Bureau of Epidemiology
Bureau of Epidemiology September 1999 Utah Department of Health
Necrotic Arachnidism In Utah
New Surveillance Activities At The Bureau
Quarterly Report of Diseases of Low Frequency
Monthly Morbidity Summary


Necrotic Arachnidism In Utah

The European aggressive house spider (Tegenaria agrestis), commonly known in the United States as the hobo spider, was first identified in Utah in 1990. This spider, as well as the brown recluse spider (Loxosceles reclusa) and the yellow sac spiders (Chiracanthium inclusum and C. meldei), have been recognized as the cause of necrotic spider bites. The brown recluse spider is not known to be established in Utah.

Hobo spider

The hobo spider is a relatively large spider, of caramel or brown color with a characteristic “herring bone” pattern on its abdomen and distinct stripes on either side of the cephalothorax (Figure 1). It has been found in northern Utah as far south as Sanpete County and as far east as Summit County (Figure 2). While the common European name for the hobo spider is the aggressive house spider, the spider is no more aggressive than other wandering spiders.

In the fall, female spiders build webs and remain stationary. Male spiders begin nocturnal wandering in search of mates. Spiders may enter houses, often in large numbers, from outside habitats during this period, and most bites occur in the fall. However, hobo spiders do not usually lay their eggs inside homes. Hobo spiders are not good climbers and are usually found at ground or basement levels. Spiders can be controlled from entering the house by ensuring a tight seal between the foundation and the wood structures of a house, and in all low portals of entry such as under outside doors. Ground vents and basement windows should be properly sealed or screened. In addition, good house cleaning practices will discourage the spiders from inhabiting areas where people are present.

A large percentage of hobo spider bites are dry defensive bites where no venom is injected. When envenomation does occur, both local and/or systemic manifestations may appear. Typically, immediately following envenomation, a large area of erythema (redness) forms around the bite site. This erythema will usually disappear in a few hours, leaving a small reddish induration (hardened area). Within 24 to 48 hours, blistering may occur at the site. These blisters may rupture, leaving an open ulceration, which will progress to an escar (scab). By about three weeks post-bite, this becomes pronounced, giving the lesion a “target and bulls-eye” appearance. Eventually, the eschar is sloughed and the lesion gradually heals, leaving a scar. In some instances, particularly when the bite is delivered in an area of fatty tissue, the lesion may become deep and extensive and may not heal for two to three years. In most instances, however, the lesion heals in about 45 days after the original bite.

Long-term sequelae from a hobo spider bite may include intractable burning pain, a damaged vascular system and cyst development in the area of the bite. Approximately half of the people who are envenomated by the hobo spider suffer systemic effects that include severe headaches that may not respond to over-the-counter analgesics, dry mouth, nausea, weakness, lethargy, dizziness, visual disturbances, hallucinations, and joint pains. In rare cases, aplastic anemia will develop several weeks after the bite and this may be fatal. Spider bite lesions are generally sterile but occasionally may develop a secondary infection. Approximately 15% of people who are envenomated require hospitalization.

Figure 1. Hobo spider
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Yellow sac spider

The yellow sac spider is a relatively small spider (10 mm body length) with a light yellow or yellow-green color and no distinguishing marks on the abdomen, cephalothorax or legs. These spiders are common throughout Utah, found in homes year-round, and may spin a web in ceiling corners. These spiders are best controlled by regular removal of the webs and nests.

Bites from yellow sac spiders are not as severe as those from hobo spiders. These bites generally produce instant, intense stinging pain, followed by localized redness, swelling and itching. The bite may or may not become a necrotic lesion, but if that occurs, healing is usually complete within eight weeks. Systemic effects are usually not severe and include chills, fever, headache, dizziness, nausea, anorexia. Shock is a rare complication.

Treatment for both hobo spider and yellow sac spider bites is similar and generally only effective if started within the first 24 hours following the bite. Local excision of the wound to remove all envenomated tissue may be appropriate if done in the first 12 hours. Steroids may be helpful if administered early.

Figure 2. Counties with hobo spider sightings.

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New Surveillance Activities At The Bureau

An important part of epidemiology is the ability to conduct public health surveillance. Public health surveillance is the continuous and systematic process of collecting, analyzing and interpreting health data. The ultimate goal of surveillance is the rapid dissemination of accurate information that will help health care providers and other health agencies in disease control and prevention. Surveillance data is also used as a basis for shaping public health policy.

A principle task of the Bureau of Epidemiology (BOE) is to conduct surveillance. The BOE is continually working to improve its surveillance capabilities. Recent awards from the Centers for Disease Control and Prevention (CDC), will assist the BOE with this undertaking.

Assessment of the Blood Lead Levels in Utah Medicaid Children

Since 1990, the BOE has maintained a registry of blood lead testing results on Utah residents. Initially, the registry only recorded the results of adults with elevated blood lead levels, as part of the Adult Blood Lead Epidemiology and Surveillance (ABLES) project. In 1996, the BOE expanded the Utah Blood Lead Registry (UBLR) to include children and started the Child Blood Lead Epidemiology and Surveillance (CBLES) project. The CBLES project investigates child blood lead poisoning, and ensures that children with elevated blood lead levels receive appropriate medical intervention and follow-up.

Nationally, Medicaid children have been identified as a particularly high risk group for blood lead poisoning. Medicaid children are at risk because 1) they often live in high risk housing - older homes that contain lead-based paint and are in poor condition, and 2) they live in homes where working adults are more likely to work in high risk occupations such as auto repair or scrap metal work. (Additionally, these adults are less likely to have received the appropriate training for protecting their families from carry home lead.)

To assess the risk of Utah Medicaid children for blood lead poisoning, the BOE will conduct a targeted surveillance project. Bureau staff will perform blood lead testing in a sample of Utah’s Medicaid child population using two portable blood lead analyzers to be purchased with funding from the CDC. While these surveillance teams are testing Medicaid children for blood lead, the teams will also conduct health risk assessments, and in some cases, limited environmental investigations.

ATSDR Cooperative Agreement to Conduct Site-Specific Health Assessment Activities

In September 1998, the BOE’s, Environmental Epidemiology Program was awarded funding for a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). The funds will be used to build the BOE’s capacity to conduct site-specific environmental health assessment activities in Utah. With this new capacity, the BOE will be better able to conduct environmental health assessments for sites that are contaminated with chemical toxins such as industrial wastes or mining wastes. The objectives of the project are to collect information about the contaminants from data provided by other state and federal agencies, identify populations at risk, identify possible exposure pathways, determine if the contaminants pose a health risk, and determine if any mitigating actions are needed. Another objective is to develop the capacity to provide community education about the investigated sites. This objective involves assessing the concerns of the community and providing information to address those concerns and additional concerns that may be raised by the health assessment.

The BOE is conducting assessments on a variety of sites. These sites include those that are listed in the National Priorities List (NPL) under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund), and other industrial sites that have produced or are producing toxic waste.

Epidemiology and Laboratory Capacity for Infectious Diseases Cooperative Agreement

In 1998, the BOE’s, Communicable Disease Control Program and the Utah Public Health Laboratory were awarded funding for a cooperative agreement with the CDC to increase the capacity for conducting infectious disease surveillance and providing a rapid public health response. The cooperative agreement will assist the BOE in accomplishing the following goals:

Implementation of electronic reporting from local health departments and reporting agencies.

Implementation of electronic dissemination of public health information to health care providers.

Rapid laboratory identification and confirmation of infectious agents.

Implementation of improved methods for detecting and monitoring emerging infectious diseases.

Surveillance of trends in antimicrobial resistance patterns.

Active surveillance of food borne and respiratory infectious diseases.

The Communicable Disease Control Program is currently assisting local health departments in acquiring the capability to submit data to the BOE electronically. Eight of the twelve local health districts are now able to submit communicable disease data to the Bureau electronically. The Communicable Disease Control Program is developing an Internet-based electronic reporting system to allow clinical laboratories, healthcare providers, and hospital emergency departments to report directly to the Bureau.

To provide health care data to users, an Internet web site (http:\\hlunix.hl.state.ut.us/els/epidemiology/index.html) has been established. The BOE is publishing a variety of reports on the website for public use. In the near future, the BOE will be able to publish regular updates on seasonal diseases such as influenza. An Internet based query system that will allow health care providers and researchers to query the surveillance database for current disease trends and rates is being developed. In addition, the Division of Epidemiology and Laboratory Services has established a listserver to broadcast infectious disease alerts by Email. Health care providers, public health workers and laboratorians can join or search the listserver by going to http://list.state.ut.us/shellcgi/lyris, clicking on 1) Health, and then 2) choosing Bureau of Microbiology.

Public Health Preparedness and Response for Bioterrorism

The BOE, with other state and local agencies, has recently received notification of an award of funds that will be used to develop an effective public health response to bioterrorism. Funds will be used to support planning activities, assessments, surveillance, epidemiological investigations, and training. In addition, funds will be used to improve the state laboratory’s capacity to identify potential bioterrorism agents, and to develop a statewide comprenhensive health alert network.

Utah is growing, both in population and in national and international influence. The state has some of the nation’s most popular winter and summer vacation sites. Utah is home to a variety of military establishments and other important industries. These scenarios are unlikely to change in the future, particularly as Utah prepares to host the 2002 Winter Olympics. With this CDC funding, the BOE will be able to increase its capacity for conducting surveillance for and responding to all diseases including those potentially associated with bioterrorism.



Quarterly Report of Diseases of Low Frequency Year-to-Date January 1 - September 30, 1999
(including a comparison for same time period 1995 -1998)

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Utah Department of Health, Bureau of Epidemiology
Monthly Morbidity Summary - September 1999 - Provisional Data

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The Epidemiology Newsletter is published monthly by the Utah Department of Health, Division of Epidemiology and Laboratory Services, Bureau of Epidemiology, to disseminate epidemiologic information to the health care professional and the general public.

Send comments to:  The Bureau of Epidemiology, Box 142104, Salt Lake City, UT 84114-2104, or call (801) 538-6191

Approval 8000008:  Appropriation 3705

Rod Betit, Executive Director, Utah Department of Health
Charles Brokopp, Dr.P.H., Division of Epidemiology and Laboratory Services
Craig R Nichols, MPA, Editor, State Epidemiologist, Director Bureau of Epidemiology
Gerrie Dowdle, MSPH, Managing Editor
Connie Dean, Production Assistant