Abstract
BackgroundBelonging to the anopluran family Echinophthiriidae, Echinophthirius horridus, the seal louse, has been reported to parasitise a broad range of representatives of phocid seals. So far, only a few studies have focused on the vector function of echinophthiriid lice, and knowledge about their role in pathogen transmission is still scarce. The current study aims to investigate the possible vector role of E. horridus parasitising seals in the Dutch Wadden Sea.MethodsE. horridus seal lice were collected from 54 harbour seals (Phoca vitulina) and one grey seal (Halichoerus grypus) during their rehabilitation period at the Sealcentre Pieterburen, The Netherlands. DNA was extracted from pooled seal lice of individual seals for molecular detection of the seal heartworm Acanthocheilonema spirocauda, the rickettsial intracellular bacterium Anaplasma phagocytophilum, and the cell wall-less bacteria Mycoplasma spp. using PCR assays.ResultsSeal lice from 35% of the harbour seals (19/54) and from the grey seal proved positive for A. spirocauda. The seal heartworm was molecularly characterised and phylogenetically analysed (rDNA, cox1). A nested PCR was developed for the cox1 gene to detect A. spirocauda stages in seal lice. A. phagocytophilum and a Mycoplasma species previously identified from a patient with disseminated ‘seal finger’ mycoplasmosis were detected for the first time, to our knowledge, in seal lice.ConclusionsOur findings support the potential vector role of seal lice in the transmission of A. spirocauda and reveal new insights into the spectrum of pathogens occurring in seal lice. Studies on vector competence of E. horridus, especially for bacterial pathogens, are essentially needed in the future as these pathogens might have detrimental effects on the health of seal populations. Furthermore, studies on the vector role of different echinophthiriid species infecting a wide range of pinniped hosts should be conducted to extend the knowledge of vector-borne pathogens.Graphical
Highlights
Belonging to the anopluran family Echinophthiriidae, Echinophthirius horridus, the seal louse, has been reported to parasitise a broad range of representatives of phocid seals
Seal lice (8 pools of 15 specimens) from the grey seal were found positive for A. phagocytophilum and seal lice from three harbour seals were found positive for Mycoplasma sp
Analysis of the partial 16S sequence revealed that a single strain of Mycoplasma sp. was present in the seal lice obtained from three harbour seals, which was identical to a Mycoplasma sp. from an Alaska native hunter who suffered from disseminated seal finger mycoplasmosis [32]
Summary
Belonging to the anopluran family Echinophthiriidae, Echinophthirius horridus, the seal louse, has been reported to parasitise a broad range of representatives of phocid seals. Hirzmann et al Parasites Vectors (2021) 14:96 species of Phocidae, the earless or true seals, with a geographical distribution confined to the Northern Hemisphere, including harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) [1]. Due to their obligate and permanent hematophagous feeding habits [1], members of the Echinophthiriidae have the potential to play an important role in the epidemiology of vector-borne diseases in free-ranging pinniped populations. The bacterium Salmonella enteritidis was isolated from blood and tissue of Northern fur seals (Callorhinus ursinus) and from the echinophthiriid lice Antarctophthirus callorhini and/or Proechinophthirus fluctus collected from the same individuals. Southern elephant seal virus (SESV), an Alphavirus, was isolated from Lepidophthirus macrorhini parasitising the Southern elephant seal (Mirounga leonina) [6]
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