How Ticks Make You Sick

Ticks are as ubiquitous as any creature on earth. There are 907 species of ticks living in a vast range of climates, from subarctic to equatorial to arctic environments, and from deserts to rainforests. They feed on mammals, birds and reptiles. When attached to birds they can survive submersion under water. They feed only on blood and can live longer without food or water than any other creature.  They stay attached to their prey for up to 2-3 weeks, feeding slowly, with the largest portion of their meal at the end of their stay. They usually molt three times to become adults, acquiring bacteria, viruses, protozoa from one feed and transmitting to the next. As they can survive the winter, it is possible that  they can have a lifespan of up to 7 years, as far as we know. Ticks harbor a complexity of organisms we are only beginning to understand. The implications of their effect on humans makes the specter of Lyme disease grow pale in comparison.

George P. Dempsey, MD

The complex salivary glands in ticks enable them to be, as one researcher called them, “supreme pharmacologists,” by secreting hundreds of molecules of diverse biological activity. For example,  anti-hemostatic  molecules thin the blood so that they can enjoy a stable pool to feed upon within the deeper layer of our skin. Anesthetic molecules numb the site of entry so that we are completely unaware of a bite.  Anti-inflammatory molecules disable our early immune response preventing rejection of the tick,  as it would ordinarily do to a foreign object embedded in our skin such as a splinter. Immunomodulatory molecules engage with higher levels of our immune response so that the organisms within the tick can be safely transported to their new host. Toxins, causing illnesses such as Tick Paralysis, can be excreted. The glands also maintain water regulation for the body of the tick to resist the harsh changes that they are known to survive in. Finally, they are involved in a lesser known area of endocrinology in ticks. These are the hormones which regulate growth and sex.

In the past we have paid a lot of attention to the deer tick,  Ixodes scapularis, or black legged tick. Far  more common now on Long Island is the Lone Star tick, or Amblyomma  americanum.  Its habitat extends from mid-Texas to the Midwest, and all the way up the East Coast. This tick is far more aggressive at all stages and results in the majority of tick bites in our area. One needs magnification to distinguish an Amblyomma  nymph from an Ixodes nymph, unless you are experienced and have good eyes! We have been so focused on Ixodes scapularis and Lyme disease that we may be “missing the boat” in many ways. To be clear, the Lone Star tick does not carry Lyme disease. This has been shown in several types of experiments. The most convincing finding was that Borrelia burgdorfi (which causes Lyme disease) cannot survive in the saliva of a Lone Star tick, as it does in a Deer tick.

The Lone Star tick does have more than its share of potentially deadly diseases. The literature is somewhat scant, but several of the newest tick diseases have been attributed to Amblyomma americanum.  Besides Tularemia, Erhlichiosis, STARI (relapsing  fever), and the alpha-gal meat allergy, there are many other diseases found in other  regions of the US that can be attributed to the Lone Star Tick. Rickettsia parkeri imitates Rocky Mountain spotted fever in the South. In 2012, in the Midwest, the Heartland Virus was newly described as a cousin of Hanta Virus with several deaths attributed to it. While some of new diseases seem rare and regionally restricted, the high attack rate of the Lone Star tick may make these diseases important in populated areas.  Migration of birds, pets and people make spread quite possible.    

Viruses need further explanation now.  They are underappreciated in their unique ability to get into our body and affect our DNA and gene expression. This is much more profound than any bacterium or protozoa.  Antibiotics have no effect. Our immune system alone  fights viruses and generally does it well. But there are plenty of ways viruses get around it (e.g. herpes, HIV, Hepatitis C) or cause “friendly fire” by activating a prolonged inflammation after the initial infection, causing arthritis, malaise and many other diseases. Our understanding of genetics and the human genome will open the way to a deeper understanding of how viruses influence us, and certainly reveal many other mechanisms of disease we’ve never even thought of.

This brings us to another profound thought: ticks may play an important role in evolution. Just as bees pollinate flowers, ticks “pollinate” animals, allowing the exchange of genetic information (viral DNA) between higher, more complex organisms in the animal kingdom to help biodiversity. No other creature does this. Viruses mutate faster than any other form of life, so this makes sense. 

There are many ways a tick can make you sick. Individually they can carry multiple infections, you can have multiple bites you were unaware of, and your immune system is unique to you. It’s important to keep this in mind when you don’t feel well and don’t understand why the Lyme test is negative. Don’t put all your eggs in the “Lyme basket,” but be open to other diagnoses. Ticks are very complex and so are humans. Fortunately, we are at a wondrous age where technology is helping us understand these vast complexities.