The presence of which parasite-related condition could result in diarrhea in rabbits?

Coccidiosis is a parasitic infection in rabbits caused by protozoan parasites known as coccidia. This condition primarily affects the intestinal tract, leading to severe gastrointestinal upset and subsequently causing diarrhea. Coccidiosis is particularly concerning in young or immunocompromised rabbits, as it can result in serious health issues if not treated promptly. The parasites disrupt normal digestion and absorption of nutrients, which contributes to the diarrhea observed in affected rabbits.

Other conditions listed, such as myxomatosis and VHD, are viral diseases that affect rabbits but do not directly cause diarrhea as a primary symptom. Moreover, fleas are external parasites that can lead to skin irritation but are not known to directly lead to diarrhea. Therefore, the association of coccidiosis with digestive distress makes it the condition most likely to result in diarrhea in rabbits.