The only place you need malaria prophylaxis in Nepal is in the Terrai or lowlands where there is a safari park. You don’t get malaria in most of Nepal because of the altitude (Kathmandu is at 1300 m.) – mosquitoes don’t like heights!

If you travel there via an endemic area e.g. Delhi ,you need Malaria prophylaxis as one poor chap got bitten by a malaria carrying mosquito on a forty minute stop-over in Delhi!!!