Spring is crawling with critter-borne infections
By Jessica Berthold
Doctors could learn a thing or two from country music singer Brad Paisley, whose song “Ticks” discusses walking in the woods with a sweetheart and then checking her body thoroughly for the blood-sucking parasites, said Larry M. Baddour, FACP, at an Internal Medicine 2007 session on insect- and animal-borne diseases.
Larry M. Baddour, FACP
“(Paisley) recognizes the epidemiology of many of these infections, like the risk associated with rural and suburban areas and the fact that the ticks can embed themselves in sections of the body where they are difficult to find,” Dr. Baddour said.
With warm weather—and tick season—upon us, the good news is that physicians now are spotting infections like Lyme disease earlier in their progression, he said. Still, doctors must be vigilant, as different critter-borne illnesses can manifest with similar symptoms—such as Lyme disease and its mimic, Southern Tick-Associated Rash Illness, or STAR I.
Symptoms of Lyme disease, the most common tick-borne infection in North America, usually start appearing a week or two after the bite, Dr. Baddour said. Erythema migrans is the most common early manifestation, occurring with a single lesion in 75%-80% of cases. About 60% of those who don’t get treatment develop arthritis and about 10% develop neurologic complaints, the most common being facial nerve palsy, he said. People in the Northeast and Midwest regions are most susceptible to the infection.
While it’s known that Lyme disease is caused by Borrelia burgdorferi that can be detected in serum, it’s not known what causes STAR I. The latter also produces a lesion that looks like E migrans, but isn’t. STAR I appears earlier in the year than Lyme Disease, is less likely to be symptomatic, has a shorter incubation period, and is even less likely to manifest with multiple skin lesions. “We call it ‘Lyme disease lite,'” Dr. Baddour said.
Babesiosis is another mimicking disease, marked by fever, chills and toxicity similar to symptoms of malaria. To help differentiate it, doctors should ask patients if they’ve recently visited East Coast islands like Nantucket, Mass. or Shelter Island, N.Y. Diagnosed by blood sample, the disease is treated with a combination of drugs.
Locally acquired malaria is rare in the U.S, but there are about 1,000-1,500 imported malaria cases each year. Preventing malaria in travelers is complicated and must be done on a case-by-case basis, taking into account where the patient is going and the kind of drugs he or she is already on, Dr. Baddour said.
West Nile Virus, which is spread largely through mosquitoes that transmit it from birds, is asymptomatic in about 80% of cases, Dr. Baddour said, but about 20% of those with the virus develop West Nile fever and its accompanying flu-like symptoms, according to the CDC. Severe forms of the disease include meningitis and encephalitis, and are fairly rare—occurring in about 1 in 150 persons, the CDC said.
Plague is still around, Dr. Baddour said. Thirteen human cases were reported in 2006—all in the U.S. West and Southwest regions—with two of them fatal. Spread mainly by infected fleas on wild rodents, rabbits or pets, all three of the plagues’ syndromes can cause fever and gram-negative sepsis. Bubonic is the most common form.
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