Through
most of history people have feared fungi. Once regarded as the
work of evil spirits or the devil, even in our enlightened era
they're still treated with suspicion in much of the western
world.
It's easy to see why fungophobia
is widespread. Many moulds, and a number of fleshy mushrooms
of woodlands and meadows produce small quantities of toxins.
Some, like the Destroying Angel, Amanita virosa and its
relatives are deadly poisonous and have killed many an unwary
diner.
Insidious moulds have caused the most widespread havoc. From
the Middle Ages until the mid-1900s, at least 65 poisoning epidemics
broke out in central Europe and France when people unknowingly
ingested the alkaloids
produced by ergot, Claviceps purpurea—a fungus that
parasitizes rye. Symptoms of ergot poisoning, or ergotism, include
terrible abdominal pains and burning sensations, followed by
convulsions, and hallucinations. Some of ergot's alkaloids
reduce peripheral blood flow leading to gangrene and loss of
limbs.
Once known as St. Anthony's fire, ergotism is rarely a problem
for humans now, but it can still affect farm animals. Beneficial
derivatives of ergot include a drug that induces childbirth
and controls bleeding in newborn babies. Ergots contain lysergic
acid from which LSD, a hallucinogenic drug, is derived. It is
not clear how or where the lysergic acid in historic cases of
ergotism was converted to LSD to give the 'mad' symtoms of victims.
Fungi are responsible for the majority of plant diseases, and
have devastated many a food crop. In 1845, the mould Phytophthora
infestans turned potatoes throughout Ireland into a rotting
mush. Thousands of Irish men, women, and children starved to
death. Many survivors fled to North America to make a new life
for themselves. In 1847 alone, some 90,000 Irish emigrants headed
for Canada.
This wasn't the first time a fungus changed the course of history.
Scientists who have studied biblical accounts of famines in
Egypt and Israel—and the mass migrations of people that
resulted—believe the crops failed because of rusts, a group
of fungi that destroy cereal crops.
Almost any food crop you choose to name is at the mercy of at
least one fungal blight or mildew. Wheat rusts gave prairie
farmers a dismal time in the 1930s, and grape mildews almost
destroyed the French wine industry in the mid-1800s. Farmers
are constantly on the alert against these pathogenic fungi.
Nor are trees spared from fungal disease. The ravages of the
fungus Cryphonectria parasitica (the agent of chestnut
blight) almost wiped out the once majestic sweet American chestnut
tree. It survived, but only in isolated populations in North
America, and it rarely reaches maturity.
Dutch elm disease, first discovered in North America in 1930,
has since killed billions of trees, and is now present wherever
American elms grow. It is caused by the fungus Ophiostoma
ulmi, spread from tree to tree by the native elm bark beetle.
A much more deadly strain developed in the North American elm
host returned to Europe to play havoc with European elm species
(O. novo-ulmi)
Beech stands in the ancient Acadian forest were devastated by
beech bark disease in the 1930s. The fungus causing the disease
(Nectria galligena) is ferried from tree to tree by an
introduced insect, Beech Scale. Fungi are also responsible for
Pine blister rust and tar spot on maple.
Apart from a few uncomfortable ailments like athletes foot,
fungi do not normally cause serious disease in humans. One exception
is histoplasmosis, caused by Histoplasma capsulatum found
in bird droppings in contact with soil. It is especially a problem
below starling roosts and in bat guano in caves. Symptoms of
the disease are similar to those of tuberculosis. Another is
fungal endocarditis, an inflammation of the heart tissues caused
by a filamentous fungus, Aspergillus fumigatus, or the
yeast Candida albicans which causes thrush. Fungal diseases
of humans are called mycoses.
Generally, pathogenic fungi are only able to attack if a person's
immune system has been compromised. When antibiotics remove
a body's healthy bacterial flora they leave the door wide open
to fungal infection. Sadly, many AIDS-related deaths are the
result of mycoses.
Another modern fungus-related health problem is an allergic
respiratory condition brought on by inhaling mould spores. Mouldy
buildings are one source, and are a serious health risk to sufferers.
The vital natural processes of rot and decay do not stop at
your front door. In fact your front door and any other wood
used in construction is also liable to attract saprobe fungi.
Just provide a few damp areas with poor ventilation and watch
them set to work!
One recent addition to this rogue's gallery of fungi is a microorganism
of the genus Batrachochytrium. In recent years it has
been killing frogs and other amphibians around the world. Biologists
suspect that changing environmental conditions may have impaired
amphibian immune systems , leaving the creatures vulnerable to
fungal attack. |
