Entomopathogenic fungus as a biological control for an important vector of livestock disease: the Culicoides biting midge

Background

The recent outbreak of bluetongue virus in northern Europe has led to an urgent need to identify control measures for the Culicoides (Diptera: Ceratopogonidae) biting midges that transmit it. Following successful use of the entomopathogenic fungus Metarhizium anisopliae against larval stages of biting midge Culicoides nubeculosus Meigen, we investigated the efficacy of this strain and other fungi (Beauveria bassiana, Isaria fumosorosea and Lecanicillium longisporum) as biocontrol agents against adult C. nubeculosus in laboratory and greenhouse studies.

Methodology/Findings

Exposure of midges to ‘dry’ conidia of all fungal isolates caused significant reductions in survival compared to untreated controls. Metarhizium anisopliae strain V275 was the most virulent, causing a significantly decrease in midge survival compared to all other fungal strains tested. The LT₅₀ value for strain V275 was 1.42 days compared to 2.21–3.22 days for the other isolates. The virulence of this strain was then further evaluated by exposing C. nubeculosus to varying doses (10⁸–10¹¹ conidia m⁻²) using different substrates (horse manure, damp peat, leaf litter) as a resting site. All exposed adults were found to be infected with the strain V275 four days after exposure. A further study exposed C. nubeculosus adults to ‘dry’ conidia and ‘wet’ conidia (conidia suspended in 0.03% aq. Tween 80) of strain V275 applied to damp peat and leaf litter in cages within a greenhouse. ‘Dry’ conidia were more effective than ‘wet’ conidia, causing 100% mortality after 5 days.

Conclusion/Significance

This is the first study to demonstrate that entomopathogenic fungi are potential biocontrol agents against adult Culicoides, through the application of ‘dry’ conidia on surfaces (e.g., manure, leaf litter, livestock) where the midges tend to rest. Subsequent conidial transmission between males and females may cause an increased level of fungi-induced mortality in midges thus reducing the incidence of disease.     

Opportunities for improving risk communication during the permitting process for entomophagous biological control agents: a review of current systems

Concerns about potentially irreversible non-target impacts from the importation and release of entomophagous biological control agents (BCAs) have resulted in increasingly stringent national import requirements by National Plant Protection Organizations worldwide. However, there is a divergence of opinions among regulators, researchers, environmentalists, and the general public on ways to appropriately manage associated risks. Implementation of a comprehensive and effective risk communication process might narrow the opinion gaps. Results from a comprehensive survey conducted in the United States were used to describe communication habits of stakeholders involved in biological control and identify areas that are fundamental in an efficient process. In addition, this study critically reviews risk communication practices and how phytosanitary decisions are communicated in the permitting systems for entomophagous BCAs of several countries to identify risk communication tools used in an effective risk communication framework. The following barriers to efficient risk communication were identified: absence of a formalized risk communication process, undefined risk communication goals and target audiences, lack of credibility and objectivity of information sources, inefficiency of mode of distribution of messages, insufficient public participation, and lack of transparency of decision making processes. This paper suggests the creation and/or enhancement of modes of distribution of risk messages to increase coverage, understanding, and guidance. For instance, messages should be presented in different formats such as internet, brochures, and newspapers. Surveys, public meetings, and trainings/workshops are tools that can be used to characterize stakeholders’ diversity and develop risk messages specific to the targeted audience. Implementation of a participatory decision making process will increase stakeholder involvement and trust in the risk management plan. Development of practical mechanisms, such as public hearings will increase all stakeholders’ involvement in the risk assessment process. A clear framework describing how public comments will be incorporated in the decision making process should be implemented. Finally, to ensure a streamlined risk communication process, there must be consistency in the messages disseminated by federal, state, and local agencies.     

Scientific advances in the analysis of direct risks of weed biological control agents to nontarget plants

Research on host specificity testing protocols over the last 10 years has been considerable. Traditional experimental designs have been refined and interpretation of the results is benefiting from an improved understanding of agent behavior. The strengths, weaknesses, and best practice for the different test types are now quite clearly understood. Understanding the concept of fundamental host range (the genetically determined limits to preference and performance) and using this to maximize reliability in predicting field host specificity following release (behavioral expression of the fundamental host range under particular conditions) are still inconsistently understood or adopted despite having been identified as the critical steps in analyzing the threats posed by biological control agents to the agriculture and biodiversity of novel environments. This needs to be consistently understood and applied so the process of testing can follow a recognized process of risk analysis from hazard identification (identifying life stages of the agent that pose a threat and defining their fundamental host range) to uncertainty analysis based on the magnitude (predicted field host specificity following release) and likelihood of threats (predicted actual damage and impact) to nontargets. Modern molecular techniques are answering questions associated with subspecific variation in biological control agents with respect to host use and the chance of host shifts of agents following release. Guidelines for assessment of nontarget impacts need to recognize and adopt such recent developments and emphasize a general increased understanding of the evolution of host choice and the phylogenetic constraints to shifts in host use. This review covers all these recent advances for the first time in one document, highlighting how inconsistent interpretation by biological control practitioners can be avoided.     

Criteria for release of genetically-improved phytoseiids: an examination of the risks associated with release of biological control agents

Biological control of agricultural pests by phytoseiid predators has been achieved through classical introductions, conservation of indigenous and established foreign species, and augmentation of both introduced and indigenous species. Laboratory selection of phytoseiids has produced several strains that have been mass reared and released for pest management programs in glasshouses and agricultural cropping systems. Concerns over risks of classical biological control have developed recently. The development of recombinant DNA (rDNA) techniques for the genetic manipulation of crops and microorganisms also has inaugurated a debate on the safety of releasing transgenic organisms into the environment. This debate will extend to the release of phytoseiids that have been manipulated with rDNA techniques. Risks associated with releasing phytoseiids for augmentation or classical biological control programs are minimal and the benefits are great. Research initiated to answer questions about the risks of releasing transgenic phytoseiids into the environment provides opportunities to expand our understanding of the ecological impact of phytoseiids in agricultural and natural environments and could lead to improved pest management tactics.     

The role of community review in evaluating the risks of human genetic variation research.

The practicality and moral value of community review of human genetic research has become a focus of debate. Examples from two Native American communities are used to address four aspects of that debate: (1) the value of community review in larger, geographically dispersed populations; (2) the identification of culturally specific risks; (3) the potential conflict between individual and group assessments of research-related risks; and (4) the confusion of social categories with biological categories. Our experiences working with these two communities suggest that: (1) successful community review may require the involvement of private social units (e.g., families); (2) culturally specific implications of genetic research may be identifiable only by community members and are of valid concern in their moral universes; (3) community concerns can be incorporated into existing review mechanisms without necessarily giving communities the power to veto research proposals; and (4) the conflation of social and biological categories presents recruitment problems for genetic studies. These conclusions argue for the use of community review to identify and minimize research-related risks posed by genetic studies. Community review also can assist in facilitating participant recruitment and retention, as well as in developing partnerships between researchers and communities.     

A review of microcystin detections in Estuarine and Marine waters: Environmental implications and human health risk

Toxin production by harmful cyanobacteria blooms (CyanoHABs) constitutes a major, worldwide environmental threat to freshwater aquatic resources that is expected to expand in scale and intensity with global climate change. Extensive literature exists on the most frequently encountered cyanotoxin, microcystin, in freshwater environments. Yet, the expansion of microcystin producing CyanoHABs and the transport of contaminated inland waters to estuarine and coastal marine waters has only recently received attention. This paper synthesizes information on the salinity tolerance of microcystin producing cyanobacteria and summarizes available case reports on microcystin presence in estuarine and coastal waters. We highlight a potential food-borne exposure route to humans by reviewing the growing body of evidence that shows microcystins can accumulate in coastal seafood. These cases reinforce the importance of freshwater nutrient reduction and the need for freshwater management efforts to look beyond lacustrine and riverine systems. Events reviewed here likely only represent a small proportion of cases where microcystins affect estuarine and coastal waters. We strongly suggest increased monitoring and research efforts to understand, react to, and prevent ecological and health problems associated with the growing problem of toxic CyanoHABs in coastal environments.     

A methodology for risk analysis of plurivorous fungi in biological weed control: Sclerotinia sclerotiorum as a model

In New Zealand, research is being performed on the use of the ubiquitous plurivorous ascomycete Sclerotinia sclerotiorum, as a biocontrol agent for Cirsium arvense in pasture. As a consequence of the wide host range of this fungus, the proposed biocontrol may pose a risk to non-target arable plants. Crop disease risk is primarily due to the formation of sclerotia. These perennating bodies may directly infect susceptible crops sown at the biocontrol site in years after the biocontrol event. Additionally they may cause infection in neighbouring crops through the formation of apothecia from which airborne ascospores are dispersed. A methodology for a risk analysis is proposed, embodying both temporal and spatial processes, where the relative disease risk from biocontrol is defined as the ratio of added to naturally occurring inoculum.Exponential decay is proposed as a suitable model for the survival of sclerotia in soils beneath pastures, and data from an ongoing study are used in a preliminary parameterisation. The model is applied to published data on initial sclerotium population size and unpublished data on natural levels of soilborne sclerotia, to reveal how a withholding period, defined as the interval of time that must elapse for the ratio of added to natural inoculum to equal unity, may be calculated.For quantifying escape and aerial dispersal of ascospores from a treated pasture, three mechanistic models are proposed. Firstly, a simple one-layer model of escape, giving a provisional estimation of 81% of released ascospores escaping the pasture canopy, is discussed. Secondly, ascospore dispersal within and close to the biocontrol site (<30 m) is described by a model revealing abrupt decline in the atmospheric concentration of ascospores within short distances from the biocontrol site. Thirdly, for predicting ascospore concentrations at greater distances (>100 m), a Gaussian plume model is proposed. In a first approximation, these models are used in an example calculation to show how a hypothetical safety zone might be determined. A map of the province of Canterbury showing the locations of different agricultural activities and infestations of dense populations of C. arvense, revealed that potential biocontrol sites mostly do not border arable land and that a safety zone would therefore be feasible.The study presented here provides conceptual and mathematical frameworks for risk analysis of the use of plurivorous fungi in biological weed control, using S. sclerotiorum as an example. However, before a judgement may be made about the phytosanitory risks associated with the use of S. sclerotiorum to control C. arvense in pastures in Canterbury, the models developed in this paper must be parameterized using data collected under a wide range of conditions in the field.     

Potential role for fish in transmission of Mycobacterium ulcerans disease (Buruli ulcer): an environmental study

This study reports a potential role that fish may play in the transmission of Mycobacterium ulcerans disease (Buruli ulcer). Fish found positive for M. ulcerans DNA all appear to feed on insects or plankton and are believed to concentrate M. ulcerans from this usual food source. These observations provide additional data supporting our previous hypothesis on sources of M. ulcerans and modes of transmission.     

The role of heterogenous environmental conditions in shaping the spatiotemporal distribution of competing Aedes mosquitoes in Panama: implications for the landscape of arboviral disease transmission

Monitoring the invasion process of the Asian tiger mosquito Aedes albopictus and its interaction with the contender Aedes aegypti, is critical to prevent and control the arthropod-borne viruses (i.e., Arboviruses) they transmit to humans. Generally, the superior ecological competitor Ae. albopictus displaces Ae. aegypti from most geographic areas, with the combining factors of biology and environment influencing the competitive outcome. Nonetheless, detailed studies asserting displacement come largely from sub-tropical areas, with relatively less effort being made in tropical environments, including no comprehensive research about Aedes biological interactions in Mesoamerica. Here, we examine contemporary and historical mosquito surveillance data to assess the role of shifting abiotic conditions in shaping the spatiotemporal distribution of competing Aedes species in the Republic of Panama. In accordance with prior studies, we show that Ae. albopictus has displaced Ae. aegypti under suboptimal wet tropical climate conditions and more vegetated environments within the southwestern Azuero Peninsula. Conversely, in the eastern Azuero Peninsula, Ae. aegypti persists with Ae. albopictus under optimal niche conditions in a dry and more seasonal tropical climate. While species displacement was stable over the course of two years, the presence of both species generally appears to fluctuate in tandem in areas of coexistence. Aedes albopictus was always more frequently found and abundant regardless of location and climatic season. The heterogenous environmental conditions of Panama shape the competitive outcome and micro-geographic distribution of Aedes mosquitoes, with potential consequences for the transmission dynamics of urban and sylvatic zoonotic diseases.

     

Genetic predisposition and environmental risk factors to pancreatic cancer: A review of the literature

Some cases of pancreatic cancer (PC) are described to cluster within families. With the exception of PALLD gene mutations, which explain only a very modest fraction of familial cases, the genetic basis of familial PC is still obscure. Here the literature was reviewed in order to list the known genes, environmental factors, and health conditions associated with PC or involved in the carcinogenesis of the pancreas. Most of the genes listed are responsible for various well-defined cancer syndromes, such as CDKN2A (familial atypical mole-multiple melanoma, FAMMM), the mismatch repair genes (Lynch Syndrome), TP53 (Li-Fraumeni syndrome), APC (familial adenomatous polyposis), and BRCA2 (breast–ovarian familial cancer), where PC is part of the cancer spectrum of the disease. In addition, in this review I ranked known/possible risk factors extending the analysis to the hereditary pancreatitis (HP), diabetes, or to specific environmental exposures such as smoking. It appears that these factors contribute strongly to only a small proportion of PC cases. Recent work has revealed new genes somatically mutated in PC, including alterations within the pathways of Wnt/Notch and DNA mismatch repair. These new insights will help to reveal new candidate genes for the susceptibility to this disease and to better ascertain the actual contribution of the familial forms.     

A historical review of research on the weaver ant Oecophylla in biological control

1 Although the weaver ant Oecophylla is the first written record of biological control, dating from 304 ad , there have been fewer than 70 scientific publications on this predator as a biological control agent in Asia, from the early 1970s onwards, and fewer than 25 in Africa. 2 Apart from crop‐specific ecological and perceptual factors, a historical review shows that political and market forces have also determined the extent to which Oecophylla was incorporated into research and development programmes. 3 In Africa, research on weaver ants in biological control concentrated on export crops, such as coconut and cocoa, whereas, in Asia and Australia, research focused on fruit and nut crops, primarily destined for domestic markets. 4 Increased evidence of pesticide inefficiency under tropical smallholder conditions, changing paradigm shifts in participatory research and a growing scientific interest in local knowledge in the early 1990s opened up new avenues for research on conservation biological control. 5 Lobbying and advocacy have been needed to ensure that Oecophylla was recognized as an effective biological control agent. 6 With an increased market demand for organic produce, holistic approaches such as conservation biological control, particularly the use of Oecophylla, are increasing in importance. 7 Multi‐stakeholder strategies for collaborative learning are proposed for a better control of major fruit, nut and timber tree pests in Africa, Asia and Australia.     

Public health: the control of meningococcal disease in Quebec

A first outbreak of serogroup C meningococcal disease occurred in the province of Quebec in 1990-1992 and lead to a mass immunization campaign using polysaccharide vaccines. In 2001, a second outbreak was identified and a mass vaccination campaign was carried out, using the newly licensed conjugate vaccine. Clinical, epidemiological, economic and social studies were instrumental in the decision making for implementing these control programs.     

Coeliac disease: A review of the causative agents and their possible mechanisms of action

Summary This review outlines the main theories for the aetiology of coeliac disease and presents in more detail the work carried out in an attempt to define the nature of the toxins in wheat gluten. This includes the results of work with synthetic peptides and a discussion of the various assays used.Evidence is presented for an enzyme deficiency in coeliac disease which leads to abnormally high concentrations of certain peptides in the small bowel. These peptides can bring about damage by direct toxic action and by immunological mechanisms.Investigations of activity of synthetic peptides based on the structure of Agliadin appear to be making good progress and point to certain regions of that molecule as being responsible for toxicity. Certain key sequences of amino acids appear to be of fundamental importance to these studies.     

Epidemiological evidence for the role of physical activity in reducing risk of type 2 diabetes and cardiovascular disease.

Epidemiological studies suggest that physically active individuals have a 30-50% lower risk of developing type 2 diabetes than do sedentary persons and that physical activity confers a similar risk reduction for coronary heart disease. Risk reductions are observed with as little as 30 min of moderate-intensity activity per day. Protective mechanisms of physical activity include the regulation of body weight; the reduction of insulin resistance, hypertension, atherogenic dyslipidemia, and inflammation; and the enhancement of insulin sensitivity, glycemic control, and fibrinolytic and endothelial function. Public health initiatives promoting moderate increases in physical activity may offer the best balance between efficacy and feasibility to improve metabolic and cardiovascular health in largely sedentary populations.