15 Pohorecka.indd - Journal of Apicultural Science

Vol. 55 No. 1 2011
Journal of Apicultural Science
137
EPIZOOTIC STATUS OF APIARIES
WITH MASSIVE LOSSES OF BEE COLONIES (2008-2009)
K r y s t y n a P o h o r e c k a 1,2, A n d r z e j B o b e r 2,
M a r t a S k u b i d a 2, D a g m a r a Z d a ń s k a 2
1
Research Institute of Horticulture, Apiculture Division, Puławy, Poland
2
National Veterinary Research Institute, Department of Parasitology
with Laboratory of Honey Bee Diseases, Puławy, Poland
E-mail: [email protected]
Received 30 May 2011; Accepted 10 June 2011
S u m m a r y
In 2008 and 2009, winter bee colony mortality in apiaries showed losses which ranged from 30%
to 100%. Analyses of tests results obtained from 1000 colonies (from 142 apiaries) were performed
to determine the impact of pathogens on the winter bee colony mortality in apiaries. Relationships
between individual pathogens were also determined. Dead bees were sampled separately from an
average of 7 colonies in each apiary, and the presence of V. destructor, Nosema spp. and viruses:
ABPV, CBPV, IAPV, DWV was detected. Co-infection with 3 or 4 pathogens was detected in over
60% of bee colonies. Infestation of V. destructor was found in 88.7% of the colonies while infection
of deformed wing virus (DWV) in 76%. A similar number of colonies (74%) were infected with
Nosema spp. parasites. Acute bee paralysis virus (ABPV) was detected in 35% of the examined
colonies and chronic bee paralysis virus (CBPV) was found in only 7,8% of the colonies. The level
of Varroa destructor and Nosema spp. infestation was high (averaged 192 mites per sample and
18 million Nosema spores per bee). Severe colony losses in examined apiaries could be attributed
to the wide prevalence of V. destructor with DWV and ABPV infections, and/or Nosema spp.
infestation. Losses can also be attributed to the co-occurrence of these pathogens in bee colonies
and their total negative impact on the bees.
Keywords: Apis mellifera, winter losses, pathogens.
INTRODUCTION
High winter losses of bee colonies are
one of main but not the only one reason,
for the decline in the number of honey
bee colonies in many European and North
American countries (vanEngelsdorp et
al., 2010, 2011; Neumann and Carreck,
2010; Potss, 2010). During the winter
of 2007/2008, beekeepers from most
regions of Poland reported extraordinary
losses of bee colonies. The colony losses
amounted to 15.9% between the autumn
of 2007 and spring of 2008. About 1.0%
of all beekeepers in Poland took part in
the 2007/2008 survey (Topolsk a et al.,
2008). However, according to beekeeper
associations, colony losses were as high
as 30.0%. In 2009, colony mortality
was significantly lower. Beekeepers lost
approximately 8.7% of their colonies
during the winter of 2008/2009. The
number of beekeepers participating in the
2008/2009 survey amounted to about 1.2%
of all beekeepers in Poland. The 8.7% figure
was in agreement with the assessment
of beekeeper associations. According to
the beekeeper associations, the colony
mortality was about 9.0% (Topolska et
al., 2010). However, in certain regions
the losses were substantially higher than
the average. The reasons for the mass bee
mortality are not clear, especially when
mortality was accompanied with a sudden
depopulation of honeybees. Among
the many mentioned factors, the most
important are bee diseases (Cox- Foster
et al., 2007; Higest et al., 2008, 2009;
138
Berthoud et al., 2010; Carrec k et al.,
2010; Chauzat et al., 2010a; Dahle,
2010; Le Conte, 2010; Martin et al.,
2010; Paxton, 2010; Topolska et
al., 2010). The epizootic state of polish
apiaries is unknown. Therefore, the aim
of this study was to identify the pathogens
occurring in dead honey bee colonies
originated from apiaries where the severe
colony losses ranged from 30% to 100%.
We also determined the relationships
between pathogens and colony mortality
as well as the relationships between the
pathogens.
MATERIAL AND METHODS
Research was carried out in 2008 - 2009,
in apiaries where the colony losses during
the wintering period amounted to at least
30.0%. At the beginning of each year,
beekeepers were notified about the purpose
of the research. We gave the beekeepers
standardized precise rules for sample
collection as well as a questionnaire that
provided us with information about the
scale of bee losses and types of colony
management. According to our instructions,
in each apiary, samples of dead bees were
supposed to be collected for laboratory
tests separately, from bottom boards of 10
randomly chosen colonies. Samples were
immediately sent to the laboratory after the
first spring beekeeper inspection; between
March and 30 April in 2008 and 2009.
In 2008 and 2009, we received the
material for laboratory tests from about
300 beekeepers. The samples came
from apiaries located in all 16 Polish
provinces, but most of the samples came
from 9 regions of Poland: Małopolskie
(46 apiaries), Lubelskie (39 apiaries),
Zachodniopomorskie
(36
apiaries)
Mazowieckie (29 apiaries), Wielkopolskie
(29 apiaries), Dolnośląskie (22 apiaries),
Świetokrzyskie (21 apiaries), Śląskie
(21 apiaries), and Lubuskie (10 apiaries).
The samples were kept in separate
test tubes and stored at -20°C until
used. Samples from each apiary were
individually examined. Varroa destructor
was detected by the shaking method and
the number of mites was recorded. In each
sample, infestation with Nosema spp. was
investigated microscopically. A Bürker
haemocytometer was used to determine
the number of Nosema spp. spores. Each
homogenized sample was prepared from
the abdomens of 30 bees and 30 ml of water.
The occurrence of bee viruses i.e. Chronic
bee paralysis virus (CBPV), Acute bee
paralysis virus (ABPV), Deformed wing
virus (DWV), and Israeli acute paralysis
virus (IAPV) were detected using one step
RT-PCR. Five dead bees from each sample
were homogenized and used for total RNA
extraction by use of the Total RNA Mini
Kit (A&A BIOTECHNOLOGY) and
afterwards for reverse transcription - PCR,
by employing the One-step RT-PCR Kit
(Qiagen). Each virus was targeted with
a single diagnostic primer pair (Tab. 1).
One step RT-PCR was performed using
the following thermal profile: reverse
transcription for 30 min at 50°C followed
by polymerase chain reaction: 15 min at
95°C followed by 35 cycles with 1 min at
94°C, 1 min at 55°C, and 1 min at 72°C,
followed by 10 min at 72°C for final
Table 1
Primers used for the detection of ABPV, CBPV, DWV and IAPV
Virus
Sequence of primer (5’-3’)
Length of
product (bp)
Reference
ABPV
GCT CCT ATT GCT CGG TTT TTC GGT
TTA TGT GTC CAG AGA CTG TAT CCA
TCA GAC ACC GAA TCT GAT TAT TG
ACT ACT AGA AAC TCG TCG CTT CG
TCG ACA ATT TTC GGA CAT CA
ATC AGC GCT TAG TGG AGG AA
ATC GGC TAA GGG GTT TGT TT
CGA TGA ACA ACG GAA GGT TT
900
C h e n et al. (2006)
569
B l a n c h a r d et al. (2007)
702
C h e n et al. (2006)
767
C ox- Fo s t e r et al. (2007)
B l a n c h a r d et al. (2008)
CBPV
DWV
IAPV
Vol. 55 No. 1 2011
Journal of Apicultural Science
extension. Positive and negative controls
were included in each run of RT - PCR.
Amplicons were analyzed by means of
1.0% agarose gel electrophoresis, staining
by ethidium bromide, and visualizing by
UV light. Specificity of the PCR products
was verified by sequencing, and comparing
to isolates of ABPV, CBPV, DWV and
IAPV available on GenBank database.
Unfortunately, due to a number of
reasons, some beekeepers took less than
the requested number of samples, and not
all samples were collected according to
our instructions. That was why, in some
cases, either samples were not suitable for
examining or we were unable to perform
all the tests. For our analysis, we only
took into account the results from those
apiaries that fulfilled 2 requirements.
The first requirement was that samples
were collected from at least 5 colonies
and they were tested for the presence of
all 6 pathogens. The second requirement
was that beekeepers gave complete and
precise information on the extent of losses
in their questionnaire. We have statistically
analyzed data from 142 apiaries (total
1000 bee colonies) that fulfilled the
2 requirements for both 2008 and 2009.
For each apiary, 7 samples were analyzed
on average.
The percentage of the winter-losses were
calculated for each apiary individually.
The percentage was based on the number
of successfully overwintered colonies in
relation to the number of colonies prepared
for wintering in autumn. In order to
139
analyze the impact of the pathogens, we
grouped apiaries according to those that
had a similar percentage of winter losses,
i.e. the groups were at 10%-intervals on a
range from 30% to 100%.
Statistical analysis
Linear regression analysis and test t
for α=0.05 were carried out in order to
determine the impact of: the number of
pathogens that had co-occurred, the level
of the V. destructor infestation, level of
the Nosema spp. infestation, and viral
infections on the losses of colonies and the
relations between pathogens. Comparisons
of average values of evaluated parameters
for homogeneous groups were performed
using the ANOVA test, and multiple
comparisons with Tukey and KruskalWallis tests on a level of significance
α=0.05. Statistica 8 software was used.
RESULTS
The most numerous groups were those
which had losses ranging from 30% to
50.0% (Tab. 2). In the other groups, the
numbers of apiaries and samples were
similar. In all the investigated apiaries from
autumn to spring, about 5440 bee colonies
were lost (58.4%). Depending on the size
of the apiary, from 3 to 385 of the colonies
died (38 on average) (Tab. 3). Samples
containing none of the six examined
pathogens amounted to 0.4%. Only 9.0% of
the samples were infected with 1 pathogen.
On the other hand, there was not even one
sample which contained all six pathogens.
The number of samples with 5 pathogens
Table 2
Number of apiaries and the different percentages of the winter losses
Extent of bee
colony losses (%)
Number
of apiaries
Mean number of dead
colonies per apiary
Number of examined
samples (colonies)
30-40
41-50
40
24.7
280
26
34.5
182
51-60
14
45.2
98
61-70
16
39.7
112
71-80
14
46.1
98
81-90
14
64.5
104
91-100
18
82.0
126
140
Table 3
Number of wintered and collapsed bee colonies in the apiaries analyzed in 2008-2009
9367
Average number
of colonies
per apiary
65.9
Range of the number of
the colonies per apiary
(min-max)
4-595
5439
38.3
3-385
State of apiaries
Total
Number of colonies in autumn
Number of colonies collapsed
from autumn to spring
Table 4
Level of the V.destructor infestation in the examined samples (colonies)
V. destructor
Level of infestation per
sample (number of mites)
Range
Mean
SD
(min-max)
Test results
Range of level
infestation
(number of mites
per sample)
Percentage
of samples
(n=1000)
negative
samples
n.d.
11.3
0
0
0
31.6
19.1
1.0- 49.0
14.6
positive
samples
low
1.0 -50.0
high
>50.0
57.1
287.5
51.0- 2628.0
310.04
total for positive
88.7
192.0
1.0-628.0
280.42
n.d.= not detected
Table 5
Level of the Nosema spp. infestation in the examined samples (colonies)
Range of level
infestation
Test results (number
of spores
x106 per ml)
negative
samples
Nosema spp.
positive
samples
Percentage
of samples
(n=1000)
Level of infestation per sample
(number spores x106 per ml)
Range
Mean
SD
(min-max)
0
25.5
0
0
0
low
(from 0.01 to 1.0 )
medium
(from 1.01 to 5.0)
11.0
0.49
0.01-1.0
0.28
17.5
2.82
1.02-5.00
1.14
high > 5.0
46.1
27.66
5.02-207.37
26.0
Total for positive
74.5
17.8
0.01-207.37
23.3
n.d.= not detected
was also low (2.0%). There was a large
number of colonies in which the presence
of 2, 3 or 4 pathogens were detected. Such
samples reached 26.7%, 38.0% and 24.0%,
respectively.
The presence of Varroa mites and the
deformed wing virus was detected most
frequently. V. destructor was found in
88.7% of samples, and there were 192
mites per sample, on average. A high
infestation level of V. destructor was
detected in more than half of the samples
(Tab. 4). Nosema spp. infestation was
also very frequent (74.6%) and level of
infestation was also high. About 46.0% of
the samples had more than 5 million spores
per milliliter of homogenate, and about
18 million Nosema spores/ml were found,
on average, in samples from infected
colonies (Tab. 5). The deformed wing
virus (DWV) was widespread; 76.1% of
colonies were infected. Acute bee paralysis
Vol. 55 No. 1 2011
Journal of Apicultural Science
141
Table 6
Relations between pathogen number, level of the V. destructor, level of the Nosema spp.
infestation and percentage of dead colonies
Parameters of the regression function α = 0.05
Regression Regression
Coefficient of
Y
coefficient
constant determination R2
X
Number of co-occurring
pathogens (from 1 to 6)
Level of
Percentage of
V. destructor infestation
(in number of mites per sample) dead colonies
Level of
Nosema spp. infestation
(in mln.spor/ml sample)
p-value
1.8716
53.1540
0.0061
0.0014
0.0017
58.1540
0.0004
0.5400
- 0.0311
47.1440
0.0026
0.0220
Table 7
Extent of bee colony losses depending on the co-occurring of different pathogens
and level of Varroa destructor and Nosema infection
Level of
V. destructor
infestation
ABPV negative
Level of Nosema spp.
samples = 0
infection
positive
(number of spores x106/ml) ABPV
samples = 1
from 0.01 to 1.0
≤ 100 mites
per sample
from 1.01 to 5.0
>5.0
from 0.01 to 1.0
>100 mites
per sample
from 1.01 to 5.0
>5.0
DWV negative
samples =0
DWV positive
samples =1
Colony
losses (%)
0
0
63.17 ab
1
0
90.80 c
0
1
51.16 a
1
1
61.30 ab
0
0
55.97 a
1
0
68.52 b
0
1
54.85 a
1
1
63.27 ab
0
0
52.87 a
1
0
47.13 a
0
1
57.53 a
1
1
57.65 a
0
0
55.01 a
1
0
75.31 bc
0
1
58.47 a
1
1
75.30 bc
0
0
57.28 a
1
0
88.10 c
0
1
54.18 a
1
1
63.60 ab
0
0
52.68 a
1
0
65.50 b
0
1
55.66 a
1
1
61.00 ab
Different letters denote statistically significant differences at α=0.05
142
virus (ABPV) was detected in 35.4% of the
colonies, and CBPV in 7.8%. Israeli acute
paralysis virus was detected for the first
time in Poland, in only 1 colony.
Analysis of the relation between
pathogens and rate of bee mortality
Significant (p=0.014) but poor (r=0.08)
relations between the number of detected
pathogens and the increase in colony
mortality were found. The average numbers
of pathogens co-occurring in bee colonies
were similar in all analyzed groups. The
number of co-occuring pathogens ranged
between 2.9 in the case of the apiaries
which had lost 30% of their colonies,
and 3.2 for apiaries which had lost all of
their colonies. Analysis of the relations
between V. destructor and Nosema spp
infestation and the severity of the colony
losses were made. The analysis showed
that the increase in dead colony numbers
was not connected with the increase in
the level of infestation by these parasites.
Infestation level of the V. destructor
and Nosema spp. did not differ among
varying degree of colony losses in apiaries
(Tab. 6). The number of DWV infected
bee colonies were high in all apiaries and
statistical analysis did not reveal an impact
of this virus on increasing colony mortality
ABPV 1 = positive samples
ABPV 0 = negative samples
(p-value 0.33). However, a correlation
between the presence of ABPV and bee
colony losses was found. The increase in
the number of colonies infected with this
virus was accompanied by the increase in
colony mortality (Fig. 1). If the number of
pathogens detected in mixed infection had
a slight impact on the extent of the colony
losses, this was significantly dependent
on the type of co-occurring pathogens.
We observed a significantly high bee
colony mortality for those apiaries where,
apart from other photogenes, ABPV was
detected (Tab. 7).
Analysis of the relationships between
the individual pathogens
Significant (p<0.001) but poor (r=- 0.15)
relationships were found for the level
of V. destructor infestation and the
level of Nosema spp. infection (Fig. 2).
However, a very strong correlation
was observed between the level of
V. destructor infestation and the infection
of bee colonies with DWV. The level of
V. destructor infestation was significantly
higher for colonies infected with DWV
(Fig. 3). This interaction was not found
for V. destructor and ABPV infection.
The mean number of Varroa mites
(185.8 per sample) in colonies with ABPV
Fig. 1. Analysis of the relation between the prevalence of ABPV and the extent of bee
colony losses (α=0.05, p<0.001).
Vol. 55 No. 1 2011
Journal of Apicultural Science
Fig. 2. Analysis of the relation between the level of V. destructor (in number of mites per
sample) and Nosema spp. (in number of spores x106/ml) infestation (α=0.05).
DWV 1 = positive samples
DWV 0 = negative samples
Fig. 3. Analysis of the relation between the level of V. destructor infestation
(in number of mites per sample) and DWV (α=0.05, p=0.01).
143
144
DWV 1 = positive samples
DWV 0 = negative samples
Fig. 4. Analysis of the relation between the level of Nosema spp. infestation
(in number of spores x106/ml) and DWV ((α=0.05, p<0.001).
Fig. 5. The extent of bee colony losses in examined apiaries from different provinces of Poland.
did not differ significantly from the number
of Varroa mites (161.9 per sample) in
colonies in which ABPV infection was
not detected (p-value=0.18). Similarly,
there was no interdependence between
V. destructor and CBPV virus infection.
The mean number of Varroa mites in
colonies with CBPV amounted to 146.2,
and the mean number of Varroa mites was
172.4 in colonies where CBPV was not
Vol. 55 No. 1 2011
Journal of Apicultural Science
present (p-value=0.39). We also did not
observe any relationship between the level
of Nosema spp. and ABPV or Nosema spp.
and CBPV infection. The mean number
of Nosema spores (12.2 x 106 per 1 ml)
in colonies with ABPV did not differ
significantly from the number of parasites
(13.9 x106 per 1 ml) in colonies without
detected ABPV infection (p-value=0.246).
The mean number of Nosema spores in
colonies with CBPV amounted to 12.9
x106, and 13.2 x106 in colonies where
CBPV was not detected (p-value=0.889).
In the case of Nosema spp. infection, only
a strong negative relation between this
pathogen and DWV was observed. The
bee colonies infected with DWV had a
significantly lower level of Nosema spp.
infection (Fig. 4).
Analysis of the extent of colony losses
among apiaries from the different
regions of Poland
The highest rate of overwintering
mortalities (above 60%) were observed
145
in 4 apiaries located in the KujawskoPomorskie,
Lubelskie,
WarmińskoMazurskie and Zachodniopomorskie
provinces. In apiaries belonging to the other
7 provinces, losses of bees were also high
and amounted to more than half of their bee
colonies (Fig. 5). The epizootic status of
apiaries from some regions of the country
differed significantly. In colonies from the
Warmińsko-Mazurskie voivodeship, the
level of V. destructor infestation and ABPV
infection was significantly higher. In
samples from Lubelskie, Świętokrzyskie,
Dolnośląskie, Śląskie and Wielkopolskie
only the number of V. destructor mites
was higher. In apiaries from KujawskoPomorskie and Zachodniopomorskie,
where losses of colonies were high, we did
not find significant differences in the level
of V. destructor, Nosema spp., and virus
infections in comparison with provinces
where losses were lower (Tab. 8).
Table 8
Prevalence of pathogens in colonies from different region of Poland
Province
V. destructor Nosema spp.
ABPV
CBPV
infestation
infection
DWV infection
infection
(mean number (mean number (%infection
(% of infected
of
infected
(%
of
infected
of mites/
of spores x
colonies)
colonies)
colonies)
6
sample)
10 /1 ml)
Dolnośląskie
157.9 ab
12.6 a
64.2 ab
0.0
86.8
Kujawsko-Pomorskie
65.1 a
9.1 a
66.7 ab
8.3
91.7
Lubelskie
196.9 ab
11.5 a
31.1 a
4.4
80.0
Lubuskie
111.0 a
13.8 a
32.7 a
2.0
63.3
Łódzkie
5.0 a
5.4 a
0.0 a
0.0
100.0
Małopolskie
139.3 a
17.7 a
40.4 a
16.0
65.4
Mazowieckie
135.5 a
8.4 a
22.3 a
5.0
77.7
Opolskie
7.8 a
27.1 ab
50.0 a
0.0
40.0
Podkarpackie
129.9 a
38.6 b
40.0 a
5.7
68.6
Podlaskie
23.2 a
2.0 a
10.0 a
0.0
90.0
Pomorskie
27.9 a
16.5 a
28.6 a
0.0
90.5
Śląskie
176.2 ab
7.5 a
4.2 a
0.0
62.5
Świętokrzyskie
308.0 bc
14.1 a
21.9 a
9.4
78.1
Warmińsko-Mazurskie
471.5 c
10.7 a
100.0 b
10.0
100.0
Wielkopolskie
258.0 bc
8.0 a
37.7 a
5.3
85.1
Zachodniopomorskie
133.8 a
13.5 a
34.9 a
13.4
73.3
Different letters denote statistically significant differences at α=0.05
146
DISCUSSION
Our laboratory test results revealed
that the epizootic status of the examined
apiaries posed a real threat to the
functioning of bee colonies and was the
main cause of death for most of them. We
found a noticeable prevalence of 3 out of
the 6 detected pathogens. Our results show
the dominant role of Varroa destructor
associated with the DWV viral infection
and/or Nosema spp., in relation to winter
colony losses.
The pathological effect of V. destructor
on bees is well known, and among other
effects, the effect of the V. destructor
depends on the rate of the mite infestation
of the colonies (Genersch, 2010).
We detected Varroa mites in almost all
the surveyed colonies. Half of the bee
colonies had high infestation levels (on
average about 200 parasites per sample).
The number of Varroa mites in those
colonies probably reached the “critical
threshold” which could lead to their death
(Delaplane and Hood, 1999). In the
case of absence of Varroa destructor,
most viruses isolated from honey bees
were considered to be non-threatening
to the bees. Such viruses mainly caused
covert, symptomless infection. DWV and
ABPV interactions with V. destructor,
transmission of virus particles, and immune
suppression of pupae and adult bees, leads
to rapid virus replications and outbreaks of
viral infection (Yang and Cox-Foster,
2005; van Engelsdorp and Meixner,
2009; Genersch, 2010). Berthoud et
al. (2010) reported statistically significant
correlations between ABPV and DWV
winter mortality of bee colonies. The
ABPV and DWV viral loads depended
on the health status of colonies and were
significantly higher in dead colonies. In
Germany (Genersch et al., 2010), the
negative impact of DWV and ABPV on
winter bee colony mortality has been
confirmed by bee monitoring program.
Highfield et al. (2009) reported that
DWV can potentially act independently
of Varroa mites to collapse a bee colony
bringing about colony losses. Therefore,
DWV may be a major factor in winter losses.
ABPV has been found to be associated with
dead colonies infested with Varroa mites
in Russia and the United States (Allen and
Ball, 1996). In our study, the ABPV virus
was present in 35% of the dead colonies.
Losses were significantly higher in apiaries
in which ABPV was found.
We detected the spores of the
Nosema spp. parasite in 75% of bee
samples. The average level of infestation
was high and amounted to 18 million
spores per bee. The preliminary study
of the epidemiological factors related to
honey bee colony losses conducted in
Spain, showed that colony losses could be
caused by Nosema ceranae (Higes et al.,
2010), and that Nosema ceranae was more
virulent than N. apis. However, regardless
of the genus, Nosema spp. was considered
to be the cause of winter mortalities when
the number of spores was higher than
10 million per bee (Chauzat et al., 2010b).
Because over 90% of bee colonies were
co-infected it is difficult to clearly define,
which of the detected pathogens played a
key role in winter mortality of bees. Each
of the identified pathogens causes serious
detrimental effects on the individual insects
and ultimately leads to disturbances in the
functioning of bee colonies. Therefore,
in co-infection, the synergistic, negative
impact of pathogens is observed.
Similar results concerning the level of the
V. destructor invasion in Polish apiaries,
were obtained by Topolska (2008). In
studies carried out on samples of dead bees
collected from 104 apiaries from various
regions of Poland, severe V. destructor
infestation, bees with deformed wings, or
ABPV infection were detected in 55% of
the apiaries. In 32% of the apiaries a severe
Nosema spp. infestation was detected.
For four years, Chauzat et al. (2010)
examined the incidence of infectious
agents and parasites in apiaries in which
the loss of colonies did not exceed 10%.
They reported a lower percentage of
colonies infected by V. destructor (20%
on average) and Nosema spp. (27%). The
numbers were different for beekeepers
Vol. 55 No. 1 2011
Journal of Apicultural Science
(hives) of various provinces who have high
mortality problem in their colonies. This
may attest to the fact, that in provinces
from which the most samples came from,
the problem of mass colony losses affected
the larger amount of apiaries. Confirmation
of these assumptions are data published
by Topolska (2008). The highest losses
of bee colonies were found in Lubelskie,
Zachodniopomorskie and Wielkopolskie.
We also received a large number of
samples from them. In some apiaries from
these provinces (Wielkopolskie, Śląskie,
Świętokrzyskie, Lubelskie) significantly
higher levels of the V. destructor infestation
were found.
CONCLUSION
1. The epizootic status of the examined
apiaries suggests that bee pathogens are
one of the main factors involved in high
mortality of honey bee colonies.
2. Severe colony losses in Polish apiaries
could be attributed to high levels of
V. destructor infestation with DWV and
ABPV viral infection and/or Nosema spp.
infection.
147
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149
STAN EPIZOOTYCZNY PASIEK, W KTÓRYCH WYSTĄPIŁA
MASOWA ŚMIERTELNOŚĆ RODZIN PSZCZELICH (2008-2009)
Pohorecka K., Bober A., Skubida M., Zdańska D.
S t r e s z c z e n i e
Celem badań była ocena sytuacji epizootycznej w pasiekach, w których odnotowano masową
śmiertelność rodzin pszczelich i określenie roli organizmów patogennych dla pszczół w etiologii
tego zjawiska.
Badaniami objęto pasieki, w których w okresie jesienno-zimowym zginęło co najmniej 30% rodzin
pszczelich. W latach 2008-2009 badaniami objęto około 300 pasiek zlokalizowanych na terenie
całego kraju. Największą liczbę pasiek do badania zgłoszono z terenu województwa małopolskiego,
lubelskiego, zachodniopomorskiego, mazowieckiego, wielkopolskiego, dolnośląskiego, śląskiego,
świętokrzyskiego i lubuskiego. W roku 2008 przebadano próby pochodzące z 265 pasiek, w roku
2009 z 24 pasiek. Materiał do badań laboratoryjnych stanowiły próbki martwych pszczół pobierane
przez pszczelarzy w czasie pierwszych wiosennych przeglądów, oddzielnie z kilku-kilkunastu
(w zależności od wielkości pasieki) losowo wybranych rodzin pszczelich. Z każdej pasieki, zbierano
w formie ankiety dodatkowe informacje niezbędne do późniejszej analizy wyników badań. W celu
zwiększenia dokładności analiz laboratoryjnych, badania wykonano na pojedynczych próbkach
pszczół. W każdej próbce oznaczano:
- obecność roztoczy V. destructor - metodą makroskopową, z uwzględnieniem oznaczenia liczby
pasożytów w każdej próbie.
- obecności grzybów z rodzaju Nosema spp. - metodą mikroskopową wg Cantwella (1970)
w modyfikacji własnej.
- obecność wirusów najbardziej patogennych dla pszczół: wirusa chronicznego paraliżu pszczół
(CBPV), wirusa ostrego paraliżu pszczół (ABPV), wirusa zdeformowanych skrzydeł (DWV), oraz
izraelskiego wirusa ostrego paraliżu pszczół (IAPV) metodą RT-PCR.
Analizę statystyczną uzyskanych wyników przeprowadzono łącznie dla 2 lat badań. Do
analizy wybrano wyniki tylko z tych pasiek, w których próbki pobrano z co najmniej 5 rodzin,
pobrany materiał pozwalał na wykonanie badań we wszystkich kierunkach, a informacje zawarte
w ankietach pozwalały ocenić wielkość strat. Ogółem analizę statystyczną przeprowadzono dla
danych uzyskanych z badań 1000 próbek (rodzin), które zostały pobrane ze 142 pasiek.
W analizowanych pasiekach, w okresie jesienno-zimowym zginęło od 30 do 100% rodzin.
Największą grupę stanowiły pasieki, w których straty mieściły się w zakresach od 30 do 40% i od
41 do 50%, w związku z czym, w tej grupie przebadano największą liczbę rodzin. W pozostałych,
zwiększających się o 10% przedziałach strat, liczba przebadanych pasiek i rodzin była zbliżona.
Ogółem, w pasiekach tych zginęło około 5440 rodzin pszczelich (58,4%), przy czym w zależności
od liczebności pasiek, osypywało się w nich od 3 do 385 rodzin, średnio 38 rodzin.
W większości badanych rodzin (99,6%) stwierdzono obecność co najmniej jednego spośród
oznaczanych patogenów, przy czym w około 90% rodzin były to zakażenia mieszane. Równoczesne
zakażenie 2 patogenami wykryto w 26,7% rodzin, trzema - w 38% rodzin, a czterema - w 24%
rodzin. Niewielki procent rodzin (2%) był zakażony równocześnie 5 patogenami, a w żadnej
z rodzin nie stwierdzono równoczesnej obecności wszystkich sześciu.
Inwazję V. destructor stwierdzono w 88,7% rodzin, przy czym w zakażonych próbkach było
średnio 192 pasożyty. Wysoki poziom inwazji (>50 roztoczy na próbkę) wykryto w 57% rodzin.
Natomiast obecność spor Nosema spp. stwierdzono w 74,5% rodzin, a wysoki poziom inwazji
(>5 milionów spor/ml) w 46,1% spośród wszystkich przebadanych rodzin. W próbkach zakażonych
rodzin stwierdzono średnio 18 milionów spor/ml.
150
Wśród infekcji wirusowych DWV był obecny w 76,1% rodzin, ABPV w 35,4%, CBPV tylko
w 7,8% rodzin. Po raz pierwszy w kraju, w próbce z 1 rodziny pszczelej wyizolowano wirusa IAPV.
Nie stwierdzono istotnych zależności pomiędzy liczbą zidentyfikowanych w rodzinach
patogenów, a procentem martwych rodzin w pasiekach. Równoczesną obecność średnio 3 patogenów
stwierdzano w rodzinach z pasiek o najniższym poziomie strat (30%), jak i w pasiekach, w których
ginęły wszystkie rodziny. Rodziny pszczele z pasiek o różnym nasileniu strat nie różniły się także
między sobą poziomem inwazji V. destructor, Nosema spp. i obecnością wirusa CBPV i DWV.
Stwierdzono natomiast istotną zależność pomiędzy liczbą rodzin zakażonych wirusem ABPV, a ich
śmiertelnością. Wzrostowi udziału martwych rodzin towarzyszył wzrost liczby rodzin zakażonych
tym wirusem.
Analiza zależności pomiędzy badanymi patogenami wykazała bardzo silną zależność pomiędzy
poziomem inwazji V. destructor, a występowaniem zakażenia wirusem zdeformowanych skrzydeł
(wartość współczynnika determinacji bliska jedności). Wzrost poziomu inwazji V. destructor
powodował rozwój tej infekcji wirusowej w rodzinach pszczelich. W przypadku zakażenia
Nosema spp. stwierdzono silną, ujemną zależność pomiędzy tym patogenem, a wirusem DWV.
W pozostałych analizach nie stwierdzono istotnych zależności pomiędzy badanymi patogenami
(poziomem inwazji V. destructor a CBPV, oraz poziomem inwazji Nosema spp. a CBPV i ABPV).
Słowa kluczowe: Apis mellifera, straty zimowe, patogeny.
Vol. 55 No. 1 2011
Journal of Apicultural Science
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