Case Presentation by Dr. Daniel Helzer
A pleasant 43 year old female from Royal Oak presents to the ED ARC complaining of a bite wound. She is embarrassed to tell you but eventually the truth reveals itself. She enjoys feeding the hordes of black squirrels that reside in her backyard. She gets a kick out of letting them eat out of her hand and was feeding them freshly baked oatmeal cookies.
While taking part in this extraordinary event, a black squirrel with a white tail gets into a scuffle with another over the last morsel of cookie. Mistakenly the squirrel bit your patient on her right foot during the scuffle. The patient, visibly shaken, thought she should come in to get checked out. She is otherwise healthy, takes no medication, no allergies, has no clue when her last tetanus update was, and has normal vital signs on presentation. PE demonstrates below on dorsum of foot, wound exploration reveals superficial wounds with no deep puncture wounds.
1) Initial management of this patient would include?
A) Reassure and discharge home.
B) Wound irrigation, bacitracin dressing and discharge with wound care instructions.
C) Wound irrigation, bacitracin dressing, Tdap and discharge with wound care instructions.
D) Wound irrigation, bacitracin dressing, Tdap, Human rabies diploid cell vaccine and discharge with wound care instructions.
E) Wound irrigation, bacitracin dressing, Tdap, Human rabies diploid cell vaccine, Human rabies immune globulin and discharge with wound care instructions.
Unfortunately you pick choice A. The patient returns to the ED 9 days later complaining of Flu like symptoms x 2 days that keep getting worse despite Tylenol. She has been having headaches, fevers, arthralgias particularly in her knees, runny nose, and 1 episode of vomiting. Brief initial PE was nonspecific, neuro exam was normal.
VS: BP 115/85, HR 112, RR 21, Temp 39.4
The sepsis bug fires and while you are trying to figure out how to make it disappear you remember seeing the patient for a squirrel bite and run over to see how it healed up. The wound has completely healed but you note this rash on BOTH of her feet and hands upon inspection.
2) The causative organism is?
A) Rickettsia rickettsii
B) Neisseria meningitidis
C) Rabies virus
D) Streptobacillus moniliformis
E) Leptospira Icterohaemorrhagiae
3) The patient receives 1g Tylenol for fever and vital signs normalize in ED. Proper treatment and disposition of this patient would be?
A) Oral Augmentin 875 mg x 10 days and D/C home
B) IV Penicillin G 600,000 IU/day and medicine admission
C) Rabies vaccine and Ig (you failed last time), MICU admission, and cross your fingers
D) Oral doxycycline 100mg Q12 and observation admission
E) IV ceftriaxone, vancomycin, and decadron and Neuro ICU admission
The Final Diagnosis?? Rat Bite Fever.
The first question deals more with basic management of animal bites. Obviously basic wound management should include wound irrigation and bandaging. Life saving tetanus should be given. Rabies vaccination is the next important consideration in management. After a bite wound/ exposure proper post exposure rabies management includes providing the rabies diploid vaccine and possibly the rabies immune globulin. It is a time consuming and expensive process so it is important to know who needs it and who does not.
Previously unvaccinated people should receive the vaccine intramuscularly at 0, 3, 7, and 14 days. For adults the vaccine is given in the deltoid area; for children, it may be given in the anterolateral aspect of the thigh. In addition to rabies vaccine, these people should also receive rabies immune globulin (HRIG) at the same time as the first dose of the vaccine to provide rapid protection that persists until the vaccine works.
Previously vaccinated people should receive two doses of the vaccine intramuscularly—the first immediately, the other three days later. HRIG is unnecessary and should not be given.
HRIG is given in a weight based dosage and is calculated in Units. Average cost for a 70 kg adult is $1500. The entire dose of HRIG should be injected directly into and around the bite wound if feasible and if a wound is evident; the remainder of the dose should be given intramuscularly in the upper arm, lateral thigh, or gluteal muscle.
So who needs this?? It can get a little complicated but here is the CDC algorithm.
Keep in mind for stray dogs in Wayne County the recommendation is to initiate rabies post exposure prophylaxis and to not wait for apprehension of the animal.
As you can see small rodents including our crazy black squirrel is low risk and does not require rabies post exposure prophylaxis.
Answer to Question #1 is C
Antibiotic prophylaxis is also not recommended for rodent bites. Animal bites that may require antibiotics prophylaxis include dog bites to hand, cat bites to hand, camel bites, pig bits, and monkey/primate bites.
Now onto the diagnosis. Rat Bite Fever, caused by Streptobacillus moniliformis bacteremia, is a systemic illness classically characterized by fever, rigors, and polyarthralgias.
Answer to Question #2 is D
Historically transmission occurs via rat bits hence its name but can occur via other rodents including mice, squirrels, guinea pigs, hamsters, ferrets, ect. The bite wound is typically healed by the time rat bite fever sets in and signs of local cellulitis or abscess formation at the bite site should steer one away from the diagnosis.
Systemic onset usually occurs in 7 – 10 days. Fever is the most common manifestation usually intermittent and above 38.0 with rigors. Other nonspecific complaints are present with the fever as well.
50% of patients develop migratory polyarthitis typically in knees and hips.
75% of patients develop a rash that may appear maculopapular, petechial, or purpuric. Hemorrhagic vesicles may also develop on the peripheral extremities, especially the hands and feet, and are very tender to palpation. Note the hemorrhagic vesicles in the image above. Appearance of this rash, especially the hemorrhagic vesicles, in the setting of an otherwise nonspecific set of disease signs and symptoms should strongly suggest the diagnosis of rat bite fever.
Complications involve endocarditis, myocarditis, polyateritis nodosa, meningitis, abscess, ect. 10% of untreated cases lead to death.
Treatment is with IV penicillin, there is very little resistance.
Answer to Question #3 is B
- CDC: Rabies. http://www.cdc.gov/rabies/index.html
- Rat Bite Fever and Streptobacillus moniliformis. Clin. Microbiol. Rev. January 2007 vol. 20 no. 1 13-22. http://cmr.asm.org/content/20/1/13.full#cited-by
- Rosen’s Emergency Medicine, seventh edition, 2010, pages 733-742, Marx.