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Background: The emergence of pfhrp2/3 -deleted parasites threatens histidine-rich protein 2 (HRP2)-based malaria rapid diagnostic test (RDT) performance. RDTs targeting Plasmodium falciparum ( Pf ) lactate dehydrogenase (LDH) may address current product limitations and improve case management., Objectives: To evaluate the performance and usability of three LDH-based RDTs in febrile patients., Methods: A cross-sectional diagnostic accuracy study was conducted in Kédougou, Senegal. Capillary blood was tested using the SD Bioline Ag Pf (#05FK50) and three LDH-based RDTs: BIOCREDIT Malaria Ag Pf (pLDH), BIOCREDIT Pf (pLDH/HRPII), and BIOCREDIT Pf/Pv (pLDH/pLDH) (Rapigen Inc., Republic of Korea). Venous blood was collected to repeat the BIOCREDIT RDTs and conduct microscopy. Frozen venous specimens were tested using a reference PCR assay. A quantitative multiplex malaria antigen assay measured antigen concentration. RDT performance was determined and analyzed as a function of antigen concentration distribution. Usability of the Pf -only BIOCREDIT tests was evaluated using a questionnaire., Results: 154/220 participants (70%) were Pf -positive by PCR. The Pf (pLDH/HRPII) test demonstrated the highest sensitivity at 78% (70.9%-84.5%); specificity was 89% (79.4%-95.6%). All RDTs performed better than microscopy (53% sensitivity). RDTs performed better when compared to antigen concentration over PCR results. Improved sensitivity of the Pf (pLDH/HRPII) test was driven by the HRP2 line. Line intensity correlated with antigen concentration. Predicted sensitivity using the analytical limit of detection (LOD) was comparable to observed sensitivity. RDTs demonstrated acceptable usability., Conclusions: Both HRP2 and LDH contributed to the sensitivity of the best-performing Pf -RDT. RDT analytical LODs can be used to predict performance in populations with known antigen concentrations., Competing Interests: Conflict of interest statement The authors have no competing interests to declare.

In malaria endemic countries, non-falciparum species are often mixed with Plasmodium falciparum in patients with uncomplicated malaria, and their contribution to malaria severity and death is poorly studied. This study assesses the contribution of non-falciparum species to malaria severity in three regions of Senegal with the highest malaria incidence.We analysed 617 blood samples obtained between 2015 and 2021 from confirmed malaria patients at health facilities in Kedougou, Kolda and Tambacounda in Senegal. Plasmodium species composition was determined by PCR and their distribution were analysed according to age and disease severity, and the relative risk of developing severe malaria.Overall, 94.8% of samples contained P. falciparum either as single or mixed with other species. Non-falciparum P. ovale, P. vivax and P. malariae species were detected in 60.12, 13.61 and 1.62% of samples, respectively. Severe malaria was primarily due to P. falciparum, but co-infection with P. vivax led to a 1.63-fold significant (p = 0.05) increased risk of developing severe malaria, contrasting with the non-significant reduced risk (OR = 0.78; CI 95: 0.55-1.11; p = 0.16) associated with P. ovale infections. Children aged < 15 years old significantly suffered of SM than adults patients, whereas no significant association was found in relation to patient' sex.This study reports the first association of non-falciparum species infections with clinical malaria phenotypes in patients from the three most malaria-affected regions in Senegal. Non-falciparum P. ovale and P. vivax species in combination with P. falciparum had a protective and worsening effect, respectively. The findings suggest that interventions targeting only P. falciparum might not be sufficient to eliminate the overall malaria burden, and should take into account the neglected non-falciparum species., Competing Interests: Declarations. Ethics approval and consent to participate: The study objectives, benefits and risks were explained in French language or local dialects to all participants before inclusion. Written informed consent was obtained from all adult participants and from the parents, or legal guardians of children. The study was examined and approved by the Senegalese National Health Research Committee under the references 0081MSP/DS/CNRS and 00185 MSAS/CNERS/SP. Competing interests: The authors declare that they have no competing interests., (© 2024. The Author(s).)

The discovery of novel quaternary intermetallic compounds R 2 MoSi 2 C (R = Y, Gd) in the R-Mo-Si-C system is reported. Their crystal structure was investigated using single-crystal X-ray diffraction. It is shown that the Y 2 MoSi 2 C and Gd 2 MoSi 2 C compounds crystallize in the tetragonal space group P4/mbm (Pearson symbol tP12) with unit-cell parameters a = 6.9525 (18) Å, c = 4.1962 (16) Å, and a = 6.9945 (16) Å, c = 4.2020 (14) Å, respectively.

Objectives: In low malaria transmission areas, the elimination of the disease has been hampered partly by the existence of a reservoir of subpatent Plasmodium falciparum infections within communities. This reservoir, often undetected, serves as a source of parasites and contributes to ongoing transmission and clinical malaria cases., Methods: This study, spanning a period of 9 years from June 2014 to December 2022, examined individual variations and long-term subpatent P. falciparum carriage in two matched cohorts of 44 individuals each living in Dielmo village in the Sudanian area of Senegal. Biannual blood samples, collected in June/July and December of each year, underwent P. falciparum diagnosis by quantitative polymerase chain reaction. QGIS and R analytical tools were used to map infections, assess the occurrence and clustering of subpatent and clinical P. falciparum infections, and determine the risk of infection in the vicinity of asymptomatic P. falciparum carriers., Results: The point frequency and long-term P. falciparum carriage were significantly higher among the quantitative polymerase chain reaction (qPCR) positive cohort compared to the negative cohort across the 16 cross-sectional surveys analyzed in this study (19.76% vs 10.99%, P-value <0.001). Asymptomatic carriage events in qPCR-positive group were 18.86 ± 1.72% and significantly greater (P-value = 0.001) than in the qPCR-negative group (11.32 ± 1.32%). The relative risk of P. falciparum infection or clinical malaria calculated with a 95% confidence interval significantly increased in the vicinity of infected individuals and was 1.44 (P-value = 0.53) and 2.64 (P-value = 0.04) when at least one individual in the direct (household) or indirect (block of households) vicinity is infected, respectively. The risk increased to 3.64 (P-value <0.001) if at least 1/5 of individuals in the indirect vicinity were P. falciparum-infected., Conclusions: The study provides a detailed qualitative and quantitative analysis of the asymptomatic P. falciparum reservoir and its temporal and spatial dynamics within two subgroups of P. falciparum-infected and non-infected individuals in Dielmo village. It identified high-risk populations known as "hotpops" and hotspots that could be targeted by innovative interventions to accelerate the elimination of malaria in Dielmo village., Competing Interests: Declarations of competing interest The authors have declared that no competing interests exist., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: The first discovery of Plasmodium vivax infections in Senegal used archived patients' sera in place of blood pellet, the preferred specimen for the molecular diagnosis of Plasmodium species. The present study assessed the reliability of detecting P. vivax DNA in plasma in comparison to blood pellet from the same patient's samples., Methods: A total of 616 blood samples obtained from febrile patients living in Kolda (2015 and 2020), Tambacounda (2017 and 2020), and Kedougou (2020) regions in Senegal, were first screened for Plasmodium species composition by 18S ssrRNA-based nested PCR. Paired blood pellets and plasma samples were selected from a subset of 50 P. vivax -positive patients matched by age and sex with 50 P. vivax -negative patients, and subjected to a cytochrome b-based qPCR to compare the detection and quantification of P. vivax genomic DNA between the two specimen types., Results and Discussion: The study reports 1.8% and 14.77% of single and mixed P. vivax infections in the study population, and a high concordance (84%) between the qPCR detection of P. vivax genomic DNA from paired blood pellets and plasma samples. Importantly, all P. vivax negative samples from the blood pellets were also confirmed plasma-negative, and parasitaemia in blood pellets was higher compared to plasma samples. The results support investigations of P. vivax infections in archived sera or plasma collections with a high degree of confidence to generate additional data on the neglected P. vivax malaria, and ultimately guide strategies to control the disease., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Sambe, Diagne, Diatta, Gaba, Sarr, Diatta, Diaw, Sané, Diouf, Vigan-Womas, Mbengue and Niang.)

Introduction: Urachus is an embryonic remnant that usually involutes before birth. Abnormal persistence of this structure gives embryologic malformation like an urachal cyst. Infection or malignancy degeneration can complicated it., Case Presentation: Case 1: We report 20 years old female patient consulted with acute abdominal pain. Clinical examination showed fever and infra-umbilical tender mass. The abdominal Computerized Tomography showed pelvic mass between umbilicus and bladder. The open laparotomy found infra-abdominal semi-solid mass. A complete resection was done and histological exam confirmed infected urachal cyst. Case 2: A 19 years old male patient presented with abdominal pain and fever. Physical examination found tenderness in lower abdomen. Biology revealed leukocytosis, and Ultrasonography found a heterogeneous infra-umbilical mass. Surgical exploration by mini-laparotomy found an abscess urachal cyst that is confirm by histological exam after complete resection., Clinical Discussion: Urachal cyst in adult patient is rare. Clinical symptoms without complications are insignificant. Because of malignancy risk, adult urachal cyst are managed by surgery., Conclusion: Infection cyst is the most common complication of urachal cyst. Complete resection is recommended because of malignancy degeneration risk., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Peanuts and peanut products are significant revenue sources for smallholder farmers in the Senegalese peanut basin. However, microbial contamination during production and storage can greatly affect market access for producers. Peanut products have emerged as possible sources of foodborne illness, encouraging discussions on international standards for peanuts. In this study, we interviewed 198 households throughout the Senegalese peanut basin to assess current production practices, storage methods, and producers' prior knowledge of microbial contamination using a 162-question survey. A member of each household orally completed the survey with a trained enumerator and the results were compared to microbiological results obtained from peanut samples collected at the time of the interview using linear regression and an analysis of variance model. Samples were collected from stored peanuts at each household; peanuts were shelled and total Enterobacteriaceae, coliform, and yeast and mold populations were enumerated. Of the 198 samples analyzed, 13.0% and 13.6% were greater than the upper detection limits for Enterobacteriaceae and coliforms, respectively. A total of 21.2% of samples were above the detection limit for yeast and mold populations. Only 22.7% and 18.7% of producers were aware of pathogenic bacteria or aflatoxins, respectively; there were no significant differences in observed microbial populations between household who took preventative measures against microbial contamination and those who did not. Additionally, four households reported washing their kitchen utensils before using them to eat and 60.1% reported always washing their hands before eating. Enumerators were asked to report peanut storage container type and if the containers were stored off the ground at the time of collection. While the interaction between storage container type and if the container was stored off the ground was significant for Enterobacteriaceae and coliforms, it was not significant for yeast and mold. Additionally, when storage container type and if peanuts were stored off the ground were included in the regression model, these methods were predictive of contamination levels for Enterobacteriaceae and coliforms. To our knowledge, this is the first study to analyze the relationship among Enterobacteriaceae, coliforms, and yeast and mold contamination and producer knowledge of Senegalese peanuts. These results provide preliminary data to inform future studies to determine pathogen prevalence and impactful preventative measures to minimize microbial contamination of peanuts produced in Senegal., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Mass drug administration (MDA) with azithromycin is a cornerstone of the trachoma elimination strategy. Although the global prevalence of active trachoma has declined considerably, prevalence persists or even increases in some communities and districts. To increase understanding of MDA impact, we investigated the prevalence of active trachoma and ocular C. trachomatis prevalence, organism load, and circulating strains at baseline and one-year post-MDA in The Gambia and Senegal., Methods: Pre- and one-year post-MDA, children aged 0-9 years were examined for clinical signs of trachoma in six Gambian and 12 Senegalese villages. Ocular swabs from each child's right conjunctiva were tested for evidence of ocular C. trachomatis infection and organism load (ompA copy number), and ompA and multi-locus sequence typing (MLST) was performed., Results: A total of 1171 children were examined at baseline and follow-up in The Gambia. Active trachoma prevalence decreased from 23.9% to 17.7%, whereas ocular C. trachomatis prevalence increased from 3.0% to 3.8%. In Senegal, 1613 and 1771 children were examined at baseline and follow-up, respectively. Active trachoma prevalence decreased from 14.9% to 8.0%, whereas ocular C. trachomatis prevalence increased from 1.8% to 3.6%. Higher organism load was associated with having active trachoma and severe inflammation. Sequence typing demonstrated that all Senegalese samples were genovar A, whereas Gambian samples were a mix of genovars A and B. MLST provided evidence of clustering at village and household levels and demonstrated differences of strain variant frequencies in Senegal, indicative of an "outbreak". MLST, including partial ompA typing, provided greater discriminatory power than complete ompA typing., Conclusions: We found that one round of MDA led to an overall decline in active trachoma prevalence but no impact on ocular C. trachomatis infection, with heterogeneity observed between villages studied. This could not be explained by MDA coverage or number of different circulating strains pre- and post-MDA. The poor correlation between active trachoma and infection prevalence supports the need for further work on alternative indicators to clinical signs for diagnosing ocular C. trachomatis infection. MLST typing has potential molecular epidemiology utility, including better understanding of transmission dynamics, although relationship to whole-genome sequence variability requires further exploration.

Improvement of the TIFD method to determine buprofezin (BUP) founded on the O-phthalaldehyde (OPA)-thermoproduct complex of buprofezin (OPA-BUP) with dimethyl-β-cyclodextrin (DMβCD) was investigated at 25 °C. The TIFD method developed in DMβCD medium, was optimized with respect to the reaction time, DMβCD concentration and pH. Based on the inclusion reaction, the OPA-BUP: DMβCD inclusion complex was developed in two aqueous media pH 7 and pH 13. A 1:1 stoichiometric ratio of OPA-BUP: DMβCD complex was obtained. The binding constants (K) and Gibbs energy (ΔG°) values increasing and decreasing with pH, respectively, show the spontaneous and thermodynamically favorable at 25 °C of the inclusion complexes formation. Normalized TIFD spectra were measured at 425 nm for emission and at 345 nm for excitation. Limits of detection (LOD) and quantification (LOQ) obtained, according to the pH, were in the ranges 0.05-0.1 ng mL ̶ 1 and 0.2-0.4 ng mL ̶ 1 , respectively. Relative standard deviation (RSD) values, less than 1.3% corroborated TIFD method repeatability in DMβCD medium. Solid phase extraction (SPE) procedure which was used for quantitative analysis of natural water samples collected from Niayes area, led to satisfactory recovery rates values 99.5-117.3%.

Background: Plasmodium falciparum may evade complement-mediated host defense by hijacking complement Factor H (FH), a negative regulator of the alternative complement pathway. Plasma levels of FH vary between individuals and may therefore influence malaria susceptibility and severity., Methods: We measured convalescent FH plasma levels in 149 Gambian children who had recovered from uncomplicated or severe P. falciparum malaria and in 173 healthy control children. We compared FH plasma levels between children with malaria and healthy controls, and between children with severe (n = 82) and uncomplicated malaria (n = 67). We determined associations between FH plasma levels and laboratory features of severity and used multivariate analyses to examine associations with FH when accounting for other determinants of severity., Results: FH plasma levels differed significantly between controls, uncomplicated malaria cases, and severe malaria cases (mean [95% confidence interval], 257 [250 to 264], 288 [268 to 309], and 328 [313 to 344] µg/mL, respectively; analysis of variance P < .0001). FH plasma levels correlated with severity biomarkers, including lactate, parasitemia, and parasite density, but did not correlate with levels of PfHRP2, which represent the total body parasite load. Associations with severity and lactate remained significant when adjusting for age and parasite load., Conclusions: Natural variation in FH plasma levels is associated with malaria susceptibility and severity. A prospective study will be needed to strengthen evidence for causation, but our findings suggest that interfering with FH binding by P. falciparum might be useful for malaria prevention or treatment.

Cytosine DNA methylation is an epigenetic regulatory system used by plants to control gene expression. Methylation pattern always changes after abiotic stresses, pathogens and pest infections or after a treatment with salicylic acid (SA). The latter is a key player in plant development and defense against insect herbivores, pathogens, and abiotic stresses. The roles of SA on the methylation patterns and the plant development were performed in 4 pearl millet (Pennisetum glaucum) varieties. Seedlings of 4 early-flowering photosensitive genotypes (PMS3, PMI8, PMG, and PMT2) were grown on MS medium supplemented with null or different doses of SA. Root growth was used as a parameter to evaluate the effects of SA at early stage development. DNA from these seedlings was extracted and Methylation-Sensitive Amplified Polymorphism (MSAP) was measured to assess the effects of SA on methylome. The methylation analysis revealed that SA treatment decreased the methylation, while inhibiting the root growth for all varieties tested, except in PMG at 0.5 mM, indicating a dose and a genotype response-dependence. The methylation level was positively correlated with the root growth. This suggests that SA influences both the methylome by demethylation activities and the root growth by interfering with the root development-responsive genes. The demethylation process, induced by the REPRESSOR OF SILCENCING 1 (ROS1) may activate R genes, or GH3.5 and downregulate the hormonal pathway under root development. These findings showed the pearl millet metabolism prioritized and promoted the defense pathways over vegetative development during stress.

Chlamydia trachomatis causes both trachoma and sexually transmitted infections. These diseases have similar pathology and potentially similar genetic predisposing factors. We aimed to identify polymorphisms and pathways associated with pathological sequelae of ocular Chlamydia trachomatis infections in The Gambia. We report a discovery phase genome-wide association study (GWAS) of scarring trachoma (1090 cases, 1531 controls) that identified 27 SNPs with strong, but not genome-wide significant, association with disease (5 × 10(-6) > P > 5 × 10(-8)). The most strongly associated SNP (rs111513399, P = 5.38 × 10(-7)) fell within a gene (PREX2) with homology to factors known to facilitate chlamydial entry to the host cell. Pathway analysis of GWAS data was significantly enriched for mitotic cell cycle processes (P = 0.001), the immune response (P = 0.00001) and for multiple cell surface receptor signalling pathways. New analyses of published transcriptome data sets from Gambia, Tanzania and Ethiopia also revealed that the same cell cycle and immune response pathways were enriched at the transcriptional level in various disease states. Although unconfirmed, the data suggest that genetic associations with chlamydial scarring disease may be focussed on processes relating to the immune response, the host cell cycle and cell surface receptor signalling.

Background: The clinical signs of active trachoma are often present in the absence of ocular Chlamydia trachomatis infection in low prevalence and mass treated settings. Treatment decisions are currently based on the prevalence of clinical signs, and this may result in the unnecessary distribution of mass antibiotic treatment. We aimed to evaluate the diagnostic accuracy of a prototype point-of-care (POC) test, developed for field diagnosis of ocular C. trachomatis, in low prevalence settings of The Gambia and Senegal., Methodology/principal Findings: Three studies were conducted, two in The Gambia and one in Senegal. Children under the age of 10 years were screened for the clinical signs of trachoma. Two ocular swabs were taken from the right eye. The first swab was tested by the POC test in the field and the result independently graded by two readers. The second swab was tested for the presence of C. trachomatis by Amplicor Polymerase Chain Reaction. In Senegal, measurements of humidity and temperature in the field were taken. A total of 3734 children were screened, 950 in the first and 1171 in the second Gambian study, and 1613 in Senegal. The sensitivity of the prototype POC test ranged between 33.3-67.9%, the specificity between 92.4-99.0%, the positive predictive value between 4.3-21.0%, and the negative predictive value between 98.0-99.8%. The rate of false-positives increased markedly at temperatures above 31.4°C and relative humidities below 11.4%., Conclusions/significance: In its present format, this prototype POC test is not suitable for field diagnosis of ocular C. trachomatis as its specificity decreases in hot and dry conditions: the environment in which trachoma is predominantly found. In the absence of a suitable test for infection, trachoma diagnosis remains dependent on clinical signs. Under current WHO recommendations, this is likely resulting in the continued mass treatment of non-infected communities.

Background: Trachoma has been endemic in The Gambia for decades. National trachoma control activities have been in place since the mid-1980's, but with no mass antibiotic treatment campaign. We aimed to assess the prevalence of active trachoma and of actual ocular Chlamydia trachomatis infection as measured by polymerase chain reaction (PCR) in the two Gambian regions that had had the highest prevalence of trachoma in the last national survey in 1996 prior to planned national mass antibiotic treatment distribution in 2006., Methodology/principal Findings: Two stage random sampling survey in 61 randomly selected Enumeration Areas (EAs) in North Bank Region (NBR) and Lower River Region (LRR). Fifty randomly selected children aged under 10 years were examined per EA for clinical signs of trachoma. In LRR, swabs were taken to test for ocular C. trachomatis infection. Unadjusted prevalences of active trachoma were calculated, as would be done in a trachoma control programme. The prevalence of trachomatous inflammation, follicular (TF) in the 2777 children aged 1-9 years was 12.3% (95% CI 8.8%-17.0%) in LRR and 10.0% (95% CI 7.7%-13.0%) in NBR, with significant variation within divisions (p<0.01), and a design effect of 3.474. Infection with C. trachomatis was found in only 0.3% (3/940) of children in LRR., Conclusions/significance: This study shows a large discrepancy between the prevalence of trachoma clinical signs and ocular C. trachomatis infection in two Gambian regions. Assessment of trachoma based on clinical signs alone may lead to unnecessary treatment, since the prevalence of active trachoma remains high but C. trachomatis infection has all but disappeared. Assuming that repeated infection is required for progression to blinding sequelae, blinding trachoma is on course for elimination by 2020 in The Gambia.

Background: Trachoma, caused by ocular infection with Chlamydia trachomatis, remains the leading infectious cause of blindness and in 2002 was responsible for 3.6% of total global blindness. Although transmission can be successfully interrupted using antibiotics and improvements in public and personal hygiene, the long-term success of the control programmes advocated by the World Health Organization are still uncertain. For the complete control and prevention of trachoma, a vaccine would be highly desirable. Currently there are no licensed vaccines for trachoma, and no human vaccine trials have been conducted since the 1960s. A barrier to new attempts to design and introduce a vaccine is the identification of immunologic correlates of protective immunity or immunopathology. We studied important correlates of the immune response in a trachoma-endemic population in order to improve our knowledge of this disease. This is essential for the successful development of a vaccine against both ocular and genital C. trachomatis infection., Methods and Findings: We used quantitative real-time PCR for C. trachomatis 16S rRNA to identify conjunctival infection. The expression of IFN-gamma, IDO, IL-10, and FOXP3 mRNA transcripts was measured. We evaluated the role of immune effector and regulatory responses in the control of chlamydial infection and in the resolution of clinical signs of trachoma in endemic communities in Gambia. All host transcripts examined were detectable even in normal conjunctiva. The levels of these transcripts were increased, compared to normal uninfected conjunctiva, when infection was detected, with or without clinical disease signs. Interestingly, when clinical disease signs were present in the absence of infection, the expression of a regulatory T cell transcription factor, FOXP3, remained elevated., Conclusions: There is evidence of an increase in the magnitude of the local anti-chlamydial cytokine immune responses with age. This increase is coupled to a decline in the prevalence of infection and active trachoma, suggesting that effective adaptive immunity is acquired over a number of years. The anti-chlamydial and inflammatory immune response at the conjunctival surface, which may control chlamydial replication, is closely matched by counter inflammatory or regulatory IL-10 expression. Differences in the level of FOXP3 expression in the conjunctiva may indicate a role for regulatory T cells in the resolution of the conjunctival immune response, which is important in protection from immunopathology. However, the expression of cytokines that control chlamydial replication and those that regulate the conjunctival immune response is not simply juxtaposed; the interaction between the infection and the clinical disease process is therefore more complex.

Chlamydia-specific cytotoxic T lymphocytes are able to control model infections but may be implicated in disease pathogenesis. HLA-A2 peptide tetramers to Chlamydia trachomatis major outer membrane protein 258-266 (MOMP258-266) and MOMP260-268 were used to characterize HLA class I-restricted CD8+ T cells in Gambian children aged 4 to 15 years with clinical signs of active trachoma and/or infection with C. trachomatis. The frequencies of circulating HLA-A2 tetramer binding cells (TBC) were determined in whole blood samples by flow cytometric analysis. Initial screening of subjects with an anti-HLA-A2 antibody confirmed the presence of either HLA-A2 or HLA-A28. These were subsequently further divided by molecular subtyping. The C. trachomatis-specific HLA-A2 peptide tetramers were able to bind T cells with receptors from subjects which were restricted by either the HLA-A2 or the HLA-A28 restriction element. In this population, the median value of C. trachomatis-specific CD8+ T cells was 0.02%, with frequencies of up to 3.71% of CD8+ T cells reactive with a single tetramer in a minority of subjects. TBC were detected more often in subjects who were infected at the ocular surface, and their presence was associated with infection episodes of longer duration. Detection of C. trachomatis-specific TBC was not associated with the presence of disease or with the estimated load of ocular C. trachomatis infection at the time of sample collection. High frequencies of C. trachomatis-specific cells did not predict subsequent appearance or resolution of the clinical disease signs of active trachoma.

The spatial distribution of motile life stages of the two-spotted spider mite Tetranychus urticae Koch in Kenyan small-scale tomato fields was described by Taylor's power law and an enumerative sampling plan was designed for research purposes. The exponential increase of T. urticae populations during three growing seasons permits the development and use of a simple exponential model for the design of a threshold-based chemical control system. For this purpose, a critical threshold of 440 motile mites per sample unit at the end of the growing season (12 weeks after transplanting) was translated into a proportion of 0.83 infested units in sample 3, i.e. five weeks after transplanting. A sequential binomial sampling plan with respect to the proportion of 0.83, five weeks after transplanting, was designed. The exponential model was extended to account for the influence of weather and host plant species. Model development and parameter estimation were based on three data sets (Kenyan tomato fields, Italian and Californian strawberry fields). The model satisfactorily predicted a positive influence on growth rates by (i) changing the host plant from tomato to strawberry, and (ii) temperature, while a negative effect resulted from (iii) rainfall; both (ii) and (iii) are controlled by temperature-rainfall interactions. In contrast, the estimated parameter values did not satisfactorily describe the expected responses at specific temperature and rainfall values. Nevertheless, the model allowed the rating of host plant species in the field. A fourth data set from Swiss apple orchards was used to test the model, and population build-up on the apple host plant appeared to be higher than on tomatoes but lower than on strawberry.