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audrey mcgowin, ph.d - research

The Influence of Urban Contamination on the Ozobranchus branchiatus Leech, A Probable Mechanical Vector in the Transmission of Sea Turtle Fibropapillomatosis.”

An alarming number of Florida sea turtles that forage in lagoons with poor water quality such as the Indian River Lagoon, Lake Worth, and Florida Bay have developed fibropapillomas on their skin and eyes impairing their ability to see, swim, and feed.  In addition to the epizootic at theses sites in Florida, fibropapillomatosis (FP) has become a panzootic with disease outbreaks at similar sites in Hawaii, Brazil, Puerto Rico, Australia, and others.  Fibropapilloma-associated turtle herpes virus (FPTHV) has been identified as the likely infectious agent yet many of the factors associated with disease etiology have not been discovered such as 1) how the virus is transmitted between turtles, 2) why some turtles that have been exposed to the virus develop tumors while others do not, and 3) what factors initiate tumor formation.  The only possible vector identified thus far for virus transmission is the sea turtle leech of the genus Ozobranchidae from a green turtle (Chelonia mydas) in Hawaii.  FP is a disease that appears to require several factors and conditions to flourish.  First, the turtle must acquire the virus.  Leeches may transmit the virus or the turtle may acquire FPTHV in another way through contact with an infected turtle.  Then, environmental stressors or pollutants must be present to cause immune suppression.  An injury to the skin and the formation of papillomas at the site of injury would follow.  Since FPTHV is latent virus, infection with the virus would not have to occur at the same time as initiation of tumor formation.  For instance, a turtle may acquire the virus and not suffer immune suppression until it enters a polluted lagoon.  At that time, a leech could produce the skin injury that initiates the formation of papillomas.  Alternatively, the leech could be a repository for the virus, which is transmitted to the turtle when it breaks its skin.  Either way, it is often reported that leeches are found on turtles in areas where high disease rates are observed. 

The main object of my project is to examine the potential of sea turtle leeches, Ozobranchus spp. to transmit FPTHV and/or initiate tumor formation.  Specific objectives include 1) identification of species of leeches removed from turtles with and without FP, 2) analysis of FPTHV in leeches to determine viral loads and viral variant, and 3) do a statistical analysis of FPTHV viral variant, virus concentration, leech species, host species, location, and FP status of turtle.  The leeches are very small so determining species with the naked eye is practically impossible.  In my laboratory, we developed a DNA barcode method that will be used in future work to unambiguously identify leech species, including separate haplotypes, by sequencing the COI mitochondrial gene.  Sequencing of the histone H3 gene in O. branchiatus has revealed the presence

Relevant References
McGowin AE, Truong TM, Corbett AM, Bagley DA, Ehrhart LM, Bresette MJ, Weege ST, Clark D, Genetic barcoding of marine leeches (Ozobranchus spp.) from Florida sea turtles and their divergence in host specificity, Molecular Ecology Resources,11(2): 271-278.

Lavretsky, P, Truong, TM, McGowin AE, Balazs, GH, Peters, JL, New primers reveal the presence of a duplicate histone H3 in the marine turtle leech Ozobranchus branchiatus, Conservation Genetics Resources, DOI 10.1007/s12686-011-9581-6, 2011. 

Ozobranchus margoi (ventral view)

Ozobranchus branchiatus (ventral view)

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