Detection of Mycoplasma spp., herpesviruses, topiviruses, and ferlaviruses in samples from chelonians in Europe

Abstract

We tested samples from 1,015 chelonians in Europe for Mycoplasma spp., herpesviruses, ranaviruses, picornaviruses, and ferlaviruses by PCR. Mycoplasma spp. were detected in 42.1% and herpesviruses were detected in 8.0% of tested chelonians. Differentiation of the herpesviruses revealed that 46.9% of the detected chelonian viruses were testudinid herpesvirus 1 (TeHV-1) and 54.3% were TeHV-3, including co-detections of TeHV-1 and -3 in 3 tortoises. TeHV-4 was detected in a leopard tortoise ( Stigmochelys pardalis), and a herpesvirus that could not be further characterized was found in a pond slider ( Trachemys scripta). Picornaviruses (topiviruses) were detected in 2.2% of the tested animals; ferlaviruses were found in 0.6%; no ranaviruses were detected in any of the animals tested. Mycoplasma spp. were detected significantly more often in Horsfield's tortoises ( Testudo horsfieldii), leopard tortoises, and Indian star tortoises ( Geochelone elegans) than in other species. Horsfield's tortoises were also significantly more often positive for TeHV-1. Mycoplasma and TeHV-1 were co-detected in 3.0%, and mycoplasma and TeHV-3 in 2.3%. The TeHV-4-positive tortoise was also positive for mycoplasma. Mycoplasma and picornaviruses were co-detected in 1.2% of the tortoises. A spur-thighed tortoise ( Testudo graeca) was positive for mycoplasma and a ferlavirus. In some cases, >2 pathogens were detected. A significant correlation between mycoplasma and herpesvirus detection was found. Of all tested animals, 47.6% were positive for at least one pathogen, demonstrating the importance of pathogen detection in captive chelonians.

Investigations on the prevalence of tortoise picorna-virus in captive tortoises in Germany

“…The results from our study support the data of previous studies: the highest number of ToPV-positive animals are detected in T. graeca. However, the prevalence in Germany was higher than in previous studies conducted throughout Europe (10). This may result from the wider range of tested flocks.…”

“…Breeders in Germany have contact to other breeders, and animals are bred and sold, so the distribution of potentially sick/virus positive animals is likely to encompass the whole of Europe. Additionally, we tested several animals in each collection, other than in the investigations in Europe, where either samples in routine diagnostics of various owners, or animals in field studies were tested (10,13). We also support the potential role of the virus in shell softening in juvenile T. graeca, as all positive juveniles from a positive breeding pair showed clinical signs of the disease.…”

“…ToPV was thought to be a causative agent in the clinical pattern of soft carapace and plastron, but was also isolated in healthy tortoises in previous studies, for routine survey on chelonian viruses (10,(12)(13)(14)(15). Heuser et al (6) isolated the virus from different species but only T. graeca and one Geochelone elegans individual demonstrated clinical signs, whereas other species showed normal development but also showed seroconversion.…”

“…In August 2017, ToPV was classified as Torchivirus by the International Committee on Taxonomy of Viruses (ICTV) (8). Recent investigations consider genetic variability in detected ToPV (10,13). The present study focuses on the prevalence of ToPV in tortoise collections in Germany, since previous work focused on only one collection.…”

Peer Review #1 of "Ranaviruses and reptiles (v0.2)"

“…Epidemiological surveys must be adequately designed and powered to ensure ranavirus prevalence is accurately reported (Gray et al, 2015). There have been several studies reporting the negative results of epidemiological surveys (Hanlon et al, 2016;Kolesnik et al, 2017;Winzeler et al, 2018). These results are extremely valuable as they also help describe the distribution and emergence patterns of reptilian ranaviruses; however, it is important to consider the sampling protocols and diagnostic choice when evaluating and comparing epidemiological studies (Gray et al, 2015).…”