What's the Buzz with ATTTA #67

Friday, 1 October 2021

Last week we reviewed some key aspects of fall varroa mite management, with emphasis on making sure we are using treatment products responsibly and when our sampling indicates that treatment is warranted. Continuing on the topic of fall pest and disease management, this week we will explore some recent studies investigating seasonal trends of Nosema with consideration of the shift in Nosema species prevalence. Fall presents an opportune time to perform Nosema sampling and to treat if this indicates the infection level is above the economic threshold.

 

Nosema in Atlantic Canada

In the world of beekeeping and honey bee research, the topic of Nosema has gained increasing attention thanks to the realized shift in prevalence of Nosema species, from Nosema apis towards Nosema ceranae. Last year, ATTTA shared interesting, significant results from our regionally relevant investigation: Evaluating Efficacy of Fumagilin-B® Against Nosemosis and Tracking Seasonal Trends of Nosema spp. in Nova Scotia Honey Bee Colonies (McCallum et al. 2020).

The results of this study (as outlined in Blog #25) revealed a shift in Nosema species infecting honey bee colonies in Atlantic Canada.  It also identified seasonal trends in infection levels and treatment efficacy (McCallum et al. 2020) specific to our region. This research helps build a better comprehension of nosemosis but emphasized a knowledge gap in understanding best management practices for control of Nosema, especially Nosema ceranae.

Lately, new research has added to our understanding of Nosema. Two examples of this type of work are explored below.


Seasonality of Nosema ceranae Infections and Their Relationship with Honey Bee Populations, Food Stores, and Survivorship in a North American Region (Emsen et al.  2020)

To help address the lack of knowledge and understanding of Nosema ceranae, a recent study from Southern Ontario aimed to determine how an infection impacts honey bees in a realistic beekeeping setting, and optimal treatment strategies to control an infection. Contributing to this aim, researchers investigated seasonal changes in the intensity, prevalence, and spore viability of Nosema ceranae infections, and explored how an infection impacts colony conditions and honey bee longevity.

This study revealed interesting, significant results that contribute to our knowledge and understanding surrounding Nosema ceranae and are summarized below:

  • Intensity: higher in spring/summer than fall
  • Prevalence: higher in spring/summer than fall
  • Spore viability: ~4x higher in spring than summer/fall
  • Colony conditions: low level N. ceranae infection (<1,000,000 spores/bee): more bees, brood, pollen stores, and honey stores than high level infection (>2,000,000 spores/bee)
  • Longevity: decreased survivorship rates in infected worker bees

This study also emphasizes the need for additional investigations on the epidemiology and the impact of Nosema ceranae in honey bee colonies in other geographic regions, due to potential regional differences in disease virulence, susceptibility, and therefore overall impact.

Mitigating Nosema ceranae infection in western honey bee (Apis mellifera) workers using propolis collected from honey bee and stingless bee (Tetrigona apicalis) hives (Naree et al. 2021)

Fumagillin has been, and continues to be, the best treatment option for controlling Nosema infections. However, reliance on a single treatment product combined with concerns regarding human exposure to fumagillin, and the shift in prevalence from N. apis to N. ceranae encourages research for finding novel treatments for Nosema.

In this recent study, the efficacy of two kinds of propolis (from honey bee and stingless bee hives) as a treatment for Nosema ceranae infections was investigated. Results revealed in this investigation are interesting and significant.  The main points are outlined below:

  • Increased probability of infected bee survival with either kind of propolis treatment
  • Decreased infection rate and infectivity in bees treated with either kind of propolis
  • Increased protein contents in both hypopharyngeal glands and hemolymph in bees treated with either kind of propolis

Although these are interesting and exciting results, more research is needed to improve understanding of how propolis works to combat Nosema ceranae infections, and how treatment efficacy varies depending on geographic location. 

 

Emsen, B., Mora, A., Lacey, B., Eccles, L., Kelly, P. G., Medina-Flores, C. A., Petukhova, T., Morfin, N., & Guzman-Novoa, E. (2020).  Seasonality of Nosema ceranae Infections and Their Relationship with Honey Bee Populations, Food Stores, and Survivorship in a North American Region, Journal of Veterinary Sciences, full text available online.

McCallum, R., Olmstead, S., Shaw, J., & Glasgow, K. (2020). Evaluating Efficacy of Fumagilin-B® Against Nosemosis and Tracking Seasonal Trends of Nosema spp. in Nova Scotia Honey Bee Colonies, Journal of Apicultural Science, full text available online.

Naree, S., Benbow, M. E., Suwannapong, G., & Ellis, J. (2021). Mitigating Nosema ceranae infection in western honey bee (Apis mellifera) workers using propolis collected from honey bee and stingless bee (Tetrigona apicalis) hives, Journal of Invertebrate Pathology, full text available online.



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