Determination of spore longevity and viability of Nosema apis and Nosema ceranae according to storage conditions

Abstract

Honey bee colonies are often infected with Nosema apis and Nosema ceranae which cause adult honey bee disease called nosemosis. All honey bee colony members can be infected with these species. In addition, it is claimed to be the main cause of honey bee winter losses in many countries. Nosema spores are expected to resistant the environmental conditions and their infectivity continues for a long time because of long-term durability of fungal spores. In this study, the viability of Nosema spores were investigated in terms of storage situations under laboratory conditions. Honey bee samples that were collected from apiaries in 2011 were investigated to detect the presence of Nosema species with real-time PCR amplification studies. After determination of Nosema species, each sample was divided in two groups. One of these groups was used to find Nosema spore concentration. Nosema solutions were divided and stored at both -20°C and +4°C. The spore concentration was measured every year in the period 2011-2015. Other group of honey bee samples was also stored at -20°C and every year was used for Nosema spore counting. Furthermore, it was examined the infectivity of Nosema spores with sugar solutions which obtained each sample using cage experiment techniques. According to results, when we compare the solutions annually, there is no change at Nosema spore concentration of the solution in -20°C and honeybee samples in -20°C. But reduction was seen at Nosema spore concentration of the solution in +4°C. Nosema spore infectivity tests revealed that infectivity of Nosema spores has not changed significantly between 2011 and 2015. This is the first time mixed Nosema spores found more infective than one-type spore after prolonged exposure to different conditions.