Step 1: Filaria disease is caused by parasitic worms, and the main causative agents are nematodes (roundworms) of the genus \textit{Wuchereria} and \textit{Brugia}.
The zoological name of the most common causative agent of Filaria disease is:
\[
\textit{Wuchereria bancrofti}
\]
Step 2: This parasitic worm is responsible for causing lymphatic filariasis (commonly known as elephantiasis). The larvae of the parasite are transmitted to humans through the bite of infected mosquitoes, primarily \textit{Culex} species.