Parasite defense mechanisms in bees: behavior, immunity, antimicrobials, and symbionts

Abstract

Parasites are linked to the decline of some bee populations; thus, understanding defense mechanisms has important implications for bee health. Recent advances have improved our understanding of factors mediating bee health ranging from molecular to landscape scales, but often as disparate literatures. Here, we bring together these fields and summarize our current understanding of bee defense mechanisms including immunity, immunization, and transgenerational immune priming in social and solitary species. Additionally, the characterization of microbial diversity and function in some bee taxa has shed light on the importance of microbes for bee health, but we lack information that links microbial communities to parasite infection in most bee species. Studies are beginning to identify how bee defense mechanisms are affected by stressors such as poor-quality diets and pesticides, but further research on this topic is needed. We discuss how integrating research on host traits, microbial partners, and nutrition, as well as improving our knowledge base on wild and semi-social bees, will help inform future research, conservation efforts, and management.

Symbiont-mediated immune priming in animals through an evolutionary lens

“…This priming is sometimes specific, where exposure to a particular parasite species only protects against lethal doses of the same parasite [34], though the evolution of specificity can depend on the parasite species [33]. In some cases, this protection is transgenerational, such that offspring of exposed mothers exhibit increased immune activities and/or survival from infection [21,103,104]. Similarly, vaccines, which are composed of specific parasite components, help the immune system recognize and remember a particular parasite so that it can prevent future infections.…”

“…Bees are an attractive model for studying host-microbe interactions due to their relatively complex microbiome compared to other insects, in addition to their agricultural importance [43]. Consequently, much research on the protective effects of symbionts and other host defence mechanisms has been focused on bees (Table 1) [21]. For vertebrates, research using mice has shed light on the effects of gut microbiome and probiotics on expression of the innate and adaptive immune systems [44][45][46].…”

“…While research on SMIP has focused on foundational processes in symbiosis as well as on applications in agriculture and animal health [12,21], less is known about the evolutionary drivers and consequences of SMIP. Here, we review recent advances made in elucidating the ecological and molecular mechanisms by which symbiont-mediated immune priming occurs and discuss the potential for this phenomenon to drive host, symbiont, and infectious disease evolution (summarized in Fig.…”

Antagonistic Activity against Ascosphaera apis and Functional Properties of Lactobacillus kunkeei Strains

“…The use of intestinal microbial symbionts, such as via dietary supplementation, can improve the health status of bees and increase their productivity, stimulating the immune defenses and exerting an antimicrobial action against unwanted and pathogenic microflora [14][15][16][17][18][19][20]. The presence of lactic acid bacteria (LAB) in the honeybee digestive system has been consistently reported in literature [21], and L. kunkeei is a bacterium frequently present in the intestinal microbiota of honeybees.…”

Antimicrobial Activity against Paenibacillus larvae and Functional Properties of Lactiplantibacillus plantarum Strains: Potential Benefits for Honeybee Health

“…The use of probiotic bacteria, unlike synthetic or natural chemical compounds, does not adversely affect the balance of gut microbiota and honeybee health [24,25]. Moreover, the protection against pathogens and/or parasites is one of the aspects frequently associated with a balanced intestinal flora [26][27][28]. It is well known that the initial phase of pathogen infection can be facilitated by any nutritional or environmental stress causing microbial dysbiosis [29][30][31].…”