Epidemiology of Coxiella burnetii Infection in Africa: A OneHealth Systematic Review

Background

Q fever is a common cause of febrile illness and community-acquired pneumonia in resource-limited settings. Coxiella burnetii, the causative pathogen, is transmitted among varied host species, but the epidemiology of the organism in Africa is poorly understood. We conducted a systematic review of C. burnetii epidemiology in Africa from a “One Health” perspective to synthesize the published data and identify knowledge gaps.

Methods/Principal Findings

We searched nine databases to identify articles relevant to four key aspects of C. burnetii epidemiology in human and animal populations in Africa: infection prevalence; disease incidence; transmission risk factors; and infection control efforts. We identified 929 unique articles, 100 of which remained after full-text review. Of these, 41 articles describing 51 studies qualified for data extraction. Animal seroprevalence studies revealed infection by C. burnetii (≤13%) among cattle except for studies in Western and Middle Africa (18–55%). Small ruminant seroprevalence ranged from 11–33%. Human seroprevalence was <8% with the exception of studies among children and in Egypt (10–32%). Close contact with camels and rural residence were associated with increased seropositivity among humans. C. burnetii infection has been associated with livestock abortion. In human cohort studies, Q fever accounted for 2–9% of febrile illness hospitalizations and 1–3% of infective endocarditis cases. We found no studies of disease incidence estimates or disease control efforts.

Conclusions/Significance

C. burnetii infection is detected in humans and in a wide range of animal species across Africa, but seroprevalence varies widely by species and location. Risk factors underlying this variability are poorly understood as is the role of C. burnetii in livestock abortion. Q fever consistently accounts for a notable proportion of undifferentiated human febrile illness and infective endocarditis in cohort studies, but incidence estimates are lacking. C. burnetii presents a real yet underappreciated threat to human and animal health throughout Africa.     

Super-infection by Bacillus thuringiensis H34 or 3a3b can lead to death in mice infected with the influenza A virus

Bacterial super-infections are the main cause of complication and mortality after influenza virus (IAV) infection. Since Bacillus thuringiensis (Bt) is considered non-pathogenic for humans and is widely sprayed in urban areas, the aim of this work was to evaluate the potential pathogenicity of a combined infection Bt-IAV in a mouse model of pneumonia. Bacteria used for super-infections were Bt serotype H34 isolated from human infection and the insecticidal strain 3a3b obtained from a commercial source. Virus strain was A/Scotland/20/74 (H3N2) adapted to BALB/c mice by serial lung passage. Combined infection with 4% of the viral lethal dose 50% (LD(50)) and 10(2) spores of Bt H34 killed 40% of the mice. Mortality rates increased up to 55% and 100% when combined infections were done with respectively 10(4) and 10(7) spores. The insecticidal strain Bt 3a3b was less pathogenic than Bt H34. A dose of 10(4) spores associated with 4% of IAV LD(50) killed 50% of the mice. This inoculum must be compared with the doses usually sprayed in agriculture: 10(11) spores m(-2). Total protection against super-infection was obtained when mice were treated with amantadine. Even if only a few cases of Bt human infection have been reported, these results suggest a possible risk for workers spraying Bt-based biopesticides during flu outbreaks.     

Prevalence, characterization and growth of Bacillus cereus in commercial cooked chilled foods containing vegetables

In cooked-chilled and pasteurized vegetable products, initial numbers of Bacillus cereus were below 10 cfu g-1. Before the appearance of spoilage, numbers reached 6-8 log cfu g-1 at 20 degrees C and 4-6 log cfu g-1 at 10 degrees C. Bacillus cereus was not detected in samples stored at 4 degrees C. Ten percent of strains isolated from the products were able to grow at 5 degrees C and 63% at 10 degrees C. Bacillus cereus strains unable to degrade starch, a feature linked to the production of emetic toxin, did not grow at 10 degrees C and had a higher heat resistance at 90 degrees C. Using immunochemical assays, enterotoxin was detected in the culture supernatant fluid of 97.5% of the strains. All culture supernatant fluids were cytotoxic but important variations in the level of activity were found. Psychrotrophic isolates of B. cereus were unable to grow in courgette broth at 7 degrees C whereas they grew in a rich laboratory medium. At 10 degrees C, these isolates grew in both media but lag time in courgette broth was 20-fold longer than in the rich laboratory medium.     

Acute, sublethal and combination effects of azadirachtin and Bacillus thuringiensis toxins on Helicoverpa armigera (Lepidoptera: Noctuidae) larvae

The efficacy of neem (1500 ppm azadirachtin (AI)), Delfin WG, a biological insecticide based on selected strain of Bacillus thuringiensis Berliner (Bt) subspecies kurstaki, and Cry1Ac protein, either individually or in combination, were examined against first to fourth instar Helicoverpa armigera (Hübner) larvae. Using an oral administration method, various growth inhibitory concentrations (EC) and lethal concentrations (LC) were determined for each bioagent. Combinations of sublethal concentrations of Bt spray formulation with azadirachtin at EC50 or EC95 levels not only enhanced the toxicity, but also reduced the duration of action when used in a mixture. The LC20 and LC50 values for Cry1Ac toxin were 0.06 and 0.22 microg ml-1, respectively. Bt-azadirachtin combinations of LC50+EC20 and LC50+EC50 result in 100% mortality. The mortality also was significant in LC20+EC20 and LC20+EC50 mixtures. These studies imply that the combined action is not synergistic but complimentary, with azadirachtin particularly facilitating the action of Bt. The Bt spray-azadirachtin combination is more economical than combinations that involve isolating the toxic protein, as the Bt spray formulations can be combined in a spray mixture with neem. These combinations may be useful for controlling bollworm populations that have acquired resistance to Bt as they may not survive the effect of mixture. Azadirachtin may be useful as a means of reducing the endotoxin concentrations in a mixture, to promote increased economic savings and further reduce the probability of resistance development to either insect control agent.     

Effects of Cry1Ab-expressing corn anthers on the movement of monarch butterfly larvae

Decreased larval feeding and weight of the monarch butterfly, Danaus plexippus L., have been detected after 4 d of exposure in the laboratory to a high density of Bacillus thuringiensis (Bt)-expressing anthers. One hypothesis is that larvae exposed to Bt anthers exhibit increased wandering, resulting in less feeding and lower weight gain. To test this hypothesis, 2-d-old monarch butterfly larvae exposed to milkweed leaf disks with no anthers, anthers that express Bt (Cry1Ab, event MON810), or other non-Bt anthers were observed using a video-tracking system. As had been shown in previous studies, larvae exposed to Bt anthers fed less and gained less weight than larvae exposed to non-Bt or no anthers, yet there was no evidence of feeding on anthers. Total distance moved, maximum displacement from release point, percentage of time spent moving or near anthers, or mean turn angle did not differ across treatments. However, larvae exposed to Bt anthers spent more time off milkweed leaf disks than those exposed to no anthers and were more likely to move off the leaf than larvae exposed to non-Bt anthers. Results suggest that larvae exposed to Bt anthers behave differently and that ingestion may not be the only way Bt can affect nontarget insects like the monarch butterfly.     

Effects of entomopathogenic nematodes on evolution of pink bollworm resistance to Bacillus thuringiensis toxin Cry1Ac

The evolution of resistance by pests can reduce the efficacy of transgenic crops that produce insecticidal toxins from Bacillus thuringiensis (Bt). However, fitness costs may act to delay pest resistance to Bt toxins. Meta-analysis of results from four previous studies revealed that the entomopathogenic nematode Steinernema riobrave (Rhabditida: Steinernematidae) imposed a 20% fitness cost for larvae of pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), that were homozygous for resistance to Bt toxin Cry1Ac, but no significant fitness cost was detected for heterozygotes. We conducted greenhouse and laboratory selection experiments to determine whether S. riobrave would delay the evolution of pink bollworm resistance to Cry1Ac. We mimicked the high dose/refuge scenario in the greenhouse with Bt cotton (Gossypium hirsutum L.) plants and refuges of non-Bt cotton plants, and in the laboratory with diet containing Cry1Ac and refuges of untreated diet. In both experiments, half of the replicates were exposed to S. riobrave and half were not. In the greenhouse, S. riobrave did not delay resistance. In the laboratory, S. riobrave delayed resistance after two generations but not after four generations. Simulation modeling showed that an initial resistance allele frequency > 0.015 and population bottlenecks can diminish or eliminate the resistance-delaying effects of fitness costs. We hypothesize that these factors may have reduced the resistance-delaying effects of S. riobrave in the selection experiments. The experimental and modeling results suggest that entomopathogenic nematodes could slow the evolution of pest resistance to Bt crops, but only under some conditions.     

转Bt基因抗虫玉米对亚洲玉米螟幼虫取食行为的影响

室内研究了转cry1Ab杀虫蛋白基因的Bt抗虫玉米MON81 0和Bt1 1对亚洲玉米螟Ostriniafurnacalis初孵幼虫和3龄幼虫的取食行为、取食选择性和存活率的影响。在48h的非选择性试验中玉米螟初孵幼虫在MON81 0和Bt1 1玉米心叶组织上的幼虫取食率随时间的增加而下降,在对照玉米上的幼虫取食率随时间的增加而上升,两者间差异极显著。初孵幼虫接虫到MON81 0和Bt1 1玉米叶片48h的累计死亡率分别为67 .5 %和47 .5 % ,而在对照玉米上死亡率均为0. 3龄幼虫在Bt和非Bt玉米穗轴组织上的幼虫取食率随时间的增加呈上升趋势,第48h时在Bt和非Bt玉米上的幼虫取食率分别达到77 5 %和1 0 0 % ,差异极显著。选择性试验中,第4～48h内,初孵幼虫在Bt玉米上的幼虫取食率呈下降趋势,第48h时MON81 0和Bt1 1与各自非Bt对照的组合中初孵幼虫的累计死亡率分别为2 5 .0 %和1 7. 5 % ,二者差异不显著。3龄幼虫在Bt玉米和非Bt玉米上的幼虫取食率均随时间的延长而增加,但在非Bt玉米的幼虫取食率增加速度快,与Bt玉米差异极显著。Bt玉米对玉米螟幼虫取食有抑制和忌避作用。     

Risk assessment and ecological effects of transgenic Bacillus thuringiensis crops on non-target organisms

The application of recombinant DNA technology has resulted in many insect-resistant varieties by genetic engineering (GE). Crops expressing Cry toxins derived from Bacillus thuringiensis (Bt) have been planted worldwide, and are an effective tool for pest control. However, one ecological concern regarding the potential effects of insect-resistant GE plants on non-target organisms (NTOs) has been continually debated. In the present study, we briefly summarize the data regarding the development and commercial use of transgenic Bt varieties, elaborate on the procedure and methods for assessing the non-target effects of insect-resistant GE plants, and synthetically analyze the related research results, mostly those published between 2005 and 2010. A mass of laboratory and field studies have shown that the currently available Bt crops have no direct detrimental effects on NTOs due to their narrow spectrum of activity, and Bt crops are increasing the abundance of some beneficial insects and improving the natural control of specific pests. The use of Bt crops, such as Bt maize and Bt cotton, results in significant reductions of insecticide application and clear benefits on the environment and farmer health. Consequently, Bt crops can be a useful component of integrated pest management systems to protect the crop from targeted pests.     

Ontological model of multi-agent Smart-system for predicting drug properties based on modified algorithms of artificial immune systems

Estimating HIV incidence is crucial for monitoring the epidemiology of this infection, planning screening and intervention campaigns, and evaluating the effectiveness of control measures. However, owing to the long and variable period from HIV infection to the development of AIDS and the introduction of highly active antiretroviral therapy, accurate incidence estimation remains a major challenge. Numerous estimation methods have been proposed in epidemiological modeling studies, and here we review commonly-used methods for estimation of HIV incidence. We review the essential data required for estimation along with the advantages and disadvantages, mathematical structures and likelihood derivations of these methods. The methods include the classical back-calculation method, the method based on CD4+ T-cell depletion, the use of HIV case reporting data, the use of cohort study data, the use of serial or cross-sectional prevalence data, and biomarker approach. By outlining the mechanistic features of each method, we provide guidance for planning incidence estimation efforts, which may depend on national or regional factors as well as the availability of epidemiological or laboratory datasets.     

Genetically engineered vegetables expressing proteins from Bacillus thuringiensis for insect resistance: successes, disappointments, challenges and ways to move forward

Genetically engineered (GE) insect-resistant crops that express proteins from Bacillus thuringiensis (Bt) have been widely adopted in the two field crops currently commercially available, Bt cotton and Bt corn. However, the development and commercialization of Bt vegetables has lagged in comparison, which is unfortunate since vegetables tend to be insecticide-intensive crops due to high pest pressure and cosmetic standards required for the market. While it is often stated that consumer choice has played a major role in companies avoiding development of Bt vegetables, this concept requires re-evaluation. In market studies in North America when consumers have been provided basic information about Bt genetic engineering, then given a choice between Bt and conventional sweet corn, they have often preferred the former. Likewise, 77% of consumers in a US survey said they would likely purchase foods produced through biotechnology for their ability to reduce pesticide use. Presently, however, the only commercialized Bt vegetable is sweet corn. Perhaps more critical obstacles to Bt vegetables are their relatively smaller acreages and the cost of government biosafety regulations that inadvertently favor large acreage of field crops because companies can obtain a better return on investment. In developing countries, private-public partnerships may provide the vehicle to bring Bt vegetables to market. However, these can be subverted by misinformation from anti-biotech campaigns, as is the case with Bt eggplant in India. Without the use of Bt vegetables as a tool for integrated pest management, farmers and the general public will not be able to realize the substantial environmental and economic benefits that have been well documented with Bt cotton and Bt corn.     

Effect of bacterial infection on antioxidant activity and lipid peroxidation in the midgut of Galleria mellonella L. larvae (Lepidoptera, Pyralidae)

Bacillus thuringiensis is one of the most widely used sources of biorational pesticides, as well as a key source of genes for transgenic expression to provide pest resistance in plants. In this study the effect of Bacillus thuringiensis ssp. galleriae (Bt) infection on the activity of superoxide dismutase (SOD), glutathione S-transferase (GST), catalase (CAT), concentrations of oxidated and reduced thiols (RSSR/RSH) and malondialdehyde (MDA) was tested in the midgut of Galleria mellonella larvae. We found that Bt infection resulted in increased activities of SOD, GST, malondialdehyde and RSSR/RSH ratio the first day after inoculation. However, catalase activity decreased on the first and following days after bacterial infection by Bt. Our results confirm the hypothesis that Bt infection increases the level of oxidative stress in the larval midgut. In light of this study, it seems possible that oxidative damage contributes to cell death in the midgut during bacteriosis.     

革兰氏阳性菌苏云金芽孢杆菌和革兰氏阴性菌大肠杆菌诱导的柞蚕蛹生理指标变化

【目的】明确柞蚕Antheraea pernyi对外源微生物防御性生理变化规律,为柞蚕的病害防治和合理饲养提供理论依据。【方法】本研究选用革兰氏阳性菌苏云金芽孢杆菌Bacillus thuringeinsis(Bt)和革兰氏阴性菌大肠杆菌Escherichia coli(Ec)为外源诱导微生物,调整至10~6～10~8cfu/m L菌液,灭活后处理柞蚕蛹,诱导24,48,72和96 h后不同时间测定血淋巴蛋白含量、PO活性、CAT活性、抗菌活性和溶菌酶活性等生理指标。【结果】Ec和Bt诱导柞蚕蛹导致各生理指标出现显著变化,但两种菌株诱导生理指标变化规律差异明显,Ec高浓度诱导72 h会增加血淋巴蛋白含量,而Bt各浓度诱导会在24,48和96 h增加血淋巴蛋白含量。免疫防御关键酶系PO和CAT活性变化规律在不同菌株诱导后差异更明显,Ec诱导后,PO活性随着时间增加表现为先升高后降低的趋势,CAT活性呈现"升高-降低-升高"的规律;而Bt诱导后PO活性表现为"升高-降低-升高"的规律,CAT活性随诱导时间增加变化规律不明显,但有随菌液浓度增加而降低的趋势。对抗菌活性测定表明,Ec和Bt诱导都会显著增加蛹粗酶液抗菌活性,溶菌酶活性也会极显著增加,但2个指标高峰值出现的时间会有明显差别。【结论】本研究结果表明Ec和Bt不同处理均可诱导柞蚕蛹产生明显防御反应,但柞蚕蛹生理指标变化规律与不同种类微生物及处理时间和浓度有关,推测革兰氏阳性菌和革兰氏阴性菌具有不同的诱导防御反应机制。研究结果可以为外源微生物侵染柞蚕后的免疫防御反应规律提供理论指导。     

Field-evolved resistance to Bt maize by western corn rootworm: predictions from the laboratory and effects in the field

Crops engineered to produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) provide an effective management tool for many key insect pests. However, pest species have repeatedly demonstrated their ability to adapt to management practices. Results from laboratory selection experiments illustrate the capacity of pest species to evolve Bt resistance. Furthermore, resistance has been documented to Bt sprays in the field and greenhouse, and more recently, by some pests to Bt crops in the field. In 2009, fields were discovered in Iowa (USA) with populations of western corn rootworm, Diabrotica virgifera virgifera LeConte, that had evolved resistance to maize that produces the Bt toxin Cry3Bb1. Fields with resistant insects in 2009 had been planted to Cry3Bb1 maize for at least three consecutive years and as many as 6years. Computer simulation models predicted that the western corn rootworm might evolve resistance to Bt maize in as few as 3years. Laboratory and field data for interactions between western corn rootworm and Bt maize indicate that currently commercialized products are not high-dose events, which increases the risk of resistance evolution because non-recessive resistance traits may enhance survival on Bt maize. Furthermore, genetic analysis of laboratory strains of western corn rootworm has found non-recessive inheritance of resistance. Field studies conducted in two fields identified as harboring Cry3Bb1-resistant western corn rootworm found that survival of western corn rootworm did not differ between Cry3Bb1 maize and non-Bt maize and that root injury to Cry3Bb1 maize was higher than injury to other types of Bt maize or to maize roots protected with a soil insecticide. These first cases of field-evolved resistance to Bt maize by western corn rootworm provide an early warning and point to the need to apply better integrated pest management practices when using Bt maize to manage western corn rootworm.     

抗虫转基因水稻和化学杀虫剂对稻田节肢动物群落的影响

从功能团优势度、功能团内科组成及其优势度、功能团个体数量、群落主要参数及群落结构相异性等方面,就含crylAb／crylAc融合基因的Bt水稻和化学杀虫剂对稻田节肢动物群落影响进行比较研究．结果表明,与对照田相比,Bt稻田的节肢动物功能团组成及其优势度、各功能团内科组成及其优势度分布、功能团内个体数量的时间动态、群落参数(物种丰富度、Shannon-Wiener多样性指数、均匀性指数、优势集中性指数)及时间动态在大多情况下均无显著差异,两者间群落结构相似性较高．Bt水稻对稻田节肢动物群落基本无明显的负效应、而化防田的功能团优势度等群落特征指标与对照田相比,有时具有明显甚至显著的差异;群落结构相似性也较低．综合分析表明,Bt水稻对稻田节肢动物群落的影响明显弱于化学杀虫剂。     

Effects of transgenic Bt corn litter on the earthworm Lumbricus terrestris

A 200-day study was carried out to investigate the impact of transgenic Bacillus thuringiensis (Bt) corn on immature and adult Lumbricus terrestris in the field and in the laboratory. Another objective of this study was to develop test methods that could be used for standard testing of the impact of transgenic plants on different earthworm species in the field and in the laboratory. For this purpose two different experiments were involved, a laboratory experiment with adult L. terrestris and a field experiment with immature L. terrestris. No lethal effects of transgenic Bt corn on immature and adult earthworms were observed. Immature L. terrestris in the field had a very similar growth pattern when fed either (Bt+) or (Bt-) corn litter. No significant differences in relative weights of (Bt+) and (Bt-) corn-fed adult L. terrestris were observed during the first 160 days of the laboratory trial, but after 200 days adult L. terrestris had a significant weight loss of 18% of their initial weight when fed (Bt+) corn litter compared to a weight gain of 4% of the initial weight of (Bt-) corn-fed earthworms. Further studies are necessary to see whether or not this difference in relative weight was due to the Bt toxin or other factors discussed in the study. Degradation of Cry1Ab toxin in corn residues was significantly slower in the field than at 10 degrees C in the laboratory. Enzyme-linked immunosorbent assay results indicated that earthworms in both experiments were exposed to the Bt toxin throughout the whole experimental time.     

Identification of Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a binding protein for a 68-kDa <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> parasporal protein cytotoxic against leukaemic cells

Background  

Bacillus thuringiensis (Bt), an ubiquitous gram-positive spore-forming bacterium forms parasporal proteins during the stationary phase of its growth. Recent findings of selective human cancer cell-killing activity in non-insecticidal Bt isolates resulted in a new category of Bt parasporal protein called parasporin. However, little is known about the receptor molecules that bind parasporins and the mechanism of anti-cancer activity. A Malaysian Bt isolate, designated Bt18 produces parasporal protein that exhibit preferential cytotoxic activity for human leukaemic T cells (CEM-SS) but is non-cytotoxic to normal T cells or other cancer cell lines such as human cervical cancer (HeLa), human breast cancer (MCF-7) and colon cancer (HT-29) suggesting properties similar to parasporin. In this study we aim to identify the binding protein for Bt18 in human leukaemic T cells.     

Insect resistance to transgenic Bt crops: lessons from the laboratory and field

Transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) grew on >62 million ha worldwide from 1996 to 2002. Despite expectations that pests would rapidly evolve resistance to such Bt crops, increases in the frequency of resistance caused by exposure to Bt crops in the field have not yet been documented. In laboratory and greenhouse tests, however, at least seven resistant laboratory strains of three pests (Plutella xylostella [L.], Pectinophora gossypiella [Saunders], and Helicoverpa armigera [Hübner]) have completed development on Bt crops. In contrast, several other laboratory strains with 70- to 10,100-fold resistance to Bt toxins in diet did not survive on Bt crops. Monitoring of field populations in regions with high adoption of Bt crops has not yet detected increases in resistance frequency. Resistance monitoring examples include Ostrinia nubilalis (Hübner) in the United States (6 yr), P. gossypiella in Arizona (5 yr), H. armigera in northern China (3 yr), and Helicoverpa zea (Boddie) in North Carolina (2 yr). Key factors delaying resistance to Bt crops are probably refuges of non-Bt host plants that enable survival of susceptible pests, low initial resistance allele frequencies, recessive inheritance of resistance to Bt crops, costs associated with resistance that reduce fitness of resistant individuals relative to susceptible individuals on non-Bt hosts ("fitness costs"), and disadvantages suffered by resistant strains on Bt hosts relative to their performance on non-Bt hosts ("incomplete resistance"). The relative importance of these factors varies among pest-Bt crop systems, and violations of key assumptions of the refuge strategy (low resistance allele frequency and recessive inheritance) may occur in some cases. The success of Bt crops exceeds expectations of many, but does not preclude resistance problems in the future.     

Dispersal of potato tuber moth estimated using field application of Bt for mark-capture techniques

A new mark-capture technique involving field applications of Bacillus thuringiensis Berliner (Bt) to study the dispersal of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated as a tool to improve information on the potential impact of insect pest dispersal on crop infestation and insecticide resistance. The acquisition and persistence of Bt on moths were characterized and potential contamination of moths from naturally occurring Bts was examined. This mark-capture technique was developed to mark larger numbers of moths than had been previously achieved with laboratory marking using fluorescent dyes in mark-release-recapture experiments. Applications of commercial preparations of Bt to 0.3 and 1.0 ha potato fields were estimated to have marked ca. 50 000 moths in each experiment. Pheromone trap catches of potato tuber moths in the Bt-sprayed fields and in potato fields at distances of ca. 80, 200, 350, and 750 m were assayed for the Bt marker using selective microbiological media and identification of characteristic Bt crystal inclusions. Marking rates of moths were 78–100% in the sprayed fields and, compared with our previous mark-release-recapture studies, marking at ca. 200 m was increased by 15–18-fold to >3.0 moths per trap. This capture rate allowed the calculation of a dispersal curve that improved the reliability of estimates of movement at farm-scale distances. These estimates indicated that 10% of the population dispersed to 240 m in 3 days, and suggested that moths can potentially disperse throughout a typical potato-growing area in one growing season. This level of dispersal has implications for the spread and management of potato tuber moth populations, especially if insecticide resistance is present.     

Identification of Bacillus thuringiensis subsp. kurstaki strain HD1-Like bacteria from environmental and human samples after aerial spraying of Victoria, British Columbia, Canada, with Foray 48B

Aerial applications of Foray 48B, which contains Bacillus thuringiensis strain HD1, were carried out on 9 to 10 May, 19 to 21 May, and 8 to 9 June 1999 to control European gypsy moth (Lymantria dispar) populations in Victoria, British Columbia, Canada. A major assessment of the health impact of B. thuringiensis subsp. kurstaki was conducted by the Office of the Medical Health Officer of the Capital Health Region during this period. Environmental (air and water) and human (nasal swab) samples, collected before and after aerial applications of Foray 48B, both in the spray zone and outside of the spray zone, were analyzed for the presence of strain HD1-like bacteria. Random amplified polymorphic DNA analysis, cry gene-specific PCR, and dot blot DNA hybridization techniques were used to screen over 11,000 isolates of bacteria. We identified bacteria with genetic patterns consistent with those of B. thuringiensis subsp. kurstaki HD1 in 9,102 of 10,659 (85.4%) isolates obtained from the air samples, 13 of 440 (2.9%) isolates obtained from the water samples, and 131 of 171 (76.6%) isolates from the nasal swab samples. These analyses suggest that B. thuringiensis subsp. kurstaki HD1-like bacteria were present both in the environment and in the human population of Victoria prior to aerial applications of Foray 48B. The presence of B. thuringiensis subsp. kurstaki HD1-like bacteria in human nasal passages increased significantly after the application of Foray 48B, both inside and outside the spray zone.     

Rapid evolution and the cost of resistance to Bacillus thuringiensis in greenhouse populations of cabbage loopers, Trichoplusia ni

The microbial insecticide Bacillus thuringiensis (Bt) has become the mainstay of non-chemical control of Lepidopteran pests, either as sprays or through the incorporation of Bt toxins into transgenic crops. Given the wide use of Bt, it is striking that currently only one pest species, Plutella xylostella, has been reported to have developed significant resistance to Bt outside the laboratory. By contrast, we report here the frequent and rapid development of resistance to B. thuringiensis kurstaki (Dipel, Abbott) in populations of cabbage loopers, Trichoplusia ni, in commercial greenhouses. Resistance to Bt appears to be costly and there is a rapid decline of resistance in populations collected from greenhouses and maintained in the laboratory without selection. Management of pests resistant to Bt in vegetable greenhouses will require sporadic use of Bt-based sprays or alternatively use of sprays containing other Bt toxins.