Itching bites may limit Ross River virus infection

To the Editor: Dugdale proposed recently in the Journal that people who have a skin reaction to mosquito bites are less likely to be infected by Ross River virus than those who do not.1 As he quotes Kumar, who made a similar comment about malaria infection,2 one could presumably extend his idea to other conditions transmitted by mosquitoes. This accords with my own personal experience of dengue fever acquired in Fiji.

While serving there, I had two separate proven infections with dengue virus. As I react very little to mosquito bites, I could not identify the time of infection. Indeed, on the first occasion, I had just returned from a three-month stay in Adelaide and could not recall being bitten by a mosquito at all. In contrast, my wife, who developed large weals whenever bitten, went through at least three epidemics of dengue without being infected.

My advice to travellers who consult me is that there is an advantage to reacting badly to mosquitoes, as one is then more likely to take anti-mosquito precautions, whereas the non-reactor is more likely to disregard them. However, Dugdale's suggestion that a local inflammatory reaction may be a factor in defence against infection is intriguing and worth following up. It should be simple to enquire retrospectively about reactions to mosquito bites in those who have had a mosquito-borne disease, as Dugdale has done for Ross River virus infection. This would provide evidence on which to base pathological and immunological studies.