The pathophysiology of renal and cardiac changes in canine babesiosis

This thesis showed that dogs with natural infection with B. canis had both renal and cardiac dysfunction, both of which can be classified as complications of babesiosis and would thus necessitate supportive therapy. This thesis demonstrated that RTE celluria, proteinuria, and variable enzymuria and azotaemia occur in dogs with babesiosis. However, these were all minimal changes and all could be consistent with hypoxia, reduced GFR, or reduced cardiac output This thesis showed that dogs with naturally occurring babesiosis had significant urine met-haemoglobin with no evidence of blood met-haemoglobin. The possibility would be that the urinary methaemoglobin was either produced in the kidney or possibly by oxidation of haemoglobin to met-haemoglobin in the bladder. It has been shown experimentally that met-haemoglobin can be toxic. The combination of reduced GFR, anaemic hypoxia, and met-haemoglobin can all act synergistically to cause renal damage. Renal haemodynamics are also much more likely to be abnormal when cardiac dysfunction is present Reduced renal blood flow and glomerular filtration rate are evidence of redistribution of blood flow that commonly occurs in early heart failure. An important finding in this thesis was that dogs with babesiosis had lower serum sodium than control dogs but there was no difference between mild, severe, or complicated cases of babesiosis. In addition, dogs with babesiosis had a lower fractional clearance of sodium than Clinically healthy control dogs, which can be interpreted as sodium retention by the kidneys. This sodium retention would also result in water retention , which will result in an expansion of the plasma volume. In the past heart lesions in canine babesiosis were regarded as rare complications, with the majority of lesions being reported as incidental findings at post-mortem examination of complicated babesiosis cases. This thesis has demonstrated that cardiac lesions to be common in canine babesiosis. This thesis showed that that ECG changes in babesiosis were similar to the pattern described for myocarditis and myocardial ischaemia, and together with the histopathological findings indicated that the heart suffers from the same pathological processes described in other organs in canine babesiosis, namely inflammation and hypoxia. As the clinical application of the ECG changes found in this thesis was limited, cardiovascular assessment should be based on functional monitoring rather than ECG. Using cardiac troponin as a marker of myocardial injury, this thesis showed that myocardial cell injury occurs with canine babesiosis. Cardiac troponins, especially troponin I, are sensitive markers of myocardial injury in canine babesiosis, and the magnitude of elevation of plasma troponin I concentrations appears to be proportional to the severity of the disease. ECG changes and serum cardiac troponin were correlated with histopathology. On cardiac histopathology from dogs that succumbed to babesiosis, haemorrhage, necrosis, inflammation and fibrin microthrombi in the myocardium were documented, all of which would have resulted in ECG changes and elevations in cardiac troponin. Myocardial infarction causes left ventricular failure, which will result in hypotension and an expansion of the plasma volume due to homeostatic mechanisms. This thesis showed that dogs with babesiosis had hypoalbuminaemia, which may be because of intravascular volume dilution due to fluid retention. In disease hypoalbuminaemia can occur as a negative acute-phase protein. In the light of the cardiac changes, hyponatraemia, and hypotension, a probable cause would be fluid retention due to myocardial disease. This thesis showed that dogs with babesiosis had left ventricular lesions, which can result in systolic heart failure.Thesis (PhD)--University of Pretoria, 2005.Veterinary Tropical Diseasesunrestricte

Worldwide prevalence and risk factors for feline hyperthyroidism : a review

Since first reported in the late 1970s, there has been a steady but dramatic increase in the worldwide prevalence of hyperthyroidism in cats. It is now regarded as the most common feline endocrine disorder, with diabetes mellitus coming a close second. Not only is there evidence for an increased worldwide prevalence of feline hyperthyroidism, but also for geographical variation in the prevalence of the disease. Despite its frequency, the underlying cause(s) of this common disease is or are not known, and therefore prevention of the disease is not possible. Due to the multiple risk factors that have been described for feline hyperthyroidism, however, it is likely that more than one factor is involved in its pathogenesis. Continuous, lifelong exposure to environmental thyroid-disruptor chemicals or goitrogens in food or water, acting together or in an additive fashion, may lead to euthyroid goitre and ultimately to autonomous adenomatous hyperplasia, thyroid adenoma and hyperthyroidism. This review aims to summarise the available published evidence for the changes observed in the worldwide prevalence of the disease, as well as risk factors that may contribute to development of hyperthyroidism in susceptible cats.http://www.jsava.co.zatm201

NT-ProBNP and cardiac troponin I in virulent canine babesiosis

Although cardiac pathology and consequently elevated serum cardiac troponin I (cTnI) have been reported, clinically it remains difficult to diagnose cardiac involvement in canine babesiosis. Thus the use of cardiac biomarkers would be useful in determining if a dog with babesiosis also has concurrent cardiac dysfunction. The objectives of this study were to determine plasma N terminal brain natriuretic peptide (NT-proBNP) in canine babesiosis and if it is correlated with cTnI. Three groups of dogs with babesiosis were used: mild uncomplicated (Group 1), severe uncomplicated (Group 2), and complicated (Group 3), and a control group (Group 4) with 15 dogs per group. Each animal had the following determined: serum urea and creatinine, urea: creatinine ratio, cystatin-C, cTnI, blood lactate, plasma NT-proBNP, fractional shortening (FS), and blood pressure. The median NT-proBNP value in Groups 1–4 was 246, 650, 638, and 106 pmol/l. All 3 babesiosis groups had a statistically elevated NT-proBNP level compared to the control group and Groups 2 and 3 showed significantly higher values compared to Group 1. Median cTnI in Group 1–3 was 0.39, 0.4, and 1.45 ng/ml, respectively with the control group having concentrations below the detection limit (0.2 ng/ml). There was a significant difference in cTnI concentration between the control group and group 3 but no statistical difference between the other babesiosis groups. The study concluded that dogs with babesiosis showed elevated levels NT-proBNP and the more severe the disease process the greater the elevation. This elevation is earlier or independent of the increased cTnI.http://www.elsevier.com/locate/vetpa

Prevalence of and risk factors for feline hyperthyroidism in South Africa

Feline hyperthyroidism is a disease of middle-aged to older cats that has shown a marked increase in worldwide incidence within the last three decades as well as a marked geographic variation in prevalence. The exact pathogenesis of the disease still remains obscure and despite a plethora of epidemiological studies, clear risk factors have not been identified. The purpose of this study was to determine the prevalence of feline hyperthyroidism in South Africa and to identify potential risk factors. Serum total thyroxine (tT4) and thyroid stimulating hormone (cTSH) were measured in 302 cats aged 9 years and older that were presented at various veterinary clinics. In a few cats, serum free thyroxine (fT4) was also measured. At the time of blood sampling a questionnaire was completed regarding vaccination history, internal and external parasite control, diet and environment. The prevalence of hyperthyroidism (tT4> 50nmol/L or tT4 between 30-50 nmol/L with cTSH 50pmol/L) within this population was 7.0% with no significant difference in prevalence between healthy (5.1%) and sick (8.2%) cats. Cats ≥ 12years of age (OR= 4.3, p= 0.02) and cats with canned food in their diet (OR= 2.1, p= 0.1) were more likely to be diagnosed with hyperthyroidism. No significant relationship between vaccinations, parasite control or indoor environment and hyperthyroidism was observed. Hyperthyroid cats were more likely to present with weight loss (OR= 3.2, p= 0.01) and with a heart rate ≥ 200bpm (OR= 5, p= 0.01) than cats without the disease.The prevalence of feline hyperthyroidism in South Africa appears to be similar to that in cats in Japan and Portugal but less than that in cats in the UK and Germany. Risk factors for hyperthyroidism, previously found in other studies, specifically older age and eating canned food was present in this study population.Poster presented at the University of Pretoria, Faculty of Veterinary Science Faculty Day, August 25, 2016, Pretoria, South Africa.ab201