Article: Experimental Challenge of Atlantic Cod (Gadus
morhua) with a Brucella pinnipedialis Strain
from Hooded Seal (Cystophora cristata)
Authors:
Journal: PLoS ONE 11(7): e0159272. doi:10.1371/journal.pone.0159272
Abstract:
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 (Cystophora cristata)
macrophages in vitro indicates
a lack of chronic infection in hooded seals. Both epidemiology and bacteriological patterns in the 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 injected intraperitoneally with 7.5 x 107bacteria
of a hooded seal field isolate. Samples of blood, liver, spleen, muscle, heart, head kidney, female gonads and feces were collected on days 1, 7, 14 and 28 post infection to assess the bacterial load, and to determine the expression of immune genes and the
specific antibody response. Challenged fish showed an extended period of bacteremia through day 14 and viable bacteria were observed in all organs sampled, except muscle, until day 28. Neither gross lesions nor mortality were recorded. Anti-Brucella antibodies
were detected from day 14 onwards and the expression of hepcidin, cathelicidin, interleukin (IL)-1β, IL-10, and interferon (IFN)-γ genes were significantly increased in spleen at day 1 and 28. Primary mononuclear cells isolated from head kidneys of Atlantic
cod were exposed to B. pinnipedialis reference
(NCTC 12890) and hooded seal (17a-1) strain. Both bacterial strains invaded mononuclear cells and survived intracellularly without any major reduction in bacterial counts for at least 48 hours. Our study shows that the B. pinnipedialis strain
isolated from hooded seal survives in Atlantic cod, and suggests that Atlantic cod could play a role in the transmission of B.pinnipedialis to
hooded seals in the wild.
Ingebjorg Helena Nymo
DVM, PhD
Post Doctoral Researcher
Research Group of Arctic Infection Biology
Department of Arctic and Marine Biology
Faculty of Biosciences, Fisheries and Economics
University of Troms? - The Arctic University of Norway