Necropsy and histology at the Leibniz Institute for Zoo and Wildlife Research suggested the cause was encephalitis most likely due to viral infection. After one of the most intensive investigations in veterinary history for a single animal, utilising state-of-the-art pathological techniques and high-throughput next-generation molecular sequencing methods, the conclusions of the investigations are presented.
Polar bear Knut as dermoplastic in the Museum für Naturkunde in Berlin, Germany.
Keeping wild animals is an important component of the mission of zoos to educate the public and preserve endangered species. When animals die, tracking the potential cause becomes an investigation of pathogens from around the world. This is because zoo animals are not only potentially exposed to pathogens occurring where the zoo is located, but also to those pathogens harboured by other zoo animals. In other words: the diagnostic challenge is enormous.
In the case of Knut, researchers from the Leibniz Institute for Zoo and Wildlife Research Berlin (IZW), the Freie Universität Berlin, the Friedrich Loeffler Institute – Insel Riems, the Max Delbrück Center for Molecular Medicine in Berlin, the University of California at San Francisco and many others combined their efforts to investigate Knut’s death. Classical pathological, bacteriological, serological, molecular, histological and electron microscopical methods were combined with high throughput microarray and next generation sequencing methods to undertake the most extensive and exhaustive evaluation of the cause of death of any zoo animal to date. The necropsy was headed at the IZW by Dr Claudia Szentiks of the Department of Wildlife Diseases.
“After a detailed necropsy and histology that took several intense days to perform, the results clearly suggested that the underlying cause of Knut’s seizures was a result of encephalitis, most likely of viral origin” says Dr Szentiks.
Encephalitis can be caused by a large number of viruses, bacteria and parasites, and identifying novel pathogens in wild animals is a huge and often insurmountable challenge. In the case of Knut, the team screened gene sequences from plausible causative pathogens from tens of millions of individual DNA sequences.
“The sheer number of experiments undertaken and the sorting of results by many of the top diagnostics groups in Germany and beyond was extremely time consuming but also informative as to what we can and cannot do with current technologies. Many new directions for improvements and novel developments should come from this”, says Professor Alex Greenwood, head of the Department of Wildlife Diseases of the IZW. Although frequently suspected by many to be the likely culprit, the equine herpesviruses found in other polar bears in Germany and elsehwere was not responsible. The analysis of Knut also revealed a novel group of bear retroviruses whose presence was not related to his death. The only pathogen Knut seemed to have been exposed was an influenza A virus, as suggested by the detection of antibodies in his blood. However, it remains unclear and relatively unlikely that the flu was responsible for his death since the actual virus (in the form of viral RNA) could not be detected in his brain.
“After so much hard work, the results appear ultimately sobering. We cannot and therefore should not blame influenza as the source of death” stated Professor Klaus Osterrieder, holder of the chair for Veterinary Virology at the Freie Universität Berlin.
The results illustrate that while great strides in diagnostics have been made over the last decade, wildlife diseases present unique challenges because less is currently known than remains unknown about them. As a case in point, the research on Knut led to the discovery that a herpesvirus of zebras is able to kill polar bears as documented in the Wuppertal Zoo, infecting Knut’s father Lars, who survived the infection, and his partner, Jerka, who died from the infection. This was a surprising result that has developed into an intensive project on herpesvirus transmission in endangered zoo animals.
“It would have been impossible to check for all the suggested culprits without the support by the zoo community which willingly supplied samples from other animals for comparative purposes. This was exemplary. Although it will not help Knut any more, or other bears in the past, because of the new knowledge on pathogens in polar bears the zoos can now begin to develop management strategies to minimise their occurrence”, commented Professor Heribert Hofer, head of the IZW.Contact:
Mayer J, Tsangaras K, Heeger F, Avila-Arcos M, Stenglein MD, Chen W, Sun W, Mazzoni CJ, Osterrieder N, Greenwood AD (2013): A novel endogenous betaretrovirus group characterized from polar bears (Ursus maritimus) and giant pandas (Ailuropoda melanoleuca). Virology 443, 1-10. doi: 10.1016/j.virol.2013.05.008.
Greenwood AD, Tsangaras K, Ho SYW, Szentiks CA, Nikolin VM, Ma G, Damiani A, East ML, Lawrenz A, Hofer H, Osterrieder N (2012): A potentially fatal mix of herpes in zoos. Current Biology 22, 1727-1731. http://dx.doi.org/10.1016/j.cub.2012.07.035.
The Leibniz Institute for Zoo and Wildlife Research (IZW) investigates the vitality and adaptability of wildlife populations in mammalian and avian species of outstanding ecological interest that face anthropogenic challenges. It studies the adaptive value of traits in the life cycle of wildlife, wildlife diseases and clarifies the biological basis and development of methods for the protection of threatened species. Such knowledge is a precondition for a scientifically based approach to conservation and for the development of concepts for the ecologically sustainable use of natural resources. The IZW is member of the Forschungsverbund Berlin e.V.
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences