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SS2 - Presentation on ACP & HLB - Handout
Medical Definition of Ko`- �+ ' ' �r�acy & P o t u 1 aTLUV Iv S MA 2b, D019 `> �:L. Koch's postulates: In 1890 the German physician and bacteriologist Robert Koch set out his celebrated criteria for judging whether a given bacteria is the cause of a given disease. Koch's criteria brought some much-needed scientific clarity to what was then a very confused field. Koch's postulates are as follows: • The bacteria must be present in every case of the disease. • The bacteria must be isolated from the host with the disease and grown in pure culture. • The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host. . The bacteria must be recoverable from the experimentally infected host. However, Koch's postulates have their limitations and so may not always be the last word. They may not hold if: • The particular bacteria (such as the one that causes leprosy) cannot be "grown in pure culture" in the laboratory. • There is no animal model of infection with that particular bacteria. A harmless bacteria may cause disease if: • It has acquired extra virulence factors making it pathogenic. • It gains access to deep tissues via trauma, surgery, an IV line, etc. • It infects an immunocompromised patient. • Not all people infected by a bacteria may develop disease -subclinical infection is usually more common than clinically obvious infection. Despite such limitations, Koch's postulates are still a useful benchmark in judging whether there is a cause -and -effect relationship between a bacteria (or any other type of microorganism) and a clinical disease NATIONAL ACADEMIES PRESS ► L3 BOOK Review of the Citrus Greening Research and Development Efforts Supported by the Citrus Research and Development Foundation.- Fighting oundation:Fighting a Ravaging Disease (2018) Chapter: Executive Surnniai-y Visit NAP.edu/10766 to get more information about this book, to buy it in print, or to download it as a free PDF. Executive Summary Huanglongbingl (HLB) or citrus greening, first observed more than a hun- dred years ago in Asia, is the most serious disease threat to the citrus -grow- ing industry worldwide due to its complexity, destructiveness, and incalci- trance to management. The bacterium Candidatus Liberibacter asiaticus, which is associated with HLB, is transmitted by the Asian citrus psyllid (ACP). First detected in Florida in 2005, HLB is now widespread in the state and threatens the survival of the Florida citrus industry despite substantial allo- cation of research funds by Florida citrus growers and federal and state agencies. In Florida, HLB research is overseen by the Citrus Research and Develop- ment Foundation (CRDF), a nonprofit corporation created in 2009 through the initiative of the state's citrus industry. In 2017, at the request of CRDF, the National Academies of Sciences, Engineering, and Medicine conducted a re- view of the foundation's research portfolio, with the goal of identifying ways to reconfigure HLB research to accelerate the development of tools and strategies to abate disease impacts and prevent the collapse of the Florida citrus industry (see the full statement of task in Chapter 1, Box 1-1). In its review, the committee found that research supported by CRDF and other agencies has expanded knowledge of every aspect of HLB, yet 1 Huanglongbing (HLB), which means yellow (huang) shoot (long) disease (bing), was unanimously adopted as the official name of the disease by the International Organization of Citrus Virologists (IOCV) at the 13th Conference of IOCV in Fuzhou, China, in 1995(llttp://ioc:v.org/huanglongbing.htni; accessed February 22, 2018). there have been no breakthroughs in HLB management. The reasons for the lack of breakthroughs in HLB management, despite the investments in re- search, are complex. Other than research on ACP in Florida, most of the available information on HLB prior to 2005 was based primarily on research performed outside the United States so researchers faced a steep learning curve. The disease itself is intractable for a variety of reasons related to the citrus host (its perennial nature, the lack of resistance in any citrus relative, and the difficulty of breeding to produce HLB-resistant cultivars); the pathogen (especially the inability to culture it in the laboratory); the insect vector (and its major role in transmission); the complexity of pathogen, vec- tor, and host interactions; the lack of a good model system; as well as the current approach to HLB research. The committee's analysis of HLB research outcomes allowed the commit- tee to identify progress and pitfalls in major research areas, and to identify research efforts that the committee believes should be continued or initiated. The committee regards the following as critical to achieve progress to- ward a viable HLB solution: • Building on knowledge generated through previous research • Supporting research on factors that influence adoption of management practices proven effective • Greater collaboration and more -frequent venues for information shar- ing by scientists • Timely and systematic communication of research outcomes and evalu- ation of research progress • Increased research coordination by CRDF and other funders of HLB research Citrus growers, particularly in Florida, still need short-term solutions to sustain the industry while researchers continue to generate longer-term ap- proaches for managing HLB, so support of basic and applied short- and long-term research is needed. Longer-term HLB solutions are likely to in- volve citrus variety improvement, derived primarily from new molecular techniques such as gene editing, and those efforts should focus on targets mediating molecular interactions among plant, bacteria, and vector. Because a single breakthrough discovery for managing HLB in Florida is unlikely, funders should support the development of sets of management ap- proaches that can be combined in different ways, optimized, and validated for use in different locations and conditions. This approach, founded on in- tegrated pest management, would allow optimization of management for each grower. Economic and sociological factors that impact decision making and be- haviors of growers, processors, and the public will influence the adoption and success of future HLB management efforts; hence, CRDF should consid- er funding these research areas and creating accessible databases to support sociological and economic modeling of HLB-related research outcomes and application projections. During its review the committee observed inconsistency in laboratory and field experimental designs and sampling methods. Because inconsistency limits the comparison of findings across teams and institutions and the use of previous research to inform further exploration, the development of com- munity -accepted standards to conduct, evaluate, and assess research should be supported. Improved consistency in reporting research outcomes is also needed to reduce constraints in reviewing research progress and delays in applying new information to HLB solutions. CRDF should develop a stan- dardized format and procedure, and set a timeline for mandatory reporting of project progress and final reports, to include publications and presenta- tions, outcomes, practical applications, and impacts. Despite commendable efforts of multiple agencies to coordinate funding and encourage appropriate interstate, interagency, and interdisciplinary col- laborations, the committee noted that decisions about research funding pri- orities and allocations occur largely within the domain of each agency, and it recommends that CRDF and other agencies work together to create an over- arching HLB research advisory panel to develop a fresh, systems approach to HLB research prioritization and the strategic distribution of resources for research leading to effective HLB management. This page intentionally left blank. The National Academies of Sciences, Engineering, and Medicine 500 Fifth St., NW I Washington, DC 20001 © 2019 National Academy of Sciences. All rights reserved.