Validation of Diagnostic Methods for European Foulbrood on Commercial Honey Bee Colonies in the United States

Abstract

One of the most serious bacterial pathogens of Western honey bees ( Apis mellifera Linnaeus [Hymenoptera: Apidae]) is Melissococcus plutonius , the cause of the disease European foulbrood. Because European foulbrood is highly variable, with diverse outcomes at both the individual and colony levels, it is difficult to diagnose through visual inspection alone. Common lab diagnostic techniques include microscopic examination and molecular detection through PCR. In 2009, a lateral flow device was developed and validated for field diagnosis of European foulbrood. At the time, M. plutonius was thought to be genetically homogenous, but we have subsequently learned that this bacterium exists as multiple strains, including some strains that are classified as ‘atypical’ for which the lateral flow device is potentially less effective. These devices are increasingly used in the United States, though they have never been validated using strains from North America. It is essential to validate this device in multiple locations as different strains of M. plutonius circulate in different geographical regions. In this study, we validate the field use of the lateral flow device compared to microscopic examination and qPCR on larval samples from 78 commercial honey bee colonies in the United States with visual signs of infection. In this study, microscopic diagnosis was more sensitive than the lateral flow device (sensitivity = 97.40% and 89.47%, respectively), and we found no false positive results with the lateral flow device. We find high concurrence between the three diagnostic techniques, and all three methods are highly sensitive for diagnosing European foulbrood.

Higher prevalence of sacbrood virus in highbush blueberry pollination units

“…In this study we did not measure prevalence of EFB disease symptoms in colonies, which is distinct from detections of M. plutonius , as testing positive for M. plutonius does not necessarily mean that the colony is symptomatic (Milbrath et al 2021). Additionally, since larval samples were not part of this experiment, we are unable to determine to what extent SBV may or may not contribute to disease manifestation or appearance.…”

“…Like EFB, SBV symptoms are thought to occur most frequently in the spring (Bailey 1969), and like EFB and American foulbrood (AFB), dried SBV-infected larvae can also have a scale-like appearance and larvae may die after cell capping, which can lead to a similar presentation of spotty brood patterns and perforated cell caps (Grabensteiner et al 2001, Milbrath 2021, Milbrath et al 2021). But unlike these two bacterial diseases, SBV can replicate in adult bees and decrease their lifespan (Wang and Mofller 1970, Bailey and Fernando 1972).…”

IPM Strategy to Control EFB in Apis mellifera: Oxytetracycline Treatment Combined with Partial Shook Swarm and Queen Caging

“…In this way, EFB infection might persist in the colony with no or scarce symptoms for years. EFB-infected colonies can also recover spontaneously due to the high variability in the virulence of M. plutonius [ 42 ]. We detected symptomatic EFB 4 months after the PSS in 2 out of 12 beehives in the untreated group and asymptomatic EFB in the OTC-treated group 7 months after the PSS in 2 out of 13 colonies.…”

A high-throughput sequencing survey characterizing European foulbrood disease and Varroosis in honey bees

“…Larval disease in the field is diagnosed by changes to healthy larval or pupal morphology, herein referred to as symptomology. The cause of disease can then be confirmed to differing degrees based on lab or field tests including staining and microscopy, qPCR, next generation sequencing, or lateral flow device 6 , 9 . During the first three days of larval development, adult nurse workers feed larvae a highly nutritious and antimicrobial jelly secreted from special head (hypopharyngeal) glands.…”