Brucellosis has become so widespread in cattle in Counties Limerick, Cork (north), Tipperary and Kerry that the Southern Health Board has issued a public health warning about it.
The bacterial infection, which occurs in cattle, pigs, sheep and goats, can be passed on to humans who come in contact with diseased animals or through unpasteurised milk and cheese products.
Irish vets blame the ending of mandatory pre-movement testing of animals for the spread of the disease.
The Southern Health Board said the symptoms in humans often mimic severe flu and may take months to emerge. These are: intermittent fever, headaches, weakness, profuse sweating, joint pain, depression and weight loss. The disease can be successfully treated.