Brussels, 20 May 2004
A Soviet-era research centre may hold the key to why bubonic plague has never been stamped out. Thanks to EU and international support, four decades of data is being converted into new epidemiological theories and public health models.
Dubbed the 'black death' during the famous European outbreak which killed over 25 million people in the 1300s – one-fourth of the continent's population – bubonic plague has long challenged epidemiologists and historians. Today, question marks remain as to its origins – recent evidence points to Egypt (see National Geographic) instead of the East – and how it has managed to reappear in areas where it was previously wiped out.
A unique archive of data, housed at the Kazakh Scientific Centre for Quarantine and Zoonotic Diseases in Almaty, sheds light on this lethal bacterial disease. After the break-up of the Soviet Union, the centre reportedly fell on hard times, putting at risk not only its huge data collection, but also its samples and strains of rogue bacteria, including anthrax, cholera and plague.
The European Union and the International Science and Technology Centre backed a four-year epidemiological study (Stepica) of plague in central Asia, led by the University of Oslo's (NO) department of biology. The project, funded through the Union's Fifth Framework Programme (FP5) for research, comprises 11 research laboratories in nine European and central Asian countries, and is in its final year.
The English nursery rhyme 'Ring-a-ring o'roses' is traced to the plague's rose-coloured lesions and deadly spread. Although largely stamped out in Western society, minor outbreaks still occur elsewhere. Scientists are intrigued as to how the disease evolves and is transmitted – which is where the data archive comes in. In Kazakhstan and neighbouring countries, the main culprit is the 'great gerbil', a native rodent whose numbers appear to relate to the occurrence of plague.
Models based on the extensive data from the region show that the prevalence of plague-infected fleas rises and falls largely in step with the gerbil numbers, reports the latest issue of Science. Under the title 'Plague annals help bring microbe lab in from the cold', the article goes on to mention the importance of this body of knowledge in eventually predicting future outbreaks and implementing countermeasures.
Stepica's coordinator Nils C Stenseth is upbeat about the research, telling Science that the Kazakh cache of information holds enormous potential for public health studies, helping scientists understand more about vector-borne diseases, such as plague, but also newer enemies like bird flu and even SARS. The added attention and funding should also secure the quarantine centre's future, as well as preventing its potentially lethal stocks from getting into the wrong hands.
A follow-up study will complete the puzzle: why does the plague bacterium retreat when gerbil numbers drop? Theories vary, but some scientists think it forms spores like anthrax which lay dormant until host populations bounce back, while others say it lingers in an almost hidden state. Stepica are looking into a third possibility, that plague disappears locally between the occasional outbreak but re-emerges when fleas from migrating animals, including birds, jump over to native gerbils.