Epidemiology is the field of science that deals with the relationships of the various factors which determine the frequencies and distributions of an infectious process, a disease or a physiological state in a human community (Maxcy, 1965). Epizootiology on the other hand is the field of science dealing with the relationships of the various factors which determine the frequencies and distributions of infectious diseases among animals.
Leptospirosis is an infectious disease caused by pathogenic, spiral bacteria belonging to the genus Leptospira, the family Leptospiracae and the order Spirochaetales. It's distribution is worldwide (sparing the polar regions) and it occurs with the greatest frequency in the tropics (Jezior, 2001). Humans and a wide range of animals including mammals, birds, amphibians and reptiles are affected. Animal urine is the most important vehicle of zoonotic infection with leptospirosis. The reservoir hosts are rodents, household pets like cats and dogs as well as farm animals. In Africa, the rodents that scavenge freely in paddocks, homes, water ponds, sewers and farms are potential sources of infection (Ezeh et al; 1989). Other studies done in Nigeria show that there is evidence of leptospirosis among sheep, cattle and goats (Ezeh et al, 1989; Agunloye, 2002). Many slaughter houses and abattoirs are not furnished with good drainage systems. Consequently, some of these open gutters overflow and the flood may be carried kilometres away from the source, especially during the rainy season. Through this, micro organisms like Leptospira are widely disseminated. Leptospirosis causes death in 10% of humans affected and is responsible for some of the cases referred to as pyrexia of unknown origin (P.U.O.) in human hospitals. It also causes death and abortion among other conditions in affected animals. This paper highlights the importance of epidemiology/epizootiology in the diagnosis, prevention and control of leptrospirosis in man and animals.