Arthropod Containment Guidelines, Version 3.2

Laboratory maintenance and care of Rhodnius prolixus (Hemiptera: Reduviidae) and other Triatominae

Triatomines (Hemiptera: Reduviidae) are hematophagous insects that transmit Trypanosoma cruzi, the etiological agent for Chagas disease, to humans and other mammals. As medically important vectors, species such as Rhodnius prolixus (Hemiptera: Reduviidae) have long been used as a model organism for physiological studies. Laboratory rearing of triatomines is needed to support vector and parasite research. Many environmental conditions, such as suitable housing containers, light source and duration, temperature, humidity, and density, must be addressed when adapting triatomines from a natural habitat for artificial rearing to create conditions for optimal growth and survival. Food source is also an important factor, as triatomines are considered the obligate blood feeders. Parasites and pathogens present risks not only for triatomines but also for the laboratorians handling them. Equipping an insectary space should apply best practices to ensure community, personnel, and insect health. Various triatomine colonies have been maintained in the Centers for Disease Control and Prevention (CDC) Entomology Branch insectary for over 25 years and have more recently been made available to the research community through the Biodefense and Emerging Infections Research Resources Repository (BEI Resources). The CDC Rhodnius prolixus genome has been characterized and thus represents an opportunity for continued model organism research. In addition to fulfilling requests for live triatomines, inquiries are received for support in establishing new and troubleshooting existing laboratory colonies. To accompany the extensive MR4 manual, Methods in Anopheles Research, procedures for triatomine husbandry have been developed and are shared here to address the aforementioned topics.

A field bioassay for assessing ivermectin bio-efficacy in wild malaria vectors

BACKGROUND

Ivermectin (IVM) mass drug administration is a candidate complementary malaria vector control tool. Ingestion of blood from IVM treated hosts results in reduced survival in mosquitoes. Estimating bio-efficacy of IVM on wild-caught mosquitoes requires they ingest the drug in a blood meal either through a membrane or direct feeding on a treated host. The latter, has ethical implications, and the former results in low feeding rates. Therefore, there is a need to develop a safe and effective method for IVM bio-efficacy monitoring in wild mosquitoes.

METHODS

Insectary-reared Anopheles gambiae s.s. were exposed to four IVM doses: 85, 64, 43, 21 ng/ml, and control group (0 ng/ml) in three different solutions: (i) blood, (ii) 10% glucose, (iii) four ratios (1:1, 1:2, 1:4, 1:8) of blood in 10% glucose, and fed through filter paper. Wild-caught An. gambiae s.l. were exposed to 85, 43 and 21 ng/ml IVM in blood and 1:4 ratio of blood-10% glucose mixture. Survival was monitored for 28 days and a pool of mosquitoes from each cohort sacrificed immediately after feeding and weighed to determine mean weight of each meal type.

RESULTS

When administered in glucose solution, mosquitocidal effect of IVM was not comparable to the observed effects when similar concentrations were administered in blood. Equal concentrations of IVM administered in blood resulted in pronounced reductions in mosquito survival compared to glucose solution only. However, by adding small amounts of blood to glucose solution, mosquito mortality rates increased resulting in similar effects to what was observed during blood feeding.

CONCLUSION

Bio-efficacy of ivermectin is strongly dependent on mode of drug delivery to the mosquito and likely influenced by digestive processes. The assay developed in this study is a good candidate for field-based bio-efficacy monitoring: wild mosquitoes readily feed on the solution, the assay can be standardized using pre-selected concentrations and by not involving treated blood hosts (human or animal) variation in individual pharmacokinetic profiles as well as ethical issues are bypassed. Meal volumes did not explain the difference in the lethality of IVM across the different meal types necessitating further research on the underlying mechanisms.

Infravec2 guidelines for the design and operation of containment level 2 and 3 insectaries in Europe

With the current expansion of vector-based research and an increasing number of facilities rearing arthropod vectors and infecting them with pathogens, common measures for containment of arthropods as well as manipulation of pathogens are becoming essential for the design and running of such research facilities to ensure safe work and reproducibility, without compromising experimental feasibility. These guidelines and comments were written by experts of the Infravec2 consortium, a Horizon 2020-funded consortium integrating the most sophisticated European infrastructures for research on arthropod vectors of human and animal diseases. They reflect current good practice across European laboratories with experience of safely handling different mosquito species and the pathogens they transmit. As such, they provide experience-based advice to assess and manage the risks to work safely with mosquitoes and the pathogens they transmit. This document can also form the basis for research with other arthropods, for example, midges, ticks or sandflies, with some modification to reflect specific requirements.

Evaluating the Clinical and Immune Responses to Spotted Fever Rickettsioses in the Guinea Pig-Tick-Rickettsia System

The guinea pig was the original animal model developed for investigating spotted fever rickettsiosis (SFR). This model system has persisted on account of the guinea pig's conduciveness to tick transmission of SFR agents and ability to recapitulate SFR in humans through clinical signs that include fever, unthriftiness, and in some cases the development of an eschar. The guinea pig is the smallest animal model for SFR that allows the collection of multiple blood and skin samples antemortem for longitudinal studies. This unit provides the basic protocols necessary to establish, maintain, and utilize a guinea pig-tick-Rickettsia model for monitoring the course of infection and immune response to an infection by spotted fever group Rickettsia (SFGR) that can be studied at biosafety level 2 (BSL-2) and arthropod containment level 2 (ACL-2); adaptations must be made for BSL-3 agents. The protocols cover methods for tick feeding and colony development, laboratory infection of ticks, tick transmission of Rickettsia to guinea pigs, and monitoring of the course of infection through clinical signs, rickettsial burden, and immune response. It should be feasible to adapt these methods to study other tick-borne pathogens. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Tick transmission of SFGR to guinea pigs Support Protocol 1: Laboratory infection of ticks by injection Alternate Protocol 1: Needle inoculation of SFGR to guinea pigs Basic Protocol 2: Monitoring the course of guinea pig rickettsial infection: clinical signs Basic Protocol 3: Monitoring the course of guinea pig rickettsial infection: collection of biological specimens Support Protocol 2: Guinea pig anesthesia Basic Protocol 4: Monitoring rickettsial burden in guinea pigs by multiplex qPCR Basic Protocol 5: Monitoring guinea pig immune response to infection: blood leukocytes by flow cytometry Basic Protocol 6: Monitoring immune response to guinea pig rickettsial infection: leukocyte infiltration of skin at the tick bite site by flow cytometry Basic Protocol 7: Monitoring the immune response to guinea pig rickettsial infection: antibody titer by ELISA Support Protocol 4: Coating ELISA Plates Alternate Protocol 2: Monitoring immune response to guinea pig rickettsial infection: antibody titer by immunofluorescence assay.

Mapping and CRISPR homology-directed repair of a recessive white eye mutation in Plodia moths

The pantry moth Plodia interpunctella is a worldwide pest of stored food products and a promising laboratory model system for lepidopteran functional genomics. Here we describe efficient methods for precise genome editing in this insect. A spontaneous recessive white-eyed phenotype maps to a frameshift deletion (c.737delC) in the white gene. CRISPR NHEJ mutagenesis of white replicates this phenotype with high rates of somatic biallelic knockout. G₀ individuals with mutant clones on both eyes produced 100% mutant progeny, making white an ideal marker for co-conversion when targeting other genes. CRISPR HDR experiments corrected c.737delC and reverted white eyes to a pigmented state in 37% of G₀ mosaic adults. These repaired alleles showed practical rates of germline transmission in backcrosses, demonstrating the potential of the technique for precise genome editing. Plodia offers a promising avenue for research in this taxon because of its lab-ready features, egg injectability, and editability.

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Plodia pantry moths are an emerging model organism for functional genomics in Lepidoptera

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Spontaneous and CRISPR-induced white mutations yield recessive-white eye phenotypes

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CRISPR HDR repair with ssODN donor result in practical rates of base editing

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We provide optimized protocols for Plodia handling and genome editing

Preparing an Insectary in Burkina Faso to Support Research in Genetic Technologies for Malaria Control

The Institut de Recherche en Sciences de la Santé (IRSS) of Burkina Faso, West Africa, was the first African institution to import transgenic mosquitoes for research purposes. A shift from the culture of mosquito research to regulated biotechnology research and considerable management capacity is needed to set up and run the first insectary for transgenic insects in a country that applied and adapted the existing biosafety framework, first developed for genetically modified (GM) crops, to this new area of research. The additional demands arise from the separate regulatory framework for biotechnology, referencing the Cartagena Protocol on Biosafety, and the novelty of the research strain, making public understanding and acceptance early in the research pathway important. The IRSS team carried out extensive preparations following recommendations for containment of GM arthropods and invested efforts in local community engagement and training with scientific colleagues throughout the region. Record keeping beyond routine practice was established to maintain evidence related to regulatory requirements and risk assumptions. The National Biosafety Agency of Burkina Faso, Agence Nationale de Biosécurité (ANB), granted the permits for import of the self-limiting transgenic mosquito strain, which took place in November 2016, and for conducting studies in the IRSS facility in Bobo-Dioulasso. Compliance with permit terms and conditions of the permits and study protocols continued until the conclusion of studies, when the transgenic colonies were terminated. All this required close coordination between management and the insectary teams, as well as others. This article outlines the experiences of the IRSS to support others undertaking such studies. The IRSS is contributing to the ongoing development of genetic technologies for malaria control, as a partner of Target Malaria. The ultimate objective of the innovation is to reduce malaria transmission by using GM mosquitoes of the same species released to reduce the disease-vectoring native populations of Anopheles gambiae s.l.

Containment Practices for Arthropods Modified with Engineered Transgenes Capable of Gene Drive Addendum 1 to the Arthropod Containment Guidelines, Version 3.2

Responsible conduct of research is a cornerstone of rigorous scientific discovery. Institutional committees, independent advisory panels, and expert steering groups are among the frameworks in academia meant to provide guidance and assurances that research activities do not result in harm to the environment, research staff, or public safety. For research involving arthropods of public health importance, several documents currently exist to guide investigators in methodologies to consider for reducing risks from arthropod escape. However, to date, there has been no standardized set of recommendations on containment practices for arthropods modified with engineered transgenes capable of gene drive. This document is meant to serve as a practical reference to fill that gap. Recommendations outlined here address containment considerations when a risk assessment indicates a possibility of establishment of a new arthropod vector species or genetically modified arthropods in the local environment.

A Phenotypic Screen for the Liver Stages of Plasmodium vivax

Control of malaria caused by Plasmodium vivax can be improved by the discovery and development of novel drugs against the parasite's liver stage, which includes relapse-causing hypnozoites. Several recent reports describe breakthroughs in the culture of the P. vivax liver stage in 384-well microtiter plates, with the goal of enabling a hypnozoite-focused drug screen. Herein we describe assay details, protocol developments, and different assay formats to interrogate the chemical sensitivity of the P. vivax liver stage in one such medium-throughput platform. The general assay protocol includes seeding of primary human hepatocytes which are infected with P. vivax sporozoites generated from the feeding of Anopheles dirus mosquitoes on patient isolate bloodmeals. This protocol is unique in that, after source drug plates are supplied, all culture-work steps have been optimized to preclude the need for automated liquid handling, thereby allowing the assay to be performed within resource-limited laboratories in malaria-endemic countries. Throughput is enhanced as complex culture methods, such as extracellular matrix overlays, multiple cell types in co-culture, or hepatic spheroids, are excluded as the workflow consists entirely of routine culture methods for adherent cells. Furthermore, installation of a high-content imager at the study site enables assay data to be read and transmitted with minimal logistical delays. Herein we detail distinct assay improvements which increase data quality, provide a means to limit the confounding effect of hepatic metabolism on assay data, and detect activity of compounds with a slow-clearance phenotype. Graphical abstract: Overview of P. vivax liver stage screening assay performed at the Institute Pasteur of Cambodia.

How relevant are in vitro culture models for study of tick-pathogen interactions?

Although tick-borne infectious diseases threaten human and animal health worldwide, with constantly increasing incidence, little knowledge is available regarding vector-pathogen interactions and pathogen transmission. In vivo laboratory study of these subjects using live, intact ticks is expensive, labor-intensive, and challenging from the points of view of biosafety and ethics. Several in vitro models have been developed, including over 70 continuous cell lines derived from multiple tick species and a variety of tick organ culture systems, facilitating many research activities. However, some limitations have to be considered in the translation of the results from the in vitro environment to the in vivo situation of live, intact ticks, and vertebrate hosts. In this review, we describe the available in vitro models and selected results from their application to the study of tick-borne viruses, bacteria, and protozoa, where possible comparing these results to studies in live, intact ticks. Finally, we highlight the strengths and weaknesses of in vitro tick culture models and their essential role in tick-borne pathogen research.

Demystifying the Risk Assessment Process for Laboratory-Based Experiments Utilizing Invasive Genetic Elements: It Is More Than Gene Drive

Advances in recombinant DNA approaches have resulted in the development of transgene architectures that severely bias their own inheritance, a process commonly referred to as "gene drive." The rapid pace of development, combined with the complexity of many gene drive approaches, threatens to overwhelm those responsible for ensuring its safe use in the laboratory, as even identifying that a specific transgene is capable of gene drive may not be intuitive. Although currently gene drive experiments have been limited to just a few species (mosquitoes, flies, mice, and yeast), the range of organisms used in gene drive research is expected to increase substantially in the coming years. Here the defining features of different gene drive approaches are discussed. Although this will start with a focus on identifying when gene drive could or could not occur, the emphasis will also be on establishing risk profiles based on anticipated level of invasiveness and persistence of transgenes in the surrounding environment. Attention is also called to the fact that transgenes can be considered invasive without being considered gene drive (and vice versa). This further supports the notion that adequate risk assessment requires information regarding the specific circumstances a given transgene or set of transgenes is capable of invading a corresponding population. Finally, challenges in the review and evaluation of work involving gene drive organisms are discussed.

Ixodid Tick Dissection and Tick Ex Vivo Organ Cultures for Tick-Borne Virus Research

Tick-borne viruses cause thousands of cases of disease worldwide every year. Specific countermeasures to many tick-borne viruses are not commercially available. Very little is known regarding tick-virus interactions and increasing this knowledge can lead to potential targets for countermeasure development. Virus infection of ex vivo organ cultures from ticks can provide an approach to identify susceptible cell types of tissue to infection. Additionally, these organ cultures can be used for functional genomic studies to pinpoint tick-specific genes involved in the virus lifecycle. Provided here are step-by-step procedures to set up basic tick organ cultures in combination with virus infection and/or functional genomic studies. These procedures can be adapted for future use to characterize other tick-borne pathogen infections as well as tick-specific biological processes. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Loading 96-well plates with gelfoam substrate Basic Protocol 2: Step-by-step aseptic dissection of unfed female/male Ixodes scapularis ticks for multiple organs Basic Protocol 3: Step-by-step aseptic dissection of fed female Ixodes scapularis ticks to remove salivary glands Basic Protocol 4: Metabolic viability analyses of tick organ cultures Basic Protocol 5: Virus infection of tick organ cultures Basic Protocol 6: Functional RNA interference analyses using tick organ cultures.

Increasing Effectiveness of Genetically Modifying Mosquito Populations: Risk Assessment of Releasing Blood-Fed Females

Releasing mosquito refractory to pathogens has been proposed as a means of controlling mosquito-borne diseases. A recent modeling study demonstrated that instead of the conventional male-only releases, adding blood-fed females to the release population could significantly increase the program's efficiency, hastening the decrease in disease transmission competence of the target mosquito population and reducing the duration and costs of the release program. However, releasing female mosquitoes presents a short-term risk of increased disease transmission. To quantify this risk, we constructed a Ross-MacDonald model and an individual-based stochastic model to estimate the increase in disease transmission contributed by the released blood-fed females, using the mosquito Aedes aegypti and the dengue virus as a model system. Under baseline parameter values informed by empirical data, our stochastic models predicted a 1.1-5.5% increase in dengue transmission during the initial release, depending on the resistance level of released mosquitoes and release size. The basic reproductive number (R0) increased by 0.45-3.62%. The stochastic simulations were then extended to 10 releases to evaluate the long-term effect. The overall reduction of disease transmission was much greater than the number of potential infections directly contributed by the released females. Releasing blood-fed females with males could also outperform conventional male-only releases when the release strain is sufficiently resistant, and the release size is relatively small. Overall, these results suggested that the long-term benefit of releasing blood-fed females often outweighs the short-term risk.

Challenges and Opportunities in the Use of High and Maximum Biocontainment Facilities in Developing and Licensing Risk Group 3 and Risk Group 4 Agent Veterinary Vaccines

New solutions are necessary for the singular global health security threat formed by endemic, epidemic, and emerging/re-emerging zoonoses, coupled with epizootic and enzootic transboundary animal diseases (TADs). This One Health issue is related to the daily interactions between wildlife, domesticated and indigenous livestock, and humans primarily associated with global trade, transboundary co-movement of humans and diverse livestock/livestock products, and agriculture production intensification and penetration into previously uninhabited areas. The World Health Organization defines Risk Group 3 (RG-3) and RG-4 pathogens as mainly viruses but also bacteria that serve as the foundation for approximately 60% of emerging infectious diseases that are zoonoses. The World Organisation for Animal Health defines trade-notifiable TADs, and subsets of these are zoonotic. Livestock vaccination policies mainly focus on TADs that are promulgated by the United Nations Food and Agriculture Organization and government agriculture agencies. The development, licensure, and product manufacturing of next-generation molecular-based RG-3 and RG-4 veterinary vaccines largely ignored by the global animal health biopharmaceutical sector can have an important positive impact on food security and One Health. There have been sharp increases in the global demand for livestock meat and milk products, especially in low- and middle-income countries in Africa and Asia. This relatively recent market driver-coupled with scientific advances in human EID and zoonotic disease vaccine platform technologies and increases in the number of high (US biosafety level 3 agriculture) and maximum (US animal biosafety level 4) biocontainment facilities with supporting workforce capabilities-offers new investment opportunities to the animal health biopharmaceutical sector. Moreover, a growing number of One Health public-private partnerships have moved the net present value calculus in favor of the financial feasibility of RG-3 and RG-4 veterinary vaccine product development and licensure. This article highlights the challenges and opportunities in the use of high and maximum biocontainment facilities in developing and licensing RG-3 and RG-4 veterinary vaccines that are safe and effective against epizootic and enzootic TADs and zoonotic diseases.

Evaluation of Hydrogen Peroxide Fumigation and Heat Treatment for Standard Emergency Arthropod Inactivation in BSL-3 Insectaries

Climate change and global movements of people and goods have accelerated the spread of invasive species, including insects that vector infectious diseases, which threaten the health of more than half of the world’s population. Increasing research efforts to control these diseases include the study of vector – pathogen interactions, involving the handling of pathogen-infected vector insects under biosafety level (BSL) 2 and 3 conditions. Like microbiology BSL-3 laboratories, BSL-3 insectaries are usually subjected to fixed-term or emergency room decontamination using recognized methods such as hydrogen peroxide (H₂O₂) or formaldehyde fumigation. While these procedures have been standardized and approved for the inactivation of diverse pathogens on surfaces, to date, there are no current standards for effective room-wide inactivation of insects in BSL-3 facilities in case of an emergency such as the accidental release of a large number of infected vectors. As H₂O₂ is often used for standard room decontamination in BSL-3 facilities, we evaluated H₂O₂ fumigation as a potential standard method for the safe, room-wide deactivation of insects in BSL-3 insectaries in comparison to heat treatment. To account for physiological diversity in vector insect species, six species from three different orders were tested. For the H₂O₂ fumigation we observed a strong but also varying resilience across all species. Lethal exposure time for the tested dipterans ranged from nine to more than 24 h. Furthermore, the coleopteran, Tribolium castaneum, did not respond to continuous H₂O₂ exposure for 48 h under standard room decontamination conditions. In contrast, temperatures of 50°C effectively killed all the tested species within 2 to 10 min. The response to lower temperatures (40–48°C) again showed a strong variation between species. In summary, results suggest that H₂O₂ fumigation, especially in cases where a gas generator is part of the laboratory equipment, may be used for the inactivation of selected species but is not suitable as a general emergency insect inactivation method under normal room decontamination conditions. In contrast, heat treatment at 48 to 50°C has the potential to be developed as an approved standard procedure for the effective inactivation of insects in BSL-3 facilities.

Safety Considerations for Malaria Volunteer Infection Studies: A Mini-Review

Malaria clinical studies entailing the experimental infection of healthy volunteers with Plasmodium parasites by bites from infected mosquitos, injection of cryopreserved sporozoites, or injection of blood-stage parasites provide valuable information for vaccine and drug development. Success of these studies depends on maintaining safety. In this mini-review, we discuss the safety risks and associated mitigation strategies of these three types of experimental malaria infection. We aimed to inform researchers and regulators who are currently involved in or are planning to establish experimental malaria infection studies in endemic or non-endemic settings.

A Cross-Sectional Survey of Biosafety Professionals Regarding Genetically Modified Insects

BACKGROUND

Genetic technologies such as gene editing and gene drive create challenges for existing frameworks used to assess risk and make regulatory determinations by governments and institutions. Insect genetic technologies including transgenics, gene editing, and gene drive may be particularly challenging because of the large and increasing number of insect species being genetically modified and the degree of familiarity with these organisms and technologies by biosafety officials charged with making containment decisions.

METHODS

An anonymous online survey of biosafety professionals was distributed to the membership of ABSA International, a global society of biosafety professionals, to investigate their perspectives on their preparedness to meet these new challenges.

RESULTS

Existing guidance used to make containment decisions for nongenetically modified insects was widely seen as adequate, and most respondents thought the available guidance for making containment decisions for genetically modified insects with and without gene drives was inadequate. Most respondents reported having less confidence in their decisions concerning containment of genetically modified insects compared to decisions involving genetically modified microbes, (noninsect) animals, and plants.

CONCLUSIONS

These results reveal a need for additional support for biosafety professionals to improve the quality of and confidence in containment decisions regarding genetically modified insects with and without gene drive. These needs might be addressed by increasing training, updating existing guidance, creating new guidance, and creating a third-party accreditation entity to support institutions. Sixty percent of the respondents said they either would or might use a voluntary third-party accreditation service to support insect containment decisions.

Human-mediated dispersal in insects

Central to the problem of biological invasions, human activities introduce species beyond their native ranges and participate in their subsequent spread. Understanding human-mediated dispersal is therefore crucial for both predicting and preventing invasions. Here, we show that decomposing human-mediated dispersal into three temporal phases: departure, transport and arrival, allows to understand how the characteristics of human activities and the biological traits of species influence each phase of the dispersal process, and ultimately govern invasion pathways in insects. Integrating these precise mechanisms into future invasion models should increase their realism and generalization for any potential insect invader. Moreover, understanding these mechanisms can provide insight into why some invasive insects are more widely distributed than others, and to estimate risks posed by species that have not yet been introduced.