Background
Nosema apis is a serious disease of adult honey bees. It has been reported to cause significant production losses as a result of a range of effects on adult bee longevity, queen bees, brood rearing, bee biochemistry, pollen collection and other bee behaviour. Despite these effects there are no classic signs of infection and hence most infections are unrecognised. There is no comprehensive current data on the prevalence of nosema disease in bees in Australia and no work which links nosema disease with beekeeper management practices.

Aims/Objectives
The aims of this project were to provide a literature review and a three year survey of Nosema apis linked with management practices.

Methods used
The literature review was prepared from information obtained from relevant literature, some of which was obtained from computer searches.

The N. apis survey was carried out over a period of three years. Each year adult bee samples (25 bees per hive) were collected from about 800 hives owned by 20 beekeepers (40 hives per beekeeper).

These samples were collected in the August of 2004, 2005 and 2006 while beekeepers from New South Wales, Victoria, Queensland and South Australia were using their bees to pollinate almond trees at Robinvale, Victoria. Bee samples were examined for N. apis spores using standard techniques. The participating beekeepers were asked to complete a questionnaire which was analysed in relation to the N. apis counts detected in their bees.

Results
The literature review is provided in the first section of the report. It provides details on the cause, occurrence, multiplication and spread, and effects on adult bees and honey bee colonies. Information is also provided on the diagnosis, factors affecting nosema spore counts and control methods. The section on diagnosis has been described in sufficient detail so that beekeepers can determine the level of infection in their hives using simple light microscopy and apply appropriate management strategies to minimise infection levels. A description of a new Nosema species Nosema ceranae, which has recently been identified in the European honey bee in the USA, Taiwan and Europe has also been included.

The three-year survey demonstrated that N. apis was present in every apiary in each of the three years.

However, there was great variation in the average nosema spore counts for the three year period.

These counts ranged from 12,236,000 to 10,000 spores per bee and the number of infected hives ranged from 40 (100%) to 1 (2.5%) per apiary.

Key findings of the survey were; (i) hive manipulation (including supplementary feeding) were related to increased spore counts, (ii) the adult bee population in hives with very high nosema spore counts decreased or stagnated while the bees were pollinating almonds, indicating a reduced pollination efficiency of those hives, (iii) low nosema spore counts were associated with hives which were packed down tight for winter and were full or nearly full of honey, (iv) there was a clear relationship between colonies that were working spotted gum and high nosema spore counts, (v) some flora which are associated with poor pollen production, e.g. grey box and iron bark, were used by beekeepers who had both high and low nosema spore counts, indicating that factors other than floral type were involved in determining the levels of nosema spore counts and (vi) in some apiaries heavily infected with nosema spores, N. apis spores were not detected in one, three or four of the 40 hives examined, suggesting that there may be specific unrecognised factors which impart resistance to this disease in those hives.

No assessment was made on the importance of queen age or comb replacement, as most beekeepers used queens which were less than 12 months old and had a comb replacement strategy in place.

Implications for relevant stakeholders
Nosema apis was identified as an important parasite of adult honey bees in the literature review. The disease it causes, nosema disease, may result in significant production losses as a result of its effects on adult bee longevity, queen bees, brood rearing, bee biochemistry, pollen collection and other bee behaviour. The degree of loss in an individual bee colony is a function of environmental conditions and beekeeper management - strategies at critical times in the infection cycle. Unfortunately, there are no clear typical signs of nosema disease which allow easy confirmation of infection. The literature review provides a step-by-step procedure for the detection of N. apis spores using standard light microscopy. This is an option that beekeepers can use to access whether the infection is present and the degree of infection. N. apis spores are much larger than bacterial spores and can be readily identified using relatively low magnifications (X 200-X 400) compared to infections such as European and American foulbroods which require high magnification (X 1000) for identification and are more complicated to diagnose than nosema disease. A number of control options have also been listed in the literature review which can help reduce the impact of this disease.

The three-year survey clearly demonstrated that N. apis is commonly found in bees in Australia. It also demonstrated that there is a broad range of infection levels within apiaries and that there are management practices which can be used to minimise the effects of disease. Beekeepers need to consider their management strategies especially in autumn and winter as these are the critical times when nosema levels can rapidly increase and cause bee and production losses. The benefits of working autumn and winter flows should be weighed against not, or reduced working of bees, which would result in better bee health for spring.

No severe losses of bees or loss of hives due to nosema disease were reported in this study probably due to the generally dry weather that was experienced from 2004-2006. However, severe losses due to nosema disease have been previously reported. Had conditions been suitable for the development of nosema disease it is likely that the beekeepers with high nosema spore counts would have suffered significant losses. By minimising hive manipulation and maintaining a high nutritional plain for hives, nosema spore counts will be kept down, reducing the possibility of large bee losses in the event that conditions favour the proliferation of nosema spores.

Recommendations
Beekeepers can influence nosema spore counts in their bee colonies by using appropriate management strategies. Beekeepers working autumn and/or winter flows will increase nosema spore counts in their bees. The economic benefit of working these flows should be evaluated against not working such flows which would provide bees with low counts and a better health status at the beginning of spring.

One tool that beekeepers can use to gauge the progress of nosema disease is to examine their bees microscopically for the presence of spores at critical times of the N. apis cycle. Being aware of the level of infection can assist in making management decisions which can influence strategies that may affect the development of nosema disease.