adverseeffects animaldiseases animalhealth anthropology complications congresses diseases ecology effectofenvironmenton energymetabolism eye eyediseases genetics geneticvariation gn289g32751986 humanbeings humanpopulationgenetics malnutrition nutritiondisorders physical physicalexertion physiologicalaspects population qu125c2361984 sf781i342004 tropicalmedicine tropics veterinarymedicine veterinarytropicalmedicine work workcapacityevaluation