An article by Clement and Colleagues in the International Journal of Health Geographics teaches us that we should be vigilant for changes in the frequency of infectious diseases and that a disease reported from Belgium is likely to have counterparts in Australia as climate change takes hold. In fact it may well come to be that the discerning general practitioner will play a role in epidemiology similar to that of the famous Dr.Will Pickles of Wensleydale England who described “catarrhal jaundice” (now recognised as Hepatitis A) in his book “Epidemiology in Country Practice” in 1923
The researchers investigated the rise of Nephropathia Epidemica (NE) in Belgium. NE is present throughout most of Europe; common symptoms include high fever, headache and nausea; unfortunately it has become the most important cause of infectious acute kidney failure in Belgium and can be is fatal.
The paper by Clement and colleagues investigates the link between climate change and the recent increase in NE, which is spread by rodents. The authors predict that NE could become a highly endemic disease in Belgium and neighbouring countries.
NE is caused by a hantavirus which is is carried by rodents, particularly the bank vole a small burrowing rodent. It is passed on to humans via airborne traces of infectious excrement. The bank vole’s staple food is the seed of deciduous broad-leaf trees, such as acorns and beechnuts. Recent abundacnce of seed, possibly the result of climate change, could provide an explanation for the increases in NE, via an increased autumn food supply for the bank vole.
The study examined variation in the incidence of NE, changes in seed abundance and climatic data from 1985 to 2007. The results suggest recent changes in climate have encouraged the spread of NE by bank voles in Belgium. The combined effect of increasingly hotter summers and autumns is seen to match a growth in incidences of NE in recent years.
A total of 2,048 NE cases were registered during this 23 year period, with numbers increasing throughout. The record year in 2005 saw 372 cases, which was considered a near-epidemic for Belgium. This situation has also been confirmed in neighbouring countries such as Germany, where a record 1,687 NE cases were officially registered in 2007.
From 1993 onwards, all NE peaks were preceded by an abundance of seeds in the previous autumn. The average temperature in the period 1996-2007 of 11.4°C was significantly higher than the previous decade (10.7°C), although rainfall was similar in the two periods. This suggests that a high availability of seed, and therefore a higher survival of bank voles in autumn-winter, provides a link between climate change and fluctuations in NE.
Overall The study demonstrated that simple climate variables can help predict increases in NE and inform prevention policies by health authorities. The authors also suggest that climate change could affect other emerging infections in Western Europe, such as Lyme disease, carried by both ticks and rodents, and which can affect the joints, nervous system and heart.
To return to the work of Will Pickles in 1928, his careful documentation of new cases of hepatitis A and their contacts in the villages in which he practiced for 50 years established the incubation period of 26-35 days and the period of infectivity, data accepted to this day. Reading the words of Pickles who walked to the top of a high, looked down on Wensleydale and wrote:-
“… one by one I made out most of our grey villages with their thin pall of smoke. And as I watched the evening train creeping up the valley with its pauses at our three stations, a quaint thought came into my head and it was that there was hardly a man, woman or child in all those villages of whom I did not know the Christian name and with whom I was not on terms of intimate friendship. My wife and I say that we know most of the dogs and, indeed some of the cats”,
one can speculate that both general practice and the tools of the epidemiologist have changed but they remain founded on careful observation and documentation. Such commitment will define the change of disease in the climate change environment of Australia and all of us can play a part.
Source: Clement, J., Vercauteren, J., Verstraeten, W.W. et al. (2009). Relating increasing hantavirus incidences to the changing climate: the mast connection.
International Journal of Health Geographics. 8:1.