The most common tick-borne infection is Lyme disease. However, infected ticks also carry and spread numerous co-infections.
The newest Global Lyme Alliance podcast, with GLA’s Dr. Harriet Kotsoris and Dr. Mayla Hsu, discusses Lyme disease and the co-infections that are often transmitted along with the initial tick bite. Below is an excerpt. CLICK HERE to listen to the entire podcast.
Host: In this podcast we’re going to expand our discussion to include co-infecting tick-borne diseases that are often transmitted along with Lyme. I’m in our studio with Dr. Harriet Kotsoris and Dr. Mayla Hsu who are science and research officers at the Global Lyme Alliance. I’ll start off by asking, what is a tick-borne infection?
Dr. Harriet Kotsoris: A tick-borne infection is an infectious disease spread by the bite of an infected tick. The most common is Lyme disease but many others are present in the same tick bite. Depending on the location and the season, up to half of all ticks may have had more than one kind of microbe or disease producing organism that can make humans very sick. The list of microbes is expanding up to 11 or 12 at last count, but we’ll focus today on the major ones. These are called co-infections, the simultaneous infection of a host by multiple pathogenic or disease producing organisms.
There is an increasing number of ticks that are multiply infected as we just said. In a recent west European study of Ixodes ricinus ticks, very similar to the American black legged deer tick, up to 45% of those ticks were co-infected with up to five pathogens or disease producing organisms. We have a similar experience here in the United States.
Host: How many people get tick-borne infections?
Dr. Kotsoris: The Centers for Disease Control calculates about 330,000 Lyme disease cases per year but it may be even over 400,000. It’s not really understood how many of these are also infected with other microbes, which in some cases cause different illnesses that require different diagnostic tests and different treatments.
Host: What can you tell us about the ticks that spread these diseases?
Dr. Mayla Hsu: Well in the United States there are different families of ticks that may be co-infected with various pathogens. As Harriet just mentioned, the Ixodes ticks or the black-legged ticks are now in half of all United States counties. There’s another tick that is further south, known as the Lone Star and there is also an American dog tick called Dermacentor that also harbors infectious microbes.
Host: How about internationally?
Dr. Hsu: Well it seems that ticks are generally found in all temperate climate zones, so there are the Ixodes species in North America, these are also found in Europe and Asia, there are other ticks found in Africa, parts of temperate Africa, that infect humans as well as animals there, and they’re responsible for causing relapsing fevers. There are soft ticks, Ornithodoros, the Ornithodoros family of ticks, that are found in South America and Western Africa, and these too are associated with causing diseases in humans. The jury is still out in Australia. There are ticks there but it’s not known whether or not they’re correlating with human disease.
Host: What do we know about changing tick geography?
Dr. Kotsoris: It seems that in the United States, the geographic range where ticks are found is expanding and we know that with climate change the range is also changing, so for instance, it is expanding northwards into Canada where Lyme disease was never a concern, it now is starting to emerge. We can expect and see more tick-borne diseases elsewhere, also spreading in through the United States. These are now classified as emerging infections and so public health authorities are very concerned about this and tracking the emergence of more tick-borne illnesses.
Host: What are some of the emerging tick-borne diseases and again we’re going to focus only on the major ones about which the most is known.
Dr. Hsu: One of the more interesting tick-borne illnesses that has been emerging in recent years is called babesiosis. This is an illness caused by a parasite that’s very similar to malaria. It’s called Babesia, Babesia microti. This is characterized by recurrent fevers, so people get fevers that spike and then go away and then come back over and over again, chills, muscle and joint aches and pains and it can be actually fatal in rare cases. The diagnostic test for this is not a blood test looking for antibodies, rather the blood is examined under a microscope and here you can see the organism actually growing in red blood cells, so just like malaria it grows in red blood cells and you can see it in a blood smear and the treatment required for this is also very similar to anti-malaria therapies, so that’s drugs that are similar to quinine but also anti-protozoan drugs like Atovaquone, also known as Mepron, and antibiotics, azithromycin and clindamycin.
About 1,800 people were reported to have gotten babesiosis in the year 2013, and the numbers are rising so where we see Lyme disease we are also starting to see more and more Babesia, and it’s important to point out that the treatment and diagnostic for Babesia is different from that of Lyme disease, so if Lyme disease is suspected and is looked for, and treated, a person who also has Babesia will not get adequately diagnosed or treated and can continue to be ill.
Host: There are several bacterial diseases that are spread by ticks that have been getting more attention in recent years, Anaplasma and Ehrlichia.
Dr. Kotsoris: Yes, historically these started out as veterinary diseases. They were identified in the late 80s and early 1990s, after having been studied as long-standing veterinary problems. These organisms belong to a group known as the Rickettsiae, Anaplasma, Ehrlichia, and Rickettsia itself. These are what we call obligate intracellular parasites. They’re bacteria that only live inside the cells of another organism, and that’s how they affect humans. Human granulocytic anaplasmosis is what we call a gram-negative bacterium of the rickettsia family. It invades white blood cells after a tick bite by an infected tick and it travels and lodges within granulocytes or the neutophils, the white blood cells of the human being.
About one to two weeks after the bite, the patient will develop spiking fevers, headache, drop in white blood count, drop in platelet count…the platelets are responsible for clotting blood, and a rise of liver function tests indicative of an inflammation of the liver. These organisms are very smart and release a chemical substance known as a chemokine, or a cytokine, interleukin-8 that actually is an attracting chemical for white blood cells to help propagate the infection throughout the body. The diagnosis has to be made by blood smear because the comparison of acute and convalescent sera that is the development of convalescent antibodies may be too late in the game, that the patient will have been compromised medically and treatment will have been delayed. The diagnosis can also be made by something known as polymerase chain reaction and the treatment is doxycycline, 100 milligrams twice a day, similar to what’s used in acute Lyme disease and the treatment is until three days after the disappearance of the fever.
Related is something known as human monocytic ehrlichiosis. Ehrlichia and Anaplasma were used interchangeably in the past, but now they’ve been divided into separate categories because of the bacterial composition. Human granulocytic anaplasmosis is carried by the black legged deer tick, Ixodes scapularis, Ixodes pacificus on the west coast, but this vector for human monocytic ehrlichiosis is the Lone star tick, or Amblyomma americanum and Dermacentor variabilis, the American dog tick. The classic infection in the Midwest in particular is by Ehrlichia chaffeensis and Ehrlichia ewingii, more so chaffeensis. Usually peaking in July, usually affecting males older than 50 years old, and again, within a few weeks of the tick bite, the patient develops headaches, muscle aches, otherwise known as myalgias, fatigue, a drop in white blood count, a drop in platelet count, fever, gastrointestinal systems, which may lead to also respiratory insufficiency and kidney failure.
The three states most affected by Ehrlichia chaffeensis and ewingii are Oklahoma, Missouri, and Arkansas. They account for 30% of the reported cases of these bacterial species. The numbers have been reported in the low thousands over the last few years. In 2009, a third cause of human ehrlichiosis was identified in the upper Midwest. This has been known as Ehrlichia muris-like agent. Interestingly, it also exists in Eastern Europe and Asia. The detection of this pathogen or disease producing organism is by looking for the DNA, that is the genetic material, of this organism in the blood of patients. About 2.5% of Ixodes scapularis ticks are infected by this E. muris type agent. Note that this one is spread by Ixodes scapularis, the black legged deer tick, not the Lone Star tick as in human monocytic ehrlichiosis.
One of the better known bacterial infections that people read about, hear about, especially with people traveling into the Rocky Mountain area, into the Midwest, into the Southeast, is something known as Rocky Mountain Spotted Fever. This is Rickettsia rickettsia…it is spread by the American dog tick, by the Rocky Mountain wood tick, and by the brown dog tick. There are reported 14 cases per million population, peaking in April through September. Despite its name, as I said before, it’s not confined to the Rocky Mountains, it’s also found in the southeastern United States. These bacteria, after the tick bite, travel within the blood stream and lodge within endothelial cells, that’s the lining cells of small blood vessels, and elicit inflammatory changes and make the blood vessels leaky, affecting all organs infected, especially the skin and the adrenal glands. The platelets responsible for clotting are consumed and you may have kidney malfunctioning.
Patient will present with severe headaches, high fevers, a few days after the bite and a few days after that, a spotted rash on the wrists, palms, and ankles. Patient may also have abdominal pain, nausea, vomiting, and other generalized symptoms. The mortality rate can be as high as 4% and this is caused by a delay in diagnosis and treatment. The treatment is doxycycline and patients do best, and have a much lower morbidity and mortality if they’re treated within five days of being infected.
Below is the full podcast with Dr. Kotsoris and Dr. Hsu. They continue their overview of Lyme and co-infections, specifically Bartonella and the Powassan virus.
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