Mastering Minor Care: Dog Bites
/In the United States, approximately 4.5 million people are bitten by dogs annually [1]. Although not every person seeks health care for these injuries, the majority of those that do end up in the emergency department. In 2008, this led to greater than 316,000 emergency department (ED) visits and about 9,500 hospitalizations [1]. There are multiple factors to consider when managing dog and mammalian bites in the ED, including closure, prophylactic antibiotic administration, and rabies post-exposure prophylaxis. Let’s take a deeper dive into the evidence.
To close or not to close?
One of the major questions when faced with a patient who has any mammalian bite in the ED is “am I going to repair that?” While the evidence is extremely limited, there are some consistent themes to help guide your management. Wounds on the face and head - due to significant improvement in cosmesis - should be primarily closed [2,3]. Also in the literature, there is often discussion of whether or not primary closure affects risk of infection. The consensus from several studies including a meta-analysis revealed that there was no increased risk from primary closures [3,4,5], even if antibiotics were not given.
However, IDSA guidelines still only recommend primary closure on the face [2]. Additionally, there seems to be significantly increased risk of infection with wounds presenting to the ED more than eight hours after injury, so caution should be used if evaluating these wounds for repair [3]. With gaping wounds that are not on the face, and particularly on the hand with highest likelihood of infection, primary closure can be determined by a shared decision-making conversation with the patient.
Bottom line: Dog bite wounds should always be primarily closed on the face for cosmetic purposes, but caution and shared decision making should be used on all other wounds, particularly those presenting greater than 8 hours from injury, due to uncertain increased risk of infection.
I heard dog mouths are dirty. I should put them on antibiotics, right?
Table 1: antibiotic regimens
“Am I going to give antibiotics?” should be the next question answered in any visit for a dog bite. While Amoxicillin-Clavulanate is the first-line antibiotic for 3-5 days after injury, alternate regimens are available for broader coverage (Table 1) [2]. This is due to studies showing mixed aerobes and anaerobes in isolates of wounds from dog bites [6]. But before you sign that prescription, some ED physicians question if antibiotics should be prescribed at all. There is no strong consensus as to whether dog bite lacerations lead to an increased risk of infection compared to other wounds [7]. One meta-analysis reported a rate of infections after dog bites of 3-46% [8] versus 2-5% in simple laceration repairs in the ED [9,10]. However, there have been no studies statistically powered well enough regarding dog bite lacerations to confirm or dispute this claim.
Table 2. Considerations for antibiotics.
The meta-analysis most frequently cited showing benefit for prophylactic antibiotics in dog bite wounds was performed in 1993 [8]. Although there was large study heterogeneity, it found a statistically significant relative risk for infection of 0.56 with a number needed to treat of 14 patients. More recently, a Cochrane review which consisted almost entirely of the same studies as the original Cummings meta-analysis, found no significant difference in rate of infections with prophylactic antibiotic use [11]. Finally, a randomized-control trial found that prophylactic antibiotics for dog bite wounds did not statistically change infection outcomes and was not cost-effective, recommending that prophylactic antibiotics only be used in high-risk wounds [12]. One study characterized puncture wounds and those with primary closure as the wounds at most increased risk for infection [13], while additional studies have indicated wounds on the hand [9] and wounds seen >8 hours after injury [3] as having the highest risk of infection. Table 2 has been included to summarize these results, most consistent with the current IDSA guidelines [2].
Bottom line: Antibiotics have not been shown to be significantly beneficial in most studies, and consideration to a patient's co-morbidities may be more helpful in judicious use of antibiotics rather than prophylactically prescribing to all.
What about rabies?
The final consideration is “do I have to give them rabies prophylaxis?” In the United States, carnivorous wild animals and bats are the most common source of transmission to humans. In 2006, only 79 dogs were found to have rabies in the United States [14]. If a patient sustains a domestic dog bite, that dog (if able) should be observed for 10 days even if the bite was provoked and the animal is vaccinated. If that animal develops any illness consistent with rabies, the patient should receive rabies post-exposure prophylaxis. If there is high suspicion that the animal is rabid, such as an ill animal with an unprovoked bite, then post-exposure prophylaxis should be given immediately. If the animal cannot be observed, this can be discussed with the patient and the public health department on the risks and benefits of immediate versus delayed treatment [14].
Post-exposure rabies prophylaxis involves both the Human Rabies Immune Globulin (HRIG, HyperRab) and the rabies vaccine (Rabavert). HRIG should not be given if the patient has previously received the rabies vaccines. HRIG should be administered at a 20 IU/kg dose intramuscularly. If possible, this should be administered into and around the wound(s) with the remainder given distant to the vaccine [15]. The first 1.0mL of the rabies vaccine, either the human diploid cell vaccine or the purified chick embryo cell vaccine, should be administered in the deltoid (patients >/= 2 years old) on the first day of presentation and additionally given on days 3, 7, and 14 for a total of four doses [15]. A 5th dose on day 28 should be given for immunocompromised people.
In patients younger than 2, this should be given in the anterolateral thigh. The gluteus should never be used because observations suggest administration in this area results in lower neutralizing antibody titers. If HRIG was not administered when vaccination was begun, it can be administered up to 7 days after the administration of the first dose of vaccine. Beyond the 7th day, HRIG is not recommended since an antibody response to the vaccine is presumed to have occurred. Patients should ideally avoid corticosteroids, antimalarials, and other immunosuppressants during post-exposure therapy as this can inhibit the immune response. The vaccine is safe in pregnancy and breastfeeding.
Bottom line: Rabies post-exposure prophylaxis should be discussed with a patient if a dog bite is unprovoked and animal is ill OR if the dog cannot be observed for at least 10 days.
Final thoughts
In addition to the important topics above, there are some tasks that should always be completed prior to dispositioning patients with dog bites.
All patients should receive a tetanus vaccine if they do not have an updated one in the last 10 years.
Wounds should receive high pressure irrigation, foreign body removal, and cautious debridement to limit the risk of infection [2], even if primary closure is not indicated.
If the bite is on any of the extremities - particularly the hand- range of motion must be performed of the affected limb to evaluate for tendon injury (see post on MMC: Hand Injuries).
Finally, all patients should be instructed to follow up with their primary care physician within one week for a wound recheck to ensure adequate healing.
Post by Melanie yates, MD
Dr. Yates is a PGY-3 in Emergency Medicine at the University of Cincinnati
Editing by Bronwyn finney, MD and Alexa sabedra, MD
Dr. Finney is a PGY-3 in Emergency Medicine at the University of Cincinnati and Resident Editor of Mastering Minor Care Series
Dr. Sabedra is an Assistant Professor in the Department of Emergency Medicine at the University of Cincinnati
References
Holmquist L, Elixhauser A. Emergency department visits and inpatient stays involving dog bites, 2008: Statistical brief #101. Healthcare cost and utilization project (HCUP) statistical briefs. 2010. 1-14.
Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clinical Infectious Diseases. 2014;59(2):147-159.
Paschos NK, Makris EA, Gantsos A, Georgoulis AD. Primary closure versus non-closure of dog bite wounds. A randomised controlled trial. Injury. 2014;45(1):237-240.
Chen E, Horing S, Shepherd SM, Hollander JE. Primary closure of mammalian bites. Academic Emergency Medicine. 2000;7(2):157-161.
Cheng H-T, Hsu Y-C, Wu C-I. Does primary closure for dog bite wounds increase the incidence of wound infection? A meta-analysis of randomized controlled trials. Journal of Plastic, Reconstructive and Aesthetic Surgery. 2014;67(10):1448-1450.
Goldstein EJ, Citron DM, Wield B, et al. Bacteriology of human and animal bite wounds. Journal of Clinical Microbiology. 1978;8(6):667-672.
Gottlieb M, Peksa GD. Prophylactic antibiotics are not routinely indicated for dog bites. Annals of Emergency Medicine. 2020;76(1):86-87.
Cummings P. Antibiotics to prevent infection in pateints with dog bite wounds: A meta-analysis of randomized trials. Annals of Emergency Medicine. 1994;23(3):535-540.
Hollander JE, Singer AJ, Valentine S, Henry MC. Wound registry: Development and validation. Annals of Emergency Medicine. 1995;25(5):675-684.
Perelman VS, Francis GJ, Rutledge T, Foote J, Martino F, Dranitsaris G. Sterile versus nonsterile gloves for repair of uncomplicated lacerations in the emergency department. Annals of Emergency Medicine. 2004;43(3):362-370.
Medeiros IM, Saconato H. Antibiotic prophylaxis for mammalian bites. Cochrane Database of Systematic Reviews. 2001.
Quinn J, McDermott D, Kramer N, Stein J. Prophylactic antibiotics for dog bites: An RCT with refined cost model. Academic Emergency Medicine. 2007;14(5).
Tabaka ME, Quinn JV, Kohn MA, Polevoi SK. Predictors of infection from dog bite wounds: Which patients may benefit from prophylactic antibiotics? Emergency Medicine Journal. 2015;32(11):860-863. doi:10.1136/emermed-2014-204378
Manning SE, Rupprecht CE, Fishbein D, et al. Human Rabies Prevention - United States, 2008: Recommendations of the Advisory Committee on Immunization Practices. MMWR Recommendations and Reports. 2008;57(03):1-26.
Rupprecht CE, Briggs D, Brown CM, et al. Use of a Reduce (4-Dose) Vaccine Schedule for Postexposure Prophylaxis to Prevent Human Rabies: Recommendations of the Advisory Committee on Immunization Practices. Morbidity and Mortality Weekly Report. 2010;59(02):1-9.
Baddour LM, Harper M. Animal bites (dogs, cats, and other animals): Evaluation and management. UpToDate. Published June 24, 2022. Accessed March 13, 2023.
