Exposure of harbour seals (Phoca vitulina) to Brucella in declining populations across Scotland

JL Kershaw, EJ Stubberfield, G Foster, A Brownlow, AJ Hall, LL Perrett

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

Since 2000 there have been major declines in the abundance of Scottish harbour seals (Phoca vitulina). The causes of the declines remain uncertain. The aim of this study was to establish the extent to which the seals in the regions of greatest decline have been exposed to Brucella, a bacterial pathogen that causes reproductive failure in terrestrial mammalian hosts. Tissues from dead seals collected between 1992 and 2013 were cultured for Brucella (n=150). Serum samples collected from live capture-released seals (n=343) between 1997 and 2012 were tested for Brucella antibodies using the Rose Bengal plate agglutination test (RBT) and a competitive Enzyme-Linked Immunosorbent Assay (ELISA). 16% of seals cultured had Brucella isolated from one or more tissues but there were no pathological signs of infection. The cELISA results were more sensitive than the RBT results showing that overall, 25.4% of seals were seropositive with the highest seroprevalence in juveniles. As there was no evidence of either a higher seroprevalence, or higher circulating antibody levels in seropositive animals in the areas with the greatest declines, it was concluded that Brucella infection is likely not a major contributing factor to recent declines. However, the consistently high proportion of seals exposed to Brucella indicates possible endemicity in these populations, likely due to Brucella pinnipedialis, which has demonstrated a preference for pinniped hosts. Importantly, given the close proximity between seals, humans and livestock in many areas, there is the potential for cross-species infections.
Original languageEnglish
Pages (from-to)13 - 23
Number of pages11
JournalDiseases of Aquatic Organisms
Volume126
Issue number1
Early online date20 Sep 2017
DOIs
Publication statusFirst published - 20 Sep 2017

Fingerprint

Phoca vitulina
Brucella
seals
Scotland
seroprevalence
infection
antibodies
host preferences
agglutination tests
indigenous species
livestock
enzyme-linked immunosorbent assay
pathogens

Bibliographical note

20102518

Keywords

  • Antibodies
  • Brucella
  • Cultures
  • Disease
  • ELISA
  • Pinnipeds
  • Rose Bengal plate agglutination test
  • Seroprevalence

Cite this

Kershaw, JL ; Stubberfield, EJ ; Foster, G ; Brownlow, A ; Hall, AJ ; Perrett, LL. / Exposure of harbour seals (Phoca vitulina) to Brucella in declining populations across Scotland. In: Diseases of Aquatic Organisms. 2017 ; Vol. 126, No. 1. pp. 13 - 23.
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Exposure of harbour seals (Phoca vitulina) to Brucella in declining populations across Scotland. / Kershaw, JL; Stubberfield, EJ; Foster, G; Brownlow, A; Hall, AJ; Perrett, LL.

In: Diseases of Aquatic Organisms, Vol. 126, No. 1, 20.09.2017, p. 13 - 23.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Exposure of harbour seals (Phoca vitulina) to Brucella in declining populations across Scotland

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AU - Stubberfield, EJ

AU - Foster, G

AU - Brownlow, A

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AB - Since 2000 there have been major declines in the abundance of Scottish harbour seals (Phoca vitulina). The causes of the declines remain uncertain. The aim of this study was to establish the extent to which the seals in the regions of greatest decline have been exposed to Brucella, a bacterial pathogen that causes reproductive failure in terrestrial mammalian hosts. Tissues from dead seals collected between 1992 and 2013 were cultured for Brucella (n=150). Serum samples collected from live capture-released seals (n=343) between 1997 and 2012 were tested for Brucella antibodies using the Rose Bengal plate agglutination test (RBT) and a competitive Enzyme-Linked Immunosorbent Assay (ELISA). 16% of seals cultured had Brucella isolated from one or more tissues but there were no pathological signs of infection. The cELISA results were more sensitive than the RBT results showing that overall, 25.4% of seals were seropositive with the highest seroprevalence in juveniles. As there was no evidence of either a higher seroprevalence, or higher circulating antibody levels in seropositive animals in the areas with the greatest declines, it was concluded that Brucella infection is likely not a major contributing factor to recent declines. However, the consistently high proportion of seals exposed to Brucella indicates possible endemicity in these populations, likely due to Brucella pinnipedialis, which has demonstrated a preference for pinniped hosts. Importantly, given the close proximity between seals, humans and livestock in many areas, there is the potential for cross-species infections.

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KW - Brucella

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KW - Disease

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KW - Rose Bengal plate agglutination test

KW - Seroprevalence

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