Signs of Fall 11: Lyme Disease and Vaccines

Photo by D. Sillman

In June 2017 I wrote my annual blog about black-legged ticks and Lyme disease. I won’t talk about the tick life cycle again until next spring, but I do have some updates and new perspectives about the disease and also about the ticks that transmit it.

First of all, Pennsylvania is once again leading the nation in cases of human Lyme disease. The final numbers are not yet in for 2017, but the Center for Disease Control (CDC) recorded 12,092 reported cases of human Lyme disease in Pennsylvania for 2016, and these data maintained the five year pattern of 25 to 33% yearly increases in human cases of Lyme in the state. A recent publication by the CDC further noted that the reported cases of Lyme probably represent only 10% of the actual cases. They calculate that there are over 300,000 cases of human Lyme disease in the United States each year and about a third of these cases are in Pennsylvania! Lyme is now the fastest growing, vector-transmitted disease in the United States!

I mentioned in my June 2016 post that the spirochete bacterium that causes Lyme disease (Borrelia burgdoferi) also infects dogs and can cause debilitating (limb paralysis) and occasionally fatal (kidney failure) reactions. The good news for dogs is that there is a vaccine that effectively generates immunological protection against B. burgdoferi infections and also reduces the severity of the Lyme syndrome if an infection does get established. The very puzzling part of any discussion about this dog vaccine, though, is the realization that there is not a human, anti-Lyme vaccine currently available to help control this growing epidemic of human Lyme disease.  A CDC discussion site actually reported cases of desperate people convincing their veterinarians to give them injections of the dog anti-Lyme vaccine!

This vaccine discussion begin to get even more absurd when you realize that there exists not just one but two human anti-Lyme vaccines! One of these was actually available to the public about twenty years ago and the other one passed through clinical trials but was never released for general distribution. What happened to these vaccines, and why can we not use them?

The answer to that question lies in outside the realm of science. A consideration of the history of vaccines may help us understand our current dilemma.

Edward Jenner by James Northcote, National Portrait Gallery, Wikimedia Commons

Most medical historians start their discussion of vaccines in the last decade of the Eighteenth Century with Edward Jenner and his cow pox inoculations. Jenner noticed that milk maids, who were exposed to the relatively mild virus that causes cox pox, were then immune to the extremely serious and frequently lethal virus that causes small pox. Small pox had been a scourge of humanity since the invention of agriculture (10,000 + years!), and it is thought to have been an animal virus that escaped into human populations from either cattle or camels. In Eighteenth Century Europe 400,000 people died every year from small pox!

Jenner’s observation was an incredibly insightful one, but the idea of vaccination (even though Jenner was the first one to coin the term) had existed for a much longer period of time. Healthy individuals possibly for centuries in India and China had undergone a process called “variolation” to protect them from small pox. Variolation involved removal of some of the puss from a fresh small pox lesion and its transfer, subcutaneously, to a healthy individual. The inoculated individual, then, typically, experienced a mild immune reaction (fever, aches, etc.) but developed an immunity to the small pox virus. The transfer of fresh fluids from a small pox patient, though, could also sometimes transfer the actual virus causing the recipient of the inoculation to actually develop small pox. It was, then, a fairly dangerous procedure. In spite of that, variolation was widely practiced across Europe throughout the Eighteenth Century and many stories of aristocratic families inoculating their offspring added greatly to the acceptance of and desire to undergo the procedure.

In 1796, Edward Jenner utilized puss from a pustule on a cow (whose name, by the way, was “Blossom”) to inoculate a young boy. The boy experienced a period of fever and immune reaction symptoms but was, then, immune to small pox. The weaker, cow pox virus “tricked” the human immune system to make the immunological proteins and cells that could destroy the small pox virus. It was a great victory for both medicine and science and subsequently saved countless numbers of human lives, but not everyone was pleased with the idea of vaccination!

Jenner among his patients. Wellcome Images, Wikimedia Commons

Satirical cartoons from early Nineteenth Century publications show people developing legs and heads of cows after receiving Jenner’s inoculation. The cross-species nature of the inoculant, and the “un-natural” process of the inoculum transfer, caused many groups to forcefully resist receiving the vaccine. People rioted, attacked the inoculators and were arrested and jailed as a consequence. Jenner, although eventually lauded by many in his professional and social spheres, was the object of widespread ridicule and the recipient of constant death threats. Something deep and primal had been awakened in the superstitious minds of people, and they focused on vaccination as a fundamental invasion of their bodies by forces of government and science.

Sadly to say, this superstitious reaction to vaccination has not gone away. Small pox, as we should all be grateful, is extinct and the virus now only exists in two extremely secure medical repositories. Almost every other vaccine since, though, has had to face the loud and emotional (and often incredibly ignorant) criticism of the anti-vaccinators. Here is a link to very readable history of the anti-vaccine movements that was published by the College of Physicians in Philadelphia.

Anyway, this was the buzz saw that the human anti-Lyme vaccine ran into. A small group of people claimed that the vaccine caused paralysis (no clinical evidence supported this). This group threatened legal action against the pharmaceutical company that had released the vaccine and also mounted an extremely effective public relations campaign against the vaccine. Under the weight of these attacks and under threat of skyrocketing legal costs, the company stopped manufacturing the vaccine, and the second company decided never to release their vaccine. In the 1990’s when the vaccine was initially released the number of Lyme cases in the United States were much lower than today, so there was little economic incentive for the pharmaceutical company to continue to make the vaccine. Possibly, as the number of Lyme cases per year increase, someone might be brave enough to re-release one of the vaccines.

Photo by K. Laubenstein, USFWS, Public Domain

One last thing about black legged ticks, B. burgdoferi, and the mice that are the lynchpins in their infectious cycles: in a study published this summer in the Proceedings of the Royal Society B the presence of active mice predators (foxes, martens, weasels etc.) did not significantly reduce local populations of mice. The presence of these predators, though, did reduce the number of ticks each mouse had on them (a 90 to 95% reduction!) and also reduced the number of ticks that were carrying the B. burgdoferi bacteria (a 96% reduction!). Speculating on these findings, the study’s lead researcher, Dr. Tim Hofmeester, felt that the presence of the predators curtailed the movements of the mice and acted to disrupt the proliferation and spread of the ticks and, possibly, their intra-specific exchanges of the bacteria!

Stop Lyme disease by adding foxes and weasels (and how about coyotes?) to our fields and woods and neighborhoods? Works for me!