Prevalence of parasites and diseases in the African honeybee (Apis mellifera scutellata Lepeletier) : with a particular focus on Varroa destructor

Abstract

The status of honeybee pathogens and parasites in the Gauteng region of South Africa was examined by collecting adult honeybee and worker brood samples from 13 Apis mellifera scutellata apiaries. The prevalence of pathogens and parasites were compared per season between sedentary (permanently stationed colonies) and migratory (transportation of colonies for pollination purposes) apiaries. Honeybee pathogens (Acute bee paralysis virus (ABPV), Black queen cell virus (BQCV), Chronic bee paralysis virus (CBPV), Deformed wing virus (DWV), Israeli acute paralysis virus (IAPV), Sacbrood virus (SBV), Varroa destructor Macula-like virus (VdMLV), Varroa destructor virus 1 (VDV-1), American foulbrood (AFB), European foulbrood (EFB), Nosema apis, Nosema ceranae) were diagnosed with PCR methods. Parasites (Bee lice, Capensis social parasites, Small hive beetles, Wax moths, Varroa destructor) and Chalkbrood were identified by visual inspection of adult honeybee and worker brood samples. No significant differences were found per season in the prevalence of pathogens and parasites between sedentary and migratory apiaries and consequently all results were pooled. Three (BQCV, VDV-1 and IAPV) of the eight viruses screened were detected in honeybees, while two of these viruses (VDV-1 and IAPV) were also confirmed in Varroa mites. This is the first report of IAPV and VDV-1 in South African honeybees as well as in Varroa mites infesting A. m. scutellata colonies. BQCV was the most common virus and was detected in eight of the 13 screened apiaries. EFB and N. apis were also detected in one and five of the apiaries, respectively. ABPV, CBPV, DWV, VdMLV, SBV, AFB and N. ceranae were not detected in the 13 apiaries. Honeybee parasites were frequently encountered in the majority of the apiaries with the most common parasite being the Varroa mite. A total of 12 pathogens and parasites were found in 13 apiaries in the Gauteng region of South Africa over a period of 14 months. The impact of Varroa mites on the development of honeybee colonies were examined from May to October 2011 in nine chemically treated and nine untreated colonies. The population dynamics of Varroa mites were examined by recording the number of mites that fell daily on the bottom boards of the hives (pre-, during and post- treatment), as well as the infestation rates of these mites in adult honeybees and worker brood cells. Honeybee colony development was measured by counting the number of adult honeybees, as well as the surface area of sealed and unsealed brood. Varroa mite fall was significantly higher in the treated apiary during treatment and in the three months following treatment. No significant differences were found in the adult honeybee and worker brood infestation rates in both apiaries during May, July and September. Honeybee colony development was similar for both apiaries indicating that colonies in the untreated apiary, that received no chemical treatment, survived just as well as the colonies that were treated. Honeybee (A. m. scutellata) colonies were thus able to survive without chemical treatment, in the presence of diverse pathogens and parasites.