Correlation between Pest Abundance and Prevalence of Honeybee Pathogens at Selected Apiaries in Kenya, 2013/2014

Abstract

Routine screening for pathogens plays an invaluable role in the detection of diseases in pre-clinical stages and prevention of losses. The present study was part of a larger surveillance effort to identify the determinants of African honeybee health, and particularly, to quantify honeybee pest abundance and to determine the prevalence of pathogens across Kenya, where 161 colonies from 32 apiaries were examined. From each colony, 20 individuals of foragers, nurse bees, worker pupae and drone pupae were sampled separately. These were organized as 30 foragers, 32 nurse bees, 28 worker pupae and 10 drone pupae pools. The pest abundance was determined by counting the number per colony and their occurrence in each apiary was computed by calculating the arithmetic mean values. Honeybee diseases were detected by PCR and the prevalence per apiary was computed. Varroa destructor mites and Aethina tumida were the most abundant pests. There was near universal presence of Varroa and to a smaller extent A. tumida in majority of the locations visited. Overall, Varroa destructor virus 1, deformed wing virus and black queen cell virus were detected with the highest prevalence in the apiaries at 66%, 69% and 69% respectively. Other pathogens detected were Sacbrood virus, Israeli acute paralysis virus, Acute bee paralysis virus and Nosema ceranae at 28%, 22%, 19% and 13% respectively. Spearman Ranked Correlation between the mean pest count and the specific pathogen prevalence revealed an overall positive though non-significant correlation between the pests and most pathogens. The exceptional finding of this study was the identification of a key association between the abundance of A. tumida and Nosema infection, with a statistically significant positive correlation (R = 0.89803; P = 0.01507). Further studies will be required to understand the nature of this association with the aim of unravelling if the A. tumida has a biological role in Nosema transmission.

Keywords: Aethina tumida, Nosema, DWV, VDV 1, BQCV