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Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The above image shows a 3-day-old dog bite.

Animal bites are a common presenting problem[1] in emergency departments (EDs) and clinics across the world. In the United States, approximately 3-6 million animal bites occur per year; most of these (80-90%) are dog bites, with cat bites a distant second.[2]

Animal bite wounds are at high risk for infection, given the bacterial flora present on the skin and in the oral cavities of the offending animals.[2,3] In addition, other complications (eg, rabies or tetanus) are important considerations in the management of animal bites.[1,2-4]

Although accurate data are lacking, human bites, often a component of violent assault, may be the third most common type of mammalian bite.[5]

Image from Miranda-Rius J, Brunet-Llobet L, Lahor-Soler E, Mendieta C. J Med Case Rep. 2014;8:298. [Open access.] PMID: 25196423, PMCID: PMC4164117.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The above image depicts a 12-day-old human bite wound mimicking a chronic ulcerative process.

All bite wounds should be heavily pressure-irrigated with saline solutions and carefully inspected for foreign material, which may include debris or even teeth.[2,3,6,7]

Although stitching some bite wounds can increase the risk of infection, they should be closed if in a cosmetically important location.[8] Loose approximation is no longer recommended.[9]

Antibiotic prophylaxis should focus on common culprit organisms, including skin flora such as Staphylococcus, Streptococcus, and Pasteurella, in dog and cat bites, and Eikenella, in human bites.[10] A common antibiotic regimen is amoxicillin-clavulanate for 5 days; clinicians should recommend a wound check in 48-72 hours.[11]

Images from Miranda-Rius J, Brunet-Llobet L, Lahor-Soler E, Mendieta C. J Med Case Rep. 2014;8:298. [Open access.] PMID: 25196423, PMCID: PMC4164117.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The images here were obtained in the same patient shown in the previous slide. He underwent surgical débridement and (bottom left and right) eventually had complete and satisfactory healing after antibiotic administration and suturing.

Image from Daniali L, Payne E, Trovato MJ. Eplasty. 2013;13:ic43. [Open access.] PMID: 23638241, PMCID: PMC3640212.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The image shows an isolated 2.6-cm full-thickness helical rim defect in a young male after a human bite to the right auricle.

In the case of human bites, potential infection with hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV) must be considered.[6,12,13]

Images from Stoner-Duncan B, Streicker DG, Tedeschi CM. PLoS Negl Trop Dis. 2014;8(6):e2867. [Open access.] PMID: 24945360, PMCID: PMC4063729.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The images in the slide show a young girl who was bitten on the head by a bat while she slept (top left and right); another example of a bat bite in a mammal (bottom left); and the common vampire bat, Desmodus rotundus(bottom right).

Tetanus and rabies prophylaxis is important with mammalian bite wounds.[4,6,7,12] Any patient with a penetrating wound must be considered at risk for tetanus, and efforts should be made to determine that individual's tetanus immunization status.[10] The incidence of rabies varies within the mammalian population in a given geographic area.[14] More than 90% of rabies exposure is caused by wildlife (eg, bats).[15]

Images from Madani G, Nekaris KA. J Venom Anim Toxins Incl Trop Dis. 2014;20(1):43. [Open access.] PMID: 25309586, PMCID: PMC4192448.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The image on the left shows a wild subadult Asian slow loris, Nycticebus kayan, a venomous mammal; note the saliva protruding from its mouth. The photographer was bitten by this animal. The image on the right shows the bite marks on the middle phalanx of the middle finger on the photographer's right hand 12 days after the bite. The photographer suffered anaphylactic shock following the bite; was hospitalized and treated with an intramuscular epinephrine injection, IV hydrocortisone, and IV fluids; and was discharged within 2 days with oral medications, including a steroid, an antihistamine, and an antibiotic.

Images from Marsden NJ, Kyle A, Jessop ZM, Whitaker IS, Laing H. Front Surg. [Open access.] 2015;2:6. PMID: 25759812, PMCID: PMC4338602.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

Dog Bites

As previously stated, dog bite is the most common type of animal bite in the United States (80-90%);[2,3,16] it accounts for an annual 1-2% of all ED visits for injuries.[3,4] Children are the most common victims.

The upper images are of an 18-month-old boy who suffered a traumatic total amputation of the nose after a dog bite, with only a small part of the nasal dorsum, septum, and right ala spared. The lower images are of the same boy at 10-year follow-up after successful microsurgical nasal replantation.

Common bacteria associated with dog bites include Staphylococcus and Streptococcus species, as well as Bacteroides, Fusobacterium, Pasteurella, and Prevotella organisms.[6]

Images from Alasil T, Eljammal S, Scartozzi R, Eliott D. Cases J. 2008;1(1):218. [Open access.] PMID: 18840259, PMCID: PMC2569032.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The above figure shows magnetic resonance imaging (MRI) scans of the pelvis from a 39-year-old man who presented with bacteremia-induced acute vision loss 6 weeks after sustaining a lower-extremity dog bite. In addition to being diagnosed with a rhegmatogenous retinal detachment, the patient had oxacillin-resistant Staphylococcus aureus bacteremia with multiple septic emboli to various organs and demonstrated bilateral loculated pleural effusion, left renal abscess, left obturator abscess, and right-eye endogenous endophthalmitis. The left MRI scan reveals extensive irregular collection (abscesses) along the left obturator internus muscle, with infiltration to the surrounding left hip structures (arrow). The right scan shows left hip joint effusion that suggests a septic joint (arrow).

Images from Nocera NF, Desai KK, Granick MS. Eplasty. 2014;14:ic25. [Open access.] PMID: 25210576, PMCID: PMC4131574.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

Cat Bites

The images show cellulitis of the left hand (left, center) and streaking of the left forearm (right) in a middle-aged man 1 week after a cat bite on the dorsum of the left hand. The swelling and erythema of the dorsal and volar-radial aspects of the hand affected the range of motion of the wrist and thumb.

Household cat bites are thought to make up an estimated 5-20% of all animal bites in the United States.[2,3,6,16] Feline bites are more prone to infection than dog bites[3,12] because cats' sharp, needlelike teeth cause puncture wounds that allow inoculation of bacteria into deep tissue beds.[2,3,6] Common bacteria involved in cat bites are similar to those found in dog bites.

Images from Sbai MA, Dabloun S, Benzarti S, Khechimi M, Jenzeri A, Maalla R. Pan Afr Med J. 2015;21:206. [Open access.] PMID: 26421101, PMCID: PMC4575703.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The above images were obtained in a middle-aged woman who had right acute carpal tunnel syndrome associated with compartment syndrome 6 days after sustaining a cat bite on her right thumb. Microbiology identified Pasteurella multocida as the causative organism. Significant edema of the right hand was apparent (top and bottom left), with contracture of the fingers being associated with paresthesia in the region of the median nerve. After incision of the carpal tunnel (top right), the median nerve presented signs of vascular suffering. Fasciotomy of the four muscular compartments of the hand was performed (bottom right).

Images from Ibraheem WA, Ibraheem AB, Ibraheem AK. Pan Afr Med J. 2014;17:311. [Open access.] PMID: 25328607, PMCID: PMC4198319.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

Rodent, Bat, and Raccoon Bites

Much less frequently than, collectively, dogs, cats, and humans, other animals may inflict bites (<2% of total animal bites[6]). The above images depict facial and left eye injuries in a 13-day-old infant who sustained rat bites. Injuries to the left upper and lower eyelids, tip of the nose, and left cheek are visible (left). At 2 weeks after the injury, left microbial keratitis can be seen that is deeply stained with 2% fluorescein dye (center). Residual left cornea opacity and deformed left eyelids are apparent (right). Rabies incidence is typically higher in bats, raccoons, and rodents than in dogs and cats, depending on the geographic area.[12,14]

Still images from a video of an alligator bite in progress, with permission from and courtesy of Brave Wilderness.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

Reptile Bites

Bite wounds from reptiles are relatively uncommon; however, in areas where large reptiles come in contact with human populations, significant injuries and even death may occur.

Lizards

The Gila monster and the Mexican beaded lizard are two well-known venomous lizards. Bites from a Gila monster can cause severe pain, edema, and paresthesia at the bite site, as well as systemic symptoms such as hypotension and airway swelling.[17]

Crocodilians

Crocodilians such as the American alligator (Alligator mississippiensis), the American crocodile (Crocodylus acutus), and the Nile crocodile (Crocodylus niloticus) have powerful jaws and large teeth that can cause substantial, life-threatening wounds.[18]

Image from Rao CP, Shivappa P, Mothi VR. J Occup Med Toxicol. 2013;8(1):7. [Open access.] PMID: 23522302, PMCID: PMC3614463.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

Snakes

The above image shows a complete snake bite mark to the right thenar eminence.

In the United States, two types of venomous snakes whose bites may be life-threatening are the pit vipers (eg, rattlesnakes, fer de lances, copperheads, and water moccasins) and the coral snakes.[19] Pit viper venom can include neurotoxins or systemic hemostasis toxins that interfere with blood clotting and cause consumptive coagulopathy and hemorrhage. Coral snake venom includes a neurotoxin that can cause respiratory failure within a few hours of the envenomation.

Corticosteroids, application of ice, nonsteroidal anti-inflammatory drugs, prophylactic fasciotomy, and routine use of blood products have not been shown to improve outcomes in snake wound management.

Images from Hui Wen F, Monteiro WM, Moura da Silva AM, et al. PLoS Negl Trop Dis. 2015;9(5):e0003701. [Open access.] PMID: 25996940, PMCID: PMC4440781.

Animal Bites: What You Need to Know

Joseph U Becker, MD | May 10, 2021 | Contributor Information

The above images illustrate local complications in three patients secondary to Bothrops snake bites. In the first patient (A), swelling and serohemorrhagic blisters on the left hand and forearm, as well as incoagulable blood, were apparent 12 hours after the bite. In the second patient (B), who presented with compartment syndrome 24 hours after sustaining the bite, fasciotomy of the left hand was performed. It should be noted that fasciotomy is usually contraindicated in snake bites. In the third patient (C and D), extensive edema and necrosis in the left hand and gangrene of the fourth finger were visible 24 hours after the bite (C); amputation was performed on the fourth finger (D).

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