The gazette-times., August 27, 1914, HOME AND FARM MAGAZINE SECTION, Page 7, Image 13

HOME AND FARM MAGAZINE SECTION
Bee Infection Cured by Heat
By L. P. White, M. D., Ph. D.
TO reduce the losses due to boo dis-J
eases beekeepers have often em
ployed heat in one form or an
ftther. The direct flame has been used
In scorching or burning the inside of
lives that have housed infected col
onies. Before being fed baek to bees
honey is often heated for the purpose
of destroying the germs of bee dis
eases, should any be present Heat is
Used in the rendering of wax and in
the making of comb foundation. It is
natural and very appropriate, there
fore that beekeepers should inquire
ebout the amount of heating that is
necessary to destroy the germs that
produce diseases among bees.
As no work had been done to deter
mine the facts relative to this question
with any degree of accuracy, the wri
ter haa performed during the last two
years a number of experiments for the
purpose of ascertaining them. It may
be of interest to beekeepers to know
in a genera way how these experiments
were made. An aqueous suspension of
larvae sick or dead of the disease is
made and placed in a small glass, tube.
This tube is immersed in water of the
iti'.mnerature desired iu the heating.
After the germ-containing material is
heated in this way it must be tested
to determine whether or not tho germs
mtru hfAn d.iifrrwpr). In the case of
American foul brood this can be done
bv inoeulatinc a suitable artificial
medium with the heated material and
observing the presence or absence of
growth of bacillus larvae, the genu of
this disease.
Testing for Disease.
As there is no artificial medium
now known suitable for cultivating
the infecting BL'ent of either Euro
pean foul brood, sacbrood, or Nosema
disease, healthy colonies of bees must
ha inoculated in making the test in
ease of these diseases. This is done by
feeding the bees the heated germ-con
taining material in sirup. If the dis
ah is produced by this feeding.
naturally tho infecting agent has not
Wn destroyed bv it. By repeated ex
periments of this kind in which the
lemnnrature used in tho heating is
varied, tho minimum temperature at
which any virus is killed can DC -ae-tnrminpd.
Thirteen experiments for
European foul brood, twenty-two for
eacbrood and twenty for iMosema ais
ann have been made in whieh healthy
eolonies were inoculated with heated
arnrmenntttininff material from the98
thrca diseases, respectively. In the last
Aihpiuu the stomachs from diseased
bees furnished the germeontainmg
material for heating and feeding. In
these experiments the temperature was
mnin!;nid for 10 mlnutos as a rule.
Nearly a century and a half ago the
name "foul brood" was used tor a
destructive brood disorder of bees, and
for almost a century later it was ap
tlv the custom to diagnose af
foul brood any destructive disease of
fcmnrf About half a century aeo bee
keepers began to note that all of the
ymtA diseases are not the same. They
began, therefore, to write of different
forms of foul brood. At the present
time it is known that there are at
least three infectious diseases of the
brood of bees. All of these diseases
are more or less destructive, and it is
quite likely that each of them has now
than hpim dispensed aB mm
hrnnA. Tn America these brood dis
eases are now known as European foul
brood, American foul brood ana sac
brood.
Fool Broods.
Tn "Riirnnean foul brood death oc
curs early, tho larvae dying usually be
fore the time far cell capping, mere
ill no viscidity (ropiness) to the de
caying larvae as a rule, ana no pro
tinntK-Bil ndor present.
. Numerous samples of this disease
have been examined from the United
States, and some from Canada. Its
Entrland. Germany,
Switzerland and Denmark is strongly
mrroofna bv written reports from
these countries. It is very probable
that the disease ban a mucn wiaer
geographical distribution than these
fncin indicate.
Two years ago the fact was demon
strated that the germ causing Euro
fnnl brood is the microorganism
to which tho name bacillus pluton is
given. In a paper announcing the fact
it was t:itl that the studies then
made indicated that the germ is easily
killed by heat. This beiier nas Deen
confirmed by further experiments.
American foul brood is the disease
of the brood of bees that is best known
to beekeepers and is the one the pres
ence of which they have been able to
recognize most easily. In this disease
the larvae usually die after the cells
containing them are capped, ine uis
ease is characterized especially by the
marked viscidity (ropiness) manifest
ed by the decaying larvae mat are
iWrl of the disease. The pronounced
odor noticeable within hives housing
colonics affected Dy wis disease, espe
cially in its later stages, is another
well-known characteristic.
TTnt.il seven vears affo the cause of
American foul brood was not known.
At that time the fact was demon
strated nnsitivplv that the eerm caus
ing the disease is the one to wnicn me
name bacillus larvae is given.
The facts obtained to date are too
meager to justify anything more than
a general statement regarding me
minimum amount of heating that can
be employed in rendering material con
taining the eerm or American ioui
brood non- infectious. Taking rather
wide limits, it may safely be said that
th minimum temperature at wnicn
this can he done, if the temperature is
applied for 10 minutes, lies somewhere
between 90 degrees C. (14 degrees I'.J
and 100 degrees 0. (212 degrees F.).
It seems quite probable, indeed, tnai
a temperature less than degrees 0.
(208.4 degrees r.) will snitieo u ap
plied for 10 minutes. When 100 de
irrun C was used the spores of baceil
!us larvae were killed in less than five
minutes.
Sacbrood.
Ohsprvant beekeepers have for many
years noted the presence of dead brood
which seemed to them to oo unrerent
from that dead of foul brood. Some
were inclined to believe that tho dis
ease was an infectious one; a larger
number apparently were disposed to
ascribe the trouble to sucn causes as
an unsatisfactory queen, starvation.
and the like. This brood disease has
been recently demonstrated to bo an
infectious one, and the name "sac
brood", has been given to it. Larvae
that die of this disease do so almost in
variably after the time of cell cap
ping. The most characteristic symp
tom of the diseaso is the saclike ap
pearance of the dead larvae when they
are removed from the cell, ims racr
suggested the name "sacbrood" for
the disease.
Morn than a vear ago it was again
the writer's fortune to determine the
cause of another brood disease. Un
like the cause of either European foul
brood or American toul brood, tne in
fecting agent causing sacbrood lias not
vpt hppn seen. It was demonstrated,
however, that the infecting agent in
this disease passes through tne pores
of pnrthenware filters. For this reason
the cause of sacbrood is spoken of as
filterable virus.
Tn a nanpr announcing the cause of
sacbrood the statement is made that
the germ causing the disease is de
stroyed by a comparatively small
amount of heat. Tlvis belief is con-
'irmed by the results of experiments.
Vptv little is known about the dis
eases of adult bees. Many names have
been used for the purpose of desig
nating 'hem, but tlm numoer or sucn
diseases is probably small. There is
only one adult disease that can be
diagnosed at present by laboratory
methods. This ono is the Nosema dis
ease. Nosema Disease.
Fifty-seven years ago Dr. Dbnhotf
mn.1n a morn or less brief study of a
disease of adult bee3 in Germany, He
observed that the stomach was the
that, was primarily affected. By
feeding to healthy colonies in sirup the
crushed stomaens irom arreciea oees
Diinhoff demonstrated that the disease
could be transmitted to healthy colo
nloa Tt was therefore infectious.
The work of Dbnhoff had been prac
tically forgotten, apparently, when
7nm1nr nf 'Erlano-en. Germany, five
years ago observed tho presence of a
disease amonif the auit Dees. nom
the evidonce at band it seems most
probable that the disorder encountered
hv Diinhoff and the one encountered
by Zander are one and the same dis
ease.
Aside from rediscovering the diseaso,
Zander has identified the germ caus
ing it as a protozoan (a one-celled ani
mal parasite and has given to it the
name Nosema apis, for tne disease ue
has nsed the name "Nosema Seuehe."
This is an appropriate one, as it sug
gests somewhat the nature ot tne dis
ease. The name "Nosema disease,"
which the writer suggests as the com
mon name for this disease, is, it will
be observed, only a translation of the
German name used by Zander.
The fferm Nosema apis gains en
trance to the body of the bee by way
of the alimentary canal. In the walls
of the stomach the growth and multi
plication of the paraiste take place to
an enormous extent, sausing tae ao
normal appearance manifested by the
organ. When the disease reacnes an
advanced stage the stomach 18 wnite
and frasile and reveals upon a micro
scopic examination the presence of the
parasite in very large numDers. in tne
sprin2 of the vcar, especially, many
weak colonies show upon examination
a high percentage of JNosema-iniecteu
bees. Quite often, indeed, in tne ex
aminations that have been made of
such colonies, 50 to 90 per cent of the
bees in sampljs taken from them were
found to be. infected with the parasite.
It is an interesting and important fact
that a very large number of colonies
which are strong and apparently doing
well are found upon examination to
contain at least a small percentage of
N'osenia-infected bees.
Summary.
The rrfults of these experiments
ohow that when they are maintained
for 10 minutes the minimum tempera
tures that can be used for destroying
the germs of the four bee diseases now
known to be infectious are as follows:
(1) The minimum temperature for
European foul brood lies somewhere
between 00 C. (140 F.) and 65 C.
(MO" F.), being approximately 63 C.
(14o.4" F.).
C21 The minimum temperature for
American foul brood lies somewhere be
tween 90 ('. (394 F.) and 100 C.
(212) F., being probably less than
9S C. (208.4 F.).
(Si The minimum temperature for
sacbrood lies somewhero between 55
C. (111.31 F.) and 60 C. (140 F.), be
ing approximately 0s t. (IAqA I.).
C41 The minimum temperature for
Nosema disease lies between 55 C
(131 F.) and 60 C. (110 F.), be
ing approximately 57 C. (134.6 F.).
Tt will he noted, therefore, that 63
C. (145.4 F.) for European foul brood,
98 C. 208.4 F.) for American foul
brood, 58 C. 136.4 F.) for sacbrood
and 57 C. 134.6 F.) for Nosema dis
easo are the approximate minimum
temperatures at which the germs of
these diseases, respctcively, are de
stroyed. Since there are varying rac
tors in experiments of this nature that
tend to produce slight variations in re
sults, these temperatures are rererrea
to as being approximate. It is probable
that future experiments may cause
slight changes to be made in these con
clusions. Nothing more than a com
paratively slight variation is to be ex
pected, however. In practice the bee
keeper, in destroying these germs by
heating, will naturally use a quantity
of heat somewhat in execss of the
minimum amount that is absolutely
necessary.
Some generalizations may now be
made which will be of interest to the
beekeeper. The melting point of bees
wax is between 62 C. (143.6 F.) and
64 C. (147.2 F.), inclusive. It will
hp observed that this same tempera
ture in 10 minutes will destroy the
germ causing European foul brood, and
that it is about 10 F. above that wbica
will destroy the germs of sacbrood
and Nosema disease. A further inter
esting generalization may be made con
cerning the heating of honey, Honey
when heated to 160 F. reaches a tem
perature 15 F. above the temperature
necessary to destroy the germ of Euro
pean foul brood and about 23 F. above
the temperature that will destroy the
infecting agents of sacbrood and
Nosema disease. The infecting agents
of these three diseases of the bee,
therefore, will be destroyed when the
temperature of 160 F. is used in the
commercial handling of honey. Finally,
it is believed that the results of this
work on the thermal death point of
the viruses of the bee diseases will be
directly applicable to the control of
these diseases.
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