Update on Lyme Disease and Other Tick-borne Diseases: An Alert for New Hampshire Clinicians

|May 20, 2014
 

New Hampshire (NH) continues to have one of the highest rates of Lyme disease in the nation, and about 60% of deer ticks sampled in NH are infected with Borrelia burgdorferi, the bacteria that causes Lyme disease.

NH Division of Public Health Services (NH DPHS) recommends:

  • Prevention of disease through use of DEET insect repellent, wearing long pants and sleeves outdoors, and daily tick checks followed by prompt removal of any ticks.

  • Diagnosis of early Lyme disease when erythema migrans is present based solely on clinical suspicion because diagnostic serologies (including immunoglobulin M [IgM]) may not yet be positive.

  • Awareness that recent reports of sudden cardiac death attributed to Lyme disease carditis highlight the importance of prompt diagnosis and treatment of Lyme disease.

  • Report all tick-borne diseases, confirmed or suspected, to the NH DPHS Bureau of Infectious Disease Control at 603-271-4496 (after hours: 1-800-852-3345, x5300).

Background

Lyme disease (Borrelia burgdorferi), babesiosis (Babesia microti and other species), anaplasmosis (Anaplasma phagocytophilum), and Powassan (POW) virus are transmitted by the bite of the deer tick (Ixodes scapularis), also known as the black-legged tick. Although these ticks have a 2-year life cycle, the greatest risk for human acquisition of tick-borne diseases is between May and August, when the aggressive nymph stage of the deer tick is active. Nymphs are very small (<2 mm) and are easy to miss unless they become engorged with blood.

Epidemiology

During the last decade, reported Lyme disease cases have increased significantly in NH. In 2013, 1,689 cases (confirmed and probable) were reported. The highest disease rates occurred in Rockingham, Strafford, and Hillsborough counties. Compared to national data from 2012 (the most recent available), the Centers for Disease Control and Prevention (CDC) reports that NH has the highest incidence rate of Lyme disease in the United States (75.9 confirmed cases per 100,000 population).

NH Lyme disease data and maps by county and town from 2006-2013 are available at http://www.dhhs.nh.gov/dphs/cdcs/lyme/publications.htm.

In 2013, 88 cases of anaplasmosis, 23 cases of babesiosis, and the first case of locally acquired POW virus infection were also reported.

The risk of Lyme disease for any individual depends on their outdoor activities and the abundance of infected ticks. Tick surveillance performed during 2007-2010 in NH counties showed that more than 50% of ticks tested in most counties were infected with the bacteria causing Lyme disease, with the exception of slightly lower rates (40%) in Belknap and Carroll and very low numbers of ticks collected in Coos County, precluding prevalence assessment. Babesia and Anaplasma have been detected in ticks in NH, although reliable prevalence data for these pathogens in ticks is not available.

Lyme Disease

Clinical Presentation: Lyme disease is caused by the bacteria Borrelia burgdorferi. The incubation period is 3-30 days after tick exposure. In approximately 60%-80% of patients, illness first manifests with a red rash that expands slowly, often with central clearing (erythema migrans or bull's-eye rash). Early systemic manifestations may include malaise, fever, headache, stiff neck, muscle and joint pains, and lymphadenopathy. At this stage, serologic testing is often negative, and treatment should be based on clinical diagnosis.

Early treatment generally leads to complete and rapid recovery and may prevent seroconversion (so that later testing is negative).

Patients who are not treated at this stage of infection may develop a variety of syndromes including aseptic meningitis, cranial neuritis, and cardiac abnormalities such as heart block or myopericarditis. Without treatment, a patient may develop chronic or intermittent episodes of arthritis or neurological symptoms weeks to years after onset.

In 2013, CDC released a report of three Lyme disease carditis cases in the northeastern United States that resulted in sudden cardiac death. Although rare, these cases highlight the importance of prompt diagnosis and treatment for Lyme disease. Healthcare providers should ask patients with suspected Lyme disease about cardiac symptoms and obtain an electrocardiogram if indicated. Healthcare providers should also ask patients with unexplained heart block about possible exposure to infected ticks. The full report on this rare clinical presentation is available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6249a1.htm.

Testing: Laboratory testing should be used to support clinical suspicion of disease based on clinical features and possible exposure to infected ticks. Within 4 weeks of infection, specific antibodies can be detected using US Food and Drug Administration (FDA)-approved two-stage serologic testing. Enzyme-linked immunosorbent assay (ELISA) is the screening test, confirmed by Western blot if positive or equivocal. A patient is considered to have positive Lyme serology either if 2 of 3 IgM bands are reactive (24, 39, 41 kDa) or if 5 of 10 IgG bands are reactive (18, 21, 28, 30, 39, 41, 45, 58, 66, 93 kDa).

An isolated positive IgM (without positive IgG) in a patient with tick exposure more than 8 weeks prior is suspicious for a false-positive test. Only laboratories with validated and FDA-approved testing methods for Lyme ELISA and confirmatory Western blot should be used for diagnosis of disease.

Treatment: The Infectious Diseases Society of America (IDSA) updated guidelines for tick-borne diseases in 2006. The IDSA guidelines were confirmed by an independent panel (recommendations published in 2010) and are the best available synthesis of the medical literature on the diagnosis and treatment of Lyme disease. The full guidelines are available at: http://cid.oxfordjournals.org/content/43/9/1089.full.pdf+html.

Antibiotic Prophylaxis: One the basis of the high prevalence of Lyme disease in NH, providers can consider prescribing single-dose doxycycline prophylaxis for patients who meet all four criteria outlined in the Lyme disease prophylaxis guidelines. Note that single-dose doxycycline is not 100% effective for prevention of Lyme disease; consequently, patients who receive this therapy should monitor themselves for the development of Lyme disease as well as other tick-borne diseases, including anaplasmosis and babesiosis. It is also a reasonable course of action to ask the patient to monitor the bite site and call back for further medical evaluation if a rash or any systemic symptoms develop. Testing the tick for tick-borne infectious agents is available in certain labs but is not recommended for guiding individual prophylaxis or treatment decisions.

Anaplasmosis

Clinical Presentation: Anaplasmosis (human granulocytic anaplasmosis, previously known as human granulocytic ehrlichiosis) is an infection of neutrophils caused by the rickettsial bacteria Anaplasma phagocytophilum. Transmitted by the deer tick, symptoms typically occur 5-21 days after the bite of an infected tick and may include fever, chills, headache, and myalgia. Some people, particularly elderly persons or those with weakened immune systems, may have a more severe illness.

Testing: Identification of the characteristic intragranulocytic inclusions on blood smear is the most rapid diagnostic method, but it requires lab expertise. Acute and convalescent antibody assays are the most sensitive diagnostic method.

Treatment: Doxycycline is the first-line therapy for anaplasmosis (see IDSA treatment guidelines). If coinfected with Lyme disease, doxycycline will treat both infections. Antibiotic therapy should not be delayed in a patient with a suggestive clinical presentation, pending the results of diagnostic testing.

Babesiosis

Clinical Presentation: Babesiosis is caused by the intraerythrocytic protozoan Babesia microti (or other Babesia species) and is transmitted by the deer tick. Although most people infected with Babesia are asymptomatic, some people experience fever, chills, sweats, myalgia, arthralgias, anorexia, nausea, vomiting, and/or fatigue within 1-4 weeks after infection. Severe and fatal cases most often occur in patients who are older or have a weakened immune system, particularly those without a spleen. Rare cases of relapsing disease have been reported.

Testing: Diagnosis is based on identification of Babesia parasites in a blood smear or by polymerase chain reaction amplification of babesial DNA.

Treatment: Babesiosis can be successfully treated with antimicrobial therapy (see IDSA treatment guidelines).

POW Virus Infection

Clinical Presentation: POW virus is an RNA virus of the genus Flavivirus with an incubation period of 7-30 days after the bite of an infected tick. Although most infections are subclinical, symptoms may include fever, headache, vomiting, and generalized weakness that can progress to meningoencephalitis.

Testing: Cerebrospinal fluid findings include normal or mildly elevated protein, normal glucose concentration, and lymphocytic pleocytosis <500 white blood cells/mm3 with granulocytic predominance. Brain magnetic resonance imaging is superior to computed tomography imaging and reveals changes consistent with microvascular ischemia or demyelinating disease in the parietal or temporal lobes. Electroencephalography shows generalized slow wave activity.

Diagnosis can be made by the detection of POW virus-specific IgM antibody in serum or cerebrospinal fluid combined with a consistent clinical presentation. At this time, POW virus testing is not commercially available but can be arranged through the NH Public Health Laboratories.

Treatment: Treatment is supportive.

Reporting Tick-borne Diseases

Clinicians should report suspected and confirmed cases of Lyme disease, anaplasmosis, babesiosis, and Powassan virus infection to the NH DPHS Bureau of Infectious Disease Control at 1-603-271-4496 (after hours, 1-800-852-3345, ext. 5300). When filling out the Lyme disease case report form, it is important to record the date of symptom onset because this information is used to determine whether a case meets the CDC case definition for surveillance. The most recent Lyme disease case report form is available at: http://www.dhhs.nh.gov/dphs/cdcs/documents/lymediseasereport.pdf.

Prevention Messages for Patients

  • Avoid tick-infested areas when possible and stay on the path when hiking to avoid brush.

  • Wear light-colored clothing that covers arms and legs so ticks can be more easily seen.

  • Tuck pants into socks before going into wooded or grassy areas.

  • Apply tick repellent (20%-30% DEET) to exposed skin. Other repellent options may be found here: http://www.epa.gov/pesticides/insect/choose.htm.

  • Outdoor workers in NH are at particular risk of tick-borne diseases, and they should be reminded about methods of prevention.

  • Do daily tick checks to look for ticks on the body, especially warm places like behind the knees, the groin, and the back and neck.

  • Remove ticks promptly using tweezers. Tick removal within 24-36 hours of attachment can prevent disease.

  • Monitor for signs and symptoms of tick-borne diseases for 30 days after a tick bite. Patients should contact their healthcare provider if symptoms develop.

For any questions regarding the contents of this message, please contact NH DHHS, DPHS, Bureau of Infectious Disease Control at 1-603-271-4496 (after hours, 1-800-852-3345, ext. 5300).

 
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