Seroepidemiology of SARS-CoV-2 in healthcare personnel working at the largest tertiary COVID-19 referral hospitals in Mexico City.

INTRODUCTION: We performed a longitudinal SARS-CoV-2 seroepidemiological study in healthcare personnel of the two largest tertiary COVID-19 referral hospitals in Mexico City. METHODS: All healthcare personnel, including staff physicians, physicians in training, nurses, laboratory technicians, researchers, students, housekeeping, maintenance, security, and administrative staff were invited to voluntarily participate, after written informed consent. Participants answered a computer-assisted self-administered interview and donated blood samples for antibody testing every three weeks from October 2020 to June 2021. RESULTS: A total of 883 participants (out of 3639 registered employees) contributed with at least one blood sample. The median age was 36 years (interquartile range: 28-46) and 70% were women. The most common occupations were nurse (28%), physician (24%), and administrative staff (22%). Two hundred and ninety participants (32.8%) had a positive-test result in any of the visits, yielding an overall adjusted prevalence of 33.5% for the whole study-period. Two hundred and thirty-five positive tests were identified at the baseline visit (prevalent cases), the remaining 55 positive tests were incident cases. Prevalent cases showed associations with both occupational (institution 2 vs. 1: adjusted odds ratio [aOR] = 2.24, 95% confidence interval [CI]: 1.54-3.25; laboratory technician vs. physician: aOR = 4.38, 95% CI: 1.75-10.93) and community (municipality of residence Xochimilco vs. Tlalpan: aOR = 2.03, 95% CI: 1.09-3.79) risk-factors. The incidence rate was 3.0 cases per 100 person-months. Incident cases were associated with community-acquired risk, due to contact with suspect/confirmed COVID-19 cases (HR = 2.45, 95% CI: 1.21-5.00). CONCLUSIONS: We observed that between October 2020 and June 2021, healthcare workers of the two largest tertiary COVID-19 referral centers in Mexico City had similar level of exposure to SARS-CoV-2 than the general population. Most variables associated with exposure in this setting pointed toward community rather than occupational risk. Our observations are consistent with successful occupational medicine programs for SARS-CoV-2 infection control in the participating institutions but suggest the need to strengthen mitigation strategies in the community.

Genomic Characterization of SARS-CoV-2 Isolated from Patients with Distinct Disease Outcomes in Mexico.

The coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has shown a wide spectrum of clinical manifestations ranging from asymptomatic infections to severe disease and death. Pre-existing medical conditions and age have been mainly linked to the development of severe disease; however, the potential association of viral genetic characteristics with different clinical conditions remains unclear. SARS-CoV-2 variants with increased transmissibility were detected early in the pandemics, and several variants with potential relevance for public health are currently circulating around the world. In this study, we characterized 57 complete SARS-CoV-2 genomes during the exponential growth phase of the early epidemiological curve in Mexico, in April 2020. Patients were categorized under distinct disease severity outcomes: mild disease or ambulatory care, severe disease or hospitalized, and deceased. To reduce bias related to risk factors, the patients were less than 60 years old and with no diagnosed comorbidities A trait-association phylogenomic approach was used to explore genotype-phenotype associations, represented by the co-occurrence of mutations, disease severity outcome categories, and clusters of Mexican sequences. Phylogenetic results revealed a higher genomic diversity compared to the initial viruses detected during the early stage of the local epidemic. We identified a total of 90 single nucleotide variants compared to the Wuhan-Hu-1 genome, including 54 nonsynonymous mutations. We did not find evidence for the co-occurrence of mutations associated with specific disease outcomes. Therefore, in the group of patients studied, disease severity was likely mainly driven by the host genetic background and other demographic factors. IMPORTANCE The genetic association of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) with different clinical conditions remains unclear and needs further investigation. In this study, we characterized 57 complete SARS-CoV-2 genomes from patients in Mexico with distinct disease severity outcomes: mild disease or ambulatory care, severe disease or hospitalized, and deceased. To reduce bias related to risk factors the patients were less than 60 years old and with no diagnosed comorbidities. We did not find evidence for the co-occurrence of mutations associated with specific disease outcomes. Therefore, in the group of patients studied, disease severity was likely mainly driven by the host genetic background and other demographic factors.

Assessment of the hemagglutinating activity of the Porcine orthorubulavirus.

Blue eye disease (BED) in pigs is caused by Porcine orthorubulavirus (PRV) of the Paramyxoviridae family. It is an endemic disease in swine production in the central region of Mexico and causes nervous signs and high mortality in suckling pigs, pneumonia in growing pigs, orchitis in boars and mummification during gestation. PRV hemagglutinates most red blood cells (RBCs) of domestic species. For serological diagnosis, the hemagglutination inhibition test is used, and in this test, guinea pig, bovine and chicken RBCs have been commonly used. In this investigation, hemagglutination with PRV was evaluated using the RBCs of seven domestic species (chicken, bovine, horse, pig, dog, guinea pig and rabbit). In the hemagglutination test, the following parameters were evaluated: temperature (25 °C and 37 °C), bottoms of the wells (V and U), erythrocyte concentration (0.5%, 0.75%, and 1%), and reading time (15, 30, 45, 60 and 90 min). Significant differences (P < 0.001) were found in most of the evaluated treatments. The best hemagglutination results were obtained with chicken, bovine and horse RBCs. The hemagglutination titer is higher (2 dilutions) when using chicken RBCs than when using bovine or horse RBCs. If chicken RBCs are used in the inhibition of hemagglutination, the test will be more sensitive, while it is more specific when bovine or horse RBCs are used. The hemagglutination readings are imprecise when using RBCs from dogs, pigs, guinea pigs and rabbits. RBCs from these species should not be used for the diagnosis or investigation of PRV.

Characteristics and growth of the genetic HIV transmission network of Mexico City during 2020.

INTRODUCTION: Molecular surveillance systems could provide public health benefits to focus strategies to improve the HIV care continuum. Here, we infer the HIV genetic network of Mexico City in 2020, and identify actively growing clusters that could represent relevant targets for intervention. METHODS: All new diagnoses, referrals from other institutions, as well as persons returning to care, enrolling at the largest HIV clinic in Mexico City were invited to participate in the study. The network was inferred from HIV pol sequences, using pairwise genetic distance methods, with a locally hosted, secure version of the HIV-TRACE tool: Seguro HIV-TRACE. Socio-demographic, clinical and behavioural metadata were overlaid across the network to design focused prevention interventions. RESULTS: A total of 3168 HIV sequences from unique individuals were included. One thousand and one-hundred and fifty (36%) sequences formed 1361 links within 386 transmission clusters in the network. Cluster size varied from 2 to 14 (63% were dyads). After adjustment for covariates, lower age (adjusted odds ratio [aOR]: 0.37, p<0.001; >34 vs. <24 years), being a man who has sex with men (MSM) (aOR: 2.47, p = 0.004; MSM vs. cisgender women), having higher viral load (aOR: 1.28, p<0.001) and higher CD4+ T cell count (aOR: 1.80, p<0.001; ≥500 vs. <200 cells/mm3 ) remained associated with higher odds of clustering. Compared to MSM, cisgender women and heterosexual men had significantly lower education (none or any elementary: 59.1% and 54.2% vs. 16.6%, p<0.001) and socio-economic status (low income: 36.4% and 29.0% vs. 18.6%, p = 0.03) than MSM. We identified 10 (2.6%) clusters with constant growth, for prioritized intervention, that included intersecting sexual risk groups, highly connected nodes and bridge nodes between possible sub-clusters with high growth potential. CONCLUSIONS: HIV transmission in Mexico City is strongly driven by young MSM with higher education level and recent infection. Nevertheless, leveraging network inference, we identified actively growing clusters that could be prioritized for focused intervention with demographic and risk characteristics that do not necessarily reflect the ones observed in the overall clustering population. Further studies evaluating different models to predict growing clusters are warranted. Focused interventions will have to consider structural and risk disparities between the MSM and the heterosexual populations.

Biological and physico-mechanical properties of poly (methyl methacrylate) enriched with graphene oxide as a potential biomaterial / Propiedades físicas-mecánicas-biológicas del poli (metilmetacrilato) enriquecido con óxido de grafeno como potencial biomaterial

Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulp-dental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: The GO was characterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical mechanical tests (flexural strength and elastic modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's posthoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 µm. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical mechanical properties of PMMA.

Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulpdental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: T he G O w as c haracterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical-mechanical tests (flexural strength and elastic modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's post-hoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 ?m. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical-mechanical properties of PMMA.

Near point-of-care, point-mutation test to detect drug resistance in HIV-1: a validation study in a Mexican cohort.

OBJECTIVE: Pretreatment HIV-drug resistance (PDR, HIVDR) to non-nucleoside reverse transcriptase inhibitors (NNRTIs) is increasing globally. NNRTIs continue to be used as first-line antiretroviral therapy (ART) in some communities due to the cost of dolutegravir-based ART or dolutegravir-associated adverse events. A simplified version of the oligonucleotide ligation assay (OLA) - 'OLA-Simple' - is a low-cost, near point-of-care assay that provides ready-to-use lyophilized reagents and reports HIVDR mutations as colored lines on lateral flow strips. Our objective was to design and validate OLA-Simple for a Mexican cohort. DESIGN: OLA-Simple probes to detect K65R, K103N/S, Y181C, M184V, and G190A were optimized for HIV Mexican sequences. Sixty clinical plasma specimens were analyzed by OLA-Simple by technicians blinded to Illumina-MiSeq sequences, and HIVDR results were compared. METHODS: Plasma RNA was tested using OLA-Simple kits. OLA-Simple lateral flow strips were read by in-house software, and were classified as mutant or wild-type at each codon. The comparison of results by OLA-Simple and Miseq was used to generate receiver-operating characteristic curves. RESULTS: OLA-Simple PCR amplified 59 of 60 specimens and successfully genotyped 287 of 295 codons, with eight of 295 (2.7%) indeterminate results. Compared to MiSeq, OLA-Simple gave five of 295 (1.7%) false-positive and four of 295 (1.4%) false-negative results. Excluding indeterminate results, OLA-Simple classified mutant with an accuracy of 97.4 and 98.8% when using thresholds at 10 and 25% mutant within an individual's HIV quasispecies, respectively. CONCLUSIONS: Compared to MiSeq, OLA-Simple detected HIVDR with high sensitivity and accuracy. OLA-Simple could expand access to affordable and rapid HIVDR testing to guide appropriate ART choices in populations using NNRTI-based ART.

Pretreatment HIV drug resistance spread within transmission clusters in Mexico City.

BACKGROUND: Pretreatment HIV drug resistance (HIVDR) to NNRTIs has consistently increased in Mexico City during the last decade. OBJECTIVES: To infer the HIV genetic transmission network in Mexico City to describe the dynamics of the local HIV epidemic and spread of HIVDR. PATIENTS AND METHODS: HIV pol sequences were obtained by next-generation sequencing from 2447 individuals before initiation of ART at the largest HIV clinic in Mexico City (April 2016 to June 2018). Pretreatment HIVDR was estimated using the Stanford algorithm at a Sanger-like threshold (≥20%). Genetic networks were inferred with HIV-TRACE, establishing putative transmission links with genetic distances <1.5%. We examined demographic associations among linked individuals with shared drug resistance mutations (DRMs) using a ≥ 2% threshold to include low-frequency variants. RESULTS: Pretreatment HIVDR reached 14.8% (95% CI 13.4%-16.2%) in the cohort overall and 9.6% (8.5%-10.8%) to NNRTIs. Putative links with at least one other sequence were found for 963/2447 (39%) sequences, forming 326 clusters (2-20 individuals). The inferred network was assortative by age and municipality (P < 0.001). Clustering individuals were younger [adjusted OR (aOR) per year = 0.96, 95% CI 0.95-0.97, P < 0.001] and less likely to include women (aOR = 0.46, 95% CI 0.28-0.75, P = 0.002). Among clustering individuals, 175/963 (18%) shared DRMs (involving 66 clusters), of which 66/175 (38%) shared K103N/S (24 clusters). Eight municipalities (out of 75) harboured 65% of persons sharing DRMs. Among all persons sharing DRMs, those sharing K103N were younger (aOR = 0.93, 95% CI 0.88-0.98, P = 0.003). CONCLUSIONS: Our analyses suggest age- and geographically associated transmission of DRMs within the HIV genetic network in Mexico City, warranting continuous monitoring and focused interventions.

Sphingosine-1-phosphate (S1P) in ovarian physiology and disease.

Sphingosine-1-phoshate (S1P) is a membrane sphingolipid involved in several physiological processes, including cell proliferation, tissue growth, cell survival and migration, inflammation, vasculogenesis, and angiogenesis. Herein, we review the most critical effects of S1P on ovarian function, including its physiological and pathophysiological effects. Based on the available evidence, S1P plays an important role in ovarian physiology, participating as an essential stimulator of follicular development in both the preantral and antral phases, as well as in ovulation and corpus luteum development. Moreover, S1P may be a good cytoprotective agent against cancer treatment side-effects (chemotherapy with or without radiation therapy). In the future, this compound may be given for fertility preservation to women undergoing cancer treatment. However, further studies are required to confirm its efficacy in ovarian protection and also its safety in terms of cancer prognosis, given the biological action of the compound. Under- or over-production of S1P may be related to ovarian pathologies.

HIV-1 drug resistance before initiation or re-initiation of first-line ART in eight regions of Mexico: a sub-nationally representative survey.

BACKGROUND: HIV pretreatment drug resistance (PDR) to NNRTIs in persons initiating ART is increasing in Mexico. OBJECTIVES: To compare HIV PDR in eight sub-regions of Mexico. PATIENTS AND METHODS: A large PDR survey was implemented in Mexico (September 2017-March 2018) across eight sub-regions. All larger clinics (which provide ART to 90% of all initiators) were included, allocating sample size using the probability-proportional-to-size method. Both antiretroviral-naive and prior antiretroviral-exposed persons were included. HIV PDR levels were estimated from pol Sanger sequences obtained at a WHO-designated laboratory. RESULTS: A total of 2006 participants were enrolled from 74 clinics. PDR to NNRTIs was higher than to other drug classes (P < 0.0001), crossing the 10% threshold in the North-East, East, South-West and South-East. NNRTI PDR was higher in the South-West (P = 0.02), coinciding with the highest proportion of restarters in this sub-region (14%). We observed higher PDR prevalence to any drug in women compared with men (16.5% versus 12.2%, P = 0.04). After multivariable adjustment, higher NNRTI PDR remained significantly associated with previous antiretroviral exposure in the Centre-North, North-West, South-West and South-East [adjusted OR (aOR): 21, 5, 8 and 25, respectively; P < 0.05]. Genetic network analyses showed high assortativity by sub-region (P < 0.0001), with evidence of drug resistance mutation transmission within local clusters. CONCLUSIONS: Diversification of the public health response to HIV drug resistance based on sub-regional characteristics could be considered in Mexico. Higher NNRTI PDR levels were associated with poorer regions, suggesting opportunities to strengthen local HIV programmes. Price and licensing negotiations of drug regimens containing integrase inhibitors are warranted.

Co-ordinated expression of the VEGF system components in granulosa cells to develop a proangiogenic autocrine milieu during ovarian follicle development.

In the present study, we investigated the temporal relationship between angiogenic and antiangiogenic vascular endothelial growth factor isoforms (VEGFxxxa and VEGFxxxb, respectively), the receptors VEGFR1 and VEGFR2, their soluble forms, and the kinases and the splicing factors regulating the synthesis of VEGF isoforms in healthy and atretic antral follicles. The results show a higher (p < 0.05) messenger RNA (mRNA) expression of VEGF120a, VEGF164a, and VEGF120b in healthy than in atretic follicles, but the mRNA expression of VEGF164b was not detected. The mRNA of serine-arginine protein kinase 1 ( SRPK1) was higher ( p < 0.05) in large healthy follicles than in large atretic follicles. In contrast, atretic follicles had higher mRNA expression of a soluble form of the receptor 2 of VEGF ( sVEGFR2) than healthy follicles ( p < 0.05). Additionally, we observed a positive relationship ( p < 0.05) between SRPK1 and serine-arginine-rich splicing factor 1 ( SRSF1) with the angiogenic isoforms VEGF120a and VEGF164a and between CDC-like kinases-1 ( CLK1) and SRSF6 with the antiangiogenic VEGF120b isoform. Principal components analysis (PCA) resulted in two PC explaining 71% of the variation, which was formed by the VEGF isoforms, the kinases and the splicing factor (PC1) and by the VEGF receptors (PC2). When PC analysis was carried out within follicular health status, there were no differences for PC1 between follicular status, whereas PC2 differed between healthy and atretic follicles. In conclusion, the higher mRNA expression for VEGF120a and VEGF164a, the low expression of sVEGFR2, and absent expression of mRNA for VEGF164b provide evidence of a proangiogenic autocrine milieu to support granulosa cells during follicle development.

Serological study of influenza viruses in veterinarians working with swine in Mexico.

Humans and swine are both affected by influenza viruses, and swine are considered a potential source of new influenza viruses. Transmission of influenza viruses across species is well documented. The aim of this study was to evaluate the seroprevalence of different influenza virus subtypes in veterinarians working for the Mexican swine industry, using a hemagglutination inhibition test. All sera tested were collected in July 2011. The data were analysed using a generalized linear model and a linear model to study the possible association of seroprevalence with the age of the veterinarian, vaccination status, and biosecurity level of the farm where they work. The observed seroprevalence was 12.3%, 76.5%, 46.9%, and 11.1% for the human subtypes of pandemic influenza virus (pH1N1), seasonal human influenza virus (hH1N1), the swine subtypes of classical swine influenza virus (swH1N1), and triple-reassortant swine influenza virus (swH3N2), respectively. Statistical analysis indicated that age was associated with hH1N1 seroprevalence (P < 0.05). Similarly, age and vaccination were associated with pH1N1 seroprevalence (P < 0.05). On the other hand, none of the studied factors were associated with swH1N1 and swH3N2 seroprevalence. All of the pH1N1-positive sera were from vaccinated veterinarians, whereas all of those not vaccinated tested negative for this subtype. Our findings suggest that, between the onset of the 2009 pandemic and July 2011, the Mexican veterinarians working in the swine industry did not have immunity to the pH1N1 virus; hence, they would have been at risk for infection with this virus if this subtype had been circulating in swine in Mexico prior to 2011.

Characterization of nanostructured ZnO thin films deposited through vacuum evaporation.

This work presents a novel technique to deposit ZnO thin films through a metal vacuum evaporation technique using colloidal nanoparticles (average size of 30 nm), which were synthesized by our research group, as source. These thin films had a thickness between 45 and 123 nm as measured by profilometry. XRD patterns of the deposited thin films were obtained. According to the HRSEM micrographs worm-shaped nanostructures are observed in samples annealed at 600 °C and this characteristic disappears as the annealing temperature increases. The films obtained were annealed from 25 to 1000 °C, showing a gradual increase in transmittance spectra up to 85%. The optical band gaps obtained for these films are about 3.22 eV. The PL measurement shows an emission in the red and in the violet region and there is a correlation with the annealing process.

Genetic improvement of Pacific white shrimp [Penaeus (Litopenaeus) vannamei]: perspectives for genomic selection.

The uses of breeding programs for the Pacific white shrimp [Penaeus (Litopenaeus) vannamei] based on mixed linear models with pedigreed data are described. The application of these classic breeding methods yielded continuous progress of great value to increase the profitability of the shrimp industry in several countries. Recent advances in such areas as genomics in shrimp will allow for the development of new breeding programs in the near future that will increase genetic progress. In particular, these novel techniques may help increase disease resistance to specific emerging diseases, which is today a very important component of shrimp breeding programs. Thanks to increased selection accuracy, simulated genetic advance using genomic selection for survival to a disease challenge was up to 2.6 times that of phenotypic sib selection.

Decline of genetic variability in a captive population of Pacific white shrimp Penaeus (Litopenaeus) vannamei using microsatellite and pedigree information

Background: The objective of this study was to estimate the decline of genetic variability and the changes in effective population size in three shrimp populations. One was a wild population collected at several points in the Mexican Pacific Ocean. The other two populations were different generations (7 and 9) from a captive population selected for growth and survival. Microsatellite markers and pedigree were both used to assess genetic variability and effective population size. Results: Using 26 loci, both captive populations showed a decline in the expected heterozygosity (20%) and allelic diversity indices (48 to 91%) compared to the wild population (P < 0.05). The studied captive populations did not differ significantly from each other regarding their expected heterozygosity or allelic diversity indices (P > 0.05). Effective population size estimates based on microsatellites declined from 48.2 to 64.0% in cultured populations (P < 0.05) compared to the wild population. Conclusions: An important decline of genetic variability in the cultured selected population due to domestication, and evidence of a further smaller decline in effective population size across generations in the selected population were observed when analyzing pedigree (41%) and microsatellite data (37%). Pedigree keeping is required to prevent the decline of effective population size and maintain genetic variability in shrimp breeding programs, while microsatellites are useful to assess effective population size changes at the population level.

Retrospective serological survey of influenza viruses in backyard pigs from Mexico City.

BACKGROUND: In the present study, we analyzed the presence of antibodies to four different influenza viruses (pH1N1, hH1N1, swH1N1, and swH3N2) in the sera of 2094 backyard pigs from Mexico City. The sera were obtained between 2000 and 2009. OBJECTIVES: The aim of this study was to perform a retrospective analysis of the 2000-2009 period to determine the seroprevalence of antibodies against pH1N1, hH1N1, swH1N1, and swH3N2 viruses in sera obtained from backyard pigs in Mexico City. METHODS: Antibody detection was conducted with hemagglutination inhibition assay (HI) using four influenza viruses. We used linear regression to analyze the tendency of antibody serum titers throughout the aforementioned span. RESULTS: We observed that the antibody titers for the pH1N1, swH1N1, and swH3N2 viruses tended to diminish over the study period, whereas the antibodies to hH1N1 remained at low prevalence for the duration of the years analyzed in this study. A non-significant correlation (P > 0.05) between antibody titers for pH1N1 and swH1N1 viruses was observed (0.04). It contrasts with the significance of the correlation (0.43) observed between the swH1N1 and swH3N2 viruses (P < 0.01). CONCLUSIONS: Our findings showed no cross-antigenicity in the antibody response against the same subtype. Antibodies against pH1N1 virus were observed throughout the 10-year study span, implying that annual strains shared some common features with the pH1N1 virus since 2000, which would then be capable of supporting the ongoing presence of these antibodies.

Additive and dominance effects of the α(s1)-casein locus on milk yield and composition traits in dairy goats.

The objective of this study was to evaluate the effects of the CSN1S1 locus polymorphism on 305-d records of milk, fat, protein, lactose and total solids yields, fat, protein, lactose and total solids contents in Mexican dairy goats. A total of 514 lactation records belonging to Alpine (n=60), Saanen (n=105) and Toggenburg (n=74) goats, born from 2003 to 2006 in three herds were used. Discrimination between alleles E, F, N, A* (CSN1S1 A, G, H, I, O1 and O2) and B* (CSN1S1 B1, B2, B3, B4, C and L) were made by amplification of fragments of the gene CSN1S1 and digestion with the restriction endonuclease XmnI. In order to estimate additive and dominance effects, data sets including (1) all genotypes, and (2) only homozygote genotypes, were analysed using linear mixed models. The allele A*, had significant additive effects for protein content (0·21±0·07%; P=0·002) and total solids content (0·66±0·23%; P=0·005) when compared with allele F. An unfavourable additive effect of allele A* on milk yield was found in the Alpine breed (-81·4±40·2; P=0·046) when compared with allele F. Favourable dominance effects were found for some genotypes (P<0·05) for milk yield (A*N and B*N), fat yield (A*N and B*E), protein yield (A*N and B*E), lactose yield (A*N) and total solids yield (A*N). Also, unfavourable dominance effects were found (P<0·05) for protein content (A*B* and A*N) and total solids content (A*B*, A*N, and A*F). Allele A* was the only one with a positive effect for protein content. Significant allele-year interaction effects were also observed. The presence of significant dominance effects, estimated between specific pairs of alleles, challenged the purely additive nature of the genetic effect at the CSN1S1 locus. Implications from use of CSN1S1 effects in goat breeding programmes are presented.

Genetic parameters for growth traits in Mexican Nellore cattle.

The aim of this study was to estimate genetic parameters for growth traits in Mexican Nellore cattle. A univariate animal model was used to estimate (co)variance components and genetic parameters. The traits evaluated were birth weight (BW), weaning weight (WW), and yearling weight (YW). Models used included the fixed effects of contemporary groups (herd, sex, year, and season of birth) and age of dam (linear and quadratic) as a covariate. They also included the animal, dam, and residual as random effects. Phenotypic means (SD) for BW, WW, and YW were 31.4 (1.6), 175 (32), and 333 (70) kg, respectively. Direct heritability, maternal heritability, and the genetic correlation between additive direct and maternal effects were 0.59, 0.17, and -0.90 for BW; 0.29, 0.17, and -0.90 for WW; and 0.24, 0.15, and -0.86 for YW, respectively. The results showed moderate direct and maternal heritabilities for the studied traits. The genetic correlations between direct and maternal effects were negative and high for all the traits indicating important tradeoffs between direct and maternal effects. There are significant possibilities for genetic progress for the growth traits studied if they are included in a breeding program considering these associations.

Covarianzas genéticas y fenotípicas para días abiertos y características de la curva de lactancia en vacas Holstein en el norte de México / Genetic and phenotypic covariances for days open and lactation curve characteristics in Holstein cows from northern Mexico

The aim of this study was to estimate genetic and phenotypic (co)variances for lactation curve traits and for days open in Holstein cows. Data included 1 579 lactations from 766 cows, daughters of 126 sires in a dairy herd in northern Mexico. The studied traits within lactation were days open (DO), peak milk production (PMAX), days to peak milk production (DPMAX), 305-day milk production (MP305), lactation persistency (based on Wood equation) (PERSW), lactation persistency expressed as the natural logarithm of the Wood equation persistency (LNPERSW), and lactation persistency measured as (production at day 305/PMP) x 100 (PERS). Covariance components were obtained by single trait and bivariate mixed linear models using restricted maximum likelihood. In general, heritabilities estimated using the repeatability model yielded lower values than those obtained based on within lactation analysis. Average heritabilities estimated with single trait models within lactation were 0.13 ± 0.09, 0.28 ± 0.09, 0.28 ± 0.09, 0.17 ± 0.10 and 0.22 ± 0.10, for DO, MP305, PMAX, DPMAX, and LNPERSW, respectively. Genetic correlations between MP305 and DO (0.66±0.57) and between PMAX and DO (0.55 ± 0.71) were unfavorable for first lactation cows, but with large standard errors. Results confirmed a low heritability for DO, but with estimates possibly larger in younger cows. Genetic correlation between MP305 and PMAX was 0.89 ± 0.09, and LNPERSW and DPMAX was 0.98 ± 0.21 for the third lactation, indicating that DPMAX is a good measure of persistency. No evidence for genetic correlation between MP305 and LNPERSW was found.

El objetivo de este estudio fue estimar covarianzas genéticas y fenotípicas para características de la curva de lactancia y días abiertos en vacas Holstein. Los datos incluyeron 1 579 lactancias de 766 vacas, hijas de 126 sementales, en un hato en el norte de México. Las características estudiadas por lactancia fueron días abiertos (DO), producción máxima de leche (PMÁX), días a la producción máxima (DPMÁX), producción de leche de 305 días (MP305), persistencia de la lactancia por Wood (PERSW), persistencia de Wood expresada como logaritmo natural (LNPERSW) y persistencia medida como ((producción al día 305/PMÁX) x 100) (PERS). Los componentes de covarianza fueron obtenidos mediante el uso de modelos univariados y bivariados con máxima verosimilitud restringida. Las heredabilidades estimadas para las características con el modelo de repetibilidad tuvieron valores generalmente inferiores a los estimados con los análisis dentro de lactancia. Las heredabilidades promedio estimadas con modelos univariados dentro de lactancia para DO, MP305, PMÁX, DPMÁX y LNPERSW fueron 0.13 ± 0.09, 0.28 ± 0.09, 0.28 ± 0.09, 0.17 ± 0.10 y 0.22 ± 0.10, respectivamente. Las correlaciones genéticas entre MP305 y DO (0.66±0.57) y entre PMÁX y DO (0.55 ± 0.71) fueron desfavorables para las primeras lactancias, pero con errores estándar elevados. Los resultados confirman una heredabilidad baja para DO, pero con valores posiblemente mayores en vacas jóvenes. La correlación genética entre MP305 y PMÁX fue de 0.89 ± 0.09 y entre LNPERSW y DPMÁX fue 0.98 ± 0.21 para la tercera lactancia, lo que indica que DPMÁX es buen estimador de la persistencia. No se encontró evidencia de correlación genética entre MP305 y LNPERSW.

Efectos de interacción genotipo por ambiente para peso corporal a los 130 días en camarón blanco del Pacífico [Penaeus (Litopenaeus) vannamei] / Genotype by environment interaction effects for body weight at 130 days of age in the Pacific white shrimp [Penaeus (Litopenaeus) vannamei]

Body weight of Pacific white shrimp [Penaeus (Litopenaeus) vannamei] at 130 days of age was analyzed in three environments corresponding to different management systems: semi-intensive (10 shrimp/m²) in Pozos, Sinaloa (POZOS10), intensive (30 shrimp/ m²) in Pozos, Sinaloa (POZOS30), and super-intensive (85 shrimp/m²) in Bahia de Kino, Sonora (KINO85). Data were obtained from 18 087 sibs from 113 sires and 143 dams. The aim of the study was to evaluate the presence of genotype by environment interaction effects (IGA) and the effect of the (co) variance between full-sibs family common effects on the genetic parameter estimates. Estimates of h² with a model including independent full-sibs family common effects were between 0.26 and 0.39 across environments, while the estimates for a model with correlated full-sibs family common effects were estimated between 0.14 and 0.23. No differences were found for h² values between environments. The genetic correlations between environments were not lower from unity with any model; therefore, it is concluded that no evidence of genotype-environment interaction exists for body weight at 130 days in Pacific white shrimp, under the environments used in this study. The inclusion of the (co)variance between full-sibs family common effects of different environments affected the parameter estimates. These results also indicate that ranking of the breeding animals will be similar in all the studied production environments.

Se analizó información de peso corporal de camarón blanco del Pacífico [Penaeus (Litopenaeus) vannamei] a los 130 días, en tres sistemas de manejo: semiintensivo (10 camarones/m²); intensivo (30 camarones/m²), ambos en Pozos, Sinaloa, y super-intensivo (85 camarones/m²), en Bahía de Kino, Sonora. Los registros corresponden a 18 087 individuos, hijos de 113 sementales y 143 hembras, con la finalidad de evaluar la existencia de interacciones genotipo por ambiente (IGA) y el efecto de la covarianza de los efectos comunes de familia de hermanos en la estimación de parámetros genéticos. Las estimaciones de h² con un modelo que consideró los efectos comunes de familia de hermanos como independientes, fueron de 0.26 a 0.39 y de 0.14 a 0.23, para un modelo que consideró dichos efectos como correlacionados. No existió diferencia significativa entre los valores de h² de los ambientes, y las correlaciones genéticas entre ambientes no fueron menores a uno con ninguno de ambos modelos, se concluye que no hay evidencia de IGA en el peso corporal a los 130 días de P. vannamei en los ambientes estudiados en este trabajo. La inclusión de la covarianza entre efectos de familias de hermanos en el análisis afectó los valores de los parámetros. Se concluye que el ordenamiento de los reproductores será similar en los ambientes estudiados.

Retrospective serological survey of Porcine circovirus-2 infection in Mexico.

Postweaning multisystemic wasting syndrome (PMWS) is considered a multifactorial emerging disease of which Porcine circovirus-2 (PCV-2) is the necessary infectious cause. However, retrospective studies have shown that PMWS is not a new disease and that PCV-2 has been circulating in pig farms for years. Most of these studies were performed in Europe and Asia; only a few were performed in North or South America. A PCV-2 retrospective serological survey was carried out with 659 serum samples collected from pigs in Mexico between 1972 and 2000. Serological analyses were performed with an immunoperoxidase monolayer assay (IPMA). The overall prevalence of PCV-2 antibodies was 59% (387/659); the prevalence was 27% (24/90) for the period from 1972-1979; 44% (74/169) from 1980-1989, and 72% (289/400) from 1990-2000. Antibodies to PCV-2 were detected in at least 1 pig from all tested years since 1973. This study shows evidence of enzootic PCV-2 infection in Mexico for many years before the first description of PMWS in the country (in 2001), further supporting results obtained in other parts of the world. To date, this study provides the earliest evidence of PCV-2 infection in the North and South American continents.