Factors influencing the prevalence and infestation levels of Varroa destructor in honeybee colonies in two highland agro-ecological zones of Uganda.

Varroa mites are ecto-parasites of honeybees and are a threat to the beekeeping industry. We identified the haplotype of Varroa mites and evaluated potential factors that influence their prevalence and infestation levels in the eastern and western highland agro-ecological zones of Uganda. This was done by collecting samples of adult worker bees between December 2014 and September 2015 in two sampling moments. Samples of bees were screened for Varroa using the ethanol wash method and the mites were identified by molecular techniques. All DNA sequences obtained from sampled mite populations in the two zones were 100 % identical to the Korean Haplotype (AF106899). Mean mite prevalence in the apiaries was 40 and 53 % for the western and eastern zones, respectively, during the first sampling. Over the second sampling, mean mite prevalence increased considerably in the western (59 %) but not in the eastern (51 %) zone. Factors that were associated with Varroa mite infestation levels include altitude, nature of apiary slope and apiary management practices during the first sampling. Our results further showed that Varroa mites were spreading from lower to higher elevations. Feral colonies were also infested with Varroa mites at infestation levels not significantly different from those in managed colonies. Colony productivity and strength were not correlated to mite infestation levels. We recommend a long-term Varroa mite monitoring strategy in areas of varying landscape and land use factors for a clear understanding of possible changes in mite infestation levels among African honeybees for informed decision making.

Agrochemical contaminants in six species of edible insects from Uganda and Kenya.

Edible insects are currently promoted worldwide as an alternative animal protein source, but they are mostly still harvested from the wild where they are predisposed to contamination with agrochemicals. This study analysed six species of edible insects (Ruspolia differens, Rhynchophorus phoenicis, Schistocerca gregaria, Oryctes sp, Pachnoda ephippiata and Acanthoplus sp) collected from different habitats and/or reared in the laboratory in Kenya and Uganda for safety from agrochemical contaminants using liquid chromatography tandem mass spectrometry. The residue levels were statistically compared with the Codex Alimentarius Commission maximum residue limits (MRLs). Residues of only nine agrochemicals were detected in the insects out of 374 chemicals which were screened. The detected agrochemicals include two insecticides (aminocarb and pymetrozine), three herbicides (atraton, methabenzthiazuron and metazachlor) and four fungicides (carboxin, fenpropimorph, fludioxonil and metalaxyl). Ruspolia differens and adult Oryctes sp were free from detectable levels of any agrochemical. Whereas the pesticides residue levels in most insect samples were within maximum residue limits, some of them notably P. ephippiata from black soldier fly larval frass, R. phoenicis from oil palm and P. ephippiata from plant compost contained 2-, 8- and 49-fold higher levels of atraton, methabenzthiazuron and metazachlor, respectively, than MRLs. These findings demonstrate that edible insects may accumulate harmful residues of agrochemicals from the environment where they breed or forage, rendering them unsafe for human consumption or feeding animals. The mechanisms for possible bioaccumulation of these agrochemicals in the insects remains to be investigated. Development of methods for farming edible insects under regulated indoor conditions to ensure their safety as sources of food or feed is recommended.

Predatory and competitive interaction in Anopheles gambiae sensu lato larval breeding habitats in selected villages of central Uganda.

BACKGROUND: Malaria is often persistent in communities surrounded by mosquito breeding habitats. Anopheles gambiae sensu lato exploit a variety of aquatic habitats, but the biotic determinants of its preferences are poorly understood. This study aimed to identify and quantify macroinvertebrates in different habitat types with determined water physico-chemical parameters to establish those preferred by An. gambiae s.l. larvae as well as their predators and competitors. METHODS: A field survey was conducted in Kibuye and Kayonjo villages located in the vicinity of the River Sezibwa, north-eastern Uganda to identify Anopheline larval habitats shared by aquatic insects. Habitats were geo-recorded and as streams, ponds, temporary pools and roadside ditches. From October to December 2017, random microhabitats/quadrats were selected from each habitat type, their water physico-chemical parameters (electrical conductivity, total dissolved solids, temperature and pH) were measured, and they were sampled for macroinvertebrates using standard dippers. All collected arthropod macroinvertebrates were then morphologically identified to family level and enumerated. RESULTS: Principal component analysis showed that the four larval habitat types were characterized by distinct physico-chemical parameter profiles. Ponds and streams had the highest number and diversity of macroinvertebrate insect taxa and sustained few An. gambiae s.l. larvae. Anopheles gambiae s.l. were more common in roadside ditches and particularly abundant in temporary pools which it commonly shared with Dytiscidae (predaceous diving beetles) and Culex spp. Cluster correlation analysis conducted on the abundance of these taxa within quadrats suggested that An. gambiae s.l. and Dytiscidae have the most similar patterns of microhabitat use, followed by Cybaeidae (water spiders). Whilst Culex spp. co-occurred with An. gambiae s.l. in some habitats, there was only partial niche overlap and no clear evidence of competition between the two mosquito taxa. CONCLUSIONS: Ponds and streams are habitats that host the largest diversity and abundance of aquatic insect taxa. Anopheles gambiae s.l. larvae distinctively preferred temporary pools and roadside ditches, where they were exposed to few predators and no apparent competition by Culex spp. Further studies should aim to test the impact of Dytiscidae and Cybaeidae on An. gambiae s.l. dynamics experimentally.

Nosema neumanni n. sp. (Microsporidia, Nosematidae), a new microsporidian parasite of honeybees, Apis mellifera in Uganda.

The microsporidium Nosema neumanni n. sp., a new parasite of the honeybee Apis mellifera is described based on its ultra-structural and molecular characteristics. Structures resembling microsporidian spores were found by microscopic examination of honeybees from Uganda. Molecular confirmation failed when PCR primers specific for Nosema apis and Nosema ceranae were used, but was successful with primers covering the whole family of Nosematidae. We performed transmission electron microscopy and found typical microsporidian spores which were smaller (length: 2.36±0.14µm and width: 1.78±0.06µm; n=6) and had fewer polar filament coils (10-12) when compared to those of known species infecting honeybees. The entire 16S SSU rRNA region was amplified, cloned and sequenced and was found to be unique with the highest resemblance (97% identity) to N. apis. The incidence of N. neumanni n. sp. in Ugandan honeybees was found to be much higher than of the two other Nosema species.

First detection of Paenibacillus larvae the causative agent of American Foulbrood in a Ugandan honeybee colony.

Paenibacillus larvae is a highly contagious and often lethal widely distributed pathogen of honeybees, Apis mellifera but has not been reported in eastern Africa to date. We investigated the presence of P. larvae in the eastern and western highland agro-ecological zones of Uganda by collecting brood and honey samples from 67 honeybee colonies in two sampling occasions and cultivated them for P. larvae. Also, 8 honeys imported and locally retailed in Uganda were sampled and cultivated for P. larvae. Our aim was to establish the presence and distribution of P. larvae in honeybee populations in the two highland agro-ecological zones of Uganda and to determine if honeys that were locally retailed contained this lethal pathogen. One honeybee colony without clinical symptoms for P. larvae in an apiary located in a protected area of the western highlands of Uganda was found positive for P. larvae. The strain of this P. larvae was genotyped and found to be ERIC I. In order to compare its virulence with P. larvae reference strains, in vitro infection experiments were conducted with carniolan honeybee larvae from the research laboratory at Ghent University, Belgium. The results show that the virulence of the P. larvae strain found in Uganda was at least equally high. The epidemiological implication of the presence of P. larvae in a protected area is discussed.