Molecular Epidemiological Tools Research Articles

Sequence analysis and genotyping of genital Chlamydia trachomatis among patients with suspected-Neisseria gonorrhoeae

Objective To understand the prevalence rate of genital Chlamydia trachomatis among a population with suspected-Neisseria gonorrhoeae infection,the distribution of Chlamydia trachomatis genotypes,assess changes in omp1 sequences among patients with Neisseria gonorrhoeae and Chlamydia trachomatis coinfections.Methods Four hundred and one swabs were collected.Chlamydia trachomatis and Neisseria gonorrhoeae were detected by Roche Amplicor System.DNA were extracted from those samples and were amplified by nested PCR.PCR products were sequencing and analyzed by software Mega4.0.Results The prevalence of genital Chlamydia trachomatis infection,Neisseria gonorrhoeae infection and coinfection with genital gonorrhoea and genital chlamydia were 82.3%,24.2% and 21.7% each.Eight genotypes were identified in 73 sequences,including E(27.4%),G/Ga(23.3%),D/Da(16.4%),F(13.7%),J (11.0%),H(5.5%),B and K(each 1.4%).Sequencing analysis showed that 3 cases(4.1%) had missense mutation,including genotype D/Da,E,G/Ga.Genotypes F,H,J and K were more variable,however,most of them were silent mutation.Conclusion The prevalence rate of genital Chlamydia trachomatis among a population with Neisseria gonorrhoeae infection was high.The most common genotypes were genotype E,G/Ga,D/Da and F; Sequencing analysis has provided a tool for the molecular epidemiology of genital Chlamydia trachomatis infections. Key words: Gonorrhea; Chlamydia trachomatis; Nested-PCR; Genotyping; Sequencing analysis

PCR-based amplification of heterogeneous IS257-ileS2 junctions for molecular monitoring of high-level mupirocin resistance in staphylococci

Plasmids encoding the ileS2 gene are responsible for the wide spread of high-level mupirocin resistance in staphylococci, and consequent clinical and epidemiological problems. We investigated the location of insertion sequence IS257 flanking ileS2 in different plasmids and developed a method for molecular typing of the IS257-ileS2 spacer regions. Nine ileS2-encoding plasmids (i.e. pPR1-pPR9) classified into distinct structural groups (i.e. S1-S4) were analysed. Complete DNA sequences between IS257s flanking ileS2 were determined. A PCR-based amplification scheme was designed for the simultaneous amplification of up- and down-stream IS257-ileS2 regions. The method was applied to a total of 90 high-level mupirocin-resistant clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). pPR1-pPR9 possessed IS257s flanking ileS2. Plasmids of each structural group showed a unique configuration of IS257-ileS2 spacer regions. The PCR-based method permitted accurate typing of the heterogeneous IS257-ileS2 up- and down-stream junctions, and the differentiation of plasmids of each group. The results obtained corresponded with previous plasmid typing based on restriction enzyme analyses and ileS2 locus hybridization polymorphs. The application of the PCR-based method to a diverse collection of MRSA isolates carrying ileS2-encoding plasmids demonstrated its versatility and revealed extraordinary heterogeneity in the IS257-ileS2 spacers. The devised PCR-based scheme offers a rapid, simple and effective approach for typing IS257-ileS2 configurations present on ileS2-encoding plasmids. Hopefully, it could serve as a useful molecular epidemiological tool to control high-level mupirocin resistance.

An overview of rabies - history, epidemiology, control and possible elimination.

Rabies remains the most important zoonotic disease in many countries. Public concern and fears are most focused on dogs as the source of rabies infection to humans and other domestic animals. Several bat species are reservoir hosts of rabies and therefore can be a public health hazard. The possibility of a carrier state or asymptomatic form of rabies deserves serious evaluation. Rabies in most countries was successfully controlled through mass vaccination of dogs, long before the recognition of bat and other wildlife rabies and the availability of modern vaccines. Though, the epidemiology, virology, transmission, pathology, clinical manifestations, diagnosis, treatment and control of rabies infection have been described extensively, the incidence is increasingly on the high side. However, experts have recognized for decades that rabies is wholly eradicable from all species except bats through targeted mass immunization, and the chief obstacle to eradicating rabies especially in bats is that no one has developed an aerosolized vaccine that could be sprayed into otherwise inaccessible caves and tree trunks. Inventing such a vaccine is considered difficult but possible. Forestalling this problem will require active epidemiological surveillance of wild and domestic animals with a wide range of modern molecular and ancillary epidemiological tools. This also demands government and private sector intervention, funding and collaboration of professionals in human and veterinary medicine with those in the environmental sciences. Recently, the heroic recovery of an unvaccinated teenager from clinical rabies offers hope of future specific therapy. While post-exposure vaccination is essential and should be continued with improvement to achieve consistently positive results, progress toward eliminating rabies has been markedly faster in nations that have emphasized preventive vaccination of animals. Key words: Control, epidemiology, history, mass vaccination, surveillance, zoonotic disease.

Longitudinal Phylogenetic Surveillance Identifies Distinct Patterns of Cluster Dynamics

Through the application of simple, accessible, molecular epidemiology tools, we aimed to resolve the phylogenetic relationships that best predicted patterns of cluster growth using longitudinal population level drug resistance genotype data. Analysis was performed on 971 specimens from drug naïve, first time HIV positive subjects collected in British Columbia between 2002 and 2005. A 1240bp fragment of the pol gene was amplified and sequenced with relationships among subtype B sequences inferred using Neighbour-Joining analysis. Apparent clusters of infections having both a mean within group distance <0.031 and bootstrap value >80% were systematically identified. The entire 2002-2005 dataset was then re-analyze to evaluate the relationship of subsequent infections to those identified in 2002. BED testing was used to identify recent infections (<156 days). Among the 2002 infections, 136 of 300 sequences sorted into 52 clusters ranging in size from 2 to 9 members. Aboriginal ethnicity and intravenous drug use were correlated, and both were linked to cluster membership in 2002. Although cluster growth between 2002 and 2005 was correlated with the size of the original cluster, more related infections were found in clusters seeded from nonclustered infections. Finally, all large growth clusters were seeded from infections that were much more likely to be recent. This population level phylogenetic analysis suggests that a greater increase in cluster size is associated with recently infected individuals, which may represent the leading edge of the epidemic. The most impressive increase in cluster size is seen originating from initially nonclustered infections. In contrast, smaller existing clusters likely describe historical patterns of transmission and do not substantially contribute to the ongoing epidemic. Application of this method for cross-sectional analysis of existing sequences from defined geographic regions may be useful in predicting trends in HIV transmission.

Epidemiology and etiology of meningioma

Although most meningiomas are encapsulated and benign tumors with limited numbers of genetic aberrations, their intracranial location often leads to serious and potentially lethal consequences. They are the most frequently diagnosed primary brain tumor accounting for 33.8% of all primary brain and central nervous system tumors reported in the United States between 2002 and 2006. Inherited susceptibility to meningioma is suggested both by family history and candidate gene studies in DNA repair genes. People with certain mutations in the neurofibromatosis gene (NF2) have a very substantial increased risk for meningioma. High dose ionizing radiation exposure is an established risk factor for meningioma, and lower doses may also increase risk, but which types and doses are controversial or understudied. Because women are twice as likely as men to develop meningiomas and these tumors harbor hormone receptors, an etiologic role for hormones (both endogenous and exogenous) has been hypothesized. The extent to which immunologic factors influence meningioma etiology has been largely unexplored. Growing emphasis on brain tumor research coupled with the advent of new genetic and molecular epidemiologic tools in genetic and molecular epidemiology promise hope for advancing knowledge about the causes of intra-cranial meningioma. In this review, we highlight current knowledge about meningioma epidemiology and etiology and suggest future research directions.

Use of FTA Cards for Direct Sampling of Patients' Lesions in the Ecological Study of Cutaneous Leishmaniasis

The FTA card (Whatman) was assessed for its utility as a molecular epidemiological tool in collecting samples from patients with leishmaniasis in Peru because the card has a variety of merits; it is less invasive for patients and easy to handle for both physicians and other medical personnel for sample collection or diagnosis, in addition to its simplicity and easy countrywide and/or intercountry transportation for analysis. Samples were collected from 132 patients suspected of having leishmaniasis, and Leishmania species were successfully identified in samples from 81 patients in 15 departments of Peru by cytochrome b and mannose phosphate isomerase gene analyses. Of these, 61.7% were identified as Leishmania (Viannia) peruviana, 22.2% as L. (V.) braziliensis, 12.3% as L. (V.) guyanensis, 2.5% as L. (V.) shawi, and 1.2% as L. (V.) lainsoni. The three predominant species, L. (V.) peruviana, L. (V.) braziliensis, and L. (V.) guyanensis, were mainly found in the Andean highlands, in the tropical rainforest, and in northern and central rainforest regions, respectively. This is the first time L. (V.) shawi has been identified outside Brazil. The present study showed that the FTA card will be a useful tool for the ecological study of different forms of leishmaniasis. Furthermore, collecting samples directly from patients' lesions by using the FTA card eliminates (i) the possibility of contamination of Leishmania isolates during short- and/or long-term passages of culture in vitro in each laboratory and (ii) pain and suffering of patients from taking samples by skin biopsy.

Efficient DNA Extraction from Nail Clippings Using the Protease Solution from Cucumis melo

Owing to the increasing importance of genomic information, obtaining genomic DNA easily from biological specimens has become more and more important. This article proposes an efficient method for obtaining genomic DNA from nail clippings. Nail clippings can be easily obtained, are thermostable and easy to transport, and have low infectivity. The drawback of their use, however, has been the difficulty of extracting genomic material from them. We have overcome this obstacle using the protease solution obtained from Cucumis melo. The keratinolytic activity of the protease solution was 1.78-fold higher than that of proteinase K, which is commonly used to degrade keratin. With the protease solution, three times more DNA was extracted than when proteinase K was used. In order to verify the integrity of the extracted DNA, genotype analysis on 170 subjects was performed by both PCR-RFLP and Real Time PCR. The results of the genotyping showed that the extracted DNA was suitable for genotyping analysis. In conclusion, we have developed an efficient extraction method for using nail clippings as a genome source and a research tool in molecular epidemiology, medical diagnostics, and forensic science.

Mycoplasma pneumonia: Clinical features and management

Mycoplasma pneumonia is a common respiratory pathogen that produces diseases of varied severity ranging from mild upper respiratory tract infection to severe atypical pneumonia. Apart from respiratory tract infections, this organism is also responsible for producing a wide spectrum of non-pulmonary manifestations including neurological, hepatic, cardiac diseases, hemolytic anemia, polyarthritis and erythema multiforme. This review focuses on molecular taxonomy, biological characteristics, epidemiology, clinical presentation, radiology and various laboratory tools in diagnosis, differential diagnosis, treatment and prevention of mycoplasma pneumonia.

Environmental Exposures and Adult Brain Cancers

ISEE-0357 Background: Adult gliomas continue to be aggressive with few known risk factors. This work focuses on assessing the risk of human exposures to animal neurocarcinogens in a case-control study. Methods: An environmental questionnaire was constructed to assess human exposures to animal neurocarcinogens. Information including primary glioma cases (n = 111) and friend controls (n = 197) were obtained from two centers: Evanston Northwestern Healthcare and Duke University Medical Center. Data were obtained using a web-based survey allowing participants to work at their leisure. Chemical-specific exposure scores were constructed from a composite of questions. Preliminary analyses were conducted using conditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals for ordinal values of exposure scores, controlling for age and gender. Results: Three compounds with ORs greater than 2.0 were identified: bis(chloromethyl) ether (P = 0.15), vinyl chloride (P = 0.09) and propylene imine (P = 0.02). Vinyl chloride and propylene imine exposure score ORs became larger in subjects without a history of asthma/allergies. Comparing the highest to the lowest tertile of the vinyl chloride score, an OR of 4.5 (95%CI: 0.9–23) was estimated (P = 0.07). As the propylene imine score was based on a limited set of questions, this score may be of limited validity. The odds ratios for several chemical scores (acrylamide, acrylonitrile, ethylene oxide, NOCs, glycidol, and 3,3-dimethylbenzidine hydrochloride) were elevated but unstable in the presence of asthma/allergy history, suggesting that a complex relationship may be present between environmental exposures and conditions affecting immune function. Conclusions: Chemical exposure indices based on questionnaires of environmental exposures have limitations; however, they are useful in setting priorities for future research focusing on biomarkers of exposure and other molecular epidemiology tools.

結核集団感染事例における分子疫学的解析法としてのVariable Numbers of Tandem Repeats法の検討

結核集団感染事例における分子疫学的解析法としてのVariable Numbers of Tandem Repeats法の検討

Infections caused by Gram-positive bacteria: a review of the global challenge

Infections caused by multidrug-resistant Gram-positive bacteria represent a major public health burden, not just in terms of morbidity and mortality, but also in terms of increased expenditure on patient management and implementation of infection control measures. Staphylococcus aureus and Enterococcus spp. are established pathogens in the hospital environment, and their frequent multidrug resistance complicates therapy. The archetypal hospital "superbug", methicillin-resistant S. aureus (MRSA), regularly attracts mass-media interest and, in many countries, there is political pressure to reduce MRSA infection rates, with some progress now being made in the United Kingdom and the United States. To compound these established problems, we have witnessed the emergence and spread of virulent clones of MRSA in the community, and of Clostridium difficile in hospitals. Multidrug-resistant Streptococcus pneumoniae clones are major community pathogens in many parts of the world, but are now being challenged by new conjugate vaccines. Using combinations of molecular epidemiological tools, which characterize the resistant isolates and their resistance determinants, scientists can track highly successful bacterial strains at local, national, and international levels. These methods have provided new insights into the evolution of key pathogens, and this information may aid the design of control strategies and vaccines. In addition, the development of new antimicrobials including oxazolidinones, lipopeptides, glycylcyclines, ketolides, and new generations of fluoroquinolones, antistaphylococcal b-lactams, and glycopeptides must remain a high priority for the continued effective treatment of infections caused by resistant strains. So far, resistance to these newer agents is identified rarely in surveillance programs, but occasional reports of resistance causing therapeutic failure (e.g., with linezolid, daptomycin, telithromycin, or newer fluoroquinolones) give cause for concern. The emergence of antibiotic resistance is inevitable, but we must seek to decrease its impact and prolong the effectiveness of the agents available to us.

Molecular epidemiology of isolates of the Cryptococcus neoformans species complex from Spain

To study genetic diversity of Cryptococcus neoformans species complex in Spain, 97 isolates of the yeast recovered from human, animal and environmental samples have been analysed using three molecular epidemiological techniques. One of these, URA5 gene fragment length polymorphism (RFLP) analysis, has been previously described as a molecular epidemiology tool. Thus, standard profiles and reference strains have been defined for it. In addition, 5S rDNA/IGS RFLP and [GACA] 4 microsatellite PCR fingerprinting were also used. Our results show five of the previously defined URA5 genotypes with a high frequency (33%) of the VNI type, which is in concordance with other studies. The high presence of VNIII pattern (28.9%) among our strains is remarkable and could be a specific feature of the isolates from our country. 5S rDNA/IGS RFLP showed a low intra-species discriminative power. Three different molecular profiles (S1-3), which showed a good correlation with the different species, varieties and genotypes, were obtained. [GACA] 4 microsatellite PCR-fingerprinting analysis showed a high variability of patterns among the studied strains. Molecular profiles represented in a dendrogram clustered strains in four main groups related with the source of the yeast and also in concordance with some of the described genotypes (VNI-IV and VGI).

Multiple-Locus Variable Number Tandem Repeat Analysis of Staphylococcus Aureus: Comparison with Pulsed-Field Gel Electrophoresis and spa-Typing

BackgroundMolecular typing of methicillin-resistant Staphylococcus aureus (MRSA) is required to study the routes and rates of transmission of this pathogen. Currently available typing techniques are either resource-intensive or have limited discriminatory ability. Multiple-locus variable number tandem repeat analysis (MLVA) may provide an alternative high throughput molecular typing tool with high epidemiological resolution.Methodology/Principal FindingsA new MLVA scheme for S. aureus was validated using 1681 S. aureus isolates collected from Dutch patients and 100 isolates from pigs. MLVA using 8 tandem repeat loci was performed in 2 multiplex PCRs and the fluorescently labeled PCR products were accurately sized on an automated DNA sequencer. The assessed number of repeats was used to create MLVA profiles consisting of strings of 8 integers that were used for categorical clustering. MLVA yielded 511 types that clustered into 11 distinct MLVA complexes which appeared to coincide with MLST clonal complexes. MLVA was at least as discriminatory as PFGE and twice as discriminatory as spa-sequence typing. There was considerable congruence between MLVA, spa-sequence typing and PFGE, at the MLVA complex level with group separation values of 95.1% and 89.2%. MLVA could not discriminate between pig-related MRSA strains isolated from humans and pigs, corroborating the high degree of relationship. MLVA was also superior in the grouping of MRSA isolates previously assigned to temporal-spatial clusters with indistinguishable SpaTypes, demonstrating its enhanced epidemiological usefulness.ConclusionsThe MLVA described in this study is a high throughput, relatively low cost genotyping method for S. aureus that yields discrete and unambiguous data that can be used to assign biological meaningful genotypes and complexes and can be used for interlaboratory comparisons in network accessible databases. Results suggest that MLVA offsets the disadvantages of other high discriminatory typing approaches and represents a promising tool for hospital, national and international molecular epidemiology.

Molecular characterization of Bovine herpesvirus type 1 Indonesian isolates

Different subtypes of bovine herpesvirus 1 (BHV-1) have been associated with different clinical conditions of cattle. For that reason subtypes differentiation has become an essential tool for understanding the pathogenesis and epidemiology of BHV infections. In search for a genomic region that would allow a clear distinction between BHV-1.1 and BHV-1.2 of glycoprotein D (gD) genes of 8 Indonesian isolates were amplified and sequenced. The amino acid sequence alignments revealed that the levels of genomic similarity ranging from 98.8 to 100% among BHV-1 Indonesian isolates and its results were also similar between BHV-1 Indonesia isolates and BHV-1.1 reference, and 98.4 to 98.8% between BHV-1 Indonesian isolates and BHV-1.2 reference. The isolates could be clearly separated into BHV-1.1 and BHV-1.2 after phylogenetic analysis. The results showed that the Indonesian isolates were characterized as BHV-1.1 as agent caused respiratory tract infections in cattle or infectious bovine rhinotracheitis (IBR) disease. The results suggest that the phylogenetic analysis performed here can be used as a potential molecular epidemiological tool for herpesviruses. Key Words : BHV-1.1, BHV-1.2, Glycoprotein D, Phylogenetic Analysis, IBR

Enhanced discrimination of African swine fever virus isolates through nucleotide sequencing of the p54, p72, and pB602L (CVR) genes

Complete sequencing of p54-gene from 67 European, American, and West and East African Swine Fever virus (ASFV) isolates revealed that West African and European ASFV isolates classified within the predominant Genotype I according to partial sequencing of p72 were discriminated into four major sub-types on the basis of their p54 sequences. This highlighted the value of p54 gene sequencing as an additional, intermediate-resolution, molecular epidemiological tool for typing of ASFV viruses. We further evaluated p54-based genotyping, in combination with partial sequences of two other genes, for determining the genetic relationships and origin of viruses responsible for disease outbreaks in Kenya. Animals from Western and central Kenya were confirmed as being infected with ASFV using a p72 gene-based PCR assay, following outbreaks of severe hemorrhagic disease in domestic pigs in 2006 and 2007. Eleven hemadsorbing viruses were isolated in macrophage culture and genotyped using a combination of full-length p54-gene sequencing, partial p72-gene sequencing, and analysis of tetrameric amino acid repeat regions within the variable region of the B602L gene (CVR). The data revealed that these isolates were identical in their p72 and p54 sequence to viruses responsible for ASF outbreaks in Uganda in 2003. There was a minor difference in the number of tetrameric repeats within the B602L sequence of the Kenyan isolates that caused the second Kenyan outbreak in 2007. A practical implication of the genetic similarity of the Kenyan and Ugandan viral isolates is that ASF control requires a regional approach.

Somatic mutation databases as tools for molecular epidemiology and molecular pathology of cancer: Proposed guidelines for improving data collection, distribution, and integration

There are currently less than 40 locus-specific databases (LSDBs) and one large general database that curate data on somatic mutations in human cancer genes. These databases have different scope and use different annotation standards and database systems, resulting in duplicated efforts in data curation, and making it difficult for users to find clear and consistent information. As data related to somatic mutations are generated at an increasing pace it is urgent to create a framework for improving the collecting of this information and making it more accessible to clinicians, scientists, and epidemiologists to facilitate research on biomarkers. Here we propose a data flow for improving the connectivity between existing databases and we provide practical guidelines for data reporting, database contents, and annotation standards. These proposals are based on common standards recommended by the Human Genome Variation Society (HGVS) with additions related to specific requirements of somatic mutations in cancer. Indeed, somatic mutations may be used in molecular pathology and clinical studies to characterize tumor types, help treatment choice, predict response to treatment and patient outcome, or in epidemiological studies as markers for tumor etiology or exposure assessment. Thus, specific annotations are required to cover these diverse research topics. This initiative is meant to promote collaboration and discussion on these issues and the development of adequate resources that would avoid the loss of extremely valuable information generated by years of basic and clinical research.

The CREST Biorepository: A Tool for Molecular Epidemiology and Translational Studies on Malignant Mesothelioma, Lung Cancer, and Other Respiratory Tract Diseases

The Cancer of RESpiratory Tract (CREST) biorepository was established to investigate biological mechanisms and to develop tools and strategies for primary and secondary prevention of respiratory tract cancer. The CREST biorepository is focused on pleural malignant mesothelioma, a rare and severe cancer linked to asbestos exposure whose incidence is particularly high in the Ligurian region. The CREST biorepository includes biological specimens from (a) patients with pleural malignant mesothelioma and lung cancer, (b) patients with nonneoplastic respiratory conditions, and (c) control subjects. Whole blood, plasma, serum, lymphocytes, pleural fluid, saliva, and biopsies are collected, and a questionnaire is administered. Collection, transportation, and storage are done according to international standards. As of January 31, 2008, the overall number of subjects recruited was 1,590 (446 lung cancer, 209 pleural malignant mesothelioma, and 935 controls). The biorepository includes a total of 10,055 aliquots (4,741 serum; 3,082 plasma; 1,599 whole blood; 633 pleural fluid; and 561 lymphocytes) and 107 biopsies. Demographic, clinical, and epidemiologic information is collected for each subject and processed in a dedicated database. The CREST biorepository is a valuable tool for molecular epidemiology and translational studies. This structure relies on a network of contacts with local health districts that allows for an active search for patients. This is a particularly efficient approach, especially when the object of the study is a rare cancer type. The CREST experience suggests that the presence of limited resources can be overcome by the biorepository specialization, the high quality of the epidemiologic information, and the variety of samples.

Intragenomic Variation in the Internal Transcribed Spacer 1 Region of Dientamoeba fragilis as a Molecular Epidemiological Marker

Dientamoeba fragilis is a parasite that has been recognized to be a causative agent of gastrointestinal symptoms. Because in most studies only some infected persons experience symptoms, it is possible that D. fragilis is a heterogeneous species with variants that display similar morphologies but different pathogenicities. The search for genetic variation in D. fragilis was based on the small-subunit rRNA gene, which was not found to be useful for molecular epidemiology. In this report, we describe the isolation and characterization of additional rRNA gene cluster sequences, the internal transcribed spacer 1 (ITS-1)-5.8S rRNA gene-ITS-2 region. For comparative purposes, we also isolated the ITS-1-5.8S rRNA gene-ITS-2 region of Histomonas meleagridis, a protozoan parasite of birds and a close relative of D. fragilis. This region was found to be highly variable, and 11 different alleles of the ITS-1 sequence could be identified. Variation in the ITS-1 region was found to be intragenomic, with up to four different alleles in a single isolate. So-called C profiles were produced from the ITS-1 repertoire of single isolates. Analysis of the C profiles of isolates from nonrelated patients identified several clearly distinguishable strains of D. fragilis. Within families, it was shown that members can be infected with the same or different strains of D. fragilis. In conclusion, the ITS-1 region can serve as a molecular epidemiological tool for the subtyping of D. fragilis directly from feces. This may serve as a means of studying the transmission, geographical distribution, and relationships between strains and the pathogenicity of this parasite.

A European laboratory network for sequence-based typing of methicillin-resistant Staphylococcus aureus (MRSA) as a communication platform between human and veterinary medicine – an update on SeqNet.org

Binary file ES_Abstracts_Final_ECDC.txt matches

Zoonotic cryptosporidiosis

The widespread usages of molecular epidemiological tools have improved the understanding of cryptosporidiosis transmission. Much attention on zoonotic cryptosporidiosis is centered on Cryptosporidium parvum. Results of genotype surveys indicate that calves are the only major reservoir for C. parvum infections in humans. The widespread presence of human-adapted C. parvum, especially in developing countries, is revealed by recent subtyping and multilocus typing studies, which have also demonstrated the anthroponotic transmission of C. parvum subtypes shared by humans and cattle. Developing and industrialized countries differ significantly in disease burdens caused by zoonotic species and in the source of these parasites, with the former having far fewer human infections caused by C. parvum and little zoonotic transmission of this species. Exclusive anthroponotic transmission of seemingly zoonotic C. parvum subtypes was seen in Mid-Eastern countries. Other zoonotic Cryptosporidium spp. are also responsible for substantial numbers of human infections in developing countries, many of which are probably transmitted by anthroponotic pathways. The lower pathogenicity of some zoonotic species in some populations supports the occurrence of different clinical spectra of Cryptosporidium spp. in humans. The use of a new generation of molecular diagnostic tools is likely to produce a more complete picture of zoonotic cryptosporidiosis.