Which of the following is NOT a mosquito-borne disease?

1. A

   Dengue fever

   (a) Dengue fever. Dengue is an Aedes-mosquito flavivirus disease. It is mosquito-borne, so it is not the odd disease on a ‘not mosquito-borne’ reading of these four names.

2. B

   Filariasis

   (b) Filariasis. Lymphatic filariasis is transmitted by Culex (and some other) mosquitoes. It is mosquito-borne.

3. C

   Sleeping sickness

   (c) Sleeping sickness. African trypanosomiasis is spread by the tsetse fly (Glossina), not by mosquitoes. Among dengue, filariasis, sleeping sickness and malaria, only sleeping sickness is not mosquito-borne. That is the official key.

4. D

   Malaria

   (d) Malaria. Malaria is Plasmodium transmitted by Anopheles mosquitoes. It is mosquito-borne.

Summary. Official key is (c) Sleeping sickness. The four names are classic vector-disease twins. Dengue (Aedes), filariasis (Culex) and malaria (Anopheles) are mosquito-borne. Sleeping sickness is tsetse-borne Trypanosoma brucei in sub-Saharan Africa. Indian kala-azar is sandfly-borne and is another non-mosquito neighbour, not on this list.