Mosquitoes provide a transmission route between possums and humans for Buruli ulcer in southeastern Australia.

Buruli ulcer, a chronic subcutaneous infection caused by Mycobacterium ulcerans, is increasing in prevalence in southeastern Australia. Possums are a local wildlife reservoir for M. ulcerans and, although mosquitoes have been implicated in transmission, it remains unclear how humans acquire infection. We conducted extensive field survey analyses of M. ulcerans prevalence among mosquitoes in the Mornington Peninsula region of southeastern Australia. PCR screening of trapped mosquitoes revealed a significant association between M. ulcerans and Aedes notoscriptus. Spatial scanning statistics revealed overlap between clusters of M. ulcerans-positive Ae. notoscriptus, M. ulcerans-positive possum excreta and Buruli ulcer cases, and metabarcoding analyses showed individual mosquitoes had fed on humans and possums. Bacterial genomic analysis confirmed shared single-nucleotide-polymorphism profiles for M. ulcerans detected in mosquitoes, possum excreta and humans. These findings indicate Ae. notoscriptus probably transmit M. ulcerans in southeastern Australia and highlight mosquito control as a Buruli ulcer prevention measure.

Electron microscope detection of tubular aggregates in the mosquito cell line C6/36 treated with Culex australicus (mosquito) homogenate.

'Tubular aggregates' are morphologically distinct cytoplasmic structures that have been linked to a variety of pathological conditions. This report documents the presence of tubular aggregates in an insect cell line (C6/36 cells derived from Aedes albopictus) following inoculation of the cells with material derived from cell culture passaged homogenized Culex australicus mosquitoes. The tubular aggregates were detected in ∼2% of treated cells and had three morphological forms that were termed primary, secondary and tertiary, with progressively greater levels of structural complexity. The findings indicate that tubular aggregates can be induced in an insect cell culture system by an unidentified agent present in some mosquitoes.