June 24, 2009
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Few data on MRSA colonization rates in non-clinically affected animals are available. Although identification of colonized or infected animals is important in the prevention of the spread of MRSA, the routine screening of all animals is not yet practical, so there remains the possibility that a small percentage of colonized animals will remain undetected upon first admission to a veterinary clinic or hospital.13
When any animal presents with clinical signs indicating possible MRSA indications, such as non-healing wounds or infections that do not respond to antibiotic therapy, it should be considered for MRSA screening.13 Animals identified as, or suspected to be, positive should be admitted directly into a separate examination room to prevent contact with other animals. The examination room must then be cleaned and disinfected prior to admitting another patient to the room. Upon entry into a veterinary hospital, a known or suspected MRSA-infected animal should be isolated and barrier precautions should be implemented when handling or treating the animal.13In a 2005 survey conducted by Hanselman et al of veterinary personnel attending the annual American College of Veterinary Internal Medicine Forum, nasal swabs were obtained from 417 attendee volunteers from 19 countries. CMRSA-5 (ST8-MRSA-IV, similar to USA500) was isolated from 13 (48%) of 27 colonized persons, all of whom were in large-animal practice. CMRSA-2 (ST5-MRSA-II, similar to USA100) was isolated from 13 (48%) of 27 colonized persons: 11 in small animal practice and 2 in large animal practice. One other isolate, possibly related to CMRSA-2. was found in a US veterinarian in small animal practice. Overall, CMRSA-5 was more commonly isolated from persons in large animal practice than persons in small animal practice.12In large animal practices, veterinary personnel routinely wear coveralls and boots as protective clothing. However, MRSA colonization and transmission usually occurs through contact from the hands of the human to the anterior nares (nostrils) of the animal, so masks and gloves should be considered as additional protective measures.22 Anderson et al reported a significant protective effect of hand hygiene in equine veterinarians. Multivariable analysis showed an increased risk of MRSA colonization associated with having been diagnosed with or having treated a patient diagnosed with MRSA colonization or infection in the last year P = 0.015, P = 0.039, respectively), whereas hand washing between infectious cases (P = 0.009) and hand washing between farms (P = 0.047) were protective. The prevalence of MRSA colonization among equine veterinary personnel found in this study was high compared to that of other studies of the general population. These data support previous suggestions that equine veterinary personnel are at increased risk of colonization with MRSA, and provided a statistically significant association between hand hygiene practices and a measurable clinical outcome in veterinary medicine60In a Netherlands study by Wulf et al, 80 veterinary students and 99 veterinarians attending a livestock conference were screened for MRSA. None of the subjects displayed symptoms of MRSA infection. Seven (3.9%) of 179 tested were positive for MRSA. Subjects who reported livestock contact had a 4.6% prevalence of MRSA, whereas none of the students who reported no contact with livestock tested positive for MRSA. The overall prevalence of MRSA colonization in veterinary doctors and students in large animal practice was 160 times the rate of MRSA prevalence in hospitalized human patients; which indicates that animal handlers, including veterinary personnel, farmers (a MRSA-colonized son of a swine farmer transmitted the pathogen to a hospital nurse), and their families should be screened upon checking into a hospital.22In order to stop the cycle of transmission and re-transmission between humans and their companion animals, efforts are needed to decontaminate their shared surroundings.13 Factors involved in MRSA transmission among humans include crowding, compromised skin surfaces (open wounds, scrapes, etc.), contaminated items or surfaces, and poor hygiene.4 This is an area of concern that needs to be addressed in both the human and the veterinary medical fields.49In veterinary hospitals, the use of a chlorhexidine surgical scrub has proven effective in eradicating transmission of S. aureus. Surgical scrubs containing both chlorhexidine and alcohol have been more effective against multiple strains of MRSA.61 In a Japanese study, seven disinfectants for hand scrubs and soaks were evaluated against multiple MRSA strains: glutaraldehyde, povidone iodine, and ethanol proved effective. Sodium hypochlorite, benzalkonium chloride, and alkyldiaminoethylglycine hydrochloride were not effective against all strains using the prescribed concentration conditions and exposure time.62In 2005 the American Veterinary Medical Association (AVMA), in partnership with the CDC, conducted an anonymous survey via a questionnaire sent to veterinarians randomly selected from the AVMA membership. The survey group was comprised of US veterinarians in small animal, large animal, and equine clinical practice, and was conducted to assess both precaution awareness (PA), which involves both proactive protective behaviors and the use of personal protective equipment; and the veterinarians' perceptions of zoonotic disease risks. Results indicated that, in general, the respondents did not engage in protective behaviors or use personal protective equipment considered sufficient to protect against zoonotic disease transmission. Small animal and equine veterinarians employed in practices that had no written infection control policy were significantly more likely to have low PA scores. Male gender was associated with low PA score among small animal and large animal veterinarians, and equine practitioners in clinical practice were more likely to have lower PA ranking than equine practitioners working in teaching or referral hospitals.63 This study emphasizes a need for increased awareness and precautions within the veterinary medical profession.Veterinarians should be aware of the concerns regarding MRSA and should develop an understanding of appropriate disease surveillance, diagnostic testing, and infection control in order to lessen the impact of MRSA on both animals and their caretakers.2,12,20,30 Veterinarians not only need to practice proper hygiene and prevention of transmission of zoonotic disease in their work environments, they also have a duty to educate the owners/handlers of MRSA-colonized or -infected animals on the risks and proper hygiene prevention when dealing with these animals.Precautionary measures include the following:
With the rise of MRSA as a zoonotic disease in both human-to-animal and animal-to-human transmission, both human healthcare and veterinary care providers are advised to review the infection control guidelines for the prevention and control of MRSA infections in both animals and humans at the AVMA's Infection control practices and zoonotic disease risks among veterinarians in the United States and the CDC's Overview of Healthcare-associated MRSA.It is incumbent upon the veterinary and human medical professions to improve communication regarding the roles of both animals and humans in MRSA transmission. The pressing need for judicious antimicrobial use and a good general infection control program in human and veterinary healthcare cannot be overstated. The judicious use of antimicrobials in animals and humans is essential in order to prevent the spread of MRSA strains that are increasingly resistant to known antimicrobials.