Land Use, Macroalgae, and a Tumor-Forming Disease in Marine Turtles

Abstract

Wildlife diseases are an increasing concern for endangered species conservation, but their occurrence, causes, and human influences are often unknown. We analyzed 3,939 records of stranded Hawaiian green sea turtles (Chelonia mydas) over 28 years to understand fibropapillomatosis, a tumor-forming disease linked to a herpesvirus. Turtle size is a consistent risk factor and size-standardized models revealed considerable spatial and temporal variability. The disease peaked in some areas in the 1990s, in some regions rates remained constant, and elsewhere rates increased. Land use, onshore of where the turtles feed, may play a role. Elevated disease rates were clustered in watersheds with high nitrogen-footprints; an index of natural and anthropogenic factors that affect coastal eutrophication. Further analysis shows strong epidemiological links between disease rates, nitrogen-footprints, and invasive macroalgae and points to foraging ecology. These turtles now forage on invasive macroalgae, which can dominate nutrient rich waters and sequester environmental N in the amino acid arginine. Arginine is known to regulate immune activity, promote herpesviruses, and contribute to tumor formation. Our results have implications for understanding diseases in aquatic organisms, eutrophication, herpesviruses, and tumor formation.

Health condition of juvenile Chelonia mydas related to fibropapillomatosis in southeast Brazil

“…Polluted areas have a higher prevalence, suggesting that FP can be an indicator of environmental damage, and that sea turtles can be used as 'sentinel species' (Aguirre & Lutz 2004). This pollution versus FP occurrence aspect has been recently examined by associating nutrient pollution of coastal areas with high prevalence of FP in Hawaii, USA, proposing that nitrogen input to the local food web promotes higher FP prevalence by favoring alphaherpesvirus-induced tumor formation (Van Houtan et al 2010. As novel or controversial as this hypothesis may appear, given that nutrient intake is strictly related to dietary conditions, agglomerations around more eutrophic and productive feeding areas are prone to occur (Santos et al 2010.…”

Global phylogeography and evolution of chelonid fibropapilloma-associated herpesvirus

“…The most susceptible life stages appear to be neritic juveniles and subadults, whereas in adults the disease is rare (Ene et al, 2005;Herbst & Klein, 1995;Work et al, 2004). A high prevalence of FP is common in anthropogenically altered environments (Aguirre & Lutz, 2004;Herbst, 1994;Van Houtan et al, 2010), suggesting that factors in these environments promote disease outbreaks, for example, through the enhancement of virus transmissibility and/or the enhancement of disease expression via substances that…”

“…The most susceptible life stages appear to be neritic juveniles and subadults, whereas in adults the disease is rare (Ene et al, 2005;Herbst & Klein, 1995;Work et al, 2004). A high prevalence of FP is common in anthropogenically altered environments (Aguirre & Lutz, 2004;Herbst, 1994;Van Houtan et al, 2010), suggesting that factors in these environments promote disease outbreaks, for example, through the enhancement of virus transmissibility and/or the enhancement of disease expression via substances thatThe GenBank/EMBL/DDBJ accession numbers for the CFPHV sequences determined in this study are JN580279-JN580296 and JN625251-JN625262.Further details about samples are available with the online version of this paper. Phylogenies of herpesviruses typically have topologies congruent with those of their tetrapod hosts, suggesting a host-linked evolution (Davison, 2002;Firth et al, 2010;Umene & Sakaoka, 1999).…”

Characterization of fibropapillomatosis in green turtles Chelonia mydas (Cheloniidae) captured in a foraging area in southeastern Brazil

“…The high prevalence of FP in Itaipu, compared with other localities in Brazil, may be related to several environmental and biological factors as described in 'Study site', such as high nutrient pollution levels (Foley et al 2005, Santos et al 2010, Van Houtan et al 2010, 2014, chemical contaminants (Adnyana et al 1997, Silva et al 2016, water temperatures (Herbst & Klein 1995, Page-Karjian et al 2014, and the immuno logic and physiologic status of turtles (Aguirre et al 1995, Work et al 2001. Furthermore, the high density of susceptible turtles in the area may also serve as a reservoir and potential vector for infectious viruses, facilitating the transmission of the disease (Herbst & Klein 1995, Curry et al 2000.…”