Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† căcŏēthĕs, is, n., = κακόηθες, τό (bad state or habit); in medic. lang., an obstinate, malignant disease, Cels. 5, 28, n 2; Plin. 24, 3, 3, § 7.
Plur. cacoëthe = κακοήθη, τά, Plin. 22, 25, 64, § 132; 24, 10, 47, § 78.
Hence,