Animal diseases are important because of animals' value in agricultural production and our food supply, and because about 60% of human diseases have an animal counterpart (think of swine flu, bird flu, anthrax, tularemia, rabies, toxoplasmosis, Kruetzfeld-Jacob disease, and many others).  Animals (wild and domestic) can serve a sentinel function for disease outbreaks.  Diseases can  spread from animals to humans, and vice versa.   And lessons learned from veterinary epidemiology can be applied to human populations - think of herd immunity, a term which was originally coined to describe the immunity of a herd of animals to disease if a certain critical proportion of them were vaccinated.  It is foolish to ignore disease epidemiology in animals if you want to keep the human population healthy.    

Thank you Jerry, 

I need to indestand

1- cumulative incidence

2- positive predictive value

3-   stratified sounding

thank you

Hi Zeineb, epidemiology helps in animal health because, just like in human health it helps you understand where diseases come from and how they spread  in animals. There are some particularities in veterinary epidemiology, for example spatial epidemiology is much more used to take in account the movement of flocks etc... even more interesting, you can combine human and animal epidemiology into "one health" epidemiology- understanding the interaction between humans, animals, and pathogens

to answer your specific questions:

1) the number of cumulative new cases of a give disease over a specific period of time. so for example, if your total study period is one year and you divide it into weeks, each week you add the new cases to the previous weeks to get your cumulative incidence

2)PPV is the proportion of individuals (or animals) who test positive to a diagnostic test, a screening procedure or fit a specific case definition who actually have the outcome your are interested in. If you pick up any epidmeiology textbook this will be explained in detail. It helps to have an understanding of what sensitivity, specificity and background prevalence are to understand ppv. If you don't havce a textbook, this is a good resource :  http://www.healthknowledge.org.uk/public-health-textbook/disease-causation-diagnostic/2c-diagnosis-screening/statistical-aspects-screening

3) I don't know what that is, do you mean stratified sampling?

http://www.healthknowledge.org.uk/public-health-textbook/disease-causation-diagnostic/2c-diagnosis-screening/statistical-aspects-screening

thank you so much Michael Edelstein