Mosquitoes more likely to bite people with lipoatrophy?

Swiss researchers have found that lipoatrophy (fat loss), a common side effect seen in people taking anti-HIV drugs, increases the chances of being bitten by mosquitoes.

Doctors at the University Hospital, Lausanne, recruited a cohort of 122 HIV-positive patients receiving treatments and gathered data over a four week period during the summer of1999 to establish if the frequency of mosquito bites was associated not only with HIV, but also other factors factors such as CD4 count, viral load, the type of retrovirals received and treatment associated side- effects.

Almost two thirds of patients (74 per cent) reported at least one mosquito bite in the three months before enrolment in the study, and 28 patients (almost 30 per cent) said that they believed that they were more likely to be bitten by mosquitoes than people in their immediate environment. Ten patients reported a greater frequency of mosquito bites since being diagnosed HIV-positive and 12 stated that they thought they were receiving more bites since they started treatment with antiretrovirals.

During the study period in July and August, researchers noted mosquito bites in 18 patients (14.8 per cent). When the data were analysed in detail for variables such as age, sex, CD4 count, viral load, and mode of HIV transmission, an independent association was found between lipoatrophy and the chances of being bitten by a mosquito in the three months before the study and during the four weeks of the investigation.

However, no specific anti-HIV drugs were particularly associated with the likelihood of being bitten. The Swiss researchers believe that the loss of subcutaneous fat seen in patients with lipoatrophy makes the network of capillaries (small veins), under the skin more accessible to mosquitoes and that the loss of fat also increases the chances of an inflamed bite or swelling becoming visible.

The study did not include an HIV-negative control group, so it is unclear whether the summer of 1999 was considered the same as usual for mosquito bites in Switzerland and whether HIV-negative people with lower than average body fat were similarly vulnerable to mosquito bites.

It is not yet known if the increased susceptibility of HIV-positive people with lipoatrophy to insect bites will increase their chances of developing potentially dangerous infections spread by mosquitoes, particularly the Leishmania and Plasmodium groups of parasites. As blood-sucking insects cannot spread HIV, there are no implications of this research for HIV transmission.