The Coombs' test in veterinary medicine: past, present, future

The Coombs' test, also known as the antiglobulin test, is used most frequently in veterinary medicine as an aid in the diagnosis of immune-mediated hemolytic anemia. The test also is used widely in human medicine to screen for red blood cell alloantibodies. Polyspecific reagents for veterinary use typically contain anti-IgG, anti-IgM, and anti-C3. Monospecific reagents also are available. False-positive and false-negative test results can be obtained. Inadequate sensitivity of the standard test in human and veterinary medicine has necessitated development of alternate, more sensitive technologies.     

The influence of veterinary epidemiology on public health: past, present and future

This paper summarizes a presentation given at the Association for Veterinary Epidemiology and Preventive Medicine sponsored Calvin W. Schwabe symposium honouring the lifetime achievements of Dr. S. Wayne Martin. While the concepts were amalgamated from many sources, the examples were primarily selected to represent areas where Wayne Martin has been an active researcher and educator. The purpose was to describe the impact of veterinary epidemiology on public health in the past and present and to consider the future of veterinary epidemiology in public health. Veterinary medicine contributes to public health not only in the area of zoonotic disease prevention and control, but also through contributions to animal health, comparative and basic medical research, and population and environmental health. Veterinary epidemiologists contribute to both research in public health and the practice of public health through a wide range of methodological approaches and via the networks of trained epidemiologists working in the area. The contributions of veterinary epidemiologists have resulted in significant improvements in human health. There are considerable challenges and opportunities facing veterinary epidemiologists working in the public health area in the future. Meeting these needs will require continued integration between veterinary and human public health research and practice, and enhanced communication of both content and context expertise.     

An introduction to principles of veterinary clinical pharmacology: The elimination of drugs

Abstract

Extract

Drug elimination refers to all the processes that operate to reduce the effective concentration of drug in the body fluids. Metabolism, storage and excretion are the three mechanisms whereby drugs are ultimately removed from their sites of action. Most drugs undergo metabolic transformation in the body — i.e., biotransformation — to more polar products with diminished or no activity. The principal site of drug biotransformation is the liver. However, biotransformation may also take place to varying extents in other tissues, including the intestinal mucosa, the blood plasma and the renal epithelium, and by the action of gut microflora. The most common pathways of drug metabolism involve oxidation, reduction, hydrolysis and conjugation. Very often a drug is subjected to several competing pathways simultaneously, and the extent of formation of the various metabolites depends on the relative rates of the various metabolic processes. In addition, metabolic reactions frequently proceed sequentially; oxidation, reduction), or hydrolysis reactions are followed by conjugation of products of the initial reaction. Numerous factors may influence the metabolism and, consequently, the activity of a chemical agent. These factors include dose and frequency of administration of the drug, species and strain of animal, route of administration, diet and nutritional status, liver and kidney function, age of animal, time of day, chronic administraton and the previous or concurrent administration of, or exposure to, certain chemical agents that may inhibit or induce important metabolic processes. The effects of biotransformation are complex. Usually the metabolites formed are more polar, less lipid-soluble, more ionized at physiological pH values, and are distributed in a smaller volume than the parent drug. For these reasons drug metabolism frequently leads to an accelerated termination of pharmacological activity. Often, metabolic alteration of structure is a prerequisite, to efficient clearance by the excretory organs. Many drug conjugates are excreted into urine and bile by carrier-mediated transport mechanisms which allow foreign compounds to be cleared very rapidly from plasma. Deposition and storage of drugs in, fat depots, in the reticuloendothelial system and in bone play significant roles in the removal from the circulation of lipid-soluble agents, colloidal substances and heavy metals, respectively. Removal of unchanged drug from the body via the kidney is the principal route of elimination of drugs that are water-soluble; this includes organic electrolytes that are predominantly ionized at the physiological pH reaction. The excretion rate of a drug depends upon the volume of distribution and extent of plasma protein binding of the drug and the following renal factors: glomerular filtration rate, extent of non-ionic back-diffusion of the drug from glomerular ultrafiltrate to blood plasma (pH and pK_a dependent) and degree of carrier-mediated excretion or reabsorption by the renal tubules. Variation in each of these factors can produce clinically significant changes in action of certain drugs, but changes in glomerular filtration rate will alter significantly the duration of action of all drugs that are eliminated from the body mainly by renal excretion. A drug may be excreted by the liver cells into bile and then pass into the intestine. Species variation in the extent of bilary excreton of drugs is likely to occur with compounds of molecular weight between 300 and 500 (Williams, 1971 Williams, R. T. 1971. “Species variations in drug biotransformations”. In Fundamentals of Drug Metabolism and Drug Disposition, Edited by: LaDu, B. N., Mandel, H. G. and Way, E. L. 187–205. Baltimore: Williams &; Wilkins. In [Google Scholar]). The main importance of the biliary route of excretion is for the elimination of certain organic anions and cations that cannot be reabsorbed from the intestine because they are ionized at the intestinal reaction. It is evident that comprehensive appreciation of what occurs followng drug administration to either man or animals is possible only when pharmacokinetic analyses complement pharmacodynamic studies.     

An introduction to principles of veterinary clinical pharmacology: General principles

Three hundred and sixty goats, pregnant from an estimated 72 days to almost full-term, aborted between 30 and 50 hours afterreceiving 0.25 or 0.5ml cloprostenol by subcutaneous or intramuscular injection. Despite close observation, no goat was seen aborting. All membranes and some foetal limbs were consumed, afterwhich the foetuses (and three live kids) were abandoned.

Fourteen goats died from blood poisoning due to CI. chauvoei between 30 and 40 hours after aborting. It is recommended that an immunisation programme precede the induction of abortion or premature parturition in the goat.     

Non-payment of veterinary bills in The Netherlands

Non-payment of bills is a phenomenon that has grave economic consequences for all entrepreneurs, veterinary practitioners included. Little in depth research has been performed into the non-payment of veterinary bills. The aim of this study was to quantify the non-payment of bills in Dutch veterinary practices and to investigate the procedures implemented in the case of non-payment and their effectiveness. Non-payment of bills is a potential source of a substantial loss of income in Dutch veterinary practices. Even though veterinarians actively tried to collect the money owed them, often bills were paid very late or were paid in part only.     

Chirality: a major issue in veterinary pharmacology

The sole purpose of this comment is to draw attention to the significance of enantiomorphism in the interpretation of pharmacokinetic/pharmacodynamic studies of drugs that are present in dosage forms as racemates. The proportion of the enantiomers formed from a racemate can vary in different animal species, and both the pharmacokinetic behaviour and pharmacodynamic activity can differ between the enantiomers. As a consequence, the pharmacological effects produced by a racemic drug represent the combined effects of the enantiomers formed in the particular species of animal. Enantiomorphism has a major influence on the prediction of dosage regimens for different animal species.     

The future of veterinary endoscopy

The developing areas of video endoscopy, endoscopic ultrasonography, and small-bowel endoscopy are discussed in this article, and new endoscopic approaches to strictures and bleeding lesions of the gastrointestinal tract are presented. The potential applications of these techniques in veterinary medicine are left to the imagination of the reader.     

The future of veterinary parasitology

Current evidence suggests research in veterinary parasitology is in decline despite its importance. This is particularly true in the UK where research funds have been diverted into BSE. Decline in interest in veterinary parasitology is at least in part due to the success of major pharmaceutical companies in producing a range of effective and safe anti-parasitic drugs. Research is needed because of the effects of parasites on animal welfare and the economic costs of parasites. However, there is little information on the actual costs of animal parasites. Another major reason for research is the development of drug resistance in protozoa, helminths and arthropods of veterinary importance. This is a serious problem particularly for sheep and goats in the southern hemisphere. A prioritised list of research requirements is suggested: (i) new drugs; (ii) resistance management; (iii) vaccines; (iv) breeding for resistance; (v) improved diagnostics; (vi) zoonoses; (vii) global warming and parasites. There is a major political challenge to raise the profile of veterinary parasitology and thus the funding essential for its advancement and the continued welfare and productivity of animals.     

Current models in pharmacokinetics: Applications in veterinary pharmacology

Major advances in developing models for pharmacokinetic studies have been made in recent years, and different approaches can now be employed. These include the use of (1) compartmental models, (2) non-compartmental models, (3) physiological models, (4) population pharmacokinetic models, and (5) pharmacokinetic-pharmacodynamic models.Each of these approaches has both advantages and disadvantages. The important question of which of these is ideal in veterinary pharmacokinetics has no simple answer. The selection and application of any one approach would depend on a number of factors, such as (1) the purpose of the study, (2) physicochemical properties and actions of drug, (3) specificity and sensitivity of the analytical methodology, (4) species of the animal, and (5) availability of funds.This paper reviews the models available for pharmacokinetic studies and indicates their possible application in veterinary pharmacology.