This highly magnified electron microscopy (SEM) image depicts a population of spirochete bacteria, above a culture of cottontail rabbit epithelial cells.
Zoom in / This highly magnified electron microscopy (SEM) image depicts a population of spirochete bacteria, above a culture of cottontail rabbit epithelial cells.

A California man is the first person in the western US to have a confirmed infection with a strange bacterium that has lurked in the area for more than two decades — and researchers fear the pathogen may finally be emerging there.

bacteria Borrelia MiyamotoiIt is a corkscrew-shaped spirochete spread by black-legged ticks and causes a rare disease called hard tick relapsing fever. H. pylori is a relative of the most famous Borrelia burgdorferi spiralAnd The bacteria that cause Lyme disease. but B. Miyamotoi It has several notable differences from its cousin, including its inconspicuous spread.

While Lyme disease was first reported in 1975 in the United States and B. burgdorferi It was first identified in 1982. P Miyamotoi It was only identified in ticks in 1995 in Japan. But once it was discovered, it was soon found in many other places, including Europe and many parts of North America. Ticks collected in California as early as 2000 have been found to carry the new spirochetes, for example. However, the first cases of the disease are caused by it P Miyamotoi In the United States it was only confirmed for the first time in 2013 in the Northeast. To date, no confirmed cases have been reported in the western part of the country, although the bacteria are common in adult black-legged ticks (Peacemaker prevails) is similar to B. burgdorferiLyme disease spirochetes.

Shadow disease

B. Miyamotoi The disease, or tick reflex fever, is a difficult infection to identify. It is often characterized by fever that comes and goes, along with indescribable fatigue, chills, and aches and pains. In severe cases, which often affect people with weakened immune systems, the disease can progress to meningoencephalitis, an inflammation of the brain and surrounding tissues. But in many cases, the disease heals on its own.

On clinical tests, affected people tend to show low levels of white blood cells and platelets (leukopenia and thrombocytopenia), as well as elevated liver enzymes and excess protein in their urine. But there are no simple tests to confirm the disease. Borrelia Bacteria share many proteins, so a search for antibodies against the microbe will readily pick up other related bacteria, including the bacteria that causes Lyme disease. The only way to determine a P Miyamotoi Infection is the direct investigation of fragments of the bacteria’s genetic sequence in a person’s blood or cerebrospinal fluid, which few laboratories do.

If infection is confirmed, there is no good treatment. With so few clearly identified cases, the researchers were unable to conduct clinical trials. But, so far, a two-week course of doxycycline or amoxicillin appears to do the trick in most cases, with intravenous antibiotic treatments used in severe cases. However, a small number of people may experience what is called a Jarisch-Herxheimer reaction, which occurs in the first few hours or days of antibiotic treatment for a spirochete infection. Not only that P Miyamotoi disease and Lyme disease, but also syphilis, leptospirosis, and others. The reaction is characterized by fever, chills, nausea, vomiting, headache, rapid heart rate, hypotension, hyperventilation, flushing, and pain. It’s not clear exactly what causes this, but researchers hypothesize that when spirochetes begin to die, they release toxins that trigger an acute inflammatory response. The reaction often resolves on its own within a day or so, but it can become life-threatening for some, and patients need to be monitored closely.

Difficult diagnosis

In the case of the California man, published Wednesday in the journal Emerging Infectious Diseases, a four-week course of doxycycline seemed to work without any severe treatment interaction. The man, who fell ill in late 2021, had previously been diagnosed with multiple sclerosis and was being treated with a monoclonal antibody that left him immunocompromised. Starting in October, he started noticing a day’s rise in temperature about every 10 to 14 days. The fever was accompanied by night sweats, vision changes, and nausea. Months later, he went to a neurological clinic in December, but the doctors couldn’t find any problems so they sent him home, telling him to come back if the fever returned.

I did. Subsequent clinical tests showed he had elevated inflammatory markers and low platelets — although doctors still don’t know why. He tested negative for common bacteria, viruses and fungi. But, given the other clinical signs, the doctors still suspected an infection of some kind and ordered an advanced test that sequenced the cell-free microbial DNA of his blood, looking for pathogens that could explain his symptoms. The results showed a 100 percent match with P Miyamotoispecifically a close match with the P Miyamotoi strain isolated in a tick in the county where the man lives, Marin County. The Centers for Disease Control and Prevention confirmed this finding. Although the man did not recall being bitten by a tick, he reported doing outdoor activities near his home, such as swimming and hiking.

carried by ticks

Previous studies estimated that 0.8 percent of adult black ticks and 1.4 percent of nymphs carried P Miyamotoi In California, despite its uneven distribution. For comparison, the estimated prevalence rate for Lyme causative agent B. burgdorferi In California, the incidence of ticks is 0.7 percent in adults and 3.3 percent in nymphs.

But, while Lyme-causing spirochetes are known to have vertebrate reservoirs, such as mice, from which the bacteria first infect larval ticks, P Miyamotoi It doesn’t have an obvious vertebrate tank – and it doesn’t seem like it needs one. In infected female ticks, P Miyamotoi It is transmitted to the eggs, which means that the tick larva hatches with the infection. (Rarely, larval black-legged ticks bite humans.)

Given prevalence estimates, infection is probably rare, and the authors conclude that because infection is difficult to confirm, it may not be as rare as we think. However, our study indicates that P Miyamotoi is an emerging human pathogen in California,” they wrote, and clinicians should suspect any recurring unexplained fevers.

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