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  News from the Maryland Veterinary Medical Association                                                   Summer 2012

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Salmonella: A Local and National Concern
by Celeste Clements, DVM, DACVIM

Salmonella is a Gram-negative, facultative anaerobic, enteric bacteria that may inhabit the intestines of most animals, including mammals, birds, reptiles and amphibians, producing diarrhea, or, less commonly, septicemia. Most animals are infected with Salmonella enterica subs. enterica, that differ only by strain or serotype, as defined by somatic and flagellar antigens, and number more than 2400.

To simplify the nomenclature a given isolate or infection is usually designated by the genus name and serotype. Amongst the most common are Salmonella Enteriditis, S. Typhimurium, and S.Typhi, which is the cause of typhoid fever. While S. Typhi, is limited to man and some primates, many strains have diverse host ranges, providing opportunity for zoonoses. In the state of Maryland mammalian Salmonella is usually reportable, and the state veterinarian should be notified within 48 hours of discovery, by phoning 410-841-5810 during business hours, or 410-841-5971 after hours. Details are provided on the State of Maryland’s website:

In May 2012 the zoonotic potential of Salmonella made national headlines when contaminated pet foods manufactured by Diamond Pet Foods in South Carolina were identified as the source of a multistate outbreak of Salmonella Infantis; at least 15 people were infected by handling dry dog food or by associating with infected dogs, although none from Maryland. FDA inspection of the company’s plants revealed irregularities with the equipment and manufacturing procedures that indicated that “all reasonable precautions” against bacterial contamination of the food products were not being taken. The results of civil law suits against the company are still pending.

These reports came in the wake of an earlier investigation into numerous cases of salmonellosis associated with reptiles and amphibians and/or exposure to feeder rodents infected with a strain of Salmonella also responsible for outbreaks in 2009 in the US and 2010 in the United Kingdom. Authorities at the Centers for Disease Control and Prevention (CDC) expressed concerns that the bacteria might be endemic in this population of feeder rats. Based on the high percentage of cases in children under five years of age they recommended that young children avoid exposure to reptiles or amphibians, including in the home. Owners of reptiles, amphibians, or other animals that are fed rodents should be aware of the risk for salmonellosis from the animals and from live and frozen feeder rodents. Safe handling instructions for all of these animals should be provided at the point of sale. 

Veterinarians may be the first point of contact for a pet owner with a food borne illness in the home. A sick pet owner should always be directed to his or her physician, and the pet’s health assessed, as needed. The most common presentation of salmonellosis in dogs is diarrhea. Vomiting, lethargy and lack of appetite may also be present. Diarrhea can range from mild to severe and bloody. Chronic diarrhea can also develop but is less common. Bacteremia can occur, with or without diarrhea, but this is uncommon..

Only clinically ill dogs and cats should be tested for Salmonella with stool cultures or PCR according to the faculty of the Ontario Veterinary College’s Centre for Public Health and Zoonoses; and no treatment of asymptomatic carriers is advised, since this may even increase the duration of bacterial shedding or promote bacterial resistance. This group’s website provides valuables resources for veterinarians and pet owners alike, including printable documents that may be carried to a physician.

Risks of human infection can be limited by good hand hygiene practices in the home, emphasizing frequent hand washing with soap and running water, or with an alcohol based hand sanitizer, especially after visiting the restroom or handling pets or their foods; and consistent clean up of animal wastes; in addition to feeding pets well cooked, not raw, diets and treats. If a problem with pet food is suspected the FDA has several reporting options, either by phone or electronic portal. 

Salmonella carriage in horses and other hoofed stock should be anticipated by hobbyists and producers, alike, but it is usually temporary. As is the case with small animals illness associated with the enteric bacteria is not common, but is more often seen in patients if they are being treated with antibiotics, held off feed, undergoing general anesthesia, having feed changes, or being shipped. They are more likely to get sick with lower doses of the bacteria or with less virulent strains under these conditions. Good farm management practices are needed to minimize contagion and the risk of outbreaks, and the basics are offered here:[1].pdf

Maryland’s monthly One Health Bulletin lists several more ongoing multistate investigations of human cases of salmonellosis derived from live poultry and small turtles, including seven in Maryland. The Maryland Department of Public Health and Hygiene posts several facts about salmonellosis on its public website, citing such common sources of the bacteria as raw chicken, turkey, beef, pork, other meat, eggs, and unpasteurized milk products which may be as important at live animal sources. The bacteria has such diverse sources that extreme vigilance is necessary for producers, consumers, and health care providers, alike.   

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