Abstract
Brucella ceti infection is associated with a variety of disease outcomes in cetaceans globally. Multiple genotypes of B. ceti have been identified. This retrospective aimed to determine if specific lesions were associated with different B. ceti DNA sequence types (STs). Characterization of ST was performed on 163 samples from 88 free-ranging cetaceans, including common bottlenose dolphin Tursiops truncatus (T.t.; n = 73), common short-beaked dolphin Delphinus delphis (D.d.; n = 7), striped dolphin Stenella coeruleoalba (n = 3), Pacific white-sided dolphin Lagenorhynchus obliquidens (n = 2), sperm whale Physeter macrocephalus (n = 2), and harbour porpoise Phocoena phocoena (n = 1), that stranded along the coast of the US mainland and Hawaii. ST was determined using a previously described insertion sequence 711 quantitative PCR. Concordance with 9-locus multi-locus sequence typing was assessed in a subset of samples (n = 18). ST 26 was most commonly identified in adult dolphins along the US east coast with non-suppurative meningoencephalitis (p = 0.009). Animals infected with ST 27 were predominately perinates that were aborted or died shortly after birth with evidence of in utero pneumonia (p = 0.035). Reproductive tract inflammation and meningoencephalitis were also observed in adult T.t. and D.d. with ST 27, though low sample size limited interpretation. ST 23 infections can cause disease in cetacean families other than porpoises (Phocoenidae), including neurobrucellosis in D.d. In total, 11 animals were potentially infected with multiple STs. These data indicate differences in pathogenesis among B. ceti STs in free-ranging cetaceans, and infection with multiple STs is possible.
Highlights
Results of the insertion sequence 711 (IS711) quantitative PCR (qPCR) were compared to sequence typing from the 9-locus multi-locus sequence typing (MLST), considered the gold standard for purposes of this study
For comparison among independent variables, bivariate and multivariate logistic regression analyses were utilized for sequence types (STs)-specific B. ceti infection lesion associations
There was 100% concordance between the 9-locus MLST results and IS711 SYBR qPCR identification of ST; the IS711 qPCR for 3 samples were positive for both ST 26 and ST 27 (Tables 1 & S1)
Summary
A zoonotic pathogen, has been isolated from dolphins, whales, porpoises, and some pinnipeds and phocids (Foster et al 2007, Whatmore et al 2008, Nymo et al 2011, Guzmán-Verri et al 2012, Hernández-Mora et al 2013, Whatmore et al.2017). Marine Brucella strains have been placed into ST groups first based on 9locus multi-locus sequence typing (MLST; Whatmore et al 2007) and more recently by an extended 21 locus multi-locus sequence analysis (MLSA; Whatmore et al 2017) These PCR tests examine multiple housekeeping genes, and surveys have grouped marine strains into hooded seal Cystophora cristata/harp seal Pagophilus groenlandicus (STs 53 and 54), pinniped (STs 24, 25, and 52), dolphin (ST 26), porpoise (ST 23), and ST 27 clusters. Though the risk of zoonotic transmission appears low, questions remain as to the mode of transmission in community acquired cases (Whatmore et al 2008)
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