Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Transmission routes of Nosema elucidated

A number of experiments and observations have been undertaken by several partners of the Pollinator Parasites project that address, directly or tangentially, the issue of how N. bombi is transmitted between hosts. This information is central to a full understanding of the biology of the microsporidium and how to control it. The relevant data are summarised in bullet form, under two headings of the main routes by which parasites are transmitted, with additional details of scientist and how the data will be more widely disseminated.

Evidence concerning vertical transmission (VT):
- (P2, Sandra Mustafa) (Evidence for VT) Overwintered queens often have ovaries that are infected with microsporidia (MSc. Thesis, manuscript in preparation).

- (P2, Julia Klee and P4, Oliver Otti) (Evidence for VT) Ovaries of infected queens commonly contain microsporidia, as visualised by in-situ hybridisation (no publication).

- (P3, Sjef van der Steen) (Evidence for VT) In the laboratory, infected larvae develop into infected queens that can successfully overwinter and found a colony the next spring, whose workers are infected (publication in preparation).

- (P3, Sjef van der Steen) (Evidence against VT) Infected adult workers do not have developed ovaries and do not lay male-destined eggs (no publication).

Evidence concerning horizontal transmission (HT):
- (P2, Ulrich Ernst) (Evidence for HT) Young workers and males can be infected by feeding them with spores (MSc. Thesis, manuscript in preparation).

- (P3, Sjef van der Steen) (Evidence for HT) Mid-aged larvae develop an infection when fed spores (manuscript ).

- (P4, Oliver Otti) (Evidence for HT) Very young larvae fed spores are usually, though not always, infected as adults.

- (P3, Sjef van der Steen and P4 Oliver Otti, in separate experiments) (Evidence for HT) Colonies experimentally infected develop infection even of individuals that were adult when spores were added to the colony (P3 manuscript in preparation).

- (P2, Julia Klee and P4, Oliver Otti, in separate experiments) (Evidence against HT) When colonies are allowed to forage upon flowers which were artificially contaminated with spores or from which infected bumble bees have been collecting nectar, they do not become infected.

- (P3, Sjef van der Steen), Administration of spores from B. pascuorum, B. lapidarius and B. hypnorum to B. terrestris larvae did not result in an infection of B. terrestris (P3 publication in preparation).

Summary:
Nosema bombi is an enigmatic species in many regards, and especially with respect to its modes of transmission. Evidence we have assembled suggests that both routes of transmission, vertical and horizontal, are used by the organism. However, the relative contribution of each to infection at the level of the individual, colony and population requires further investigation. Many of the above bullet points will be written up in manuscript form and submitted for publication in peer reviewed journals within the first 6 months of 2006. Then we aim to review the transmission of N. bombi in a manuscript, combining all experiments, published or not, for submission to a peer-reviewed journal by the end of 2006.

Reported by

Swiss Federal Institute of Technology
Ecology & Evolution, Claudiusstrasse 25 (NW)
8092 Zuerich
Switzerland
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