abstract
The large lungworm of seals, Otostrongylus circumlitus, is the most common cause of mortality of stranded juvenile northern elephant seals (NES), Mirounga angustirostris, along the central California coast. In this host, the clinical signs are non-specific, and juvenile mortality often occurs with low intensity infections during the pre-patent period of the nematode life cycle. Therefore it is necessary to have reliable diagnostic tests for infection that are independent of coprological examination for larvae. We have developed two types of diagnostic tests, quantitative real-time polymerase chain reaction (q-PCR) for the detection of O. circumlitus nucleic acid in NES blood, and enzyme linked immunosorbent assay (ELISA) for detection of anti-O. circumlitus antibodies in both NES and Pacific harbor seal (PHS), Phoca vitulina richardsi, serum.1 Here, we report optimization of q-PCR using primers for O. circumlitus 28S rDNA in conjunction with primers for NES Apo B, as a host control gene. This diagnostic test successfully detected O. circumlitus DNA in vitro, and is currently being applied to frozen blood samples from infected and uninfected animals. We also report the further optimization of the ELISA by using a seal-specific secondary monoclonal antibody (H49A). The improved assay has a high sensitivity, specificity, and reproducibility that has enhanced our ability to differentiate infected from uninfected animals. In combination, these two methods provide a strong platform for designing studies to examine clinical disease caused by O. circumlitus, and to explore the natural history of this parasite in free-ranging populations.
acknowledgements
The authors wish to thank the staff and volunteers at The Marine Mammal Center, Sausalito, California, and Sea World, San Diego, California for sample collection. This work was partially supported by a John H. Prescott marine mammal assistance grant (NA06NMF4390133).
References
1. Elson-Riggins JG, Gulland FM, Aldridge BM. 2007. Development of diagnostic tests for Otostrongylus circumlitus infection in northern elephant seals. Abstr. Proc. Wildlife Disease Association. Pp. 60.