Xunde Li

Publications (12)35.14 Total impact

• Article: Multiple unique Cryptosporidium isolates from three species of ground squirrels (Spermophilus beecheyi, S. beldingi, and S. lateralis) in California.

  Maria das Graças Cabral Pereira, Xunde Li, Brenda McCowan, Ralph L Phillips, Edward R Atwill
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  ABSTRACT: Phylogenetic analyses of the 18S small-subunit (SSU) rRNA and Cryptosporidium oocyst wall protein (COWP) genes indicate that multiple unique Cryptosporidium isolates are shed by separate species of Spermophilus ground squirrels (S. beecheyi, S. beldingi, and S. lateralis) throughout California, despite some squirrel populations' being geographically isolated. The data support our assertion that Spermophilus squirrels shed novel Cryptosporidium species.
  Applied and environmental microbiology 10/2010; 76(24):8269-76. · 3.69 Impact Factor
• Article: Effect of daily temperature fluctuation during the cool season on the infectivity of Cryptosporidium parvum.

  Xunde Li, Edward R Atwill, Lissa A Dunbar, Kenneth W Tate
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  ABSTRACT: The present work calculated the rate of inactivation of Cryptosporidium parvum oocysts attributable to daily oscillations of low ambient temperatures. The relationship between air temperature and the internal temperature of bovine feces on commercial operations was measured, and three representative 24-h thermal regimens in the approximately 15 degrees C, approximately 25 degrees C, and approximately 35 degrees C ranges were chosen and emulated using a thermocycler. C. parvum oocysts suspended in deionized water were exposed to the temperature cycles, and their infectivity in mice was tested. Oral inoculation of 10(3) treated oocysts per neonatal BALB/c mouse (approximately 14 times the 50% infective dose) resulted in time- and temperature-dependent reductions in the proportion of infected mice. Oocysts were completely noninfectious after 14 24-h cycles with the 30 degrees C regimen and after 70 24-h cycles with the 20 degrees C regimen. In contrast, oocysts remained infectious after 90 24-h cycles with the 10 degrees C regimens. The estimated numbers of days needed for a 1-log(10) reduction in C. parvum oocyst infectivity were 4.9, 28.7, and 71.5 days for the 30, 20, and 10 degrees C thermal regimens, respectively. The loss of infectivity of oocysts induced by these thermal regimens was due in part to partial or complete in vitro excystation.
  Applied and environmental microbiology 12/2009; 76(4):989-93. · 3.69 Impact Factor
• Article: [Human cryptosporidiosis and Cryptosporidium spp. in Haiti].

  Christian P Raccurt, Philippe Brasseur, Rose I Verdier, Xunde Li, Etna Eyma, Christine Pannier Stockman, Patrice Agnamey, Karine Guyot, Anne Totet, Bernard Liautaud, Gilles Nevez, Eduardo Dei-Cas, Jean W Pape
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  ABSTRACT: Contamination by water-born infectious diseases is closely linked to urban slums conditions such as overcrowding and high level of faecal pollution by animal and human excreta. In this environment, cryptosporidiosis is a major cause of acute diarrhoea in children and chronic persistent diarrhoea in AIDS patients, resulting in increased morbidity and mortality in both populations. The aims of this study conducted in Port-au-Prince, Haiti were to: (i) determine the frequency of Cryptosporidium infection in two populations of patients with diarrhoea, children and AIDS patients, and the existence of Cryptosporidium carriage in healthy adults living in close contact with them; (ii) identify by molecular genotyping the Cryptosporidium species involved; and (iii) evaluate the viability of Cryptosporidium oocysts isolated from human stools. From January 2000 to January 2001, 158 of 1529 diarrhoea stool samples collected from 93 patients with diarrhoea, 57 adults followed at Centres GHESKIO and 36 children admitted at the University Hospital in Port-au-Prince contained Cryptosporidium oocysts (10.3%). The majority of adult patients (98%) were HIV-infected whereas the majority of children (81%) tested negative for HIV. Cryptosporidium was documented in only 1/102 healthy persons living in contact with Cryptosporidium infected patients and infection was with the same genotype as that of the contact patient. Among the 69 Cryptosporidium isolates studied for genotyping, three species were identified: C. hominis (59%), C. parvum (38%) and C. felis (3%). The two C. felis cases are the first reported from AIDS patients in the Caribbean. Most of the children regardless of their HIV status were infected with C. hominis (72%), whereas AIDS patients were more likely to be infected by either human or animal genotypes. These data confirm that immunocompromised individuals are susceptible to a wide range of Cryptosporidium spp. Viability of Cryptosporidium oocysts were determined in an experimental mouse model for 17/18 specimen studied including in 12/13 C. hominis, 4/4 C. parvum and 1/1 C. felis. Infectivity in newborn mice was found to be dose-dependent and more effective with C. parvum than the other two genotypes. Cryptosporidiosis remains a frequent hazard for both AIDS patients and young children in Haiti because of poor hygiene, particularly contaminated water and overcrowded conditions associated with urban slums.
  Tropical Medicine & International Health 07/2006; 11(6):929-34. · 2.80 Impact Factor
• Article: Cryptosporidiose humaine et espèces en cause en Haïti

  Christian P. Raccurt, Philippe Brasseur, Rose I. Verdier, Xunde Li, Etna Eyma, Christine Pannier Stockman, Patrice Agnamey, Karine Guyot, Anne Totet, Bernard Liautaud, Gilles Nevez, Eduardo Dei-Cas, Jean W. Pape
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  ABSTRACT: RésuméLa cryptosporidiose constitue un problème majeur de santé publique en Haïti. Pour évaluer son impact chez les patients atteints du SIDA et les sujets contacts, les enfants en bas âge, et pour déterminer les espèces en cause par génotypage, une étude a été menée à Port-au-Prince, incluant l’étude de la viabilité des oocystes éliminés dans les selles des patients. De janvier 2000 à janvier 2001, sur 1.529 selles diarrhéiques provenant de patients suivis dans les Centres GHESKIO et d'enfants hospitalisés à l'hôpital de l'Université d’État d’Haïti, 158 (10,3%) ont montré la présence d'oocystes de cryptosporidies. Chez ces malades, 56 adultes sur 57 (98%) et 7 enfants sur 36 (19%) étaient VIH-positifs. Chez 102 sujets contacts examinés, un seul a été dépisté porteur sain de cryptosporidies du même génotype que celui de l'isolat trouvé chez le malade VIH-positif. Le génotypage par biologie moléculaire de 69 isolats de cryptosporidies a identifié trois espèces: Cryptosporidium hominis (41), C. parvum (26) et C. felis (2). C'est la première fois qu'est rapportée dans la Caraïbe l'infestation de deux patients VIH-positifs par C. felis. Les enfants généralement non infectés par le VIH sont dans 72% des cas parasités par C. hominis. Les adultes VIH-positifs sont parasités aussi bien par le génotype humain que par les génotypes animaux. Sur 18 isolats de cryptosporidies étudiés à l'aide d'un modèle expérimental (souriceau nouveau-né), la viabilité des oocystes a été confirmée pour 17 d'entre eux (12 C. hominis, 4 C. parvum, 1 C. felis). Le pouvoir infestant est dose-dépendant et plus élevé avec C. parvum qu'avec les deux autres espèces. Au moins trois espèces de cryptosporidies circulent en Haïti où la population pauvre vit dans des conditions d'hygiène précaires, et utilise pour sa consommation une eau polluée notamment par des fèces d'origine humaine et animale, dans un tissu urbain surpeuplé où les animaux domestiques se déplacent en toute liberté.Human cryptosporidiosis and Cryptosporidium spp. in HaitiContamination by water-born infectious diseases is closely linked to urban slums conditions such as overcrowding and high level of faecal pollution by animal and human excreta. In this environment, cryptosporidiosis is a major cause of acute diarrhoea in children and chronic persistent diarrhoea in AIDS patients, resulting in increased morbidity and mortality in both populations. The aims of this study conducted in Port-au-Prince, Haiti were to: (i) determine the frequency of Cryptosporidium infection in two populations of patients with diarrhoea, children and AIDS patients, and the existence of Cryptosporidium carriage in healthy adults living in close contact with them; (ii) identify by molecular genotyping the Cryptosporidium species involved; and (iii) evaluate the viability of Cryptosporidium oocysts isolated from human stools. From January 2000 to January 2001, 158 of 1529 diarrhoea stool samples collected from 93 patients with diarrhoea, 57 adults followed at Centres GHESKIO and 36 children admitted at the University Hospital in Port-au-Prince contained Cryptosporidium oocysts (10.3%). The majority of adult patients (98%) were HIV-infected whereas the majority of children (81%) tested negative for HIV. Cryptosporidium was documented in only 1/102 healthy persons living in contact with Cryptosporidium infected patients and infection was with the same genotype as that of the contact patient. Among the 69 Cryptosporidium isolates studied for genotyping, three species were identified: C. hominis (59%), C. parvum (38%) and C. felis (3%). The two C. felis cases are the first reported from AIDS patients in the Caribbean. Most of the children regardless of their HIV status were infected with C. hominis (72%), whereas AIDS patients were more likely to be infected by either human or animal genotypes. These data confirm that immunocompromised individuals are susceptible to a wide range of Cryptosporidium spp. Viability of Cryptosporidium oocysts were determined in an experimental mouse model for 17/18 specimen studied including in 12/13 C. hominis, 4/4 C. parvum and 1/1 C. felis. Infectivity in newborn mice was found to be dose-dependent and more effective with C. parvum than the other two genotypes. Cryptosporidiosis remains a frequent hazard for both AIDS patients and young children in Haiti because of poor hygiene, particularly contaminated water and overcrowded conditions associated with urban slums.Las enfermedades infecciosas causadas por aguas contaminadas están estrechamente relacionadas con condiciones deficientes en la vivienda urbana, tales como la superpoblación o altos niveles de contaminación fecal por excrementos animales y humanos. En este medio, la criptoesporidiosis es una causa importante de diarrea aguda en niños y de diarrea crónica persistente en pacientes adultos con SIDA, resultando en una morbilidad y mortalidad aumentada para ambas poblaciones. El objetivo de este estudio, conducido en Port-au-Prince, Haiti, fue: 1) determinar la frecuencia de infección por Cryptosporidium en dos poblaciones de pacientes con diarrea, niños y pacientes con SIDA, y la existencia de adultos viviendo en contacto próximo con ellos que son portadores de Cryptosporidium; 2) identificar mediante genotipaje molecular las especies de Cryptosporidium involucradas; 3) evaluar la viabilidad de los oocitos de Cryptosporidium aislados de heces humanas. Entre Enero 2000 y Enero 2001, de 1,529 muestras fecales recolectadas a 93 pacientes con diarrea – 57 adultos bajo seguimiento en centros GHESKIO y 36 niños admitidos en el Hospital Universitario en Port-au-Prince, 158 contenían oocitos (10.3%). La mayoría de los pacientes adultos (98%) estaban infectados con VIH, mientras que la mayoría de los niños (81%) dieron negativos para la prueba de VIH. Se documentóCryptosporidium en solo 1/102 personas sanas que viviesen en contacto con pacientes infectados y en dicho caso, la infección era por un genotipo idéntico al del paciente contacto. Entre los 69 aislados de Cryptosporidium que se genotiparon, se identificaron tres especies como C. hominis (59%), C. parvum (38%) y C. felis (3%). Los dos casos de C. felis son los primeros en ser reportados en pacientes con SIDA en el Caribe. La mayoría de los niños, independientemente de su estatus de VIH, estaban infectados con C. hominis (72%), mientras que los pacientes con SIDA podían estar infectados con cualquiera de los genotipos, humano o animal. Estos datos confirman que los individuos inmunocomprometidos son susceptibles a un amplio rango de especies de Cryptosporidium. La viabilidad de los oocitos de Cryptosporidium se determinó mediante un modelo en ratón para 17/18 especimenes estudiados, incluyendo 12/13 C. hominis, 4/4 C. parvum y 1/1 C. felis. Se encontró que la infectividad en ratones recién nacidos era dosis-dependiente y más efectiva con C. parvum que con los otros genotipos. La Criptoesporidiosis continúan siendo un peligro frecuente tanto para pacientes con SIDA como para niños pequeños en Haiti, debido a una higiene deficiente y en particular a las aguas contaminadas y las condiciones de hacinamiento asociadas a las barriadas urbanas.
  Tropical Medicine & International Health 06/2006; 11(6):929 - 934. · 2.80 Impact Factor
• Article: Cryptosporidium oocysts in mussels (Mytilus edulis) from Normandy (France).

  Xunde Li, Karine Guyot, Eduardo Dei-Cas, Jean-Paul Mallard, Jean Jacques Ballet, Philippe Brasseur
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  ABSTRACT: Cultured mussels (Mytilus edulis) were collected seasonally during one year from three sites on the Northwestern coastal area of Normandy (France). Flesh, gills and innerwater were examined for Cryptosporidium oocyst detection using immunomagnetic separation and immunofluorescence assay. Oocysts were present in all samples for all sites and seasons and flesh was the most contaminated part. Oocyst rates were apparently related with seasonal rain precipitation variations. Molecular analysis revealed that oocysts belonged to the species Cryptosporidium parvum (formerly genotype 2 or ). Oocyst infectivity was assessed by oral administration to suckling NMRI-mice, and developmental stages were observed in only one mouse infected with oocysts from one location. The detection of potentially infectious C. parvum oocysts of likely cattle-breeding origin in cultured edible mussels confirms their resistance to sea environments, and underlines the potential risk of food-borne infection. This work reports for the first time the presence of infectious Cryptosporidium oocysts in shellfish from France.
  International Journal of Food Microbiology 05/2006; 108(3):321-5. · 3.33 Impact Factor
• Source

  Available from: usda.gov

  Article: Infectivity of microsporidian spores exposed to temperature extremes and chemical disinfectants.

  Xunde Li, Ronald Fayer
  Journal of Eukaryotic Microbiology 02/2006; 53 Suppl 1:S77-9. · 2.66 Impact Factor
• Source

  Available from: ucdavis.edu

  Article: Seasonal temperature fluctuations induces rapid inactivation of Cryptosporidium parvum.

  Xunde Li, Edward R Atwill, Lissa A Dunbar, Ted Jones, Jimmy Hook, Kenneth W Tate
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  ABSTRACT: This study measured the inactivation rate of bovine genotype A Cryptosporidium parvum oocysts attributable to diurnal oscillations of ambient temperature and solar radiation typical of California rangelands and dairies from spring through autumn. We first measured the relationship between air temperature and the internal temperature of bovine feces exposed to sunlight on commercial operations throughout California. Once maximum air temperature exceeded the mid 20 degrees C, diurnal thermal regimes of bovine fecal material exhibited peaks of over 40, 50, 60, and 70 degrees C. These diurnal thermal regimes were emulated using a thermocycler, with oocysts suspended in distilled water or fecal-water mix. Using oral inoculations of 10(5) C. parvum oocysts per neonatal Balb/c mouse (>1000-fold the ID50), no infections were observed using 1 to 5-day cycles of these thermal regimes. Loss of infectivity induced bythese thermal regimes was primarily due to partial or complete in vitro excystation during the first 24-h diurnal cycle and secondarily to thermal inactivation of the remaining intact or partial oocysts. These results suggest that as ambient conditions generate internal fecal temperatures > or = 40 degrees C via conduction, radiation, and convection, rapid environmental inactivation occurs at a rate of > or = 3.27 log reduction d(-1) for C. parvum oocysts deposited in the feces of cattle.
  Environmental Science and Technology 07/2005; 39(12):4484-9. · 5.23 Impact Factor
• Source

  Available from: ncbi.nlm.nih.gov

  Article: Seasonal shedding of multiple Cryptosporidium genotypes in California ground squirrels (Spermophilus beecheyi).

  Edward R Atwill, Ralph Phillips, Maria Das Graças C Pereira, Xunde Li, Brenda McCowan
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  ABSTRACT: Twelve percent of 853 California ground squirrels (Spermophilus beecheyi) from six different geographic locations in Kern County, Calif., were found to be shedding on average 44,482 oocysts g of feces(-1). The mean annual environmental loading rate of Cryptosporidium oocysts was 57,882 oocysts squirrel(-1) day(-1), with seasonal patterns of fecal shedding ranging from <10,000 oocysts squirrel(-1) day(-1) in fall, winter, and spring to levels of 2 x 10(5) oocysts squirrel(-1) day(-1) in summer. Juveniles were about twice as likely as adult squirrels to be infected and shed higher concentrations of oocysts than adults did, with particularly high levels of infection and shedding being found among juvenile male squirrels. Based on DNA sequencing of a portion of the 18S small-subunit rRNA gene, there existed three genotypes of Cryptosporidium species in these populations of squirrels (Sbey03a, Sbey03b, and Sbey03c; accession numbers AY462231 to AY462233, respectively). These unique DNA sequences were most closely related (96 to 97% homology) to porcine C. parvum (AF115377) and C. wrairi (AF115378). Inoculating BALB/c neonatal mice with up to 10,000 Sbey03b or Sbey03c fresh oocysts from different infected hosts did not produce detectable levels of infection, suggesting that this common genotype shed by California ground squirrels is not infectious for mice and may constitute a new species of Cryptosporidium.
  Applied and Environmental Microbiology 11/2004; 70(11):6748-52. · 3.83 Impact Factor
• Article: Time and temperature effects on the viability and infectivity of Cryptosporidium parvum oocysts in chlorinated tap water.

  Xunde Li, Philippe Brasseur, Patrice Agnamey, Jean Jacques Ballet, Chu Clemenceau
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  ABSTRACT: The authors compared the viability and infectivity of Cryptosporidium parvum oocysts in chlorinated tap water at various storage durations (i.e., 2 wk, 4 wk, 6 wk, or 8 wk) and at 2 cool temperatures (i.e., 10 degrees C and 4 degrees C), using in vitro (excystation) and in vivo (suckling mouse) methods. After 8 wk, mean oocyst excystation decreased to 33.4% and 26.7% at 10 degrees C and 4 degrees C, respectively. Suckling mice infectivity was higher after storage at 10 degrees C than after storage at 4 degrees C. These data suggest that Cryptosporidium parvum oocysts can survive and remain infectious for 8 wk in cool chlorinated tap water.
  Archives of Environmental Health An International Journal 10/2004; 59(9):462-6.
• Source

  Available from: cas.cz

  Article: Long-lasting anticryptosporidial activity of nitazoxanide in an immunosuppressed rat model.

  Xunde Li, Philippe Brasseur, Patrice Agnamey, Denis Leméteil, Loïc Favennec, Jean-Jacques Ballet, Jean-François Rossignol
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  ABSTRACT: Cryptosporidium parvum, Tyzzer, 1912 is identified as a common cause of diarrhoea in immunocompetent individuals. In immunocompromised, especially HIV-infected subjects, cryptosporidiosis causes severe chronic diarrhoea. In this study, nitazoxanide (NTZ) was compared for curative activity with sinefungin (SNF) and paromomycin (PRM) in immunosuppressed rats, a screening model for anticryptosporidial agents. NTZ at either 50 mg/kg/day, 100 mg/kg/day or 200 mg/kg/day resulted in seven days in a dose-dependent inhibition of oocyst shedding similar to that obtained with SNF (10 mg/kg/day) and PRM (100 mg/kg/day). Further discontinuation of SNF or PRM 100 mg/kg/day therapy resulted in early relapse of oocyst shedding which reached the pre-treatment levels in 2-4 days. In contrast, seven days after discontinuation of therapy, shedding inhibition was unchanged in NTZ-treated rats. Data prompt further assessment of the activity of NTZ on sequestered C. parvum.
  Folia parasitologica 04/2003; 50(1):19-22. · 1.81 Impact Factor
• Article: Detection of Encephalitozoon hellem in feces of experimentally infected chickens.

  Ronald Fayer, Monica Santin, Robert Palmer, Xunde Li
  Journal of Eukaryotic Microbiology 02/2003; 50 Suppl:574-5. · 2.66 Impact Factor
• Article: Efficiency for recovering Encephalitozoon intestinalis spores from waters by centrifugation and immunofluorescence microscopy.

  Xunde Li, Kenneth W Tate, Lissa A Dunbar, Betsy Huang, Edward R Atwill
  Journal of Eukaryotic Microbiology 02/2003; 50 Suppl:579-80. · 2.66 Impact Factor