Animal disease patterns

Organic livestock production and animal disease patterns - an overview... 

Halpin, B. Patterns of Animal Disease Bailiere Tindall London, 1975. 

Joint capsule and cartilage of arthritic and healthy animals are similarly stained. The growth related lined pattern is observed in both arthritic and healthy animals. Disease related differences are found only in tissues relating to arthritic lesions. 

We know that metals lost to the environment will not degrade. We also know they affect plant, animal, and human health yet we are just beginning to relate environmental trace metals levels to health and disease patterns. 

Ideally, hygiene standards should be derived from the quantitative relations between the contaminant and its effects, i.e. X ppm of substances causes Y amount of harm. However such relations are very difficult to establish in humans. The problems involved have been considered in some detail by Atherley . Attempts have been made to relate human disease patterns to industrial experience, but unfortunately sufficient data do not exist. By using chemical analogy which assumes that similar chemicals have biologically similar effects and animal exposure experiments, the effects of harmful agents have been studied. 

The types of veterinary vaccine products available difler from country to country. This not only reflects commercial considerations but also disease patterns, which vary depending on location. As with human medicine, animal diseases difler with climactic conditions and so different vaccines are required in equatorial conditions when compared with those needed in northern Europe. Table 14.1 is neither comprehensive nor is it representative of every climactic area. In fact, it is largely (but not entirely) based on the United Kingdom and the vaccine products commercially available there. The table also shows that in the UK there only three enzootic disease vaccines available which are capable of causing disease in humans. Such vaccines are usually authorised, in spite of the obvious hazards and associated risks, either because the inactivated versions are not effective or if they are, they are not as efficacious as the live version. 

Some have also predicted a series of thirdhand impacts that might occur if the climate warms and becomes more dynamic. Wildlife populations would be affected (positively and negatively), as would some vegetative growth patterns. The home range of various animal and insect populations might shift, exposing people to diseases that were previously uncommon to their area, and so on. 

Phytochemicals have been the subject of many studies evaluating their effects in relation to common chronic human illnesses such as cancer and cardiovascular diseases. These studies encounter difficulties in using this information to influence the dietary patterns of consumers because in the past they have used models or experiments with animals. However, in the last decade, researchers have moved away from animal studies in favour of human cell models or human intervention studies. Scientists still need to determine the likely incidence of illness from exposure to known amounts of a given natural compound in the diet and specifically in relation to the complex matrices of whole foods. Therefore, it is inevitable that some animal studies have to be continued for toxicological studies. 

Some xenobiotics may have divergent mechanisms of autoimmune responses. For example, hydralazine demonstrates adduct reactivity as well as inhibition of DNA methylation [68,73], while procainamide inhibits DNA methylation, forms immunogenic NPA, and disrupts clonal selection in the thymus [68, 72, 74], It is this complicated pattern of effects that makes assessment of autoimmune potential in the laboratory for new xenobiotics almost impossible. Animal models can sometimes be recreated to resemble human disease [74], and thus may be useful for therapy considerations, but are difficult to utilize for screening chemicals for hazard potential due to the diverse nature of autoimmunity mechanisms and physiological presentation. While evidence supports many different mechanisms for xenobiotic-induced autoimmune reactions, none have conclusively demonstrated the critical events necessary to lead to the development of autoimmune disease. Therefore, it is difficult to predict or identify xenobiotics that might possess the potential to elicit autoimmune disorders. 

Epizootic 1. Denoting a temporal pattern of disease occurrence in an animal population in which the disease occurs with a frequency clearly in excess of the expected frequency in that population during a given time interval. 2. An outbreak (epidemic) of disease in an animal population often with the implication that it may also affect human populations. 

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