The term 'Nagana Carrier' refers to the TSETSE fly, which is a six-letter insect found in Africa. The TSETSE fly is a carrier of Nagana, a disease caused by the protozoan parasite Trypanosoma brucei. This disease affects both humans and animals, causing fever, anemia, and neurological symptoms. The TSETSE fly is the only known vector for the disease, and it is responsible for transmitting the parasite from one host to another.