Abstract

Urogenital cancer (UGC) is a disease that is known to affect California sea lions (Zalophus californianus) since the 80s.⁴ Currently, approximately 18% of dead animals stranded on the US Pacific coast, and that are examined at necropsy, have UGC,⁶ but little is known about the prevalence of this disease in natural populations along the species distribution. We investigated the presence of OtHV-1 and beta hemolytic streptococci, previously associated with pathogenic UGC,^8,7 and recorded the occurrence of cytological abnormalities in the reproductive tract of California sea lions from the Gulf of California, Mexico. During three trips to the Gulf of California between January and October 2012, we captured 60 sea lions (3 adult females and 57 pups) at Granito rookery. Cytological brushes were used to collect genital epithelial samples and we conducted molecular and cytological analyses on the specimens. Total DNA was extracted from the brushes and we used PCR to amplify a 200 bp fragment of the OtHV-1 Dpol gene⁹ and a 458 bp fragment of the 16S ribosomal gene of beta-hemolytic streptococci. Cell smears were stained with a modified Papanicolaou method. OtHV-1 was found in 6.6% of the samples while 65% were positive for beta-hemolytic streptococci. We found 17 cell types with characteristic morphology, including koilocytes, binucleated cells and cells with absence of chromatin, which are typical traits of pre-cancerous cells. Normal cells were observed in 80% of the smears, but koilocytes and binucleated cells were a common finding (46.6%), as were the presence of enlarged nuclei (86.6%) and pyknosis (66.6%). The absence of chromatin was less common, occurring only in 6.6% of samples, and some intracellular inclusions were observed (13.33%). Other findings included presence of cytoplasmic vacuoles (66.6%), pleomorphic cells (53.3%), nuclear fragmentation (26.6%), and cell lysis (80%). A high percentage of smears had erythrocytes (80%), polymorphonuclear leukocytes (80%), fungal spores (40%), and fissured cells (46.6%). Many of the epithelial abnormalities observed are associated with cancer processes in humans⁵ and were found in 50% of the samples that were positive to OtHV-1, although the linkage between both was not significant (Fisher exact test, p > 0.05). Our results suggest that i) the prevalence of OtHV-1 in California sea lions from Granito rookery is similar to what has been reported for animals from US waters, and ii) genital epithelial cell-transformation is a common occurrence in the California sea lion, although to date there has been no reported case of UGC in the region. It is likely that other factors are related to the cellular abnormalities described, plausibly the beta-hemolytic streptococci found at a high prevalence. Genetic factors such as heterozygosity and specific MHC-II alleles have been associated with the development of UGC,^1,3 but marked genetic differences between colonies from the US and the Gulf of California have not been reported^2,3. However, concentrations of organochlorine pesticides, also linked correlatively to UGC, in the Gulf of California are lower than those reported for the California coastline.¹⁰ Future studies will allow us to address these potential links further.

* Presenting author

Literature Cited

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