National Oceanographic and Atmospheric Administration, Hawaiian Monk Seal Research Program, Pacific Islands Fisheries Science Center, 1845 Wasp Blvd., Honolulu, Hawaii 96818, USA.
National Oceanographic and Atmospheric Administration, Wildlife Management and Conservation Branch, Pacific Islands Regional Office, 1845 Wasp Blvd., Honolulu, Hawaii 96818, USA.
J Wildl Dis. 2023 Jan 1;59(1):1-11. doi: 10.7589/JWD-D-21-00179.
Toxoplasmosis is a major threat to Hawaiian monk seals (Neomonachus schauinslandi) in the main Hawaiian Islands where seal habitat overlaps with substantial human and domestic cat populations. As the definitive hosts, members of the Felidae are the sole sources contaminating the environment with infectious oocysts; these oocysts can be transported into the marine environment, thereby threatening marine mammals. To understand environmental factors influencing Hawaiian monk seal exposure to Toxoplasma gondii, we examined monk seal strandings from toxoplasmosis in relationship to location and rainfall patterns throughout the main Hawaiian Islands. Using a case-control study design, we compared mortalities due to toxoplasmosis (cases) with those from other causes (controls). We found that cases were up to 25 times more likely than controls to occur after heavy runoff events. The greatest odds ratio was observed when rainfall occurred 3 wk before strandings, potentially indicating important timelines in the disease process. Our results suggest that heavy rainfall frequently delivers sufficient numbers of oocysts to infect Hawaiian monk seals. With infectious doses of as low as a single oocyst, any contaminated runoff constitutes a risk to Hawaii's endangered monk seal.
弓形虫病对夏威夷僧海豹（Neomonachus schauinslandi）构成了重大威胁，这些海豹的栖息地与大量的人类和家猫种群重叠。猫科动物是终末宿主，是唯一将具有传染性的卵囊污染环境的来源；这些卵囊可以被运送到海洋环境中，从而威胁到海洋哺乳动物。为了了解影响夏威夷僧海豹感染弓形虫的环境因素，我们研究了与主要夏威夷群岛的位置和降雨模式有关的弓形虫病导致的僧海豹搁浅事件。我们使用病例对照研究设计，将因弓形虫病而死亡的个体（病例）与因其他原因而死亡的个体（对照）进行了比较。我们发现，在发生大量径流事件后，病例发生的可能性比对照高 25 倍。当降雨发生在搁浅前 3 周时，观察到最大的优势比，这可能表明疾病过程中有重要的时间线。我们的研究结果表明，强降雨经常会带来足够数量的卵囊感染夏威夷僧海豹。由于感染剂量低至单个卵囊，任何受污染的径流都会对夏威夷濒危的僧海豹构成风险。
