Human-induced pluripotent stem cell-derived ovarian support cell co-culture improves oocyte maturation in vitro after abbreviated gonadotropin stimulation.

STUDY QUESTION: Can in vitro maturation (IVM) and developmental competence of human oocytes be improved by co-culture with ovarian support cells (OSCs) derived from human-induced pluripotent stem cells (hiPSCs)? SUMMARY ANSWER: OSC-IVM significantly improves the rates of metaphase II (MII) formation and euploid Day 5 or 6 blastocyst formation, when compared to a commercially available IVM system. WHAT IS KNOWN ALREADY: IVM has historically shown highly variable performance in maturing oocytes and generating oocytes with strong developmental capacity, while limited studies have shown a positive benefit of primary granulosa cell co-culture for IVM. We recently reported the development of OSCs generated from hiPSCs that recapitulate dynamic ovarian function in vitro. STUDY DESIGN, SIZE, DURATION: The study was designed as a basic science study, using randomized sibling oocyte specimen allocation. Using pilot study data, a prospective sample size of 20 donors or at least 65 oocytes per condition were used for subsequent experiments. A total of 67 oocyte donors were recruited to undergo abbreviated gonadotropin stimulation with or without hCG triggers and retrieved cumulus-oocyte complexes (COCs) were allocated between the OSC-IVM or control conditions (fetal-like OSC (FOSC)-IVM or media-only IVM) in three independent experimental design formats. The total study duration was 1 April 2022 to 1 July 2023. PARTICIPANTS/MATERIALS, SETTING, METHODS: Oocyte donors between the ages of 19 and 37 years were recruited for retrieval after informed consent, with assessment of anti-Mullerian hormone, antral follicle count, age, BMI and ovarian pathology used for inclusion and exclusion criteria. In experiment 1, 27 oocyte donors were recruited, in experiment 2, 23 oocyte donors were recruited, and in experiment 3, 17 oocyte donors and 3 sperm donors were recruited. The OSC-IVM culture condition was composed of 100 000 OSCs in suspension culture with hCG, recombinant FSH, androstenedione, and doxycycline supplementation. IVM controls lacked OSCs and contained either the same supplementation, FSH and hCG only (a commercial IVM control), or FOSCs with the same supplementation (Media control). Experiment 1 compared OSC-IVM, FOSC-IVM, and a Media control, while experiments 2 and 3 compared OSC-IVM and a commercial IVM control. Primary endpoints in the first two experiments were the MII formation (i.e. maturation) rate and morphological quality assessment. In the third experiment, the fertilization and embryo formation rates were assessed with genetic testing for aneuploidy and epigenetic quality in blastocysts. MAIN RESULTS AND THE ROLE OF CHANCE: We observed a statistically significant improvement (∼1.5×) in maturation outcomes for oocytes that underwent IVM with OSCs compared to control Media-IVM and FOSC-IVM in experiment 1. More specifically, the OSC-IVM group yielded a MII formation rate of 68% ± 6.83% SEM versus 46% ± 8.51% SEM in the Media control (P = 0.02592, unpaired t-test). FOSC-IVM yielded a 51% ± 9.23% SEM MII formation rate which did not significantly differ from the media control (P = 0.77 unpaired t-test). Additionally, OSC-IVM yielded a statistically significant ∼1.6× higher average MII formation rate at 68% ± 6.74% when compared to 43% ± 7.90% in the commercially available IVM control condition (P = 0.0349, paired t-test) in experiment 2. Oocyte morphological quality between OSC-IVM and the controls did not significantly differ. In experiment 3, OSC-IVM oocytes demonstrated a statistically significant improvement in Day 5 or 6 euploid blastocyst formation per COC compared to the commercial IVM control (25% ± 7.47% vs 11% ± 3.82%, P = 0.0349 logistic regression). Also in experiment 3, the OSC-treated oocytes generated blastocysts with similar global and germline differentially methylated region epigenetic profiles compared commercial IVM controls or blastocysts after either conventional ovarian stimulation. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: While the findings of this study are compelling, the cohort size remains limited and was powered on preliminary pilot studies, and the basic research nature of the study limits generalizability compared to randomized control trials. Additionally, use of hCG-triggered cycles results in a heterogenous oocyte cohort, and potential differences in the underlying maturation state of oocytes pre-IVM may limit or bias findings. Further research is needed to clarify and characterize the precise mechanism of action of the OSC-IVM system. Further research is also needed to establish whether these embryos are capable of implantation and further development, a key indication of their clinical utility. WIDER IMPLICATIONS OF THE FINDINGS: Together, these findings demonstrate a novel approach to IVM with broad applicability to modern ART practice. The controls used in this study are in line with and have produced similar to findings to those in the literature, and the outcome of this study supports findings from previous co-culture studies that found benefits of primary granulosa cells on IVM outcomes. The OSC-IVM system shows promise as a highly flexible IVM approach that can complement a broad range of stimulation styles and patient populations. Particularly for patients who cannot or prefer not to undergo conventional gonadotropin stimulation, OSC-IVM may present a viable path for obtaining developmentally competent, mature oocytes. STUDY FUNDING/COMPETING INTEREST(S): A.D.N., A.B.F., A.G., B.P., C.A., C.C.K., F.B., G.R., K.S.P., K.W., M.M., P.C., S.P., and M.-J.F.-G. are shareholders in the for-profit biotechnology company Gameto Inc. P.R.J.F. declares paid consultancy for Gameto Inc. P.C. also declares paid consultancy for the Scientific Advisory Board for Gameto Inc. D.H.M. has received consulting services from Granata Bio, Sanford Fertility and Reproductive Medicine, Gameto, and Buffalo IVF, and travel support from the Upper Egypt Assisted Reproduction Society. C.C.K., S.P., M.M., A.G., B.P., K.S.P., G.R., and A.D.N. are listed on a patent covering the use of OSCs for IVM: U.S. Provisional Patent Application No. 63/492,210. Additionally, C.C.K. and K.W. are listed on three patents covering the use of OSCs for IVM: U.S. Patent Application No. 17/846,725, U.S Patent Application No. 17/846,845, and International Patent Application No.: PCT/US2023/026012. C.C.K., M.P.S., and P.C. additionally are listed on three patents for the transcription factor-directed production of granulosa-like cells from stem cells: International Patent Application No.: PCT/US2023/065140, U.S. Provisional Application No. 63/326,640, and U.S. Provisional Application No. 63/444,108. The remaining authors have no conflicts of interest to declare.

"Pause" for Resident Education in the Operating Room.

Objective: To determine if asking residents to discuss their specific learning objectives with the attending physician prior to beginning a surgical case would improve the educational experience in the operating room. Study Design: This was a prospective nonrandomized cohort study utilizing a self-administered questionnaire. Prior to the intervention, residents and attendings were asked to fill out surveys evaluating the educational experience in the operating room. Subsequently, attending physicians were instructed to ask residents at the beginning of the surgery, "What are your goals for this surgical case?" During this intervention period, the same anonymous survey was filled out. Preintervention and postintervention answers were compared by t test and Fisher's exact test. Results: A total of 49 preintervention and 47 postintervention resident-attending survey pairs were collected. After implementation of the intervention, 100% of residents reported having surgical goals for the procedure as compared to 45% prior to the intervention (p<0.0001). Additionally, during the intervention residents reported they were better able to maximize learning opportunities and were more satisfied with their participation in the case. Attending physicians were more likely to be aware of resident learning objectives after the intervention. Conclusion: We propose the routine addition of an educational pause to the surgical time out.

Characterization of human spermatogonial stem cell markers in fetal, pediatric, and adult testicular tissues.

Autologous spermatogonial stem cell (SSC) transplantation is a potential therapeutic modality for patients with azoospermia following cancer treatment. For this promise to be realized, definitive membrane markers of prepubertal and adult human SSCs must be characterized in order to permit SSC isolation and subsequent expansion. This study further characterizes the markers of male gonocytes, prespermatogonia, and SSCs in humans. Human fetal, prepubertal, and adult testicular tissues were analyzed by confocal microscopy, fluorescence-activated cell sorting, and qRT-PCR for the expression of unique germ cell membrane markers. During male fetal development, THY1 and KIT (C-Kit) are transient markers of gonocytes but not in prespermatogonia and post-natal SSCs. Although KIT expression is detected in gonocytes, THY1 expression is also detected in the somatic component of the fetal testes in addition to gonocytes. In the third trimester of gestation, THY1 expression shifts exclusively to the somatic cells of the testes where it continues to be detected only in the somatic cells postnatally. In contrast, SSEA4 expression was only detected in the gonocytes, prespermatogonia, SSCs, and Sertoli cells of the fetal and prepubertal testes. After puberty, SSEA4 expression can only be detected in primitive spermatogonia. Thus, although THY1 and KIT are transient markers of gonocytes, SSEA4 is the only common membrane marker of gonocytes, prespermatogonia, and SSCs from fetal through adult human development. This finding is essential for the isolation of prepubertal and adult SSCs, which may someday permit fertility preservation and reversal of azoospermia following cancer treatment.

Donor side effects experienced under minimal controlled ovarian stimulation with in vitro maturation vs. conventional controlled ovarian stimulation for in vitro fertilization treatment.

OBJECTIVE: To evaluate oocyte retrieval experiences and side effects under minimally controlled ovarian stimulation (COS) treatment for in vitro maturation (IVM) of oocytes compared with conventional COS treatment. DESIGN: A retrospective survey study. SETTING: Clinical in vitro fertilization treatment center. PATIENT(S): Data were collected from subjects undergoing minimal COS treatment (n = 110; 600-800 IU follicle-stimulating hormone) for IVM of oocytes and conventional COS treatment for egg donation (n = 48; 1,800-2,600 IU follicle-stimulating hormone) from April 2022 to November 2023. INTERVENTION(S): Minimal and conventional COS treatments. MAIN OUTCOME MEASURE(S): The most common side effects experienced during ovarian stimulation and after oocyte pick-up, satisfaction level, and the likelihood of recommending or repeating minimal or conventional COS. Statistical analysis included Mann-Whitney U test and χ2 tests, with a significance level. RESULT(S): During minimal COS treatment, most subjects did not experience breast swelling (86%), pelvic or abdominal pain (76%), nausea or vomiting (96%), and bleeding (96%). After oocyte pick-up, the majority (75%) reported no pelvic or abdominal pain. The most common side effect was abdominal swelling (52%). Compared with conventional COS cycles, minimal COS subjects reported significantly less postretrieval pain, with 33% experiencing no pain (vs. 6%) and with a reduced severe level of pain (5% vs. 19%), leading to fewer subjects requiring pain medication (25% vs. 54%). Additionally, 85% of women were very satisfied with minimal stimulation treatment and would recommend or repeat the treatment. CONCLUSION(S): Reducing the hormonal dose for ovarian stimulation has a beneficial effect on subjects, suggesting the combination of minimal COS treatment with IVM techniques is a well-tolerated alternative for women who cannot or do not wish to undergo conventionally controlled ovarian hyperstimulation treatment.

The transcriptome of a human polar body accurately reflects its sibling oocyte.

Improved methods are needed to reliably and accurately evaluate oocyte quality prior to fertilization and transfer into the woman of human embryos created through in vitro fertilization (IVF). All oocytes that are retrieved and matured in culture are exposed to sperm with little in the way of evaluating the oocyte quality. Furthermore, embryos created through IVF are currently evaluated for developmental potential by morphology, a criterion lacking in quantitation and accuracy. With the recent successes in oocyte vitrification and storage, clear metrics are needed to determine oocyte quality prior to fertilizing. The first polar body (PB) is extruded from the oocyte before fertilization and can be biopsied without damaging the oocyte. Here, we tested the hypothesis that the PB transcriptome is representative of that of the oocyte. Polar body biopsy was performed on metaphase II (MII) oocytes followed by single-cell transcriptome analysis of the oocyte and its sibling PB. Over 12,700 unique mRNAs and miRNAs from the oocyte samples were compared with the 5,431 mRNAs recovered from the sibling PBs (5,256 shared mRNAs or 97%, including miRNAs). The results show that human PBs reflect the oocyte transcript profile and suggests that mRNA detection and quantification through high-throughput quantitative PCR could result in the first molecular diagnostic for gene expression in MII oocytes. This could allow for both oocyte ranking and embryo preferences in IVF applications.

Whole-genome risk prediction of common diseases in human preimplantation embryos.

Preimplantation genetic testing (PGT) of in-vitro-fertilized embryos has been proposed as a method to reduce transmission of common disease; however, more comprehensive embryo genetic assessment, combining the effects of common variants and rare variants, remains unavailable. Here, we used a combination of molecular and statistical techniques to reliably infer inherited genome sequence in 110 embryos and model susceptibility across 12 common conditions. We observed a genotype accuracy of 99.0-99.4% at sites relevant to polygenic risk scoring in cases from day-5 embryo biopsies and 97.2-99.1% in cases from day-3 embryo biopsies. Combining rare variants with polygenic risk score (PRS) magnifies predicted differences across sibling embryos. For example, in a couple with a pathogenic BRCA1 variant, we predicted a 15-fold difference in odds ratio (OR) across siblings when combining versus a 4.5-fold or 3-fold difference with BRCA1 or PRS alone. Our findings may inform the discussion of utility and implementation of genome-based PGT in clinical practice.

Detection and quantification of mRNA in single human polar bodies: a minimally invasive test of gene expression during oogenesis.

Proteins and mRNA produced in oogenesis support embryonic development until the zygotic transition, 3 days after fertilization. Since polar bodies can be biopsied with little if any harm to the oocyte, we tested the hypothesis that mRNA originating from expression in the meiotic oocyte is present and detectable in a single polar body prior to insemination. Human oocytes were obtained from patients undergoing controlled ovarian hyperstimulation and intracytoplasmic sperm injection. Immature oocytes were cultured overnight and inspected the following day for maturation. Metaphase II oocytes underwent polar body biopsy followed by reverse transcription without RNA isolation. Sibling oocytes were similarly prepared. Complementary DNA from all samples were pre-amplified over 15 cycles for candidate genes using selective primers. Real-time PCR was performed to detect and quantify relative single-cell gene expression. Polar body mRNA was detected in 11 of 12 candidate genes. Transcripts that were present in greater abundance in the oocyte were more likely to be detected in qPCR replicates from single polar bodies. Pre-amplification of cDNA synthesized without RNA isolation can facilitate the quantitative detection of mRNA in single human polar bodies.

Fibroids and reproductive outcomes: a systematic literature review from conception to delivery.

We examined the published relationship between uterine fibroids and reproductive outcomes. Submucosal fibroids had the strongest association with lower ongoing pregnancy rates, odds ratio, 0.5; 95% confidence interval, 0.3-0.8, primarily through decreased implantation. Cumulative pregnancy rates appeared slightly lower in patients with intramural fibroids 36.9% vs 41.1%, which may reflect biases in the literature; however, patients with intramural fibroids also experienced more miscarriages, 20.4% vs 12.9%. Adverse obstetric outcomes are rare and may reflect age or other differences in fibroid populations. Increased risk of malpresentation (odds ratio, 2.9; 2.6-3.2), cesarean (odds ratio, 3.7; 3.5-3.9), and preterm delivery (odds ratio, 1.5; 1.3-1.7) are reported; however, the incidence of labor dystocia was low (7.5%). There was no conclusive evidence that intramural or subserosal fibroids adversely affect fecundity. More prospective, controlled trials are needed to assess the effects of myomectomy. Good maternal and neonatal outcomes are expected in pregnancies with uterine fibroids.

Abruptio placentae in the setting of an atypical presentation of acute appendicitis: a case report.

BACKGROUND: Causes of placental abruption include traumatic events, cocaine use, hypertension, cigarette smoking and advanced maternal age. Recent studies also implicate inflammatory precursors, such as preterm premature rupture of membranes and chorioamnionitis. Clear precipitating events are often not identified, and precise etiologic determinants are still being determined. CASE: A 25-year-old woman, grayida 4, para 2012, presented with acute onset of severe abdominal pain; frequent, low-amplitude contractions; and a nonreassuring fetal heart tracing. While performing an urgent cesarean section for acute placental abruption, a ruptured appendicitis was identified. CONCLUSION: This case suggests that appendicitis in the third trimester may be a risk factor for placental abruption.

Access to infertility care in the developing world: the family promotion gap.

Infertility in resource-poor settings is an overlooked global health problem. Although scarce health care resources must be deployed thoughtfully, prioritization of resources may be different for recipient and donor countries, the latter of whom focus on maternal health care, prevention, and family planning. For women and couples with involuntary childlessness, the negative psychosocial, sociocultural, and economic consequences in low-income countries are severe, possibly more so than in most Western societies. Despite the local importance of infertility, few resources are committed to help advance infertility care in regions like sub-Saharan Africa. The worldwide prevalence of infertility is remarkably similar across low-, middle-, and high-income countries. The World Health Organization (WHO) recognizes infertility as a global health problem and established universal access to reproductive health care as one of the United Nation's Millennium Developmental Goals for 2015. Currently, access to infertility care is varied and is usually only attainable by the very wealthy in low-income countries. We provide an overview on the current state of access to infertility care in low-income countries such as in sub-Saharan Africa and a rationale for providing comprehensive reproductive care and possible solutions for providing cost-effective infertility services in these settings.

Optimizing cryopreservation of human spermatogonial stem cells: comparing the effectiveness of testicular tissue and single cell suspension cryopreservation.

OBJECTIVE: To determine whether optimal human spermatogonial stem cell (SSC) cryopreservation is best achieved with testicular tissue or single cell suspension cryopreservation. This study compares the effectiveness between these two approaches by using testicular SSEA-4+ cells, a known population containing SSCs. DESIGN: In vitro human testicular tissues. SETTING: Academic research unit. PATIENT(S): Adult testicular tissues (n=4) collected from subjects with normal spermatogenesis and normal fetal testicular tissues (n=3). INTERVENTION(S): Testicular tissue versus single cell suspension cryopreservation. MAIN OUTCOME MEASURE(S): Cell viability, total cell recovery per milligram of tissue, as well as viable and SSEA-4+ cell recovery. RESULT(S): Single cell suspension cryopreservation yielded higher recovery of SSEA-4+ cells enriched in adult SSCs, whereas fetal SSEA-4+ cell recovery was similar between testicular tissue and single cell suspension cryopreservation. CONCLUSION(S): Adult and fetal human SSEA-4+ populations exhibited differential sensitivity to cryopreservation based on whether they were cryopreserved in situ as testicular tissues or as single cells. Thus, optimal preservation of human SSCs depends on the patient's age, type of samples cryopreserved, and end points of therapeutic applications.

Testicular niche required for human spermatogonial stem cell expansion.

Prepubertal boys treated with high-dose chemotherapy do not have an established means of fertility preservation because no established in vitro technique exists to expand and mature purified spermatogonial stem cells (SSCs) to functional sperm in humans. In this study, we define and characterize the unique testicular cellular niche required for SSC expansion using testicular tissues from men with normal spermatogenesis. Highly purified SSCs and testicular somatic cells were isolated by fluorescence-activated cell sorting using SSEA-4 and THY1 as markers of SSCs and somatic cells. Cells were cultured on various established niches to assess their role in SSC expansion in a defined somatic cellular niche. Of all the niches examined, cells in the SSEA-4 population exclusively bound to adult testicular stromal cells, established colonies, and expanded. Further characterization of these testicular stromal cells revealed distinct mesenchymal markers and the ability to undergo differentiation along the mesenchymal lineage, supporting a testicular multipotent stromal cell origin. In vitro human SSC expansion requires a unique niche provided exclusively by testicular multipotent stromal cells with mesenchymal properties. These findings provide an important foundation for developing methods of inducing SSC growth and maturation in prepubertal testicular tissue, essential to enabling fertility preservation for these boys.

Management of the first in vitro fertilization cycle for unexplained infertility: a cost-effectiveness analysis of split in vitro fertilization-intracytoplasmic sperm injection.

OBJECTIVE: To determine the cost-effectiveness of split IVF-intracytoplasmic sperm injection (ICSI) for the treatment of couples with unexplained infertility. DESIGN: Adaptive decision model. SETTING: Academic infertility clinic. PATIENT(S): A total of 154 couples undergoing a split IVF-ICSI cycle and a computer-simulated cohort of women <35 years old with unexplained infertility undergoing IVF. INTERVENTION(S): Modeling insemination method in the first IVF cycle as all IVF, split IVF-ICSI, or all ICSI, and adapting treatment based on fertilization outcomes. MAIN OUTCOME MEASURE(S): Live birth rate, incremental cost-effectiveness ratio (ICER). RESULT(S): In a single cycle, all IVF is preferred as the ICER of split IVF-ICSI or all ICSI ($58,766) does not justify the increased live birth rate (3%). If two cycles are needed, split IVF/ICSI is preferred as the increased cumulative live birth rate (3.3%) is gained at an ICER of $29,666. CONCLUSION(S): In a single cycle, all IVF was preferred as the increased live birth rate with split IVF-ICSI and all ICSI was not justified by the increased cost per live birth. If two IVF cycles are needed, however, split IVF/ICSI becomes the preferred approach, as a result of the higher cumulative live birth rate compared with all IVF and the lesser cost per live birth compared with all ICSI.

Use of sea stars to study basic reproductive processes.

Echinoderms are closely related to chordates and comprise a major group of invertebrate deuterostomes. They are broadcast spawners and as such, each female accumulates millions of eggs and oocytes. These cells are readily isolated, and are often large, clear, and surrounded by accessory cells and extracellular coverings that do not prevent access to the oocyte. Sea star oocytes are stored in prophase of meiosis, and since the natural meiotic stimulus has been identified as 1-methyladenine, these cells can be induced to complete meiotic maturation as individuals, or synchronously en masse. Microinjection and culture of these cells is feasible using quantitative or repetitive methods so that hundreds of oocytes and eggs can be modified each hour. Experimentation on this organism is extensive over a rich history of reproductive and developmental biology so that new investigators can easily incorporate this organism into their repertoire of research. This review will highlight the fundamental protocols to enable a new investigator to perform an array of approaches on this organism, including oocyte isolation, microinjection, and even single cell quantitative PCR.

The role of embryonic origin in preeclampsia: a comparison of autologous in vitro fertilization and ovum donor pregnancies.

OBJECTIVE: To compare the risk of gestational hypertension and preeclampsia in pregnancies conceived through standard in vitro fertilization (IVF) using autologous oocytes with pregnancies conceived using donated oocytes. METHODS: We conducted a retrospective, matched cohort study of women undergoing IVF using autologous compared with donor oocytes between 1998 and 2005. Women with live births resulting from oocyte donor pregnancies were matched for age and plurality (singleton or twin) with women undergoing autologous IVF. Primary outcomes were the incidence of preeclampsia or gestational hypertension (with and without proteinuria) in the third trimester. Data on preterm delivery, low birth weight, and embryo cryopreservation were also recorded. RESULTS: Outcome data were available for 158 pregnancies, including 77 ovum-donor recipient pregnancies and 81 pregnancies using autologous oocytes. There were no differences in age, parity, and gestational type between the two cohorts. The incidence of gestational hypertension and preeclampsia was significantly higher in ovum-donor recipients compared with women undergoing autologous IVF (24.7% compared with 7.4%, P<.01, and 16.9% compared with 4.9%, P=.02, respectively). Ovum-donor recipients were more likely than women undergoing autologous IVF to deliver prematurely (34% compared with 19%). This association remained after controlling for multiple gestation (odds ratio 2.6, 95% confidence interval 1.04-6.3). Sixteen pregnancies from cryopreserved embryos were more likely to have hypertensive disorders of pregnancy (odds ratio 5.0, 95% confidence interval 1.2-20.5). CONCLUSION: Pregnancies derived from donor oocytes and cryopreserved-thawed embryos may be at a higher risk for hypertensive disorders of pregnancy. These findings inform future research and help counsel women using assisted reproductive technology.

A pregnancy complicated by endometrial scarring.

A 39-year-old woman with a thick uterine synechia became pregnant with placental tissue implanted on both sides. She underwent serial ultrasounds during her pregnancy, experienced some mild second trimester bleeding, but delivered successfully at term.

Epidemiologic response to anthrax outbreaks: field investigations, 1950-2001.

We used unpublished reports, published manuscripts, and communication with investigators to identify and summarize 49 anthrax-related epidemiologic field investigations conducted by the Centers for Disease Control and Prevention from 1950 to August 2001. Of 41 investigations in which Bacillus anthracis caused human or animal disease, 24 were in agricultural settings, 11 in textile mills, and 6 in other settings. Among the other investigations, two focused on building decontamination, one was a response to bioterrorism threats, and five involved other causes. Knowledge gained in these investigations helped guide the public health response to the October 2001 intentional release of B. anthracis, especially by addressing the management of anthrax threats, prevention of occupational anthrax, use of antibiotic prophylaxis in exposed persons, use of vaccination, spread of B. anthracis spores in aerosols, clinical diagnostic and laboratory confirmation methods, techniques for environmental sampling of exposed surfaces, and methods for decontaminating buildings.

Environmental exposure and leptospirosis, Peru.

Human infection by leptospires has highly variable clinical manifestations, which range from subclinical infection to fulminant disease. We conducted a population-based, cross-sectional seroepidemiologic study in Peru to determine potential relationships of environmental context to human exposure to Leptospira and disease associated with seroconversion. Three areas were studied: a flooded, urban slum in the Peruvian Amazon city of Iquitos; rural, peri-Iquitos villages; and a desert shantytown near Lima. Seroprevalence in Belen was 28% (182/650); in rural areas, 17% (52/316); and in a desert shantytown, 0.7% (1/150). Leptospira-infected peridomestic rats were found in all locales. In Belen, 20 (12.4%) of 161 patients seroconverted between dry and wet seasons (an incidence rate of 288/1,000). Seroconversion was associated with history of febrile illness; severe leptospirosis was not seen. Human exposure to Leptospira in the Iquitos region is high, likely related both to the ubiquity of leptospires in the environment and human behavior conducive to transmission from infected zoonotic sources.