Abstract
Currently, the degree of passive transfer of immunoglobulins is not known for the West Indian manatee. However, in the historically related elephant, failure of passive transfer (FPT) is presumed. FPT can have serious implications for the care and management of orphaned or rejected calves where hand rearing is required. Recent studies have shown however, a significant degree of immunoglobulin transfer across the placenta in Asian elephants.1 The placental morphology of the manatee, similar to that of the elephant, suggests that some degree of passive transfer is possible, though the true extent remains to be defined. To most effectively examine this hypothesis in manatees, samples from pre-suckling manatees as well as colostrum are optimal. These samples are difficult to obtain in Florida since captive breeding programs do not exist. Samples are opportunistic and often collected from orphaned animals entering rehabilitation and/or carcasses. For this study, collaborations with international facilities in which manatee breeding opportunistically occurs as well as those collaborations with various manatee rehabilitation facilities, allowed us to utilize archived blood samples collected from West Indian manatee calves to investigate passive transfer and provide preliminary data on developmental immunology in the manatee.
To measure IgG in manatee calves, the UF developed anti-manatee IgG mAb was incorporated into a custom quantitative biolayer interferometry assay using the Octet QKe system (FortéBio, Inc.).1 This study included blood samples from both pre-suckling and post-suckling calves as well as fetal blood samples and covered a range of specific calf ages of both free ranging manatees and those in a rehabilitation setting. Calf and fetal IgG blood values were compared to previously established reference ranges and average IgG values for adult/subadult West Indian manatees and sub-species.1 Samples of fetal Florida manatee sera revealed a mean IgG of 26.01 mg/mL, suggesting significant passive placental transfer of antibodies from cow to calf, similar to that observed in the historically related Asian elephant. Mean IgG values from calves in a rehabilitation setting exhibited a significantly lower (IgG < 4.5 mg/mL) total IgG value below the adult/subadult West Indian manatee IgG average and reference range. However, IgG values from free ranging manatees' calves (8.24 mg/mL) were not significantly different from those of subadults or adults. As part of this study, we also included blood samples from a captive managed Antillean manatee calf from birth (pre-suckling) to 4 mo (not hand-reared), further supplementing the preliminary data on developmental immunology in the West Indian manatee presented in this study.
Transfer of immunoglobulins can occur passively, across the placenta, and/or actively, through ingestion of colostrum and milk. This study provides the first documentation of transplacental transfer of immunoglobulins in manatees. However, the extreme low IgG values observed in orphaned manatee calves in rehabilitation warrants further investigation as failure of adequate transfer of immunoglobulins can contribute to the mortality of hand-reared calves by potentially increasing susceptibility to pathogens and possibly impairing immunological development.
Acknowledgements
The authors would like to thank Dr. Robert K. Bonde and the U.S. Geological Survey's Southeast Ecological Science Center -Sirenia Project, Dr. James 'Buddy' Powell and Sea to Shore Alliance, Fabia Luna and Dr. Fernanda Löffler Niemeyer Attademo and O Centro Nacional de Pesquisa e Conservação de Mamíferos Aquáticos-CMA/ICMBio, Dr. Ray Ball and the Lowry Park Zoological Society, Dr. Roberto Sanchez Okrucky and Dolphin Discovery and Dr. Benjamin Morales and ECOSUR for contributing samples for this study. Research funding was provided through the University of Florida (UF)-Aquatic Animal Health Program at the College of Veterinary Medicine (CVM), Florida Fish and Wildlife Conservation Commission, the UF Whitney Marine Laboratory for Marine Bioscience, and the UF-CVM Consolidated Faculty Research Development. This study was conducted under IACUC #201106011, Federal Fish and Wildlife Permit (USFWS) #MA067116-1 and #MA791721, and CITES Permit #11US808447 and # 12US42872A/9.
* Presenting author
+ Student presenter
Literature Cited
1. McGee, JL. 2012. Immunological investigations in the West Indian manatee (Trichechus manatus) and Asian elephant (Elephas maximus). Gainesville: University of Florida.