Introduction

Disease means a change in the normal functions or well-being of farm animals which results in observable symptoms. It is an illness, unhealthy or abnormal condition in the body of farm animals.

It can also be defined as the absence of normal health due to infection (presence of pathogens in the body), nutritional deficiency and imbalance, hereditary and functional disorders as well as injuries.

Pathogens include bacteria, fungi, viruses, protozoan, etc.

These diseases cause a reduction in production, loss of appetite, loss of weight, slow growth rate, and death of an animal.