Iridovirus and Microsporidian Linked to Honey Bee Colony Decline

Abstract

BackgroundIn 2010 Colony Collapse Disorder (CCD), again devastated honey bee colonies in the USA, indicating that the problem is neither diminishing nor has it been resolved. Many CCD investigations, using sensitive genome-based methods, have found small RNA bee viruses and the microsporidia, Nosema apis and N. ceranae in healthy and collapsing colonies alike with no single pathogen firmly linked to honey bee losses.Methodology/Principal FindingsWe used Mass spectrometry-based proteomics (MSP) to identify and quantify thousands of proteins from healthy and collapsing bee colonies. MSP revealed two unreported RNA viruses in North American honey bees, Varroa destructor-1 virus and Kakugo virus, and identified an invertebrate iridescent virus (IIV) (Iridoviridae) associated with CCD colonies. Prevalence of IIV significantly discriminated among strong, failing, and collapsed colonies. In addition, bees in failing colonies contained not only IIV, but also Nosema. Co-occurrence of these microbes consistently marked CCD in (1) bees from commercial apiaries sampled across the U.S. in 2006–2007, (2) bees sequentially sampled as the disorder progressed in an observation hive colony in 2008, and (3) bees from a recurrence of CCD in Florida in 2009. The pathogen pairing was not observed in samples from colonies with no history of CCD, namely bees from Australia and a large, non-migratory beekeeping business in Montana. Laboratory cage trials with a strain of IIV type 6 and Nosema ceranae confirmed that co-infection with these two pathogens was more lethal to bees than either pathogen alone.Conclusions/SignificanceThese findings implicate co-infection by IIV and Nosema with honey bee colony decline, giving credence to older research pointing to IIV, interacting with Nosema and mites, as probable cause of bee losses in the USA, Europe, and Asia. We next need to characterize the IIV and Nosema that we detected and develop management practices to reduce honey bee losses.

Regulatory Circuitry Governing Fungal Development, Drug Resistance, and Disease

“…This is supported by the recent emergence of C. gattii, a species previously associated with tropical and subtropical climates (296,297), as a primary pathogen of otherwise healthy hosts in northwestern North America (40, 84-86, 191, 352, 594). Other recent examples of changing fungus-host interactions include the sudden extinctions of frog populations caused by the chytrid fungus Batrachochytrium dendrobatidis (49,250,337,567) as well the dramatic collapse of bee colonies associated with the microsporidian Nosema ceranae (73,575). It is likely that such pathogenic fungi sense and respond to their changing environment through many of the same cellular signaling networks discussed in this review.…”

Long term effects of a food supplement HiveAlive™ on honey bee colony strength and Nosema ceranae spore counts

“…As the parasite's development depends on host condition (Porrini et al, 2011) stimulating spring build up of colonies with healthier bees coming out of the winter could be a key factor for increased spring and summer populations with reduced nosema spore loads. Considering that nosema is associated with the presence of different viruses (Bailey & Ball, 1991;Bromenshenk et al, 2010;Toplak, Ciglenečki, Aronstein, & Gregorc, 2013) it is essential to keep the nosema loads low, reducing the probability of virus increase or vice versa. It is quite probable that the positive effect of HiveAlive™ shown during the second year is a result of its long term use (starting in autumn 2012 and finishing in spring 2014).…”

Parasite diversity and coinfection determine pathogen infection success and host fitness

“…Theory predicts that, unlike the many weak interactions that characterize freeliving communities, parasites within a host have a high likelihood of interacting strongly (15,16). Indeed, multipathogen interactions are believed to play an influential role in HIV and malaria in humans, colony collapse disorder in honey bees, and emerging infections in coral reefs (17)(18)(19)(20). Given that many parasites cause limited pathology within their hosts (21), antagonism among coinfecting parasites could represent a novel mechanism of the dilution effect, particularly if less virulent parasites replace or compete with virulent groups at higher diversity (22,23).…”