A Scab Story Bites Back

A Scab Story Bites Back

March 6, 2017 Karie Youngdahl

Curator Dhody & John Faherty of the Philadelphia Department of Public Health
Curator Dhody & John Faherty of the Philadelphia Department of Public Health. Photo by Evi Numen, Mütter Museum

Today's blog post is by Robert D. Hicks and Anna N. Dhody

“What if possibly infectious samples of smallpox still exist . . . in museums and libraries?” That was the question posed in “A Scab Story,” a blog posted here on August 4, 2014. The essay reviews the few examples of 19th century scabs that have appeared in library collections (and a few other places) over the past dozen years and argued that they might prove to be a scientific boon because we lack historical examples of smallpox and smallpox vaccine material. The blog concludes by suggesting how museum and library employees ought to handle any such material they find in their collections, including conveying old scabs to the Centers for Disease Control and Prevention (CDC) for analysis. The essay reminded readers, “And don’t forget to blog about it.”

Admittedly, one of us (Robert D. Hicks) fantasized about finding an ancient scab from an early vaccination in the collections of the Mütter Museum and Historical Medical Library of The College of Physicians of Philadelphia that would yield a crucial insight about the origin of the smallpox vaccine. One should always be careful about what one wishes for. In April 2016, while the rest of the museum staff was away on a field trip, Robert took a new employee into collections storage for a tour. While inspecting phlebotomy tools, the new employee called attention to a small, pretty, red leather roll-up case. Robert saw a handwritten label on it which read, “vaccination kit.” Not having noticed it before, he removed it (with nitrile-gloved hands) and examined its components: a tiny lancet, two square glass plates, and a tiny tin box with a sliding lid. He opened the lid and beheld crumbled scabs which had the appearance of tiny fragments of topaz. At once, he recognized how the kit was intended for use because he had researched vaccination practices during the American Civil War (see “Spurious Vaccination in the Civil War”).

Because cowpox, thought to be the vaccination material Edward Jenner first used, was a rare spontaneous infection, humans were often used as intermediaries to produce vaccine material. To harvest vaccine, the physician used a lancet to poke a raised pustule on a on a recently vaccinated person to obtain the fluid within (called “lymph” during the 19th century). The physician made a tiny dermal incision in the arm of a healthy person into which the anointed lancet was inserted. Ideally, the healthy person would develop a mild infection caused by the vaccine, recover, and then enjoy immunity from smallpox infection. The original lymph removed would have been placed on a glass plate, water added, and then the second plate pushed down upon the first to smear the substance into a mix. The mix might furnish sufficient material for multiple piercings. If the physician waited to harvest vaccine material until the pustules dried and hardened into scabs (called “crusts” during the 19th century), they would be placed between the plates, pulverized, and with water added the physician could make a paste to serve multiple vaccinations.

Kit with scabs in two compartments
Kit with scabs in two compartments. Photo by Evi Numen, Mütter Museum

Robert searched the phlebotomy drawer for more vaccination kits and came up with five in various states of preservation. Either the tins contained scab material or the glass plates showed a milky residue: all five kits had something suspicious. Robert removed all kits into his office and then emailed curator Anna N. Dhody with the news. After she recovered from her surprise, and upon promising herself never to leave the museum director alone with the collections again, she contacted the Pennsylvania Department of Health and CDC. Health officials wanted the specimens, and two days later representatives from the Philadelphia Department of Public Health came to the museum to collect all kits and send them to CDC in Atlanta, Georgia. Based on the previous episodes (outlined in “Scab Story”), both organizations agreed that the infection risk was very low, so they asked Robert to alert them if he became sick over the following weeks.  He didn’t.

By the end of April, CDC had assayed the samples and found them “consistent with what we have obtained in the past for other historical relics (example, Virginia crust).” The Virginia reference involved a 2011 incident at the Virginia Historical Society described in “A Scab Story.” Three of the five kits yielded hits for an unknown pox-family virus: scab material in two kits and residue on glass plates in the third. The results “suggest the presence of Orthopoxvirus DNA in these specimens that is not consistent with variola virus or contemporary strains of vaccinia virus.” Variola and vaccinia refer to the smallpox virus and the Orthopoxvirus used as a vaccine against smallpox, respectively. If the samples do not indicate variola or current-day vaccinia, then what is the best guess for the source? The samples may represent an older vaccinia virus that assays cannot currently detect, or another Orthopoxvirus, possibly one that infected horses[i] or another mammal. We will know more once we know the sequence of the virus. Note that there is no relationship among the vaccination kits other than their being part of the same museum collection. There is no evidence that the suspicious substances in the kits come from the same source.

By August, CDC tried to culture the pox variants and while the attempts failed, they at least determined that the viral remnants were not viable. By the end of November, Dr. Hendrik Poinar from the Ancient DNA Centre at McMaster University, Canada, joined the conversation with CDC. An expert on ancient DNA extraction, his team identified a strain of cholera in a fluid-preserved specimen of cholera-infested tissue which has been preserved since 1849 at The College of Physicians of Philadelphia (see “Cholera Specimen Reveals its Genetic Secrets”). The cholera identification marked the first instance of viable DNA extraction from a 19th-century fluid-preserved specimen. Poinar’s identification constituted an etiological milestone. Can his team do with the pox specimens what the CDC was not able to do? Could his laboratory repeat the breakthrough, but with Orthopoxvirus this time? At this writing, CDC is preparing to ship the specimens to McMaster.

Meanwhile, Dr. Poinar and his scientific colleagues have achieved another insight through recovery of variola from a 17th-century corpse. Their insight complicates our historical understanding of smallpox and may have implications for the study of the vaccination kits. Poinar’s team, headed by the DeGroote Institute for Infectious Disease Research at McMaster isolated and sequenced DNA from a Lithuanian mummy.  The corpse, a child, had been interred in the cool, dry crypt underneath the Dominican Church of the Holy Spirit in Vilnius, where it naturally mummified over the centuries. The researchers compared the reconstructed DNA of the mummy smallpox with a reference specimen obtained in India during the 1960s. With the two comparative specimens, scientists constructed a “molecular clock” that enabled them to trace the genetic evolution of the child’s disease. The researchers’ characterization of the mummy’s “strain provides a key calibration point in the epidemiological history of smallpox.”[ii] In their study, Poinar and his colleagues conclude that the common ancestor of all smallpox cases dates to between 1588 and 1645. If this is true, what about reported smallpox cases before that time, extending to the era of the Egyptian pharaohs? If the Mütter’s 19th-century specimens are not smallpox, then what are they? If CDC’s suggestion that the scabs derive from an animal virus is true, then what animal? Nineteenth-century sources maintain that Civil War doctors experimented with obtaining virus from many animals. Perhaps we may now learn the source of vaccination material during the 1800s and better understand how pox viruses have evolved in recent times. It’s up to the Ancient DNA Centre.

2017 should produce exciting results to this story.  Watch for our next blog post, “A Scab Story: The Virus Awakens."

Robert D. Hicks, PhD
Director, Mütter Museum/Historical Medical Library
William Maul Measey Chair for the History of Medicine

Anna N. Dhody, MFS
Curator and Director, Mütter Institute
The College of Physicians of Philadelphia


[i] Kendall A. Smith, "Edward Jenner and the Smallpox Vaccine," Frontiers in Immunology 2 (2011):  1-6

[ii] Ana T. Duggan, et al., “17th Century Variola Virus Reveals the Recent History of Smallpox,” Current Biology 26 (2016): 3411.

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