Impact of Varroa destructor and deformed wing virus on emergence, cellular immunity, wing integrity and survivorship of Africanized honey bees in Mexico.

The ectoparasitic mite Varroa destructor is the primary health problem of honey bees (Apis mellifera) worldwide. Africanized honey bees in Brazil have demonstrated tolerance to the mite, but there is controversy about the degree of mite tolerance of Africanized bees in other countries. This study was conducted to quantify the effect of V. destructor parasitism on emergence, hemocyte concentration, wing integrity and longevity of Africanized honey bees in Mexico. Africanized bee brood were artificially infested with V. destructor mites and held in an incubator until emergence as adults and compared to non-infested controls. Deformed wing virus (DWV) presence was determined in the mites used to infest the bees. After emergence, the bees were maintained in an incubator to determine survivorship. The percentage of worker bees that emerged from parasitized cells (69%) was significantly lower than that of bees emerged from non-infested cells (96%). Newly-emerged parasitized bees had a significantly lower concentration of hemocytes in the hemolymph than non-parasitized bees. Additionally, the proportion of bees with deformed wings that emerged from V. destructor-parasitized cells was significantly higher (54%) than that of the control group (0%). The mean survival time of bees that emerged from infested and non-infested cells was 8.5 ±â€¯0.3 and 14.4 ±â€¯0.4 days, respectively, and the difference was significant. We conclude that V. destructor parasitism and DWV infections kill, cause deformities and inhibit cellular immunity in developing Africanized honey bees, and significantly reduce the lifespan of adult bees in Mexico. These results suggest that the tolerance of Africanized bees to V. destructor is related to adult bee mechanisms.

Varroa destructor (Mesostigmata: Varroidae) Parasitism and Climate Differentially Influence the Prevalence, Levels, and Overt Infections of Deformed Wing Virus in Honey Bees (Hymenoptera: Apidae).

The prevalence and loads of deformed wing virus (DWV) between honey bee (Apis mellifera L.) colonies from a tropical and a temperate environment were compared. The interaction between these environments and the mite Varroa destructor in relation to DWV prevalence, levels, and overt infections, was also analyzed. V. destructor rates were determined, and samples of mites, adult bees, brood parasitized with varroa mites and brood not infested by mites were analyzed. DWV was detected in 100% of the mites and its prevalence and loads in honey bees were significantly higher in colonies from the temperate climate than in colonies from the tropical climate. Significant interactions were found between climate and type of sample, with the highest levels of DWV found in varroa-parasitized brood from temperate climate colonies. Additionally, overt infections were observed only in the temperate climate. Varroa parasitism and DWV loads in bees from colonies with overt infections were significantly higher than in bees from colonies with covert infections. These results suggest that interactions between climate, V. destructor, and possibly other factors, may play a significant role in the prevalence and levels of DWV in honey bee colonies, as well as in the development of overt infections. Several hypotheses are discussed to explain these results.

Genotypic variability and relationships between mite infestation levels, mite damage, grooming intensity, and removal of Varroa destructor mites in selected strains of worker honey bees (Apis mellifera L.).

The objective of this study was to demonstrate genotypic variability and analyze the relationships between the infestation levels of the parasitic mite Varroa destructor in honey bee (Apis mellifera) colonies, the rate of damage of fallen mites, and the intensity with which bees of different genotypes groom themselves to remove mites from their bodies. Sets of paired genotypes that are presumably susceptible and resistant to the varroa mite were compared at the colony level for number of mites falling on sticky papers and for proportion of damaged mites. They were also compared at the individual level for intensity of grooming and mite removal success. Bees from the "resistant" colonies had lower mite population rates (up to 15 fold) and higher percentages of damaged mites (up to 9 fold) than bees from the "susceptible" genotypes. At the individual level, bees from the "resistant" genotypes performed significantly more instances of intense grooming (up to 4 fold), and a significantly higher number of mites were dislodged from the bees' bodies by intense grooming than by light grooming (up to 7 fold) in all genotypes. The odds of mite removal were high and significant for all "resistant" genotypes when compared with the "susceptible" genotypes. The results of this study strongly suggest that grooming behavior and the intensity with which bees perform it, is an important component in the resistance of some honey bee genotypes to the growth of varroa mite populations. The implications of these results are discussed.

Colonización, impacto y control de las abejas melíferas africanizadas en México / Colonization, impact and control of Africanized honey bees in Mexico

This review article describes the colonization process and the replacement of European honey bee populations by Africanized bees, as well as the biological characteristics that have given Africanized bees advantages for their colonizing success, and a discussion on their impact, control, and perspectives for the Mexican beekeeping industry, taking into consideration the beekeepers' point of view with regard to their management and culture in comparison with European bees.

En este trabajo recapitulativo se describe el proceso de colonización y reemplazo de las poblaciones de abejas melíferas europeas por africanizadas, así como las características biológicas que han dado ventajas a las abejas africanizadas para su éxito colonizador y una discusión sobre su impacto, control y perspectivas para la apicultura mexicana, abordando el punto de vista de los apicultores respecto a su manejo y explotación en comparación con abejas europeas.

Estudio comparativo de tres pruebas para evaluar el comportamiento higiénico en colonias de abejas (Apis mellifera L.) / Comparative study of three assays to evaluate hygienic behavior in honey bee (Apis mellifera L.) colonies

The discriminatory capacity, cost and practicality of three assays to measure hygienic behavior in 60 honey bee colonies were compared in a first experiment. Capped worker brood of these colonies were killed with an insect pin (P), frozen in a freezer at -18°C (CC) and with liquid nitrogen at -195°C (CN2). The percentage of brood removed by the bees was recorded 24 h after being killed. Since the P assay showed a low discriminatory capacity, an additional experiment with 50 colonies was performed, reducing the evaluation time to 8 h and verifying the influence of body fluids and odors released by the pin-killed brood. Colonies were significantly more hygienic (P < 0.01) with the P assay (88%) than with the CC (69%) and CN2 (65%) assays. There were significant correlations among assays (r > 0.54, P < 0.01) and between replicates within assays (r > 0.37, P < 0.01). Variation among colonies was greater with the CN2 and CC assays than with the P assay. The P assay was the least expensive and easiest to apply (6.59 pesos, 0.58 dollars per colony), but showed the lowest discriminatory capacity, that could not be enhanced even though the time of evaluation was reduced. This could have been caused by the strong stimulus from odors and haemolymph released from the pinkilled brood. The CN2 and the CC assays showed a high discriminatory capacity, but the former was more expensive (14.80 pesos, 1.31 dollars) and the least practical. The CC assay was the second least expensive (10.15 pesos, 0.90 dollars) and practical. The application of either freeze assays is recommended for screening hygienic behavior in honey bees because of their reliability.

Se comparó la capacidad discriminatoria, costo y facilidad de aplicación de tres pruebas para medir el comportamiento higiénico en 60 colonias de abejas melíferas en un primer experimento. Las crías operculadas de estas colonias fueron sacrificadas al puncionarlas con un alfiler entomológico (P), y congelarlas en congelador a -18°C (CC) con nitrógeno líquido a -195° C (CN2). Se determinó el porcentaje de crías removidas por las abejas 24 h después de que fueron sacrificadas. Como consecuencia de la poca discriminación entre colonias inicialmente encontrada con la prueba P, se realizó un experimento adicional con 50 colonias, reduciendo el tiempo de lectura a 8 h y se verificó el efecto producido por la emanación de olores y fluidos de las crías sacrificadas. Las colonias fueron significativamente más higiénicas (P < 0.01) con la prueba P (88%), en comparación con la de CC (69%) y CN2 (65%). Se encontraron correlaciones significativas entre pruebas (r > 0.54, P < 0.01) y entre repeticiones dentro de pruebas (r > 0.37, P < 0.01). La variación entre colonias fue mayor con las pruebas CN2 y CC que con la P. La prueba P fue la más económica y práctica de aplicar (6.59 pesos, 0.58 dólares, por colonia), pero mostró menor capacidad discriminatoria, que no se incrementó aun cuando se redujo el tiempo de lectura. Este resultado pudo deberse al fuerte estímulo provocado por olores y hemolinfa emanados de las crías sacrificadas. Las pruebas CN2 y CC mostraron alta capacidad discriminatoria, pero la primera fue más cara (14.80 pesos, 1.31 dólares) y la menos práctica. La prueba CC fue la segunda más económica (10.15 pesos, 0.90 dólares) y práctica. Se recomienda aplicar cualquiera de las pruebas de congelación para medir el comportamiento higiénico de colonias de abejas melíferas por su confiabilidad.