Pulsed light inactivation of the bumble bee trypanosome parasite Crithidia bombi

The anthropogenic movement of managed bees has led to the introduction and global spread of parasites with significant adverse effects on the health of both managed and wild species. This constitutes the first study to report on the use of high-intensity pulsed light (PL) for the inactivation of the trypanosome parasite Crithidia bombi, a pest of wild and managed bees. Through initial PL range-finding studies we identified a putative effective UV dose of 12.96 mu J/cm(2) for C. bombi treatment. This was a result of tests on waterborne protozoan Cryptosporidium parvum, and was determined using in vitro combined cell culture-qPCR infectivity assays. This irradiance produced ca. >= 4 log(10) oocyst reductions of C. parvum. To confirm this dose as appropriate for treatment of C. bombi, we used the buff tailed bumble bee (Bombus terrestris) as an animal infectivity model. C. bombi was collected from the feces of wild B. terrestris queens and used to inoculate 30 commercially supplied workers (B. terrestris audux) in order to obtain a colony-specific C. bombi inoculum. This was used for subsequent tests on 60 randomly-selected unparasitised workers, which were divided evenly and fed either PL-treated or untreated (control) C. bombi inoculant. Of the 28 surviving workers fed with pooled C. bombi untreated inoculum, 25 exhibited infection as confirmed by detection of the parasite in fecal samples after 9 days, where the remaining two did not excrete feces. Twenty-eight of 30 (93%) workers fed PL-treated C. bombi at 12.96 mu J/cm(2) under similar test conditions were uninfected after the same time period (the remaining two workers did not produce feces for testing). Thus we demonstrate for the first time, that PL is potentially a reliable and efficient technology for the non-thermal inactivation of C. bombi for the pollination industry. Although in vivo treatment of whole bees with PL is not possible, the use of this technology on equipment used in commercial bumble bee breeding facilities could potentially reduce infection rates, therefore contributing to making the industry more sustainable and less of a risk to wild pollinators.