Detection of Toxoplasma gondii (Types I, II, III and 12) and Sarcocystis spp. in the brains of river otter (Lontra canadensis) from Alberta, Canada

<i>Toxoplasma gondii</i> and <i>Sarcocystis</i> spp. are globally distributed coccidian parasites infecting endothermic vertebrates. <i>Toxoplasma gondii</i> is zoonotic, with widespread global prevalence in humans, domestic animals, and wildlife. <i>Sarcocystis</i> is a related and diverse genus, with species that use a range of definitive and intermediate hosts. In intermediate hosts, these tissue dwelling coccidians can be asymptomatic or cause disease through neural, hepatic, and transplacental infections. Semiaquatic mammals such as the North American river otter (<i>Lontra canadensis</i>) are at high risk of exposure to <i>T. gondii</i> and <i>Sarcocystis</i> spp. due to terrestrial runoff into freshwater environments. Their high trophic position and dual habitat use make them excellent sentinel species to monitor the presence of food and waterborne pathogens in ecosystems. Brain tissue was sampled from 89 river otters in Alberta, Canada. DNA of <i>T. gondii</i> was detected in 34 % of otters using magnetic capture sequence-specific DNA extraction and qPCR. Genotypes of <i>T. gondii</i> were identified using nested PCR and sequencing of the GRA6 and SAG2 genes, and included the most common clonal lineages in North America, Types I, II, and III, as well as Type-12 (X/A), which is highly pathogenic in sea otters. DNA of <i>Sarcocystis</i> spp. was detected in brain lysates of 30 % of otters via conventional PCR with primers targeting ITS1 and 18S ribosomal regions, and sequencing revealed <i>S. lutrae</i> and a species most closely related to, but distinct from, <i>S. kitikmeotensis</i>. This study suggests that river otters are exposed trophically to <i>T. gondii</i> shed by felids<i>,</i> and at least 2 species of <i>Sarcocystis</i> shed by unknown definitive hosts<i>.</i> Highly pathogenic <i>S. neurona</i> was not detected in this population, likely reflecting the absence of possum definitive hosts in northern Canada. The potential effects of <i>T. gondii</i> and <i>Sarcocystis</i> spp. on behaviour, health, and reproduction of river otters warrant further investigation.