A review of fibropapillomatosis in Green turtles (Chelonia mydas)

Abstract

Despite being identified in 1938, many aspects of the pathogenesis and epidemiology of fibropapillomatosis (FP) in marine turtles are yet to be fully uncovered. Current knowledge suggests that FP is an emerging infectious disease, with the prevalence varying both spatially and temporally, even between localities in close proximity to each other. A high prevalence of FP in marine turtles has been correlated with residency in areas of reduced water quality, indicating that there is an environmental influence on disease presentation. Chelonid herpesvirus 5 (ChHV5) has been identified as the likely aetiological agent of FP. The current taxonomic position of ChHV5 is in the family Herpesviridae, subfamily Alphaherpesvirinae, genus Scutavirus. Molecular differentiation of strains has revealed that a viral variant is typically present at specific locations, even within sympatric species of marine turtles, indicating that the disease FP originates regionally. There is uncertainty surrounding the exact path of transmission and the conditions that facilitate lesion development, although recent research has identified atypical genes within the genome of ChHV5 that may play a role in pathogenesis. This review discusses emerging areas where researchers might focus and theories behind the emergence of FP globally since the 1980s, which appear to be a multi-factorial interplay between the virus, the host and environmental factors influencing disease expression.

Sea turtle fibropapilloma tumors share genomic drivers and therapeutic vulnerabilities with human cancers

“…Although ChHV5 has been associated with fibropapillomatosis and ChHV5 DNA is readily detectable within tumors 5,31 , there was an almost complete lack of viral transcripts within the RNA-seq samples, with only four ChHV5 transcripts being detected, three of which were related transcript variants (Fig. 2c, Supplementary Table 1).…”

“…The analysis revealed that there was a mild positive correlation between UVI exposure and the numbers of stranded fibropapillomatosis-afflicted turtles ( R 2  = 0.493), suggesting that UV exposure may also be a risk factor for fibropapillomatosis and a potential limiting factor accounting for the relatively slow northward spread of fibropapillomatosis. The observed level of correlation is relatively high, considering that fibropapillomatosis is a multifactorial disease with viral and other environmental factors likely contributing to disease progression 5 .

Fig. 6Putative fibropapillomatosis prevalence and ultraviolet (UV) radiation exposure link.

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The green turtle Chelonia mydas as a marine and coastal environmental sentinels: anthropogenic activities and diseases

“…Although FP occurs globally, the etiological agent and the transmission remain undetermined, but the Chelonid herpesvirus 5 (ChHV5) DNA is often detected in tumors from different sea turtle species and regions, and is the most commonly accepted agent (DOMICIANO et al, 2013;WORK et al, 2015b;JONES et al, 2016). Recently, ChHV5 DNA was also detected in saliva and ocular secretion of FP-affected C. mydas in southeastern Brazil, and added to skin contact, it represents another possible pathway for virus shedding (MONEZI et al, 2016).…”

“…Recently, ChHV5 DNA was also detected in saliva and ocular secretion of FP-affected C. mydas in southeastern Brazil, and added to skin contact, it represents another possible pathway for virus shedding (MONEZI et al, 2016). Fibropapillomatosis is associated with the life cycle of C. mydas, because tumors are observed in postrecruitment juveniles and adults in neritic areas but is absent in oceanic areas (ENE et al, 2005;JONES et al, 2016). Some environmental factors, such as high levels of contamination, water temperature and concentration of viral strains in neritic areas have been associated with FP (HERBST, 1994;SANTOS et al, 2010;RODENBUSCH et al, 2014).…”

In VitroReplication of Chelonid Herpesvirus 5 in Organotypic Skin Cultures from Hawaiian Green Turtles (Chelonia mydas)

“…Diseases have also been documented for green turtles; the most common of these is fibropapillomatosis (FP), a disease that has a global distribution (3) and causes disfiguring tumors on the skin, eyes, and mouth as well as internal tumors, mostly in the lungs, heart, and kidneys (4,5). FP has been seen in most places where green turtles range and has been studied most extensively in Hawaii, Florida, Brazil, and Australia (3,6). Severely affected turtles become immunosuppressed, septic, and emaciated and eventually die (7,8).…”