Download Case-control Study of Armadillo Contact and Hansen`s Disease

Am. J. Trop. Med. Hyg., 78(6), 2008, pp. 962–967
Copyright © 2008 by The American Society of Tropical Medicine and Hygiene
Case-control Study of Armadillo Contact and Hansen’s Disease
Brychan M. Clark, Clinton K. Murray,* Lynn L. Horvath, Gregory A. Deye, Mark S. Rasnake, and
Robert N. Longfield
Department of Infectious Diseases, Wilford Hall Medical Center, Lackland Air Force Base, Texas; Department of Medicine, Brooke
Army Medical Center, Fort Sam Houston, Texas; U.S. Air Force Office of the Surgeon General, Medical Modernization Directorate,
Pentagon, Falls Church, Virginia; Department of Medicine, University of Tennessee Graduate School of Medicine, Knoxville,
Tennessee; Medicine Specialty Service, University of Texas at Tyler and Texas Center for Infectious Diseases, San Antonio, Texas
Abstract. Hansen’s disease (HD) continues to have worldwide impact despite efforts to eradicate the disease.
Although a definitive transmission mode has not been identified, data supports an association between HD and contact
with the nine-banded armadillo. We conducted a case-control study of 28 HD patients to determine if there is an
association between armadillo exposure and HD. There was no association between HD and place of birth or having
hunted, consumed, or had direct or indirect contact with deer, birds, or squirrels. Univariate analysis showed that
residence in Mexico (P ⳱ 0.001), hunting rabbits (P ⳱ 0.04), cleaning rabbits (P < 0.001), and armadillo exposure from
hunting (P ⳱ 0.005), cleaning (P ⳱ 0.004), consuming (P ⳱ 0.002) them, or having direct armadillo contact (P ⳱ 0.017)
were associated with HD. Multivariate analysis showed that eating armadillos (P ⳱ 0.039, odds ratio [OR] ⳱ 3.65, 95%
confidence interval [CI] ⳱ 1.07–12.4), cleaning rabbits (P ⳱ 0.018, OR ⳱ 4.08, 95% CI ⳱ 1.27–13.1), and having lived
in Mexico (P ⳱ 0.006, OR ⳱ 24.9, 95% CI ⳱ 2.52–245) were associated with HD.
INTRODUCTION
fluorescent antibody studies, mycolic acid analysis, and DNA
analysis.9,10 Human HD related to armadillos has been described in many patients with close contact with armadillos
and no other exposure risks.11–17 Arguing against an association is an age- and sex-matched study of 19 HD patients from
Louisiana in 1977 that did not show an association with exposure to armadillos.18
Data regarding an association between contact with the
nine-banded armadillo and the development of HD have
been conflicting. Case-control studies to delineate an association between the two have not been adequately conducted.
We conducted a retrospective case-control study of HD patients to determine if there is an association between armadillo contact or consumption and the subsequent development of HD.
Hansen’s disease (HD), or leprosy, is a nationally reportable infectious disease in the United States that continues to
have worldwide impact despite the commitment of the World
Health Organization to eliminate the disease.1–3 Although
most HD occurs in Latin America, Africa, Asia, and various
islands in the western Pacific, there were 166 new cases reported in the United States in 2005, mostly in California,
Louisiana, Texas, New York, Massachusetts, and Hawaii.3
Most cases that occur in the United States are in immigrants
but autochthonous foci for HD transmission have also been
recognized.2–4
Numerous modes of transmission have been proposed for
HD but no mode is currently based on solid evidence. Traditionally, it was believed that the spread of infection was by
respiratory droplets or by skin-to-skin contact. Although insect transmission in the laboratory has been previously described, this is unlikely to be a source of human infection.5
Hansen’s disease may also be zoonotic because it has been
described in the armadillo, chimpanzee, and Mangabey monkey.2,6 Discovery of soil glycolipids from Mycobacterium leprae in armadillo habitats, the predominance of M. leprae in
rural and not urban areas, transmission of M. leprae through
dermal inoculation (tattoos), and the decreasing rate of disease in areas that have become more industrialized all suggest
that, like with other non-tuberculous mycobacteria, soil might
be a source of transmission.7 However, the inability to readily
culture M. leprae from the environment is a significant barrier
to investigating environmental reservoirs and related modes
of transmission.
The armadillo has been a research model for HD because
of its cooler body temperature, reproductive rate, and similarity to human HD clinically after inoculation with M. lepraeinfected tissue.8 Nine-banded armadillos (Dasypus novemcinctus) in Louisiana were previously found to have a form of HD
identical to human HD on the basis of histologic examination,
MATERIALS AND METHODS
Patients who were seen at the Texas Center for Infectious
Diseases (San Antonio, TX) from January 2001 through June
2005, were eligible to participate in the study. The Texas Center for Infectious Diseases (TCID) is a public health facility of
the Texas Department of State Health Services that provides
inpatient treatment of patients with tuberculosis (TB) and
outpatient treatment of patients with HD. Patients treated at
TCID are all referred from the same regional area, which
enabled control of geographic bias in the study. Study participants included males and females 18–100 years of age who
were undergoing routine care for either HD or TB. These
participants, including the control group, were asked to voluntarily participate in the study as they were evaluated in the
clinic or inpatient ward for their underlying infection after the
protocol was implemented at the site. Subjects were approached in a serial fashion initially; first all inpatients currently in the facility and then new admissions or outpatients
as they came to the clinic until the number of participants and
corresponding controls were obtained. Consent was obtained
at the time of enrollment and a face-to-face interview by the
primary or associate investigators using the study questionnaire was then performed. For every HD patient participating
in the study, two control patients with M. tuberculosis infec-
* Address correspondence to Clinton K. Murray, Department of
Medicine, Brooke Army Medical Center, 3851 Roger Brooke Drive,
Fort Sam Houston, TX 78216. E-mail: [email protected]
962
963
ARMADILLO CONTACT AND HANSEN’S DISEASE
contrasts. Statistical analysis was performed using the software program SPSS version 13.0 (SPSS Inc., Chicago, IL).
RESULTS
FIGURE 1. Distribution of the nine-banded armadillo (Dasypus
novemcinctus) in the United States, 1995.
tion were enrolled and entered into the study. Selection of the
control group was based on the patient population cared for
at TCID and not an attempt to compare the two mycobacterial diseases. Routine clinical care was determined by the
treating physician and was not influenced by participation in
the study.
A comprehensive questionnaire was administered to all
study participants in either English or Spanish, depending on
the patient’s native language. Demographic details collected
included age, sex, race, date of diagnosis, place of birth, type
of HD, and state and country of residence in childhood, adulthood, and at the time of diagnosis. Subjects were evaluated
for having ever hunted, cleaned, eaten, or direct or indirect
contact with armadillos, deer, rabbits, birds or squirrels, and
where these activities took place. Exposure to a variety of
animals rather than just armadillo exposure was evaluated by
the study in an effort to minimize the potential for bias. The
other animals were chosen because they are commonly encountered in activities such as hunting, butchering, gardening,
frequently kept as pets, and consumed across the country,
making regional geographic bias less likely. Subjects were
asked if they knew of an association between animal contact
and HD or, more specifically, armadillo contact and HD. Subjects were also asked if they had a family member with HD
and whether the family member with HD had contact with
armadillos. Direct contact was defined as having an armadillo,
deer, rabbit, bird or squirrel for a pet, working in the field
with direct contact with any of these animals, or preparing
them for a meal. Indirect contact was defined as working in
fields or gardens with any of these animals present or seen but
not actually having direct contact with the animal. Residence
in a given state was further classified as an armadilloinhabited area of the United States or a non-inhabited area.
This classification was based on the known current and projected range of the nine-banded armadillo within the United
States (Figure 1).19 The armadillo expansion map in Figure 1,
adapted from Taulman and Robbins, illustrates the known
established range of the nine-banded armadillo as of 1995 that
included Texas, Oklahoma, Kansas, Missouri, Arkansas,
Louisiana, Mississippi, Alabama, Tennessee, Georgia, South
Carolina, Florida, and Illinois.19
Categorical variables were then compared with chi-square
and Fisher’s exact tests, and multivariate analysis was performed using logistic regression with significance assigned to
P values ⱕ 0.05. All categorical variables with P < 0.10 by
univariate analysis were included in the multivariate model
using backwards conditional logistic regression with simple
From January 2001 through June 2005, a total of 28 HD
patients and 59 controls were enrolled in the study. Of the
study participants, HD patients were generally older than
control patients at the time of diagnosis with a mean age of 52
years for HD patients compared with 43 years for control
patients, but this difference was not statistically significant by
univariate analysis (Table 1). Although Hispanics outnumbered Caucasians by nearly 2:1 and African-Americans by
almost 3:1 (Table 1), there was no significant association between race and HD. Among HD patients, men outnumbered
women 3:1 and were generally younger with a mean age of 50
years compared with a mean age of 57 years for women
(Table 1). There was no statistically significant difference
with regard to sex among the two groups.
Most HD patients and controls had previously resided in an
armadillo-inhabited area of the United States, specifically
Texas, Oklahoma, Louisiana, Arkansas, Mississippi, Alabama, Florida, and Georgia. Among study participants, 64%
of HD patients and 81% of control subjects reported living in
Texas, either in childhood or as an adult, prior to their diagnosis. When study participants with armadillo exposure reported where their exposure to armadillos took place, it was
almost always in Texas or Mexico. However, because most
study participants with armadillo exposure did not report the
location of their exposure, this variable could not be further
analyzed.
Within the HD study group, seven patients had tuberculoid
HD, one had borderline tuberculoid HD, three had borderline HD, four had borderline lepromatous HD, eight had lepromatous HD, and five had either indeterminate HD or were
not classified further. Because there were so few patients with
a particular type of HD, further statistical analysis of this
variable was not performed.
Univariate analysis showed that there was no association
between having HD and having hunted, consumed, or had
direct contact with deer, birds, or squirrels, in fields or gardens, as pets, or in preparation of the animal meat for cooking
(Tables 1 and 2). There was a trend toward an association between HD and having either direct contact with rabbits (P ⳱
0.081, odds ratio [OR] ⳱ 2.24, 95% confidence interval [CI] ⳱
0.90–5.6) or eating rabbit meat (P ⳱ 0.057, OR ⳱ 2.70, 95%
CI ⳱ 0.95–7.63). Hunting rabbits (P ⳱ 0.04, OR ⳱ 2.59, 95%
CI ⳱ 1.03–6.55), cleaning rabbits (P < 0.001, OR ⳱ 5.78, 95%
CI ⳱ 2.18–15.4), cleaning birds (P ⳱ 0.012, OR ⳱ 3.39, 95%
CI ⳱ 1.28–9.01), and armadillo exposure from hunting (P ⳱
0.005), cleaning (P ⳱ 0.004), eating armadillo meat (P ⳱
0.002), or having direct armadillo contact (P ⳱ 0.017) were all
associated with HD by univariate analysis. All animal exposure occurred prior to diagnosis of either HD or TB.
Among patients with HD who hunted armadillos, 67% also
frequently ate the armadillos, whereas only 44% of the controls who hunted armadillos reported consuming armadillo
meat (P ⳱ 0.002, OR ⳱ 1.74, 95% CI ⳱ 1.22–2.49). Among
patients with HD who consumed armadillo meat, 60% also
reported cleaning bird and rabbit meat compared with only
22% of controls. Hunting and cleaning of rabbits and arma-
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CLARK AND OTHERS
TABLE 1
Baseline characteristics of study participants*
Multivariate analysis
Characteristic
HD (N ⳱ 28)
TB (N ⳱ 59)
Univariate analysis P†
Mean age at diagnosis, years (range)
Sex
Male (% of patients)
Female (% of patients)
Race (%)
Hispanic
Caucasian
African-American
Other
Place of birth (%)
Mexico
Armadillo-inhabited area of United States
Areas of United States without armadillos
Residence in childhood (%)
Mexico
Armadillo-inhabited area of United States
Areas of United States without armadillos
Residence as adult (%)
Mexico
Armadillo-inhabited area of United States
Areas of United States without armadillos
Type of Hansen’s disease (%)
Tuberculoid
Borderline tuberculoid
Borderline
Borderline lepromatous
Lepromatous
Indeterminate
Family contact with Hansen’s disease
52 (21–76)
43 (22–70)
21 (75)
7 (25)
52 (88)
7 (12)
NS
NS
21 (75)
7 (25)
0
0
23 (39)
17 (31)
16 (25)
3 (5)
8 (29)
18 (64)
2 (7)
5 (8)
51 (86)
3 (5)
10 (36)
16 (57)
2 (7)
5 (8)
51 (86)
3 (5)
8 (29)
19 (64)
1 (4)
1 (2)
56 (95)
2 (3)
7 (25)
1 (4)
3 (11)
4 (14)
8 (29)
5 (18)
3 (11)
2 (3)
OR (95% CI)
P†
24.9 (2.52–245)
0.006
NS
NS
0.01
0.001
NS
* HD ⳱ Hansen’s disease; TB ⳱ tuberculosis; OR ⳱ odds ratio; CI ⳱ confidence interval; NS ⳱ not significant.
† Significance was assigned to P values ⱕ 0.05.
TABLE 2
Correlation of animal exposure and Hansen’s disease (HD)*
Characteristic
Hunted
Armadillo
Rabbits
Deer
Birds
Squirrels
Cleaned
Armadillo
Rabbits
Deer
Birds
Squirrels
Direct contact
Armadillo
Rabbits
Deer
Birds
Squirrels
Indirect contact
Armadillo
Rabbits
Deer
Birds
Squirrels
Consumption
Armadillo
Rabbits
Deer
Birds
Squirrels
HD
Controls
N ⳱ 28 (%)
N ⳱ 59 (%)
OR (95% CI)
12 (43)
17 (61)
13 (46)
12 (43)
8 (29)
9 (15)
22 (37)
19 (32)
18 (31)
17 (61)
4.17 (1.49–11.7)
2.59 (1.03–6.55)
0.005
0.040
NS
NS
NS
10 (28)
18 (64)
9 (32)
13 (46)
7 (25)
6 (10)
14 (24)
10 (17)
12 (20)
10 (17)
4.91 (1.56–15.4)
5.78 (2.18–15.4)
0.004
< 0.001
NS
0.012
NS
10 (28)
16 (57)
13 (46)
13 (46)
8 (29)
8 (14)
22 (79)
18 (31)
23 (39)
14 (24)
3.54 (1.21–10.4)
2.24 (0.90–5.60)
15 (54)
19 (68)
10 (28)
15 (54)
13 (46)
24 (41)
30 (51)
30 (51)
37 (63)
35 (59)
13 (46)
22 (78)
24 (86)
13 (46)
12 (43)
9 (15)
34 (58)
45 (76)
20 (34)
19 (32)
* OR ⳱ odds ratio; CI ⳱ confidence interval; NS ⳱ not significant.
† Significance was assigned to P values ⱕ 0.05.
Univariate analysis
3.39 (1.28–9.01)
Multivariate analysis
P†
OR (95% CI)
P†
NS
NS
4.08 (1.27–12.4)
NS
0.018
NS
0.017
0.081
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
4.82 (1.72–13.5)
2.70 (0.90–7.65)
0.002
0.057
NS
NS
NS
3.65 (1.07–12.4)
0.039
NS
ARMADILLO CONTACT AND HANSEN’S DISEASE
dillos were highly collinear. Therefore, hunting these animals
was excluded from the multivariate model because of the
stronger association and more plausible intense exposure history between HD, cleaning rabbits (P ⳱ 0.001), and cleaning
armadillos (P ⳱ 0.004).
After multivariate analysis (Table 2), consumption of armadillos (P ⳱ 0.039, OR ⳱ 3.65, 95% CI ⳱ 1.07–12.4), cleaning rabbits (P ⳱ 0.018, OR ⳱ 4.08, 95% CI ⳱ 1.27–13.1), and
having lived in Mexico (P ⳱ 0.006, OR ⳱ 24.9, 95% CI ⳱
2.52–245) were all independently associated with HD. Logistic regression analysis showed that there was no significant
correlation between HD and having hunted, cleaned, or had
direct contact with armadillos. Cleaning birds, hunting rabbits
and contact with rabbits in fields or gardens, as pets, or in
preparation of the animal meat for cooking were also not
associated with HD.
More patients in the HD group than the control group had
heard of an association between animals and HD (P ⳱ 0.001),
but there was no difference between the two groups when it
came to having heard specifically of an association between
armadillos and the development of HD (P ⳱ 0.712). Few
patients reported contact with HD cases within the home. For
our study participants, there was no association between having HD and having a family member with HD.
Only 2% of the controls reported living in Mexico as an
adult compared with 29% of HD patients (P ⳱ 0.001). Univariate analysis showed that patients with HD were also more
likely to report living as a child (P ⳱ 0.01) in Mexico, where
the nine-banded armadillo has been present since the 14th
century.16 Because childhood and adult residence in Mexico
were highly collinear, only adult residence in Mexico was
included in multivariate analysis because of the stronger association (P ⳱ 0.001 versus P ⳱ 0.01) with HD. When compared with the control group, patients with HD were 25 times
more likely to have resided in Mexico as an adult (P ⳱ 0.006,
OR ⳱ 24.9, 95% CI ⳱ 2.52–245) than in an armadillo-inhabited
area of the United States.
DISCUSSION
As a public health facility, TCID provides treatment primarily for patients with TB and HD. The selection of the
control group was based on the population available for study
at TCID and was not an attempt to compare the two mycobacterial diseases. There were large numbers of Mexicanborn and Hispanic persons within the general population that
served as the referral base for the study center. All study
participants were referred from the same general area, which
enabled control of geographic bias in the study.
Our findings indicate that residing in Mexico, eating armadillos, and cleaning the dead carcass of a rabbit are all associated with human HD. Although there was some association
by univariate analysis between HD and armadillo exposure
from hunting, cleaning, or directly handling armadillos in
fields, as pets, or in the preparation of armadillo meat for a
meal, this did not remain significant after analysis by logistic
regression. When compared with the control group, most
(67%) patients with HD who had hunted armadillos also
cleaned the dead carcass and ate the armadillo meat. Because
cleaning armadillos had a stronger association with HD (P ⳱
0.004, OR ⳱ 4.91, 95% CI ⳱ 1.56–15.4) than hunting armadillos did by univariate analysis (P ⳱ 0.005, OR ⳱ 4.17, 95%
965
CI ⳱ 1.49–11.7), hunting armadillos was excluded from the
multivariate model because it was most likely a confounding
variable. When hunting armadillos was controlled for in logistic regression analysis, patients who frequently ate armadillo meat were almost four times more likely to have HD
than those who had never eaten an armadillo. Although
cleaning rabbit meat was found to be associated with HD by
multivariate analysis (OR ⳱ 4.08), it is unclear if this is a true
association because most HD patients who had hunted, eaten,
and cleaned armadillo meat also tended to clean bird and
rabbit meat. Cleaning rabbit meat might be a confounder or
a marker of exposure risk for some unidentified environmental risk factor that has yet to be discovered.
Previous studies have reported conflicting data regarding
an association between contact with the nine-banded armadillo and development of HD. In 1971, the armadillo was
noted to be a research model for HD because of its cooler
body temperature, reproductive rate, and similarity to human
HD clinically after inoculation with M. leprae-infected tissue.8
In 1975, nine-banded armadillos in Louisiana were noted to
have HD that was identical to human HD disease on the basis
of histologic examination, fluorescent antibody studies, mycolic acid analysis, and DNA analysis.9,10
Human HD related to armadillos was first described in
1981 when a Texas rancher with HD was noted to have significant armadillo contact but no other exposure risks such as
contact with HD patients or travel overseas.11 In 1983 and
1984, 6 cases of HD were described with associated close contact
with armadillos but no other exposure risks were noted.12,13 A
1987 study in Los Angeles, California, showed an association
among Mexican-born patients with HD and armadillo exposure.14 The relative risk for Mexican-born males was an OR
of 6.5 for direct exposure and an OR of 2.7 for indirect exposure, whereas for Mexican-born females, the OR was 4.1
for direct exposure and 3.5 for indirect exposure.14 In 1988, 6
cases of HD were described in residents of a non-endemic
area of northern Louisiana with significant armadillo exposure as the only risk factor for HD.15 More recently, a case of
HD was reported in a woman from Georgia with no other
exposure risks other than frequently working in a garden
where armadillos burrowed or were buried.16 A study in 2000
showed that 71% of non-Asian patients with HD in Houston,
Texas, reported direct or indirect contact with armadillos compared with none of the Asian patients with HD (P < 0.001).17
Arguing against an association between armadillo contact
and HD is a 1977 age- and sex-matched study of 19 HD
patients from Louisiana that did not show an association with
exposure to armadillos.18 Our study found that consumption
of armadillos, and possibly to a lesser extent, cleaning the
bloody carcass of a dead armadillo and direct armadillo contact were associated with HD. Unlike the previous study that
showed an association among Mexican-born patients and
HD, we found no correlation between place of birth and HD.
Although there were disproportionately more Hispanic patients in the HD group than the control group, we found no
significant association between race and having HD. Because
all study participants came from the same general referral
area that contained a high percentage of Hispanic and Mexican-born persons among the general population, the possibility of an unintended selection bias is less likely. Previously
residing in Mexico, where armadillos have been present for
many centuries, seemed to be the most important risk factor
966
CLARK AND OTHERS
in our study for acquiring leprosy with an odds ratio of 24.9.
Because only 2% of controls reported living in Mexico as an
adult compared with 29% of HD patients (P ⳱ 0.001), an environmental bias may have been introduced if the migration
from rural to more urban areas coincided with migration from
Mexico to the southern part of the United States, specifically
Texas. Although our findings support most of the previously
published literature regarding an association between armadillo contact and HD, further studies that match for race, age,
and residence in Mexico may eliminate any potential bias that
might reflect a person’s habits associated with their ethnicity
or living in rural areas.
Hansen’s disease has affected humans throughout recorded
history. Because of an exceptionally stable genome, M. leprae
can be a helpful marker for tracking the migration of people
over time.20 The M. leprae strain in North America is genetically closest to that found in Europe and west Africa and was
likely transported by colonial and migratory voyages.20 Wild
armadillos from Louisiana, which have been found to be naturally infected with M. leprae, harbor the European/North African SNP type 3 strain, indicating that they acquired the infection
from human sources.20 There is currently little direct evidence of
an environmental source or reservoir of M. leprae, other than
armadillos.20 Other Mycobacterium, such as M. ulcerans, can
be transmitted to humans by insect bites, and various nontuberculous mycobacteria have well-described environmental
reservoirs.21 Although transmission of viable M. leprae from
HD patients to mice has been shown to occur in the laboratory, it is unlikely to be a source of human infection.5,22 The
presence of M. leprae phenolic glycolipids in the soil of armadillo habitats, the predominance of M. leprae in rural areas, transmission of M. leprae through dermal inoculation
(tattoos), and the decreasing rate of disease in industrialized
areas all suggest that soil might be a potential source of transmission.7 However, the inability to readily culture M. leprae
from the environment has proven to be a significant barrier to
investigating environmental reservoirs and other related
modes of transmission.23,24
Population serosurveys in disease-endemic areas have demonstrated antibodies to M. leprae phenolic glycolipid I among
otherwise healthy persons, and it has been postulated that
people are exposed to a common source of the bacillus, perhaps in the environment, although no environmental reservoir of M. leprae, other than armadillos, has been demonstrated to date.25,26 Although eating armadillos and cleaning
rabbits were associated with human HD in our study, living in
Mexico seemed to be the most important risk factor, indicating that contact with an, as yet uncharacterized, environmental reservoir of M. leprae might account for transmission of
the disease. Further elucidation of the mode or modes of
transmission of M. leprae would be important in prevention
and control of HD.
Received September 28, 2007. Accepted for publication February
7, 2008.
Disclaimer: The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or
reflecting the views of the U.S. Department of the Army, the U.S.
Department of the Air Force, the U.S. Department of Defense, or the
U.S. government.
Disclosure: The authors are employees of the U.S. government and
this work was performed as part of their official duties. As such, there
is no copyright to be transferred.
Authors’ addresses: Brychan M. Clark, Department of Medicine,
Mike O’Callaghan Federal Hospital, 4700 Las Vegas Boulevard
North, Nellis Air Force Base, NV 89191. Clinton K. Murray and Lynn
L. Horvath, Department of Medicine, Brooke Army Medical Center,
3851 Roger Brooke Drive, Fort Sam Houston, TX 78216. Gregory A.
Deye, Walter Reed Army Institute of Research, 503 Robert Grant
Avenue, Silver Spring, MD 20910. Mark S. Rasnake, Department of
Medicine, University of Tennessee Graduate School of Medicine,
1924 Alcoa Highway, Knoxville, TN 37920. Robert N. Longfield,
Medicine Specialty Service, University of Texas at Tyler and Texas
Center for Infectious Diseases, 2303 SE Military Drive, San Antonio,
TX 78223.
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