Nested Analysis Of Variance Research Articles

Morphological leaf variability in natural populations of Pistacia atlantica Desf. subsp. atlantica along climatic gradient: new features to update Pistacia atlantica subsp. atlantica key.

The effect of bioclimate range on the variation in Pistacia atlantica Desf. subsp. atlantica leaf morphology was studied on 16 sites in Northwest Algeria. The study examined biometrically mature leaves totaling 3520 compound leaves. Fifteen characters (10 quantitative and 5 qualitative) were assessed on each leaf. For each quantitative character, the nested analysis of variance (ANOVA) was used to examine relative magnitude of variation at each level of the nested hierarchy. The correlation between the climatic parameters and the leaf morphology was examined. The statistical analysis applied on the quantitative leaf characters showed highly significant variation at the within-site level and between-site variation. The correlation coefficient (r) showed also an important correlation between climatic parameters and leaf morphology. The results of this study exhibited several values reported for the first time on the species, such as the length and the width of the leaf (reaching up to 24.5 cm/21.9 cm), the number of leaflets (up to 18 leaflets/leaf), and the petiole length of the terminal leaflet (reaching up to 3.4 cm). The original findings of this study are used to update the P. atlantica subsp. atlantica identification key.

Reference intervals for plasma-free amino acid in a Japanese population.

Plasma amino acid concentrations vary with various diseases. Although reference intervals are useful in daily clinical practice, no reference intervals have been reported for plasma amino acids in a large Japanese population. Reference individuals were selected from 7685 subjects examined with the Japanese Ningen Dock in 2008. A total of 1890 individuals were selected based on exclusion criteria, and the reference samples were selected after the outlier samples for each amino acid concentration were excluded. The lower limit of the reference intervals for the plasma amino acid concentrations was set at the 2.5th percentile and the upper limit at the 97.5th percentile. By use of the nested analysis of variance, we analysed a large dataset of plasma samples and the effects of background factors (sex, age and body mass index [BMI]) on the plasma amino acid concentrations. Most amino acid concentrations were related to sex, especially those of branched-chained amino acid. The citrulline, glutamine, ornithine and lysine concentrations were related to age. The glutamate concentration was related to body mass index. The concentrations of most amino acids are more strongly related to sex than to age or body mass index. Our results indicate that the reference intervals for plasma amino acid concentrations should be stratified by sex when the background factors of age and body mass index are considered.

Analysis of flexible substrates for clinical translation of laser-generated shockwave therapy.

Bacteria biofilms in chronically infected wounds significantly increase the burden of healthcare costs and resources for patients and clinics. Because biofilms are such an effective barrier to standard antibiotic treatment, new methods of therapy need to be developed to combat these infections. Our group has demonstrated the potential of using Laser Generated Shockwaves as a potential therapy to mechanically disrupt the bacterial biofilms covering the wound. Previous studies have used rigid silica glass as the shockwave propagation medium, which is not compatible with the intended clinical application. This paper describes the exploration of five candidate flexible plastic films to replace the glass substrate. Each material measured 0.254 mm thick and was used to generate shockwaves of varying intensities. Shockwave characterization was performed using a high-speed Michelson displacement interferometer and peak stress values obtained in the flexible substrates were compared to glass using one-way nested Analysis of Variance and Tukey HSD post-hoc analysis. Results demonstrate statistically significant differences between substrate material and indicate that polycarbonate achieves the highest peak stress for a given laser fluence suggesting that it is optimal for clinical applications.

Influence of nanoparticles on color stability, microhardness, and flexural strength of acrylic resins specific for ocular prosthesis.

The aim of this study was to assess the effect of adding nanoparticles to N1 acrylic resin intended for artificial sclera, in terms of the color stability, microhardness, and flexural strength of the resin. Three hundred samples of N1 acrylic resin were used: 100 samples for color stability and microhardness tests (each test was performed on the opposite side of each sample), and 200 samples for flexural strength testing (100 samples before and after 1,008 hours of accelerated aging). Samples for each test were separated into ten groups (n=10), ie, without nanoparticles (control group) or with nanoparticles of zinc oxide, titanium dioxide (TiO2), and barium sulfate at weight concentrations of 1%, 2%, and 2.5% (nanoparticle groups). Data were subjected to statistical analysis with nested analysis of variance and Tukey’s test (P<0.05 significance level). Among the nanoparticle groups, the TiO2 groups showed better color stability at all concentrations. Microhardness values increased after artificial aging, except for the control and zinc oxide groups. After aging, the 1%–2% TiO2 groups had significantly higher microhardness values compared with the other nanoparticle groups. Before aging, there was a significant difference in flexural strength between the control and nanoparticle groups. After aging, the control and TiO2 groups, regardless of concentration, showed the lowest flexural strength values. Incorporation of nanoparticles directly influenced the acrylic resin properties, with TiO2 being the most influential nanoparticle in terms of the evaluated properties.

Does the Sequence of Instruction Matter During Simulation?

Instructional strategies must be balanced when subjecting students to full-immersion simulation so as not to discourage learning and increase cognitive overload. The purpose of this study was to determine if participating in a simulation exercise before lecture yielded better performance outcomes among novice learners. Twenty-nine participants were divided into 2 groups as follows: group 1 participated in simulation exercises followed by a didactic lecture and group 2 participated in the same learning activities presented in the opposite order. Participants were administered a multiple-choice cognitive assessment upon completion of a workshop. Learners who participated in the simulated exercises followed by the didactic lecture performed better on postassessments as compared with those who participated in the simulation after the lecture. A repeated-measures or nested analysis of variance generated statistically significant results in terms of model fit F (α=0.05; 4.54)=176.07 with a P<0.0001. Despite their higher levels of increased performance, 76% of those who participated in simulation activities first indicated that they would have preferred to participate in a lecture first. The findings of this study suggest that differences occur among learners when the sequencing of instructional components is altered. Learners who participated in simulation before lecture demonstrated increased knowledge compared with learners who participated in simulation after a lecture.

High-dimensional nested analysis of variance to assess the effect of production season, quality grade and steam pasteurization on the phenolic composition of fermented rooibos herbal tea

A nested analysis of variance combined with simultaneous component analysis, ASCA, was proposed to model high-dimensional chromatographic data. The data were obtained from an experiment designed to investigate the effect of production season, quality grade and post-production processing (steam pasteurization) on the phenolic content of the infusion of the popular herbal tea, rooibos, at ‘cup-of-tea’ strength. Specifically, a four-way analysis of variance where the experimental design involves nesting in two of the three crossed factors was considered.For the purpose of the study, batches of fermented rooibos plant material were sampled from each of four quality grades during three production seasons (2009, 2010 and 2011) and a sub-sample of each batch was steam-pasteurized. The phenolic content of each rooibos infusion was characterized by high performance liquid chromatography (HPLC)-diode array detection (DAD). In contrast to previous studies, the complete HPLC-DAD signals were used in the chemometric analysis in order to take into account the entire phenolic profile.All factors had a significant effect on the phenolic content of a ‘cup-of-tea’ strength rooibos infusion. In particular, infusions prepared from the grade A (highest quality) samples contained a higher content of almost all phenolic compounds than the lower quality plant material. The variations of the content of isoorientin and orientin in the different quality grade infusions over production seasons are larger than the variations in the content of aspalathin and quercetin-3-O-robinobioside. Ferulic acid can be used as an indicator of the quality of rooibos tea as its content generally decreases with increasing tea quality. Steam pasteurization decreased the content of the majority of phenolic compounds in a ‘cup-of-tea’ strength rooibos infusion.

A comparison of inshore marine soundscapes

Sound travels well through water and is capable of conveying information to any listener on both the presence of particular organisms and the quality of the environment. Many marine organisms use sounds to navigate, forage and communicate, while different marine habitats often have their own acoustical characteristics. However, there are still large gaps in our knowledge of marine soundscapes, particularly in regard to their spatial patterns. The goal of this research was to investigate passive acoustic monitoring as an ecological survey technique. The specific objectives were to compare soundscapes between and within benthic habitats and to evaluate the influence of different environmental factors. Acoustic recordings were made in Lough Hyne, Ireland during May 2012, following a nested design in three benthic habitats; Mud, Gravel and Cliff. Three patches of each habitat were selected using hydro-acoustic and underwater video surveys and within each patch five different sites were monitored (n=45). A nested analysis of variance (ANOVA) showed that acoustic profiles differed significantly within but not between habitats, although unique acoustic signatures existed over different spatial ranges, illustrating a degree of stability at local patch level. A distinct peak (2–4kHz) in acoustic complexity was observed in all habitat patches but one, and was caused by the presence of transient broadband pulses or snaps. These snaps were attributed to the presence of snapping shrimp (family Alpheidae), found at a particular location within the lough. Other distinctive sounds of suspected biological origin were identified in particular habitat patches (Cliff and Gravel) and suggested the presence of habitat related biophonies. Soundscape signatures of different patches were strongly correlated with proximity to the source of the high-energy snaps, indicating that location was more important than habitat in determining soundscape characteristics. Other environmental factors such as bottom type and depth were less important. It is evident that acoustical sources of high energy and broadband properties have pervasive effects over considerable distances (up to 1km). The acoustic characteristics of a habitat patch were greatly influenced by extraneous sounds, in this case from a biological source. The high acoustic connectedness of marine habitats underlines the need for evaluating the impact of anthropogenic activities, particularly for ecosystems with unique biophonies in need of protection. There is potential for developing passive acoustic monitoring as a principal method for surveying marine habitats and observing local processes at different spatial and temporal scales.

The geometric morphometrics and condition of Pontic shad, Alosa immaculata (Pisces: Clupeidae) migrants to the Danube River

Anadromous fish could have intraspecific groups with different life histories; identification of these is very important for management and conservation. Geometric morphometrics represents a quick and cost-effective method to identify such intraspecific groups. In this study, geometric morphometrics of Pontic shad (Alosa immaculata) migrants from the Danube River were investigated, as was Fulton's condition factor (K), hepatosomatic index (HSI) and gonadosomatic index (GSI). Pontic shad specimens were collected during April and May of 2004 and 2006. The sample comprised four groups (65 males and 56 females in 2004; 110 males and 78 females in 2006). Geometric morphometrics revealed differences in shape that were statistically significant for both year (nested analysis of variance: F = 13.84; p < 0.001) and sex (nested analysis of variance: sex nested in year, F = 1.71; p < 0.01). The major differences between years were in head shape and position of fins. The most significant difference between females and males was in the dorsolateral expansion of the mid-body section with emphasis on the higher dorsal part of the body. Values for K in this work (0.65–0.70) were the lowest recorded for Pontic shad in the Danube River. Additional investigations involving both geometric morphometrics and molecular genetics are necessary to confirm the presence of races. This could be important information for conservation purposes as Pontic shad is listed as Vulnerable on the International Union for Conservation of Nature list.

Confidence Intervals and Power Calculations for Within-Person Biological Variation: Effect of Analytical Imprecision, Number of Replicates, Number of Samples, and Number of Individuals

Reliable estimates of within-person biological variation and reference change value are of great importance when interpreting test results, monitoring patients, and setting quality specifications. Little information has been published regarding what experimental design is optimal to achieve the best estimates of within-person biological variation. Expected CIs were calculated for different balanced designs for a 2-level nested variance analysis model with varying analytical imprecision. We also simulated data sets based on the model to calculate the power of different study designs for detection of within-person biological variation. The reliability of an estimate for biological variation and a study's power is very much influenced by the study design and by the ratio between analytical imprecision and within-person biological variation. For a fixed number of measurements, it is preferable to have a high number of samples from each individual. Shortcomings in analytical imprecision can be controlled by increasing the number of replicates. The design of an experiment to estimate biological variation should take into account the analytical imprecision of the method and focus on obtaining the highest possible reliability. Estimates of biological variation should always be reported with CIs.

Genetic variance of tolerance and the toxicant threshold model

A statistical genetics method is presented for estimating the genetic variance (heritability) of tolerance to pollutants on the basis of a standard acute toxicity test conducted on several isofemale lines of cladoceran species. To analyze the genetic variance of tolerance in the case when the response is measured as a few discrete states (quantal endpoints), the authors attempted to apply the threshold character model in quantitative genetics to the threshold model separately developed in ecotoxicology. The integrated threshold model (toxicant threshold model) assumes that the response of a particular individual occurs at a threshold toxicant concentration and that the individual tolerance characterized by the individual's threshold value is determined by genetic and environmental factors. As a case study, the heritability of tolerance to p-nonylphenol in the cladoceran species Daphnia galeata was estimated by using the maximum likelihood method and nested analysis of variance (ANOVA). Broad-sense heritability was estimated to be 0.199 ± 0.112 by the maximum likelihood method and 0.184 ± 0.089 by ANOVA; both results implied that the species examined had the potential to acquire tolerance to this substance by evolutionary change.

Spatial and temporal variations in the species composition and abundance of benthic molluscs along 4 rocky shores of Karachi

A total of 97 species of macromolluscs were collected from 4 rocky beaches (Manora, Buleji, Nathiagali, and Cape Monze) along the Karachi coast from December 1993 to December 1995. More species were recorded from Buleji (68) and Manora (63) than from Nathiagali (55) and Cape Monze (57). Gastropods dominated at all 4 of the sites studied. Four species were commonly abundant at all 4 sites: Turbo coronatus, Nerita albicilla, Morula granulata, and Cerithium rubus. The average number of species decreased with an increase in the tidal heights at Manora, Buleji, and Nathiagali, whereas this was greater in the high tidal zone at Cape Monze's rocky shore. The average number of individuals of molluscs was greater in the midtidal zone at the Manora and Buleji rocky shores, whereas it was greater in the low tidal zone at Nathiagali and Cape Monze. Two-way nested analysis of variance showed that the number of individual molluscs was significantly different among zones and among sites in most of the samples. Species richness, diversity, and evenness, however, were not found to be significantly different among zones and sites. Cluster analyses, derived from Bray-Curtis measures of similarity based on abundance data, showed the discrimination between carnivore gastropods and an increase in the abundance of herbivore gastropod molluscs. Differences in community structure amongst sites appeared to be due to habitat structure, substrate instability, human disturbances, and degree of exposure.

On Three-Way Unbalance Nested Analysis of Variance

Problem statement: In this study, we give a simple analytically tract able procedure for solving three-way unbalanced nested Analysis of Variance (ANOVA). In many realistic situations, unbalanced design was unavoidable due to natural co nstraints and missing data. Approach: Here, we present a comprehensive approach for addressing sol utions of problems arising from unbalanced nested ANOVA. We consider the F-statistics under the different models. Results: Special attention was given to the construction of approximate F-test where exact F-test does not exist. Pseudo-degrees of freedoms were derived using the Satterthwaite's type approximation. Conclusion: In all derivations, we assume that the effects act independently and th at the mean squares are independent. A numerical example is given to illustrate the solution procedu re.

Advantages of the lognormal approach to determining reference change values for N-terminal propeptide B-type natriuretic peptide

BackgroundSerial measurement of NT-proBNP is performed routinely in the monitoring and assessment of the effectiveness of therapy in patients being treated for chronic heart failure (CHF). Intra-individual changes in NT-proBNP levels over time are compared typically to a reference change value (RCV) determined using either a standard [i.e., nested analysis of variance (nANOVA)] or a lognormal approach. The RCV defines the minimum percent change in serial analyte values that exceeds the percent change expected due to biological variation alone. Currently, there is no consensus on which approach (nANOVA or lognormal) to determining RCV is better. AimsBased on these considerations, we aimed to illustrate the impact of data transformation on the calculation of the biological variation of NT-proBNP and discuss the utility of logarithmic transformation in monitoring patients with heart failure. Methods15 healthy subjects were enrolled after informed consent; 5 blood specimens were collected twice a week. Nested ANOVA from replicate analyses was applied to obtain components of biological variation, on the raw data and after data transformation. ResultsNT-proBNP distribution being highly skewed required data transformation. Natural log transformation yielded normalization. An example demonstrates that for untransformed values the RCV was overestimated for low concentrations of NT-proBNP and underestimated for higher concentrations. ConclusionsLog-transformed data are often used in the establishment of reference intervals for evaluating laboratory tests results in clinical practice, especially when the reference interval data are not Gaussian distributed. As log-normal approach is the best approach to determining RCV values we encourage its use assessing the clinical utility of NT-proBNP serial testing. We propose that the log-normal approach becomes the standard approach to determining RCV and replaces the use of nANOVA.

Can a Teaching Intervention Reduce Interobserver Variability in LVEF Assessment: A Quality Control Exercise in the Echocardiography Lab

This study sought to determine whether a formalized teaching intervention could reduce the interobserver variability (IOV) in visual estimation of left ventricular ejection fraction (LVEF) within a group of sonographers and physicians with a spectrum of experience. Precise and reliable echocardiographic assessment of LVEF is necessary for clinical decision-making and minimizing duplicative testing. Skill in the visual estimation of LVEF varies depending on experience and is critical for corroborating EF quantification. IOV may also lead to inconsistency if multiple readers are assessing the EF on serial exams. Fourteen cases of 2-dimensional echocardiograms were shown to 25 participants who estimated the EF based on a complete assessment of LV wall motion including parasternal, short-axis, apical, and subcostal views. The cases represented a spectrum of EF range, image quality, and clinical context. Following the initial interpretations, participants underwent a teaching intervention involving tutorial review of reference cases and group discussion of each case with determination of the EF guided by quantitative measure (biplane Simpson method). Three months after the teaching intervention, 14 new cases were shown to the 25 participants following the same methodology. IOV was quantified before and after the teaching intervention with the use of a 3-factor, nested analysis of variance. The factors were: observer, patient, and pre- and post-intervention (time). The analysis of variance showed that the intervention reduced the IOV for the 25 readers between the pre- and post-intervention assessments (F = 2.8, p = 0.007). The IOV decreased from ± 14% EF prior to intervention to ± 8.4% EF following intervention (a 40% reduction in IOV). In a large echocardiography laboratory with a wide range of training levels and experience, a simple, formalized teaching intervention can successfully diminish IOV of LVEF assessment. This intervention provides not only discrete quality measures, but also serves as a practical tool to document and improve quality of reporting, potentially reducing clinical inefficiencies and repeat testing.

An appraisal of statistical procedures used in derivation of reference intervals

When conducting studies to derive reference intervals (RIs), various statistical procedures are commonly applied at each step, from the planning stages to final computation of RIs. Determination of the necessary sample size is an important consideration, and evaluation of at least 400 individuals in each subgroup has been recommended to establish reliable common RIs in multicenter studies. Multiple regression analysis allows identification of the most important factors contributing to variation in test results, while accounting for possible confounding relationships among these factors. Of the various approaches proposed for judging the necessity of partitioning reference values, nested analysis of variance (ANOVA) is the likely method of choice owing to its ability to handle multiple groups and being able to adjust for multiple factors. Box-Cox power transformation often has been used to transform data to a Gaussian distribution for parametric computation of RIs. However, this transformation occasionally fails. Therefore, the non-parametric method based on determination of the 2.5 and 97.5 percentiles following sorting of the data, has been recommended for general use. The performance of the Box-Cox transformation can be improved by introducing an additional parameter representing the origin of transformation. In simulations, the confidence intervals (CIs) of reference limits (RLs) calculated by the parametric method were narrower than those calculated by the non-parametric approach. However, the margin of difference was rather small owing to additional variability in parametrically-determined RLs introduced by estimation of parameters for the Box-Cox transformation. The parametric calculation method may have an advantage over the non-parametric method in allowing identification and exclusion of extreme values during RI computation.

Geostatistics explained: an introductory guide for earth scientists

Preface 1. Introduction 2. 'Doing science' - hypotheses, experiments and disproof 3. Collecting and displaying data 4. Introductory concepts of experimental design 5. Doing science responsibly and ethically 6. Probability helps you make a decision about your results 7. Working from samples - data, populations and statistics 8. Normal distributions - tests for comparing the means of one and two samples 9. Type 1 and type 2 error, power and sample size 10. Single factor analysis of variance 11. Multiple comparisons after ANOVA 12. Two-factor analysis of variance 13. Important assumptions of analysis of variance: transformations and a test for equality of variances 14. Two-factor analysis of variance without replication, and nested analysis of variance 15. Relationships between variables: linear correlation and linear regression 16. Linear regression 17. Non-parametric statistics 18. Non-parametric tests for nominal scale data 19. Non-parametric tests for ratio, interval or ordinal scale data 20. Introductory concepts of multivariate analysis 21. Introductory concepts of sequence analysis 22. Introductory concepts of spatial analysis 23. Choosing a test Appendix A. Critical values of chi-square, Student's t and F Appendix B. Answers to questions References Index.

Process Robustness of Hot Embossing Microfluidic Devices

Polymeric substrates have significant advantages over silicon and glass for use in microfluidics. However, before polymer microfluidic devices can be mass produced, it must be shown that the manufacturing method used to create these devices is robust and repeatable. For this paper, a polymer manufacturing process, hot embossing, was used to produce microsized features in polymethylmethacrylate (PMMA) chips. A design of experiments that varied two factors during the hot embossing process (temperature and pressure), was conducted to determine the robustness of hot embossing microsized channels in PMMA. The channel height and width were measured at three sites on each chip, and the results were analyzed in two ways: response surface modeling (RSM) and nested variance analysis. For the RSM analysis, two separate ANOVA tests and regressions were performed on both channel width and channel height to obtain the response surface models between temperature, pressure and the channel width and height. Furthermore, the variance of channel width and height at each design point was determined and then two ANOVA tests and two separate regressions were performed to obtain the response surface models between temperature, pressure and the variance of channel height and channel width. This analysis was used to determine if hot embossing microfluidic devices is a robust process capable of producing quality parts at different operating conditions. The nested variance analysis was used to determine the primary source of the variation in channel height and width. For the nested variance analysis, two separate calculations were performed in order to determine whether the variance of channel width and height is mostly caused by within-chip variance or chip-to-chip variance. The analysis showed that the channel widths and heights were statistically equal across the four different operating points used (the low-temperature, low-pressure point was omitted). The variance of channel width and the variance of channel height remained constant in the desired operating region. Based on this analysis, it was concluded that hot embossing is a robust process for features on the order of 50 μm. Furthermore, the nested variance analysis showed that the variance of channel width and height is mostly caused by site-to-site measurements on a chip rather than between-chip variance. Therefore, it was determined that hot embossing microfluidic devices are repeatable and consistent from chip-to-chip.

Phenotypic Diversity of Natural Populations in Diospyros glaucifolia

12 phenotypic traits from leaves,fruits and seeds were investigated for 210 individuals in 7 natural populations of Diospyros glaucifolia from south-east China and the relationship between phenotypic variation of the natural populations and different distribution areas was discussed using variance analysis and nested variance analysis. The relationship among phenotypic variation of the natural populations, geo-ecological factors and morohlogical traits was discussed by correlation analysis. The results showed that there were significant differences in phenotypic variation among and within populations. It also showed that the diversity within populations was higher than that among populations. The average differentiation coefficient of seed traits is the smallest in all phenotypic traits.The traits stability of seeds was higher than that of other traits. There was no significant relationship between traits. The traits variation of natural populations were affected mainly by longitude (such as LL and LW) and height(such as seeds weight) in spatial distribution. The 7 populations investigated could be divided into five groups according to the cluster analysis.

Pseudoreplication conventions are testable hypotheses.

Hurlbert's conceptions of pseudoreplication, such as the loss of independent replicates with repeated sampling over time and the lack of appropriate spatial interspersion of experimental units to achieve statistical independence, are really theoretical hypotheses that warrant empirical confirmation or disconfirmation. Schank and Koehnle have provided a valuable service to researchers in ecology, conservation biology, and animal behavior using logical argument and repeated Monte Carlo simulations to challenge Hurlbert's theoretical assumptions about statistical independence. Their simulations showed that averaging samples to produce a single datum destroys the information within experimental units and is mathematically equivalent to the treatment level in a nested analysis of variance. Such results counter Hurlbert's argument that pooling is wrong. Rigid thinking about sampling, as engendered by Hurlbert's pseudoreplication arguments, does not promote the exploration of new methodologies and there is something disturbingly inconsistent with the scientific method when journal editors and reviewers adopt Hurlbert's pseudoreplication arguments unquestionably.

Blood parasites of the striped field mouse Apodemus agrarius and their morphological characteristics

Blood parasites of Apodemus agrarius were investigated in Eastern Slovakia during 1998–2005. The following parasitic species were detected: Trypanosoma grosi, Babesia microti-like piroplasms and Bartonella sp. Trypanosoma grosi was the most common species, with an infection prevalence of 12.7%. Trypanosomes were morphologically typical of the lewisi group, however, they were bigger than T. grosi described in A. flavicollis and A. sylvaticus. The differences analysed by nested analysis of variance were statistically significant. Pleomorphism was not observed. Infections with piroplasms were detected only at two sites, with an intensity of infection not exceeding 0.1%. The morphology of the piroplasms was different from those typical of B. microti. Bartonella occurred at two sites in 0.81% of the animals sampled. The prevalence of infection had a seasonal pattern throughout the study years. Trypanosomes occurred from July to November, with a peak in September, piroplasms occurred in May and June, and Bartonella sp. from May to July.