2 History (Anamnesis)

Disease problems in veterinary medicine are invariably presented to the clinician through the medium of the owner's complaint, which is a re­quest for professional assistance. This provides the opportunity to obtain all the essential in­formation relating to the circumstances of the immediate disease problem. This procedure is termed 'taking the history' and it is a very important—if not the most important—facet of the whole procedure of clinical examination. By means of appropriate questions, phrased in the minimum of technical terms, the veterinarian must try to obtain from the owner or attendant of the animal all the information that will assist the examination and ensure the accuracy of the diagnosis. When a history is being obtained, allowance should be made for the personality, knowledge and ability of the informant to com­municate. Generally speaking, the better edu­cated the person concerned, the more likely it is that only accurate observations will be reported.

It is advisable for the clinician to check the validity of the history as related and, when pos­sible, to evaluate and supplement it by making a detailed, systematic examination. An incomplete history can be misleading, and even stock owners themselves may attempt to excuse their neglect to obtain professional help at an earlier stage by grossly understating the length of time the animal has been ill. Whenever possible lead­ing questions should be avoided, and an attempt should be made to establish good rapport by instilling confidence in the person concerned by exhibiting a friendly manner. The confidence of animal owners is most readily gained when the veterinarian is known by repute to provide a prompt and highly efficient service. The ability to obtain a satisfactory history depends upon a thorough knowledge of how animals react to disease, and increases with widening experience. If, at a later stage during the particular clinical examination of the animal, evidence emerges which appears to throw doubt on any aspect of the history, further enquiries should be made in order to clarify the situation. It is not possible to specify all the questions that must be asked in individual cases, but, in general, routine con­formity is achieved and all aspects likely to be of significance are covered by applying them under the headings of immediate, past and general history, the latter to include consideration of the environment.

Immediate History

This relates to the sequence of events associa­ted with the period of time that the animal has been ill. It is important to determine the chrono­logical order in which the more important chan­ges in behaviour and in physiological functions were observed. Specific questions should there­fore be centred on such aspects as appetite for food or drink, defaecation, urination, respira­tion, sweating, physical activity, milk production, growth, gait, posture, voice, odour, etc. The questions should be designed to ascertain the degree and nature of any departure from normal in any of these functions.

When a proportion of a group or flock of animals is affected, a typical case should be selected as a basis for establishing the history. Significant information may be obtained, in this situation, from laboratory examination of speci­mens from a proportion of the living, affected animals, or autopsy investigations in a few selec­ted cases. Information relating to any preceding

surgical, therapeutic or prophylactic procedure such as docking, castration, shearing, vaccina­tion or administration of anthelmintics, parasiti­cides or other chemotherapeutic substances may be important. The nature of the disease might be indicated by assessing the morbidity rate (expressed as the proportion of animals clini­cally affected compared with the total number at risk) and the mortality rate (the proportion of affected animals which die). It is important to realize that a proportion of animals, in a herd or flock affected by disease, may not themselves manifest overt clinical signs; in the majority of such instances productive capacity is impaired.

Particularly in those countries where therapeu­tic substances are freely available for treatment of animals, but also elsewhere, it is essential to determine whether any treatment has, in fact, been given and, if so, the nature and dose of the preparation used. Due allowance must be made for the effect of such treatment in modifying the clinical signs of disease. Many of the thera­peutic substances now in common use are cap­able of producing clinical signs (iatrogenic disease) in animals when they are administered in too large doses or for too long a time. It should be remembered that unless the client is known to him, the veterinarian must satisfy himself that he has not been presented with a case that is already receiving professional attention, thus avoiding supersession.

Past History

In this respect, information should be obtained relating to the nature and timing of any previous illness which had affected the individual animal or group. Details regarding clinical features, diagnosis, treatments, morbidity and mortality rates, post mortem observations, etc., should be obtained. It is pertinent, at this juncture, to ascertain the system of animal replacement on the farm or in the home, with the object of determining whether there has been any recent introduction from outside sources. In the event that this has occurred, then further enquiries should be made concerning the health history and status of the source animals. The period for retrospective enquiry may extend to weeks, months or even years according to the informa­tion that is made available and the evidence obtained by the clinician.

General History and Consideration of the Environment

The examination of an animal must be accom­panied by a consideration of its surroundings and circumstances. This is more necessary in the case of animals in groups than for individual animals, although even in the case of domestic pets the environmental aspects should not be completely overlooked. In this context considera­tion might be given to the epidemiological signi­ficance of the relationship between humans and animals. The consideration of the surroundings and circumstances should include an enquiry into such aspects of animal husbandry as nutri­tion, breeding policy, housing, etc., which might reveal information of diagnostic significance. In relation to diet, any recent change in character or constitution should be ascertained. This brings into focus the need to determine whether the ailing animal is being house-fed or grazing. Within this context, it is necessary to consider the geographical and seasonal incidence of disease for a particular region. Knowledge of the local topography is of value in relation to vector-borne diseases including louping-ill, babesiasis, anaplasmosis, trypanosomiasis, African horse sickness, Rift Valley fever and blue tongue, etc., and a number of other diseases such as fascioliasis, hypocuprosis, cobalt deficiency, etc. Nutri­tional diseases are, in most instances, group problems, so that a number of animals are more or less simultaneously affected. Domestic pets, however, are still occasionally found to be suf­fering from serious nutritional deficiency syn­dromes.

During the grazing season, a study of the pasture composition, along with identification of specific poisonous species, including ergotized grass or rye, or those which possess the ability selectively to absorb potentially toxic elements (selenium, copper), is advisable in certain cir­cumstances. Stall-fed animals, in comparison with those at pasture, are in most instances fed on a nutritionally balanced diet; the quality of pasture is not easily assessed, so that, with the exception of certain recognized diseases, a nutritional deficiency may exist for quite a time before it is identified. A sudden change from stall to lush pasture feeding, during the spring season, may predispose to hypomagnesaemic tetany or rickets, even though the herbage com­position is normal. Grazing animals, more particularly when adolescent, are exposed to the risk of acquiring various parasitic infestations, e.g. various forms of parasitic gastroenteritis in cattle and sheep, lungworm infestation in cattle, strongylosis in horses. By the adoption of improved fertilization programmes and the in­clusion of more productive strains of plants, grazing of animals is becoming more intensive, thus increasing the incidence of parasitic diseases. The standard of grassland and grazing stock management of the particular farm should, therefore, receive appropriate consideration, with, where it is thought advisable, an examina­tion of the pasture, grazing control and fodder conservation methods and the conserved fodder.

Housed animals are exposed to the risk of being over- or underfed or of receiving diets which are incomplete or inadequate in respect of some essential constituents. Farm compoun­ded foods are more likely than those commer­cially produced to be nutritionally inadequate. The quality of the ingredients may have an un­desirable effect. Grain of good quality, recog­nized by weighing heavier per unit volume, may cause digestive disturbance if the ration is com­pounded on a volume rather than a weight basis. In this context, the proportion of fibre or rough­age in the diet of intensively produced animals being fed on cereal diets is a matter of some im­portance. A sudden change from a high- to a low-fibre, crushed barley diet causes lactic acidaemia in young cattle, unless care is taken to make the change gradually and to ensure an adequate roughage intake. The quality of the conserved fodder should be considered in rela­tion to ragwort or sweet clover poisoning. In the case of ensiled grass, a product which has a high butyric acid content will be a cause of primary ketosis in cattle. Imported foodstuffs, particularly those of animal origin, are a possible source of entry for such conditions as foot-and-mouth disease, swine fever, anthrax and salmonellosis.

The presence of old flaking paint on wood­work, or evidence of recent painting, may be valuable knowledge in relation to lead poisoning in calves. The quality of the drinking water may be important because of possible contamination with organic or inorganic substances, or infec­tive agents, e.g. fluorine in artesian and subartesian waters, nitrate in shallow water drained off soil rich in organic matter or contaminated by silage effluent, algae in stagnant pools, ponds or shallow lakes may contain neurotoxic and hepatotoxic agents, and effluents from industrial processes may contaminate rivers. In the case of a stalled or housed animal, said to be off its food, investigation may reveal that the water supply is polluted or inadequate, or that the fodder within the animal's reach is stale or otherwise unpalatable. An adequate, and where possible continuous, water supply is a prime factor in maintaining animal health and pro­duction; in the case of pigs, water deprivation is an essential feature of salt poisoning. Faecal contamination of rivers or streams by grazing cattle is a recognized means of dissemination of salmonellae and other pathogenic bacteria.

Feeding methods should also be investigated because they may contribute to low productivity or disease. Inadequate trough space for pigs and calves and for older cattle in yards leads to over­eating on the part of the vigorous animals and partial starvation in the smaller, weaker ones. The design or fittings of a box, stall, pen or kennel may suggest the possibility of certain kinds of injury, or of exposure to draughts or sudden changes in environmental temperature. The state of the bedding may reveal whether the animal has been restless, either moving about aimlessly or circling clockwise or anti­clockwise.

In the context of general management there are many factors to be considered, neglect of which can contribute to the development of disease. Adequate hygienic standards are of vital importance in relation to milk production, par­turition and the early postnatal period. Other factors of importance in animal health include adequate house space, satisfactory ventilation, reasonable facilities for effluent treatment and disposal and opportunity for exercise. An inves­tigation of the breeding programmes may reveal features of significance when line breeding has led to the appearance of an inherited genetic defect. It is necessary to appreciate that selection for high productivity may result in breeds or families of animals which are more susceptible to certain diseases or which have inherited a greater than normal requirement for a specific nutrient (genototrophic disease). Consideration of the breeding management may reveal features of significance; for instance when calvings are arranged to occur early in the year the incidence of ketosis, hypomagnesaemia and calf scour may be increased. An early lambing programme, more particularly in lowland flocks, may be associated with a high incidence of pregnancy toxaemia.

Climatic conditions have an influence on many diseases. The relationship between tem­perature, high rainfall and clinical fascioliasis in sheep and cattle is well recognized. Similarly, warmth and humidity have an important in­fluence on the larval stages of the internal nematode parasites which cause gastroenteritis and parasitic bronchopneumonia. Intermittent periods of warm, wet weather and cold moist conditions during the spring season may favour the appearance of hypomagnesaemic tetany in cattle and sheep. A mild, damp spring season may be responsible for the appearance of rachitogenic effects in young grazing animals in par­ticular, because of the high carotene content in the lush pasture. Conversely a period of drought may be sufficiently prolonged to cause vitamin A deficiency in animals grazing the dried-out herbage. Hot, humid weather is associated with anhidrosis in non-indigenous horses and dairy cattle. Contamination of pastures by fumes and other effluents from brick works, ore smelters, aluminium processing plants, mines, etc., is more likely to lead to significant intoxication problems in animals grazing pasture situated in the direction of the prevailing wind or down­stream.