A correction has been published: N Engl J Med 2001;345(24):1784.
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Case Report
During September 2000, a 28-year-old woman from northeastern Ohio who had epidermolytic hyperkeratosis11 and was 15 weeks pregnant presented to her physician with lesions that had appeared after she was bitten by her dog six days earlier. She had sustained mild abrasions on her forearm and a puncture wound on a finger. The finger bled and was washed thoroughly with soap and water. She did not notice bleeding on the superficial forearm abrasion and did not wash it. Three days after the bite, she observed two small blisters approximately 6 cm apart on her forearm, which progressed to nontender, vesicular lesions that were approximately 1.5 cm in diameter at the time of her initial presentation. She was given amoxicillin–clavulanate. Two days later, she presented to a hospital emergency room with progressive pain, erythema, swelling of the left forearm, and necrosis of the vesicular areas, which had expanded to 2 cm in diameter (Figure 1).
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The next day, the patient's arm appeared less swollen and erythematous, and axillary tenderness improved. Amoxicillin–clavulanate was prescribed, and she was discharged on the following day. Two days later, she had worsening erythroderma that was thought to be a reaction to the antibiotics, and treatment with amoxicillin–clavulanate was discontinued. The next day, she presented to the hospital emergency room with general erythroderma, mild burning sensations and a feeling of tightness in the face, and generalized exfoliation on her face and neck. Her incision was healing, and she felt better overall. Five days later, a thick layer of epidermis exfoliated from her palms and soles. Ten days later (30 days after the dog bite), a residual eschar was removed for laboratory examination. Exfoliation had stopped by four days later, and her wounds had healed. The patient remained free of symptoms; her pregnancy was normal, and she delivered a healthy child in March 2001. Samples from the placenta and serum from umbilical-cord blood were shipped to the CDC.
Methods
After the patient gave informed consent, material from the swabs and homogenized portions of the eschar were inoculated onto a monolayer of Vero cells and maintained at 37°C. Approximately 48 hours after infection, cells scraped from a tissue-culture flask underwent centrifugation, and the pellet was processed for thin-section electron microscopy.12 Homogenized portions of the eschar were prepared by an established method of negative staining for orthopoxviruses.13 The DNA was extracted from approximately 25 µl of Vero-cell cultures infected with a swab of the skin lesion, 50 µg of homogenized eschar, and 25 µg of the homogenized associated skin tissue and was compared with noninfected Vero-cell culture and dilutions of reference vaccinia–rabies glycoprotein virus.9,14 Briefly, deproteinization occurred at 37°C for two hours in an extraction buffer containing proteinase K (0.2 mg per milliliter). Purification of DNA was performed by phenol–chloroform extraction. Pelleted DNA was reconstituted in 200 µl TRIS–EDTA buffer (pH 8.0). Amplification of DNA was accomplished with the use of specific primers for the vaccinia virus thymidine kinase gene or the rabies virus glycoprotein gene by denaturation for 2 minutes at 95°C, 40 cycles of denaturation at 95°C for 1 minute, annealing at 55°C for 2 minutes, extension at 72°C for 7 minutes, and final extension at 72°C for 10 minutes. Primer sequences are given in Table 1. The polymerase-chain-reaction (PCR) products (20 µl from a 100-µl reaction mixture) were examined by electrophoresis on a 2 percent agarose gel containing ethidium bromide. Specific bands of the expected molecular weight were excised and sequenced with the use of an ABI 377 sequencer (Applied Biosystems, Foster City, Calif.) (Table 1). Routine virus-neutralization and indirect immunofluorescent assays were performed to detect antibodies against rabies and vaccinia viruses with the use of serum from the patient and the umbilical-cord blood.18,19 Groups of Swiss ICR mice four to six weeks of age were inoculated parenterally and orally with the cell-culture supernatant to evaluate the characteristics of the infectious agent.
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Cytopathic effects were observed in cell culture within 12 hours after incubation with material from the patient. Typical morphologic features of orthopoxviruses were observed by electron microscopy (Figure 2). Positive PCR products were obtained (Figure 3) for all but the samples from the placenta. Sequences exhibited 100 percent homology with those expected for vaccinia–rabies glycoprotein virus (Table 1). Negative control human serum had a titer of less than 1:5 in all tests. In contrast, the titers of antibodies against vaccinia virus in the patient's serum at three weeks after the bite were greater than 1:125 on the virus-neutralization assay and greater than 1:625 on the indirect immunofluorescent assay; the titer of antibodies against rabies virus was greater than 1:18,000 on the virus-neutralization assay. Serum obtained from umbilical-cord blood had a titer of 1:250 for antibodies against rabies on the virus-neutralization assay. Safety and efficacy data were consistent with the results of previous studies of vaccinia–rabies glycoprotein virus infection in mice (data available as Supplementary Appendix 1 with the full text of this article at http://www.nejm.org).3,9
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We have documented human infection with vaccinia–rabies glycoprotein virus. For more than a decade, tens of millions of baits containing vaccine have been used throughout Europe and North America. Use of the oral rabies vaccine for wildlife substantially augments conventional programs for the control of rabies. With this approach, western Europe has nearly eliminated rabies in foxes. Nevertheless, the vaccinia–rabies glycoprotein virus is a self-replicating agent, albeit a highly attenuated one, and may cause adverse events, particularly in hosts with altered immunocompetence and in persons for whom smallpox vaccination is contraindicated, such as pregnant women or patients with an exfoliative skin condition.20 Vaccinia immune globulin may be useful if administered promptly for the treatment of eczema vaccinatum and some cases of progressive, ocular, or severe generalized vaccinia, but its effectiveness is questionable if administration is delayed until well after the onset of symptoms.
Despite the large number of baits containing vaccinia–rabies glycoprotein virus that are widely distributed in the field, human contact with the vaccine and adverse events appear to be rare. In northeastern Ohio, from the spring of 1997 to the fall of 2000, 3.6 million baits were deployed over an area of 6497 km2 (2509 mi2). Each year, bait was distributed for approximately one week during both spring and fall. In rural areas, aircraft dropped approximately 85 percent of the baits, flying over uniform grid lines 0.5 km (0.3 mi) apart. The remaining 15 percent were delivered by automobile and by hand in urban and suburban areas. Ground-distribution personnel placed baits in areas where raccoons were likely to be found. The target density was 75 baits per square kilometer, or 1 per 3.3 acres. No cases of rabies in raccoons were reported in Ohio during 2000 — a benefit unprecedented among affected regions of the United States over the past 50 years.
With large-scale programs for oral rabies vaccination, people will inevitably find vaccine-laden baits. In Ohio, toll-free telephone numbers are printed on baits, and callers are automatically routed to a rabies information line. Since the inception of the program, 160 reports of human contact with baits have been filed. In 100 reports (62 percent), baits were found in yards and near residences. Twelve reports (8 percent) indicated that baits were found in public areas (parks, roads, or sidewalks). In the remaining reports, the location of the bait was unspecified. A total of 100 callers indicated that they had had contact only with the outer portion of the bait, with the vaccine sachet intact. In 20 instances, persons had probably been exposed to vaccine, with evidence that the inner sachet had ruptured, usually contaminating the hands.
Three of 160 reports involved persons who listed a health condition that may have been a contraindication to vaccination with the vaccinia virus: one subject was six months pregnant but stated that she had washed her hands after touching the bait; another stated that she had diabetes and rheumatoid arthritis, but follow-up investigations indicated that although she had touched the bait, the vaccine sachet was intact; the third was the patient in the current report. After exposure to the vaccine, the risk of an adverse outcome can be minimized if proper and prompt first-aid procedures, such as hand washing, are followed. Although the overall numbers in Ohio remained fairly consistent each year, reports logged decreased from 7.1 per 100,000 baits in 1997 to 2.1 per 100,000 baits in 2000. Rates of human contact with baits are probably somewhat higher because some incidents go unreported.
Active surveillance of the telephone logs indicates that pets can facilitate human exposure to rabies vaccine. Dogs are attracted to baits and bring them to their owners. Moreover, dogs can rupture the sachet, increasing the chance of human exposure to vaccine. Seventy-eight percent of the reports in Ohio involved domestic animals finding or eating baits. Of these, 120 mentioned dogs, 3 cats, 1 both a dog and a cat, and 1 the possible exposure of cattle at a feedlot. Ten callers described removal of a bait from a dog's mouth. Of 20 reports of contact of the skin with a ruptured sachet, 18 involved dogs. No incidents were documented in which dogs consumed bait and subsequently became ill.
The incident we describe reinforces the message that public and professional awareness is critical to any successful vaccination program. To prevent complications, state programs require ongoing training in the strategic placement of baits to minimize contact by humans and pets. Before bait is distributed, press releases and information describing dates and areas of operation should be given to the media, licensed veterinarians, and infectious-disease specialists in hospitals in the targeted counties. People should be requested to keep pets indoors or confined during baiting campaigns and should be advised to avoid touching baits. Residents should call a toll-free number with questions or to report finding baits. When owners discover a pet eating a bait, they should not risk being bitten by removing it from the animal's mouth. If contact with the vaccine occurs, exposed areas should be washed thoroughly. If signs or symptoms suggestive of infection with vaccinia–rabies glycoprotein virus develop, patients should seek medical consultation. Unfortunately, as oral-vaccination programs become more common, the public and medical professionals may become more complacent and less likely to seek information or to respond to events that involve exposure to the live recombinant vaccinia–rabies glycoprotein virus.
We are indebted to S. Crone, C. Edwards, M. Durica, P. Kay, I. Krishnarao, P. Morrill, and T. Shipman for assistance with the investigation; to M. Byrnes for help with photography; to C. Goldsmith for aid in thin-section electron microscopy; to C. Humphries for preparation of the grid used for the negative-staining electron microscopy; and to the staffs of the Ohio Department of Health and the Viral and Rickettsial Zoonoses Branch of the CDC for excellent overall technical assistance and useful discussion of the manuscript.
Source Information
From the Centers for Disease Control and Prevention, Atlanta (C.E.R., L.A.O., M.N., S.G.W., R.V.G., M.G., C.A.H.); Trumbull Memorial Hospital, Warren, Ohio (L.B.); and the Ohio Department of Health, Columbus (K.S.).
Address reprint requests to Dr. Rupprecht at the Rabies Section, Centers for Disease Control and Prevention, Mailstop G-33, 1600 Clifton Rd., N.E., Atlanta, GA 30333, or at cyr5{at}cdc.gov.
References
ek Z, Ladnyi ID. Smallpox and its eradication. Geneva: World Health Organization, 1988:149-50.
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