Seasonal Variation of Honeybee Pathogens and its Association with Pollen Diversity in Uruguay.

Honeybees are susceptible to a wide range of pathogens, which have been related to the occurrence of colony loss episodes reported mainly in north hemisphere countries. Their ability to resist those infections is compromised if they are malnourished or exposed to pesticides. The aim of the present study was to carry out an epidemiological study in Uruguay, South America, in order to evaluate the dynamics and interaction of honeybee pathogens and evaluate their association with the presence of external stress factors such as restricted pollen diversity and presence of agrochemicals. We monitored 40 colonies in two apiaries over 24 months, regularly quantifying colony strength, parasite and pathogen status, and pollen diversity. Chlorinated pesticides, phosphorus, pyrethroid, fipronil, or sulfas were not found in stored pollen in any colony or season. Varroa destructor was widespread in March (end of summer-beginning of autumn), decreasing after acaricide treatments. Viruses ABPV, DWV, and SBV presented a similar trend, while IAPV and KBV were not detected. Nosema ceranae was detected along the year while Nosema apis was detected only in one sample. Fifteen percent of the colonies died, being associated to high V. destructor mite load in March and high N. ceranae spore loads in September. Although similar results have been reported in north hemisphere countries, this is the first study of these characteristics in Uruguay, highlighting the regional importance. On the other side, colonies with pollen of diverse botanical origins showed reduced viral infection levels, suggesting that an adequate nutrition is important for the development of healthy colonies.

American Foulbrood in Uruguay: twelve years from its first report.

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), a deleterious disease that affects honeybees. In Uruguay it was first reported in 1999. In 2001 the bacterium was spread all over the country, and its prevalence in honey was estimated in 51%. Two P. larvae genotypes were found; ERIC I - BOX A, worldwide distributed and ERIC I - BOX C, exclusively detected in Argentina until then. In the present manuscript we analyzed the evolution of AFB outbreaks from 1999 to 2009, presented a new nation-wide survey carried out during 2011 when a prevalence of 2% was found and discuss national strategies for prevention of the disease. Since Uruguay is a small country where almost all beekeepers are registered, Uruguayan experience can be useful to be applied in other countries.

Presence of Nosema ceranae in honeybees (Apis mellifera) in Uruguay.

The microsporidium Nosema ceranae is an emergent pathogen of European honeybees Apis mellifera. Using a PCR-RFLP diagnosis, 29 samples of infected honeybees obtained in 2007-2008 (N=26), 2004 (N=2) and before 1990 (N=1) were analyzed for the presence of Nosema apis and N. ceranae. Only N. ceranae was found in all samples, indicating that this species dispersed to Uruguay (and likely the region) at some time before 1990. The presence of N. ceranae in Uruguay is not associated with an increase of Nosemosis, and its role in colony loss seems to be irrelevant.

Efficacy of natural propolis extract in the control of American Foulbrood.

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), a severe disease that affects larvae of the honeybees. Due to the serious effects associated with AFB and the problems related to the use of antibiotics, it is necessary to develop alternative strategies for the control of the disease. The aim of the present work was to evaluate the effect of a propolis ethanolic extract (PEE) against P. larvae and its potential for the control of AFB. In vitro activity of PEE against P. larvae isolates was evaluated by the disk diffusion method and the minimum inhibitory concentration (MIC) was determined. Toxicity for honeybees was evaluated by oral administration of PEE and its lethal concentration was assessed. Lastly, colonies from an apiary with episodes of AFB on previous years were divided into different groups and treated with sugar syrup supplemented with PEE by aspersion (group one), sugar syrup by aspersion (group two), fed with sugar syrup supplemented with PEE (group three) and fed with sugar syrup only (group four). All isolates were sensitive to PEE and the MIC median was 0.52% (range 0.32-0.64). PEE was not toxic for bees at least at 50%. Field assays showed that 21 and 42 days after the application of the treatments, the number of P. larvae spores/g of honey was significantly lower in colonies treated with PEE compared to the colonies that were not treated with PEE. To our knowledge, this is the first report about the use of propolis for the treatment of beehives affected with P. larvae spores.

Agricultural pesticides and veterinary substances in Uruguayan beeswax.

Over the last decade, Uruguay has expanded and intensified its rainfed crop production. This process has affected beekeeping in several ways: for example, by reducing the space available. This has increased the density of apiaries, the risk of varroosis and acaricide use. Additionally, the dominance of no-tillage crops has increased the frequencies of application and of loads of pesticides in regions where such crops share the land with beekeeping and honey production. Therefore, the exposure of bees to xenobiotics (agricultural pesticides and veterinary products) has increased in line with pollution of hives and their products. To document pollution from hive exposure to pesticides, we surveyed the presence of 30 xenobiotics normally used in Uruguay, in recycled beeswax (RB) and in honey cappings (HC) from the main Uruguayan beekeeping regions. There was contamination of all the analyzed samples (RB and HC) with the herbicide atrazine at a range of 1-2 ng g-1. At least three or four additional xenobiotics were detected: insecticides (chlorpyrifos-ethyl and thiacloprid); fungicides (azoxystrobin and tebuconazole); and veterinary products (coumaphos, ethion, and tau-fluvalinate). The frequency of detection of chlorpyrifos-ethyl and coumaphos in RB samples was higher than in those of HC. Moreover, the concentrations of azoxystrobin, coumaphos, and tebuconazole in RB samples were higher than in HC samples. Therefore, we suggest the use of HC to produce recycled printed beeswax films for use in hives to minimize pollution transfer.