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Updated 18.03.2016

Our book " Suomen kalojen loiset"

Gaudeamus, Helsinki 2012, compiles all knowledge on fish parasites in Finland.



Katja Pulkkinen, PhD, Docent, University researcher 

e-mail: katja.pulkkinen(at) *

Department of Biological and Environmental Science

P.O. Box 35, FI-40014 University of Jyväskylä
Tel. +358406800213

* replace (at) with @

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.