrogenous waste excretion is impaired additional protein input can only exacerbate the problem. For the same reason, the protein content of the general and post-recovery diet should also be carefully monitored, and steps should be taken to ensure that animals adapted to ultra low dietary protein inputs such as herbivorous chelonians are not placed upon artificially high protein diets, e.g animal proteins or foodstuffs of vegetable origin which are similarly high in protein content such as legumes. The nitrate content of processed animal protein sources is particularly lethal in this context.

Prevention obviously is better than cure, and much can be achieved by ensuring that all captive reptiles are provided with adequate access to fresh drinking water. The fluid and protein contents of food items should also be considered relative to the specific requirements of the species. Where dehydration is suspected, early detection, prompt intervention and veterinary treatment can do much to prevent serious secondary renal damage from occurring.

NB: Hartmann's solution, Duphalyte and Frusemide mentioned above are prescription only medicines which must only be used under veterinary supervision.