The response of the pituitary-adrenal and pituitary-thyroidal axes to the plasma glucose perturbations in Babesia canis rossi babesiosis

J.P Schoeman,M.E Herrtage

doi:10.4102/jsava.v78i4.326

Abstract

This prospective, cross-sectional, interventional study was designed to determine the association between the hormones of the pituitary-adrenal and pituitary-thyroid axes and other clinical parameters with the blood glucose perturbations in dogs with naturally occurring Babesia canis rossi babesiosis. Thirty-six dogs with canine babesiosis were studied. Blood samples were obtained from the jugular vein in each dog prior to treatment at admission to hospital and serum endogenous adrenocorticotrophic hormone (ACTH), pre-ACTH cortisol, thyroxine, free thyroxine and TSH concentrations were measured. Immediately thereafter each dog was injected intravenously with 5 microg/kg of ACTH (tetracosactrin). A 2nd blood sample was taken 1 hour later for serum post-ACTH cortisol measurement. Three patient groups were recruited: hypoglycaemic dogs (glucose < 3.3 mmol/l, n = 12); normoglycaemic dogs (glucose 3.3-5.5 mmol/l, n = 12); hyperglycaemic dogs (glucose > 5.5 mmol/l, n = 12). Basal and post-ACTH serum cortisol concentrations were significantly higher in hypoglycaemic dogs, whereas body temperature, serum thyroxine and free thyroxine were significantly lower in hypoglycaemic dogs. Haematocrit was significantly lower in both hypo-and hyperglycaemic dogs compared with normoglycaemic dogs. Low blood glucose concentrations were significantly associated with high basal and post-ACTH cortisol concentrations and with low serum thyroxine and free thyroxine concentrations in dogs suffering from B. canis rossi babesiosis.

Highlights

The blood glucose perturbations in virulent canine babesiosis have been highlighted recently and 1 study identified hypoglycaemia in 20 % of canine babesiosis cases admitted to a veterinary hospital11
Affected dogs treated as outpatients, as well as more severely affected dogs that died, were excluded. This was done in an attempt to assure that the groups were as similar as possible in all respects, apart for their blood glucose concentrations, to limit the confounding effect of the previously described high death rate on the cortisol, T4 and fT4 concentrations11,20
Significant hypoglycaemia and attendant risk factors such as clinical collapse, low haematocrit, icterus and young age have previously been described in virulent B. canis rossi babesiosis11

Summary

Introduction

The blood glucose perturbations in virulent canine babesiosis have been highlighted recently and 1 study identified hypoglycaemia in 20 % of canine babesiosis cases admitted to a veterinary hospital. Apart from its association with hyperlactataemia and poor outcome, little is known regarding the pathophysiology of hypoglycaemia in this disease. Human falciparum malaria is a disease in which pathophysiology similar to that of virulent canine babesiosis has been postulated. In malaria, increased insulin concentrations was a cause of hypoglycaemia in adults and children and inadequate gluconeogenesis, compounded aDepartment of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110 South Africa. BDepartment of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, CB3 OES, England.

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