THE DISEASES OF BEES.
Dysentery: How Produced--Indications--Treatment. Foul-Brood: two
kinds--Nature--Propagation. Mr. Cheshire's Discoveries and
Treatment--Fatal Effects of Disease--Detection--Vertigo--Analogy
of Human and Bee Diseases.
How far the diseases of domesticated animals are due to the conditions
to which they are subjected by man, and which are always, to some
extent, contrary to the natural mode of life of the creatures, we are
at present unable to say. We can, however, point with some certainty
to cases in which birds and quadrupeds, which are made subservient to
our needs or our convenience, suffer in consequence of our treatment.
In some degree, this is true with regard to bees. In a wild state
their habitations may, indeed, expose them to risks they do not run in
hives, but these artificial dwellings, on the other hand, tend to the
development, or the extension of, at least two maladies to which their
occupants are subject. These are the deadly evils of dysentery and
so-called "foul-brood."
Dysentery has been known in apiaries from the time of Columella, in
the first century of our era, who attributed it to the effect of
food derived by the bees from the elm and the spurge. Other more
recent writers have ascribed it to over-indulgence in spring-honey,
wheresoever derived: others, again, to the consumption of stores which
had candied in the cells during the winter. More recent investigations
show that there are several means by which this trouble may be
generated. In the first place, ineffective ventilation, by permitting
the condensation of moisture on the combs, and its admixture with the
food stores, is a prolific source of the mischief. During the winter,
the low temperature is constantly reducing to a watery condition
the aqueous vapour given off by respiration. This vapour, like our
own perspiration, contains matter derived from impurities in the
circulating fluid, and is the natural vehicle for their removal. If,
then, such moisture again enters the body of the bee, it is simply a
poison, whose effects become manifest by producing diarrhœa, distension
of the abdomen, and more or less speedy death.
Again, if the stocks be supplied in the late autumn with syrup too
watery for the bees to seal over in the cells, contact with air sets
up a chemical change, and a certain amount of acid is generated,
which makes the honey most prejudicial to the health of the stock, by
deranging their digestive functions.
Thirdly, if during the winter time, when the insects are closely
confined to their dwellings by the weather, and when they are, under
ordinary conditions, very quiescent, they be disturbed and excited,
they are apt to gorge themselves with food; and having no natural means
of working off the extra quantity they have taken, the system is
overloaded, and the stomach and intestines suffer from the too great
burden thrown on them.
The occurrence of this malady is indicated by the altered appearance
and odour of the excrement, which, instead of being reddish yellow,
becomes of a muddy black colour, and has an intolerably foul smell.
It is, moreover, deposited by the weakened insects, contrary to their
cleanly habits, on the combs, the inner walls of the hives, on the
floor-board, and at the entrance of their dwellings.
The avoidance of the causes of the generation of the disease is a
comparatively easy matter. The means of cure are, first, the removal
of the reasons for its occurrence, and, secondly, the immediate and
thorough cleansing of all parts of a hive soiled by the sick bees. It
is still better, if possible, to remove the stock into a perfectly
fresh dwelling; and it is advisable to take away all combs with
unsealed honey, and substitute sealed stores, or to feed the bees with
barley-sugar.
"Foul-brood" is a much more formidable malady, and is often
encountered. It is, indeed, a terror to apiarians, for not only is
it very fatal to any stock in which it appears, but, from its ready
contagiousness, it may depopulate any number of previously healthy
communities, and may extend from one apiary to several others in the
neighbourhood.
As the name implies, it has been thought to be a disease of the
larvæ, and there are said to be two kinds, called respectively the
_dry_ and the _wet_. The former of these is much less serious, and is
not contagious. The young merely die in their cells; their bodies
desiccate, and there is an end of the matter. In the other variety, the
brood remains dark and shiny in the hatching-places, and emits a most
offensive odour, perceptible at some distance from the hive. When the
mischief is very great, combs are sometimes removed which are masses of
corruption and fœtor.
Microscopical investigations led to the belief that the source of
this dire pest was a microbe, allied to _micrococcus_. If the germs
of this lowly organism find a lodgment on the tender skin of a larva,
they propagate with immense rapidity, and cause the death of the
young insect. Then, wafted about the hive by the currents produced
in ventilation, they pass from one part to another; or, attaching
themselves to the bodies of adult bees, they are carried from cell
to cell, and each of these thus infected, in its turn, becomes a new
centre of deadly plague.
Dr. Schönfeld in Germany made a series of interesting experiments,
which he considered conclusive on the question of the origin and spread
of this disease. From a small piece of foul-brood he propagated, by
suitable means, large quantities of the fatal so-called _micrococcus_,
and with it he was able to infect a healthy stock. He, moreover,
established the fact that the dried germs float readily in the air.
Placing some of the foul-brood in a bell-glass, in which he inserted
lightly a plug of cotton-wool, he caused a gentle atmospheric current
to pass into the glass, and out by the tube. Then, moistening the
cotton-wool with water, and putting some of the liquid under a
microscope, he detected what he concluded to be numerous spores.
This circumstance throws a light on the contamination of the different
hives in an apiary, through one that has become infected; as, no doubt,
during the process of ventilation, many germs of the disease find their
way out of the entrances. It is probable that robber-bees are also very
frequently the carriers of contagion. Taking advantage of the dwindling
down of a stock suffering from the disease, these plunderers pilfer
the honey, and, in so doing, receive on their bodies the fatal seeds
of the malady, which they then carry to their own stocks. In this way
the existence of the pest in one community may become the cause of its
extension throughout a neighbourhood. It is, therefore, of the utmost
importance that the signs of the appearance of the evil should be
constantly watched, and very stringent measures applied whenever its
existence is ascertained.
Until quite lately it was thought that no means of cure, strictly so
called, existed. The germs are so minute, and are capable of such
diffusion and adherence in a hive, that half-measures proved, as usual,
of no avail. The removal of the combs and bees to a fresh hive, and
thoroughly sprinkling them with salicilic acid and water, has been
recommended as a remedial course; but bee-keepers found that nothing
short of the complete destruction of the infected community was likely
to be really effective, and the first loss, in such a case, might save
the entire destruction of all the stocks in the apiary. The very honey
stored in the combs had to be sacrificed also; for in it the dangerous
germs settle, and being used by the nurse-bees for feeding the larvæ,
become the continued, and possibly unsuspected, source of mischief to
any hive to which it is imparted. If the disease appeared in a straw
skep, it was considered desirable to destroy it with fire. If it found
its way into a bar-frame hive, every frame, every portion, even every
crevice, must be treated. Thorough boiling in a copper has been found
helpful in eradicating the mischief, but could not alone be relied
upon. A strong mixture of chloride of lime and water, or of salicilic
acid and water, applied carefully to every part, has been found more
effective. The important facts to be remembered are that, owing to the
extreme minuteness of the germs, their multitudes, and their great
vitality, it is very easy for some to escape destruction, and to become
the sources of future mischief, unless the most radical methods of
destruction are applied to them.
A new light has, however, just been thrown on this important subject
by Mr. Frank Cheshire, of Acton, who has done so much good work
in the anatomy of bees, and in their practical management. He has
now satisfied himself, by long-continued and careful microscopic
investigation, that the origin of foul-brood is a _bacillus_, not a
_micrococcus_,[5] and that the disease extends to all the inmates of
the hive. But what is of far greater moment to apiarians is, that Mr.
Cheshire claims to have discovered a means of completely curing the
dire plague. This consists in the administration of _phenol_, which
is one of the components of carbolic acid. Syrup is made with 3 lbs.
of loaf-sugar to a quart of water, and to this is added 1/500 part
of pure _phenol_. By removing the stored honey, and pouring the syrup
into cells around the infected parts of combs containing foul-brood,
the bees are induced to consume the medicated food. The "nurses" supply
it also to the larvæ, and the result is, that not only is the progress
of the disease stopped, but renewed courage and hope are infused into
the community, who remove the dead larvæ, clear out the polluted cells,
and bring about an entire renewal of healthy conditions. Should further
facts prove all that Mr. Cheshire expects, he will be regarded by
apiarians in future with as much admiration as Jenner, the introducer
of vaccination, is looked upon by the medical world. His generous
publication of his discoveries, so that all interested may have the
benefit of them, lays all bee-keepers under great obligations to him.
[Footnote 5: Those who wish for details on this and other points should
read Mr. Cheshire's admirable papers in the _British Bee-Journal_ for
August, 1884.]
As an example of the terrible results of this pest to the bee-keeper,
the case of the well-known German bee-master, Dzierzon, may be
mentioned. In the year 1848 the disease broke out in his apiary, and
more than 500 stocks were destroyed by it; in fact, only ten hives
escaped the pestilence. John Hunter--the author of a good _Manual
of Bee-Keeping_--records that from a friend, who had complained of
not finding his bees profitable, he purchased all his stocks, some
twenty in number, and removed them to his garden. They proved to have
foul-brood in them, and not only did the whole of them perish, but
all Mr. Hunter's own stocks, and, in addition, two or three years of
trouble were required to eradicate the mischief from the apiary.
The late Mr. Woodbury, whose name is "a household word" among
bee-keepers, was unfortunate enough to have this disease among his
hives in the spring and summer of 1863. He published a graphic account
of his trouble in the _Journal of Horticulture_ of July 21st, 1863,
entitled, "A Dwindling Apiary." By very vigorous measures he was able
to get rid of the pest; but the conclusions to which he came were
the following: "First let me endorse the opinions of both Dzierzon
and Rothe, that, except under very especial circumstances, it is
unadvisable to attempt the cure of a foul-broody stock: better, far
better, to consign its inhabitants to the brimstone-pit: the hive
itself, if a straw one, to the flames: the comb to the melting-pot: and
appropriate the honey to any purpose except that of feeding bees."
It is now known that this treatment is by no means always successful
when the _bacilli_ have reached the "resting" or "spore" stage.
The detection of signs of the disease is not very difficult, especially
in hives with movable frames. If, during the working season, a stock
seems not only not to increase, but to diminish in numbers; if fewer
and fewer bees appear active about the entrance; and if, above all,
a peculiarly disagreeable odour is perceptible, at even one or two
feet from the entrance, it is time to look to the condition of the
interior. An infected comb, on examination, is seen to be dark and
unwholesome-looking. If the caps covering the brood be distinctly
sunk, so as to show a concave surface, the existence of the disease is
almost a certainty; and if the covering of one or more of these cells
be removed, there will be found dark coffee-coloured, slimy liquid, the
remains of the larvæ destroyed by the _bacillus_.
From what we have said of this disease it will be seen that it is
most important for any one about to commence bee-keeping to be sure
the stocks he may purchase are not only themselves free from disease,
but come from an apiary absolutely uninfected by it. Many a beginner
in apiculture has been so disheartened, and has suffered such severe
loss from foul-brood in his hives, that he has given up bee-keeping
in disgust. We need hardly say that any man who knowingly sold hives
with foul-brood in them, would deserve to be visited with penalties
for damages, which we have no doubt his victim could obtain by legal
process.
Some writers enumerate _vertigo_, or giddiness and staggering, among
the diseases of bees. We incline to the belief that cases of the kind
observed were due to the individuals having been stung in fighting,
though it is possible that mistakes in pasturage _may_ occasionally be
made, and that the nectar of certain flowers may induce disorder in the
bee-constitution. We, however, doubt the likelihood of the quick senses
of the insect being at fault with regard to food which will prove
hurtful.
One other malady has been occasionally noticed, viz., the swelling of
the terminal segments of the antennæ. The occurrence of this mischief
is too rare to need further remark, beyond the suggestion that it may
be the result of _microbe_ germs having made a lodgment in the tender
organs affected.
There is a striking analogy in the results of insanitary conditions,
and the propagation of zymotic disease among the human family and
among bees. Unwholesome food, defective ventilation, the diffusion
of poisonous germs, produce, among both orders of beings, similar
disastrous effects; and this sketch of the diseases of one class of
domesticated insects may serve to point a moral for the guidance of
mankind in social economy. The same inexorable laws of health and
sickness prevail in the highest and the inferior orders of animal
existences, and with unvarying steadfastness is proclaimed the solemn
warning "Be not deceived: God is not mocked. Whatsoever a man soweth
that shall he also reap."