Diseases can have a hugely detrimental effect on livestock - take for example the epidemics of Rinderpest in Africa which have decimated cattle herds several times in the past hundred years; or Foot and Mouth in Europe; or BSE (Mad Cow Disease) in England. Other diseases, like nagana (cattle sleeping sickness or trypanosomosis) may have a less dramatic, but more insidious effect in that they can drastically reduce productivity, but may not kill the more resistant varieties of animals.
We need to know about the geography of diseases so that we can plan control or eradication programmes and monitor their spread or recession. If we know where they are, we have a reasonable chance of working out what other areas are likely to be at risk and put measures in place to reduce the likelihood of neighbouring livestock being infected. We can also assess the likely impact of the disease - perhaps in terms of the number of animals infected, which allows us to evaluate the economic arguments for investing in control or vaccination programmes or perhaps in terms of the people whose livelihoods are being most affected and who therefore need the most help.
There is a global animal disease monitoring system - run by the Office International des Epizooties (OIE) based in Paris - which provides annual reports of disease occurrence in each country. Valuable as this is, it cannot provide the detailed maps showing how diseases are distributed within countries that are needed to target remedial action at specific locations. FAO has recently commissioned research aimed at producing such maps by using the available satellite imagery to predict disease distributions. Three examples have been provided: one - trypanosomosis - which looks at the flies that spread rather than actually cause the disease (called disease vectors); the second, the specific case of Screwworm in the Middle East; and third- Other Diseases - which considers a range of diseases in more general terms.