Highly divergent herpesviruses in threatened river dolphins from Brazil

Helena Exposto Novoselecki,Angélica María Sánchez-Sarmiento,Vera Maria Ferreira Da Silva,Carolina P Bertozzi,José Luiz Catão-Dias,Carlos Sacristán,Aricia Duarte-Benvenuto,Carlos G Das Neves,Vanessa Lanes Ribeiro,Fernando Esperón,Pedro Enrique Navas-Suárez,Henrique Christino Lial,Vitor L Carvalho,Miriam Marmontel,Samira Costa Silva,Rodrigo Del Rio Do Valle,Ana Carolina Ewbank,Juliana Marigo,Waleska Gravena

doi:10.1038/s41598-021-04059-0

Abstract

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America. To address the knowledge gap regarding infectious agents in this cetacean group, we surveyed the presence of herpesviruses by PCR in skin and/or blood samples of live-captured Amazon (Inia geoffrensis, n = 25) and Bolivian (Inia boliviensis, n = 22) river dolphins of the Amazon basin and in selected tissue samples of franciscanas (Pontoporia blainvillei, n = 27) stranded or bycaught in southeastern Brazil. Additionally, available franciscana tissue samples were examined by histopathology. Herpesvirus DNA was amplified in 13 Bolivian river dolphins (59.1%, 95% CI 38.5–79.6%) and 14 franciscanas (51.9%, 95% CI 33.0–70.7%). All Amazon river dolphins were herpesvirus-negative. Two different herpesviruses were found in Bolivian river dolphins: a previously known gammaherpesvirus detected in blood and/or skin samples of all positive individuals and a novel alphaherpesvirus in the skin of one animal. A new gammaherpesvirus was found in several franciscana samples—the first herpesvirus recorded in Pontoporiidae. Intranuclear inclusion bodies consistent with herpesvirus were observed in the lymph node of one franciscana. The high divergence among the obtained herpesviruses and those previously described can be explained by viral-host coevolution, and by the fact that these populations are fairly isolated.

Highlights

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America
Herpesvirus DNA was detected in 59.1% (13/22, 95% confidence interval [CI] 38.5– 79.6%) of these individuals by DNA polymerase gene (DPOL) and/or glycoprotein B (gB) PCR, including cutaneous samples from four animals and blood samples from eleven animals
The DPOL gene was amplified in 9.1% (2/22, 95% CI 0.0–21.1%) of skin samples and 55.6% (10/18, 95% CI 32.6–78.5%) of blood samples of these dolphins

Summary

Introduction

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America. The polyphyletic group “river dolphins” comprises four different odontocete families: Iniidae, Pontoporiidae, Lipotidae and Platanistidae[1,2] They are likely relict representatives of originally diverse marine taxa that precede the radiation of the Delphinidae and remained in riverine ecosystems or coastal waters (i.e., Pontoporiidae)[1]. The franciscana is a small cetacean endemic of the southwestern Atlantic Ocean, that inhabits coastal and occasionally estuarine waters from the state of Espírito Santo, southeastern Brazil (18o25′S–30o42′W) to the Chubut province, in the northern Argentinean Patagonia (42o35′S–64o48′W), with some gaps in their d istribution[19] This species is classified as Vulnerable by the IUCN Red L ist[20] and as Critically Endangered by the Brazilian Ministry of E nvironment[12]. Gastrointestinal parasites—including the acanthocephalan Polymorphus sp. and the trematodes Hadwenius pontoporiae and Synthesium pontoporiae, among others, have been r eported[36,37,38]

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