Nosemosis, a disease caused by a microsporidian infection, is one of the most frequently observed parasitic pathologies affecting adult honeybees. Presently, Nosema ceranae seems to be the main microsporidian infection in Apis mellifera. The antibiotic fumagillin is the only compound available to treat Nosema diseases; however, it is no longer licensed in most EU member states; therefore, the need to identify new molecules/substances prevails. The intent of this paper is to test bacterial metabolites by Bacillus and Enterococcus strains, isolated from bee midgut and honey. The toxicity on bees and the antiparasitic activity on N. ceranae were assessed under laboratory conditions. Results did not yield toxicity for the administered surfactin or bacteriocin concentrations. Spores exposed to direct contact with a particular surfactin revealed a significant infectivity reduction when inoculated on bees. This surfactin, administered ad libitum from the individuals' emergence, led to a significant reduction in parasitosis development when bees were infected with untreated spores 7 days postemergence. Based on the results obtained, one of the surfactins is herein postulated as a molecule capable of reducing N. ceranae development, acting either by direct exposure to purified spores or incorporated into the digestive tract of the bee.

To investigate the effect of nutritional condition of the honey bee Apis mellifera on the development of the microsporidian parasite Nosema ceranae under laboratory conditions, newly emerged bees were confined and fed on three ad libitum diets: high fructose corn syrup (HFCS) + fresh bee bread; HFCS + a commercial mixture of amino acid and vitamin, and HFCS. On day 7 post-emergence, bees from each diet treatment were individually infected with 4.60 x 10 4 , 2.30 x 10 5 or 1.15 x 10 6 spores of N. ceranae, keeping later on the same diet. On days 3, 6, 9, and 12, post-infection bee midguts were removed to individually quantify the spores developed. The results indicate that this parasite multiplies successfully regardless of the inoculum given or the nutritional status of its host. When bees are fed on pollen, however, the parasite develops quickly, exhibiting significantly higher intensities than under other treatments. The longevity of infected bees fed on the same diet was not affected by the degree of parasitism, but by the quality of the ad libitum diet administered. The data demonstrate a parasite development that depends on host-condition. This should be considered when designing experiments to evaluate the development and virulence of this pathogen. Desarrollo de Nosema ceranae en Apis mellifera: influencia de la dieta y el inoculado infectivo Resumen Para estudiar el efecto de la condición nutricional de obreras de Apis mellifera sobre el desarrollo de Nosema ceranae, se confinaron abejas recién emergidas y se sometieron a alimentación ad libitum con tres dietas diferentes: jarabe de alta fructosa (HFCS) + polen fresco ensilado; HFCS + mezcla comercial de aminoácidos y vitaminas, y una tercera de HFCS. Siete días luego de la emergencia, cada tratamiento nutricio fue subdividido en tres grupos y sus individuos fueron individualmente infectados con 4.60 x 10 4 , 2.30 x 10 5 o 1.15 x 10 6 esporos de N. ceranae, manteniéndose luego la dieta previa a la infección. A los 3, 6, 9 y 12 días posteriores a la infección se sacrificaron abejas para obtener el ventrículo y cuantificar individualmente el número de esporos presentes. Los resultados demuestran que este parásito se multiplica exitosamente, independientemente del inóculo administrado y del estado nutricional de su hospedador. De todos modos, cuando las obreras son alimentadas con polen fresco, la infección se desarrolla rápidamente, mostrando intensidades significativamente mayores a las desarrolladas bajo otros tratamientos. La longevidad de los individuos infectados y alimentados con la misma dieta no fue afectada del grado de parasitismo desarrollado, sino por la calidad de la dieta administrada. Los datos nos muestran un desarrollo del parásito que es dependiente de la condición del hospedador, y por lo tanto, deberían ser considerados cuando se diseñan experimentos para evaluar el desarrollo y la virulencia de este patógeno.

Using molecular techniques, we documented the presence of Nosema ceranae in honeybees (Apis mellífera) from Argentina. Samples were collected from A. mellifera colonies in 38 districts of Buenos Aires province, Argentina. Molecular characterization was achieved with a multiplex PCR-based method, which allows parallel diagnosis of N. ceranae and N. osema apis. N. ceranae was identified in all the samples analyzed. Moreover, coinfections with N. apis were detected in Balcarce and Maipú districts. We identified three rRNA sequence variants of N. ceranae, which may represent diverse sources of bee importation. The results suggest that N. ceranae is widely distributed in Argentina and that the genetic variation observed between the different isolates could be related with the difference in the symptomatology found previously by our work group. Our results highlight the need to re-assess the health protocols currently in force so that they recognize N. ceranae as the main causal agent of Nosemosis in this country.

No abstract