With increasing concerns over antibiotic resistance in bacterial and other pathogens, the search for novel approaches to infection control other than stimulation of classic adaptive immunity (vaccination) are increasingly being sought. The idea of controlling a pathogen with another microorganism is not new and was initiated originally by Felix d’Herelle, one of the co-discoverers of bacteriophages. d’Herelle had earlier explored the idea of using pathogenic bacteria to control grasshoppers.
Because of a lack of understanding of both phage and bacterial pathogenesis at that time, initial experimental work in phage biocontrol by d’Herelle and those of his colleagues and followers used treatments with phage preparations of uncertain content and quality and not infrequently involving poorly conceived and uncontrolled experiments. Benefiting from our increasing understanding of pathogenesis and using more appropriate models, more recent and more rigorous experimental work has shown the value of using phages in bacterial control. Despite this, the large scale application of phages for infection control remains to be fully exploited.
In highly complex ecosystems, whether on the macro- or micro-scale, a wide variety of interactions involving competition, parasitism, and symbiosis can be found, sometimes with pathogens occupying different roles dependent on the nature of the host. Viruses have been identified for almost every species of higher animal and for most prokaryotes for which they have been sought. For any interaction of this sort, whether it be microbial pathogen and host or parasitic nucleic acid and host genome, the parasitizing entity will drive evolution of the host and vice versa. Such genetic and ecological interactions must be taken into account when considering the biological control of one organism by another.
Fleas and smaller fleas: virotherapy for parasite infections. Trends in Microbiology 26 Mar 2013 doi: 10.1016/j.tim.2013.02.006
Bacteriophages are viruses of bacteria that are used for controlling bacterial food-borne pathogens and have been proposed for more extensive usage in infection control. Protists are now recognised to harbour viruses and virus-like particles. We propose that investigation of their prevalence in parasites be intensified. We also propose that such viruses might be considered for virotherapy to control certain parasite infections of man and animals.