Mite bites and biological pest control using birds in urban areas

Tits are among the biocontrol agents that are being promoted in urban areas through the installation of nestboxes. This practice aims notably to limit the proliferation of the pine processionary caterpillar, which poses a significant health and veterinary risk. As with many birds, tit nests can harbor blood-sucking mites. These mites are capable of traveling tens of meters in a few hours, and cases of human bites in homes with bird nests are regularly reported around the world. Given that knowledge about their vector role is very limited and that the distribution of zoonotic pathogens found in birds is changing as a result of global changes, studying the risk of human bites by these mites could help anticipate new epidemics. Human bites are generally associated with Dermanyssus gallinae L1, a cryptic species within the gallinae complex of genus Dermanyssus, associated with pigeons, and Ornithonyssus bursa, a largely generalist species found on various urban birds. Could increasing the presence of tits in urban areas contribute to the spread of these species and increase the risk of human bites? To obtain initial answers to this question, we compared the blood-feeding acarofauna of tit (Great and Blue Tits), pigeon and other birds’nests collected in and around Montpellier. To do so, nest material was collected shortly after the young had fledged (peak infestation) between spring 2024 and fall 2025. Then, dermanyssoid mites were isolated and identified using a morpho-molecular approach. The results of this pilot study show that the prevalence of species commonly found in human cases is very low in tit nestboxes in the Montpellier region. Dermanyssus gallinae L1 was found with a high prevalence in pigeon nests and only in these nests. While Ornithonyssus bursa was detected from all of the urban bird species under scrutiny, it was found in only one of the 156 tit nests studied. Apart from this anecdotal case, the blood-feeding mites isolated from tit nests in this study belonged either to D. carpathicus, a species typically found in tit nests, or to a previously unreported variant of the gallinae complex, whose status as a species or intraspecific variant remains to be established. Further experiments are needed to state whether their absence from reports in humans is due to the lack of opportunity due to isolation in the nestboxes, or because of host-mite incompatibility. However, the risk associated with installing tit nestboxes in cities is probably very low.