Introduction
About 4.5 million people in the US are bitten by dogs each year. Most of the people who seek medical care for these injuries end up in the emergency department (ED). In 2008, there were more than 316,000 ED visits and about 9,500 hospitalizations due to dog bites. There are many factors to consider when treating dog and other mammal bites in the ED, such as whether to close the wound, give antibiotics to prevent infection, and give rabies shots. Let's look at the evidence to learn more.
To close or not to close?
When a patient with a mammalian bite arrives in the emergency department (ED), one of the biggest questions is whether to stitch the wound closed. The evidence is limited, but there are some general principles that can help guide decision-making.
Face and head wounds: These wounds should typically be stitched closed to improve cosmetic appearance. Studies have shown that stitching these wounds does not increase the risk of infection, even if antibiotics are not given. However, the Infectious Diseases Society of America (IDSA) still only recommends stitching face wounds closed.
Other wounds: For wounds other than those on the face and head, it is important to be cautious, especially if the wound is more than eight hours old. This is because older wounds are more likely to be infected. If the wound is gaping and not on the face, the decision of whether to stitch it closed can be made on a case-by-case basis with the patient's input.
Bottom line: Dog bite wounds on the face should always be stitched closed for cosmetic purposes. However, caution and shared decision-making should be used for all other wounds, especially those presenting more than eight hours from injury, due to the uncertain increased risk of infection.
I heard dog mouths are dirty. Should I put them on antibiotics?
The next question to answer in any dog bite visit is whether to give antibiotics. Amoxicillin-Clavulanate is the first-choice antibiotic for 3-5 days after injury, but other antibiotics are available for broader coverage. This is because dog bite wounds often contain a mix of aerobic and anaerobic bacteria. However, some emergency department doctors question whether antibiotics should be given at all.
There is no clear consensus on whether dog bite wounds are more likely to get infected than other wounds. One study found that 3-46% of dog bite wounds get infected, compared to 2-5% of simple lacerations repaired in the emergency department. However, there have not been any large enough studies to confirm or disprove this claim.
The oldest and most cited meta-analysis study performed in 1993 on prophylactic antibiotics for dog bites found that they reduced infection risk by half. However, a Cochrane review in 2001 which consisted almost entirely of the same studies in the 1993 study found no significant difference in rate of infections with prophylactic antibiotic use. However, more recent studies have shown no benefit, and antibiotics may not be cost-effective.
Puncture wounds, hand wounds, and wounds seen more than 8 hours after injury are at highest risk of infection, so antibiotics should only be used in these cases.
Bottom line: Antibiotics have not been shown to be very helpful in most studies, so it is better to consider a patient's other medical conditions when deciding whether to prescribe them, instead of giving them to everyone prophylactically.
What about rabies?
The last thing to think about is whether or not to give the patient rabies shots. In the US, most cases of rabies in humans come from bites from wild carnivores and bats. In 2006, only 79 dogs in the US were found to have rabies. If a patient is bitten by a pet dog, the dog should be watched for 10 days, even if the bite was provoked and the dog is vaccinated. If the dog gets sick during that time, the patient should get rabies shots. If the dog is sick and bites someone without being provoked, the person should get rabies shots right away. If the dog cannot be watched, talk to the patient and the public health department about the risks and benefits of getting rabies shots right away versus waiting.
Rabies post-exposure prophylaxis (PEP) is a series of shots that are given after a person has been exposed to rabies. PEP involves two types of shots: human rabies immune globulin (HRIG) and rabies vaccine. HRIG is given if the patient has never been vaccinated against rabies before. It is given as a single shot into the muscle, usually within 7 days of exposure. The rabies vaccine is given as a series of four shots, usually on days 0, 3, 7, and 14. The first shot is given into the deltoid muscle, and the other shots are given into the arm or thigh. An extra shot may be given on day 28 for people with weakened immune systems.
For babies under 2 years old, the first rabies shot should be given in the front of the thigh. The shot should not be given in the buttock, as this may lead to a lower immune response. If HRIG is not given when the rabies vaccine is started, it can be given up to 7 days later. After 7 days, HRIG is not recommended because the body will have already started to produce antibodies to the vaccine. Patients should avoid taking corticosteroids, antimalarials, and other immunosuppressants during rabies post-exposure therapy, as these medications can weaken the immune response. The rabies vaccine is safe for pregnant and breastfeeding women.
Bottom line: If a dog bites someone without being provoked and is sick, or if the dog cannot be watched for at least 10 days, talk to the patient about rabies post-exposure prophylaxis (PEP).
References:
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.
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.
Medeiros IM, Saconato H. Antibiotic prophylaxis for mammalian bites. Cochrane Database of Systematic Reviews. 2001.
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
Baddour LM, Harper M. Animal bites (dogs, cats, and other animals): Evaluation and management. UpToDate. Published June 24, 2022. Accessed March 13, 2023.