Host sharing by the honey bee parasitesLotmaria passimandNosema ceranae.
The trypanosomeLotmaria passimand the microsporidianNosema ceranaeare common parasites of the honey bee,Apis mellifera, intestine, but the nature of interactions between them is unknown. Here, we took advantage of naturally occurring infections and quantified infection loads of individual workers (N= 408) originating from three apiaries (four colonies per apiary) using PCR to test for interactions between these two parasites. For that purpose, we measured the frequency of single and double infections, estimated the parasite loads of single and double infections, and determined the type of correlation between both parasites in double infections. If interactions between both parasites are strong and antagonistic, single infections should be more frequent than double infections, double infections will have lower parasite loads than single infections, and double infections will present a negative correlation. Overall, a total of 88 workers were infected withN. ceranae, 53 withL. passim, and eight with both parasites. Although both parasites were found in all three apiaries, there were significant differences among apiaries in the proportions of infected bees. The data show no significant differences between the expected and observed frequencies of single- and double-infected bees. While the infection loads of individual bees were significantly higher forL. passimcompared toN. ceranae, there were no significant differences in infection loads between single- and double-infected hosts for both parasites. These results suggest no strong interactions between the two parasites in honey bees, possibly due to spatial separation in the host. The significant positive correlation betweenL. passimandN. ceranaeinfection loads in double-infected hosts therefore most likely results from differences among individual hosts rather than cooperation between parasites. Even if hosts are infected by multiple parasites, this does not necessarily imply that there are any significant interactions between them.
Institute of Bee Health Vetsuisse Faculty University of Bern Bern Switzerland.
Manuel
M
Tritschler
Institute of Bee Health Vetsuisse Faculty University of Bern Bern Switzerland.
Gina
G
Retschnig
Institute of Bee Health Vetsuisse Faculty University of Bern Bern Switzerland.
Orlando
O
Yañez
Institute of Bee Health Vetsuisse Faculty University of Bern Bern Switzerland; Agroscope Swiss Bee Research Centre Bern Switzerland; Department of Entomology and Plant Pathology Auburn University Auburn AL USA.
Geoffrey R
GR
Williams
Institute of Bee Health Vetsuisse Faculty University of Bern Bern Switzerland; Agroscope Swiss Bee Research Centre Bern Switzerland.
Peter
0000-0001-5163-5215
P
Neumann
Lotmaria passim; Nosema ceranae; competition; interaction