Pathways Analyses for the Introduction to the U.S. of Plant Pathogens of Economic Importance Prepared by the National Agricultural Biosecurity Center Consortium Kansas State University Purdue University Texas A&M University August 2004 List of Contributors Kansas State University Karen A. Garrett (POC) John C. Reese (POC) Leslie R. Campbell Shauna P. Dendy J.M. Shawn Hutchinson Nancy J. Leathers Brooke Stansberry Purdue University Ray Martyn (POC) Don Huber Lynn Johal Texas A&M University Joseph P. Krausz (POC) David N. Appel Elena Kolomiets Jerry Trampota Project Manager Jan M. Sargeant, DVM, MSc, PhD, Kansas State University and McMaster University, Hamilton, Canada List of Contributors 1/1 Plant Pathways Analysis Table of Contents List of Contributors.............................................................................i-1 Methodology for Pathway Analysis of an Intentionally Introduced Plant Pathogen ...........................................................ii-1 A Conceptual Framework for the Analyses of Pathways for the Introduction of Plant Pathogens .................................................iii-1 SOYBEAN Mosaic Virus...................................................................................1-1 Rust.................................................................................................2-1 CORN Late Wilt..........................................................................................3-1 Philippine Downy Mildew .............................................................4-1 RICE Bacterial Leaf Blight .....................................................................5-1 Bacterial Leaf Streak .....................................................................6-1 CITRUS Huanglongbing...............................................................................7-1 Citrus Variegated Chlorosis..........................................................8-1 WHEAT Karnal Bunt ....................................................................................9-1 Slime Disease...............................................................................10-1 SORGHUM Sorghum Ergot.............................................................................11-1 Brown Stripe Downy Mildew.......................................................12-1 Methodology for Pathway Analysis of an Intentionally Introduced Plant Pathogen Lynn Johal, Don Huber, Ray Martyn Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN The terrorist events of September 11, 2001 and subsequent bioterrorist anthrax attacks have resulted in the legitimate concern over U.S. vulnerability to agricultural bioterrorism. Agricultural targets offer terrorists a virtually open area to assault, often with little cost or expertise required and with a potential for high probability of inflicting significant economic impact on U.S. agriculture. Analysis of potential pathways for exotic disease entry and establishment, and assessment of U.S. capacity to minimize the impact of such an introduction can form a basis for developing safeguards to ensure rapid detection, containment and mitigation in the event of an attack. Pathway analyses provide a tool for assessing the potential threat of an introduced plant pathogen to the U.S. and thereby help policy makers allocate resources wisely. A basic conceptual framework for pathway analysis of an introduced plant pathogen can be applied as new disease risks arise or when changes occur that affect the risks associated with known pathways or diseases. The plant pathways methodology developed and applied herein has two primary components, a) a disease introduction and development pathway and, b) an associated response strategy pathway to minimize disease impact and enhance preparedness (Fig. 1). All areas of the pathway are founded on a thorough review of the biology and epidemiology of the pathogen. This includes pathogen identity, hosts, geographic distribution and impact, Methodology 1/6 disease cycle and epidemiology, symptoms, and methods of detection. If vectors are involved in secondary spread of a pathogen, the vector’s life cycle, alternate host distribution, transmission ability, etc. must be incorporated in the analysis. Published and unpublished literature, along with personal communication with experts, develops the most comprehensive base possible. Knowledge gaps in pathogen epidemiology, establishment in the U.S. and control/mitigation strategies are then identified. A list of knowledgeable scientists with contact information should be included for each pathogen. A disease introduction and development pathway initiated by covert action (Fig. 1a), reviews means and materials for intentional introduction. The probable route of terrorist entry, propagule(s) for initiation, ease of propagation and dissemination, and quantity of propagule(s) required, all contribute to understanding the probability of a successful introduction. On introduction, rapid detection can modify the likelihood of successful establishment, potential disease spread, and mitigation. The pathogen was assigned a qualitative risk (high, moderate, or low) of successful introduction and establishment based on 29 different criteria (Appendix 1). The likelihood of successful introduction was broken down into 5 categories. These included: quantity of inoculum required to introduce and establish damage, likelihood of surviving initial introduction, likelihood of dissemination beyond the point of introduction, likelihood of alternate host infection and likelihood of early detection. Risk establishment was rated with respect to six elements: climate, host range, dispersal, persistence, economic impact, and environmental impact. The first four risk elements provided a basis for prediction of the pathogen's survival and disease distribution ranges. When available, predictive models for the pathogen or disease distribution patterns of taxonomically related pathogens with similar biology were employed. The site of introduction within the U.S. influences outcome and may result in more than one disease development pathway scenario. Finally the pathogen was assigned an over-all risk rating. The response strategy pathway (Fig. 1b) indicates where and how intervention can curtail impact. The initial step considers how an attempted introduction can be recognized (“Initiating event”) through observation/diagnosis of presence, interception, and “Intelligence” information. The diagnostic and action pathway recently developed by NPDN (National Plant Diagnostic Network) coordinates the movement of samples and data, as well as communication between various responders (Fig. 2). The following questions complete the Methodology 2/6 basic structure of the response pathway. How can rapid diagnosis/detection be improved? Is containment and eradication of the pathogen possible? If so, what is the best containment response? After a thorough inventory of control and mitigation methods, what will be the best control strategy in the U.S.? Are any regulatory or legal changes required in order to reduce potential entry of the pathogen or implement post-introduction strategies? Optimum immediate response options to minimize impact of an introduced exotic pathogen complete the pathway. Methodology 3/6 Figure 1. Generic plant pathogen pathway analysis and response summary a. Disease introduction and development pathway Probable Site of Rate of Risk of pathogen introduction method introduction potential establishment disease Bioterrorist spread (for Route of introduction; Requirements for Qualitative Consequences (covert entry) each regional Includes: identifying & likelihood of ranking of of introduction scenario) potential vehicle(s) successful climate, host & Overall Source of introduced, quantity of introduction. range, dispersal establishment: risk of pathogen; 1. likelihood propagules required, Site influences and persistence economic, pathogen pathogen of extensive equipment needed, outcome and may allows prediction psychological, to U.S. (inoculum) abiotic delivery method, etc. result in >1 of eventual & production secondary disease disease environmental spread development distribution and risks scenario. survival ranges 2. vectors? b. Response strategy pathway i.e. Where and how can we interact to reduce risk? How can likelihood of early detection be How can we Identify improved? recognize an attempted 1. knowledge gaps introduction? in pathogen Trained first Sample collection epidemiology responders Data recording 1. diagnosis pertinent to 2. interception establishment in Inventory 3. intellegence U.S. control & mitigation 2. scientists First diagnosis strategies knowledgeable Land Grant Quality control about pathogen Diagnostic Communication PIN (Port Information Develop immediate Authority) Pathway Action NPDN response options Homeland 1. best control Security, NSA, Diagnosis confirmation strategies Regional Ongoing CIA, DIA, FBI, Coordination Diagnostic response or USDA-PPQ Communication 2. regulatory Centers measures 3. economic support Is containment & eradication possible? Identify continued Yes No research needs National data synthesis Detection On-site threat Mapping NAPIS Assessment assessment; Real time monitoring team - determine APHIS distribution and quarantine area APHIS/State Initiate eradication; Departments determine method of Agriculture Disease Failure to contained & contain eradicated disease Methodology 4/6 Figure 2. Sampling + diagnostic data and action pathways for NPDN Sampling & Diagnostic