Abstract

Toxoplasmosis is a leading cause of mortality in endangered Hawaiian monk seals (HMS) in the main Hawaiian Islands.^1,2 Between January 1, 2020 and December 1, 2021 two adult HMS with toxoplasmosis were admitted to The Marine Mammal Center’s hospital in Kona Hawai′i. The 12-year-old adult female and 13-year-old adult male were well known individuals that primarily resided in the waters surrounding the island of O′ahu and had no history of significant illness. Both were admitted in a severely compromised state with varying degrees of neurologic impairment. Toxoplasmosis was diagnosed based on strongly positive serologic titers on admission (male: 1:10,240; female: 1:40,000). Both were treated with an aggressive regimen of multi-modal anti-protozoal therapy (ponazuril, clindamycin, trimethoprim-sulfamethoxazole), corticosteroids, antiemetics, and gastrointestinal support medications, as well as supplemental vitamin and anti-oxidant therapy. Unilateral ocular disease developed and was treated in each individual. Both individuals showed initial improvement before a decline at roughly 4 weeks in rehabilitation and both succumbed to the disease. Prior to these two individuals, all HMS with toxoplasmosis were found dead or died before treatment could be initiated. Histopathology in both indicated that cause of death was congestive right-sided heart failure, likely secondary to chronic toxoplasmosis, though protozoal treatment appeared at least partially successful in controlling tachyzoite dissemination. These cases represent the first two HMS to receive targeted, extended treatment for toxoplasmosis and lessons learned will help guide future therapies for this deadly disease.

Acknowledgements

The authors thank Dr’s Frances Gulland, Deborah Fauquier, Meghan Barrett, Ednee Yoshioka, Kate Spalding, Shawn Johnson, Carmen Colitz, and Michelle Rivard for their expertise in these cases. Special thanks goes to the animal care team Heidi Nikolai, Ashley Bell, Heather Stoker, and veterinary technician Claudia Cedillo for their expert care. The authors also thank the Hawaiian Monk Seal Research Program Staff, the O′ahu community and Hawai′i Marine Animal Response personnel that helped monitor and locate these seals in the wild, and the volunteer animal care crews at Ke Kai Ola for their dedication and diligence in caring for these monk seal patients. This work was conducted under NMFS permit 18786.

Literature Cited

1.  Harting AL, Barbieri MM, Baker JD, Mercer TA, Johanos TC, Robinson SJ, Littnan CL, Colegrove KM, Rotstein DS. 2021. Population‐level impacts of natural and anthropogenic causes‐of‐death for Hawaiian monk seals in the main Hawaiian Islands. Mar Mamm Sci 37(1):235–50.

2.  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. Dis Aquat Organ 26;121(2):85–95.