|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.
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
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
Figure 1. Hobo spider
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.
Counties with hobo spider sightings.
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
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 Utahs 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
In September 1998, the BOEs, 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 BOEs 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
In 1998, the BOEs, 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
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
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.
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 laboratorys 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 nations 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.
of Diseases of Low Frequency Year-to-Date January 1 - September 30, 1999
(including a comparison for same time period 1995 -1998)
Department of Health, Bureau of Epidemiology
Monthly Morbidity Summary - September 1999 -
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