Complex sentence: Hansson (1977) showed that direct transmission of the nematode from mustelid to mustelid did not occur, nor did infection occur when the mustelid was fed on small rodents, amphibians, molluscs, arthropods, or earthworms.
Split into simpler sentences: Hansson (1977) showed that direct transmission of the nematode from mustelid to mustelid did not occur. Nor did infection occur when the mustelid was fed on small rodents, amphibia, molluscs, arthropods or earthworms.