Nosemosis Prevention and Control

Nosemosis is a serious microsporidian disease of adult European honey bees caused by the spore-forming unicellular fungi Nosema apis and Nosema ceranae. In this paper we describe the currently known techniques for nosemosis prevention and control including Good Beekeeping Practices (GBPs) and biosecurity measures (BMBs). Topics such as queen renewal, nosema-resistant bees and hygienic and control methods are described. Strong efforts are currently provided to find more a sustainable solution than the use of antibiotics. So far, it seems that the best way to approach nosemosis is given by an “integrated pest management strategy”, which foresees the contemporary application of different, specific GBPs and BMBs.

Molecular Detection of Nosema spp. in Honey in Bulgaria

Environmental DNA (eDNA) analysis is related to screening genetic material of various organisms in environmental samples. Honey represents a natural source of exogenous DNA, which allows for the detection of different honey bee pathogens and parasites. In the present study, we extracted DNA from 20 honey samples from different regions in Bulgaria and tested for the presence of DNA of the ectoparasitic mite Varroa destructor, as well as Nosema apis and Nosema ceranae. Only Nosema ceranae was detected, showing up in 30% of all samples, which confirms the widespread prevalence of this pathogen. All positive samples were found in plain regions of the country, while this pathogen was not detected in mountainous parts. None of the samples gave positive amplifications for the Nosema apis and Varroa mite. The obtained results from this study confirm previous observations that eDNA contained in honey is a potent source for effective biomonitoring of actual diseases in the honey bee.

Nosema Ceranae Interactions with Nosema apis and Black Queen Cell Virus

Nosema ceranae is a relatively new pathogen of the honeybee (Apis mellifera) and the course of type C nosemosis (the disease that it causes) is not entirely known. In order to better understand the course and the consequences of this disease, laboratory experiments were performed. They aimed to compare the course of N. ceranae infection with the course of Nosema apis infection, taking its influence on the black queen cell virus (BQCV) into account. Determination of the quantity of N. ceranae and BQCV genetic material in laboratory tests was performed using real-time PCR. In mixed Nosema infections, N. ceranae “wins” the competition and manages to outnumber N. apis significantly. BQCV exacerbates the course of both A and C nosemoses, but the data shows that in the case of nosemosis C and this viral infection, the mortality rate was the highest from all examined groups. Obtained results show that N. ceranae is more pathogenic for A. mellifera than N. apis, and the course of type C nosemosis is much heavier, which results in the shortened life spans of bees, and in connection with BQCV it becomes even more dangerous to bees.

Study on Major Parasitic Diseases of Adult Honeybees in Three Districts of Kaffa Zone, Southern Ethiopia

Background and Methods. Since regular and timely control of all factors that endanger honeybee life and threaten their products is needed for effective apiculture, cross-sectional research was performed in the three districts (Bonga, Chena, and Gimbo) of the Kaffa Zone to assess the prevalence of major honeybee diseases. A total of 384 honeybee samples from 15 operating apiaries were chosen from each kebele based on their ability to provide a bee sample and the apiary farm’s accessibility. From each district, 128 bee colonies were selected from different apiaries; of these, there were 209 transitional, 74 traditional, and 101 modern hives. Results. Out of 384 samples, the overall prevalence of small hive beetle, Nosema apis, and amoeba (Malpighamoeba mellificae) diseases was 39%, 45.3%, and 40.3%, respectively. The overall prevalence of these three diseases was ascertained, with a statistically significant ( p < 0.05 ) variation in the overall prevalence of N. apis disease and amoeba (M. mellificae) disease between hive type and agroecologies. Conclusion. The research indicates that N. apis, M. mellificae, and small hive beetle are the major parasites that affect honeybees in the study area. In order to classify and describe honeybee diseases and pests associated with Ethiopia’s local honeybees, several field diagnostic surveys and laboratory research works need to be performed.

Nosemosis en colmenas de abejas africanizadas (Apis mellifera) en las condiciones tropicales de Costa Rica: Nosema apis o Nosema ceranae

Se estudió la presencia del microsporidio Nosema spp. en colmenas de abejas africanizadas en Costa Rica. Se seleccionaron un total de 75 muestras de abejas adultas de diferentes zonas apícolas del país, para el diagnóstico molecular de nosemosis. Previamente a la prueba de PCR, las esporas de Nosema spp. se identificaron morfológicamente con el microscopio de luz a un aumento de 40x. Con base en el análisis molecular, se determinó que la mayoría de abejas estaban infectadas con Nosema ceranae, aun cuando las colmenas no mostraban signos clínicos de la infección durante el periodo de muestreo. Por otra parte, ninguna de las muestras estaba infectada con Nosema apis. Un hallazgo para resaltar es que un 29.3% de las muestras de abejas resultaron negativas a nosemosis mediante el examen de PCR. El origen de las abejas, las cuales se colectaron de apiarios ubicados en cuatro de las siete provincias de Costa Rica, indica que el microsporidio N. ceranae está ampliamente distribuido en las principales zonas apícolas del país. Aún no se conoce con exactitud las consecuencias patológicas de la presencia de N. ceranae en colmenas de abejas africanizadas. Sin embargo, debido a la pérdida de abejas melíferas reportada en Europa, relacionada a infecciones de microsporidios, la virulencia de N. ceranae en abejas africanizadas debe ser estudiada.

Application of Herbal Essential Oil Extract Mixture for Honey Bees (Apis mellifera L.) Against Nosema ceranae and Nosema apis

In recent years, interest in herbal essential oil extracts for the treatment of nosemosis has steadily increased. The great importance of this study is in evaluating and validating the synergistic effect caused by the mixture of different herbal extracts. The aim of the study was to investigate through cage experiments and field studies the effect of mixed herbal essential oil extracts and to determine the most suitable application methods and doses of the product in the treatment of nosemosis. The duration of the experiments was three weeks. Results show that the herbal essential oil extract mixture (HEOEM) is effective on both Nosema apis and Nosema ceranae, and on the two together (mixed infection). With respect to application methods, the results revealed that the most suitable method is spraying HEOEM with sterilized distilled water on adult bees and on both sides of frames; 500 µL per cage and 2,000 µL per frame were found to be effective doses of HEOEM in the experimental cages and hives. HEOEM can be a viable alternative to synthetic products in the immediate future as the contents are natural and have no toxic effect on honey bees.

Variation in the Distribution of Nosema Species in Honeybees (Apis mellifera Linnaeus) between the Neighboring Countries Estonia and Latvia

The unicellular spore-forming parasites Nosema apis and Nosema ceranae are considered to be one of the causes of increased honey bee mortality in recent years. These pathogens attack their honey bee hosts through their gut, causing changes in behavioral stress responses and possibly resulting in decreased honey yield and increased honey bee mortality. The present study aimed to determine the prevalence of Nosema spp. (nosemosis) in Estonia and Latvia, as well as the persistence of the disease in previously infected hives. Currently, N. ceranae is considered the most virulent species and is predominant worldwide. However, in some regions, usually with colder climates, N. apis is still prevalent. To achieve better disease control, it is important to determine the species distribution. For this purpose, we selected 30 apiaries in Estonia and 60 in Latvia that were positive for Nosema spp. in the EPILOBEE (2012–2014) study, which was 5 years prior to the present study. The results show that, while both species are present in Estonia and Latvia, N. apis is dominant in Estonia (43%), and N. ceranae is dominant in Latvia (47%). We also found that the pathogens are very persistent, since 5 years later, only 33% of infected apiaries in Estonia and 20% of infected apiaries in Latvia, we could not detect any pathogens at the time of sampling.

Evaluating Efficacy of Fumagilin-B® Against Nosemosis and Tracking Seasonal Trends of Nosema spp. in Nova Scotia Honey Bee Colonies

The efficacy of the antimicrobial Fumagilin-B® against nosemosis was evaluated in both spring and autumn feeding treatments following label directions in seventy-two honey bee (Apis mellifera) colonies across three apiaries in Nova Scotia, Canada. The seasonal trend of Nosema spp. spore loads was also tracked in these same colonies throughout a thirteen-month period (February 2018 – March 2019). We found the spring Fumagilin-B® treatment to be effective at significantly suppressing Nosema spp. spore levels below the recommended treatment threshold. There was no effect of Fumagilin-B® treatment in the autumn based on low spore levels at this time. We detected a drastic increase in Nosema spp. spore loads as May progressed but a decline in spores in summer (June–September). By October, there was another increase in spore levels, but this increase did not exceed the economic treatment threshold. Across seventeen collection periods in both control and Fumagilin-B® colonies, 74% (25) of samples tested positive for Nosema ceranae, while 26% (9) contained no Nosema spp. spores. No Nosema apis spores were detected during this trial. Our results indicate that Fumagilin-B® is an effective management practice in the spring, but colonies should still be monitored in the autumn. Our data also support that the Nosema species profile is shifting to be exclusively N. ceranae and the treatment threshold for Fumagilin-B® may need to be updated to reflect this, as the threshold was originally developed for N. apis.

Nosema ceranae (Microspora: Nosematidae): A Sweet Surprise? Investigating the Viability and Infectivity of N. ceranae Spores Maintained in Honey and on Beeswax

Nosema disease is a prominent malady among adult honey bees [Apis mellifera L. (Hymenoptera: Apidae)], caused by the microsporidian parasites, Nosema apis Zander (Microspora: Nosematidae) and N. ceranae Fries et al. 1996. The biology of N. apis is well understood, as this parasite was first described over a century ago. As N. ceranae is an emerging parasite of the honey bee, we do not yet understand how long spores of this parasite survive in honey bee colonies, or all the potential modes of transmission among bees. We investigated the viability and infectivity of N. ceranae spores in honey and on beeswax over time after exposure to 33, 20, −12, and −20°C. Spores in honey maintained viability at freezing temperatures for up to 1 yr and remained viable considerably longer than those on beeswax. Based on this evidence, honey may act as an important reservoir for infective spores to initiate or perpetuate N. ceranae infections in honey bee colonies. This work provides information that may help enhance current management recommendations for apiculturalists.