The effects of various antimicrobials and supplements on the expression of immune-related genes, oxidative stress and survival of honey bee Apis mellifera infected with microsporidium Nosema ceranae

Abstract

Nosema ceranae is a microsporidian endoparasite of the European honey bee, Apis mellifera, and the dominant Nosema species in Southeast Europe. Depending on the infection level it could have significant consequences on bees, their health and productivity. The impact of N. ceranae on honey bees’ immunity has been particularly investigated in recent years. Some conclusions of this research underline N. ceranae-induced suppression of immune-related genes, proving its immunosuppressive impact. Treatment for nosemosis includes the use of the antibiotic fumagillin. Fumagillin has proven effect in Nosema control, but its side effects may pose a problem for the bees and the quality of their products, which is why its application in many countries have been limited. Hence, researchers are constantly looking for natural and synthetic components which could be suitable substitutes for fumagillin. Many products have been tested and plant/algae extracts and synthetic vitamin-mineral complexes showed the best effects. This laboratory (cage) experiment included testing of five products: (1) antibiotic fumagillin (2) a plant extract - thymol, and three dietary supplements: (3) a commercial amino acid and vitamin complex named Beewell AminoPlus, (4) a commercial mixture of oak bark, sage and absinth extracts named Medenko forte, and (5) a polysaccharide extract of Agaricus blazei mushroom. Bees in all treatment groups were infected with N. ceranae spores on day 3, and treated with the listed products from day 1, 3 or 6 after emergence. Bee survival, Nosema loads, levels of immune-related genes (abaecin, apidaecin, hymenoptaecin, defensin and vitellogenin) expression and the level of oxidative stress, assessed through the activity of antioxidative enzymes (catalase, glutathione S-transferase and superoxide dismutase) and the concentration of malondialdehyde, were measured in all experimental groups. The obtained values were compared with those of control (noninfected and infected) groups...

Nosema ceranae je mikrosporidija koja parazitira kod Evropske medonosne pčele, Apis mellifera, i dominantna je vrsta roda Nosema u jugoistočnoj Evropi. U zavisnosti od stepena infekcije i perioda godine, ovaj endoparazit može imati dalekosežne posledice po pčele, njihovo zdravlje i produktivnost. Poslednjih godina posebno je istraživan uticaj N. ceranae na imunitet pčela a zaključci pojedinih istraživanja izdvajaju efekat supresije gena značajnih za imunitet pčela, odnosno dokazuju imunosupresivne posledice infekcije vrstom N. ceranae. Terapija nozemoze podrazumeva upotrebu antibiotika fumagilina, koji ima dokazanu efikasnost u suzbijanju infekcije ali njegovi sporedni efekti mogu predstavljati problem za same pčele i kvalitet pčelinjih proizvoda, te je stoga je njegova primena u mnogim zemljama ograničena. Imajući ovo na umu konstantno se traga za prirodnim i sintetskim komponentama koje bi bile zamena za fumagilin. Testirane su mnoge supstance, a među onima koje su pokazale najbolji efekat izdvajaju se ekstrakti biljaka i algi i sintetske vitaminsko-mineralne mešavine. U ovom radu je u kaveznom eksperimentu testirano pet preparata: (1) antibiotik fumagilin, (2) biljni ekstrakt timol; i tri aditiva u ishrani pčela: (3) komercijalni preparat Beewell AminoPlus koji predstavlja vitaminsko-aminokiselinsku mešavinu, (4) komercijalni preparat Medenko forte koji sadrži ekstrakte hrastove kore, pelena i žalfije i (5) polisaharidni ekstrakt gljive Agaricus blazei. Pčele su u svim tretiranim grupama trećeg dana života inficirane sporama N. ceranae, a različite grupe su tretirane preparatima od prvog, trećeg i šestog dana. Kod tretiranih pčela je praćen efekat na preživljavanje pčela, stepen Nosema infekcije, nivoe ekspresije gena značajnih za imunitet pčela (abecin, defenzin, himenoptecin, apidecin i vitelogenin) i nivo oksidativnog stresa praćen kroz aktivnost antioksidativnih enzima (katalaze, superoksid dizmutaze i glutation S-transferaze) i koncentracije malondialdehida...