Global Warming Affects Increase in Lyme Disease Especially in Northeast

Global Warming Affects Increase in Lyme Disease Especially in Northeast

According to Outbreak News Today, an article by Harold W. Manter from the Laboratory of Parasitology at the University of Nebraska-Lincoln, and  affiliated zoologist, Daniel Brooks warns that humans can expect more illnesses like Lyme disease to emerge in the future, as climate change shifts habitats and brings wildlife, crops, livestock, and humans into contact with pathogens to which they are susceptible but to which they have never been exposed.

The expert admit we are losing the war against emerging pathogens and especially infectious diseases carried by ticks.

The authors explain that most Ixodes ticks spend more than 95% of their lives on or just below the ground surface digesting a blood meal, moulting, in diapause or seeking a host.

The conditions at the ground are critically important to tick survival and population explosion which has been observed by the generations of families that have lived in the Northeast.

My mother was born and raised in a small town near Sunday River Ski Resort in the western mountains of Maine. She was a tomboy and remembers spending hours in the woods and around the lakes and never seeing a single tick.

Now ticks are not only common in the western mountains of Maine, but each year the number of people diagnosed with Lyme disease continues to grow – even by CDC standards.  And the population of ticks in coastal Maine, New Hampshire and Massachusetts are far worse than ever before.

According to “Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission“, Manter and Brooks report that research conducted on Ixodes scapularis around the time of the discovery of Lyme disease, indicated that tick populations in coastal Massachusetts, USA, were only found after mild winters.  

The article at this time, I. scapularis in the northeastern United States appeared to be restricted to coastal southern New England, a zone of relatively cool summers and warm winters compared with inland sites. These observations led to the conclusion that extreme cold and heat were unsuitable for this species, limiting its distribution and affecting its population dynamics.

At the time of these observations, researchers mistakenly considered their study organism a distinct, northern species of tick that had been named I. dammini. Only later, when it was revealed that the New England ticks under study belonged to populations of a widespread species,I. scapularis, were many of the conclusions revised.

The presence of I. scapularis in much colder climates of Minnesota and Wisconsin and in much warmer climates of Georgia and South Carolina provided evidence that the species tolerated a considerably wider range of conditions.

Additionally, Changes in habitat mean animals are exposed to new parasites and pathogens. So the ticks that are feeding on the same animals, are picking up more diseases and passing them on to human hosts whether they are aware of it or not.

Certainly it is hard to miss a 106 degree fever, but even so, my grandson has been to the ER several times with fevers over 105 – one time included seizures, and the doctors did not look for any reason beyond encephalitis. Could he have Relapsing Fever?

You bet.

But when the ER doctor says everything is OK it is a lot easier to believe than that your child has a tick-borne disease.

The Royal Journal also features a study by researchers at the Cary Institute of Ecosystem Studies in Millbrook, NY, which demonstrate that in the northeastern United States, warmer spring temperatures are leading to shifts in the emergence of the blacklegged ticks that carry Lyme disease and other tick-borne pathogens. At the same time, milder weather is allowing ticks to spread into new geographic regions.

Cary Institute ecologist and co-author of the study, Dr. Richard S. Ostfeld notes, “Nearly two decades of data revealed climate warming trends correlated with earlier spring feeding by nymphal ticks, sometimes by as much as three weeks. If this persists, we will need to move Lyme Disease Awareness Month from May to April.”

Risk of tick-borne illness is shaped by complex interactions among pathogens, ticks, and host animals. Take the case of Lyme disease: blacklegged ticks acquire the bacterium that causes Lyme when they feed on small mammals that harbor Borrelia burgdorferi. Ticks seek a single blood meal at each life stage: larva, nymph, and adult. Larval ticks are only born free of the Borrelia bacteria if the parent is free.

If the parent is infected, it has been recently discovered that the larval ticks are infected too.

Tiny infected larval and nymph ticks pose the greatest threat to people because they are so small as to be almost microscopic.

Dr. Taal Levi of Oregon State University led the emergence analysis; he performed the work while a Postdoctoral Associate at the Cary Institute. Levi explains,

“Understanding when ticks are active, and at what life stage, is essential to predicting tick-borne disease spread. Pathogens that cause a lasting host infection, such as the Lyme disease bacterium, benefit from a lag between nymphal and larval feeding. The same might not be true of other pathogens, like Powassan virus, that are transmitted when larvae and nymphs feed simultaneously.”

“Results suggest that significant climate warming may reduce risk of anaplasmosis and the Powassan virus, but increase Lyme disease risk, particularly in the Upper Midwest where tick feeding patterns are likely to become more asynchronous.” 

With Ostfeld emphasizing, “Here in the Northeast, warming is already having an effect, and people need to be tick-vigilant before May, as potentially infected nymphal ticks are searching for their blood meals earlier and earlier.”

It is clear that vigilance, protection and extreme caution needs to be observed by any and all who venture outdoors in early spring, but even in the height of summer or late fall or early winter, the risk still remains.



Parham PE, Waldock J, Christophides GK, et al. Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission. Philos Trans R Soc Lond, B, Biol Sci. 2015;370(1665):20130551.

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One Response to Global Warming Affects Increase in Lyme Disease Especially in Northeast

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