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Volume 9, Number 8—August 2003

Volume 9, Number 8—August 2003   PDF Version [PDF - 6.69 MB - 141 pages]

Perspective

  • Porcine Reproductive and Respiratory Syndrome Virus: Origin Hypothesis PDF Version [PDF - 222 KB - 6 pages]
    P. G. Plagemann
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    Porcine reproductive and respiratory syndrome is a serious swine disease that appeared suddenly in the midwestern United States and central Europe approximately 14 years ago; the disease has now spread worldwide. In North America and Europe, the syndrome is caused by two genotypes of porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus whose genomes diverge by approximately 40%. My hypothesis, which explains the origin and evolution of the two distinct PRRSV genotypes, is that a mutant of a closely related arterivirus of mice (lactate dehydrogenase-elevating virus) infected wild boars in central Europe. These wild boars functioned as intermediate hosts and spread the virus to North Carolina in imported, infected European wild boars in 1912; the virus then evolved independently on the two continents in the prevalent wild hog populations for approximately 70 years until independently entering the domestic pig population.

  • Detecting Bioterror Attacks by Screening Blood Donors: A Best-Case Analysis PDF Version [PDF - 344 KB - 6 pages]
    E. H. Kaplan et al.
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    To assess whether screening blood donors could provide early warning of a bioterror attack, we combined stochastic models of blood donation and the workings of blood tests with an epidemic model to derive the probability distribution of the time to detect an attack under assumptions favorable to blood donor screening. Comparing the attack detection delay to the incubation times of the most feared bioterror agents shows that even under such optimistic conditions, victims of a bioterror attack would likely exhibit symptoms before the attack was detected through blood donor screening. For example, an attack infecting 100 persons with a noncontagious agent such as Bacillus anthracis would only have a 26% chance of being detected within 25 days; yet, at an assumed additional charge of $10 per test, donor screening would cost $139 million per year. Furthermore, even if screening tests were 99.99% specific, 1,390 false-positive results would occur each year. Therefore, screening blood donors for bioterror agents should not be used to detect a bioterror attack.

Research

  • Legionnaires’ Disease Outbreak in Murcia, Spain PDF Version [PDF - 279 KB - 7 pages]
    A. García-Fulgueiras et al.
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    An explosive outbreak of Legionnaires’ disease occurred in Murcia, Spain, in July 2001. More than 800 suspected cases were reported; 449 of these cases were confirmed, which made this the world’s largest outbreak of the disease reported to date. Dates of onset for confirmed cases ranged from June 26 to July 19 , with a case-fatality rate of 1%. The epidemic curve and geographic pattern from the 600 completed epidemiologic questionnaires indicated an outdoor point-source exposure in the northern part of the city. A case-control study matching 85 patients living outside the city of Murcia with two controls each was undertaken to identify the outbreak source; the epidemiologic investigation implicated the cooling towers at a city hospital. An environmental isolate from these towers with an identical molecular pattern as the clinical isolates was subsequently identified and supported that epidemiologic conclusion.

  • Survival of Batrachochytrium dendrobatidis in Water: Quarantine and Disease Control Implications PDF Version [PDF - 249 KB - 4 pages]
    M. L. Johnson and R. Speare
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    Amphibian chytridiomycosis is an emerging infectious disease of amphibians thought to be moved between countries by trade in infected amphibians. The causative fungus, Batrachochytrium dendrobatidis, produces aquatic, motile zoospores; infections have been achieved in experiments by exposing amphibians to water containing zoospores. However, the ability of this fungus to survive in the environment in the absence of an amphibian host is unknown. We show that B. dendrobatidis will survive in tap water and in deionized water for 3 and 4 weeks, respectively. In lake water, infectivity was observed for 7 weeks after introduction. The knowledge that water can remain infective for up to 7 weeks is important for the formulation of disease control and quarantine strategies for the management of water that has been in contact with amphibians.

  • Enzootic Transmission of Yellow Fever Virus in Peru PDF Version [PDF - 427 KB - 8 pages]
    J. E. Bryant et al.
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    The prevailing paradigm of yellow fever virus (YFV) ecology in South America is that of wandering epizootics. The virus is believed to move from place to place in epizootic waves involving monkeys and mosquitoes, rather than persistently circulating within particular locales. After a large outbreak of YFV illness in Peru in 1995, we used phylogenetic analyses of virus isolates to reexamine the hypothesis of virus movement. We sequenced a 670-nucleotide fragment of the prM/E gene region of from 25 Peruvian YFV samples collected from 1977 to 1999, and delineated six clades representing the states (Departments) of Puno, Pasco, Junin, Ayacucho, San Martin/Huanuco, and Cusco. The concurrent appearance of at least four variants during the 1995 epidemic and the genetic stability of separate virus lineages over time, indicate that Peruvian YFV is locally maintained and circulates continuously in discrete foci of enzootic transmission.

  • Molecular Analysis of Echovirus 13 Isolates and Aseptic Meningitis, Spain PDF Version [PDF - 366 KB - 8 pages]
    A. Avellón et al.
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    Echovirus 13 (EV13), considered rare, was reported worldwide in 2000, mostly related to aseptic meningitis outbreaks. In Spain, 135 EV13 isolates were identified. The genetic relationships between 64 representative strains from Spain and other reported isolates from the United States, Germany, Italy, Japan, and Sweden were described by analyzing the partial sequence of the major capsid protein (VP1) gene. The strains from Spain were clearly identified as EV13 (79.5% similarity with the EV13 reference strain) and were grouped phylogenetically into two different clusters (by origination on either the Iberian Peninsula or Canary Islands). Isolates from Germany from 2000 clustered with the Canary Islands group. The isolates from other countries obtained before 2000 were genetically distant. Changes in EV13 coding sequence involved several differences in the C-terminal extreme of the VP1 protein. Part of the neutralizing antigenic site III has been described in this genome region in poliovirus and swine vesicular disease virus.

  • Molecular Characterization of a Non–Babesia divergens Organism Causing Zoonotic Babesiosis in Europe PDF Version [PDF - 286 KB - 6 pages]
    B. L. Herwaldt et al.
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    In Europe, most reported human cases of babesiosis have been attributed, without strong molecular evidence, to infection with the bovine parasite Babesia divergens. We investigated the first known human cases of babesiosis in Italy and Austria, which occurred in two asplenic men. The complete 18S ribosomal RNA (18S rRNA) gene was amplified from specimens of their whole blood by polymerase chain reaction (PCR). With phylogenetic analysis, we compared the DNA sequences of the PCR products with those for other Babesia spp. The DNA sequences were identical for the organism from the two patients. In phylogenetic analysis, the organism clusters with B. odocoilei, a parasite of white-tailed deer; these two organisms form a sister group with B. divergens. This evidence indicates the patients were not infected with B. divergens but with an organism with previously unreported molecular characteristics for the 18S rRNA gene.

  • Severe Tungiasis in Underprivileged Communities: Case Series from Brazil PDF Version [PDF - 306 KB - 7 pages]
    H. Feldmeier et al.
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    Tungiasis is caused by infestation with the sand flea (Tunga penetrans). This ectoparasitosis is endemic in economically depressed communities in South American and African countries. Tungiasis is usually considered an entomologic nuisance and does not receive much attention from healthcare professionals. During a study on tungiasis-related disease in an economically depressed area in Fortaleza, northeast Brazil, we identified 16 persons infested with an extremely high number of parasites. These patients had >50 lesions each and showed signs of intense acute and chronic inflammation. Superinfection of the lesions had led to pustule formation, suppuration, and ulceration. Debilitating sequelae, such as loss of nails and difficulty in walking, were constant. In economically depressed urban neighborhoods characterized by a high transmission potential, poor housing conditions, social neglect, and inadequate healthcare behavior, tungiasis may develop into severe disease.

  • Pseudomonas aeruginosa and the Oropharyngeal Ecosystem of Tube-Fed Patients PDF Version [PDF - 322 KB - 4 pages]
    A. Leibovitz et al.
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    We evaluated whether elderly patients fed with nasogastric tubes (NGT) are predisposed to Pseudomonas aeruginosa colonization in the oropharynx. Fifty-three patients on NGT feeding and 50 orally fed controls with similar clinical characteristics were studied. The tongue dorsum was swabbed and cultured. P. aeruginosa was isolated in 18 (34%) of the NGT-fed group but in no controls (p<0.001). Other gram-negative bacteria were cultured from 34 (64%) of NGT-fed patients as compared with 4 (8%) of controls (p<0.001). Antibiotic susceptibility of the oropharyngeal P. aeruginosa isolates was compared with that of isolates from sputum cultures obtained from our hospital’s bacteriologic laboratory. The oropharyngeal isolates showed a higher rate of resistance; differences were significant for amikacin (p<0.03). Scanning electron microscope studies showed a biofilm containing P. aeruginosa organisms. The pulsed-field gel electrophoresis profile of these organisms was similar to that of P. aeruginosa isolates from the oropharynx. NGT-fed patients may serve as vectors of resistant P. aeruginosa strains.

  • Nonmalarial Infant Deaths and DDT Use for Malaria Control PDF Version [PDF - 192 KB - 5 pages]
    A. Chen and W. J. Rogan
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    Although dichlorodiphenyl trichloroethane (DDT) is being banned worldwide, countries in sub-Saharan Africa have sought exemptions for malaria control. Few studies show illness in children from the use of DDT, and the possibility of risks to them from DDT use has been minimized. However, plausible if inconclusive studies associate DDT with more preterm births and shorter duration of lactation, which raise the possibility that DDT does indeed have such toxicity. Assuming that these associations are causal, we estimated the increase in infant deaths that might result from DDT spraying. The estimated increases are of the same order of magnitude as the decreases from effective malaria control. Unintended consequences of DDT use need to be part of the discussion of modern vector control policy.

  • Multidrug-Resistant Tuberculosis in HIV-Negative Patients, Buenos Aires, Argentina PDF Version [PDF - 235 KB - 5 pages]
    D. Palmero et al.
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    Initial multidrug-resistant (MDR) tuberculosis (TB) in HIV-negative patients treated at a Buenos Aires referral hospital from 1991 to 2000 was examined by using molecular clustering of available isolates. Of 291 HIV-negative MDRTB patients, 79 were initially MDR. We observed an ascending trend of initial MDRTB during this decade (p=0.0033). The M strain, which was responsible for an institutional AIDS-associated outbreak that peaked in 1995 to 1997, caused 24 of the 49 initial MDRTB cases available for restriction fragment length polymorphism. Of those, 21 were diagnosed in 1997 or later. Hospital exposure increased the risk of acquiring M strain–associated MDRTB by approximately two and a half times. The emergence of initial MDRTB among HIV-negative patients after 1997 was apparently a sequel of the AIDS-related outbreak. Because the prevalence of M strain–associated disease in the study population did not level out by the end of the decade, further expansion of this disease is possible.

  • Invasive Group A Streptococcal Disease: Risk Factors for Adults PDF Version [PDF - 279 KB - 8 pages]
    S. H. Factor et al.
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    We conducted a case-control study to identify risk factors for invasive group A streptococcal (GAS) infections, which can be fatal. Case-patients were identified when Streptoccus pyogenes was isolated from a normally sterile site and control subjects (two or more) were identified and matched to case-patients by using sequential-digit telephone dialing. All participants were noninstitutionalized surveillance area residents, >18 years of age. Conditional logistic regression identified the risk factors for invasive GAS infection: in adults 18 to 44 years of age, exposure to one or more children with sore throats (relative risk [RR]=4.93, p=0.02), HIV infection (RR =15.01, p=0.04), and history of injecting drug use (RR=14.71, p=0.003); in adults >45 years of age, number of persons in the home (RR=2.68, p=0.004), diabetes (RR= 2.27, p=0.03), cardiac disease (RR=3.24, p=0.006), cancer (RR= 3.54, p=0.006), and corticosteroid use (RR=5.18, p=0.03). Thus, host and environmental factors increased the risk for invasive GAS disease.

  • Community-Acquired Methicillin-Resistant Staphylococcus aureus Carrying Panton-Valentine Leukocidin Genes: Worldwide Emergence PDF Version [PDF - 353 KB - 7 pages]
    F. Vandenesch et al.
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    Infections caused by community-acquired (CA)-methicillin resistant Staphylococcus aureus (MRSA) have been reported worldwide. We assessed whether any common genetic markers existed among 117 CA-MRSA isolates from the United States, France, Switzerland, Australia, New Zealand, and Western Samoa by performing polymerase chain reaction for 24 virulence factors and the methicillin-resistance determinant. The genetic background of the strain was analyzed by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The CA-MRSA strains shared a type IV SCCmec cassette and the Panton-Valentine leukocidin locus, whereas the distribution of the other toxin genes was quite specific to the strains from each continent. PFGE and MLST analysis indicated distinct genetic backgrounds associated with each geographic origin, although predominantly restricted to the agr3 background. Within each continent, the genetic background of CA-MRSA strains did not correspond to that of the hospital-acquired MRSA.

  • Candidemia in Finland, 1995–1999 PDF Version [PDF - 343 KB - 6 pages]
    E. Poikonen et al.
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    We analyzed laboratory-based surveillance candidemia data from the National Infectious Disease Register in Finland and reviewed cases of candidemia from one tertiary-care hospital from 1995 to 1999. A total of 479 candidemia cases were reported to the Register. The annual incidence rose from 1.7 per 100,000 population in 1995 to 2.2 in 1999. Species other than Candida albicans accounted for 30% of cases without change in the proportion. A total of 79 cases of candidemia were identified at the hospital; the rate varied from 0.03 to 0.05 per 1,000 patient-days by year. Predisposing factors included indwelling catheters (81%), gastrointestinal surgery (27%), hematologic malignancy (25%), other types of surgery (21%), and solid malignancies (20%). Crude 7-day and 30-day case-fatality ratios were 15% and 35%, respectively. The rate of candidemia increased in Finland but is still substantially lower than in the United States. No shift to non–C. albicans species could be detected.

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