Some Causes of Diseases in Animals

Disease causes body functions to dysfunction or function improperly. Three principal reasons most often cited for the spread of diseases are poor sanitation, improper management and introduction of new animals into a herd.
There are many causes of disease in animals. Knowledge of what causes disease, and of how animals can get a disease, helps us to know how to prevent disease and to treat sick animals.
Parasites are organisms that have to live on or in other organisms, such as animals, in order to survive. Most parasites are easy to see, although some mites and the early stages of worms can only be seen under a microscope. Some live outside the animal, such as flies, lice, mites, fleas and ticks. Others such as flukes and round worms live inside an animal. They usually live in the stomach and intestines but also in other parts of the body such as the lungs and liver. Parasites cause a variety of diseases in animals.
Microbes or germs are usually too small to be seen with the naked eye, and only a microscope will enable you to see what a microbe looks like. Viruses and bacteria are the most common disease-causing pathogens. Other pathogens are fungi and protozoans.
Fungal diseases are caused by fungi, which are small organisms. Many disease-producing fungi live in the soil.
Protozoa are one celled and the simplest form of animal life. Some protozoa can live outside cells, especially the type that causes trichomonosis, a disease in cattle. Others need to live inside cells, and include those causing coccidiosis, redwater, heartwater and gallsickness.