Canyon Creek Schoolhouse Laboratory 100^th Anniversary

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Although it was known that RMSF was caused when the Rickettsia rickettsii bacteria infected a Dermacentor andersoni tick that then bit a human, more questions remained. Was the bacteria spread by other species of ticks? And exactly how did the ticks get infected? To find out where the ticks were picking up the infection and to answer a number of other questions, ticks had to be collected in the wild.

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Man dressed in white with pants tucked in boots waves large white flag over meadow grass in high mountains.

A staff member of the Canyon Creek Schoolhouse Laboratory—possibly Dr. Ralph Parker, C.M. Salisbury, or George Cowan—dragged a white flannel flag over brush and grass to gather ticks in the Bitterroot Valley, Montana. He wore a white jump suit over his regular clothes, tucking his pant legs into the top of his high, laced boots. When they returned from such outings, the men would check each other closely in case a tick had attached itself to one of them.

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Image: Office of NIH History and Stetten Museum, 1522

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In 1923, a mountain goat (perhaps this mountain goat kid) taken by George Cowan had over 1,000 ticks engorged ticks on it. It was with these ticks that Dr. Roscoe Spencer came up with his idea for an RMSF vaccine.

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Image: Rocky Mountain Laboratories, 264

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Cataloguing Ticks

As the field researchers gathered many species of ticks and ticks in many stages of their life cycle, Dr. Robert Cooley developed a huge collection of them. Cooley was the head entomologist at Canyon Creek Schoolhouse laboratory. This collection would help later researchers solve questions about other tick-borne diseases. In this photo, Cooley shows off his world-class tick collection kept in jars in a huge card file cabinet. The photo was taken in Building One (which opened in 1928), not the Canyon Creek Schoolhouse laboratory, on December 3, 1946. Cooley had been developing this collection since his first days studying RMSF forty years before.

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Image: Wikimedia Commons

How do you get RMSF?

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How do you get RMSF?

Occurrence

One way of finding out how a disease is spread is by looking at where it occurs. Rocky Mountain spotted fever came to be studied in Montana’s Bitterroot Valley because the bites of the western slope’s ticks caused a particularly deadly infection, meaning that more people died. By mapping and charting where they found ticks or where people got RMSF, the researchers could find the ticks and animals they needed to study. Mapping turned up interesting insights, such as one area may have a heavily infected tick population, but an area across a stream did not. Ticks do not like to swim.

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C.M. Salisbury drew this grid map of an area of land near Mill Creek in 1922. Included were the sites of stumps, trees, and roads. The researchers could use it to keep track of where they collected ticks.

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Image: Rocky Mountain Laboratories, 961b

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Studying the life cycle of ticks provided important pieces of the RMSF puzzle. Knowing the life cycle meant that scientists could study questions such as: When did the ticks pick up the bacteria causing RMSF—was it when they were newly hatched? When they were adults? And was the infection passed on to a new generation of ticks through the eggs? The answers to these questions could be used in control efforts and in developing a new vaccine.

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Tick with eggs bunched together in bundle larger than tick

The life cycle of the tick: a fertilized female lays thousands of eggs on the ground. When they hatch as larvae, they attach to small animals and feed. Then they drop off to digest their meal, and molt (shed their old shell) to become nymphs. The first winter they spend as unfed nymphs.

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Female and Male ticks on white background

In spring, the nymphs once again attach to an animal and feed, drop to the ground, and digest their meals. This time they molt to adults, like these Rocky Mountain wood ticks, Dermacentor andersoni. They spend their second winter as unfed adults.

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Inventing the Vaccine

Dr. Roscoe Spencer came to the Canyon Creek Schoolhouse laboratory from Washington, D.C., in spring 1921, when the ticks were out. After the laboratory’s field workers collected ticks, Spencer would test the ticks for RMSF by taping them to a guinea pig; if the guinea pig came down with RMSF, the ticks were infected. But this process was messy and dangerous and slow, so he decided to grind up the ticks and inject them under the skin of the guinea pigs. Still, none of them got sick. Then he took samples from guinea pigs that were sick with RMSF. He injected the samples into guinea pigs that had been injected with ground-up ticks and into those guinea pigs that had not. The guinea pigs that had previously been injected with the ground-up ticks did not get sick.

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Roscoe Roy Spencer close up of him at desk in suit

Dr. Roscoe Roy Spencer.

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Image: National Library of Medicine, 101429481

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One day field worker George Cowan brought in a mountain goat covered with nearly a thousand engorged ticks. The researchers plucked the ticks off and decided to see what would happen when they ground them up and injected them into healthy guinea pigs. Every guinea pig got sick and died. The control group were guinea pigs that had been injected with ground-up unfed ticks; they did not get sick.

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To be sure of the results, Spencer took some unfed ticks, attached them to a sick guinea pig to feed, ground up the ticks, and injected them into healthy guinea pigs. They all died. As Lucy Salamanca dramatically wrote:

“They had proved it was the meal of blood that had turned a harmless tick into an agent of death!”
(Quote from “Tick Conquered,” Lucy Salamanca, Washington Evening Star, March 28, 1937, page F-4.) (24 kB)

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Ticks feed among the hair

Ticks feeding on guinea pig. Taken in 1931.

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Image: Office of NIH History and Stetten Museum, 1465-3

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Canyon Creek Schoolhouse Laboratory 100^th Anniversary

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