Honey bee pathogens and parasites in Swedish apiaries: a baseline study

Figures & data

Figure 1. Prevalence of Varroa and honey bee pathogens in Sweden 2016. Acute bee paralysis virus (ABPV), Deformed wing virus (DWV), Melissococcus plutonius (MP), Paenibacillus larvae (PL), and Varroa destructor (Varroa).

Table 1. Summary of questionnaire answers related to at least 2,185 colonies in Swedish apiaries surveyed in 2016. In 8 out of 376 study apiaries there was no information on the number of colonies.

Questions on	No. of apiaries with valid answers	No. of positive answers (%)	No. of colonies^a (positive answers)
Purchased queens, ≤1 yr	323	172 (53.3)	1089
From within county		135 (78.5)	768
From another county		34 (19.8)	302
From abroad		3 (1.7)	19
Purchased queens, >1 yr	323	151 (46.7)	838
From within county		115 (76.2)	616
From another county		35 (23.2)	215
From abroad		1 (0.7)	7
Moved colonies to the apiary, ≤1 yr	289	116 (40.1)	679
Within county		106 (91.4)	627
From another county		10 (8.6)	52
Moved colonies to the apiary, >1 yr	289	173 (59.9)	999
Within county		157 (90.8)	887
From another county		16 (9.2)	112
Treatment against Varroa	371	330 (88.9)	1964
Winter losses 2015/16	139	29 (20.9)	42^b

^a Not always equal to the total colonies in the apiaries due to missing data.

^b Out of the 655 colonies in the 139 apiaries.

Figure 2. Bar plots comparing the percentage of apiaries tested positive for Varroa and DWV in laboratory assays and the percentage of beekeepers who observed Varroa or any disease signs related to DWV.

Table 2. Results from the logistic regression models for risk factors associated with the outcomes high Varroa infestation (≥3 mites per 100 bees), high Deformed wing virus (DWV) virus loads (≥10⁷ virus copies per bee), and Paenibacillus larvae infection.

Outcome	Variable	Category	OR^a	95% CI^b	P-value
High Varroa infestation	Honey bee colonies in apiary	−	1.06	1.01 − 1.11	0.012
High DWV infection level	Varroa infestation level^c	Absent or low	1	−	<0.001
		High	5.94	3.64 − 9.82
Paenibacillus larvae infection	Last colony movement	>1 year	1	−	0.024
		≤1 year	2.99	1.19 − 8.19

^a OR = odds ratio.

^b CI = confidence interval.

^c Varroa infestation levels; Absent or low (<3 mites per 100 bees), High (≥3 mites per 100 bees).

Table 3. Results of a logistic regression model for risk factors associated with winter colony losses in Swedish apiaries.

Variable	Category	OR^a	95% CI^b	P-value
Colonies per beekeeper	–	0.98	0.96 − 1.0	0.048
Last colony movement	>1 year	1	–	0.023
	≤1 year	2.39	1.14 − 5.21
Varroa mite infestation level^c	Absent or low	1	–	0.002
	High	3.59	1.67 − 8.22

^a OR = odds ratio.

^b CI = confidence interval.

^c Varroa infestation levels: Absent or low (<3 mites per 100 bees); High (≥3 mites per 100 bees).