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Understanding Reportable Diseases

For a horse owner, receiving a positive test result from your veterinarian for an equine infectious disease can be scary and overwhelming. What is the disease? How did my horse contract it? What happens now? What is the role for state and federal animal health officials in disease control management?
Because some infectious diseases can cause significant number of sick horses and deaths and are easily spread, individual states and the United States Department of Agriculture (USDA) act on reportable diseases to prevent disease spread.

Upon receiving the positive result, a horse owner might ask themselves what is a reportable disease? A “reportable disease” is defined as having the potential for significant equine health and economic impact on the equids of the United States. The list of reportable diseases is based on international, national, and local diseases of concern. At the international level, the World Organization of Animal Health (WOAH) determines diseases of significant impact which countries must report. At the country level, the USDA must report detections of those diseases and determine if there are additional diseases of concern for the United States which must be reported by the individual state veterinarians. Lastly, state veterinarians with input from their equine industry determine what diseases of concern should be reported within their state.

The list of WOAH reportable disease can be found at https://www.woah.org/en/what-we-do/animal-health-and-welfare/animaldiseases/?_tax_animal=terrestrials%2Cequine, while the USDA list can be located at https://www.aphis.usda.gov/sites/default/files/nlrad-nahrs-disease-list.pdf. The Equine Disease Communication Center (EDCC) provides a list of reportable and actionable and reportable and monitored diseases in each 50 states plus Canadian Providences on its website at https://equinediseasecc.org/report-adisease.

“Each state is different because each state assesses their own risk and determines what disease they think are important to control from a regulatory standpoint,” said Dr. Katie Flynn, current senior veterinarian for equine health and biosecurity at US Equestrian and former Kentucky State Veterinarian.
It might seem easier at first glance to create a standardized list of reportable diseases for all states, but Dr. Heather Roney, Wisconsin state animal health official, said, “There are diseases that are common in other states that would be novel or unreported in Wisconsin. So, this (standardized list) is likely not practical or useful. There are some diseases that are federally reportable, our list of reportable diseases would be inclusive of those on the National List of Reportable Animal Diseases from the USDA.”
To determine what diseases are placed on their reportable and monitored list Washington state animal health official, Dr. Ben Smith, said his office works alongside diagnostic labs and the department of health, along with the WOAH guidelines, and includes diseases that are contagious and infectious and of economic importance to the state.

Individual states break their reportable diseases into classifications such as Reportable and Actionable, Reportable and Monitored, and Not Reportable. For example, WOAH and USDA require equine infectious anemia (EIA) to be reportable so that is on all lists in each state. Strangles is reportable and actionable in Kentucky but is not considered reportable in Indiana or Texas. Both Virginia and Florida consider eastern equine encephalitis (EEE) as reportable and monitored but not actionable. Pigeon fever is not reportable in Maryland but is reportable and monitored in Washington. Because this can be confusing, owners and veterinarians should be aware of what diseases are reportable in their state.

Some reportable diseases are on the list for monitoring or surveillance purposes only, meaning the state and the USDA are monitoring the disease occurrences for early identification of any changes in the disease such as increased in clinical disease, change in geographic occurrence of the disease, or change in frequency of detection. For example, some reportable disease lists contain equine influenza as a monitored reportable disease. Equine influenza is caused by a virus that can mutate and change how it affects horses. By being on the reportable disease list, animal health officials can monitor for any changes in clinical manifestations, frequency of detection, seasonality of detection or geographic distribution.

Once the infectious disease diagnosis has been given to the owner by the veterinarian, who reports it and to where? And what happens to the horse and premises where it is kept? Some state laws require the veterinarian and laboratory to report while other states’ laws mandate anyone who has knowledge, such as the horse owner, to report the suspected reportable disease.

“The general recommendation is for anyone suspecting a reportable disease to contact a local, state, or federal animal health official- a representative of the state veterinarian’s office or of the local USDA- Animal Plant Health Inspection Service (APHIS) Veterinary Services,” Flynn said.

State animal health officials work with private practitioners to ensure they know when and how to report positive test results to the state veterinarian’s office. Smith said his office provides educational training and outreach to veterinarians to review the reporting process and to answer any questions about what and how to report.

Private practitioners are not required to report non-reportable diseases to the state offices. “Reporting all non-reportable diseases would overwhelm our limited resources,” Roney said. “Additionally, some reportable disease results for endemic diseases are reported by the testing laboratory, and we may or may not reach out to the private practitioner for more information about the case.”

Once the disease has been reported, each state determines how to respond, specifically whether the disease detection will be actionable or monitored. Actionable responses typically involve a quarantine and movement restrictions while a monitored response focuses implementation of biosecurity and monitoring of disease progression where the horse is located. There is no standard response for any one disease as each response will be dependent upon the disease agent detected, the equine population, and the environment.

It is important for horse owners to work with their state animal health officials in advance of an outbreak to know what you can expect if a reportable disease were to occur. Working in advance with these officials will ensure prompt and coordinated response at the time of detection. Delay in initial detection and isolation of the sick horse shedding the infectious disease agent, typically leads to increased number of horses exposed and sick as well as longer duration of disease outbreak.

The goal of any response to a reportable disease is to stop spread of the disease pathogen to protect equine health. The three core pillars of response are: 1). Early identification of infected horses with health monitoring and diagnostic testing; 2). Immediate isolation of horses suspected or confirmed with a reportable disease pathogen; and 3). Enhanced biosecurity to reduce bacteria or virus in the environment and to prevent further transmission.

To best protect the health of equines, isolation, and movement restrictions of horses’ sick with an equine infectious diseases are essential, especially for highly contagious diseases. It is critical for a horse shedding an equine infectious disease agent to be isolated to prevent exposure to other horses.
To effectively monitor and mitigate the spread of infectious disease, the EDCC reports on confirmed cases and diseases that have been submitted by state animal health officials or an attending veterinarian. Veterinarians are encouraged to report all cases with a confirmed diagnosis of an infectious or vector borne disease, including outbreaks and cases of non-reportable diseases.

This is particularly important when there is an increased risk of disease spread due to commingling of horses at equine events. The cases are then published on the EDCC website https://equinediseasecc.org/alerts and shared to the EDCC Facebook page. The EDCC issues alert notification emails to subscribers at the end of the day.