Lauren Wright of Green Island School asks :-

How many insects carry diseases?

Leo Celi, a specialist in Infectious Diseases and Intensive Care at Dunedin Hospital, responded.

Insects play a significant role in the transmission of a number of infectious diseases. They either carry viruses or they support a stage in the life cycle of parasites. In this role, insects are referred to as vectors. Ticks transmit Lyme disease, ehrlichiosis and babesiosis; flies transmit African sleeping sickness; bugs transmit Chagas disease; lice and mites transmit rickettsial infection, amongst others. None of these occur in New Zealand and, of all the vectors, mosquitoes are the most important.

There are different types of mosquitoes that carry different diseases and each type is limited in terms of where they live in the world. This is the reason why we see certain infections, such as malaria for example, only in specific areas of certain countries.

Six hundred million people get infected and three million people die each year of malaria. It is caused by a parasite called Plasmodium that requires both mosquitoes and humans to complete their life cycle. The female Anopheles mosquito is the vector for malaria; hence there is no malaria in countries where there are no Anopheles mosquitoes like New Zealand.

Someone visiting a place where malaria exists will need to take antibiotics in order to prevent the infection in case an infected mosquito bites him or her. There are also ways to minimise being bitten by these mosquitoes, such as avoiding being outdoors at night since these mosquitoes feed mostly at night, avoiding use of perfumes and brightly coloured clothes that attract the mosquitoes, and wearing long-sleeved shirts and long pants to minimise exposed skin. Other diseases caused by mosquito bites include dengue fever, and a number of brain infections such as West Nile encephalitis and those caused by a family of viruses known as arboviruses.