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The main
theme in my work is to study how ecological factors can modulate the
outcome of
host-parasite interactions and the transmission, persistence and
virulence of
parasites. Currently I am studying the effect of environmental
nutrients
in driving the evolution of virulence in a pathogenic fish bacterium Flavobacterium
columnare,
which is a major threat to salmonid fingerling farming in Finland and
channel
catfish farming in US.
In my
research with the model system consisting of Daphnia-waterfleas and their microparasites, I
have been studying e.g. the interactions between resource quality (in
terms of
Carbon:Nitrogen:Phosphorus-ratios)
and parasites in Daphnia
both in laboratory and in the field, as well as the effects of
nutritional
stress, predation or host community structure
on the
persistence and transmission of parasites in host populations or
between
individuals. The results of this work have shown that both nutritional
stress
and size-selective predation have a potential to constrain the
occurrence and
persistence of parasites in the host populations. Interestingly, as was
shown
for predation, they could also be a factor promoting co-existence of a
virulent
parasite with its host. I have also shown that the presence of a conspecific, even a resistant
one, can decrease the
transmission of parasites between Daphnia
individuals (dilution
effect).
In my PhD-work I studied the transmission of a cestodan fish parasite Triaenophorus
crassus which has a copepod as the first intermediate host
and two coregonid
fishes as second intermediate hosts. Experimental
infections of copepods with parasite eggs hatched in the laboratory
showed e.g.
that the parasite facilitates its transmission by making the copepod
host more
vulnerable to fish predation. In the field I was trying to find a proof
that strong
fluctuations in the abundance of the host which was less susceptible
but a
superior competitor could affect the transmission of the parasite to
the host
which was more susceptible but a poorer competitor.
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