Influence of urbanisation on the prevalence of protozoan parasites of bumblebees

1. Increasing urbanisation is often cited as a cause of declining biodiversity, but for bumblebees there is evidence that urban populations of some species such as Bombus terrestris L. may be more dense than those found in agricultural landscapes, perhaps because gardens provide plentiful floral resources and nesting opportunities. 2. Here we examine the influence of urbanisation on the prevalence of the main protozoan parasites of bumblebees in west central Scotland. We would expect transmission rates and prevalence of parasites to be higher in high density host populations, all else being equal. 3. Workers of two bee species, B. terrestris and B. pascuorum, were sampled over a 45‐day period in mid to late summer, and parasites were detected in faeces and via dissection. A comparison of the two methods suggests that faecal sampling is considerably less sensitive than dissection, failing to detect infection in 27.8%, 55.1%, and 80% of cases of infection with the parasites Crithidia bombi, Nosema bombi, and Apicystis bombi, respectively. 4. For all three parasites, broad patterns of prevalence were similar, with prevalence tending to increase with urbanisation in B. terrestris but not in B. pascuorum. The different patterns of seasonal prevalence in the two bee species suggest that intraspecific transmission is more important that interspecific transmission. 5. Our observation of greater parasite prevalence among B. terrestris in urban compared with rural areas suggests that urban habitats may present greater opportunities for parasite transmission. Greater bee densities in urban areas may be the driving factor; however, further study is still needed. For example, differences in disease prevalence between habitats could be driven by differences in the types and abundance of flowers that are available, or in exposure to environmental stressors.     

基于EB1基因的环介导等温扩增（LAMP）法检测感染家蚕微粒子病的蚕卵

【目的】家蚕 Bombyx mori 微粒子病一直影响着蚕种业的健康发展,快速而准确地检测出寄生于蚕卵中的家蚕微孢子虫 Nosema bombycis 对于有效控制家蚕微粒子病危害意义重大。【方法】环介导等温扩增（loop-mediated isothermal amplification, LAMP）法是一种快速、灵敏、特异的DNA体外恒温扩增方法,本文基于LAMP检测法的原理,依据家蚕微孢子虫孢子繁殖复制相关的 EB1 基因（GenBank登录号：KF421134.1）设计LAMP引物,对LAMP反应体系的最佳反应温度、内外引物浓度比、检测反应的特异性、灵敏度等进行研究,建立了一种检测蚕卵感染家蚕微粒子病的LAMP检测方法。【结果】结果表明,基于EB1 基因建立的LAMP检测方法在63℃恒温下在1.5 h内就可完成对样品的有效检测,本LAMP法对家蚕微孢子虫孢子DNA的检测灵敏度为5.0×10^-3 ng/μL,对EB1-pMD^TM19-T质粒标准品的检测灵敏度为1.0×10² copies/μL,同时对人工感染家蚕微粒子病单个母蛾产下蚕卵的1/8卵圈量或1粒蚕卵均能检出阳性结果。上述结果都分别应用凝胶电泳法、恒温荧光检测仪以及SYBR GreenⅠ显色肉眼观察法得到同步判定。【结论】本研究建立的基于EB1基因LAMP法可用于蚕卵微粒子病的检测,LAMP法为蚕种质量检验及成品卵微粒子病现场检疫提供了新技术。     

Molecular data and phylogeny of Nosema infecting lepidopteran forest defoliators in the genera Choristoneura and Malacosoma

ABSTRACT. Nosema isolates from five lepidopteran forest defoliators, Nosema fumiferanae from spruce budworm, Choristoneura fumiferana ; a Nosema sp. from jack pine budworm, Choristoneura pinus pinus and western spruce budworm, Choristoneura occidentalis ( Nosema sp. CPP and Nosema sp. CO, respectively); Nosema thomsoni from large aspen tortrix, Choristoneura conflictana ; and Nosema disstriae , from the forest tent caterpillar, Malacosoma disstria were compared based on their small subunit (SSU) ribosomal RNA (rRNA) gene sequences. Four of the species sequenced, N. fumiferanae , Nosema sp. CPP, Nosema sp. CO, and N . disstriae have a high SSU rDNA sequence identity (0.6%–1.5%) and are members of the "true Nosema " clade. They all showed the reverse arrangement of the (large subunit [LSU]–internal transcribed spacer [ITS]–SSU) of the rRNA gene. The fifth species, N. thomsoni has the usual (SSU–ITS–LSU) arrangement and is not a member of this clade showing only an 82% sequence similarity. We speculate, therefore, that a genetic reversal may have occurred in the common ancestor to the "true Nosema " clade. Although, the mechanism for rearrangement of the rRNA gene subunits is not known we provide a possible explanation for the localization. N. fumiferanae , Nosema sp. CPP, and Nosema sp. CO clustered together on the inferred phylogenetic tree. The high sequence similarities, the reverse arrangement in the rRNA gene subunits, and the phylogenetic clustering suggest that these three species are closely related but separate species.     

Does fumagillin control the recently detected invasive parasite Nosema ceranae in western honey bees (Apis mellifera)?

Western honey bee (Apis mellifera) colonies in Nova Scotia, Canada were sampled in spring and late summer 2007 to evaluate efficacy of fumagillin dicyclohexylammonium (hereafter, fumagillin) against Nosema ceranae. Colonies treated with fumagillin in September 2006 (n = 94) had significantly lower Nosema intensity in spring 2007 than did colonies that received no treatment (n = 51), but by late summer 2007 no difference existed between groups. Molecular sequencing of 15 infected colonies identified N. ceranae in 93.3% of cases, suggesting that fumagillin is successful at temporarily reducing this recent invasive parasite in western honey bees.     

Action of carbendazim on the development of Nosema bombycis Naegeli in silkworm Bombyx mori L.

Abstract:  Carbendazim, a benzimidazole compound is effective in curing pebrine disease in silkworm, Bombyx mori , caused by Nosema bombycis , if treatment is given within 48 h post-infection or before the parasite establishes itself in the host tissue. Ultrastructural evidence of the action of carbendazim showed an adverse effect of the drug on both merogonic and sporogonic stages of the parasite in the midgut and silk gland of the silkworm. The drug caused elongation, vacuolation and depletion of cytoplasmic contents of the meront, sporont, sporoblast and spore stages of N. bombycis .     

Influence of the forest caterpillar hunter Calosoma sycophanta on the transmission of microsporidia in larvae of the gypsy moth Lymantria dispar

• 1 The behaviour of predators can be an important factor in the transmission success of an insect pathogen. We studied how Calosoma sycophanta influences the interaction between its prey [Lymantria dispar (L.) (Lepidoptera, Lymantriidae)] and two microsporidian pathogens [Nosema lymantriae (Microsporidia, Nosematidae) and Vairimorpha disparis (Microsporidia, Burellenidae)] infecting the prey.
• 2 Using laboratory experiments, C. sycophanta was allowed to forage on infected and uninfected L. dispar larvae and to disseminate microsporidian spores when preying or afterwards with faeces.
• 3 The beetle disseminated spores of N. lymantriae and V. disparis when preying upon infected larvae, as well as after feeding on such prey. Between 45% and 69% of test larvae became infected when C. sycophanta was allowed to disseminate spores of either microsporidium.
• 4 Laboratory choice experiments showed that C. sycophanta did not discriminate between Nosema‐infected and uninfected gypsy moth larvae. Calosoma sycophanta preferred Vairimorpha‐infected over uninfected gypsy moth larvae and significantly influenced transmission.
• 5 When C. sycophanta was allowed to forage during the latent period on infected and uninfected larvae reared together on caged, potted oak saplings, the percentage of V. disparis infection among test larvae increased by more than 70%. The transmission of N. lymantriae was not affected significantly in these experiments.
• 6 Beetles never became infected with either microsporidian species after feeding on infected prey.
• 7 We conclude that the transmission of N. lymantriae is not affected. Because no V. disparis spores are released from living larvae, feeding on infected larvae might enhance transmission by reducing the time to death and therefore the latent period.

     

榆绿毛萤叶甲寄生微粒子虫新种记述：微孢子门：微粒子科

本文记述寄生于榆绿毛萤叶甲的一种微粒子虫新种的光匀和电镜形态特征及寄生习性。并讨论了新种鉴别特性。     

Effect of Paranosema (Nosema) locustae (Microsporidia) on morphological phase transformation of Locusta migratoria manilensis (Orthoptera: Acrididae)

Field and laboratory studies demonstrated that Paranosema (Nosema) locustae had significant effects on the morphological phase transformation of Locusta migratoria manilensis (Meyen 1835). In the field, spraying P. locustae on gregarious locusts caused a substantial population reduction by 16 days after treatment, with most of the surviving locusts being phase solitaria. However, the effects of P. locustae on locust phase transformation began before direct mortality had caused a substantial reduction in locust density: locust numbers were still high at day 10, but locusts had already transformed to phase transiens. Laboratory assays showed that while a low dose of P. locustae had no effect on phase transformation, at a higher dose of 1×10⁵ spores/mL, locusts had F/C ratios that were significantly (P<0.05) more solitaria than untreated locusts, with locusts having ratios that were either phase solitaria or on the solitaria side of phase transiens. In a second laboratory experiment that analysed the effects of locust density on phase transformation by P. locustae, there was no obvious effect of density on female locusts 10 days later as all were solitaria at all locust densities. At day 16, female locusts were transiens at higher densities, but were solitaria at 4/cage. With males there were lesser effects. These results provide new evidence for P. locustae having sub-lethal effects on locust phase transformation at a wide range of locust densities.     

Spore Dimorphism in a Microsporidan Isolate*

A microsporidan isolate currently considered to represent a mixed infection of Nosema necatrix Kramer, 1965 and Thelohania diazoma Kramer, 1965 was subjected to cultivation in hosts held at various temperatures. The ratio of the Nosema (monospore) to the Thelohania (octospore) forms at these temperatures was found to vary from 1:1 at 16 C to 1:0 at 32 C. Isolation technics using mechanical, temperature and temporal methods separated monosporous from octosporous forms for inoculation purposes. However, microscopic examination of hosts receiving these inocula revealed the presence of both monospores and octospores. Electrophoretic analysis of monospores and monospore-octospore mixtures indicated equivalent hydrophobic protein spectra. These observations suggest that this isolate has the ability to produce either single spores or spores in groups of eight. This microsporidan was not considered a member of the genus Stempellia since spores in groups of 2 or 4 were not observed. Retention of the name Nosema necatrix Kramer is suggested.     

Energetic stress in the honeybee Apis mellifera from Nosema ceranae infection

Parasites are dependent on their hosts for energy to reproduce and can exert a significant nutritional stress on them. Energetic demand placed on the host is especially high in cases where the parasite-host complex is less co-evolved. The higher virulence of the newly discovered honeybee pathogen, Nosema ceranae, which causes a higher mortality in its new host Apis mellifera, might be based on a similar mechanism. Using Proboscis Extension Response and feeding experiments, we show that bees infected with N. ceranae have a higher hunger level that leads to a lower survival. Significantly, we also demonstrate that the survival of infected bees fed ad libitum is not different from that of uninfected bees. These results demonstrate that energetic stress is the probable cause of the shortened life span observed in infected bees. We argue that energetic stress can lead to the precocious and risky foraging observed in Nosema infected bees and discuss its relevance to colony collapse syndrome. The significance of energetic stress as a general mechanism by which infectious diseases influence host behavior and physiology is discussed.