Development of rapid diagnostic tests

A wide range of monoclonal antibodies has now been produced enabling detection of a large number of economically significant fish pathogens (bacterial, viral, parasitic and fungal) using a variety of immunodiagnostic tests (immunohistochemistry, IFAT and ELISA). Antibodies developed to detect fish pathogens include those against Aphanomyces invadans, Flavobacterium psychrophilum, Lactococcus garvieae, Mycobacterium spp., Photobacterium damselae subspecies piscicida, Piscirickettsa salmonis, Noda virus, Renibacterium salmoninarum, Streptococcus iniae, and Tetracapsuloides bryosalmonae. Very sensitive molecular methods, such as PCR, reverse cross blot PCR and in situ hybridisation tests have also been developed to detect and identify many of these pathogens in environmental samples as well as fish tissue.

Detection of specific antibodies in the serum of animals is recognised as a useful indicator of previous exposure to pathogens and is regularly used in both clinical and veterinary medicine. This type of serology is often used when it is not possible to isolate the pathogen by traditional methods or when rapid tests to identify the pathogen have not yet been developed. The anti-fish species IgM antibody probes required for such tests have now been developed enabling screening for pre-exposure to disease in a variety of fish species, including Asian sea bass (Lates calcarfier), Atlantic salmon (Salmo salar), cod (Gadus morhua), giant gourami (Osphronemus goramy), grouper (Epinephelus spp.), halibut (Hippoglossus hippoglossus), European sea bass (Dicentrarchus labrax), sea bream (Sparus aurata) ,tilapia (Oreochromis niloticus), turbot (Scopthalmus maximus), trout (Oncorhynchus mykiss) and sturgeon (Acipencer spp.). ELISA provides a convenient method for testing large sample numbers and testing is non-destructive, requiring only a serum sample.

Currently monoclonal antibodies are being developed against a variety of Vibrio species, ISAV and to components of the fish immune system. Novel antibodies and immunodiagnostic tests are developed as part of the Unit's research programme as new pathogens emerge and new fish species are cultured. Current research is focusing on the development of multiplex tests (both antibody based and molecular) for the identification of fish pathogens and components of the fish immune system.

Prevention of fish diseases by protective bacteria in aquaculture

The aim of this research is to study and optimize protective bacteria which work as biological control agents against fish diseases in aquaculture conditions. Specifically, we focus on prevention of Flavobacterium infections, which are serious pathogens in freshwater fish farms and causes loses especially for fish eggs and juveniles. However, there are no specific treatments available for these pathogens. Furthermore, in aquaculture practices several chemotherapeutics and antibiotics has been recently banned or their use is restricted because of their toxicity for the environment and pathogens increasing bacterial resistance for the antibiotics. We have isolated in our earlier research putative protective bacteria, which hinder growth of Saprolegnia in rainbow trout hatchery and several Flavobacterium strains in vitro. The aim of the research in Aquatic Vaccine Unit is to concentrate on mode of the action of the protective bacteria. In practice, we will define (i) optimal manipulation of the protective bacteria for rainbow trout fry, (ii) effect of the protective bacteria for the developing immunity of fry, (iii) determine adhesion capability of the protective bacteria into the fish gills, skin and intestinal mucus and (iv) investigate does the protective bacteria diminish number of Flavobacterium on fish surfaces and mucus during disease challenge.

Although the probiotics of fish has been studied quite extensively, this is the first time that these putative probiotic bacteria have been isolated from fish eggs. Healthy eggs promote growth of indigenous microbial flora, which play major role also in establishment of immunity and a protective microbial flora of fish during young life stages. In addition, expected result is to optimize more sustainable and ecofriendly disease management for the aquaculture industry. This research has been funded by the University of Kuopio foundation and the Academy of Finland.

Development of vaccines

Fish Vaccines developed at/in collaboration with the Aquatic Vaccine Unit include 3 that have been commercialised for Vibriosis, Enteric Red Mouth and Furunculosis. Further vaccines against Pasteurellosis, Bacterial Kidney Disease and Rainbow Trout Fry Syndrome are undergoing field-testing, while current research is focusing on Proliferative Kidney Disease and Piscirickettsiosis.

Host pathogen interactions

A variety of research projects are currently in progress to investigate host-pathogen interactions, including projects on Mycobacteriosis, Rainbow Trout Fry Syndrome, Piscirickettsiosis and Proliferative Kidney Disease.

Immunomodulation of the immune system

Dietary supplementation can be a useful way of modulating the immune system in fish to enhance health and increase resistance to disease. Projects are in progress to investigate the effects of a variety of compounds on the immune response of fish, including organic chromium, and alternative dietary oil sources.

Seasonality on the Immune Response of Rainbow Trout

Seasonality is primarily made up of photoperiod and temperature. We are currently trying to establish if the pineal hormone melatonin, which is considered to be an internal "zeitgeber" in vertebrates, has any immunostimulatory effect and/or a timing and control effect on the regulation of the immune response of (Oncorhynchus mykiss)