Séminaire CEFE : Brucella infections in seals and fish: not just another disease story

vendredi 24 mai 10h,

Grande salle de réunion

Jacques Godroid 
Department of Arctic and Marine Biology,
 UiT – The Arctic University of Norway, Tromsø, Norvège

Investigations of hooded seals (Cystophora cristata) have revealed high prevalences of Brucella-positive seals in the reduced Northeast Atlantic stock, compared to the increasing Northwest Atlantic stock. Pathology has not been observed in true seals infected with Brucella pinnipedialis. A lack of intracellular survival and multiplication of B. pinnipedialis in hooded seal macrophages in vitro indicates a lack of chronic infection in hooded seals. Both epidemiology and bacteriological patterns in hooded seal point to a transient infection of environmental origin, possibly through the food chain. To analyse the potential role of fish in the transmission of B. pinnipedialis, Atlantic cod (Gadus morhua) were infected experimentally with B.pinnipedialis. We further analyzed how thermal stress influenced the fish immune responses against an opportunistic intracellular bacterium. Following experimental infection with B. pinnipedialis at normal water temperature (6◦C) and sub-optimal temperature (15◦C), cod cleared the intracellular bacteria more rapidly at the highest temperature. The overall immune response was faster and of higher amplitude at 15◦C, however, a significant number of cod died at this temperature despite efficient clearance of infection. Our results suggest that Atlantic cod could play a role in the transmission of B.pinnipedialis to hooded seals in the wild and a trade-off between resistance and tolerance to survive infection at sub-optimal temperatures. This raises questions concerning the impact of increased water temperatures on the energetic costs of immune system activation in aquatic ectotherms.
 
References
Nymo I.H., Tryland M., Frie A.K., Haug T., Foster G., Rødven R., Godfroid J. 2013. Age-dependent prevalence of anti-Brucella antibodies in hooded seals (Cystophora cristata). Dis. Aquat. Organ., 106: 187-196.
Larsen A.K., Nymo I.H., Sørensen K.K., Briquement B., Godfroid J. 2013. Entrance and survival of Brucella pinnipedialis hooded seal strain in human macrophages and epithelial cells. PLoS One, 8: e84861.
Larsen A.K., Nymo I.H., Sørensen K.K., Seppola M., Rødven R., Jiménez de Bagüés M.P., Al Dahouk S., Godfroid J. 2018. Concomitant Temperature Stress and Immune Activation Induce Mortality Despite Efficient Clearance of an Intracellular Bacterial Infection in Atlantic Cod. Front. Microbiol/doi.

Contact au CEFE : Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.