Lotmaria passim currently appears to be the predominant trypanosome in honey bees worldwide. Although, the specific effects of L. passim by single or mixed with other gut parasites such as Nosema ceranae on honey bees’ health is still unclear. We consequently measured bees’ survival, parasite loads, the expression of antimicrobial peptides (AMPs) and vitellogenin gene. Thus, (1) bees naturally infected with L. passim, (2) healthy bees inoculated with Nosema ceranae, (3) bees naturally infected with L. passim and inoculated with N. ceranae and (4) healthy bees (control) were maintained under controlled conditions. Honey bees infected with N. ceranae or with mixed infections of L. passim and N. ceranae had significantly lower survival rates than the control group at 20 days post-inoculation (dpi). A competitive suppression was also detected, provided that the L. passim load was significantly affected by the presence of N. ceranae at 15 dpi. Expressions of the AMPs defensin and hymenoptaecin rapidly (two hours post-inoculation) increased in bees infected with N. ceranae and mixed infections. However, this effect was not continuous. In fact, expressions of abaecin, defensin, hymenoptaecin and vitellogenin decreased drastically at 15 dpi in bees with both single and mixed infections. The decrease in the expression of AMPs and vitellogenin throughout this period was consistent with the reduced survivals observed in this study, indicating that mixed infections of L. passim and N. ceranae, and even into a scenario of competition between them, may have a synergic effect on the survival and immune-related gene expressions (biomarkers) of worker bees.

Deformed wing virus (DWV) is one of the most common viruses in apiaries worldwide, and its presence in Chilean apiaries is no exception. There are three well-defined master variants described as DWV-A, DWV-B (or VDV-1) and DWV-C. We studied the prevalence, load and recombinant genotypes among DWV variants in honey bees from Chilean apiaries. We also compared the viral load in each region in colonies that were treated or untreated against Varroa destructor. Using real-time PCR with specific primers enabled us to determine that DWV-A was the most prevalent (71%) throughout Chile, with a higher level than DWV-B (circa 3% prevalence), and almost 60-times more load, especially in northern Chile. The viral load was lower only in treated colonies located in the Metropolitana, Biobío/Ñuble and Los Ríos regions. The DWV-C genotype and recombinants were not detected. This suggests that viral recombinant events are limited since DWV-B is still uncommon in honey bee hives at present. This is the first study involving DWV-B in Chile.

Insects have a highly sensitive sense of smell, allowing them to perform complex behaviors, such as foraging and peer recognition. Their sense of smell is based on the recognition of ligands and is mainly coordinated by odorant-binding proteins (OBPs). In Apis mellifera, behavior can be affected by different pathogens, including deformed wing virus (DWV) and its variants. In particular, it has been shown that variant A of DWV (DWV-A) is capable of altering the ultra-cellular structure associated with olfactory activity. In this study was evaluated olfactory sensitivity and the expression of OBP genes in honey bees inoculated with DWV-A. Electroantennographic analyses (EAG) were carried out to determine the olfactory sensitivity to the essential oils Eucalyptus globulus and Mentha piperita. The expression of nine antenna-specific OBP genes and DWV-A load in inoculated bees was also quantified by qPCR. We observed an inverse relationship between viral load and olfactory sensitivity and the expression of some OBP proteins. Thus, high viral loads reduced olfactory sensitivity to essential oils and the gene expression of the OBP2, OBP5, OBP11, and OBP12 proteins on the antennas of middle- and forager-age bees. These results suggest that DWV-A could have negative effects on the processes of aroma perception by worker bees, affecting their performance in tasks carried out in and outside the colony.

The gut parasite Lotmaria passim has recently been identified in Apis mellifera and appears to be the predominant trypanosome in honey bees worldwide, but there is little information about L. passim in honey bees of different ages and stages of development. We evaluated the prevalence and load of L. passim in eggs, young and old larvae, dark pupae, newly emerged, nurse and forager bees from colonies that were L. passim-positive. The use of real-time PCR enabled us to detect L. passim, ranging from 21 to 100% in honey bees of almost all stages and ages, with loads ranging from 1.91 x 10¹ to 7.39 x 10⁵ cells equivalent per bee. This is the first study that reports L. passim in honey bees of different ages and stages of development. We also found an absence of L. passim in eggs, which discards a possible transovarial transmission of this pathogen, although further validations are required. Our findings provide new perspectives for studies on the epidemiology of L. passim in honey bees and other insect pollinators.

Insect behavior is coordinated mainly by smell through the diverse odor-binding proteins (OBP) that allow them to identify and recognize their environment. Sensory information collected through smell is then analyzed and interpreted in the brain, allowing for correct insect functioning. The behavior of honeybees (Apis mellifera L.) can be affected by different pathogens, such as deformed wing virus (DWV). In particular, the DWV variant A (DWV-A) is capable of altering olfactory sensitivity and reducing the gene expression of different OBPs, including those associated with nursing behavior. The DWV is also capable of replicating itself in the sensory lobes of the brain, further compromising the processing of sensory information. This study evaluated the behavioral response of nurse honeybees exposed to a pheromone compound and the alterations in the gene expression of the pre- and post-synaptic neuronal genes neuroxins-1 and neurogilin-1 in the bee heads and OBP proteins in the antennae of nurse bees inoculated with DWV-A. The behavioral response of nurse bees exposed to the larval pheromone compound benzyl alcohol was analyzed using a Y-tube olfactometer. The viral load, the gene expression of OBP5 and OBP11 in antennae, and neuroxins-1 and neurogilin-1 in the bee heads were analyzed via qPCR. High viral loads significantly reduced the ability of 10- and 15-day-old nurse honeybees to choose the correct pheromone compound. Also, the gene expression of OBP5, OBP11, neuroxin-1, and neurogilin-1 in nurse honeybees decreased when they were highly infected with DWV-A. These results suggest that a DWV-A infection can disturb information processing and cause nursing honeybees to reduce their activity inside the hive, altering internal cohesion.

The 2,4-Diacetylphloroglucinol (2,4-DAPG) and phenazine (PCA)-producing Pseudomonas inhibit wheat pathogens’ development, but the relationship between communities of pathogens and genotypes of these bacteria has been little studied. Relationships between wheat crown fungi associated with the presence of 2,4-DAPG and PCA-producing pseudomonads were evaluated in four commercial wheat crops located in the La Araucanía and Los Lagos Regions of Chile, during two crops seasons. Portions of the base of the first internode of the culm collected during the grain-filling stage were cultured in an artificial medium for fungal isolation, while roots of the same wheat plants and from plants collected previous harvest, and also used to assess yield and plant height, were used for the detection of 2,4-DAPG and PCA-producing Pseudomonas spp. using PCR with specific primers. Genera Phaeosphaeria, Fusarium, Rhizoctonia, and Microdochium were repeatedly isolated (52.6%, 22.1%, 7.8%, and 4.9%, respectively) and the genetic composition of 2,4-DAPG and PCA-producing Pseudomonas spp. varied between fields and sampling periods. Genetic groups A, B, D, K, L, and P associated with the phlD gene were detected. The presence of 2,4-DAPG-producing bacteria benefited crop health, relating their existence with increasing yield and plant height, and the reduction in the incidence and severity of disease caused by pathogenic microorganisms on the first internode of wheat culms.