Detection of Chelonid alphaherpesvirus-5 (ChHV5) in blood and organs of Chelonia mydas (Testudines, Cheloniidae) and correlation with morphometrics in animals with and without fibropapillomatosis in the coast of Ubatuba/São Paulo

Author(s)

Isabela Santos Silva

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2019-08-26

Examining board members

Eliana Reiko Matushima; Marco Aurélio Gattamorta; Silmara Rossi

• Advisor: Eliana Reiko Matushima

Abstract

Fibropapillomatosis (PF) is a neoplastic disease with epithelial origin characterized by skin tumors, and has been reported to affect all species of sea turtles. Green sea turtles (Chelonia mydas) are the most commonly and severely afflicted with fibropapillomatosis. The pathogenesis of the disease is not fully elucidated yet, however is a consensus in the literature that it has a multifactorial character. Chelonid alphaherpesvirus-5 (ChHV5) is indicated as an etiological agent of PF, since several molecular studies have shown the detection of this virus in samples from cutaneous neoformations. How spread and dissemination of ChHV 5 occurrence in animals is not one that is fully understood. The present study aim to detect ChHV5 in samples of Chelonia mydas affected and not affected by PF, from the feeding area of Ubatuba-SP and surroundings. ChHV5 detection as well as molecular characterization of the agent were done through polymerase chain reaction (PCR) and sequencing techniques. Samples were collected from 70 live animals - blood (n = 70), skin (n = 20) and tumor (n = 9) and 33 of necropsied animals: liver (n = 33), spleen (n = 32), gonads (n = 32), lungs (n = 6) and skin (= 6). The prevalence of ChHV5 was 80% (16/20) in live animals - : skin, blood and tumor (when present) and 100% (33/33) of the necropsied animals. Virus was detected in all types of tissues evaluated, and in turtles affected and not affected by PF. Considering the severity of PF was not possible to relate a direct response between that and the body condition of evaluated animals. Animals affected with severe SPF had the viral agent detected in all organs and tissues evaluated, characterizing this type of event as virus spreaders. Detection of ChHV5 in internal organs indicates local possibilities of viral persistence, specifically in gonads of animal without tumors which suggests the hypothesis of a sexual or vertical transmission of ChHV5, as it happens with other alphaherpesviruses. The quality of the water in Ubatuba beaches - where samples were collected - was analyzed and showed that some areas are more affected than others considering pollution levels. However, it is not possible set the difference between some of the parameters analyzed and the disease occurrence. ChHV5 DNA polymerase sequences from blood and tumor samples identified in this study had 100% identity with sequences from Ubatuba/SP. Thus, the same haplotype of the viral agent appears to be able to infect different host tissues. Moreover, the sequence obtained from an ovary sample in this study was compatible with a sequence found in Fernando de Noronha/PE. Thus, animals found on the North Coast of São Paulo may be infected by more than one viral haplotype and appear to be able to carry the virus between distant regions. Results of this study allow to formulate hypotheses that can contribute to the understanding of problems related to the disease pathogenesis and help in the monitoring of the viral agent, thus contributing to the control of sea turtles. (AU)

• FAPESP's process: 17/23309-8 - Detection of Chelonid Herpesvirus(ChHV-5) in blood and organs of Chelonia mydas (Testudines, Cheloniidae) and correlation with morphometrics in animals with and without fibropapillomatosis in the coast of Ubatuba/São Paulo
• Grantee: Isabela Santos Silva
• Support Opportunities: Scholarships in Brazil - Master