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Some conditions that might change an animal’s body temperature include: High body temperature Low body temperature Infections Shock Heat stroke Hypothermia ( exposure to cold ) Pain Severe disease Inflammation Anaesthesia Convulsion Poisoning Fever is also known as pyrexia and refers to an elevated temperature due to an infection. There are many more examples that can be found. In the dog for instance, even with severe disease, the temperature rarely exceeds 41 o C or falls below 36 o C. An interesting situation may occur in the pregnant bitch just prior to giving birth, where the temperature falls up to two degrees. TO DETERMINE AN ANIMAL’S TEMPERATURE A standard mercury thermometer is usually used. These can take a little getting used to initially. A magnified view is shown below. 35 6 7 8 9 40 1 2 The mercury (the silver liquid in the bulb) will rise up the thermometer with heat. It will then stay in the position of the highest temperature. 1 35 6 The numerals indicate the degrees centigrade, and are further broken down in to tenths of a degree. The temperature is determined by reading the top of the mercury, which is a silver colour, against the blue or white background. Try reading the examples below and then practice with your own thermometer using warm water (under the tap) to change the readings. 35 6 7 8 9 40 1 2 35 6 7 8 9 40 1 2 35 6 7 8 9 40 1 2 The readings in the above case are 36.6o C , 40 .0 o C, 38.8 o C Remember to use the tenth of a degree scale, and report the temperature using tenths of a degree. 2 VIRUSES Viruses are much smaller than bacteria and can only be seen using an electron microscope that magnifies in the order of 400,000 times. They have a unique structure that often resembles a crystalline shape than that of a living thing. Viruses live and reproduce only in the cells of plants and animals. Not all viruses are harmful, but many pathogenic ones are capable of causing contagious diseases (spread from animal to animal). Some examples of diseases caused by viruses include: Distemper A disease affecting the dog that can result in the death of the animal from convulsions. Feline Respiratory Disease Better known as cat flu. A highly contagious and sometimes serious disease of cats. Foot and mouth disease A debilitating disease of livestock that can have a dramatic effect on production of stock and a country’s economic situation ( you are unable to sell affected stock ) Human diseases Colds, measles, chicken pox, AID’s are all examples of human viral diseases. 3 PROTOZOANS Protozoans are single celled organisms that may be seen with the light microscope and magnification as little as 50 times. There are thousands of different species of protozoa found naturally in the environment on both land and in water. They have a useful role in the environment, being an important part of the ecosystem. In plant eating animals such as cattle and horses they form an important part of the microbial flora of the stomach and intestine that digest plant material. However, occasionally these organisms can cause disease, especially if the host animal is stressed or has an immune system that is not working properly. Some examples of diseases caused by protozoans include: Coccidiosis A disease causing severe enteritis (diarrhoea features) in animals, often blood stained and resulting in death. Toxoplasmosis A mild disease of cats, which may cause diarrhoea, but may also go unnoticed, with cats carrying the disease. It is of concern as it may cause abortion in women, if contracted from cats. Giardia infection A common parasite of the intestine that can cause diarrhoea in animals and man. 4 NON INFECTIOUS DISEASES This broad category of disease describes all those other diseases that are not caused by infectious organisms. That is, they are not caused by bacteria or viruses or any other living creature, but by other causes. This is a very large and varied group of diseases and it is useful to further classify these into more specific groups. One such classification is shown below: Nutritional diseases Physical diseases or trauma Hormonal diseases Chemical diseases Degenerative diseases Immunological diseases Metabolic diseases Psychological diseases Inherited diseases Unknown causes 5 Nutritional diseases These are caused by an excess or deficiency of components of the diet. Rickets is a disease that may be seen with dietary deficiencies of calcium or Vitamin D resulting in misshapen and weak bones. Obesity is another example that may be caused by excessive food intake. There are hundreds of diseases that have been identified and fit into this category. Hormonal diseases These diseases are associated with an excess or deficiency of a particular hormone. Hormones are chemical messengers in the body, and abnormal levels of hormones cause abnormal body function. Diabetes mellitus is a disease that features excessive drinking and urinating, weight loss and other body changes. It is caused by a deficiency of the hormone insulin. Dozens of other hormonal diseases have been identified. Degenerative diseases These diseases are associated with a breakdown or wearing of tissues. Age or excessive use often contribute to these diseases. Arthritis is an example where the animal’s joints become worn and painful. There are many examples of degenerative diseases seen in animals 6 TRANSMISSION OF DISEASES Having discussed how a disease might leave and enter an animal, we now need to consider how the disease is passed or transmitted from one animal to another. Diseases may be transmitted either directly or indirectly. DIRECT DISEASE TRANSMISSION INDIRECT DIRECT TRANSMISSION Here the animals have direct contact and the disease causing organisms will be transferred from one animal to the next. Some actions that will permit direct transmission include: touching sucking licking biting breathing , sneezing and coughing sexual contact 7 SKIN The skin of an animal is exposed to the environment and other animals, and may often be in contact with potentially disease causing organisms. The skin acts in several ways to prevent micro - organisms entering the body, they include: Physical Barrier If the skin remains unbroken, the tough outer layer (the epidermis) acts as a physical barrier preventing the entry of micro - organisms. For an infectious organism to enter through the skin, the skin must be damaged as might happen with a cut or graze, or be punctured as might occur in a fight or by insect bites. Production of chemicals Various areas of skin produce sweat, oils and wax. Most of these chemicals are harmful to many micro - organisms. Useful micro - organisms Populations of bacteria live on the skin of animals without causing any harm. These are referred to as normal flora. They live on the skin and are unaffected by the normal defences of animal. Their presence will discourage the action of foreign, potentially disease causing bacteria as they physically take up space where other organisms might try to invade and they will produce chemicals that are toxic to (kill) other bacteria. 8 ASSIGNMENT 4A STUDENTS NAME Vet Medical Nursing 1 ______________________________________ Answer the following questions 1. Describe 3 ways in which the skin acts to prevent infectious micro - organisms entering the body ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ 2. Describe how cilia in the respiratory tract act as a barrier to infection. ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ 3. List four chemicals that mucous membranes produce that may be harmful to micro - organisms 4 ________________________ _____________________________ ________________________ _____________________________ List the five main signs of inflammation ________________________ _____________________________ ________________________ _____________________________ ________________________ 9