Joanne Carey, of Port Chalmers School, asks :-

Do moths spread germs?

John Smith, a Microbiologist at the University of Otago, responded.

As far as humans are concerned, moths are not regarded as significant vectors (spreaders) of germs such as bacteria, viruses and fungi. However, any animal can spread germs passively. By this we mean that if a moth stands on or walks across material contaminated with germs (e.g. raw sewage), some of these will adhere to the feet and may be deposited (and grow) on the next thing the moth lands on. In the same way, bacteria which occur on our hands may contaminate coins and be passed on to the next person who handles the coins. In each case, the germs do not multiply on the vector (moth, coins) which simply serves as a transmitter of the germs. This is one of the main reasons why we should always wash our hands before eating food.

Some microbes do, however, actively grown in and parasitise moths; fungi are important examples. As a general rule these germs are harmless to us as they cannot grow at the body temperature (37C) normally occurring in humans. They may, however, be capable of parasitising plants.

In contrast to moths, some insects (e.g. mosquitoes, ticks) are well known as vectors of some important human diseases, e.g. malaria. In these cases, the germs usually have an active growth phase in the insect vector; that is, the germs multiply to high levels in the insect and large numbers (of germs) are then passed on to the next person bitten by the insect.