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Nosemosis, is caused by two microsporidian species: Nosema apis and N. ceranae. In the last decade there has been rapid development and spread of bee diseases, creating serious problems for bee keeping management. The above situation requires a substantial increase in the intensity of research, which would result in a successful means of combating the disease with no risk to the host organism. In recent years, a number of studies were conducted providing new knowledge about the disease, dealing with important issues related to the development, epidemiology and treatment of bees. However, despite this it remains unclear as to the real nature of the organisms that cause nosemosis, nor what is their structure and biology. The issues raised above have obligated the authors to a brief summary of current knowledge both about the disease, as well as its perpetrators. It has been proposed to amend certain terms that should be used when describing the structures and phenomena associated with pathogenic species and the course of the process of pathogenesis. The article draws attention to some important issues that summarize and organize existing knowledge, also indicates problems which should be the subject of future research.
Nosemosis is serious and widespread bee disease connected with Collony Colapse Disorder (CCD). Monitoring of this disease is crucial to a better understanding of the effect of this disease on the health in both individual bees and at the whole colony level. There is little information about nosemosis in different parts of Poland, which have distinct beekeeping management and climate conditions. It is also important to have quick and easy methods of differentiation of the type of nosemosis (type A - caused by Nosema apis and C - by N. ceranae). Therefore the aims of the study was to determine the degree of Nosema spp. infection amount in the Lublin region during the course of 7 years and to find morphometric parameters which could help to distinguish the differences between spores of N. apis and N. ceranae. In the Lublin region the amount of nosemosis infection has risen from the year 2001 to 2008, with the highest infection scores in 2008. This decreasing number of healthy colonies probably provides evidence of the impact of the greater frequency of N. ceranae infection, which could be the one of the causes of CCD. Scanning Electron Microscopy (SEM) reveals that N. apis and N. ceranae spores differ in their surface structure. Generally, spores of N. ceranae seemed to be more sculptured with deeper ornamentation than those of N. apis. Therefore ornamentation of the spores cell walls with special reference to their area can be considered as a taxonomic criterion for separating these two Nosema taxa.
Nosema spp. spores are extremely resistant to external stress factors and can survive several years without losing the ability for further infection within the insect body. For this reason, combating nosemosis is difficult. Some beekeepers add ethanol to the sucrose solution before the winter to prevent nosemosis infection and to cure already infected colonies. Others feed infected colonies with herbal ethanol extracts. Therefore the aim of this study was to evaluate the ethanol impact on bees infected with Nosema spp. Four groups of uninfected and Nosema spp. infected bees were fed with sugar-water syrup (1:1) supplemented with ethanol at the following concentrations: 10%, 5% and 2.5% and 0% as a control (only a sucrose syrup). Generally, bees consumed 10% EtOH solution in an amount even 50% lower than in other concentrations. The impact of EtOH on the increase of bees’ mortality was observed at a 10% EtOH concentration for healthy bees and even from 5% EtOH concentration for Nosema spp. infected bees. In our study the highest number of Nosema spp. infestation was noticed for bees fed with 5% EtOH and the lowest pH level was also measured for this group of bees. Therefore, a clear correlation was observed between the feeding bees with EtOH, which resulted in the acidification of bees, and the degree of Nosema spp. infestation. A synergistic effect of the ethanol and nosemosis on the rise of the mortality of bees has been observed. The addition of ethanol to sucrose syrup facilitates conditions for the development of nosemosis in honey bees. The strongest effect of ethanol on the level of Noseama spp. infection was observed for the 5% ethanol solutions. Moreover, ethanol at 10% concentration in sugar syrup exerts severe toxic effects even on healthy bees. All these factors induced immune-suppression in bees and enhanced the level of Nosema spp. infestation.
Nosemosis is a serious honeybee disease linked to Colony Collapse Disorder (CCD). It cause many changes at the individual bee level, which also affects the health of the entire bee colony. N. ceranae and N. apis are not tissue specific as was previously thought and besides the ventriculus epithelium their spore are also present in other tissue, such as Malpighian tubules, hypopharyngeal glands, salivary glands, and fat bodies. Emplacement of nosema infection in honeybee glands interferes with the production of the royal jelly, honey, bee bread. Moreover spores remaining in the honeybee glands are a potential reservoir of infection. The aim of the research was to determine the correlation among the number of Nosema spores in whole bees, as well as in their ventriculus and hypopharyngeal glands. Nosema-infected honey bees were collected in the spring, when there should be a comparable degree of Nosema infection level in all tissues. Three independent experiments were conducted. In these studies the number of spores in the hypopharyngeal glands was the lowest and the highest results were observed for ventriculus samples. A large number of spores in the hypopharyngeal glands was also observed. This can be the cause of a reduction or loss of these glands’ function; moreover, it may increase the horizontal transmission of the infection within a hive as well as to a queen bee.
Intestinal microflora is a very important part of the digestive system in every animal, and plays a role in the synthesis of vitamins and the metabolism of many toxic chemical compounds. The indigenous intestinal flora of bees changes even as a result of changing their diet from natural to artificial or placing them in cages. Such factors have an impact on the health of bees and on the strength of whole colonies. In our study, intestinal fungi isolated from healthy bees and from bees infected with Nosema spp. belonged to two genera: Candida and Saccharomyces. The approximate numbers of yeast CFUs (colony forming units) obtained from healthy Apis mellifera carnica and Buckfast bees were, respectively, 2880-5180 and 1056-4120. Apis mellifera carnica and Buckfast bees were similarly sensitive to slight Nosema spp. infections, but heavy infestations had a greater impact on the intestinal microflora of A. m. carnica. The degree of Nosema spp. infestation had an impact on the quantitative composition of the intestinal microflora of bees. Slightly infected bees of Apis mellifera carnica had up to 44 915 yeast CFUs per bee, and Buckfast bees up to 28 705 yeast CFUs per bee. Surprisingly, a heavy infestation reduced the number of yeast CFUs to no more than 120 in A. m. carnica bees and to no more than 164 in Buckfast bees. Therefore, in studies in which the number of yeast CFUs is used as the main indicator of stress in bees, the potential presence and the degree of Nosema spp. infestation needs to be taken into account.
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