March 2006

With summer just around the corner, more children will be spending their days playing outside, along with the increased risk of various outdoor threats. As I recall from when my children were children (about 25 years ago), they faced everything from fire ants to chiggers, poison ivy to bull nettle, sunburns to impetigo, swimming pool accidents (including backyard wading pools) to puncture wounds of their feet and potential attack by neighborhood animals, both domestic and wild. By the way, I place human predators in this same category. The following case was a child admitted a couple of summers ago.

A 4½-year-old girl was admitted to the hospital for treatment of pain, erythema and swelling of an injured left cheek and ear. The history of her complaint started with a dog bite to the area three days before at a neighbor’s house. She said it was an unprovoked attack by a Chow-mix dog, but was not clearly witnessed. According to the dog owners, the dog had not been behaving abnormally, and its immunizations (including rabies) were up-to-date. The child was evaluated in the emergency department where she was treated by the plastic surgeon on-call with copious irrigation and closure, and tetanus prophylaxis was recommended, but not given. She was sent home on prophylactic amoxicillin-clavulanate (Augmentin, GlaxoSmithKline) at 45 mg/kg/day, divided twice daily. She was also given rabies immune globulin and the first dose of rabies vaccine. She returned to the plastic surgery clinic three days later due to the above symptoms.

Her past medical history was unremarkable and her immunizations were documented up-to-date through her 18-month boosters. She has no known allergies and was taking only the prescribed amoxicillin-clavulanate. She had significant animal exposure as her family has two dogs, three cats and three birds in the home. Her review of systems was positive only for the chief complaint.

Examination on admission revealed normal vital signs and a normal-appearing 4½-year-old child except for the obvious injury to her left cheek and ear as shown in figure 1. The area of injury was very tender to touch, swollen and red. Her oral exam was normal and there was no palpable adenopathy. She was taken to the operating room for drainage, and pus obtained was sent to the lab for Gram’s stain and culture.

Part 1: What’s Your Diagnosis?

1. Staphylococcus aureus cellulitis
2. Streptococcus pyogenes cellulitis
3. Pasturella multocida cellulitis
4. Eikenella corrodens cellulitis

Part 2: Should she continue rabies prophylaxis?

1. Yes
2. No

Part 3: Should she be given tetanus prophylaxis?

1. Yes
2. No

Answer

Statistically, the most likely organism would be Pasturella multocida; however, infection occurring in spite of amoxicillin-clavulanate prophylaxis makes one think more of methicillin-resistant Staphylococcus aureus (MRSA). However, the culture grew P. multocida that was sensitive to amoxicillin-clavulanate. So much for prophylaxis! Remember, antibiotic prophylaxis is limited by variables like compliance, absorption and resistance patterns. After admission, she was treated with IV ampicillin-sulbactam (Unasyn, Pfizer) for seven days in addition to two trips to the operating room for drainage. She was sent home on amoxicillin-clavulanate with a good outcome as seen in figure 2, one week after discharge.

Dog bites are not as likely to get infected as cat bites because of the shearing-type injury dog bites usually produce (figures 3a & 3b) compared with the puncture-type injury of a cat bite (figure 4). But, obviously, some do get infected. S. aureus and Streptococcus pyogenes can also complicate a dog bite, but just not as likely as P. multocida. Eikenella corrodens may be seen in a case of a human bite, but not likely with a dog bite. Amoxicillin-clavulanate is still a reasonable choice for prophylaxis of bite victims who need to be given prophylaxis. But again, one just needs to consider the limitations of prophylaxis in general and MRSA specifically nowadays.

Rabies and tetanus prophylaxis

Since the biting dog was a domestic, immunized dog with otherwise normal behavior, AND we had the ability to observe the dog in a controlled environment for 10 days, rabies prophylaxis would NOT be necessary in this case, according to the Red Book. Having said that, the emergency department staff started the child on the five-shot series of rabies immunizations and gave rabies immunoglobulin (RIG). There’s something about the lethality of rabies that makes otherwise rational physicians choose not to be the one responsible for deciding not to immunize. That’s not to say there is something wrong with these providers, it’s just human nature. Also, in the real time environment of the emergency department, one cannot be sure of all the facts regarding the dog in question.

These cases require a good working relationship with the animal control and public health personnel who can help facilitate the management of the animal. When in doubt, the animal should be euthanized and the head sent to the state lab for examination, which, unfortunately for the dog, was done in this case. Having been bitten twice as a youngster, I grew up having no great love for dogs, but I think these animals are unnecessarily sacrificed in lieu of observation and following established guidelines. I often get the feeling it’s done for punitive rather than clinical reasons. Oftentimes, especially in Texas, the justice is dealt out by the father of the bitten child at the end of a shotgun, which may hamper the process and commit the child to receive five doses of rabies vaccine and RIG unnecessarily. But again, the stakes are very high if you’re wrong. There have been six case reports of recovery after rabies infection. The most recent was a report in The New England Journal of Medicine last June of a child with rabies who survived after a prolonged course of intensive care that included drug-induced coma and the antiviral agents, amantadine and ribavirin. The case was initially reported in the Morbidity and Mortality Weekly Report (MMWR), Dec. 24, 2004. If one works in a referral center that may receive a case of rabies, one may want to have these papers handy as a reference or better yet, call the CDC for guidance at 800-232-4636.

Although most cases of rabies occur as a result of the bite of a rabid animal, other, nonbite exposures may result in the infection. The scary thing is, sometimes the source of exposure is unknown. In the summer of 2004, three cases of rabies occurred secondary to solid organ transplantation from a single donor who unknowingly died of rabies encephalitis. All three cases were fatal and confirmed with central nervous system tissue revealing Negri bodies and the presence of rabies viral antigen by direct flourescent antibody. This was also reported in MMWR, July 1, 2004. These are some of the reasons physicians on the frontline have a very low threshold for giving rabies prophylaxis, and even when the dog is sent to the state lab for examination, the results are usually not known in time to make much of a difference in the first few doses of vaccine and RIG prophylaxis. The recommended schedule for the vaccine is on days 0, 3, 7, 14 and 28. RIG should have half the dose injected around the bite site, if possible, and the rest intramuscularly. Consult the Red Book for specific guidelines.

Since the patient’s immunizations were documented up-to-date through her 18-month boosters, which means she had received four doses of tetanus toxoid, and her last dose was within the last five years, there was NO need for tetanus prophylaxis, even though the plastic surgery staff recommended it.

It is interesting that the patient’s family has two dogs, three cats and three birds living in their home. Knowing that dogs have an acute sense of smell, it makes one wonder that if the child had the odor of one or more of the family pets on her when she was attacked, could that have contributed to the event? I have never read of this being investigated, but it makes sense to me that an otherwise “friendly” dog may be “turned on” by the smell of another dog or cat, which, in turn, may make them aggressive toward a small child. Just food for thought!

Comment

I would like to offer congratulations to my old friend, Col. Charles (Chuck) Callahan, pediatrician in the Army Medical Corps, who just assumed the position of deputy commander of the Walter Reed Army Medical Center in Washington. His position prior to this was as chief of the department of pediatrics at the venerable Tripler Army Medical Center in Hawaii. Through his insistence on academic excellence and his willingness to place himself in harm’s way with a tour in the Middle East last year, he has shown what hard work and leadership-by-example can do for you in an organization that really has no official pediatric mission. Very few pediatricians have reached the loftier ranks of command, and only one — Vice Adm. Harold Koenig, COL, USN (Retired) — has been appointed surgeon general of one of the military services. John R. Pierce, COL, MC, USA (Retired) was the last pediatrician to hold this coveted position as deputy commander at Walter Reed. Pierce, by the way, wrote a book that was published last year called Yellow Jack: How Yellow Fever Ravaged America and Walter Reed Discovered Its Deadly Secrets (John Wiley and Sons). I recently received my copy and will report on it in a future column. Col. Callahan and Col. Pierce are shown in figure 5, flanking Jim Shira, COL, MC, USA (Retired), former chief of pediatrics at Walter Reed; this was taken at the 2005 Uniformed Services Pediatric Seminar (USPS). As I have mentioned in previous issues, the USPS will be in Portsmouth, VA, this month. It’s probably not too late to go. Please keep in touch at jhbrien@aol.com.