Survey for Selected Pathogens and Evaluation of Disease Risk Factors for Endangered Hawaiian Monk Seals in the Main Hawaiian Islands

Abstract

A recently reestablished and increasing population of Hawaiian monk seals in the main Hawaiian Islands (MHI) is encouraging for this endangered species. However, seals in the MHI may be exposed to a broad range of human, pet, livestock, and feral animal pathogens. Our objective was to determine the movement and foraging habitats of Hawaiian monk seals in the MHI relative to the potential exposure of seals to infectious diseases in near-shore marine habitats. We captured 18 monk seals in the MHI between January 27, 2004 and November 29, 2005, tested them for various infectious diseases, and then monitored the foraging movements of 11 of them using satellite-linked radio transmitters for the next 32-167 days. All seals tested negative for canine adenovirus, calicivirus, four morbilliviruses, phocine herpes virus, Leptospira sp., and feline and canine heartworm antigen/antibody. Six of the seals tested positive on complement fixation for Chlamydophila abortus (formerly Chlamydia psittaci). Four seals demonstrated positive titers to Sarcocystis neurona, two to Neospora caninum, and two to Toxoplasma gondii. Fecal cultures showed approximately half (n = 6) positive for E. coli 0157, no Salmonella sp., and only one with Campylobacter sp. Satellite monitored seals spent considerable time foraging, traveling, and resting in neritic waters close to human population centers, agricultural activity, and livestock ranges, and sources of land-based water runoff and sewage dispersal.Consequently, Hawaiian monk seals in the MHI may be at risk of exposure to several infectious disease agents associated with terrestrial animals that can contaminate marine habitats from runoff along drainages and that are known to cause disease in marine mammals. Further, some seals overlapped substantially in their use of coastal habitats and several moved among islands while foraging and were seen on beaches near each other.This suggests that diseased seals could infect healthy conspecifics throughout the MHI.

An integrated approach for assessing translocation as an effective conservation tool for Hawaiian monk seals

“…Thus, it seems unlikely that the low antibody titers for C. abortus detected in many resident and translocated seals affected translocation success. Similarly, most enteric bacteria cultured from seals in this study, some of which are potentially pathogenic (Thornton et al 1998, Xie et al 2005, were present in monk seals at other sites (Aguirre 1998, Littnan et al 2007). Vibrio spp.…”

“…It was not possible, however, to perform real-time infectious disease screening on translocated or resident seals before translocations due to the remoteness of the NWHI. Instead, the potential disease exposure risk was deemed minimal because clinical signs of disease were not observed in monk seals at the donor or release sites prior to translocations and few infectious agents or antibodies have been detected in monk seals across the Hawaiian Archipelago (Aguirre et al 2007, Littnan et al 2007). An exception to this is that, similar to this study, Chlamydophila abortus antibodies have been found in 36 to 70% of monk seals at most NWHI sites (Aguirre et al 2007).…”

Genome-Wide Loss of Diversity in the Critically Endangered Hawaiian Monk Seal

“…Climate change may result in reduced prey and habitat availability through lowered productivity and sea-level rise [74,75]. The growing presence of seals in the MHI will likely result in increased human-seal and dog-seal interactions, with greater potential for exposure to introduced infectious diseases [76]. The low genetic diversity described herein heightens concern regarding the future of the Hawaiian monk seal.…”

Protozoal-related mortalities in endangered Hawaiian monk seals Neomonachus schauinslandi

“…Physical examination revealed that both patients were in good nutritional condition, anorexic, and tachypneic with increased respiratory effort. Reference values (± SD) for live-captured, healthy animals from Reif et al (2004) time (Littnan et al 2007). While risk factors for the development of fulminant disease are not yet well understood, the increasing number of mortalities and severity of T. gondii infections in affected seals suggest that terrestrially-sourced protozoal parasites could pose a substantial impediment to population recovery, in particular in the MHI, where the definitive host of this parasite is abundant.…”

“…California sea lions Zalophus californianus, for example, are definitive and intermediate hosts to at least 4 coccidian parasites that cause little to no disease (Colegrove et al 2011, Carlson-Bremer et al 2012). Exposure to protozoa has been serologically determined in many pinniped taxa (Measures et al 2004, Littnan et al 2007, ABSTRACT: Protozoal infections have been widely documented in marine mammals and may cause morbidity and mortality at levels that result in population level effects. The presence and potential impact on the recovery of endangered Hawaiian monk seals Neomonachus schauinslandi by protozoal pathogens was first identified in the carcass of a stranded adult male with disseminated toxoplasmosis and a captive monk seal with hepatitis.…”