The question asks us to identify the disease in which a mosquito-transmitted pathogen causes chronic inflammation of the lymphatic system. Let's examine the options:
Based on the above examination, the correct answer is:
Elephantiasis is the disease caused by mosquito-transmitted pathogens leading to chronic inflammation of the lymphatic system.
This understanding of each disease aligns with the given options where only Elephantiasis correlates directly with the mosquito transmission and lymphatic involvement. Hence, option (a) is the correct choice.