Molecular survey for the honey bee (Apis mellifera L.) trypanosome parasites Crithidia mellificae and Lotmaria passim in the United States

Authors: WILLIAMS, MARY KATE - University Of Arkansas; Tripodi, Amber; SZALANSKI, ALLEN - University Of Arkansas

Submitted to: Journal of Apicultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Honey bee populations have been fluctuating in recent years. Many factors may be playing a role in honey bee health, but disease is thought to be one of the more important factors at work. Honey bees are susceptible to many diseases, and the pathogenic organisms that cause these are often not well-studied. Trypanosomatids are one such group of insect pathogens with two species that can infect honey bees: Crithidia mellificae and Lotmaria passim. Because these pathogens are indistinguishable with typical microscopy, they have historically been conflated in disease surveys prior to the development of molecular tools to identify trypanosomatid species. We surveyed 1,412 honey bee samples from across eight states and used molecular tools to diagnose the presence of trypanosomatids and identify the species present. This is the first national honey bee trypanosome survey in the United States, and our samples included both managed and wild populations of honey bees. We found that 11% of these bees tested positive for a trypanosomatid and all of the positive cases were L. passim. There were differences among states, with low prevalence in Mississippi (0%) and Utah (0.6%), and high rates in Hawaii (16%) and New York (18%). Additionally, managed honey bees showed higher rates of infection (16%) than wild populations (4%). These results show that L. passim is widespread throughout the United States, and that C. mellificae is much less common. Although L. passim is the dominant trypanosomatid across the US, very little research has been conducted on its effects on honey bee health. The role of L. passim in honey bee losses warrants further investigation.

Technical Abstract: Honey bee populations in the United States have been fluctuating in recent years. Although no one cause has been attributed to this, recent studies have shown that multiple interactions among mircoorganisms may be behind their decline. Several honey bee internal parasites have been overlooked as probable contribution to their decline; these include two different species of trypanosomes Crithidia mellificae and Lotmaria passim. Both parasites have been understudied in honey bee populations and could contribute to population disease dynamics. This study conducted a molecular diagnostic survey for C. mellificae and L. passim using multiplex PCR. Honey bee samples from both feral and managed populations were collected from eight States. This is the first national honey bee trypanosome survey in the United States. A total of 1,412 samples were surveyed during this study. Of the 1,412 samples screened, 11% were positive for L. passim; while no cases of C. mellificae were detected using multiplex PCR analysis. Infection rates of states positive for L. passim ranged from 18% (New York) to 0.60% (Utah). Only one state (Mississippi) was not positive for L. passim. The proportion of positive L. passim samples was significantly different between managed and feral honey bee colonies. Our results reveal that the honey bee parasitic trypanosome L. passim has a widespread distribution in the United States and should be considered as a potential contributor to honey bee health decline.