Mosquitoes are bothersome and deadly insects. Many atrocious diseases are spread through their bite, including lymphatic filariasis. Never heard of it? This disease passes from mosquito to human and travels into the lymph nodes (those ping-pong-ball-like organs in your neck and groin that govern the immune system). If undetected, the illness slowly depletes the immune system and can cause elephantiasis, which is distinguished by a thickening of the skin and swelling of body parts. More than 120 million people worldwide are infected with the disease, though it's not found in the United States.