Health assessments uncover novel viral sequences in five species of Galapagos tortoises

Abstract

Emerging infectious diseases (EIDs) have been reported as causes of morbidity and mortality in free-living animal populations, including turtles and tortoises, and they have even resulted in species extinctions, with human activities contributing to the spread of many of these diseases. In the Galapagos, giant tortoises are endangered due to habitat change, invasive species, and other human impacts; however, the impact of EIDs on Galapagos tortoise conservation remains understudied. To fill this gap, we conducted health assessments of five tortoise species from the islands of Santa Cruz, Isabela and Española. We performed health evaluations of 454 animals and PCR testing for pathogens known to be relevant in other tortoise species. We identified two novel sequences of adenoviruses and four of herpesviruses. Based on alignments of the DNA polymerase gene and maximum likelihood phylogenetic analyses, we found both novel adenoviruses to be most closely related to red footed tortoise adenovirus 2, by nucleotide sequence and red footed tortoise adenovirus 1, based on amino acid sequence. Three of the herpesvirus sequences translated into the same deduced amino acid sequence; therefore, they may be considered the same viral species, closely related to terrapene herpesvirus 2. The fourth herpesvirus sequence was highly divergent from any sequence previously detected and is related to an eagle owl herpesvirus based on nucleotide sequence and to loggerhead oro-cutaneous herpesvirus based on amino acids. These novel viruses may be pathogenic for giant tortoises under specific conditions (e.g., stress). Continued screening is crucial to determine if these viruses play a role in tortoise fitness, morbidity and survival. This information allows us to provide recommendations to the Galapagos National Park Directorate and other institutions to improve the management of these unique species both in Galapagos and globally, and for tortoise reintroduction plans throughout the archipelago.

Keywords: Chelonoidis spp; adenovirus; conservation medicine; herpesvirus; wildlife surveillance.