The first step in disease recognition and control is being able to recognise when an animal or group of animals is unwell.

By compiling information from the history of an animal or group of animals, conducting a physical examination, and undertaking special testing (if necessary) the veterinarian or government inspector is generally able to determine the cause of a condition or disease.

The following list outlines some of the more common signs that can be looked out for in an ill animal: 

  • Common signs of an ill or injured animal
  • The animal not eating as much as usual – this is usually the first sign you will notice
  • It may also drink more or less water than normal, depending on the illness.
  • An animal standing by itself away from the herd
  • The animal not getting up and walking to the feed bunk - A very sick animal will lie down for long periods and will not get up when approached.
  • Animal limping or dragging a leg
  • Discharge from eyes, nose, or vaginal area
  • There may be abnormal lumps
  • The eyes may be dull and the mucous membranes may have changed colour. Deep red membranes indicate fever; pale membranes show anaemia; yellow membranes indicate a liver disorder, while blue-red membranes show heart and circulatory problems, or pneumonia.
  • Animal making unusual noise (bellowing, grunting)
  • Animal acting uncomfortable, getting up and down
  • The animal might be sweating. A cold sweat indicates pain while a hot sweat indicates fever. If the animal is in pain it will probably be restless (getting up and down and pacing about), and it may even be groaning
  • Diarrhoea or straining to defecate
  • Animal not defecating or with very little stool
  • Animal urinating a lot, or not as much as usual
  • Marked weight loss or gain
  • The coat will look dull and dry, and the hairs may stand up.
  • There may the presence of open sores, dandruff, or the loss of hair or fur from the body
  • Behavioural signs - Recognise any significant differences in the behaviour of an animal such as increases in viciousness, lethargy or any other abnormal signs such as excessive head shaking, scratching, licking or biting of certain parts of the body
  • The vital signs of a sick animal will change. The temperature may go up or down. A rise in temperature of one or two degrees usually indicates pain, while a rise of more usually indicates infection.
  • The rate of respiration, and the way the animal breathes could also slow changes. With pain or infection, breathing becomes more rapid. In a very sick animal, breathing can be laboured and shallow.
  • A slightly increased pulse rate suggests pain, while a rapid pulse suggests fever. An irregular pulse can indicate heart trouble. In a very sick animal, the pulse is weak and feeble.
  • A sick animal may also possess foul breath or excessive tarter deposits on the teeth


Differential diagnosis is the process of weighing the probability of one disease versus that of other diseases possibly accounting for an animal’s illness, condition or death. It involves comparing and contrasting the signs, symptoms, and laboratory findings of two or more diseases to determine which is causing the animal's condition. To assist in this process it is important to gather as much relevant information as possible. The following lesson discusses how information is collected and used to identify disease conditions.

Background history

Recognising the differences between what is normal and what is abnormal about an animal or group of animals forms the basic foundation for good animal husbandry and veterinary medicine.

Using your powers of observation can be very important for the early recognition of subtle abnormalities. Observation of behavioural changes, changes in energy levels, elimination changes (urine and faeces) and physical changes are important, but don't just evaluate the animal, evaluate its environment, too.

Ask questions such as: How is the animal housed? What are the climatic conditions? What plants do they have access to? Are they hand fed or do they graze? This type of information is very important in the process of determining what disease processes are occurring.

In addition to evaluating the animal’s environment, recording and compiling animal information such as type and condition of animals, age, sex, number of affected animals, and progression of disease are the first steps in the disease recognition process.

When dealing with diseased animals it is important to remember that some diseases are zoonoses (they are transmissible to humans). When undertaking a physical examination or post mortem examination, wear protective clothing, gloves and overalls.

Physical examination

A physical examination is the next step in identifying diseases or conditions in animals. The veterinarian will examine the whole animal and not just the obviously affected area. It is helpful to start by examining the non-painful areas and then moving on to those areas that show discomfort. If an animal is in a lot of pain, the veterinarian may suggest lightly anesthetizing the animal so a more complete exam can be safely conducted.

The exam will generally include:

  • Weighing the animal, taking the temperature
  • Listening to the heart and lungs
  • Checking eyes, ears, nose, etc.
  • Examining the skin for any trauma or puncture wounds
  • Examining all the limbs
  • Watching the animal move about the exam room or outside on the grass
  • Performing special manipulations of various body parts e.g., neck, limbs