81824
Parasites increase their own fitness by exploiting hosts for resources necessary for their survival , in particular by feeding on them and by using intermediate ( secondary ) hosts to assist in their transmission from one definitive ( primary ) host to another .
 transmission
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 transmission