The only result was an increase in the numbers of the diseased.
For hundreds of years this idea of diabolic possession was steadily developed.

It was believed that devils entered into animals, and animals were accordingly exorcised, tried, tortured, convicted, and executed.
The great St.Ambrose tells us that a priest, while saying mass, was troubled by the croaking of frogs in a neighbouring marsh; that he exorcised them, and so stopped their noise.

St.Bernard, as the monkish chroniclers tell us, mounting the pulpit to preach in his abbey, was interrupted by a cloud of flies; straightway the saint uttered the sacred formula of excommunication, when the flies fell dead upon the pavement in heaps, and were cast out with shovels! A formula of exorcism attributed to a saint of the ninth century, which remained in use down to a recent period, especially declares insects injurious to crops to be possessed of evil spirits, and names, among the animals to be excommunicated or exorcised, mice, moles, and serpents.

The use of exorcism against caterpillars and grasshoppers was also common.

In the thirteenth century a Bishop of Lausanne, finding that the eels in Lake Leman troubled the fishermen, attempted to remove the difficulty by exorcism, and two centuries later one of his successors excommunicated all the May-bugs in the diocese.