Abstract
Two species of microsporidia, Nosema apis and Nosema ceranae, are obligate intracellular parasites that are widespread in the world and cause the infectious disease (Nosemosis) of the Western honey bee Apis mellifera. Information on the prevalence and distribution of Nosema species in North Asia conditions is scarce. The main aim of the present study is to determine the prevalence of Nosema spp. (Nosemosis) in honey bees inhabiting some inland regions of North Asia (Western and Eastern Siberia, Altai Territory, Russia, and northeastern part of Kazakhstan). The objective of the paper is also to assess the influence of climatic factors on the spread of N. ceranae. Eighty apiaries in four ecological regions of North Asia (southern taiga, sub-taiga zone, forest steppe, and mountain taiga forests) were investigated with regard to distribution, prevalence, and diversity of Nosema infection in honey bees using duplex-PCR. Nosema infected bees were found in 65% apiaries of ecoregions studied, and coinfection was predominant (36.3% of Nosema-positive apiaries). Both N. apis and N. ceranae occur across subarctic and warm summer continental climates, but while N. apis predominates in the former, N. ceranae is more predominant in the latter. No statistically significant differences in Nosema distribution were identified in various climatic zones. In the sub-taiga zone (subarctic climate), low presence of colonies with pure N. ceranae and a significantly higher proportion of coinfection apiaries were revealed. Long-term epidemiological study of Nosema spp. prevalence in the sub-taiga zone showed a surprising percentage increase of Nosema-positive apiaries from 46.2% to 74.1% during 2012–2017. From 2012 to 2015, N. apis became a predominant species, but in 2016–2017, the coinfection was mainly detected. In conclusion, the results of this investigation showed that N. ceranae is widespread in all study ecoregions of North Asia where it exists in combination with the N. apis, but there is no replacement of N. apis by N. ceranae in the studied bee populations.
Highlights
In Western honey bees, two species of Microsporidia causing nosemosis have been described: Nosema apis Zander, 1909 [1] and Nosema ceranae Fries et al, 1996 [2]
In all the ecoregions of North Asia studied, two species of Microsporidia were registered in honey bees: N. apis and N. ceranae
The geographic distribution of Nosema spp. in several ecoregions of North Asia can be represented as follows: The presence of bee colonies infected with pure N. ceranae in all the study ecoregions; No significant differences were identified in the incidence of Nosema infection between subarctic and warm summer continental climates
Summary
In Western honey bees, two species of Microsporidia causing nosemosis have been described: Nosema apis Zander, 1909 [1] and Nosema ceranae Fries et al, 1996 [2]. 2020, 7, 111 parasite of the Eastern honey bee Apis cerana in 1996 [2]. The parasite N. apis, responsible for nosemosis type A, is characterized by moderate virulence (mainly nosemosis is accompanied by dysentery), and bee colonies can often cure themselves under favorable environmental conditions [3,6]. For N. ceranae, a relatively new parasite for the A. mellifera, data on the virulence, the prevalence in different climates, as well as the role and effect on the viability and survival of bee colonies are contradictory [14,19,25,26,27,28,29,30]
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