27 de febrer 2015



Les abelles africanes gaudeixen d'una bona salut, restant lliures de les plaques de paràsits que estan provocant una disminució terrible i preocupant de les seves colònies.

Hom es pregunta a què es deu aquest fet, i la resposta sembla ser deguda a la presència de pesticides en l'ambient. Els estudis realitzats constaten que la concentració de productes químics en l'ambient a l'Àfrica són rerelativament baixos, i que això permetria a l'abella africana gestionar-se la seva pròpia salut, com ho ha estat fent de forma natural en els darrers milions d'anys d'evolució. 

La combinació d'aquest factor mediambiental i la pròpia aptitud higiènica de l'abella africana, podrien ser l'explicació de la resistència momentània davant els principals paràsits de l'abella de la mel.

Font: apisuk.com

Article en anglès
If you really want to say goodbye to varroa and other pests and pathogens, simply use African bees. Several parasites and pathogens that devastate honeybees in Europe, Asia and the United States are spreading across East Africa, but do not appear to be impacting native honeybee populations at this time, according to an international team of researchers. The invasive pests include including Nosema microsporidia and Varroa mites.
East African honeybees appear to be resilient to these invasive pests, which suggests that the chemicals used to control pests in Europe, Asia and the United States currently are not necessary in East Africa say researchers in the Department of Biological Sciences, South Eastern Kenya University, and researcher at the International Centre of Insect Physiology and Ecology, Kenya.

The team first discovered Varroa mites in Kenya in 2009. This new study also provides baseline data for future analyses of possible threats to African honeybee populations.

Kenyan beekeepers believe that bee populations have been experiencing declines in recent years, but research results suggest that the common causes for colony losses in the United States and Europe — parasites, pathogens and pesticides — do not seem to be affecting Kenyan bees, at least not yet. Some preliminary data suggest that the loss of habitat and drought impacting flowering plants, from which the bees get all their food, may be the more important factor driving these declines.

In 2010, the researchers conducted a nationwide survey of 24 locations across Kenya to evaluate the numbers and sizes of honeybee colonies, assess the presence or absence of Varroa and Nosema parasites and viruses, identify and measure pesticide contaminants in hives and determine the genetic composition of the colonies.

This is the first comprehensive survey of bee health in East Africa, where researchers have examined diseases, genetics and the environment to better understand what factors are most important in bee health in this region. The results appeared in April 17 PLOS ONE.

The researchers found that Varroa mites were present throughout Kenya, except in the remote north. In addition, Varroa numbers increased with elevation, suggesting that environmental factors may play a role in honeybee host-parasite interactions. Most importantly, the team found that while Varroa infestation dramatically reduces honeybee colony survival in the United States and Europe, in Kenya, its presence alone does not appear to impact colony size.

The scientists found Nosema at three sites along the coast and one interior site. At all of the sites, they found only a small number of pesticides at low concentrations. Of the seven common honeybee viruses in the United States and Europe, the team only identified three species, but, like Varroa, these species were absent from northern Kenya. The number of viruses present was positively correlated with Varroa levels, but was not related to colony size.

The Africanized bees — the so-called ‘killer bees’ — in the Americas seem to be having no problem with Varroa or diseases, they may have some innate genetic tolerance to these pests. There is a seemingly greater tolerance of African bees to these pests is a combination of genes and environment.”

Given their findings that African honeybees currently appear to be resilient to the effects of parasites and viruses, the researchers recommend that beekeepers in East Africa maintain healthy bee populations by protecting vital nesting habitat and the native flowering plant diversity that the bees depend on for food. In addition, the researchers suggest that beekeepers use pesticides sparingly.

This research is important because it confirms the resilience of African bees, despite the heavy presence of recently introduced Varroa mites, and it suggests that the approach to manage these pests should not follow the application of pesticides as has been done in the western. These newly introduced pests to Africa might have long-term implications for the honeybee populations. As these new parasites and pathogens become more widespread, as pesticide use increases and as landscape degradation increases due to increased urbanization, farming and climate change, researchers expect to see the combination of all these factors negatively impact the bees in the future.

Article Source:
The above story is based on materials provided by Penn State. The original article was written by Sara LaJeunesse. Note: Materials may be edited for content and length.

Elliud Muli, Harland Patch, Maryann Frazier, James Frazier, Baldwyn Torto, Tracey Baumgarten, Joseph Kilonzo, James Ng’ang’a Kimani, Fiona Mumoki, Daniel Masiga, James Tumlinson, Christina Grozinger. Evaluation of the Distribution and Impacts of Parasites, Pathogens, and Pesticides on Honey Bee (Apis mellifera) Populations in East AfricaPLoS ONE, 2014; 9 (4): e94459 DOI:10.1371/journal.pone.0094459