Containment Standards for Facilities Handling Plant Pests
2.0 Plant pest containment
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2.1 Pest biology and containment
In order for a plant pest to survive, establish and spread in an environment, the following conditions must be met: 1) the pest must be able to find a suitable host; 2) susceptible material (e.g. plant tissue) must be available; and 3) the environment must be conducive to the pest's establishment and development. These three factors must all occur over a sufficient and overlapping period of time. Natural limitations to any one of the three factors and/or human intervention, such as the use of chemical or biological controls can influence pest establishment or spread. Thus, plant pests can be contained by spatial and temporal isolation from their hosts, either in the natural environment or in containment facilities.
In order to prevent the escape and the establishment of plant pests in the environment, the facilities that work with such pests and their operating procedures must be appropriate to the biology of the specific pests under consideration. In addition, the operating procedures must prevent the introduction of organisms into the facility that could contaminate, kill or transmit contained pests. Singh (1999) states that: "Containment requirements for various pathogen [and other pest] groups will vary according to the pest risks they pose to...agriculture because of their unique biologies, particularly their modes of dispersal, and their survival potential under adverse conditions." In the absence of arthropod vectors, organisms such as bacteria, viruses, phytoplasmas and nematodes generally have no means of becoming dispersed over long distances. Arthropods can actively disperse or be passively dispersed by air currents; however, their spread can be prevented by sealing facilities in which they are kept and by using appropriately sized filters and screening. Fungi that are not well adapted for aerial dispersal can also be contained fairly easily, but those fungi that produce spores adapted for efficient aerial dispersal are very difficult to contain and may require the use of sealed facilities with HEPA filtered ventilation systems. Containment precautions must also be appropriate to the proposed type of work. Containing pests in vitro (e.g. as pure cultures on petri plates) is inherently easier than containing pests in vivo (e.g. on infected or infested plants) and, similarly, containing pests in small-scale experiments presents a lower risk of pest escape than containing them in large-scale experiments.
Effective containment involves the use of trained personnel, appropriate and documented operational procedures, effective use of primary containment devices and facilities designed to limit access to authorized personnel.
2.2 Risk assessment, risk management and containment
Facilities that handle plant pests should be constructed and operated to achieve the containment levels required for the pests concerned. The level required depends on the risk of the plant pest escaping and becoming established in the environment and on the environmental, economic, agricultural, forestry and trade consequences of such an introduction.
To provide a framework for ensuring appropriate biological containment in facilities that work with plant pests in Canada, a containment classification system has been developed that is consistent with the systems for human and animal pathogens. It has four containment levels: Basic; Plant Pest Containment Level 1 (PPC-1); Plant Pest Containment Level 2 (PPC-2); and Plant Pest Containment Level 3 (PPC-3). Physical and operational requirements for these levels are described below (section 2.3) and comprehensive and detailed descriptions for PPC-1, PPC-2 and PPC-3 are discussed in sections 3 (Physical Requirements) and 4 (Operational Practices) of this document. The containment requirements for a particular organism are frequently project-specific, and are determined after assessing pest risk factors such as:
- the known presence or absence of the organism in Canada;
- its host range and the local presence of potential hosts;
- the existence of, or the potential for, significant organism biotypes or strains that are exotic to an area;
- the history of the organism in other new environments;
- the virulence or aggressiveness of the organism;
- the availability of pest risk information;
- the nature of the proposed work (in vitro, in vivo or large-scale in vivo);
- the location, proximity of suitable hosts and time of year of the proposed work;
- the mode of transmission or spread (e.g. active flight, passive airborne, contact, soil-borne, water-borne);
- its potential rate of local and long-distance spread;
- the presence of vectors in Canada (e.g. arthropods, fungi, nematodes);
- the presence of vectors in or near the containment facility;
- the persistence of the organism in the environment and its potential for overwintering;
- environmental requirements for establishment and spread;
- the potential capacity to control or eradicate the organism if it escapes;
- the potential for economic or environmental loss from the organism;
- the economic and environmental significance of potential pest organisms and their host plants; and
- biosecurity-related risks (e.g. the potential for theft and misuse).
Based on a review of the above, regulatory scientists make risk management recommendations aimed at reducing the risk of organism escape and establishment in Canada. Appropriate containment levels are determined by a reviewer who uses the conceptual risk model (Figure 1) shown below. The risk model demonstrates the general principle of requiring increased levels of containment with increasing risk of pest escape and establishment and increasing economic, environmental, agricultural, forestry and trade consequences associated with an escape. There are many methods of assessing risk.
Graphic 1 is a simplified graphical representation of how risk can be categorized for plant pests.
2.3 Plant pest containment levels
Regardless of the containment level of the facility, the physical attributes of the facility and the operational procedures must be suitable for containing the pest(s) under consideration and should be tailored to that purpose. In view of the variables involved, the appropriate containment of plant pests must be determined on a case-by-case basis and specific applications may require precautions in addition to those described for each of the containment levels.
The concept of biological containment is usually applied to work done in buildings, growth chambers or greenhouses which have, or present, physical barriers to prevent the escape of pests. Although the concept of biocontainment under field conditions seems contradictory, there are some pests that can safely be contained under quarantine conditions in the field. For example, areas with natural geographic isolation (e.g. islands), a local absence of susceptible host tissue or a climate unsuitable for long-term pest survival may be effective in preventing the escape and establishment of particular plant pests.
Comprehensive descriptions of each containment level are provided in sections 3 (Physical Requirements) and 4 (Operational Practices). Simplified facility diagrams for PPC-1, PPC-2 and PPC-3 are presented in Appendix 1. The following brief descriptions explain the major features of each containment level and provide illustrative examples of the type of plant pest work that would be appropriate at each level.
Basic containment is the lowest containment level for plant pests and it provides simple, but adequate, barriers to pest escape. Facilities may consist of field plots, basic laboratories or simple glass, plastic or screen houses which may have dirt or gravel floors and unscreened vents. Containment of plant pests is achieved through sanitation (see 184.108.40.206), spatial isolation from susceptible hosts, physical security, signage, destruction of waste and destruction of all viable pests at the end of the experiment or the testing period. Basic containment is applicable for work with low to very low risk plant pests for scientific, research, educational, processing, industrial or exhibition purposes.
The following are examples of the types of work that could be appropriately conducted (with or without supplemental conditions) in Basic containment:
- establishing a field plot using plants infected with a virus that can only be transmitted by grafting;
- using lyophilized virus-infected plant tissue as a control in an ELISA test; or
- using plant tissue infected with a common strain of tobacco mosaic virus to inoculate tobacco plants for a high school biology project.
2.3.2 Plant Pest Containment Level 1 (PPC-1)
PPC-1 containment is the next highest containment level for plant pests. Facilities include permanent structures such as laboratories, greenhouses and screenhouses. Windows that can be opened must be fitted with appropriate screens, and greenhouses must be fully screened and caulked to both contain and exclude arthropods. An autoclave must be available to treat waste and waste water must be treated to kill pests where appropriate.
The following are examples of the types of work that could be appropriately conducted (with or without supplemental conditions) in PPC-1 containment:
- inoculating host plants with isolates of plum pox or other plant viruses in the absence of the vectors of those viruses;
- importing low-risk tropical insects into butterfly houses for study, display or rearing; or
- studying and rearing nematodes of quarantine concern in Canada that have low spread potential (e.g. Globodera rostochiensis and Ditylenchus destructor).
2.3.3 Plant Pest Containment Level 2 (PPC-2)
PPC-2 facilities include permanent structures such as laboratories and greenhouses but not screenhouses. Containment is achieved through facility design, operational procedures and the use of specialized equipment. All PPC-1 physical and operational requirements also apply to this containment level.
Key additional operational practices include:
- use of primary containment devices;
- use of dedicated or disposable laboratory clothing;
- appropriate decontamination of solid and liquid waste;
- pest monitoring and regular inspection of screens, filters and caulking for defects;
- clear documentation of standard operating procedures (SOPs);
- mandatory personnel training; and
- the availability of suitable emergency response plans.
Key additional physical requirements include:
- restricted access via an anteroom;
- an on-site autoclave; and
- greenhouses that are mechanically ventilated with screened or filtered inlet and exhaust air.
Key additional physical requirements for PPC-2 arthropod facilities include:
- sealing or screening all penetrations into the work area;
- inward directional airflow; and
- access via a dedicated anteroom.
The following are examples of the types of work that could be appropriately conducted (with or without supplemental conditions) in PPC-2 containment:
- conducting plant inoculations with an isolate of Ralstonia solanacearum Biovar 2, Race 3, the causal agent of potato brown rot disease;
- morphological examination and DNA extraction of sporangia of Synchytrium endobioticum, the causal agent of Potato Wart, and their use as diagnostic controls;
- growing chrysanthemum plants infected with Puccinia horiana, the causal agent of chrysanthemum white rust;
- rearing the arthropod pest Anoplophora glabripennis, the Asian longhorned beetle;
- conducting plant inoculations with specific races of the corn pathogen Helminthosporium turcicu;
- conducting fruit inoculations in a laboratory using Alternaria gaisen, the causal agent of Black Spot of pear; or
- culture work with, and diagnostics for, Phytophthora ramorum, the causal agent of Sudden Oak Death.
2.3.4 Plant Pest Containment Level 3 (PPC-3)
PPC-3 is the highest containment level for plant pests. All PPC-1 and PPC-2 physical and operational requirements apply to this containment level. Containment is achieved through the use of specialized facilities, stringent operational procedures and the use of specialized equipment. Designing, constructing and maintaining a PPC-3 greenhouse facility is complex and expensive. The use of growth chambers or growth rooms within a PPC-3 facility can be a cost-effective alternative to constructing a PPC-3 greenhouse.
Key additional operational practices include:
- designation of a person with responsibility for the overall operation of the facility;
- a high level of physical security;
- restricted access with a log being kept of personnel and visitors entering the facility;
- full clothing change before entering the facility with the possibility of washing or showering on exit, if required;
- checks to confirm inward directional airflow and regular inspections for deterioration in seals; and
- a procedural manual, including standard operating procedures (SOPs), that addresses all emergencies including those relating to containment.
Key additional physical requirements include:
- dedicated anterooms with change areas;
- sealed facilities with inward directional airflow from "clean" to "dirty" areas;
- HEPA filtered exhaust air;
- drains routed to an effluent treatment system;
- electronic data transfer capability;
- emergency power for critical containment systems; and
- break-resistant glazing for greenhouses.
The following are examples of the types of work that could appropriately be conducted (with or without supplemental conditions) in PPC-3 containment:
- conducting plant inoculations with isolates of Phakopsora pachyrhizi, the causal agent of Asian Soybean Rust, in an area in close proximity to susceptible hosts;
- conducting plant inoculations with imported isolates of Gymnosporangium yamadae, the causal agent of Japanese Apple Rust, in an area in close proximity to susceptible hosts;
- biocontrol research with exotic microbial plant pests that are difficult to contain and in cases where the establishment risks are poorly documented; or
- conducting plant inoculations with pests of environmental and/or economic concern that have a high establishment and/or trade potential risk and that produce airborne spores, such as the pathogen Phytophthora ramorum.
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