NAADSM is a computer program designed to simulate the spread and control of foreign animal diseases in a population of susceptible livestock herds. Among the goals of the NAADSM project are the following:

  • To produce a practical, user-friendly modeling application suitable for the study of disease spread in the absence of an actual outbreak;
  • To offer a tool for the assessment and evaluation of proposed disease control strategies and preparedness planning purposes;
  • To provide support for researchers who will incorporate disease modeling in their work;
  • To offer outreach and training in the use of disease models in general and of NAADSM in particular to the scientific and veterinary medical communities in North America and abroad.

Key characteristics of NAADSM 

  • NAADSM is herd-based: disease manifestation and transmission are represented at the level of a herd of animals, rather than at the individual animal level.
  • NAADSM is a state transition model: each newly infected herd undergoes a transition from the susceptible state to an infected state to an immune state. Details of the state transition mechanism employed by NAADSM are presented in the NAADSM User's Guide.
  • NAADSM is a stochastic simulation: it attempts to imitate the random processes responsible for disease spread. Each simulated outbreak is the end result of a unique series of random events and processes. Taken together, many simulated outbreaks represent the range of possible outcomes, given the starting assumptions specified at the beginning of the simulation.
  • NAADSM simulates spatial and temporal aspects of disease spread: each herd in a scenario is assigned to a particular latitude and longitude (either real or hypothetical), and disease progression occurs in daily time steps.
  • NAADSM includes cost accounting components: the direct costs associated with simulated outbreaks may be estimated.

Critical notes

The outcome of an NAADSM simulation (as with any computer simulation model) depends heavily on the quality of the scenario input parameters; the assumptions of the modeler who created the scenario; and the capabilities and limitations of the model framework itself. The utility of disease models like those created with NAADSM critically depends on participation and interpretation of experts familiar with the behavior of disease within populations, and with the limitations, assumptions, and output of the model. Without such participation, modeling results can be seriously misleading.

While NAADSM is published as a service to the scientific and animal health communities, the NAADSM team does not necessarily endorse results obtained with the NAADSM application or any conclusions drawn from such results.

Obtaining NAADSM

NAADSM is open source software and is released under the terms of the GNU General Public License.

An executable version of NAADSM for Microsoft Windows may be downloaded from this website. Source code for NAADSM for Microsoft Windows as well as for a variety of other operating systems is also available.


A detailed user's guide and a description of the conceptual model implemented in the NAADSM application are available: please refer to Documentation for details.