Disease Control Bulletin: May 2002

Contents

disease control bulletin

Vectorborne Diseases in Vermont

West Nile virus, which was introduced into the northeastern United States in 1999, is one of several vectorborne diseases present or likely to be present in Vermont. Last year, an article in the CDC’s Morbidity and Mortality Weekly Report1 documented a case of locally acquired Powassan encephalitis in a Vermont resident in 1999. Infection with this tickborne flavivirus was identified when the patient was tested for other arbovirus infections found in the northeast, after testing for West Nile virus infection was negative. In the summer of 2000 a hermit thrush found dead in Vermont tested positive for West Nile virus; although it is likely that West Nile is in Vermont, no surveillance indicators (e.g., dead birds, mosquitoes) tested positive for West Nile virus in Ver-mont in 2001. The Vermont departments of Health; Agriculture; Forests, Parks and Recreation; and Fish and Wildlife are working to better understand the distribution of vectorborne diseases, and the vectors that transmit them, in Vermont.

Tickborne Illnesses

While the risk of contracting Lyme disease in Vermont remains low, the vector and the causative organism are present in Vermont. (See article on back page.) Vermont has some statewide surveillance data on tick species and their distribution. For the past three years, the Department of Forests, Parks and Recreation has collaborated with the Department of Fish and Wildlife to collect data on the number and species of ticks found on deer checked at 18 stations during the opening weekend of rifle season. In both 2000 and 2001, deer or moose ticks were found on 11 percent of the deer examined (45 of 412 deer in 2000 and 56 of 510 deer in 2001). Deer ticks (Ixodes scapularis), which transmit Lyme disease bacterium (Borrelia burgdorferi) to humans in the northeastern United States, have been found in northern as well as southern parts of Vermont.

In an effort to expand our knowledge of tick vector species in Vermont, the departments of Health; Agriculture; and Forests, Parks and Recreation are collaborating on a project to collect ticks from selected veterinarians in every county beginning this spring. Veterinarians will retrieve ticks they find on their canine patients and submit them to the Department of Agriculture and the Department of Forests, Parks and Recreation’s Forest Biology Laboratory, where trained personnel will identify the ticks. Other sources of historical tick data, such as the Department of Health Laboratory and collections at the University of Vermont, will also be compiled. These efforts will be useful in assessing the risk of transmission of tickborne illnesses, including Lyme disease and Powassan encephalitis, to people in Vermont.

West Nile Virus

West Nile virus has become established in the northeastern United States, and is likely to be in Vermont. The presence of West Nile virus was documented in 27 states plus the District of Columbia in 2001 (compared to four states in 1999). Canada also detected the virus last year, with 121 birds in southeast Ontario testing positive for the virus. No human disease was reported in Canada. New Hampshire reported 83 positive birds and three positive mosquito pools in the southern half of the state during the 2001 season. Two horses from Rockingham County, NH were confirmed to have West Nile virus in 2001. Onset of illness in both horses was in November, indicating a longer transmission season than previously thought in the Northeast.

WNV Case-Patient Demographic & Mortality United States,1999–2001
  1999-2000 2001*
Number 83 66
Age (years) Median 65 68
Age (years) Range 5–90 19–90
Males 54% 65%
Case Fatality Rate 11% 14%

*As of 3/31/02

In 2001, the Vermont departments of Health and Agriculture implemented statewide mosquito surveillance activities to document mosquito species and their distribution and to look for the presence of West Nile virus. These activities will continue during the 2002 transmission season. Dead bird surveillance remains the most sensitive surveillance tool for detecting West Nile virus, as some bird species experience mortality rates greater than 90 percent after infection with the virus. The public is encouraged to report dead bird sightings to the Department of Health, and birds without signs of decomposition will be tested. Equine and human testing will be conducted as appropriate. In 2001, eight Vermonters were tested for West Nile virus. Four presented with meningitis, one with encephalitis, and three had other symptoms; all were negative for West Nile.

Who should be tested

Hospitalized patients with encephalitis (especially when associated with diffuse muscle weakness), meningitis of suspected viral origin, or Guillain-Barré syndrome should be tested. Testing is not recommended for persons suspected of having West Nile virus infection on the basis of mild illness, such as fever or headache, and recent mosquito bites for several reasons: 1) Levels of West Nile virus activity in the community would have to be very high (i.e., several confirmed cases in Vermont of severe West Nile virus illness) for such symptoms to likely be due to West Nile virus infection; 2) As individuals with mild illness will most likely recover completely, testing is not necessary for establishing a care plan.

These persons should be advised to seek medical attention if more severe symptoms develop, such as confusion, severe muscle weakness, severe headache, stiff neck, or photophobia.

Specimen Collection and Transport

West Nile virus is diagnosed by examination of blood and/or cerebrospinal fluid submitted by the Vermont Department of Health Laboratory to the CDC.

Acute and convalescent serum specimens:
Collect 7–10 ml of blood in either a red-top or tiger-top collection tube. CDC recommends that acute phase serum be collected on day 10 of the illness, as a large majority of people infected with West Nile virus have detectable serum IgM antibody by the eighth day of illness. In addition, CDC recommends that convalescent serum be collected on day 21 of illness, as almost all infected individuals demonstrate long-lived serum IgG antibody by three weeks post infection. Any patient whose acute phase serum tests negative for IgM antibody to West Nile virus needs to have a convalescent phase specimen submitted for testing. Specimens should be centrifuged and 1–2 ml of serum submitted at refrigerated temperature to the Vermont Department of Health Laboratory. Specimens should be accompanied by a completed form VDHL Micro 214 “Request for Serological Examination for Bacterial, Fungal, Parasitic & Viral Agents” and a CDC History Form # 50.34 (rev 11/90).
Cerebrospinal fluid:
Collect 1–2 ml of cerebrospinal fluid (CSF) as early as possible in the first few days of illness. IgM antibody will almost always be detectable in CSF by the eighth day of illness due to West Nile virus and sometimes as early as the day of onset of symptoms; compared with serum, IgM antibody in CSF is relatively short-lived. IgG antibody in CSF often does not reach detectable levels and thus is a relatively insensitive indicator of infection. Specimens should be submitted frozen to the Vermont Department of Health Laboratory accompanied by a completed form VDHL Micro 214 “Request for Serological Examination for Bacterial, Fungal, Parasitic & Viral Agents” and a CDC History Form # 50.34 (rev 11/ 90). Date of onset must be included or CDC will not perform testing.

Call the laboratory at 1-800-660-9997, extension 7560 or 863-7560 in the Burlington area to obtain forms and serology mailers.

1 CDC. Outbreak of Powassan encephalitis – Maine and Vermont, 1999-2001. MMWR 2001;50:761-4.

Human WNV Disease Cases by week of onset graph

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Vermont: Selected Reportable Diseases April 6, 2002

reportable disease may 2002

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Important Telephone Numbers

Routine disease reporting

Vermont Department of Health
Infectious Disease Epidemiology
802-863-7240 or 1-800-640-4374 (in VT)
802-951-4080 or 1-888-588-7781 (24-hour voicemail)

For information about laboratory testing

Vermont Department of Health Laboratory
802-863-7560 or 1-800-660-9997 (in VT 8:30–4:40)

For quit smoking information

Vermont Quit Line (for smokers)
1-877-937-7848 (toll free in VT)

Vermont Department of Health Tobacco Control Program
802-863-7514

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Lyme Disease Surveillance In Vermont

In 2000 and 2001, the Vermont Department of Health conducted a canine seroprevalence study to determine if Lyme disease was present in dogs in southern Vermont. Nine veterinary practices from Bennington, Rutland, Windham, and Windsor counties participated in the study. Dogs had to meet several criteria to be included in the study, the most important being never having gone more than 10 miles beyond the Vermont border. Over the course of two years, 92 dogs were tested. Nine of the dogs (9.7%) tested positive for Lyme disease (EIA supplemented by Western Blot testing). Dogs who tested positive for Lyme disease resided in Bennington (two of 33), Rutland (one of 27), and Windham (six of 31) counties. The one dog that was tested from Windsor county was negative.

For the years 1999 through 2001, 84 confirmed cases of human Lyme disease were reported to the Vermont Department of Health. Twenty-two of these cases, representing nine counties, had likely exposure in Vermont; 62 cases were classified as imported. The exposure site for two cases was unknown. While the risk of contracting Lyme disease in Vermont is not high, it is present, and when a patient presents with symptoms suggestive of Lyme disease, it should be considered in the differential diagnosis. Early symptoms of Lyme disease may include erythema migrans (a rash at least 5 cm in diameter is considered diagnostic), fatigue, chills and fever, headache, myalgia, arthralgia, and lymphadenopathy. The rash may appear anywhere from three days to one month after the infected tick’s bite, but it usually appears in 7–14 days. Later symptoms can include numbness and pain in arms or legs, paralysis of facial muscles, meningitis, and cardiac ar-rhythmia (rare).

Laboratory testing should provide support for a clinical diagnosis of Lyme disease and should never be used as the sole basis for a Lyme disease diagnosis. All screening tests need to be followed by a more specific, supplemental test. Testing can be arranged through a reference laboratory.

Precautions to reduce the chance of a tick bite, and thereby decrease risk for Lyme disease, include minimizing skin exposure, wearing light colored clothing, using insect repellant containing DEET, and checking for ticks following outdoor activities. Studies suggest that ticks must be attached for at least 48 hours to transmit disease. Lyme vaccine is no longer available.

Lyme disease is reportable to the Vermont Department of Health by calling 1-800- 640-4374. Additional information on Lyme disease is available from the Vermont Department of Health, Epidemiology Field Unit.

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Cutaneous Melanoma

Melanoma is the most serious form of skin cancer. Melanoma is a malignant tumor that originates in melanocytes, the cells that produce the pigment melanin that gives skin its natural color and is heavily concentrated in most nevi. Melanomas fall into the following four basic categories: superficial spreading melanoma; lentigo maligna; acral lentiginous melanoma; and nodular melanoma.

The Burden of Melanoma

The American Cancer Society estimates that in 2002, approximately 53,600 persons will be diagnosed with malignant melanoma in the United States.1 Since 1981, the incidence of melanoma in the United States has increased an average of 7 percent per year to a rate of 14.3 per 100,000 in 1997. In Vermont, the age-adjusted incidence of melanoma during 1994-1996 was 14.6 per 100,000 population (95% CI: 12.9, 16.4). Melanoma is the most common cancer among people 25 to 29 years old. From 1994-1996, the age-adjusted incidence of melanoma was higher in Vermont males than Vermont females (18.0 per 100,000 vs. 12.1 per 100,000, respectively).

Malignant melanoma is the most rapidly increasing form of cancer in the U.S., causing more than 75 percent of all deaths from skin cancer.2 From 1995-1999, the age-adjusted mortality rate for melanoma in Vermont was 3.2 per 100,000 (95% CI: 2.6, 3.9) compared to 3.0 per 100,000 in the U.S.3 The mortality rate for melanoma in both Vermont men (4.6 per 100,000) and women (2.1 per 100,000) was similar to the U.S. mortality rates for each gender (U.S. male: 4.3 per 100,000; U.S. female: 2.0 per 100,000).3

Signs and Symptoms

The ABCD’s of melanoma are as follows: Asymmetry, Border irregularity, Color variability, and Diameter larger than a pencil eraser. The majority of melanomas are black or brown. However, melanomas occasionally stop producing pigment. When that happens, the melanomas may no longer be dark, but are skin-colored, pink, red, or purple.

Risk Factors

At this time, the causes of melanoma are not fully understood. Some of the factors associated with an increased risk of developing melanoma are:4

Preventing Melanoma

Exposure to the sun’s UV rays appears to be the most important factor in developing skin cancer, and skin cancer is largely preventable when sun protective practices and behaviors are consistently used. According to the 2001 Vermont Behavioral Risk Factor Surveillance Survey (BRFSS), preliminary data show that among Vermont adults aged 18 years and older, 36.6 percent of men and 60 percent of women routinely used sunblock with an sun protection factor (SPF) 15; 39.7 percent of men and 48.9 percent of women stayed in the shade when out on a sunny day; and 52.5 percent of men and 42.2 percent of women wore protective clothing when exposed to sunlight. These results emphasize the need to educate Vermonters to practice sun safety and healthy behavior patterns that can reduce the risk of developing melanoma.

Healthy Vermonters 2010

Preventing skin cancer is a priority in Healthy Vermonters 2010, the state’s blueprint for improving public health. The Healthy Vermonters 2010 goal for skin cancer is to increase to at least 75 percent the percentage of people who use at least one protective measure to decrease their risk of skin cancer (as measured by percentage of adults 18 years of age).

Diagnosing Melanoma

The most accurate diagnostic test is a biopsy. If the microscopic examination reveals melanoma, the cancer is staged based on the size and depth of the lesion, whether or not it is ulcerated, and whether metastasis has occurred.

Treatment Options

Standard treatment for melanoma is surgical excision with adequate margins. Adjuvant therapy can be used when the melanoma is metastatic. Clinical trials for the experimental treatment of melanoma are available.

Information Resources for Melanoma

References

  1. Cancer Facts and Figures 2002, American Cancer Society, 2002.
  2. MMWR Weekly, May 11, 2001. 50(18); 365.
  3. 1995-1999 Vermont Vital Records. The U.S. rates are based on the Vital Statistical System of the United States Public Use Database. U.S. rates are 1995-1999 white population mortality rates. All rates are age-adjusted to the 2000 U.S. standard population.
  4. National Cancer Institute: 1-800-4-CANCER or http://www.cancer.gov

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Vermont Women Quit Smoking and Decrease the Incidence of Low Birth Weight Babies

Smoking during pregnancy is a major public health problem. Research has shown that “smoking during pregnancy is a known cause of reduced infant birth weight, preterm delivery, and increased perinatal mortality.”1 Two studies of low birth weight in Vermont determined that “cigarette smoking during pregnancy was found to be the single most important preventable risk factor for low birth weight.”2 Low birth weight is often associated with preterm birth, and preterm birth, according to a 2000 JAMA article, “is the leading cause of infant mortality in industrialized countries and also contributes to substantial neurocognitive, pulmonary, and ophthalmologic morbidity.”3 Infants who are small for gestational age at term are also at increased risk of death.4 Surviving low birth weight infants are at increased risk of later developmental disabilities.5

Decreasing the Risk

Does the risk of delivering a low birth weight infant decrease if a pregnant woman stops smoking? Data from Vermont birth certificates suggest that mothers who quit smoking have half the risk of low birth weight delivery—the same level as mothers who did not smoke at all.

Many studies of smoking rely on a question asked of the mother during an interview. However, the question usually relates to the entire pregnancy: “Was tobacco used by mother during pregnancy?” An unknown number of mothers who smoked early in their pregnancy but then quit may have answered “no” to the question. Since January 2000, Vermont birth certificate worksheets have asked for the average number of cigarettes the mother smoked daily in the three months before pregnancy and in each trimester. This form of the question solicits more accurate replies and provides an opportunity to compare mothers who quit smoking during pregnancy with those who smoked throughout their pregnancy and those who did not smoke at all. No other state has asked the question in this way, providing Vermont a unique opportunity to study the relationship.

Low birth weight by smoking status of mother, Vermont, 2000-2001

Birth certificate records were analyzed for all babies born in Vermont to a Vermont resident mother during the years 2000 and 2001 (2001 data are preliminary). Records where either smoking status or birth weight was unknown were eliminated. The results suggest that quitting smoking before the second trimester was associated with a much lower risk of low birth weight:

Table 1. Low birthweight by smoking status of mother Vermont, 2000-2001
Smoking Status Birthweight <2500 grams
% 95%, CI*
Smokers 8.3% 7.2, 9.5
Quitters 4.1% 2.8, 6.0
Non-smokers 4.7% 4.2, 5.1

* Confidence interval.

Of the women who smoked before or during this pregnancy, about 24 percent quit before the second trimester. There are stop-smoking programs that work effectively for people who are ready to quit. Pregnant women who are ready to quit can call the toll-free Vermont Quit Line at 1-877-937-7848. Prenatal care providers who would like smoking cessation materials to offer their patients can contact their Area Health Education Center (AHEC) or the Vermont Department of Health Tobacco Control Program 802-863-7514.

References:

  1. Lucinda J. England et al, “Effects of Smoking Reduction During Pregnancy on the Birth Weight of Term Infants,”Am J Epidemiol 2001; 154:694
  2. Vermont Department of Health, “An Analysis of LBW in Vermont,” October 1996, published at http://www.state.vt.us/health/ lowbirth.htm; also, see “Low Birthweight and Preterm Risk Factors, Vermont, 1995-1998 (unpublished), which found that multiple gestation had the highest attributable risk for LBW and smoking during pregnancy had the second highest attributable risk.
  3. Michael S Kramer et al, “The contribution of mild and moderate preterm birth to infant mortality,” JAMA, 2000; 284:843
  4. Jon E. Tyson et al, “The Small for Gestational Age Infant: Accelerated or Delayed Pulmonary Maturation? Increased or Decreased Survival?” Pediatrics. 1995; 95:536
  5. Rachel N. Avchen et al, “Birth Weight and School-age Disabilities: A Population-based Study,” Am J Epidemiol 2001; 154:898-899

REPORT DISEASE: VERMONT TOLL FREE: 1-800-640-4374 OR 1-802-863-7240

Vermont Department of Health
Division of Health Surveillance P.O. Box 70 Burlington, VT 05402-0070
Agency of Human Services
Jan K. Carney, MD, MPH
Commissioner

THIS BULLETIN IS PRODUCED BY THE DISEASE CONTROL BULLETIN EDITORIAL STAFF.

Ann R. Fingar, MD, MPH
State Epidemiologist Managing Editor

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