July 18, 2017

Researchers Identify Novel Avulaviruses in Antarctic Penguins

Researchers discovered 3 distinct avulaviruses in Antarctic penguins, suggesting that Antarctic penguins may carry multiple avulavirus species.

By JoAnna Pendergrass, DVM

A team of researchers recently identified 3 genetically and antigenically distinct avulaviruses in Antarctic penguins. The team’s findings, reported in the Centers for Disease Control and Prevention’s Emerging Infectious Diseases journal, “suggest that, in Antarctica, a much greater diversity of avulaviruses exists than previously recognized,” wrote the researchers.

 

Avulaviruses comprise the Avulavirus genus, which is within the Paramyxoviridae family of viruses. Avian paramyxoviruses (APMVs) affect domestic and wild birds, including turkeys, chickens, and pigeons. Outbreaks of APMVs can be economically devastating, particularly to the poultry industry.

 

Currently, 13 Avulavirus species (APMV-1 to APMV-13) have been recognized formally. Although most avulaviruses cause either mild or no clinical signs, APMV-1—the well-known and highly contagious Newcastle disease virus—can cause acute respiratory disease and diarrhea in chickens. Previous studies have reported detection of APMV-1 and several other avulaviruses in Antarctic pigeons.

 

For the current study, researchers visited 7 Antarctic locations, collecting cloacal and fecal samples from Gentoo penguins and blood samples from Adélie penguins; samples were collected during 3 scientific expeditions from 2014 to 2016. Several diagnostic tests were performed to isolate, confirm, and characterize the avulaviruses.

 

Virus Isolation

Virus isolation was successful in 12 cloacal samples from Gentoo penguins living on Antarctica’s Kopaitic Island. Five of the 12 viral isolates were positive for avulavirus RNA, demonstrated by reverse transcriptase polymerase chain reaction (PCR).

 

Genetic Characterization

The PCR-positive isolates underwent next generation sequencing, which identified genomic sequences for 3 novel avulaviruses: Antarctic penguin virus A (APVA), Antarctic penguin virus B (APVB), and Antarctic penguin virus C (APVC). These avulaviruses shared approximately 65% genome-wide nucleotide identity with each other and about 60% identity with other avulaviruses.

 

Using phylogenetics (the study of evolutionary relationships), researchers determined that APVA, APVB, and APVC share a common viral ancestor with several other APMVs, forming what’s called a monophyletic cluster.

 

These results, the researchers noted, suggest that the novel avulaviruses are genetically distinct.

 

Antigenic Characterization

To evaluate the antigenicity of the novel avulaviruses, researchers performed several hemagglutination inhibition assays (HAI), which measure an antibody’s ability to inhibit agglutination between red blood cells and a virus’s hemagglutinin protein.

 

For the first HAI, antisera of APVA, APVC, and APMVs 1–3 was tested against isolates of the novel avulaviruses; APVA and APVC antisera was generated by immunizing guinea pigs with inactivated APVA and APVC vaccines and collecting the sera 28 days post-immunization. The novel avulaviruses did not cross-react with each other or the other avulaviruses, indicating that the novel avulaviruses are antigenically distinct.

 

For the second HAI, researchers tested APVA and APVC against sera collected from Adélie penguins living on Kopaitic Island. A few serum samples reacted to APVC and one reacted to AVPA, suggesting that the novel avulaviruses can infect other Antarctic penguin species.

 

Cytopathology

Researchers inoculated specific pathogen-free embryonic chicken eggs with the novel avulavirus isolates. Cytology revealed cell rounding and detachment from the monolayer, indicating cytopathogenic changes following infection with the novel avulaviruses.

 

Looking Forward

Given the study results, the research team advocated for addition research “to evaluate the presence of these new viruses in other birds in Antarctica [and] better understand the ecology and transmission of avulavi­ruses in this pristine environment.”


 


Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.



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