 More recently, the disease has become a problem in the lake itself as the endemic "B. nyassanus" has become an intermediate host.This change, first noticed in the mid-1980s, is possibly related to a decline in snail-eating cichlids (for example, "Trematocranus placodon") due to overfishing and/or a new strain of the bilharzia parasite.Unlike Lake Tanganyika with its many endemic freshwater crabs and shrimp, there are few such species in Lake Malawi.