Highly divergent herpesviruses in threatened river dolphins from Brazil

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.

Survey of selected viral agents (herpesvirus, adenovirus and hepatitis E virus) in liver and lung samples of cetaceans, Brazil

“…The DPOL and gB herpesvirus gammaherpesvirus sequences detected in the four novel franciscana cases were 100% identical to those previously identified by Exposto Novoselecki et al 34 in franciscanas from São Paulo state, Brazil. In our animals, 3 gB sequences were found in liver and 1 DPOL and 2 gB sequences were detected in lung.…”

“…Interestingly, the family Pontoporiidae (which comprises only one species, the franciscana) presented a significantly higher number of herpesvirus-positive individuals (p = 0.02) and of herpesvirus-positive liver samples when compared to Delphinidae included in the study. A previous article in this species that tested more tissues per individual also found a higher prevalence (14/27, 51.9%) 34 -some of these animals were also included in our www.nature.com/scientificreports/ study. The reason for such high value in this threatened family-classified as Vulnerable by the IUCN Red List and as Critically Endangered by the Red Book of the Brazilian Fauna Threatened of Extinction 55,56 -is unknown, and the drivers should be identified.…”

“…To the authors' knowledge, this is the largest study on herpesviruses in cetaceans of South America, a region with only a few herpesvirus descriptions in odontocetes-all of them in Brazil 32,34,44,45 . The herpesvirus overall prevalence (8.7%, 19/218) was similar to those described in cetaceans from the coast of Portugal (7.8%, 14/179) 46 , but apparently lower than the ones described in Ziphiidae of the Canary Islands in Spain (14.5%, 8/55) 47 and in Delphinidae of the Spanish Cantabrian coast (78.6%, 11/14) 33 , which analyzed several tissue types by animal with the same DPOL PCR protocol used in the present study.…”

“…Gammaherpesvirus. Overall, 6% (13/218) of the cases presented gammaherpesviruses in liver and/or lung samples, i.e., six franciscanas previously published by Exposto Novoselecki et al 34 , another four novel franciscana cases (MM525, ii94246, ii126142, and ii160187), a pygmy sperm whale (ii179266), an Atlantic spotted dolphin (ii213578) and a Guiana dolphin (ii137962) (Table 2). Additionally, another Atlantic spotted dolphin (ii230353) presented a gammaherpesvirus, but only in kidney.…”

“…Moreover, a novel polyomavirus has been associated with thracheobronchitis in a common dolphin (Delphinus delphis) 30 , and alphaherpesviruses were linked to interstitial pneumonia in common bottlenose dolphins 31 . Additionally, alpha-and gammaherpesviruses have been molecularly detected in lung samples of animals with respiratory disease, even though an etiological relationship has not been established yet [32][33][34][35] . Other viruses (e.g., Avian influenza virus, coronavirus, parainfluenza virus, and adenovirus) able to cause respiratory disease in mammals have also been described in cetaceans, although without associated respiratory lesions 19,[22][23][24]36 .…”