Canada-wide surveillance of exotic pathogens: Lotmaria passim and Crithidia mellificae

The presence of high levels of pathogens and/or parasites in honey bee colonies is one of the most prominent factors affecting bee health and contributing to colony losses. Every year, Canadian beekeepers import about 250,000 queens, mainly from the US, as well as package bees from Australia and New Zealand. The importations of foreign queens and bees have the potential to introduce new pathogens into the Canadian honey bee population, such as the recently characterized trypanosomatids Crithidia mellificae and Lotmaria passim.

The aims of this study are to: 1) investigate whether C. mellificae and L. passim are widespread in managed honey bee populations in Canada, as well as the relative abundance of each species; and 2) establish a trypanosomatid cell culture isolated from Canadian honey bees.

A total of 263 colonies were sampled from nine provinces and one territory. Fifty bees per colony were collected in late August, before the application of any disease treatment to the colony. All bees from the same colony were pooled and DNA was extracted from the pooled sample. The prevalence of C. mellificae and L. passim was quantified via real-time PCR using published primers and protocols. Additionally, a third generic primer (‘Universal’ primer) was also used to quantify the presence of all members of the trypanosomatid group. Cell culture was established by using dissected ileum and hindgut from individual bees collected from trypanosomatid-positive colonies. After dissection, samples were incubated in Drosophila medium at room temperature for a week to promote trypanosomatid cells growth.

Our results show that L. passim is more prevalent than C. mellificae in the Canadian honey bee population. Every province sampled had at least one colony infected with L. passim, while only two provinces had colonies infected with C. mellificae. We have successfully isolated L. passim and we currently maintain a healthy culture at Agriculture Agri-food Canada’s Beaverlodge Research Farm. Prior to this survey, the prevalence of these two trypanosomatid species in the Canadian honey bee population was unknown. This first national survey conducted for trypanosomatids sheds light on their prevalence as well as their regional, provincial and national distribution.