From Poo to Papillomavirus: Peculiar Penguin Pathogens
Posted on June 24, 2014 by Jon Fuhrmann
Penguin poo has seen a surprising range of scientific applications, from a comprehensive census of emperor penguins from satellite data to a calculation of the rectal pressures required to avoid defecating into their own nests; the latter research, unsurprisingly, even won the 2005 Ig Nobel Prize in fluid dynamics.
More recently, the droppings of Adélie penguins were studied from a different angle in research published in the Journal of General Virology. Dr Arvind Varsani, a virologist at the University of Canterbury in Christchurch, New Zealand, isolated a previously unknown species of virus from these droppings and produced the first fully identified genome of any penguin-associated virus.
So far, we have only scratched the surface of the world of viruses. While we are aware of a significant proportion of mammal and reptile species, we only know an estimated 1% of all virus species – and within this 1%, most research focuses on viruses that cause disease in humans, certain animals and plants. The new virus Dr Varsani and his team discovered in the Adélie droppings is a species of papillomavirus. This is a large family of more than 270 virus types, over 160 of which infect humans; some of them are benign, while others can cause warts on various parts of the body or even cause cancer. The remaining 100-odd strains are found in a wide variety of animals – mostly mammals and a handful of reptiles. However, the Adélie papillomavirus is only the fourth species known associated with birds.
Dr Varsani and colleagues sampled penguin poo at Cape Crozier, in the Antarctic – home to the largest Adélie penguin colony. Adélie penguins forage in waters overlying the Antarctic continental shelf and slope, and live much further south than most other penguin species. Standing just 1.5 to 2 feet tall, Adélies can migrate up to 10,000 miles every year, in part riding the sea ice as it circulates during the winter. At Cape Crozier, near the American McMurdo station, the team observed some 270,000 breeding pairs of Adélie penguins that make up one of the southernmost of all penguin colonies on Earth.
In contrast to most Antarctic fieldwork, the logistics of Adélie poo collection were relatively simple. From McMurdo Station, the researchers were flown by helicopter to their field site on the slopes of a dormant volcano ominously named Mount Terror. Their toolkit consisted of two 1m2 wooden frames supporting stainless steel mesh cloth that holds any solid material but allows moisture to percolate through. The team placed these trays in the centre of the penguins’ nesting area, and the Adélies built their simple pebble nests on them. As a result, both adults and chicks defecated on the trays repeatedly over the course of the breeding season, which lasts from late October through January.
Contamination of the “poo trays” with non-penguin droppings was highly unlikely: the south polar skua is the only other bird species that lives nearby. Skuas prey on vulnerable penguin chicks and eggs, so the Adélies attack them on sight. This means that skuas nest some distance away and hover above the colony only briefly before darting in to try to snatch a chick, making very low the likelihood of them defecating into the trays.
In the last few years a large number of new papillomaviruses have been discovered both in humans and animals, particularly following the advent of next-generation DNA sequencing techniques. However, the papillomavirus Varsani and his colleagues identified in Adélies is just the second animal-based genome of any Antarctic virus to be sequenced. It is most closely related to the three other papillomaviruses that have been identified in birds – the African grey parrot, Common chaffinch and Yellow-necked Francolin. Since none of the Adélies observed at Cape Crozier exhibited the skin carcinomas, warts or tumours that are often associated with papillomaviruses, the researchers surmise that the virus may infect the penguins’ cloacas, rendering its symptoms outwardly invisible. Little is known about its epidemiology, and studying how the virus spreads and its impacts remains a subject for further research.
For most people who have the opportunity to travel to Antarctica, their time on the Frozen Continent is an unforgettable experience. This is certainly true for Dr Varsani, who says that the cold and difficult conditions were just another fieldwork challenge, rather than something to discourage him. For someone who specialises in the discovery of new virus species, fieldwork in exotic or unusual places is the norm. Indeed, viruses can be found in the most unexpected places – one theory even suggests that they are passed on along the food chain. With the Antarctic, for now, being something of a terra incognita in terms of virology, Dr Varsani and his collaborators are looking forward to a plethora of virus discoveries there in the coming years.
Ramet J, van Esso D, Meszner Z, & European Academy of Paediatrics Scientific Working Group on Vaccination (2011). Position paper–HPV and the primary prevention of cancer; improving vaccine uptake by paediatricians. European Journal of Pediatrics, 170 (3), 309-21 PMID: 20686784
Varsani A, Kraberger S, Jennings S, Porzig EL, Julian L, Massaro M, Pollard A, Ballard G, & Ainley DG (2014). A novel papillomavirus in Adélie penguin (Pygoscelis adeliae) faeces sampled at the Cape Crozier colony, Antarctica. The Journal of General Virology, 95 (Pt 6), 1352-65 PMID: 24686913