As we know, honey bees face many pests and diseases that impact colonies, including trypanosomatids. Trypanosomatids are single-celled, flagellated eukaryotic parasites that are found in many different hosts ¹. In honey bees, the most common trypanosomatid is Lotmaria passim. This species colonizes the hindgut of honey bees and can influence physiology, behaviour and survival. 

What is Lotmaria passim?   

Lotmaria passim was first formally described in 2015 after being distinguished from Crithidia mellificae using molecular and morphological evidence ². The parasite exists as flagellated promastigotes, and as a non-mobile round spheroid that adheres to the gut lining in honey bees ². Morphologically, L. passim cells have a lanceolate or tear‑drop shape with a single flagellum ². L. passim colonizes the ileum and rectum of the honey bee hindgut, as both motile and stationary forms ². The stationary forms are spheroids that form single-layered sheets along the gut wall ². 

Arismendi et al. (2022) examined L. passim prevalence across eggs, larvae, pupae, newly emerged bees, nurses and foragers. L. passim was detected in 21–100% of developmental stages except eggs, where it was absent ³. Pupae, nurse bees and foragers showed high prevalence (>92%) of L. passim ³. Young larvae, old larvae and newly emerged bees showed lower prevalence (<71%) compared to foragers ³. Parasite loads ranged from 1.91 × 10¹ to 7.39 × 10⁵ cell equivalents per bee, with foragers carrying the highest loads ³. These findings indicate that L. passim is present in nearly all developmental stages except eggs ³.

Figure 1: Images of isolated cells of Lotmaria passim, wet slides (A), May Grunwald-Giemsa-stained slides (B) and scanning electron microscope (C) (photo:  Rudelli et al. 2023)

The parasite colonizes the ileum and rectum, where its cells can be shed into the gut lumen and passes to other bees through normal social behaviours ². Transmission occurs when bees ingest infected material during trophallaxis, grooming, or while cleaning contaminated brood cells ³. Honey bees frequently exchange food and contact each other during colony tasks, which are behaviours that create efficient routes for parasite movement between individuals ¹. Forager bees can also pick up fecal material on flowers, allowing the parasite to spread outside of the hive. Pollen brought back to the hive has been shown to contain L. passim, suggesting that contaminated floral resources serve as an environmental reservoir for transmission ³. 

Infected bees show reduced survival and increased sucrose responsiveness, indicating energetic stress and altered feeding behaviour ⁴. At the colony level, L. passim infection lowers vitellogenin expression and contributes to precocious foraging, accelerating physiological aging and reducing worker longevity ⁴.

It is important for beekeepers to understand the different diseases honey bees face, including emerging parasites whose full impacts are still being uncovered. Lotmaria passim is a relatively new trypanosomatid described in 2015, and although its long‑term effects on colonies are not yet fully known, it has already been detected across Canada, the United States, South America and Europe ^2,3,4.

 Written by Kaitlyn Newton, ATTTA Seasonal Apiculturist

Connecting with ATTTA Specialists

If you’d like to connect with ATTTA specialists or learn more about our program, you can:

visit our website at https://www.perennia.ca/portfolio-items/honey-bees/

Email attta@perennia.ca

References:

1. Wallace, F., 1966. The Trypanosomatid Parasites of Insects and Arachnids. Experimental Parasitology, 18, p. 124-193. 

2. Schwarz, R.S., Bauchan, G.R., Murphy, C.A., Ravoet, J., de Graaf, D.C. and Evans, J.D., 2015. Characterization of Two Species of Trypanosomatidae from the Honey Bee Apis mellifera: Crithidia mellificae Langridge and McGhee, and Lotmaria passim n. gen., n. sp. Journal of Eukaryotic Microbiology, 62(5), pp.567-583.

3. Arismendi, N., Castro, M.P., Vargas, M., Zapata, C. and Riveros, G., 2022. The trypanosome Lotmaria passim prevails in honey bees of different ages and stages of development. Journal of Apicultural Research, 61(1), pp.63-69.

4. MacInnis, C.I., 2024. How honey bees (Apis mellifera L.) respond to infection with Nosema ceranae and Lotmaria passim.

5. Rudelli, C., Isani, G., Andreani, G., Tedesco, P. and Galuppi, R., 2023. Detection of Lotmaria passim in honeybees from Emilia Romagna (Italy) based on a culture method. Journal of Invertebrate Pathology, 201, p.108007.

Honey bees consistently used comb for storage of food products, supporting brood development and as a structural component within the hive. Honey bees will remove or rebuild wax themselves after many years, but the buildup of residues, such as agrochemicals, and pathogens, can all occur within the wax after only a few years of use. Regular comb rotation every four to five years helps improve honey bee health by limiting exposure to contaminants found within wax as it ages.

Comb Rotation

Comb rotation is the regular replacement of older comb with new foundation or freshly drawn comb. Over time, comb becomes darker, heavier and more contaminated. The older the comb is, the more it will undergo structural changes that reduce cell volume and produce smaller workers with shorter lifespans ¹. Replacing comb helps maintain cleaner wax and supports healthier colony development.

Dark comb is a visual indicator of age, so beekeepers should identify the darkest, oldest frames and replace them with new frames and foundation. Marking the date, year of placement, on the top bars of the frames can help beekeepers track the age of frames. By removing old comb and allowing bees to draw fresh wax, beekeepers can also reduce buildup of contaminants that accumulate over time.

Figure 1: Dark, old frames near the brood nest (ATTTA ©, 2026)

Early in the spring is the ideal time for comb rotation because colonies are expanding and brood nests are being built. Feeding 1:1 sugar water syrup to honey bees can also stimulate wax production during that time of year. This timing allows for the replacement of old comb without disrupting brood patterns. 

Beekeepers can gradually replace frames by removing one or two frames per season from the edge of the colony or by replacing darkest frames first and then replacing them with new foundation. Frames should be slowly rotated to the outside position which would be the 1^st and 10^th frames on standard Langstroth equipment. Removing the outside frames will ensure the brood nest is not disrupted and only the outside frames can be culled. When removing frames, beekeepers should aim to remove 20% of the comb, or 2 frames per a standard 10-frame Langstroth hive box every season. 

Figure 2: Honey bees on a frame with new wax

Comb rotation is a preventive, integrated pest management, practice that supports colony health by reducing disease, chemical residues, and structural constraints related to aged comb. Removing frames is a physical control used to eradicate the disease American foulbrood and Vairimorpha (formerly Nosema) ².

Cultural controls are also a good management practice that beekeepers can use to minimize the risk of disease, like disinfecting comb by fumigation or irradiation can be used for treating comb infected by Vairimorpha spores ². Details on fumigation and irradiation will be discussed further in another blog post in the future.

By replacing older frames each spring and maintaining a 4–5 year turnover cycle, beekeepers can promote cleaner wax, healthier brood development and more resilient colonies. For additional information on Comb Rotation, refer to the Atlantic Tech Transfer Team for Apiculture Comb Rotation Factsheet. 

 Written by Kaitlyn Newton, ATTTA Seasonal Apiculturist

Connecting with ATTTA Specialists

If you’d like to connect with ATTTA specialists or learn more about our program, you can:

visit our website at https://www.perennia.ca/portfolio-items/honey-bees/

Email attta@perennia.ca

References:

1.       Meng, Q., Huang, R., Yang, S., Jiang, W., Tian, Y. and Dong, K., 2025. An Overview of the Adverse Impacts of Old Combs on Honeybee Colonies and Recommended Beekeeping Management Strategies. Insects, 16(4), p.351.

2.       Pernal, S. F. and Clay, H., 2013. Honey bee diseases and pest 3^rd edition. Canadian Association Professional Apiculturist, Beaverlodge, AB, Canada 68 pp.