Long‐term prevalence of the protists Crithidia bombi and Apicystis bombi and detection of the microsporidium Nosema bombi in invasive bumble bees

Abstract

An initial survey in 2009 carried out at a site in northwestern Patagonia region, Argentina, revealed for the first time in South America the presence of the flagellate Crithidia bombi and the neogregarine Apicystis bombi, two pathogens associated with the Palaearctic invasive bumble bee Bombus terrestris. In order to determine the long-term persistence and dynamics of this microparasite complex, four additional collections at the same site (San Carlos de Bariloche) were conducted along the following seven years. Both protists were detected in all collections: prevalence was 2%-21.6% for C. bombi and 1.2%-14% for A. bombi. In addition, the microsporidium Nosema bombi was recorded for the first time in the country in the last two collections, at prevalences of 12.4% and 2.4% and unusually high infection intensities (Average = 6.56 × 10 spores per individual). Due to the exceptional dispersal ability of the exotic B. terrestris, these three multihost pathogens should be considered as potential threats to South American native bumble bees.

Pathogens Spillover from Honey Bees to Other Arthropods

“…Upon the ingestion of the oocytes by the bee, the sporozoites develop and migrate to the fat body, where they develop, multiply and disrupt the adipose tissue. The infection increases the worker mortality rate and, due to the fat body disruption, both queen survival to hibernation and colony foundation success are impaired [ 84 , 207 , 208 ].…”

“…Likely, the infection occurs via contact on contaminated flowers [ 208 ]. Indeed, A. bombi was found in wild species also, namely A. vaga , A. ventralis , H. truncorum , O. bicornis and O. cornuta [ 37 ].…”

Phoretic mites on South American bumblebees (Bombus spp.) as parasite carriers: a historical input

“…bombi , or (more recently) N . bombi could have been introduced by alien bees and then transferred to native ones (Arbetman et al 2013;Plischuk et al 2017); however, temporarily space incompatible findings have suggested some weaknesses in this hypothesis (Gamboa et al 2015;Nunes-Silva et al 2016). Throughout our contribution, we suggest that these three species were in fact present in the region long before the introduction of B .…”

Impact of Biotic and Abiotic Stressors on Managed and Feral Bees

“…Observing N. bombi spread in a managed colony of B. auricomus , a study isolated the highest pathogen loads in males and lowest pathogen loads in queens and older workers, and concluded that if the described increased male susceptibility to N. bombi substantially reduces the quantity of males available to fertilize queens, this may impact bumble bee colonies [178]. Further confirmation of the global spread of Nosema in bumble bees has been documented in other studies [46,176]. Since the importation of commercially bred bumble bees to South America has been linked with pathogen spillover to native species and their recorded population declines [49], these findings of Nosema spread may be explained by this scenario.…”

“…Similarly, new approaches using molecular biology have been demonstrated for understanding how other honey bee maladies such as Paenibacilius larvae [42] and Nosema microsporidia [43] are vectored, and outlining corresponding appropriate management tactics. More recent literature has explored the spread of bumble bee and solitary bee parasites on a global level [44,45,46,47]. These initial findings have inspired the use of molecular tools to isolate historical time periods correlated with rapid levels of bumble bee parasite infestation [48] and pattern mapping for parasite spread among bee species [49].…”