Abstract
During a 2012 winter field trip to Granito and Angel de la Guarda islands in the Gulf of California, three California sea lions (Zalophus californianus) died suddenly during their individual capture. The animals (two adult females, one juvenile female), which appeared to be in good condition and did not show evidence of illness before capture, displayed tremors minutes after capture, before entering into cardiorespiratory arrest. Our efforts to resuscitate the sea lions were ineffectual. We performed full necropsies of the animals and collected samples for histopathology, serology, bacteriology, and molecular detection of pathogens. At gross examination, the sea lions had thick, normal-appearing blubber. They all had froth in the trachea and bronchi. One of the adult females had bilateral areas of pulmonary congestion, nematodes and enlarged regional lymph nodes. All animals had high numbers of gastrointestinal parasites with no evident associated pathology. Both adult sea lions had consolidated zones in the liver. The meninges of the juvenile sea lion were moderately hemorrhagic, and the cerebellum had foci of petechial hemorrhages. Microscopic lesions were similar among the three cases and included mild to moderate diffuse congestion in various organs. The livers of the adult females had perilobular fibrosis and moderate hyperplasia of the epithelium of the biliary ducts. The cerebellum and spinal cord were mildly congested. The myocardium and skeletal muscle showed moderate diffuse congestion and mild dissociation of fibrils. There was evident lymphocytic depletion in the spleen, and the adrenal glands showed moderate diffuse medullar congestion. The rest of the tissues examined showed no apparent changes. We were unable to find evidence of infection by Morbillivirus, Influenza, West Nile Virus, Coronavirus, Leptospira and Clostridium spp. in any of the tissues examined by PCR or RT-PCR. Both adult females had positive serum antibodies to various Leptospira serovars (1:1200). Moraxella catarhalis, Haemophilus spp. and Pasteurella multocida were isolated from the lung. The gross and microscopic lesions observed are suggestive of acute intoxication and are not typical of an infectious process that might explain the animals' sudden death. There was no evidence of algal blooms in the area near the time of the event. However, there have recently been a number of events related to drug trafficking in the area. A recent report stated that drug 'warehouses' are increasingly found in Natural Reserves.3 During the field trip we observed atypical behaviors of the entire sea lion colony, including over-excitation, increased aggression and apparent hyperacusis. Considering the results obtained from the postmortem examination, which revealed lesions compatible with acute cocaine-intoxication in humans,1,3 the uncommon behaviors observed, and the current situation regarding drug-trafficking in the area, we believe the animals may have been exposed to cocaine from packages stashed among the rocks in their colony, and that the additional stress caused by routine capture led to sudden heart failure. However, as we were unable to freeze samples, we had no way of attempting to detect cocaine metabolites in the sea lions' urine or blood. Further work will help prove or disprove our hypothesis.
* Presenting author
Literature Cited
1. Lucena J, Blanco M, Jurado R, Rio A, Salguero M, Vazquez R, Thiere G, Basso C. 2010. Cocaine-related sudden death: a prospective investigation in southeast Spain. Europ Heart J 31, 318–326.
2. Mash DC, Duge L, Pablo J, Qin Y, Adi N, Hearn WL, Hyma DA, Karch SB, David H, Wetli CV. 2009. Brain biomarkers as a cause of sudden death. Forensic Sci 190 e13–e19.
3. Milenio news. Narcos explotan areas naturales protegidas. January 6, 2013. www.milenio.com/cdb/doc/noticias2011