Interspecific competition in honeybee intracellular gut parasites is asymmetric and favours the spread of an emerging infectious disease

There is increasing appreciation that hosts in natural populations are subject to infection by multiple parasite species. Yet the epidemiological and ecological processes determining the outcome of mixed infections are poorly understood. Here, we use two intracellular gut parasites (Microsporidia), one exotic and one co-evolved in the western honeybee (Apis mellifera), in an experiment in which either one or both parasites were administered either simultaneously or sequentially. We provide clear evidence of within-host competition; order of infection was an important determinant of the competitive outcome between parasites, with the first parasite significantly inhibiting the growth of the second, regardless of species. However, the strength of this ‘priority effect’ was highly asymmetric, with the exotic Nosema ceranae exhibiting stronger inhibition of Nosema apis than vice versa. Our results reveal an unusual asymmetry in parasite competition that is dependent on order of infection. When incorporated into a mathematical model of disease prevalence, we find asymmetric competition to be an important predictor of the patterns of parasite prevalence found in nature. Our findings demonstrate the wider significance of complex multi-host–multi-parasite interactions as drivers of host–pathogen community structure

Characterisation of a beta-tubulin gene from the liver fluke, Fasciola hepatica.

This study represents the first ß-tubulin sequence from a trematode parasite, namely, the liver fluke, Fasciola hepatica. PCR of genomic DNA showed that at least one ß-tubulin gene from F. hepatica contains no introns. A number of amino acids in the primary sequence of fluke tubulin are different from those described previously in various nematode species and the cestode, Echinococcus multilocularis. ß-Tubulin is an important target for benzimidazole anthelmintics, although (with the exception of triclabendazole) they show limited activity against F. hepatica. The amino acid differences in fluke ß-tubulin are discussed in relation to the selective toxicity of benzimidazoles against helminths and the mechanism of drug resistance.

The FLP-side of nematodes.

The central role of FMRFamide-like peptides (FLPs) in nematode motor and sensory capabilities makes FLP signalling an appealing target for new parasiticides. Accumulating evidence has revealed an astounding level of FLP sequence conservation and diversity in the phylum Nematoda, and preliminary work has begun to identify the nematode FLP receptor complement in Caenorhabditis elegans, with a view to investigating their basic biology and therapeutic potential. However, much work is needed to clarify the functional aspects of FLP signalling and how these peptides exert their effects at the organismal level. Here, we summarize our current knowledge of nematode FLP signalling.