Pyres: 2001 UK FMD Outbreak - Photo: Murdo Macleod. Slides L-R: Smallpox, SARS Coronavirus , Foot and Mouth Disease, West Nile Virus.
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6 March 2005: Updated 15 March 2013

Contact: Stephen M. Apatow
Founder, Director of Research & Development
Humanitarian Resource Institute (UN:NGO:DESA)
Humanitarian University Consortium Graduate Studies
Center for Medicine, Veterinary Medicine & Law
Phone: 203-668-0282
Email: s.m.apatow@humanitarian.net
Internet: www.humanitarian.net

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Antibiotic Resistance - Enteric Disease


 Several years back, one of my clients had a top level dressage horse heading for Gran Prix, that presented acute illness prior to a show in in the Western United States.  The horse was shipped to a diagnostic lab, testing negative for salmonella upon admission, but positive during the observation period.  The horse never fully recovered, leaving the owner/trainer devastated, with significant expenses associated with veterinary care.
In recent years there have been important changes in antibiotic therapy in equine practice. There are new antibiotics available and there is more information available on the antibiotics used in horses. Concerns over drug residues in food animals and antibiotic resistance has lead to the development of the Canadian Veterinary Medical Association's Prudent Use Guidelines. These guidelines stress obtaining a diagnosis and selecting appropriate antibiotic therapy. In practice situations, it is often difficult to submit samples for microbiologic culture and antibiotic susceptibility testing. Practitioners often choose antibiotics selection based on data from university teaching hospitals and veterinary diagnostic laboratories from other parts of Canada, the United States and even Europe.  -- P. M. Dowling, "Bad Bugs, Bad Bugs, Whatcha Gonna Do?,"  presented at, and appears in the Proceedings of, the 2003 Alberta Horse Breeders and Owners Conference, 11 March 2003.

Since no commercially available vaccine exists for pathogens such as Salmonella, disinfection and other biosecurity practices must be utilized in order to prevent the introduction or the spread of this disease. -- Animal Health Advisory: Multi Drug Resistant Strains of Salmonella in Horses, Cornell’s College of Veterinary Medicine, June 2004.

The following microbiologic culture and antibiotic susceptibility test demonstrates the level of antibiotic resistance recently isolated at livestock operations in the United States.  Disclosure of such findings, by the academic community, is crucial.
 

Sensitivity: Salmonella
U.S. Test: February 2005

 Embracing challenges associated with drug resistant pathogens,  water conservation initiatives, environmental contamination,  agricultural and public health impact.
Antibiotic use and resistance in food animals is as a breeding ground for resistance genes and operons, for the accumulation of these genes on integrons and their movement to plasmids and other accessory elements. That is, animal use could in principle be a selective force responsible for the assembly of resistance gene clusters [like that postulated for the vancomycin-resistance operons in Enterococcus or the multiple-resistance island in Salmonella DT104] -- Antibiotics in agriculture: When is it time to close the barn door?," PNAS, April 30, 2002, vol. 99, no. 9, 5752-5754.

During the AAEP Convention 2004: Medicine II--Salmonella, the question was asked:  What type of impact can a salmonella outbreak at a veterinary hospital have and what can be done to prevent it?:

"Magdalena Dunowska, DVM, PhD, postdoctoral fellow in the veterinary teaching hospital at Colorado State University (CSU), discussed this issue at the 50th annual American Association of Equine Practitioners (AAEP) Convention in Denver, Colo., Dec. 4-8, 2004. She told the group that the James L. Voss Veterinary Teaching Hospital at CSU was hit with salmonella outbreaks in 1996 and 2001. The 1996 outbreak, she said, resulted in the hospital being closed for three months. The cost to the university for the closure was $500,000.

Yet the losses were greater because the $500,000 only covered expenses of clearing the hospital of the bacteria and does not include losses from clientele who were not allowed to bring horses to the facility."

Related discussions:
EQUINE ADVISORY: CORNELL

Animal Health Advisory: Multi Drug Resistant Strains of Salmonella in Horses, Cornell’s College of Veterinary Medicine, June 2004:

The NYS Veterinary Diagnostic Laboratory has isolated Salmonella Group C2 from cultures submitted from 7 horses of 4 different horse farms in either New Jersey or Pennsylvania, in one week. They have all shown the same profile, being resistant to most antibiotics. They awaiting further identification of these isolates. A Salmonella Newport strain (Group C2) was recently associated with the closing of the University of Pennsylvania’s large animal clinic, New Bolton Center, and was also reported to be multi-drug resistant.

Salmonellosis is generally a disorder of the gastrointestinal tract. Stress such as surgery, transportation, hospitalization, training, antibiotic therapy, or dietary changes
can lead to its development in the presence of infection. Symptoms are caused by toxins produced by the Salmonella species bacteria. Signs exhibited relate to four distinct types:

1) active carrier that appears normal
2) depression, fever, loss of appetite
3) severe case of enteritis and colitis that exhibits diarrhea and/or colic
4) generalized septicemia that can lead to rapid death or later bone and joint infections. Transmission to other horses is by the oral route, entry through umbilical stump in foals less than 30 days of age, or an open wound.

It is unknown how and when multi-drug resistant Group C2 Salmonella strains have emerged in the equine industry, or how widespread they are. It is believed that extensive non-therapeutic use of antibiotics exposes too many pathogens to levels of antibiotic which then causes “hardy” strains to survive. At this point, the cultures received at the lab have all been from sick foals or from the environment in which sick animals with confirmed Salmonella cultures were housed. It is advised that equine operations be alert to the possible spread of these organisms. Illness can be difficult to treat, may be fatal, and the environment, once contaminated, may be difficult to clean up. Other livestock and companion animal species are also susceptible to infection. Horse owners and caretakers should be alert to equine illnesses involving fever, diarrhea and colic, especially in foals, and call their veterinarian promptly. Fecal or blood culture (sick foals, especially) samples from all horses with such symptoms should be promptly submitted to the New York State Veterinary Diagnostic Laboratory at Cornell University for identification.

Since no commercially available vaccine exists against Salmonella, disinfection and other biosecurity practices must be utilized in order to prevent the introduction or the spread of this disease. Specific management practices to be used are outlined in the New York State Horse Health Assurance Program, a program designed to promote horse health, care and welfare and to encourage horse owners to learn more about horse management.

New arrivals and horses returning from off the farm should be isolated from other horses so that fecal-oral spread of these organisms can be controlled. If strict isolation is not possible, maintain closed groups with as small a number of animals per group as possible. Since foals seem to be most susceptible, avoid combining mare/foal pairs with new arrivals. Shared pastures, paddocks and stalls can all promote transmission of these organisms as they survive in manure, manure contaminated soils and forages, and wet areas. Horse trailers should be thoroughly cleaned, disinfected and re-bedded prior to transport of different animals. Always provide clean, individual food and water buckets and tubs for your horses then they are away from home. Avoid contact with manure when visiting equine facilities, and footwear that can be cleaned and disinfected. Do not wear the same clothing and shoes while visiting other horse facilities that you wear when caring for animals at your home facility.

Environmental cleanup involves the removal of all organic material (bedding, contaminated feed, manure), complete washing down of all surfaces, including feed tubs, water buckets/tanks, and cleaning utensils with water and a detergent cleaner to remove remaining organic residues, and the application of an appropriate disinfectant for the proper contact time. Disinfectants used to combat Salmonella include chlorine bleach and quaternary ammonium compounds. Scrapers, brooms, shovels and manure forks can spread the organism from contaminated areas to previously uncontaminated ones. Cleaned areas should be encouraged to dry quickly by using fans and exposing to sunlight, where possible. Pressure washers should be avoided, unless all animals have been removed and the operator wears OSHA-approved respirator protection, as Salmonella organisms can be aerosolized and spread this way. Environmental sampling can be used to determine if effective cleaning has been done in a facility with previously infected animals.

 
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