An important tool for veterinary epidemiology
Outbreaks of highly contagious animal diseases, such as Foot-and-Mouth Disease (FMD) and Highly Pathogenic Avian Influenza (HPAI) can have severe consequences. The economic costs and production losses of such an outbreak can be significant. Measures for disease prevention provide a first line of defense, but appropriate contingency planning for implementation of disease control strategies is also essential.
The design and evaluation of policies for the control of highly contagious diseases are not tasks that lend themselves to field experimentation: it is not practical to experimentally determine the extent of a disease outbreak or to test large-scale mitigation strategies under actual field conditions. Instead, investigators rely on alternatives, such as computer-driven simulation modeling. Computer models allow researchers to estimate the potential impact of disease outbreaks, to design disease control strategies, and to inform policy decisions regarding outbreak response plans, all without affecting even a single animal.
Since its founding in 2002, the Animal Population Health Institute (APHI) at Colorado State University has been involved in the creation and use of epidemiologic simulation models. The centerpiece of modeling efforts at APHI is the North American Animal Disease Spread Model.
The North American Animal Disease Spread Model (more commonly known as NAADSM) is a computer program used to simulate the spread of disease in animal populations and to evaluate different disease control strategies, thereby providing information for emergency response plans and policy. NAADSM is the product of a long-standing multinational collaboration involving APHI and many US and international partners.
Emergency responders throughout the US have used NAADSM for training exercises to evaluate responses to disease outbreaks. NAADSM is now recognized and used worldwide by government agencies, academic researchers, and other investigators. APHI is at the forefront of this activity and is involved in the ongoing development and application of NAADSM.
NAADSM is best suited to the simulation of highly contagious diseases in livestock and poultry populations. It is not currently designed to simulate diseases that are chronic, endemic, vertically or sexually transmitted, or transmitted by insects or other vectors. Initial efforts to expand the application of NAADSM to wildlife populations and to wildlife and livestock interactions are now underway.
International outreach with practical applications in the US
Since 2007, more than 200 participants from 22 countries have attended NAADSM training courses conducted by APHI personnel, and many have gone on to apply the model to problems in their own countries. This international outreach makes a valuable contribution to disease response plans for the United States, as well. For example, there has not been an outbreak of FMD in the United States for over 80 years, but outbreaks continue to occur in several countries in South America. Through the NAADSM project, APHI has established or strengthened ties with several South American countries as well as with the Pan American Foot-and-Mouth Disease Center (PANAFTOSA) in Rio de Janeiro, Brazil. The experience of experts in the region and access to detailed information regarding recent outbreaks of FMD help APHI and our collaborators to enhance the capabilities of NAADSM and to improve our understanding of the nature of major animal disease outbreaks.
A network of professionals
APHI’s partnering institutions in NAADSM development are the US Department of Agriculture; the Canadian Food Inspection Agency; the Ontario Ministry of Agriculture, Food, and Rural Affairs; the University of Guelph; and the University of Prince Edward Island. Because the USDA Centers for Epidemiology and Animal Health (CEAH) are located on the CSU campus, APHI works closely with CEAH in NAADSM development and collaborates on many projects. Members of each team help to provide expertise on various topics related to disease modeling and risk assessment, from assessing contact rates among livestock species to the economic impact of a disease outbreak.
The CSU APHI NAADSM Team
L to R: Aaron Reeves, Ric Hupalo, Shaun Case, Dr. Marna Sinclair,
Deborah Batista, and Dr. Sangeeta Rao
The APHI NAADSM Team
Current members of the CSU APHI NAADSM Team are Aaron Reeves, Ric Hupalo, Shaun Case, Dr. Marna Sinclair, Deborah Batista, and Dr. Sangeeta Rao.
Aaron Reeves joined APHI in 2004 and has been actively engaged in the development and application of epidemiologic models for a variety of diseases of livestock and poultry. He assists with development of new versions of the NAADSM model and is the primary instructor for the Epidemiological Simulation Modeling Course presented to domestic and international researchers by APHI.
Ric Hupalo works primarily with development and maintenance of the NAADSM user interface and testing beta releases of NAADSM. Other projects have involved creating software for APHI related projects, wildlife modelinginvestigation, and GIS support for the team's epidemiologists.
Shaun Case has beenworking on the NAADSM Team (Infectious Disease Modeling Group for APHI) for just over 5 years. As a software engineer, he helps with the development of new versions of the NAADSM model and with improvements and design of features for the modeling framework. He also trains and assists researchers and foreign governments with the use and application of the model, and is also working on the adaption of NAADSM for use in Turkey as well as other FMD endemic countries.
Dr. Marna Sinclair is on the Infectious Disease Modeling Team of APHI. Her main responsibilities are to help with beta-testing of new versions of NAADSM as well as the application of the model in different settings. She is also currently working on a project which aims to obtain better information regarding contacts between different livestock operations in Colorado and Kansas. The data obtained from this project will help to better parameterize disease spread models in these two states. For more information about this project visit www.livestockcontactstudy.org.
Deborah Batista joined the APHI team in November 2010. Her research has been focused on finding appropriate nonparametric statistical tests for comparing outputs from the North American Animal Disease Spread Model (NAADSM). She also works as a beta tester of NAADSM identifying issues in the software prior to public releases. Currently, she is working on the adaptation of NAADSM for use in Turkey as well as other FMD endemic countries.
Dr. Sangeeta Rao began working with the model earlier this year, and is currently is the lead person for the Updated Site Specific Risk Assessment (USSRA) project from Department of Homeland Security for the planned National Bio and Agro-Defense Facility (NBAF) in Manhattan, Kansas. This assessment is tasked with describing risk reduction and mitigation strategies related to conducting essential research and diagnostic testing at the NBAF.
The USDA CEAH NAADSM Team
L to R: Kelly Patyk, Dr. Chad Eshelman,
Dr. Kim Forde-Folle, Dr. Eihab Fathelrahman.
Not pictured: Drs. Barbara Corso, Jane Rooney, and Tim Boyer
The USDA CEAH NAADSM Team
Current members of the USDA CEAH NAADSM Team are Drs. Chad Eshelman, Kim Forde-Folle, Eihab Fathelrahman, Barbara Corso, Jane Rooney, Tim Boyer, and Kelly Patyk.
Dr. Chad Eshelman is a statistician and computer modeler working through the University of Minnesota. Major responsibilities include meta-analysis and development of statistical distributions associated with input parameters of NAADSM, exploration of analysis options of output data associated with NAADSM and development of external software used for data extraction, organization and spatial analyses of NAADSM output.
Dr. Kimberly Forde-Folle is a Veterinary Epidemiologist at the Centers for Epidemiology and Animal Health in Fort Collins, Colorado. Dr. Forde-Folle acts as the primary adviser on the North American Animal Disease Spread Model to USDA, APHIS, VS. In this role, she partners with epidemiologists, veterinarians, economists, disease modelers, programmers, research associates, and other experts on matters related to infectious animal disease simulation modeling.
Dr. Eihab Fathelrahman is an Agricultural Economist with the USDA APHIS VS Centers for Epidemiology and Animal Health Office of International Collaboration & Coordination. In his current position, Dr. Fathelrahman supports the cost estimates and economic modeling and analysis for the North American Animal Disease Spread Model (NAADSM). His current NAADSM applications include modeling highly pathogenic avian influenza (HPAI) virus detection capacity in South Carolina, Foot-and-Mouth Disease vaccination strategies, and integration of NAADSM results with the economics models analyses.
Dr. Barbara Corso is a Veterinary Epidemiologist, currently with the Risk Analysis group at CEAH. She has worked with the NAADSM model for many years, starting early in the development, verification and awareness of the model. She uses NAADSM to address concerns in exposure and consequence analysis.
Dr. Jane Rooney is a Senior Staff Veterinarian with the National Center for Animal Health Emergency Management (NCAHEM). As a member of the Interagency Coordination staff Jane works to build partnerships with Federal, State, and local entities to strengthen early disease detection and rapid response at all levels; identify resources and clarify roles in the event of an animal health emergency. Major responsibilities include: coordinating APHIS Animal Disease Spread Modeling efforts at the national level and as an interagency liaison for the VS Animal Disease Modeling Team.
Tim Boyer is an epidemiologist with the National Center for Food Protection and Defense at the University of Minnesota. Tim collaborates with CEAH to develop disease spread models using NAADSM. He also participates in NAADSM Development Team activities to verify new versions of NAADSM.
Kelly Patyk is a senior veterinary student at Colorado State University and a recipient of the Saul T. Wilson Jr. Veterinary Scholarship. Her primary work has been to assist with developing parameters to address highly pathogenic avian influenza modeling in NAADSM.
Recent publications from NAADSM Team members are included in Volume 30, Issue 2 of the 2011 OIE Revue Scientifique et Technique titled Models in the Management of Animal Diseases, which is edited by P. Willeburg. Authors and article titles are provided below:
- A. Reeves, M.D. Salman, and A.E. Hill. Approaches for evaluating veterinary epidemiological models: verification, validation and limitations
- R.L. Swanson, N. Harvey, M.G. Garner, M.A. Stevenson, T.M. Davies, M.L. Hazelton, J.O. O’Connor, C. Dube, K.N. Forde-Folle and K. Owen. Foot and mouth disease model verification and ‘relative validation’ through a formal model comparison.
- K. Forde-Folle, D. Mitchell and C. Zepeda. The role of models in estimating consequences as part of the risk assessment process.
- K. Patyk, C. Caraguel, C. Kristensen and K. Forde-Folle. Lexicon of disease spread modeling terms.
- C. Dube, J. Sanchez and A. Reeves. Adapting existing models of highly contagious diseases to countries other than their country of origin.
NAADSM is a freely distributed open source software package. There are now registered NAADSM users in 31 countries. The software and documentation are currently available in English and Spanish. To learn more about NAADSM or to obtain your own copy of the latest version, please visit the NAADSM website at http://www.naadsm.org.