ZKEA

Biological Terrorism : Emerging Diseases : Biological Warfare

Emerging Disease, Animals

One example of this is the unexplained spread of Phocine Distemper virus(PDV) amongst seal populations around the world. PDV is closely related to canine distemper and has apparently always afflicted seal populations to one degree or another. However, in recent years there have been a series of increasingly lethal PDV epidemics amongst seal populations including one in 1998 that wiped out half of Europe's seals. What is causing this epidemic? No one is sure, although it is suspected that pollution and global warming may be combining to depress seal immune systems.

An even more amazing instance is the massive global decline in amphibian populations. Around the world - even in relatively pristine areas - amphibian populations have been crashing. Frogs are particularly hard-hit. In some areas entire species have vanished without a trace in the space of just a few years. The causes appear to be quite complex and remain to be clarified, but the spread of increasingly pathogenic viral and fungal infections seem to be a key element. Amphibians have fragile physiologies and therefore are extremely sensitive to environmental disruption. They thus act as sentinels for coming biological events. Right now these sentinels are flashing red warnings everywhere on the planet.

Another recent example is the introduction of the West Nile virus into a new ecology - North America. As its name implies, West Nile originated in tropical Africa. Apparently it recently jumped to the United States, found the warming climate to it ts liking, and proceeded to sicken and kill a number of people. However, it's far more deadly to other species. In some situations it appears to kill 100% of infected American Crows. Many other bird species, in particular raptors and owls, are also extremely vulnerable.

Yet another example is the recent cancer epidemic afflicting Australia's Tasmanian Devils. Tasmanian Devils are a predatory marsupial confined to - you guessed it - Tasmania. In prehistoric times they ranged in mainland Australia as well, but were apparently eliminated by the aboriginal introduction of the dingo. In any event, the devils are now faced by a retrovirus which induces a fast-growing and fatal form of cancer. The species will probably survive this onslaught, even though it looks like the majority of the population might eventually succumb.

The plant world is just as vulnerable to such epidemics and the results are evident. For instance, in the western United States oak trees are rapidly dying due to a new disease called, appropriately enough, Sudden Oak Death. This disease is caused by the previously unknown fungus Phytophthora ramorum, which is genetically closely related to the species that caused the great Irish potato famine (another classic example of a plant epidemic, by the way). Phytophthora infects over 20 species of plants, including redwoods, although it appears to be particularly deadly in three of these species. Again, no one knows why this fungus has appeared and is exacting such a huge cost. But, as in the previous examples, it is likely that environmental disruption is the key catalyst.

Epidemics and population die-offs are hardly abnormal in the natural world. Ever since multicellular life first evolved during the Cambrian Explosion (and probably before), all species have had to deal with viruses and epidemic disease. Therefore this dynamic is hardly new; pathogenic organisms are nature's crowd-control mechanism and have no rival in efficiency when the time comes to cut a given population down to size. However, what is different in the modern world is the extent and degree to which these epidemics are taking place. The world's natural environment is now in a profoundly stressed state. It is impossible to predict what the final outcome might be.

The cynic might think the previous examples are only of interest to nature-lovers. Who cares if frogs and oak tress die off? That will hardly affect the price of beer or next season's sports schedule. This attitude overlooks the fact that Homo sapiens, whether we like to admit it or not, are as tied to the environment as every other species. We live on this planet too, breathing the same air and drinking the same water. We too are exposed to these same environmental stresses. Further, pathogenic organisms do not greatly respect artificial boundaries. History is full of diseases which crossed over from animal populations into humanity, with devastating results. Among many others, these diseases have historically included smallpox (which evolved from a related pox in the Egyptian era), bubonic plague and influenza. As the world grows ever more out of balance, the pace of these new diseases has increased in recent years. Thus we have the AIDS epidemic, Ebola and during late 2003, SARS.

The world is sending us a message. It remains to be seen if we look up early enough from our television and pizza in order to take action. Link: CDC Report On West Nile Virus
Link: Nature: Distemper killing lions
Link3: Canine Distemper Virus

Link: West Nile, North American Birds
Link: PDV, Virus Decimating Seal Populations
Link: Analysis of the PDV epidemic (technical)
Link: BBC: New Diseases Threaten both Humans and Wildlife
Link: Federation American Scientists: Infectious Zoonotic Disease Surveillance
Link: Wordwide Amphibian Population Declines and Emerging Disease (technical)
Link: BBC: Virus Threatens UK's Red Squirrels