Mixed infection in the brood diseases of bees

ALBERT R. MANN
LIBRARY

New York STATE COLLEGES
OF
AGRICULTURE AND HoME ECONOMICS

AT

CORNELL UNIVERSITY

EVERETT FRANKLIN PHILLIPS

BEEKEEPING LIBRARY

Reprinted from the JouRNAL oF Economic Enromovoey, Vol. 14, February, 1921, No. 1

MIXED INFECTION IN THE BROOD DISEASES OF BEES

By ARNOLD P. STURTEVANT, Specialist in the Bacteriology of Bee Diseases, Bureau of

_o Eniomology, United States Department of Agriculture

The two principal brood diseases of bees, European foulbrood and
American foulbrood, heretofore have not been found associated together
commonly in the same colony. The generally accepted belief has been
that it is indeed a rare occurrence to find both diseases under these
conditions. Sacbrood, on the other hand, is much more often found in
greater or less quantity associated with either European foulbrood or
American foulbrood, but seldom assuming dangerous proportions,
either alone or in conjunction with the others. Statistics for the past
few years, however, show that these cases of what may be called mixed
infection are probably more common than was previously supposed and
may account for some of the puzzling instances where colonies have not
responded to treatment in the customary manner, thereby causing
beekeepers to believe they have some new form of brood disease, or that
the disease is showing some new unheard of characteristics.

Cases of so-called mixed infections are not at all uncommon among
human diseases. Where this condition occurs, such as when a person
affected with typhoid fever develops pneumonia at the same time, it is
always the individual to whom the term mixed infection is applied.
It is a somewhat different matter in the case of the brood diseases of
bees. In the first place, so far as is known, the organisms causing these
two diseases, Bacillus larvae of American foulbrood and Bacillus pluton
of European foulbrood, have never been found together in the same
individual larva. It is, therefore, the colony as whole which is to

es

'

128 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14

be considered as the individual unit, as is the case in the majority of
the manipulations of beekeeping practice. This fact makes the problem
slightly different from a case of mixed infection as considered from the
point of view of human medicine. However, since different individuals
are involved in the mixed infections there is no “a priori’’ reason for
considering such cases as impossible.

The first published report of an authentic instance where both Ameri-
can and European foulbrood were found together in the same comb from
a diseased colony was reported by McCray.! This report was concern-
ing a sample (4982) received at the laboratory for diagnosis May 4, 1916,
from Stanislaus County, California. Previous to this case only one other
such sample (2598 from Brown County, Wisconsin in 1911) had been
received for diagnosis, showing the presence of both diseases, but no
report concerning it was published. ‘These two samples were the only
known authentic cases on record either in the Bee-Culture Laboratory
among practically 5000 samples received up to 1916, or in the beekeeping
literature. These two cases were considered to be interesting in that
they demonstrated that the presence of both diseases at the same time
in a colony was possible, but not much importance was given the matter
because of their rare occurrence. White? states that ‘‘such a double
infection has been encountered in the writer’s experience very rarely.
In such diagnoses, therefore, after European foulbrood had been found
in the sample, American foulbrood is seldom looked for.” This practice
has been the custom generally as well when American foulbrood was
found present in a sample, no further search for European foulbrood
being made unless there were present strikingly prominent symptoms
abnormal for American foulbrood. As a result the diagnostic records
of the Office of Bee-Culture show but six cases of mixed infection up to
December 31, 1918, among the approximately 6000 sample records.

Developments during the year 1919, however, showed that mixed or
double infection is more probable than had been previously supposed.
These facts were particularly impressed upon the writer during the
spring of 1919 while on a trip investigating the bee disease conditions in
the State of California. While in the field during a period of less than
one month, and in three different counties of the State of California, six
cases were found showing both American foulbrood and European foul-
brood in the same colonies. Each case was diagnosed posivitely at
once in the field by means of microscopic examination of dead larvae
showing characteristic symptoms of the two diseases and found to con-
tain the specific causative organisms. It is interesting to note that three

1McCray, A. H.1916. Report of the finding of American Foulbrood and European
foulbrood in the same comb. Jour. or Eco. Ent. Vol. IX, p. 379.
2White, G. F., 1920. European foulbrood. U.S. Dept. of Agric. Bul. 810.

February, ’21] STURTEVANT: MIXED INFECTIONS 129

of the six samples were found in Stanislaus County in the same locality
as the sample reported by McCray in 1916. These cases were all found
in regions where both diseases are exceedingly prevalent and of long
standing. A few of the samples were fairly self evident from gross
appearances, but the majority required a more minute examination.

From that time on, particularly after returning to the laboratory in
Washington, more careful examination was made, both gross and
microscopic of all samples received because of suspicions aroused by
the unusual prevalence of the obvious cases found in California. This
was done in order to eliminate the danger of overlooking cases where one
disease might be predominant over the other, whether both diseases
were suspected or not, causing the less prominent to be overlooked.

As a result, during the remainder of the year 1919 from June until
December, twelve more such samples were received in the laboratory
from various parts of the country, (18 in all for that year, total 24) all of
which proved upon careful diagnosis to contain both American foul-
brood and European foulbrood in the same sample of comb. Further-
more, during the year 1920, up until November 15th, fourteen more
such samples were received, making a total in all of 38. Tables 1 and 2
give the data from sample records.

TaBLeE I.—CaseEs OF MIXED INFECTION FROM LABORATORY RECORDS
Apparent primary

Date Lab. No. State County invader from gross Remarks
appearance
9-20-11 2598 Wisconsin Brown ? Diagnosed by G. F. White
5- 4-16 4982 California Stanislaus American fb. Diagnosed by A. H. McCray
6— 3-16 5061 California Stanislaus American fb. Diagnosed by A. H. McCray
5-16-17 5392 Missouri Jasper Probably Afb.
5- 9-18 5836 Mississippi Washington ? Apparently about equa
10- 9-18 6122 Wisconsin Barron 2 More Efb than Afb
4-19-19 6437 California Santa Barbara Probably Efb. One cell Afb.
4-26-19 6441 California Sacramento American fb. From history of case
4-26-19 6442 California Sacramento American fb.
4-28-19 6445 California Stanislaus European fb. Few cells Afb.
4-30-19 6449 California Stanislaus American fb. Few cells Efb.
5- 1-19 6452 California * Stanislaus European fb. From history of case
5-20-19 6304 Missouri Lewis 2
6-11-19 6401 Ohio Ashtabula ?
6-27-19 6498 Iowa Johnson American fb. Efb early stages, also Sacbrood
8- 1-19 6629 Ohio Trumbull ?
8-15-19 6672 Connecticut Tolland Probably Efb. Afb slight amount
8-25-19 6698 Kansas Cherokee %,
8-29-19 6716 New York Cayuga American fb. Efb active Afb scales
9- 2-19 6721 Washington Pacific ? e
g- 2-19 6722 Washington Pacific ? Efb more prominent
9-19-19 6768 California Santa Barbara ? Afb 1st disease reported for county
9-26-19 6778 California Santa Barbara ?
10- 5-19 6834 California Santa Cruz m
5-12-20 6985 California Butte European fb. Afb one or two cells
5-29-20 7023 Michigan Calhoun ?
5-29-20 7025 Michigan Calhoun ?
5-29-20 7026 Wisconsin Fond du Lac European fb. Few cells Afb
6-17-20 7119 Washington Lewis ?
6-17-20 7120 Washington Lewis ? Also Sacbrood
6-22-20 7143 New York Allegany European fb. Few cells Afb.
6-24-20 7158 Pennsylvania Crawford ig
6-26-20 7172 New York Cayuga ?
6-26-20 7174 New York Cayuga ?
6-26-20 7177 Pennsylvania Crawford ?
7-21-20 7335 New York Seneca Probably Afb.
8- 5-20 7386 Indiana Blackford ?

8- 5-20 7387 Indiana Blackford ?

130 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14

TABLE II.—SampLes oF MIXED INFECTION BY YEARS

Samples of Total Samples

Year mixed infection received
MOTE ge ota ey ane ta Sah he Rn Sipe ape i ee 1 1042
LOT Gis sien eareacoastecteric rates hema ale Name a tee een etkealchevano 2 374
MO Usama eaeaa nt ns sears ae ea ah emer hla ewe 1 449
LOIS crcngts tenes daw emmardnestenra meer retemnmne aealnaam a 2 429
19ND: wrtonwmass sam mmanne tga Sarre eet we Red omeR 18 693.
VG20 wy cveesist apn mee Mae wee athe Ti Phe OER DOE BRE 14 698
1905-1920 38 7568

This marked apparent increase in cases of mixed infection carries
the subject over from one of scientific interest to one of practical im-
portance. As is shown in Table III, the 38 samples of mixed infection
have come from 24 counties in thirteen states, most of these located in
prominent beekeeping regions. In eleven of these thirteen states both
European foulbrood and American foulbrood as shown by samples of
disease received in the laboratory for diagnosis are prevalent and of
long standing. There are only about three or four other states where
both diseases have been found in quantity from which samples of mixed
infection have not been received, while only from two states of the
many where the diseases are only occasionally bad have such samples
been received.

TABLE III.—Sampe_es oF MIXED INFECTION BY STATES AND COUNTIES

State Counties Samples
ea Fen 1 ec ataonas ay denen wt caes panes uae omta nN ine ere aes bees 5 12
Connecticut: pusdceswman 2enneneiosaseans eae samens aRMNEHeR 1 1
Indiana: ncgamcavasnesatoateeses ais eee Rees yeseese 1 2
LOWS: ew ange Seton S Wasa EA SGAG an sms SA ee He aces 1 1

gs ERCTAS ASP 076 ct aa cst pe ele Ris Seatac inte ‘ona ogee onaneeatee 1 1
IVETE ebb ss &apslt ast slagu Sodas bese, es bpdetaav saan asas aaa sin ease os 1 2
IMETSSISSUD BI, eccercacctakeset can hacen aa stones DaectondliGwd yo rab iain odoin 1 1
IMIS STEN, “cain cy ecie-clen tns ect cebi Saves Syste Ou samacdane eg Meee lay luc inde i 2 2
ING Wr GEIS ets x sac ceyess ce Sep etett AR cn SPR cn A cra Kel hee 3 5
CE ac eso emg eg exccee date nf erin Eas Sip cde bce abe ET 2 2
d 24 06'S VARIA: dat: \ eee ere oD Re ere ere re eee eee eee 1 2
WiASCOnSinte ssa latin gies tae g aateleaene ants age hnen a antada ma Kapighen 3 2 3
Washington gxerdceenadsabee dvamoosecrer sus bendsemees 2 4

Statistics obtained from the sample records, however, are not entirely
conclusive since a majority of the samples come to the laboratory
unsolicited. Ifa careful survey could be made of the regions where the
brood diseases are bad and widespread, probably many more such cases
would come to light.

February, '21] STURTEVANT: MIXED INFECTIONS 131

TABLE IV.—DIsTRIBUTION OF SAMPLES OF MIXED INFECTION BY MONTHS

APE eis cate el oe ence cena ek eg es th tthe nee heer oes a tyaloabean tient cccet 5
IMLAY sirsetoch sent waa Sistine teen ll Me batch ear earer edca ee nied Rito IIS ao ata oa 9
SMT Sse cota a Baa ta ned ke aN aren ea ease et eg ots a est Ne eae as 10
JRE ss soins cee oe seca G5 sash em cat ug aby hil ac nan td es elit 1
BINS SUAS op Sar esc abn dca sia essa ian A eee se eo ts ets Pde GRP 6
OPPO DET soci ies aausbodsi wash did at ealrten tyme cco eases ceo eg denen: eaten 5
CE GB Ge desis ccs raced ceudviecs OA eee Aula cee nom vata tbc eibigens PANES Hiscs Wiync te whim wrest ad 1
INOMEMIDER sna cen ate ccta acinannmnisenaia tanec abiatulneanctereeene mere taiow manines Semen & 1

These samples of mixed infection have been examined in eight out of
the twelve months of the year, April to November inclusive, as shown in
Table IV. Twenty-four of the total 38 samples, nearly 65 per cent.,
were examined during the months of April, May and June, the months
during which European foulbrood is most prevalent. In contrast to
‘the spring months, eleven samples of mixed infection were examined
during August and September, and only one each in July, October and
November, a total of fourteen. :

The question, however, of which diesase is most often the primary
invader in a colony is difficult to answer, particularly without a history
of the colony and locality. (Table I). If only dried adhesive American
foulbrood scales are found, accompanied by numerous coiled fresh moist
melting larvae of European foulbrood, it is not difficult to say that
American foulbrood was the primary invader, perhaps during the pre-
vious season, as was the case of the sample reported by McCray. But
often there is no such demarkation. Because the presence of American
foulbrood depletes the strength of the colony this increases the probabil-
ity of European foulbrood infection.

Since the requirements of the treatment of the two diseases are so
entirely different, the necessity for correct diagnosis becomes of im-
portance, particularly in regions where both diseases have been prevalent
for some time. The presence of both diseases in the same colonies or
even in the same apiary is a complicating factor in the diagnosis and
treatment. Furthermore there is danger from the possibility of con-
tinued and confusing losses due to the ignorance of the presence of mixed
infection in colonies under such circumstances and resulting therefrom,
improper treatment which would only continue the losses.

Several samples have been received for diagnosis which beekeepers
have thought contained both diseases and which indeed seemed to have
some of the characteristics of each. Upon careful examination, however,
both gross and microscopic, these have mostly proven to be definitely
not mixed infections. The recognition of cases of mixed infection in

3Phillips, E. F., 1918. The control of European foulbrood. U.S. Dept. of Agric.
Farmers’ Bulletin 975, 16 pp.

182 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14

colonies is often difficult because of the fact, as is particularly the case
with European foulbrood, there are many irregularities and variations
in symptoms that often add to the confusion of the beekeeper in making
gross diagnosis hurriedly in the field. In order to more easily differen-
tiate some of these confusing symptoms to assist in gross diagnosis, they
may be divided into three classes. Occasionally in an unusually virulent
case of American foulbrood or in one where the bees have deserted the
brood because of its foul condition allowing what healthy brood there
is to starve, larvae will be found which have died while still coiled in the
cell, among the typical American foulbrood larvae. These coiled
larvae often have much the same appearance as typical European foul-
brood coiled larvae. However, the consistency is generally quite dif-
ferent from European foulbrood, more like the typical slimy glue-like
consistency of American foulbrood material. As a rule, however, the
symptoms of American foulbrood are uniformly constant because of the
fact that Bacillus larvae is almost always the only invader of the larvae
causing death and a type of decomposition which prevents growth of
other organisms. Several such cases were found in California.

A second class of confusing symptoms are found in samples which
come particularly from regions where European foulbrood has been
allowed to run unchecked for a long time. Such samples were found
in certain sections of California and have been received from various
other sections of the country. These samples show along with more
or less of the typically coiled European foulbrood larvae, large numbers
of larvae which have died after extending and even being sealed in the
cell, showing a consistency somewhat like that of American foulbrood
but more lumpy or like an old partly rotten rubber band. Sometimes
scales are found extended in the cells in such large numbers as to appear
on casual examination like an old comb of American foulbrood. Close
examination, however, shows the consistency, irregular shape and posi-
tion with lack of adherence to the cell wall to be different from that in
American foulbrood. This type was found to be quite prevalent in
California.

The third class is composed of cases of actual mixed infection where
typical American foulbrood, ropy larvae or scales, are associated in the
same comb with typical European foulbrood, coiled moist melting larvae,
or possibly occasionally the abnormal rubbery irregular larvae mentioned
above. The active stage of the two diseases often seems to be localized
more or less in different parts of the comb. This is probably due to

“White, G. F. 1920. American foulbrood. U. S. Dept. of Agric. Bul. No. 809.
5Sturtevant, A. P., 1920. A study of the behavior of colonies affected by European
foulbrood of bees. U.S. Dept. of Agric. Bul. No. 804.

February, ’21] STURTEVANT: MIXED INFECTIONS 133

the fact that the queen would tend to desert that section of the comb
containing the American foulbrood, particularly where this disease was
the primary invader. In many cases one or the other of the diseases
will be more prominent, at least in the active stages. This fact may
be one of the causes for cases of mixed infection having been overlooked,
the beekeeper seeing only the prominent outstanding symptoms. There-
fore in cases where there is doubt or suspicion that both diseases may be
present in the same colony, a positive laboratory diagnosis often appears
to be desirable.

As is well known, the shaking method of treatment in its essentials
is so far the only successful way of treating American foulbrood.6 The
nature of Bacillus larvae has prevented success along any other line,
because of its ability to form exceedingly resistant spores and especially
to decompose the dead larva in such a way as to cause the mass contain-
ing large numbers of these spores to adhere to the cell wall as if glued.
It has been learned furthermore, often by sad experience, that the
shaking treatment is practically never successful in the treatment of
European foulbrood; in fact, often when used causes the disease to be
spread all the more because of the weakening effect the shaking has on the
colonies.’ The requirements for the successful treatment of European
foulbrood have been found to be fundamentally dependent upon ade-
quately strengthening the colonies with young bees sufficiently to throw
off the disease,’ at the same time combined with the requeening of the
diseased colonies with vigorous young Italian queens, permitting the
bees themselves to remove the infected material.

The apparent logical solution of the problem of the treatment for a
known case of mixed infection, therefore, is to combine the treatments for
both American foulbrood and European foulbrood as a single treatment.
In other words, the one or more colonies known or strongly suspected
to have mixed infection should be shaken as for American foulbrood,
requeening them with vigorous young Italian queens and later strength-
ening them by the addition of young bees or hatching brood from a
healthy colony, or by uniting later. Strength of colony is the important
factor combined with the shaking and requeening with vigorous Italian
stock.

The problem of the control of mixed infections of American foulbrood
and European foulbrood is primarily associated with the control of
European foulbrood. In localities where both diseases are prevalent

6Phillips, E. F. 1920. The control of American foulbrood. U.S. Dept. of Agric.,
Farmers’ Bulletin No. 1084. :

7Phillips, E. F. 1918. The control of European foulbrood. U.S. Dept. of Agric.,
Farmers’ Bulletin No. 975. .

134 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14

and there is suspicion of both being present in the same apiary, and pos-
sibly even some as mixed infection in the same colony, control of the
two diseases will depend upon the elimination of European foulbrood
first. This should be done by treating the entire apiary for European
foulbrood, by strengthening and requeening all the colonies with young
and vigorous Italian queens, which is after all only good beekeeping.
After the elimination of European foulbrood it will be a simple matter
to determine those colonies that have not responded to this treatment,
as being American foulbrood. This method is possible because of the
fact that American foulbrood seldom spreads with the rapidity of Euro-
pean foulbrood, particularly if care is taken to prevent robbing and mixing
up of combs. Those colonies which continue to show American foul-
brood remaining may now be given the usual shaking treatment.

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ixed infection in the brood diseases of

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