Transplacental toxoplasmosis in a wild southern sea otter (Enhydra lutris nereis) Melissa Miller a, * , Patricia Conrad b , E.R. James d , Andrea Packham b , Sharon Toy-Choutka a , Michael J. Murray c , David Jessup a , Michael Grigg d a California Department of Fish and Game-Office of Spill Prevention and Response, Marine Wildlife Veterinary Care and Research Center, 1451 Shaffer Road, Santa Cruz, CA 95060, United States b Department of Pathology, Microbiology and Immunology, 1 Garrod Drive, School of Veterinary Medicine, University of California, Davis, CA 95616, United States c Monterey Bay Aquarium, 886 Cannery Row, Monterey, CA 93940, United States d Molecular Parasitology Unit, Laboratory of Parasitic Diseases, National Institutes of Allergy and Infectious Diseases, 4 Center Drive, Room B1-06, National Institutes of Health, Bethesda, MD 20892-0425, United States Received 30 September 2007; received in revised form 29 December 2007; accepted 8 January 2008 Abstract In September 2004, a neonatal sea otter pup was found alive on the beach in northern Monterey Bay, CA. Efforts to locate the mother were unsuccessful. Due to a poor prognosis for successful rehabilitation, the pup was euthanized. Postmortem examination revealed emaciation, systemic lymphadenopathy and a malformation of the left cerebral temporal lobe. On histopathology, free tachyzoites and tissue cysts compatible with Toxoplasma gondii were observed in the brain, heart, thymus, liver, lymph nodes and peri-umbilical adipose. The presence of T. gondii within host tissues was associated with lymphoplasmacytic inflammation and tissue necrosis. Immunofluorescent antibody tests using postmortem serum were positive for anti-T. gondii IgM and IgG (at 1:320 and 1:1280 serum dilution, respectively), but were negative for IgG directed against Sarcocystis neurona and Neospora caninum (<1:40 each). Brain immunohistochemistry revealed positive staining for tachyzoites and tissue cysts using antiserum raised to T. gondii, but not S. neurona or N. caninum. T. gondii parasite DNA was obtained from extracts of brain and muscle by PCR amplification using the diagnostic B1 locus. Restriction enzyme digestion followed by gel electrophoresis and DNA sequencing confirmed the presence of Type X T. gondii, the strain identified in the majority of southern sea otter infections. # 2008 Elsevier B.V. All rights reserved. Keywords: Toxoplasma gondii; Sea otter; Enhydra lutris; Transplacental; Genotype X; Congenital brain malformation 1. Introduction Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii is an important cause of morbidity and mortality in humans and terrestrial animals (Tenter et al., 2000). In these species, transplacental transmis- sion of T. gondii, especially if occurring during early gestation, may result in placentitis, embryonic death, stillbirth, abortion, congenital malformations or post- natal blindness and retardation (Dubey and Beattie, 1988; Dubey, 1993; Tenter et al., 2000). Increasing recognition of T. gondii as a waterborne pathogen traced to drinking water raises concerns for risks to pregnant women and their unborn fetuses (Benenson et al., 1982; Bowie et al., 1997; de Moura et al., 2006; Heukelbach www.elsevier.com/locate/vetpar Available online at www.sciencedirect.com Veterinary Parasitology 153 (2008) 12–18 * Corresponding author. Tel.: +1 831 469 1746; fax: +1 831 469 1723. E-mail address: mmiller@ospr.dfg.ca.gov (M. Miller). 0304-4017/$ – see front matter. # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2008.01.015