Gene expression changes with tumor disease and leech parasitism in the juvenile green sea turtle skin transcriptome.

Emerging infectious diseases are a major threat to biodiversity in the 21st century. Fibropapillomatosis (FP) is an epithelial tumor disease that affects immature and adult marine turtles worldwide, particularly green turtles (Chelonia mydas). We know little about the host factors contributing to FP susceptibility, in part because transcriptomic studies that compare transcript expression in turtles with and without FP are lacking. Here, we performed RNA-Seq on healthy skin tissue from immature C. mydas in the Indian River Lagoon, Florida, USA, comparing turtles (1) with and without FP and (2) with and without leech parasites, a putative vector of FP. We assembled a de novo C. mydas skin transcriptome to identify transcripts with significant differential expression (DE) across FP and leech categories. Significant DE transcripts were found across FP and leech comparisons, including 10 of the same transcripts with DE across both comparisons. Leech-positive individuals significantly upregulated different immune and viral interaction transcripts than did leech-negative individuals, including viral interaction transcripts associated with herpesvirus interactions. This finding strengthens the role of marine leeches as mechanical vectors of Chelonid herpesvirus 5 (ChHV5) which has been implicated as a causative agent of FP. FP-positive turtles upregulated several tumor progression and suppression transcripts relative to FP-negative turtles, which had no significant DE tumor progression transcripts. FP-positive turtles also upregulated significantly more protein interaction transcripts than FP-negative turtles. DE transcripts across leech comparisons showed no functional enrichment, whereas DE transcripts across FP comparisons showed some GO terms were enriched in FP-positive and FP negative turtles. Notably, only FP-negative turtles were enriched for GO terms involved in acquired and inflammatory immune gene regulation. Overall, our DE transcripts included several candidate genes that may play important roles in C. mydas resistance to or recovery from FP, highlighting that transcriptomics provides a promising venue to understand this impactful disease. Continued investigation of C. mydas responses to FP and leech affliction is imperative for species persistence and the conservation of marine ecosystems worldwide due to the essential role of sea turtles in ecosystem function and stability.

Detection of Infectious Pancreatic Necrosis Virus from the Leeches Hemiclepsis marginata and Hirudo medicinalis.

Leeches have been reported to harbor several important fish pathogens, including spring viremia of carp virus, infectious hematopoietic necrosis virus (IHNV), and viral hemorrhagic septicemia virus (VHSV), and also may contain blood protozoa. In the present study, leeches were collected from water bodies located in Kurdistan province, Iran. The specimens were tested for IHNV, VHSV, and infectious pancreatic necrosis virus (IPNV) using the PCR method. The results showed that two different species of leeches, Hemiclepsis marginata and Hirudo medicinalis, were infected by IPNV among the seven species studied. The infected leeches were found in areas that were polluted with untreated sewage coming from upstream fish farms culturing Rainbow Trout Oncorhynchus mykiss. In addition, the fish at fish farms in the vicinity had been infected with IPNV 9 months previously. Our results showed that the virus causing infectious pancreatic necrosis is present in the leeches H. marginata and H. medicinalis, suggesting that leeches are a potential source of IPNV in fish farms. Received October 14, 2015; accepted June 1, 2016.

The Ozobranchus leech is a candidate mechanical vector for the fibropapilloma-associated turtle herpesvirus found latently infecting skin tumors on Hawaiian green turtles (Chelonia mydas).

Fibropapillomatosis (FP) of marine turtles is a neoplastic disease of ecological concern. A fibropapilloma-associated turtle herpesvirus (FPTHV) is consistently present, usually at loads exceeding one virus copy per tumor cell. DNA from an array of parasites of green turtles (Chelonia mydas) was examined with quantitative PCR (qPCR) to determine whether any carried viral loads are sufficient to implicate them as vectors for FPTHV. Marine leeches (Ozobranchus spp.) were found to carry high viral DNA loads; some samples approached 10 million copies per leech. Isopycnic sucrose density gradient/qPCR analysis confirmed that some of these copies were associated with particles of the density of enveloped viruses. The data implicate the marine leech Ozobranchus as a mechanical vector for FPTHV. Quantitative RT-PCR analysis of FPTHV gene expression indicated that most of the FPTHV copies in a fibropapilloma have restricted DNA polymerase expression, suggestive of latent infection.