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Volume 11, Number 12—December 2005

Volume 11, Number 12—December 2005   PDF Version [PDF - 8.42 MB - 187 pages]

Perspective

  • Role of Multisector Partnerships in Controlling Emerging Zoonotic Diseases PDF Version [PDF - 34 KB - 2 pages]
    N. Marano et al.
  • Community Epidemiology Framework for Classifying Disease Threats PDF Version [PDF - 248 KB - 7 pages]
    A. Fenton and A. B. Pedersen
    View Summary

    Ecologic and evolutionary features of multihost pathogens determine the likelihood of emerging infectious diseases.

       View Abstract

    Recent evidence suggests that most parasites can infect multiple host species and that these are primarily responsible for emerging infectious disease outbreaks in humans and wildlife. However, the ecologic and evolutionary factors that constrain or facilitate such emergences are poorly understood. We propose a conceptual framework based on the pathogen's between- and within-species transmission rates to describe possible configurations of a multihost-pathogen community that may lead to disease emergence. We establish 3 dynamic thresholds separating 4 classes of disease outcomes, spillover, apparent multihost, true multihost, and potential emerging infectious disease; describe possible disease emergence scenarios; outline the population dynamics of each case; and clarify existing terminology. We highlight the utility of this framework with examples of disease threats in human and wildlife populations, showing how it allows us to understand which ecologic factors affect disease emergence and predict the impact of host shifts in a range of disease systems.

  • Bushmeat Hunting, Deforestation, and Prediction of Zoonotic Disease PDF Version [PDF - 122 KB - 6 pages]
    N. D. Wolfe et al.
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    Integrating virology, ecology, and other disciplines enhances prediction of new emerging zoonoses.

       View Abstract

    Understanding the emergence of new zoonotic agents requires knowledge of pathogen biodiversity in wildlife, human-wildlife interactions, anthropogenic pressures on wildlife populations, and changes in society and human behavior. We discuss an interdisciplinary approach combining virology, wildlife biology, disease ecology, and anthropology that enables better understanding of how deforestation and associated hunting leads to the emergence of novel zoonotic pathogens.

  • Human Granulocytic Anaplasmosis and Anaplasma phagocytophilum PDF Version [PDF - 214 KB - 7 pages]
    J. Dumler et al.
    View Summary

    Understanding how Anaplasma phagocytophilum alters neutrophils will improve diagnosis, treatment, and prevention of this severe illness.

       View Abstract

    Human granulocytic anaplasmosis is a tickborne rickettsial infection of neutrophils caused by Anaplasma phagocytophilum. The human disease was first identified in 1990, although the pathogen was defined as a veterinary agent in 1932. Since 1990, US cases have markedly increased, and infections are now recognized in Europe. A high international seroprevalence suggests infection is widespread but unrecognized. The niche for A. phagocytophilum, the neutrophil, indicates that the pathogen has unique adaptations and pathogenetic mechanisms. Intensive study has demonstrated interactions with host-cell signal transduction and possibly eukaryotic transcription. This interaction leads to permutations of neutrophil function and could permit immunopathologic changes, severe disease, and opportunistic infections. More study is needed to define the immunology and pathogenetic mechanisms and to understand why severe disease develops in some persons and why some animals become long-term permissive reservoir hosts.

Synopses

  • Francisella tularensis in the United States PDF Version [PDF - 547 KB - 7 pages]
    J. Farlow et al.
    View Summary

    Subpopulations A.I and A.II. of Francisella tularensis subsp. tularensis are associated with unique biotic and abiotic factors that maintain disease foci.

       View Abstract

    The causative agent of tularemia, Francisella tularensis, is a formidable biologic agent that occurs naturally throughout North America. We examined genetic and spatial diversity patterns among 161 US F. tularensis isolates by using a 24-marker multiple-locus variable-number tandem repeat analysis (MLVA) system. MLVA identified 126 unique genotypes. Phylogenetic analyses showed patterns similar to recently reported global-scale analyses. We observed clustering by subspecies, low genetic diversity within F. tularensis subsp. holarctica, and division of F. tularensis subsp. tularensis into 2 distinct subpopulations: A.I. and A.II. The 2 F. tularensis subsp. tularensis subpopulations also represent geographically distinct groups; A.I. occurs primarily in the central United States, and A.II. occurs primarily in the western United States. These spatial distributions are correlated with geographic ranges of particular vectors, hosts of tularemia, and abiotic factors. These correlates provide testable hypotheses regarding ecologic factors associated with maintaining tularemia foci.

Research

  • Host Range and Emerging and Reemerging Pathogens PDF Version [PDF - 236 KB - 6 pages]
    M. Woolhouse and S. Gowtage-Sequeria
    View Summary

    Emerging and reemerging species of human pathogens are associated with a broad range of nonhuman hosts.

       View Abstract

    An updated literature survey identified 1,407 recognized species of human pathogen, 58% of which are zoonotic. Of the total, 177 are regarded as emerging or reemerging. Zoonotic pathogens are twice as likely to be in this category as are nonzoonotic pathogens. Emerging and reemerging pathogens are not strongly associated with particular types of nonhuman hosts, but they are most likely to have the broadest host ranges. Emerging and reemerging zoonoses are associated with a wide range of drivers, but changes in land use and agriculture and demographic and societal changes are most commonly cited. However, although zoonotic pathogens do represent the most likely source of emerging and reemerging infectious disease, only a small minority have proved capable of causing major epidemics in the human population.

  • Person-to-Person Transmission of Andes Virus PDF Version [PDF - 168 KB - 6 pages]
    V. P. Martinez et al.
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    Epidemiologic and genetic data show that person-to-person spread likely took place during the prodromal phase or shortly after it ended.

       View Abstract

    Despite the fact that rodents are considered to be the infectious source of hantavirus for humans, another route of transmission was demonstrated. Andes virus (ANDV) has been responsible for most of the cases recorded in Argentina. Person-to-person transmission of ANDV Sout lineage was described during an outbreak of hantavirus pulmonary syndrome in southwest Argentina. In this study, we analyzed 4 clusters that occurred in 2 disease-endemic areas for different ANDV lineages. We found new evidence of interhuman transmission for ANDV Sout lineage and described the first event in which another lineage, ANDV Cent BsAs, was implicated in this mechanism of transmission. On the basis of epidemiologic and genetic data, we concluded that person-to-person spread of the virus likely took place during the prodromal phase or shortly after it ended, since close and prolonged contact occurred in the events analyzed here, and the incubation period was 15–24 days.

  • European Bat Lyssaviruses, the Netherlands PDF Version [PDF - 308 KB - 6 pages]
    W. Van der Poel et al.
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    Genotype 5 lyssaviruses are endemic in the Netherlands, and can cause fatal infections in humans.

       View Abstract

    To study European bat lyssavirus (EBLV) in bat reservoirs in the Netherlands, native bats have been tested for rabies since 1984. For all collected bats, data including species, age, sex, and date and location found were recorded. A total of 1,219 serotine bats, Eptesicus serotinus, were tested, and 251 (21%) were positive for lyssavirus antigen. Five (4%) of 129 specimens from the pond bat, Myotis dasycneme, were positive. Recently detected EBLV RNA segments encoding the nucleoprotein were sequenced and analyzed phylogenetically (45 specimens). All recent serotine bat specimens clustered with genotype 5 (EBLV1) sequences, and homologies within subgenotypes EBLV1a and EBLV1b were 99.0%–100% and 99.2%–100%, respectively. Our findings indicate that EBLVs of genotype 5 are endemic in the serotine bat in the Netherlands. Since EBLVs can cause fatal infections in humans, all serotine and pond bats involved in contact incidents should be tested to determine whether the victim was exposed to EBLVs.

  • SARS-CoV Infection in a Restaurant from Palm Civet PDF Version [PDF - 189 KB - 6 pages]
    M. Wang et al.
    View Summary

    Contact with food animals was associated with SARS-CoV infection in the People’s Republic of China.

       View Abstract

    Epidemiologic investigations showed that 2 of 4 patients with severe acute respiratory syndrome (SARS) identified in the winter of 2003–2004 were a waitress at a restaurant in Guangzhou, China, that served palm civets as food and a customer who ate in the restaurant a short distance from animal cages. All 6 palm civets at the restaurant were positive for SARS-associated coronavirus (SARS-CoV). Partial spike (S) gene sequences of SARS-CoV from the 2 patients were identical to 4 of 5 S gene viral sequences from palm civets. Phylogenetic analysis showed that SARS-CoV from palm civets in the restaurant was most closely related to animal isolates. SARS cases at the restaurant were the result of recent interspecies transfer from the putative palm civet reservoir, and not the result of continued circulation of SARS-CoV in the human population.

  • Echinococcosis in Tibetan Populations, Western Sichuan Province, China PDF Version [PDF - 310 KB - 8 pages]
    L. Tiaoying et al.
    View Summary

    This area has the highest prevalences of both forms of this disease in the world.

       View Abstract

    We screened 3,199 people from Shiqu County, Sichuan Province, China, for abdominal echinococcosis (hydatid disease) by portable ultrasound combined with specific serodiagnostic tests. Both cystic echinococcosis (CE) (Echinococcus granulosus infection) and alveolar echinococcosis (AE) (E. multilocularis) were co-endemic in this area at the highest village prevalence values recorded anywhere in the world: 12.9% were infected with one or the other form (6.8% CE and 6.2% AE). Prevalences of both CE and AE were significantly higher in female than male patients and increased with the age of the person screened. Pastoral herdsmen were at highest risk for infection (prevalence 19.0%). Prevalence of CE varied in 5 townships from 0% to 12.1%, whereas AE prevalence ranged from 0% to 14.3%. Risk factors associated with both infections included the number of owned dogs, frequency of contact with dogs, and sources of drinking water.

  • Porcine Noroviruses Related to Human Noroviruses PDF Version [PDF - 390 KB - 8 pages]
    Q. Wang et al.
    View Summary

    Pigs may be reservoirs for human noroviruses, and porcine/human genogroup II recombinants could emerge.

       View Abstract

    Detection of genogroup II (GII) norovirus (NoV) RNA from adult pigs in Japan and Europe and GII NoV antibodies in US swine raises public health concerns about zoonotic transmission of porcine NoVs to humans, although no NoVs have been detected in US swine. To detect porcine NoVs and to investigate their genetic diversity and relatedness to human NoVs, 275 fecal samples from normal US adult swine were screened by reverse transcription–polymerase chain reaction with calicivirus universal primers. Six samples were positive for NoV. Based on sequence analysis of 3 kb on the 3´ end of 5 porcine NoVs, 3 genotypes in GII and a potential recombinant were identified. One genotype of porcine NoVs was genetically and antigenically related to human NoVs and replicated in gnotobiotic pigs. These results raise concerns of whether subclinically infected adult swine may be reservoirs of new human NoVs or if porcine/human GII recombinants could emerge.

  • Viral Load Distribution in SARS Outbreak PDF Version [PDF - 126 KB - 5 pages]
    C. Chu et al.
    View Summary

    Airborne transmission may have resulted in an outbreak of SARS in Hong Kong.

       View Abstract

    An unprecedented community outbreak of severe acute respiratory syndrome (SARS) occurred in the Amoy Gardens, a high-rise residential complex in Hong Kong. Droplet, air, contaminated fomites, and rodent pests have been proposed to be mechanisms for transmitting SARS in a short period. We studied nasopharyngeal viral load of SARS patients on admission and their geographic distribution. Higher nasopharyngeal viral load was found in patients living in adjacent units of the same block inhabited by the index patient, while a lower but detectable nasopharyngeal viral load was found in patients living further away from the index patient. This pattern of nasopharyngeal viral load suggested that airborne transmission played an important part in this outbreak in Hong Kong. Contaminated fomites and rodent pests may have also played a role.

  • Pandemic Strain of Foot-and-Mouth Disease Virus Serotype O PDF Version [PDF - 262 KB - 7 pages]
    N. J. Knowles et al.
    View Summary

    The PanAsia strain is spreading explosively in Asia and extending to parts of Africa and Europe.

       View Abstract

    A particular genetic lineage of foot-and-mouth disease virus (FMDV) serotype O, which we have named the PanAsia strain, was responsible for an explosive pandemic in Asia and extended to parts of Africa and Europe from 1998 to 2001. In 2000 and 2001, this virus strain caused outbreaks in the Republic of Korea, Japan, Russia, Mongolia, South Africa, the United Kingdom, Republic of Ireland, France, and the Netherlands, countries which last experienced FMD outbreaks decades before (ranging from 1934 for Korea to 1984 for the Netherlands). Although the virus has been controlled in all of these normally FMD-free or sporadically infected countries, it appears to be established throughout much of southern Asia, with geographically separated lineages evolving independently. A pandemic such as this is a rare phenomenon but demonstrates the ability of newly emerging FMDV strains to spread rapidly throughout a wide region and invade countries previously free from the disease.

  • Bartonella henselae in Porpoise Blood PDF Version [PDF - 48 KB - 5 pages]
    R. G. Maggi et al.
    View Summary

    DNA in porpoises suggests an emerging infectious disease in marine mammals.

       View Abstract

    We report detection of Bartonella henselae DNA in blood samples from 2 harbor porpoises (Phocoena phocoena). By using real-time polymerase chain reaction, we directly amplified Bartonella species DNA from blood of a harbor porpoise stranded along the northern North Carolina coast and from a preenrichment blood culture from a second harbor porpoise. The second porpoise was captured out of habitat (in a low-salinity canal along the northern North Carolina coast) and relocated back into the ocean. Subsequently, DNA was amplified by conventional polymerase chain reaction for DNA sequencing. The 16S–23S intergenic transcribed spacer region obtained from each porpoise was 99.8% similar to that of B. henselae strain San Antonio 2 (SA2), whereas both heme-binding phage-associated pap31 gene sequences were 100% homologous to that of B. henselae SA2. Currently, the geographic distribution, mode of transmission, reservoir potential, and pathogenicity of bloodborne Bartonella species in porpoises have not been determined.

  • Antimicrobial-drug Susceptibility of Human and Animal Salmonella Typhimurium, Minnesota, 1997–2003 PDF Version [PDF - 205 KB - 8 pages]
    S. D. Wedel et al.
    View Summary

    Food animals are likely the primary reservoir of resistant S. Typhimurium.

       View Abstract

    We compared antimicrobial resistance phenotypes and pulsed-field gel electrophoresis (PFGE) subtypes of 1,028 human and 716 animal Salmonella enterica serotype Typhimurium isolates from Minnesota from 1997 to 2003. Overall, 29% of human isolates were multidrug resistant. Predominant phenotypes included resistance to ampicillin, chloramphenicol or kanamycin, streptomycin, sulfisoxazole, and tetracycline (ACSSuT or AKSSuT). Most human multidrug-resistant isolates belonged to PFGE clonal group A, characterized by ACSSuT resistance (64%), or clonal group B, characterized by AKSSuT resistance (19%). Most animal isolates were from cattle (n = 358) or swine (n = 251). Eighty-one percent were multidrug resistant; of these, 54% were at least resistance phenotype ACSSuT, and 43% were at least AKSSuT. More than 80% of multidrug-resistant isolates had a clonal group A or B subtype. Resistance to ceftriaxone and nalidixic acid increased, primarily among clonal group A/ACSSuT isolates. Clonal group B/AKSSuT isolates decreased over time. These data support the hypothesis that food animals are the primary reservoir of multidrug-resistant S. Typhimurium.

  • Postepizootic Persistence of Venezuelan Equine Encephalitis Virus, Venezuela PDF Version [PDF - 218 KB - 9 pages]
    J. Navarro et al.
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    Etiologic subtype IC of virus persists, 5 years after the major 1995 epidemic.

       View Abstract

    Five years after the apparent end of the major 1995 Venezuelan equine encephalitis (VEE) epizootic/epidemic, focal outbreaks of equine encephalitis occurred in Carabobo and Barinas States of western Venezuela. Virus isolates from horses in each location were nearly identical in sequence to 1995 isolates, which suggests natural persistence of subtype IC VEE virus (VEEV) strains in a genetically stable mode. Serologic evidence indicated that additional outbreaks occurred in Barinas State in 2003. Field studies identified known Culex (Melanoconion) spp. vectors and reservoir hosts of enzootic VEEV but a dearth of typical epidemic vectors. Cattle serosurveys indicated the recent circulation of enzootic VEEV strains, and possibly of epizootic strains. Persistence of VEEV subtype IC strains and infection of horses at the end of the rainy season suggest the possibility of an alternative, cryptic transmission cycle involving survival through the dry season of infected vectors or persistently infected vertebrates.

  • Intergenogroup Recombination in Sapoviruses PDF Version [PDF - 386 KB - 7 pages]
    G. S. Hansman et al.
    View Summary

    This first report of intergenogroup recombination for any calicivirus highlights a possible route of zoonoses.

       View Abstract

    Sapovirus, a member of the family Caliciviridae, is an etiologic agent of gastroenteritis in humans and pigs. Analyses of the complete genome sequences led us to identify the first sapovirus intergenogroup recombinant strain. Phylogenetic analysis of the nonstructural region (i.e., genome start to capsid start) grouped this strain into genogroup II, whereas the structural region (i.e., capsid start to genome end) grouped this strain into genogroup IV. We found that a recombination event occurred at the polymerase and capsid junction. This is the first report of intergenogroup recombination for any calicivirus and highlights a possible route of zoonoses because sapovirus strains that infect pig species belong to genogroup III.

  • Rabies Postexposure Prophylaxis, New York, 1995–2000 PDF Version [PDF - 205 KB - 7 pages]
    J. D. Blanton et al.
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    Bats are now the leading source of rabies postexposure prophylaxis.

       View Abstract

    The epidemiology of human rabies postexposure prophylaxis (PEP) in 4 upstate New York counties was described from data obtained from 2,216 incidences of PEP recorded by local health departments from 1995 to 2000. Overall annual incidence for the study period was 27 cases per 100,000 persons. Mean annual PEP incidence rates were highest in rural counties and during the summer months. PEP incidence was highest among patients 5–9 and 30–34 years of age. Bites accounted for most PEP (51%) and were primarily associated with cats and dogs. Bats accounted for 30% of exposures, more than any other group of animals; consequently, bats have replaced raccoons as the leading rabies exposure source to humans in this area.

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