Health and Disease Research and Emergency Response Initiative

Comparison of body condition between two weaned Hawaiian monk seal pups.
Comparison of body condition between two weaned Hawaiian monk seal pups.

The Health and Disease Research and Emergency Response Initiative investigates the role infectious diseases, parasites, and toxins (anthropogenic or human caused, and naturally occurring biotoxins) play in the recovery of the Hawaiian monk seal population. Studies include gross necropsy and histopathology, parasitology, hematology, serology, morphometrics, microbiology, and epidemiology to assess population health. Additional activities include critical response to potentially life threatening situations for monk seals.

The Hawaiian Monk Seal Health and Disease Research and Emergency Response Initiative lead is Michelle Barbieri, DVM, MS.

Infectious Disease

Close contact with other animals can spread some diseases.
Close contact with other animals can spread some diseases.

New disease threats are constantly emerging and diseases in terrestrial, avian and other marine mammal species could threaten monk seals. Given that monk seals are endangered, have very low genetic diversity, and have not been exposed to many diseases due to the isolation of the Hawaiian Archipelago, the potential impact of infectious disease on the monk seal population could be severe and have devastating population-level impacts. Thus vigilant infectious disease surveillance is constantly maintained. Additionally, a Hawaiian Monk Seal Vaccination Research and Response Plan was developed to proactively address this threat, particularly for morbillivirus and West Nile virus infections.

In the main Hawaiian Islands (MHI), monk seals forage, travel and rest in close proximity to areas of human activity, domestic and feral animals, and agricultural areas. This increases exposure to contaminated waters from sewage and land based surface run-off, increasing the probability of infectious disease transmission. Monk seal movements throughout the MHI and Northwestern Hawaiian Islands (NWHI) suggest any diseased seal could quickly infect healthy seals, with the potential of causing debilitating impacts to the monk seal population including mass mortality.

Multiple pathogens which are a known risk for pinnipeds (seals and sea lions) and cetaceans (whales and dolphins) are monitored. Some of the infectious diseases that pose a risk to the Hawaiian monk seal population include distemper viruses, West Nile virus, Leptospira spp., and Toxoplasma gondii.

Canine and phocine distemper virus infections have caused mass die offs of tens of thousands of other phocids. Risk factors for Hawaiian monk seals include cetaceans and non-native pinniped species that carry morbillivirus into Hawaiian waters and interactions between monk seals and infected dogs. Fortunately, distemper virus in Hawaii is rarely diagnosed in domestic pets; however, the first Hawaii report of morbillivirus in a marine mammal (a stranded beaked whale) was in 2010. Monk seals continue to be screened for exposure and infection due to the known devastating impact these viruses have on other marine and terrestrial species.

West Nile virus has not been detected in Hawaii or in wild marine mammals. However, this mosquito-borne pathogen has been attributed to the deaths of a captive Hawaiian monk seal at Sea World San Antonio, Texas, and captive harbor seals on the mainland United States. Because of public health concerns, the State of Hawaii has rigorous surveillance and response plans. West Nile virus is one of the two viruses identified in the monk seal vaccination plan.

Leptospirosis is widespread worldwide. In Hawaii, mongoose and rodents are the principle vectors where transmission of the bacteria is made through direct or indirect contact with infected urine. Evaluation of testing methods and monitoring of Leptospira infections are ongoing to determine potential lethal impacts on monk seals.

Toxoplasma gondii is a microscopic protozoan parasite. The oocytes (immature egg cells) are found in cat feces which contaminate the ocean environment via terrestrial run-off. A seal may become infected either through direct contact or through ingestion of contaminated prey. T. gondii is potentially fatal and is thought to be a cause of mortality in the southern sea otter population along the central California coast. This pathogen was first identified in Hawaiian monk seals in 2004, and the deaths of several seals have been attributed to T. gondii infection. The impact of T. gondii and other protozoal parasites on monk seals continues to be examined and monitored.

Ongoing efforts include improvement of infectious disease surveillance and rapid response and treatment of infected seals. Additional research is aimed to develop more accurate testing methods for existing and emergent diseases specific to Hawaiian monk seals to enhance our ability to better mitigate the effects of these diseases.

Further Reading:

Pacific Islands Fisheries Science Center
2017. 2016 report on Hawaiian monk seal vaccination program. Pacific Islands Fisheries Science Center, PIFSC Data Report, DR-17-010, 12 p. doi:10.7289/V5/DR-PIFSC-17-010
Hawaiian Monk Seal Vaccination Research and Response Plan
Aguirre AA, Keefe TJ, Reif JS, Kashinsky L, Yochem PK, Saliki JT, Stott JL, Goldstein T, Dubey JP, Braun R, Antonelis G
2007. Infectious disease monitoring of the endangered Hawaiian monk seal. Journal of Wildlife Diseases 43(2): 229-241. DOI: 10.7589/0090-3558-43.2.229
Baker JD, Harting AL, Barbieri MM, Johanos TC, Robinson SJ, Littnan CL
2016. Estimating contact rates of Hawaiian monk seals (Neomonachus schauinslandi) using social network analysis. Journal of Wildlife Diseases 52(3):533-543. doi:10.7589/2015-10-286
Barbieri MM, Kashinsky L, Rotstein DS, Colegrove KM, Haman KH, Magargal SL, Sweeny AR, Kaufman AC, Grigg ME, Littnan CL
2016. Protozoal-related mortalities in endangered Hawaiian monk seals Neomonachus schauinslandi. Diseases of Aquatic Organisms. 121(2):85-95. doi:Diseases of Aquatic Organisms. 121(2):85-95. doi:10.3354/dao03047
Hanson MT, Aguirre AA, Braun RC
2009. Clinical observations of ocular disease in Hawaiian monk seals (Monachus schauinslandi). U.S. Dept. of Commer., NOAA Tech. Memo. NOAA-TM-NMFS-PIFSC-18, 9 p.
Honnold, SP, Braun R, Scott DP, Sreekumar C, Dubey JP
2005. Toxoplasmosis in a Hawaiian monk seal (Monachus schauinslandi). Journal of Parasitology 91: 695–697. DOI: 10.1645/ge-469r
Littnan CL, Stewart BS, Yochem PK, Braun R
2006. Survey for selected pathogens and evaluation of disease risk factors for endangered Hawaiian monk seals in the main Hawaiian Islands. EcoHealth 3(4): 232-244. DOI: 10.1007/s10393-006-0059-z
Nielsen O, Nielsen K, Braun R, Kelly L
2005. A comparison of four serologic assays in screening for Brucella exposure in Hawaiian monk seals. Journal of Wildlife Diseases 41:126–133. DOI: 10.7589/0090-3558-41.1.126
West KL, Sanchez S, Rotstein D, Robertson KM, Dennison S, Levine G, Davis N, Schofield D, Potter CW, Jensen B
2013. A Longman's beaked whale (Indopacetus pacificus) strands in Maui, Hawaii, with first case of morbillivirus in the central Pacific. Marine Mammal Science, 29: 767–776. DOI: 10.1111/j.1748-7692.2012.00616.x
Yantis D, Moeller R, Braun R, Gardiner CH, Aguirre A, Dubey JP
2003. Hepatitis associated with a Sarcocystis canis-like protozoan in a Hawaiian monk seal (Monachus schauinslandi). Journal of Parasitology. 89:1258-1260. DOI: 10.1645/ge-3265rn

Parasites

Emaciated yearling from the NWHI.
Emaciated yearling from the NWHI.

The prevalence of gastrointestinal parasitic infections throughout the monk seal population is significant and the effects on monk seal morbidity and mortality are not fully known. The high rate of infection, concurrent with prey limitation in the NWHI, may be a significant factor affecting the growth and survivorship of juvenile Hawaiian monk seals in this region. Parasitic infections directly contribute to emaciation and starvation by damaging a seal's ability to digest food and absorb nutrients. When prey availability is scarce, the effects of an additional parasite load may further impair a seal's ability to effectively forage, leading to starvation while also increasing susceptibility to shark predation. Administration of deworming treatments to reduce parasite burdens in individual seals can be a valuable intervention strategy with the potential to increase growth and survivorship of the monk seal population.

Further Reading:

Baker JD
2008. Variation in the relationship between offspring size and survival provides insight into causes of mortality in Hawaiian monk seals. Endangered Species Research 5(1):55-64. DOI: 10.3354/esr00122
DeLong RL, Orr AJ, Jenkinson RS, Lyons T
2009. Treatment of northern fur seal (Callorhinus ursinus) pups with ivermectin reduces hookworm-induced mortality. Marine Mammal Science 25(4):944-948. DOI: 10.1111/j.1748-7692.2008.00274.x
Gobush KS, Baker JD, and Gulland FMD
2011. Effectiveness of an Antihelminthic Treatment in Improving the Body Condition and Survival of Hawaiian Monk Seals. Endangered Species Research 15:29-37. DOI: 10.3354/esr00364
Gobush KS, Booth RK, Wasser SK
2014. Validation and application of noninvasive glucocorticoid and thyroid hormone measures in free-ranging Hawaiian monk seals. General and Comparative Endocrinology 195: 174-182. DOI: 10.1016/j.ygcen.2013.10.020
Reif JS, Kliks MM, Aguire AA, Borjesson DL, Kashinsky L, Braun RC, Antonelis GA
2006. Gastrointestinal helminths in the Hawaiian monk seal (Monachus schauinslandi): associations with body size, hematology, and serum chemistry. Aquatic Mammals 32(2): 157-167. DOI: 10.1578/AM.32.2.2006.157

Toxins

Persistent oganic pollutants (POPs), including oganochlorine (OC) pesticides and many industrial chemicals, are associated with urban and agricultural regions. Contamination of the marine environment occurs from a variety of sources including sewage spills, urban and agricultural run-off and oil spills. Ingestion of contaminated prey ultimately results in the accumulation of POPs in monk seal tissue and blood. High POP concentrations in tissue and blood may lead to reproductive failure, immunosuppression, as well as other effects, with the potential of having a significant negative influence on monk seal survival.

Studies evaluating POP levels in NWHI and MHI seals determined that the contaminant levels of MHI seals were not higher than seals from the uninhabited NWHI. However, there were a few animals from both regions with high enough levels of POPs in their tissues to possibly have an effect on their health. These findings suggest that POPs are not a current threat to the monk seal population.

A study on the potential threat from ciguatoxins, neurotoxins produced by microalgae that accumulate in coral reef associated fish, has shown that some monk seals have significant levels of ciguatoxins in their tissues. However, it is unclear what impacts ciguatoxins have on the health of monk seals.

Efforts are ongoing and in collaboration with other researchers to understand the role of contaminants, both human introduced and naturally occurring, in monk seal vitality.

Further reading:

Bottein M-Y D, Kashinsky L, Wang Z, Littnan C, Ramsdell JS
2011. Identification of Ciguatoxins in Hawaiian Monk Seals Monachus schauinslandi from the Northwestern and Main Hawaiian Islands. Environmental Science and Technology 45(12): 5403–5409. DOI: 10.1021/es2002887
Littnan CL, Stewart BS, Yochem PK, Braun R
2006. Survey for selected pathogens and evaluation of disease risk factors for endangered Hawaiian monk seals in the main Hawaiian Islands. EcoHealth 3(4): 232-244. DOI: 10.1007/s10393-006-0059-z
Lopez J, Boyd D, Ylitalo GM, Littnan C, Pearce R
2012 Persistent organic pollutants in the endangered Hawaiian monk seal (Monachus schauinslandi) from the main Hawaiian Islands. Marine Pollution Bulletin. DOI: 10.1016/j.marpolbul.2012.07.012
Lopez J, Hyrenbach KD, Littnan C, Ylitalo GM
2014. Geographic variation of persistent organic pollutants in Hawaiian monk seals Monachus schauinslandi in the main Hawaiian Islands. Endangered Species Research 24: 249-262. DOI: 10.3354/esr00602
Ylitalo GM, Myers M, Stewart BS, Yochem PK, Braun R, Kashinsky L, Boyd D, Antonelis GA, Atkinson S, Aguirre AA, Krahn MM
2008. Organochlorine contaminants in endangered Hawaiian monk seals from four subpopulations in the Northwestern Hawaiian Islands. Marine Pollution Bulletin 56(2): 231-244. DOI: 10.1016/j.marpolbul.2007.09.034

Emergency Response

Seal with fish hook in mouth.
Seal with fish hook in mouth.

Emergency responses to address potentially life threatening situations for monk seals include removal of embedded fishhooks and entangling marine debris, treatment of sick and injured seals, and addressing aggressive human-seal interactions among other activities. Population assessment field teams conduct the majority of these response activities in the NWHI. Depending on the nature of the emergency, some seals may be treated on site while others may need to be held in temporary holding facilities at NOAA's Inouye Regional Center on Oʻahu or hospitalized at The Marine Mammal Center's monk seal hospital Ke Kai Ola on Hawaiʻi Island.