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.