Biological agents in the work environment include viruses, rickettsiae, bacteria, and parasites of various types. Occupational infectious diseases occur in industry and mining. The common infectious and parasitic occupational diseases include anthrax (wool-sorting and handling of infected hides), brucellosis (contact with infected animals), tetanus (from infected wounds), ancylostomiasis (hookworm disease) and schistosomiasis (bilharzia). Fungi from organic dusts, such as bagasse and cocoa, may cause myotic respiratory diseases or skin infections. Diseases transmitted from animal to man in agricultural work are of common occurrence in view of the fact that agriculture is the major economic activity in developing countries. In such work, infectious and parasitic diseases may result from exposure to contaminated water or to insects.
The case of schistosomiasis as an occupational disease is an example. In endemic areas in Brazil, workers in plantations are exposed at work to infected water and soil. It was found that the proportion of stool-positive cases was 59% among exposed workers, as compared with only 10% among other workers in the same area who did not come into contact with infected water or soil.