Guest essay by Eric Worrall
Zoonotic disease researcher Katharine Walter has claimed that climate is causing a massive rise in human cases of potentially debilitating Lyme Disease. But there are a few problems with this theory.
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Deer tick invasion
Encounters with ticks didn’t always cast a dark shadow over North American summers. Cases of Lyme disease first appeared in 1976 in the woodsy suburb of Lyme, Connecticut. At that time, deer ticks were found only in a hotbed encircling Long Island Sound, along with a small area in Wisconsin.
Since the 1970s, deer ticks have rapidly extended their reach north, west, and south. The most recent map shows that deer ticks now roam throughout the eastern coastal states, from Maine to Florida, and across the Midwest. They are now established in 45 percent of US counties. That means the deer tick has more than doubled its reach in the 20 years since the previous map was published.
The spread of Lyme disease has closely followed the spread of the forest nymphs. Lyme disease is now the most common disease transmitted by a vector — a mosquito, tick, or other bug — in United States. More than 30,000 cases are reported each year, and the Centers for Disease Control and Prevention estimates that 10 times as many Americans develop the disease.
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Ticks spend the majority of their lives on the forest floor. They are vulnerable to changing local climates and death by freezing, drowning, or desiccation. Warmer winters and longer summers let more ticks survive and thrive further north each year. Warmer temperatures quicken the tick life cycle, too. Tick eggs hatch sooner and ticks spend more time questing for blood, and so are increasingly likely to feast on a human and pass on a disease-causing pathogen. Because more ticks survive and mature more quickly, diseases can be transmitted faster.
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Read more: https://www.statnews.com/2016/07/01/lyme-disease-climate-change/
What happened in the early 1970s, which might have caused a sudden rise in the rate of dangerous insect borne disease infections?
In 1962, Rachel Carson published the book Silent Spring. It cataloged the environmental impacts of widespread DDT spraying in the United States and questioned the logic of releasing large amounts of potentially dangerous chemicals into the environment without understanding their effects on the environment or human health. The book claimed that DDT and other pesticides had been shown to cause cancer and that their agricultural use was a threat to wildlife, particularly birds. Its publication was a seminal event for the environmental movement and resulted in a large public outcry that eventually led, in 1972, to a ban on DDT’s agricultural use in the United States. A worldwide ban on agricultural use was formalized under the Stockholm Convention on Persistent Organic Pollutants, but its limited and still-controversial use in disease vector control continues, because of its effectiveness in reducing malarial infections, balanced by environmental and other health concerns.
Read more: https://en.wikipedia.org/wiki/DDT#United_States_ban
The timing fits. DDT was banned because of fears about its long term persistence in the environment – its ability to spread and continue killing insects, well beyond the location where it was originally sprayed.
But there are other issues which might have contributed to the “rise” in Lyme disease rates.
Nobody actually knows how many people are infected every year with Lyme disease. Estimates are statistical models, based on the number of people who are diagnosed, which the CDC admits are only a tiny fraction of the number of people they believe are actually infected. The bacterium which causes Lyme wasn’t identified until 1982, when it was described by Willy Burgdorfer. Given the variability of Lyme disease symptoms, any diagnosis prior to 1982 must be considered circumstantial at best. Changes to the quality of diagnosis, of which there have been a number in recent years, could potentially have a significant impact on the number of reported cases.
Each year, approximately 30,000 cases of Lyme disease are reported to CDC by state health departments and the District of Columbia. However, this number does not reflect every case of Lyme disease that is diagnosed in the United States every year.
Surveillance systems provide vital information but they do not capture every illness. Because only a fraction of illnesses are reported, researchers need to estimate the total burden of illness to set public health goals, allocate resources, and measure the economic impact of disease. CDC uses the best data available and makes reasonable adjustments—based on related data, previous study results, and common assumptions—to account for missing pieces of information.
… the number of people diagnosed with Lyme disease based on medical claims information from a large insurance database. In this study, researchers estimated that 329,000 (range 296,000–376,000) cases of Lyme disease occur annually in the United States.
Read more: http://www.cdc.gov/lyme/stats/humancases.html
Changes to land management may have also contributed. The ticks which transmit Lyme disease to humans hide in leaf litter. During much of the 20th century, controlled burning was unfashionable – fire departments sought to suppress fires, rather than burn off excess fuel. Policies have varied in different places at different times, so it is difficult to match management policies to tick prevalence, but controlled burning when it occurred likely had a massive impact on the tick lifecycle, by burning the leaf litter in which they hide.
It is not impossible that climate has influenced the distribution of Lyme disease. However, concluding that climate has caused a rise in Lyme disease infections in US and Canadian forests seems dubious, without considering the likely significant impact of other contributing factors, or the very real possibility that much of the apparent rise is a statistical artefact, caused by poor historical diagnosis and reporting.
Update (EW) – Katharine also mentions the rapid rise in deer population as a contributing factor
In part, ticks are following the spread of one of their favorite sources of blood: deer. As deer populations exploded over the last sixty years, thanks to strict hunting laws and the largely predator-free and deer-friendly landscapes in New England and the Midwest, deer ticks followed. However, the steady crawl of ticks north into Canada can’t be explained by deer alone.
I think it makes more sense that the transportation of tick-infested livestock (and pets) all over the US, which is much easier to do these days than it was a few decades ago, has a larger role to play in the spread of Lyme and other tick-borne diseases than previously acknowledged.
Expanding deer populations certainly play a role , but livestock (particularly sheep) are frequently moved around the country, to places without a sizeable native deer population. .
Nothing to do with climate change.
Obviously the return of forest cover is the main promoter of deer retreats and shelter. The forests have exploded with the deer in tow, absorbing CO2 and breeding ticks in consequence.
It seems the use of DDT isn’t going to help anything. The burning, yes, maybe, but the deer population is probably the biggest issue. They are a road hazard and health threat. It is unnatural.
The best long term solution is to inoculate the deer and people. It works with wild foxes and rabies.
I remember several cows dying from Red Water Disease in on a neighbours Perthshire farm when I was a boy.
Babesiosis (Redwater fever)
Deer have become ‘rats with hooves’, especially white-tailed deer.
OK, all you tin foil hat fans. It seems that Lyme CT, where the disease suddenly appeared in the ’70’s, is the ferry terminus for the Plum Island ferry. Did someone carry something home from work one night?
You can buy books on the topic. Some argue that Lyme escaped from military research at Plum Island. Others argue that it was weaponized and then escaped. I have not read them.
I have a son who is twenty-one and who contracted Lyme when he was ten years old. We saw an army of doctors over the years and he was diagnosed with Lyme when he was 16. He has been under treatment for the last five years and has improved considerably. He is able to take two college courses per semester.
Reading the posts above, I see that some people are well informed about Lyme and have some useful things to say. Right off the bat, I want everyone to know that the CDC changed its estimate of new cases from 30,000 annually to 300,000 and made that change about two years ago. Lyme is endemic from Virginia north and west to the middle of Ohio. Its range has spread rapidly and continues to spread. To some degree, it is everywhere. You can get it in Arizona or Florida but the risk is really great in the area I mentioned above. For those of you who are skeptics about Lyme, find a large animal veterinarian near your place of residence. They will tell you off the top of their heads how many horses or other large animals have Lyme in the county or city. Vets have a superior test for Lyme but it is not approved for humans.
As regards the climate change hypothesis, there is no reason to believe it. The spread of Lyme has been caused by two things (1) the huge increases in the number of deer and (2) total breakdown of barriers between humans and deer. In Virginia, deer are everywhere except right downtown. They are in the near suburbs and the far suburbs. I have gone out my front door at three in the morning and been challenged by a deer who was happily eating acorns. People think they are cute.
To keep your yard free of ticks you have to keep out the deer and you have to make sure that the leaves underneath your shrubs are removed annually. If the fellow next door does not do the same, then you are hardly better off. Eradicating Lyme from the suburbs requires eradicating the deer.
The nymph stage of the deer tick is the most dangerous because it can be darn near microscopic yet it can transmit Lyme and several other bacterial infections that often accompany Lyme. When you check yourself for ticks use a magnifying glass.
The symptoms caused by Lyme and the other tick born bacteria can be horrendous. I know first hand because my family and I have been on a five year odyssey through clinics and medical facilities seeking treatment for my son. Some physicians, LLMDs (Lyme literate MDs), have developed various regimens that are effective in eliminating the bacteria. Here is the catch. The effective treatments are really harsh. Many people, including my son, could not handle them. So, he is taking a gentler but longer road. He suffered greatly with Lyme. He had severe arthritis, some wasting, some nervous system complaints, and his immune system is a mess. But progress is being made. I have seen far worse. I have seen adults who had been vital confined to a wheel chair for years and some of them have little hope of improving. A young man who suffers from Lyme and his parents came over recently to borrow some medical equipment. He too is 21 but about 5′ 6″ and 90 pounds. His fingers were the thinnest I have seen. Looking at his parents, he should have been 6′ 1″ and 200 pounds.
Be careful. Remember: Virginia north and west to central Ohio. Lyme is everywhere but not like that corridor. Senator Kelly Ayotte has introduced legislation to increase government resources dedicated to Lyme disease. Please support her efforts if you are so inclined.
Read a book named “Lab 257” and you might just come to a different cause for lyme disease.
Ground zero was Plum Island where a bio-weapons lab operated. At first their security was first rate but over time due to budget cuts and the “do we really need that much security?” attitude deer and other animals started visiting the island and gong back to the mainland.
They had a tick colony but had to destroy it because, ahem, they “lost containment”. That and all the other nonsense in and around it will shock you (maybe not, depending on how jaded you are).
All circumstantial but an interesting idea as to where it came from.