Educating insect pathologists to prevent infectious diseases in mass-reared insects
Assessing the risk of microsporidian parasites to industrially mass reared insects
January 13, 2022
I am Edouard Bessette, Early Stage Researcher 4 within the INSECT DOCTORS program studying entomopathogenic Microsporidia. I moved from France to the University of Exeter (UK) in September 2020 and am cosupervised from the University of Copenhagen. Microsporidia are considered to be some of the most prevalent pathogens amongst terrestrial insect species and it is therefore important to consider how this group of parasites is likely to affect the expanding insect rearing industry.
The main objectives of this project are: the assessment of the presence and risk of microsporidia (or other protistan parasites) within commercially reared insects; and understanding whether increasing population density increases the transmission and virulence microsporidia. I am currently trying to ascertain whether a community of microsporidia parasites is present in commercially reared insect species.. The main techniques for the detection of those parasites involve a lab work flow as well as the bioinformatic mining of insect genomic data that are available online (NCBI databases).
The laboratory techniques are based on the individual dissection of sampled insects and the observation of the tissues under microscope alongside the DNA extraction of the dissected tissues for PCR amplification. Primers used during the PCR are either found in the literature or designed to target microsporidia and other eukaryotic parasites that could pose a threat to the insect rearing industry, such as gregarines or coccidia.
The mining of insect genomic and transcriptomic data involves a blast-based search for Microsporidia and other eukaryotes parasites incidentally sequenced as part of insect genome and transcriptome sequencing projects. Analysis of this ever increasing body of data is allowing to generate a map of which microsporidian clades are found in specific insect species or groups, and will lead to a better understanding of which species may pose a risk to commercially reared insects.
With regards to the assessment of microsporidia transmission and virulence at varying densities, my initial objective was to use study the insect models Tenebrio molitor (mealworm) and Galleria mellonella (wax worm). However, our efforts to infect our model system based on past studies have not been successful so far, and the lack of infected microsporidia material from commercial sources has prevented the setting up of a host parasite study system. I will now explore other potential host parasite systems such as the cricket Acheta domesticus or the locust Locusta migratoria, which are both reported to be naturally infected with microsporidia.
I hope that the outcomes of my research with generate valuable data for the insect rearing industry regarding the diversity and the risk of that microsporidia within insect hosts.
Figure above shows screening of samples by PCR and microscopy