Ticks, already notorious as carriers of disease, get another black mark tomorrow New England Journal of Medicine . A document, it indicates that ticks can infect people with a new, potentially life-threatening disease. The culprit is a bacterium known as Ehrlichia ewingii , which until now was thought to infect only dogs.
The microbe is a relative of E. chaffeensis , humans can also contract ticks. Attacking his victim white blood cells E. chaffeensis causes a disease called ehrlichiosis, characterized by fever, malaise, muscle pain, and, if untreated, organ failure. Ehrlichiosis was first reported in 1986; Since then, hundreds of cases have arisen in the US, with the highest incidence in Missouri.
Because his flu symptoms are much like those of many other diseases, ehrlichiosis is difficult to diagnose. Doctors can get an early indication of the number of white blood cells from patients' blood, said Gregory Storch, professor of pediatrics at Washington University in St. Louis, but to confirm their diagnoses, clinicians use the polymerase chain reaction to search for the patient's blood for a typical ribosomal gene from several Ehrlichia bacteria.
Between 1994 and 1998, the team Storch ran this test, and another more specific that detects only E. chaffeensis of 413 people suspected of ehrlichiosis. Sixty patients were tested positive for the general test, but of those, only 56 were confirmed to have E. chaffeensis . Suspect that the other four have dealt a new Ehrlichia species, the researchers sequenced the bacterial gene in the blood and compared to a database containing sequences from known infectious bacteria. To their surprise, the "new" species had already been identified - by veterinarians. Called E. ewingii , it usually infects dogs that have been bitten by ticks. "This is the first time anyone has seen this in humans," says Storch.
The symptoms of E. ewingii infection seems indistinguishable from E. chaffeensis , but many other things about the disease is unknown. "it might be unusual or common," says Storch, "and it could be carried by deer ticks and Lone Star ticks." Three of the four patients had weakened immune systems - may have contributed to E. ewingii foothold - but the fourth was healthy before
"They opened a new chapter in history of pathogens by ticks, "said Jesse Goodman doctor from the University of Minnesota .. the next step is to try to develop E. ewingii in the laboratory and perhaps learn how to prevent ehrlichiosis, he said. "We'll keep working on medical aspects," says Storch, "perhaps in collaboration with veterinarians."
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