Polymicrobial Wound Infection and Nerve Injury Secondary to a Nonhuman Primate Bite

Bite wounds inflicted by animalscan result in serious infectionscaused by zoonoticoropharyngeal flora.¹ Among theseare simian immunodeficiency virus,simian T-cell lymphotropic virus,simian foamy viruses, herpes Bvirus, and myriad bacteria. Nonhumanprimate bites occur with significantlyless frequency than dog andcat bites,^2,3 and when they do occur,the clinician has little guidance regardingworkup and management.We report a case of polymicrobialsimian bite wound infection with associated nerve injury in a child whowas petting and feeding a monkeywithout authorization while visitinga zoo.

Case report

While engaging in unauthorizedfeeding and petting of a caged white-handedgibbon (Hylobates lar), a 12-year-old boy was bitten on the rightforearm. First aid was provided atthe zoo, and he was referred to a localemergency department (ED) forfurther evaluation. After wound irrigation,sterile dressing, and verification that tetanus and hepatitis B immunizationswere current, prophylactictreatment with amoxicillin/clavulanic acid was prescribed andthe patient was discharged home.

Thirty-six hours after the injury,purulent drainage from the woundwas noted. Approximately 12 hourslater, progressive erythema, induration,and tenderness developed overthe involved forearm. There was noassociated fever or other constitutionalsymptoms. The child was reevaluatedin the ED.

The physical examination revealedan awake, alert, cooperativeboy. His vital signs were a temperatureof 37.8C (100F), a pulse rate of84 beats per minute, a respiratoryrate of 20 breaths per minute, and ablood pressure of 126/72 mm Hg.Examination of the right forearm revealeda 3-cm, irregular, deep lacerationon the radial aspect of the mid todistal, dorsal right forearm. In addition,a 4-mm puncture wound wasnoted on the ulnar aspect of the arm.

Swelling and erythema surroundedthe larger laceration. The erythemaextended along the posterior surfaceof the arm toward the axilla.Neurological examination revealedloss of sensation over the dorsum ofthe right thumb. The remaining findingsof the physical examinationwere normal, including motor andcirculatory function.

Consultations with pediatric surgeryand orthopedics were obtained.The patient was taken to an operatingroom for wound exploration anddebridement. Significant seropurulentdrainage was encountered, andpartial laceration of the thumb andfinger extensor muscles was noted.Distally in the wound, the radial sensorynerve was lacerated. After debridementand copious irrigation, aPenrose drain was placed and thewound was left open and dressed.

Postoperatively, empiric intravenouspiperacillin/tazobactam, gentamicin,and acyclovir were administered.Acyclovir was given becauseearly initiation of antiviral therapywith valacyclovir or acyclovir coupledwith rapid and thoroughcleansing of the wound may preventsevere disease or death.⁴Wound debridementwas performed daily for 4days, after which secondary closureof the wound was allowed. After 10days of hospitalization, the patientwas discharged home and continuedto receive parenteral antibiotic therapyto complete a 14-day treatmentcourse. His wounds healed uneventfully,with normal function.

Aerobic and anaerobic cultures ofwound material grew multiple organisms,including Streptococcus mitis,Enterobacter cancerogenus (Enterobactertaylorae), Neisseria subflava,Rothia dentocariosa, and Roseomonasgilardii. The speciation of the last 3organisms was confirmed by DNAsequencing. It was determined thatS mitis was susceptible to penicillinand cefotaxime. E cancerogenus wassusceptible to cefotaxime and piperacillin.Susceptibility testing was notperformed for R dentocariosa and Rgilardii because there are no recommendedstandards from the NationalCommittee for Clinical LaboratoryStandards for susceptibility testingof these organisms.

Viral cultures of wound materialwere negative for herpes B virus.Similarly, acute and convalescentserum samples from the child werenegative for antibodies to herpes Bvirus. Assistance from the zoo veterinarianwas sought in evaluatingthe gibbon. Serological assays werenegative for herpes B virus and hepatitisA, B, and C viruses.

Discussion

The management of bites of commonlyencountered domesticatedanimals is generally straightforward,consisting of wound irrigation, verificationof the patient's and animal'simmunization status, and the use ofprophylactic antibiotics.⁵ Because ofthe rarity of nonhuman primate bitesin the United States, most physicianshave no experience in the managementof these wounds.

Among a series of 59 animal bitesin hospitalized patients, only 3 werecaused by nonhuman primates.² In 1case, delay in seeking medical careresulted in a wound infection. In theremaining 2 cases, no infection occurred,possibly because infectionwas prevented by prophylactic antibiotictherapy with either penicillinor ampicillin.

In a larger series of 332 animal biteinjuries that were treated in an ED,only 5 resulted from monkey bites.⁶None were associated with complications.Information about the typeof antibiotic prophylaxis given wasnot provided.

In a report of 4249 animal-relatedinjuries, 28 (0.7%) were monkey-related.³ Ten of these injuries weresecondary to bites, and 7 were due toscratches. All monkey-related injurieswere managed in an outpatientsetting, and there were no complications.Information about severityof injury and type of prophylaxisor treatment was not included in thereport.

Nonhuman primates pose a riskto animal handlers, including researchpersonnel who have contact with them. A case of an infectedmonkey bite wound without complicationswas reported in a researchstudent who was working with arhesus monkey.⁷

Organisms in the oral flora ofnonhuman primates are similar tothose in humans. They include Enterobacteriaceae,Eikenella corrodens,alpha;-hemolytic streptococci, Neisseria,anaerobes, and Haemophilus parainfluenzae.^7,8 The oral flora of 17 rhesusmonkeys was studied; the aerobicand facultative anaerobic flora consistedof Neisseria species (19.8%), alpha;-hemolytic streptococci (19.8%), andH parainfluenzae (17.2%).⁹ Pasteurellamultocida was not isolated in thisstudy. Gram-negative enteric organismswere identified less often.

The case presented in this reportdocuments the polymicrobial natureof infections that can result from thebite of a nonhuman primate. Interestingly,2 bacteria that had been previouslyunreported in associationwith nonhuman primate bites wereidentified in our patient: R dentocariosaand R gilardii. R dentocariosa isa facultative, non-spore-forming anaerobicGram-positive rod and aninhabitant of the human oropharynx.Human infections, includingendocarditis and peritonitis, havebeen reported.^10,11

R gilardii is a Gram-negative coccobacillus.It has been isolated fromenvironmental sources and from thegenitourinary and respiratory tracts.It can be an opportunistic humanpathogen that causes sepsis, especiallyin immunocompromisedpatients.^12,13

Orthopedic complications of simianbite infections include osteomyelitis,tenosynovitis, and flexioncontractures.^2,8 Our patient sustaineda nerve injury, which resultedin sensory loss over the dorsum ofthe thumb.

A dreaded infectious complicationof nonhuman primate bites isherpes B virus infection. Herpes Bviruses are enzootic among wild OldWorld monkeys (Macaca species).Herpes B virus infections in humansresult from bites or scratches fromsimians shedding the virus. In humans,these infections can cause anascending meningoencephalitis witha mortality rate of 70%.^8,14 The reportedincubation period for herpesB virus ranges from 2 days to 5weeks.¹⁵

Patients with simian bite injuriesshould be managed in consultationwith an infectious diseases specialist,surgeon, and veterinarian. The initialtreatment of a simian bite woundis similar to that of a human bitewound. It includes thorough irrigationof the affected area and prophylacticantibiotic treatment withamoxicillin/clavulanic acid. The patient'stetanus immunization statusshould be evaluated and, if necessary,prophylactic treatment shouldbe provided.

In the case of macaque bites, evaluationfor herpes B virus infection iswarranted because multiple Macacaspecies are documented carriers andshedders of the virus.7 In cases ofbites by any other primate species,including gibbons, the potential severityof herpes B virus infection inhumans warrants checking for itspresence despite the extremely lowrisk.

If the wound is infected, ampicillin/sulbactam can be used to provideempiric coverage against mostisolates of streptococci, staphylococci,enterococci, E corrodens, anaerobes,and Enterobacteriaceae. In patientswith an allergy to penicillin,extended-spectrum cephalosporinsin combination with clindamycin isan option.

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