Dog bites

Dog bites are skin lesions, avulsion injuries, hemorrhage, and secondary infections caused by canine teeth bites. In addition to suppurative infections, rabies, tetanus, and gas gangrene may occur.


Causes

Dog bite wounds can be on all areas of the body, mostly on the extremities, especially upper extremities and hands in adults, 54% - 85% of bites are on the extremities, and 15% - 27% of bites are on the head and neck. The bite sites are predominantly on the head, face, and neck in children, and about 2/3 are on the head, face, and neck in children aged under 4 years.

Due to strong bite and tear forces from dogs, severe soft tissue injuries may occur, and puncture wounds may be complicated by nerves, blood vessels, tendons, ligaments, and even bone injuries.


Signs and Symptoms

Dog bites can result in various wounds, such as scratches, punctures, and lacerations. Bites from large dogs can produce powerful tear forces that can lead to serious injuries. Fatal injuries are usually on the head and neck or direct penetrating injuries to vital organs in young children. When old children or adults are bitten by dogs, the extremities, especially the dominant hand, are most vulnerable.

Video 1 wounds caused by dog bites

Clinical manifestations of wound infections include fever, redness, swelling, tenderness, purulent discharge, and lymphangitis, and complications include subcutaneous abscesses, interdigital infection, osteomyelitis, septic arthritis, and bacteremia. Localized cellulitis may occur 24 - 72 hours after being bitten. Systemic infection occurs in less than 20% of patients. Bones, joints, blood, and meninges may be involved. Delayed treatment of dog bites is one of the important factors contributing to the high incidence of infection. If patients are not treated more than 24 hours after being bitten, infection may occur.

Ultrasonography can help identify abscess formation and locate foreign bodies in the infected wounds. Plain radiographs and computed tomography (CT) scans are necessary for deep bite wounds near the joints, and bone or joint destruction and foreign bodies such as embedded teeth can be detected. For obviously infected wounds, imaging studies are needed to determine bone and soft tissue damage and osteomyelitis-related changes. Dog bites on the head occasionally penetrate the skull, leading to depressed skull fractures, local infection, and brain abscesses. Therefore, CT and magnetic resonance imaging (MRI) are required for patients with deep scalp bites, including stab wounds, especially in children under 2 years of age. CT scans show skull fracture, punctured skull external lamina, and intracranial pneumatosis, indicating the presence of penetrating injuries.


Diagnosis

On the basis of chief complaints and clinical presentations, the condition can be definitively diagnosed.


Treatment

All bites should be rinsed with soapy water, other weak alkaline detergents, and running water alternately for about 15 minutes, and the residual liquids on the wounds should be removed with sterile gauze or absorbent cotton. If there is severe pain during cleaning, local anesthesia can be administered.

After thorough rinsing, the inside of the wounds can be cleaned with diluted iodophor or other medical preparations with virus inactivation ability, inactivating the rabies virus remaining in the wounds.

In dog bite wounds, especially lacerations, debridement should be performed to remove necrotic tissues.

Scratches and simple puncture wounds do not require primary closure. Simple laceration wounds can require primary closure. For facial lacerations, primary closure can also be applied. Appropriate wound management is extremely important for the prognosis of patients undergoing wound closure and the reduction of infection risks. Adequate irrigation and debridement are necessary, and deep closure should be avoided as far as possible.

If wounds are more than 6 hours after being bitten, or patients are susceptible to infections, primary closure is not recommended as these wounds are with a high risk of infection. In early treatment, wound cleaning, debridement, open drainage, and regular dressing changes are appropriate. Delayed closure can be performed in 72 hours after being bitten according to the wound conditions.


Post-exposure prophylaxis

Rabies vaccine should be injected immediately, and there are 5 doses regimen and 2-1-1 regimen.

5 doses regimen is 1 dose intramuscularly on the 0th, 3rd, 7th, 14th, and 28th day, while 2-1-1 regimen is 2 doses intramuscularly on the 0th day and 1 dose intramuscularly on the 7th and 21st day.

Human rabies immunoglobulin 20U/kg and anti-rabies serum 40U/kg should be injected locally around the wounds.

Tetanus vaccine and tetanus antitoxin can be considered.

Psychological intervention may be required, because post-traumatic stress disorder occurs in 50% of patients, and hydrophobophobia may occur.