Building Programs to Eradicate Toxoplasmosis Part III: Epidemiology and Risk Factors

Purpose of Review

Review comprehensive data on rates of toxoplasmosis in Panama and Colombia.

Recent Findings

Samples and data sets from Panama and Colombia, that facilitated estimates regarding seroprevalence of antibodies to Toxoplasma and risk factors, were reviewed.

Summary

Screening maps, seroprevalence maps, and risk factor mathematical models were devised based on these data. Studies in Ciudad de Panamá estimated seroprevalence at between 22 and 44%. Consistent relationships were found between higher prevalence rates and factors such as poverty and proximity to water sources. Prenatal screening rates for anti-Toxoplasma antibodies were variable, despite existence of a screening law. Heat maps showed a correlation between proximity to bodies of water and overall Toxoplasma seroprevalence. Spatial epidemiological maps and mathematical models identify specific regions that could most benefit from comprehensive, preventive healthcare campaigns related to congenital toxoplasmosis and Toxoplasma infection.

Building Programs to Eradicate Toxoplasmosis Part II: Education

Purpose of Review

Review work to create and evaluate educational materials that could serve as a primary prevention strategy to help both providers and patients in Panama, Colombia, and the USA reduce disease burden of Toxoplasma infections.

Recent Findings

Educational programs had not been evaluated for efficacy in Panama, USA, or Colombia.

Summary

Educational programs for high school students, pregnant women, medical students and professionals, scientists, and lay personnel were created. In most settings, short-term effects were evaluated. In Panama, Colombia, and USA, all materials showed short-term utility in transmitting information to learners. These educational materials can serve as a component of larger public health programs to lower disease burden from congenital toxoplasmosis. Future priorities include conducting robust longitudinal studies of whether education correlates with reduced adverse disease outcomes, modifying educational materials as new information regarding region-specific risk factors is discovered, and ensuring materials are widely accessible.

Estimating Bordetella pertussis seroprevalence in adolescents and young adults in Mexico using the 2012 National Health and Nutrition Survey (ENSANUT)

BACKGROUND

Low vaccination rates and under-detection of pertussis infections in adolescents and young adults have an impact on the transmission of pertussis to infants. In this study, the proportion of adolescents and young adults with IgG antibodies against B. pertussis antigens, representing recent infection or vaccination, was estimated in a population-based probabilistic survey in Mexico.

METHODS

Sera and data from 1,581 subjects, including 1,102 adolescents and 479 young adults (10-19 and 20-25 years old, respectively) randomly selected from Mexico's 2012 National Health and Nutrition Survey, were analyzed. IgG antibodies against pertussis toxin (PT) were measured with the CDC/FDA ELISA. A subset of 234 samples was additionally tested with Bp-IgG PT ELISA kit (EUROIMMUN AG, Lubeck, Germany). Threshold values from corresponding test kits were used to identify recent infection or vaccination.

RESULTS

Overall anti-PT IgG seroprevalence was 3.9% (95% CI: 2.3-6.3); 3.1% (95% CI: 1.9-5.0) in adolescents, and 4.9% (95% CI: 2.2-11) in young adults. Seroprevalence did not significantly vary by sex, socioeconomic status, region or rural/urban location. Compared to the CDC/FDA ELISA, the EUROIMMUN test showed a 76% sensitivity and 88% specificity. The weighted estimates represent a considerable burden of recent infection in adolescents and young adults; however, most adolescents and adults were seronegative and, therefore, susceptible to pertussis infection.

CONCLUSION

Since booster vaccination to B. pertussis after toddlerhood is not recommended in the Mexican national policy, anti-PT IgG seropositivity may be reasonably attributed to recent infection. Assessing pertussis seroprevalence requires careful consideration of the diagnostic test threshold interpretation and epidemiological model used.

15-year experience with rotavirus vaccination in Mexico: a systematic literature review

A systematic review was conducted in Mexico to consolidate and evaluate evidence after 15 years of rotavirus vaccination, according to the National Immunization Program. Five databases were screened to identify published articles (January 2000-February 2020) with evidence on all clinical and epidemiological endpoints (e.g. immunogenicity, safety, efficacy, impact/effectiveness) of rotavirus vaccination in Mexico. Twenty-two articles were identified (observational studies including health-economic models: 17; randomized controlled trials: 5). Fourteen studies evaluated a human attenuated vaccine (HRV), four studies evaluated both vaccines, and only two evaluated a bovine-human reassortant vaccine, with local efficacy data only for HRV. Local evidence shows vaccines are safe, immunogenic, efficacious, and provide an acceptable risk-benefit profile. The benefits of both vaccines in alleviating the burden of all-cause diarrhea mortality and morbidity are documented in several local post-licensure studies. Findings signify overall benefits of rotavirus vaccination and support the continued use of rotavirus vaccine in Mexico.

Performance of a Point of Care Test for Detecting IgM and IgG Antibodies Against SARS-CoV-2 and Seroprevalence in Blood Donors and Health Care Workers in Panama

Novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic, which has reached 28 million cases worldwide in 1 year. The serological detection of antibodies against the virus will play a pivotal role in complementing molecular tests to improve diagnostic accuracy, contact tracing, vaccine efficacy testing, and seroprevalence surveillance. Here, we aimed first to evaluate a lateral flow assay's ability to identify specific IgM and IgG antibodies against SARS-CoV-2 and second, to report the seroprevalence estimates of these antibodies among health care workers and healthy volunteer blood donors in Panama. We recruited study participants between April 30th and July 7th, 2020. For the test validation and performance evaluation, we analyzed serum samples from participants with clinical symptoms and confirmed positive RT-PCR for SARS-CoV-2, and a set of pre-pandemic serum samples. We used two by two table analysis to determine the test positive and negative percentage agreement as well as the Kappa agreement value with a 95% confidence interval. Then, we used the lateral flow assay to determine seroprevalence among serum samples from COVID-19 patients, potentially exposed health care workers, and healthy volunteer donors. Our results show this assay reached a positive percent agreement of 97.2% (95% CI 84.2-100.0%) for detecting both IgM and IgG. The assay showed a Kappa of 0.898 (95%CI 0.811-0.985) and 0.918 (95% CI 0.839-0.997) for IgM and IgG, respectively. The evaluation of serum samples from hospitalized COVID-19 patients indicates a correlation between test sensitivity and the number of days since symptom onset; the highest positive percent agreement [87% (95% CI 67.0-96.3%)] was observed at ≥15 days post-symptom onset (PSO). We found an overall antibody seroprevalence of 11.6% (95% CI 8.5-15.8%) among both health care workers and healthy blood donors. Our findings suggest this lateral flow assay could contribute significantly to implementing seroprevalence testing in locations with active community transmission of SARS-CoV-2.

Can two different pneumococcal conjugate vaccines be used to complete the infant vaccination series? A randomized trial exploring interchangeability of the 13-valent pneumococcal conjugate vaccine and the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine

Background: We assessed the safety and immunogenicity of 2 + 1 infant regimens initiated with the 13-valent pneumococcal conjugate vaccine (PCV13) and completed with the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV). Methods: This partially blinded study randomized 6-12-week-old infants to receive two-dose priming and a booster (at ages 2, 4, 12-15 months) with: PCV13 at priming and PHiD-CV at boosting (PPS); PCV13 then PHiD-CV at priming and PHiD-CV at boosting (PSS); or PHiD-CV at priming and boosting (SSS control). All analyses were descriptive, i.e., no statistical significance tests were done. Results: The total vaccinated cohort at priming comprised 294 infants. Grade 3 adverse events were reported after 8.7% (PPS), 11.4% (PSS), and 16.9% (SSS) of primary doses (primary objective). No serious adverse events were considered vaccination-related. For most PHiD-CV serotypes, observed percentages of children reaching antibody concentrations ≥0.2 µg/mL and opsonophagocytic activity (OPA) titers above cutoffs were similar across groups 1 month post-priming and post-booster. Observed geometric mean antibody concentrations and OPA titers were lower for some PHiD-CV serotypes with the mixed regimens than with PHiD-CV only, especially for PSS. However, no tests of statistical significance were performed. Conclusions: Immunogenicity of the two mixed PCV13/PHiD-CV regimens seemed mostly similar to that of a PHiD-CV-only series, although observed antibody GMCs and OPA GMTs for some PHiD-CV serotypes were lower. No safety concerns were raised. The clinical relevance of the observed differences is unknown. Clinical trial registration: ClinicalTrials.gov: NCT01641133.

Highlights of an Expert Advisory Board on Acute Exacerbations of Chronic Obstructive Pulmonary Disease (AE-COPD) in Latin America

Background

Chronic obstructive pulmonary disease (COPD) is a preventable and usually progressive lung disease that affects millions of people worldwide and is the sixth leading cause of death in the Americas. Viral and bacterial respiratory tract infections and air pollution may cause acute exacerbations of COPD (AE-COPD) ranging from mild, moderate to severe. The greatest proportion of the overall COPD burden on the health system is due to disease exacerbations. There is limited evidence regarding the etiology and burden of AE-COPD in Latin America (LATAM).

Methods

To respond to this gap in evidence, an Advisory Board with regional pneumologists and infectious disease experts was convened in September 2018 in Panama City, Panama, to: 1) review the burden of AE-COPD in LATAM; 2) evaluate the etiology of AE-COPD in LATAM; and 3) assess and compare the local/regional guidelines to confirm the etiology, characterize, and manage AE-COPD.

Results

The results of the meeting showed that there is a high prevalence of AE-COPD in LATAM countries, limited evidence on etiology data, and discrepancies in the case definitions and symptomology (ie, severity) classifications used in LATAM.

Conclusion

The Advisory Board discussions further resulted in recommendations for future research on the impact on the epidemiology and burden of disease, on establishing standardized AE-COPD case definition guidelines, and on studying the etiology of both moderate and severe AE-COPD cases.

COVID-19 pandemic in Panama: lessons of the unique risks and research opportunities for Latin America

The Republic of Panama has the second most unequally distributed wealth in Central America, has recently entered the list of countries affected by the COVID-19 pandemic, and has one of the largest testing rate per inhabitant in the region and consequently the highest incidence rate of COVID-19, making it an ideal location to discuss potential scenarios for assessing epidemic preparedness, and to outline research opportunities in the Region of the Americas. We address two timely important questions: What are the unique risks of COVID-19 in Panama that could help other countries in the Region be better prepared? And what kind of scientific knowledge can Panama contribute to the regional and global study of COVID-19? This paper provides suggestions about how the research community could support local health authorities plan for different scenarios and decrease public anxiety. It also presents basic scientific opportunities about emerging pandemic pathogens towards promoting global health from the perspective of a middle income country.

Vaccination herd effect experience in Latin America: a systematic literature review

Background: National pediatric vaccination programs have been introduced in Latin America (LatAm) to reduce the burden of diseases due to pathogens such as rotavirus, Haemophilus influenzae type b (Hib) and pneumococcus. Vaccination health benefits may extend to unvaccinated populations by reducing pathogen transmission. Understanding herd effect is important for implementation and assessment of vaccination programs. The objective was to conduct a systematic review of published epidemiological evidence of herd effect with Hib, rotavirus and pneumococcal conjugate vaccines (PCV) in LatAm.

Methods: Searches were conducted in PubMed, Virtual Health Library (VHL), SciELO and SCOPUS databases, for studies reporting data on herd effect from Hib, rotavirus and PCV vaccination in LatAm, without age restriction. Searches were limited to articles published in English, Spanish or Portuguese (1990–2016). After screening and full-text review, articles meeting the selection criteria were included to be critically appraised following criteria for observational and interventional studies. The presence of a herd effect was defined as a significant decrease in incidence of disease, hospitalization, or mortality.

Results: 3,465 unique articles were identified, and 23 were included (Hib vaccine n = 5, PCV n = 8, rotavirus vaccine n = 10). Most studies included children and/or adolescents (age range varied between studies). Studies in adults, including older adults (aged > 65 years), were limited. Few studies reported statistically significant reductions in disease incidence in age groups not targeted for vaccination. Hib-confirmed meningitis hospitalization decreased in children but herd effect could not be quantified. Some evidence of herd effect was identified for PCV and rotavirus vaccine in unvaccinated children. Evidence for herd effects due to PCV in adults was limited.

Conclusion: After introduction of Hib, PCV and rotavirus vaccination in LatAm, reductions in morbidity/mortality have been reported in children not targeted for vaccination. However, due to methodological limitations (e.g. short post-vaccination periods and age range studied), there is currently insufficient evidence to quantify the herd effect in adult populations. More research and higher quality surveillance is needed to characterize herd effect of these vaccines in LatAm.

Pneumococcal meningitis trends after pneumococcal conjugate vaccine introduction in Colombia: An interrupted time-series analysis

Colombia introduced mass pneumococcal conjugate vaccination at the end of 2011. Using 2005-2015 surveillance data, we conducted a retrospective interrupted time-series analysis. A significant trend towards reduced monthly was observed in the post-vaccination period (2012-2015) compared with the expected rate, reaching in 2015 a reduction of 90.5% of pneumococcal meningitis. This trend was not observed for control diseases.

A cross-sectional study assessing the pharyngeal carriage of Neisseria meningitidis in subjects aged 1-24 years in the city of Embu das Artes, São Paulo, Brazil

Meningococcal carriage is a prerequisite for invasive infection. This cross-sectional study assessed the pharyngeal carriage prevalence in healthy subjects aged 1-24 years in Embu das Artes city, São Paulo, Brazil. Pharyngeal swabs were examined for the presence of Neisseria meningitidis. The isolates were tested for different serogroups using agglutination and polymerase chain reaction. A logistic regression model assessed any independent association between Neisseria meningitidis carriage and various risk factors. A total of 87/967 subjects (9%, 95% Confidence Interval (CI): 7.3-11.0) tested positive for N. meningitidis: 6.2% (95% CI: 3.8-9.4) in 1-4 years, 8.5% (95% CI: 5.1-13.0) in 5-9 years, 12.5% (95% CI: 7.8-18.6) in 10-14 years, 12.6% (95% CI: 7.4-19.7) in 15-19 years and 9% (95% CI: 4.9-14.9) in 20-24 years age groups. Highest carriage prevalence was observed in adolescents 10-19 years old. Serogroup C was predominant (18.4%) followed by serogroup B (12.6%). The 15-19 years age group showed a significant association between number of household members and carriers of N. meningitidis. This cross-sectional study is the first in Brazil to evaluate meningococcal carriage prevalence and associated factors in a wide age range.

Etiology of acute otitis media and serotype distribution of Streptococcus pneumoniae and Haemophilus influenzae in Chilean children <5 years of age

The impact of bacterial conjugate vaccines on acute otitis media (AOM) is affected by several factors including population characteristics, bacterial etiology and vaccine conjugation method, carrier, and coverage. This study estimated the baseline etiology, distribution, and antibiotic susceptibility of bacterial serotypes that causes AOM in children aged <5 years in a public setting in Santiago, Chile.Children aged ≥3 months and <5 years referred to the physician for treatment of AOM episodes (with an onset of symptoms <72 h) were enrolled between September 2009 and September 2010. Middle ear fluid (MEF) was collected by tympanocentesis or by otorrhea for identification and serotyping of bacteria. Antibacterial susceptibility was tested using E-test (etrack: 112671).Of 160 children (mean age 27.10 ± 15.83 months) with AOM episodes, 164 MEF samples (1 episode each from 156 children; 2 episodes each from 4 children) were collected. Nearly 30% of AOM episodes occurred in children aged 12 to 23 months. Streptococcus pneumoniae (41.7% [58/139]) and Haemophilus influenzae (40.3% [56/139]) were predominant among the cultures that showed bacterial growth (85% [139/164]). All Streptococcus pneumoniae positive episodes were serotyped, 19F (21%) and 14 (17%) were the predominant serotypes; all Haemophilus influenzae strains were nontypeable. Streptococcus pneumoniae were resistant to penicillin (5%) and erythromycin (33%); Haemophilus influenzae were resistant to ampicillin (14%) and cefuroxime and cefotaxime (2% each).AOM in Chilean children is predominantly caused by Streptococcus pneumoniae and nontypeable Haemophilus influenzae. Use of a broad spectrum vaccine against these pathogens might aid the reduction of AOM in Chile.

Efficacy, safety and effectiveness of licensed rotavirus vaccines: a systematic review and meta-analysis for Latin America and the Caribbean

BACKGROUND

RotaTeq™ (RV5; Merck & Co. Inc., USA) and Rotarix™ (RV1, GlaxoSmithKline, Belgium) vaccines, developed to prevent rotavirus diarrhea in children under five years old, were both introduced into national immunization programs in 2006. As many countries in Latin America and the Caribbean have included either RV5 or RV1 in their routine childhood vaccination programs, we conducted a systematic review and meta-analysis to analyze efficacy, safety and effectiveness data from the region.

METHODS

We conducted a systematic search in PubMed, EMBASE, Scielo, Lilacs and the Cochrane Central Register, for controlled efficacy, safety and effectiveness studies published between January 2000 until December 2011, on RV5 and RV1 across Latin America (where both vaccines are available since 2006). The primary outcome measures were: rotavirus-related gastroenteritis of any severity; rotavirus emergency department visits and hospitalization; and severe adverse events.

RESULTS

The results of the meta-analysis for efficacy show that RV1 reduced the risk of any-severity rotavirus-related gastroenteritis by 65% (relative risk (RR) 0.35, 95% confidence interval (CI) 0.25; 0.50), and of severe gastroenteritis by 82% (RR 0.18, 95%CI 0.12; 0.26) versus placebo. In trials, both vaccines significantly reduced the risk of hospitalization and emergency visits by 85% (RR 0.15, 95%CI 0.09; 0.25) for RV1 and by 90% (RR 0.099, 95%CI 0.012; 0.77) for RV5. Vaccination with RV5 or RV1 did not increase the risk of death, intussusception, or other severe adverse events which were previously associated with the first licensed rotavirus vaccine. Real-world effectiveness studies showed that both vaccines reduced rotavirus hospitalization in the region by around 45-50% for RV5 (for 1 to 3 doses, respectively), and, by around 50-80% for RV1 (for 1 to 2 doses, respectively). For RV1, effectiveness against hospitalization was highest (around 80-96%) for children vaccinated before 12 months of age, compared with 5-60% effectiveness in older children. Both vaccines were most effective in preventing more severe gastroenteritis (70% for RV5 and 80-90% for RV1) and severe gastroenteritis (50% for RV5 and 70-80% for RV1).

CONCLUSION

This systematic literature review confirms rotavirus vaccination has been proven effective and well tolerated in protecting children in Latin America and the Caribbean.

Impact of Hepatitis A vaccination with a two-dose schedule in Panama: Results of epidemiological surveillance and time trend analysis

PURPOSE

In April 2007, Panama introduced Hepatitis A universal vaccination using a two-dose schedule (Havrix(®)junior; GSK Vaccines, Belgium). We assessed the impact of this hepatitis A vaccine three years after it was recommended for universal mass vaccination in Panama.

MATERIALS AND METHODS

Hepatitis A vaccination impact was assessed using two different approaches. The first approach used retrospective data (incidence and number of cases for all age groups), collected from the passive surveillance of the Epidemiologic Surveillance System of the Ministry of Health of hepatitis A and unspecified hepatitis before (2000-2006) and after (2008-2010) introduction of hepatitis A vaccine. The second approach was a prospective hospital-based active surveillance for hepatitis cases conducted in subjects (0-14 years) during 2009-2011 at three sentinel hospitals in Panama.

RESULTS

Overall, the annual incidence of hepatitis A and unspecified hepatitis in 2008, 2009 and 2010 were 13.1, 7.9 and 3.7 per 100,000 subjects, lower than the baseline incidence of 51.1 per 100,000 subjects. In comparison to the mean baseline period (2000-2006), there was an 82% mean reduction in the overall hepatitis-related outcomes (hepatitis A and unspecified hepatitis) after vaccine introduction (2008-2010) in all age groups. In the hospital-based surveillance (2009-2011), of the 42 probable viral hepatitis A cases, nine cases were confirmed as acute hepatitis A (8 in 2009, 1 in 2010). Of these confirmed cases, two belonged to the targeted vaccine group (1-4 years) but were not vaccinated.

CONCLUSIONS

Our study suggests that the introduction of two-dose hepatitis A vaccines in Panama has contributed to the reduction in the incidence of overall hepatitis-related outcomes for all age groups, suggesting herd protection. Additional monitoring is required to document a sustained long-term effect.

Etiology and antimicrobial susceptibility of middle ear fluid pathogens in Costa Rican children with otitis media before and after the introduction of the 7-valent pneumococcal conjugate vaccine in the National Immunization Program: acute otitis media microbiology in Costa Rican children

Acute otitis media (AOM) microbiology was evaluated in children after 7-valent pneumococcal conjugate vaccine (PCV7) introduction in Costa Rica (private sector, 2004; National Immunization Program, 2009). This was a combined prospective and retrospective study conducted in a routine clinical setting in San José, Costa Rica. In the prospective part of the study, which was conducted post-PCV7 introduction (2010-2012), standard bacteriological procedures were used to evaluate the etiology and serotype distribution of middle ear fluid samples collected by tympanocentesis or otorrhea from children aged 3-59 months diagnosed with AOM. E-tests were used to evaluate antimicrobial susceptibility in culture-positive samples. Retrospective data recorded between 1999 and 2004 were used for comparison of bacterial etiology and serotype distribution before and after PCV7 introduction. Statistical significance was evaluated in bivariate analyses at the P-value < 0.05 level (without multiplicity correction). Post-PCV7 introduction, Haemophilus influenzae was detected in 118/456 and Streptococcus pneumoniae in 87/456 AOM episodes. Most H. influenzae isolates (113/118) were non-typeable. H. influenzae was more (27.4% vs 20.8%) and S. pneumoniae less (17.1% vs 25.5%) frequently observed in vaccinated (≥ 2 PCV7 doses or ≥ 1 PCV7 dose at >1 year of age) versus unvaccinated children. S. pneumoniae non-susceptibility rates were 1.1%, 34.5%, 31.7%, and 50.6% for penicillin, erythromycin, azithromycin, and trimethoprim/sulfamethoxazole (TMP-SMX), respectively. H. influenzae non-susceptibility rate was 66.9% for TMP-SMX. Between pre- and post-PCV7 introduction, H. influenzae became more (20.5% vs 25.9%; P-value < 0.001) and S. pneumoniae less (27.7% vs 19.1%; P-value = 0.002) prevalent, and PCV7 serotype proportions decreased among pneumococcal isolates (65.8% vs 43.7%; P-value = 0.0005). Frequently identified pneumococcal serotypes were 19F (34.2%), 3 (9.7%), 6B (9.7%), and 14 (9.7%) pre-PCV7 introduction, and 19F (27.6%), 14 (8.0%), and 35B (8.0%) post-PCV7 introduction. Following PCV7 introduction, a change in the distribution of AOM episodes caused by H. influenzae and pneumococcal serotypes included in PCV7 was observed in Costa Rican children. Pneumococcal vaccines impact should be further evaluated following broader vaccination coverage.

Seroprevalences of varicella-zoster virus, herpes simplex virus and cytomegalovirus in a cross-sectional study in Mexico

We estimated the seroprevalences of varicella-zoster virus (VZV), herpes simplex virus (HSV) and cytomegalovirus (CMV) in this cross-sectional database study. Serum samples collected during the National Health and Nutrition survey (ENSANUT 2006) were obtained from subjects aged 1-70 years between January and October 2010. Serological assays for the determination of antibodies against VZV, HSV and CMV were performed. The overall seroprevalences of VZV, HSV-1, HSV-2 and CMV were 85.8%, 80.9%, 9.9% and 89.2%, respectively. Seroprevalences of VZV, HSV-1 and CMV were comparable between males and females. For HSV-2, although the seroprevalence rate was higher in females when compared to males, this difference in seroprevalence was not statistically significant. Seroprevalence rates for VZV, HSV-1, HSV-2 and CMV increased with age (p-value<.0001). Differences in seroprevalence rate for VZV by socioeconomic status (SES) were significant (p-value<0001). Results of the serological analyses reported high VZV seroprevalence, indicating high transmission in the Mexican population with children and adolescents at risk of acquiring VZV. Global HSV-1 seroprevalence was high, especially in adults. HSV-1 and HSV-2 seroprevalences were consistently higher in women than men, particularly for HSV-2. CMV seroprevalence was higher in Mexico when compared to developed countries. Seroepidemiological data on VZV supports the fact that varicella vaccination may serve as an alternative effective solution to reduce transmission in the Mexican population. For CMV and HSV, since no vaccines are available, activities to reduce transmission are important to reduce the risk of complications and therefore need to be considered.

Seroprevalence of hepatitis A virus in a cross-sectional study in Mexico: Implications for hepatitis A vaccination

Hepatitis A virus (HAV) remains a public health concern worldwide contributing to significant morbidity in developed and developing countries. This cross-sectional database study estimated the overall HAV seroprevalence and the seroprevalence by gender, age, region and socioeconomic status in Mexico. Between January and October 2010, serum samples collected during the National Health and Nutrition survey (ENSANUT 2006) were obtained from subjects aged 1-95 y. Subjects' gender, age, geographical region and socioeconomic status were extracted from the survey and compiled into a subset database by the Mexican National Institute of Public Health. Anti-HAV antibodies were measured using a chemiluminescent immunoassay. A total of 3658 subjects were included in the according-to-protocol cohort. Overall, the HAV seroprevalence was 84.2%. The HAV seroprevalence rates were similar between females (86.1%) and males (82.2%). The percentage of subjects seropositive for anti-HAV antibodies was highest in adults aged ≥ 20 y (96.9%), followed by adolescents aged 10-19 y (80.1%) and lowest in children aged 1-9 y (45.0%) (p < 0.0001). Regionally, the highest HAV seroprevalence rate was observed in the South (88.8%) followed by Central and Northern Mexico and Mexico City (p = 0.02). The HAV seroprevalence was similar between subjects of high socioeconomic (90.1%) status and of low socioeconomic status (86.6%). This study confirms the intermediate HAV endemicity in Mexico. Cost-effectiveness studies are necessary to evaluate the inclusion of an effective hepatitis A vaccine from a population-based perspective in addition to continuous efforts to improve hygiene and sanitation that have a substantial impact on the disease burden.

Streptococcus pneumoniae serotype 19A in Latin America and the Caribbean: a systematic review and meta-analysis, 1990-2010

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) are in the process of implementation in Latin America. Experience in developed countries has shown that they reduce the incidence of invasive and non-invasive disease. However, there is evidence that the introduction of PCVs in universal mass vaccination programs, combined with inappropriate and extensive use of antibiotics, could be associated to changes in non-PCV serotypes, including serotype 19A. We conducted a systematic review to determine the distribution of serotype 19A, burden of pneumococcal disease and antibiotic resistance in the region.

METHODS

We performed a systematic review of serotype 19A data from observational and randomized clinical studies in the region, conducted between 1990 and 2010, for children under 6 years. Pooled prevalence estimates from surveillance activities with confidence intervals were calculated.

RESULTS

We included 100 studies in 22 countries and extracted data from 63. These data reported 19733 serotyped invasive pneumococcal isolates, 3.8% of which were serotype 19A. Serotype 19A isolates were responsible for 2.4% acute otitis media episodes, and accounted for 4.1% and 4.4% of 4,380 nasopharyngeal isolates from healthy children and in hospital-based/sick children, respectively. This serotype was stable over the twenty years of surveillance in the region. A total of 53.7% Spn19A isolates from meningitis cases and only 14% from non meningitis were resistant to penicillin.

CONCLUSIONS

Before widespread PCV implementation in this region, serotype 19A was responsible for a relatively small number of pneumococcal disease cases. With increased use of PCVs and a greater number of serotypes included, monitoring S. pneumoniae serotype distribution will be essential for understanding the epidemiology of pneumococcal disease.

Non-capsulated and capsulated Haemophilus influenzae in children with acute otitis media in Venezuela: a prospective epidemiological study

Background

Non-typeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae are major causes of bacterial acute otitis media (AOM). Data regarding AOM are limited in Latin America. This is the first active surveillance in a private setting in Venezuela to characterize the bacterial etiology of AOM in children < 5 years of age.

Methods

Between December 2008 and December 2009, 91 AOM episodes (including sporadic, recurrent and treatment failures) were studied in 87 children enrolled into a medical center in Caracas, Venezuela. Middle ear fluid samples were collected either by tympanocentesis or spontaneous otorrhea swab sampling method. Standard laboratory and microbiological techniques were used to identify bacteria and test for antimicrobial resistance. The results were interpreted according to Clinical Laboratory Standards Institute (CLSI) 2009 for non-meningitis isolates. All statistical analyses were performed using SAS 9.1 and Microsoft Excel (for graphical purposes).

Results

Overall, bacteria were cultured from 69.2% (63 of the 91 episodes); at least one pathogen (S. pneumoniae, H. influenzae, S. pyogenes or M. catarrhalis) was cultured from 65.9% (60/91) of episodes. H. influenzae (55.5%; 35/63 episodes) and S. pneumoniae (34.9%; 22/63 episodes) were the most frequently reported bacteria. Among H. influenzae isolates, 62.9% (22/35 episodes) were non-capsulated (NTHi) and 31.4% (11/35 episodes) were capsulated including types d, a, c and f, across all age groups. Low antibiotic resistance for H. influenzae was observed to amoxicillin/ampicillin (5.7%; 2/35 samples). NTHi was isolated in four of the six H. influenzae positive samples (66.7%) from recurrent episodes.

Conclusions

We found H. influenzae and S. pneumoniae to be the main pathogens causing AOM in Venezuela. Pneumococcal conjugate vaccines with efficacy against these bacterial pathogens may have the potential to maximize protection against AOM.

Burden and typing of rotavirus group A in Latin America and the Caribbean: systematic review and meta-analysis

The efficacy of licensed rotavirus vaccines has only been shown against certain rotavirus group A (RV-A) types. It is critical to understand the burden of rotavirus gastroenteritis (RVGE) and its prevalent types to assess the potential impact of these vaccines in Latin America and the Caribbean (LA&C). We performed a systematic review and meta-analyses of all the available evidence reported from 1990 to 2009 on the burden of rotavirus disease and strains circulating in LA&C. Eligible studies--185 country-level reports, 174 951 faecal samples--were selected from MEDLINE, Cochrane Library, EMBASE, LILACS, regional Ministries of Health, PAHO, regional proceedings, doctoral theses, reference lists of included studies and consulting experts. Arc-sine transformations and DerSimonian-Laird random-effects model were used for meta-analyses. The proportion of gastroenteritis cases due to rotavirus was 24.3% (95%CI 22.3-26.4) and the incidence of RVGE was 170 per 1000 children-years (95%CI 130-210). We estimated a global annual mortality for 22 countries of 88.2 (95%CI 79.3-97.1) deaths per 100 000 under 5 years (47 000 deaths).The most common G type detected was G1 (34.2%), followed by G9 (14.6%), and G2 (14.4%). The most common P types detected were P[8] (56.2%), P[4] (22.1%) and P[1] 5.4%, and the most prevalent P-G type associations were P[8]G1 17.9%, P[4]G2 9.1% and P[8]G9 8.8%. In the last 10 years, G9 circulation increased remarkably and G5 almost disappeared. More recently, G12 appeared and P[4]G2 re-emerged. To our knowledge, this is the first meta-analysis of rotavirus infection and burden of disease in LA&C.

Rotavirus genotypes in Costa Rica, Nicaragua, Honduras and the Dominican Republic

In this study, 574 stool samples from children with gastroenteritis were obtained from different hospitals in Costa Rica, Honduras, Nicaragua and the Dominican Republic during 2005-2006. Diarrhea stool samples were analyzed for rotavirus by ELISA and typed by the RT-PCR-based method. Unusual strains were detected: G1P6, G2P8, G3P6, G9P4 and mixed infections. Recent studies have indicated that unusual human rotavirus strains are emerging as global strains, which has important implications for effective vaccine development. In this context, the next generation of rotavirus vaccines will need to provide adequate protection against diseases caused not only by mixed infections, but also by unusual G/P combinations.

Diversity of human rotavirus G and P genotypes in Panama, Costa Rica, and the Dominican Republic

In this study 2,089 fecal samples from patients with gastroenteritis were analyzed from different hospitals in Panama, Costa Rica, and the Dominican Republic during the period comprised between December 2002 and July 2003. One hundred samples per country from the positives to the enzyme-linked immunosorbent assay (ELISA) kit were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) to determine the G and P genotypes: in Panama, Costa Rica, and Dominican Republic the combinations G and P have a great diversity and unusual genotypes. These results highlight an unexpected diversity among rotavirus strains in these countries and emphasize the need for further serologic and genetic surveys on more rotavirus strains in Central America and the Caribbean. In this context, the next generation of rotavirus vaccines will need to provide adequate protection against diseases caused by unusual genotypes. These results represent the second report of rotavirus genotypes in Costa Rica and first-time reports of rotavirus genotypes in Panama and the Dominican Republic.

Benefit of vitamin A supplementation on ascaris reinfection is less evident in stunted children

Despite the common coexistence of vitamin A deficiency and Ascaris infection in preschool children in developing countries, and despite the widespread use of vitamin A supplements, remarkably little is understood about the impact of vitamin A supplementation on this gastrointestinal nematode. The Ministry of Health of Panama recently initiated a vitamin A supplementation program in rural indigenous populations. We took advantage of this initiative to assess the benefit of 200,000 IU (60 mg retinol) vitamin A on reinfection with Ascaris following deworming. Baseline stool exams, anthropometry, and socio-economic data were collected for 328 preschool children from 12-60 mo of age (106 supplemented within previous 3 mo and 222 unsupplemented within previous 6 mo). All children were dewormed with albendazole, and reinfection levels were monitored 3 and 5 mo later. Baseline prevalence of Ascaris was 79.5%. Stepwise regression showed that Ascaris intensity was lower in Vit A-supplemented children at baseline and 3 mo after deworming, but not after 5 mo. As 61% of the children were stunted, the impact of supplementation on Ascaris reinfection was examined separately for stunted and children of normal height. Prevalence and intensity of Ascaris at baseline and 3 mo after deworming were lower in children of normal height, but in stunted children the benefit was restricted to those who were dewormed within 6 wk of supplementation. Our study provides evidence that combined vitamin A supplementation and deworming reduces Ascaris reinfection in children living in areas of chronic parasitosis, but that the duration of the benefit is less in stunted children.

Caucanolides A-F, unusual antiplasmodial constituents from a colombian collection of the gorgonian coral Pseudopterogorgia bipinnata

Six new diterpenoids, caucanolides A-F (1-6), have been isolated from extracts of the gorgonian octocoral Pseudopterogorgia bipinnata collected near the Colombian Southwestern Caribbean Sea. The structures of 1-6 were elucidated by comprehensive analysis of spectroscopic data. The caucanolides showed in vitro antiplasmodial activity against the malaria parasite, Plasmodium falciparum. In addition to possessing structures based on novel carbon skeletons, one of these metabolites, caucanolide B (2), constitutes the only example from nature of a secondary metabolite possessing the N(1),N(1)-dimethyl-N(2)-acylformamidine functionality.

Antitrypanosomal activity of a novel norlignan purified from Nectandra lineata

Bioactivity-guided fractionation of a MeOH-EtOAc extract from the young leaves of Nectandra lineata (Lauraceae), using a Trypanosoma cruzi bioassay resulted in the isolation of a novel norlignan 3'-methoxy-3,4-methylenedioxy-4',7-epoxy-9-nor-8,5'-neolignan-9'-acetoxy (1), together with the known compound, 3'-methoxy-3,4-methylenedioxy-4'-7-epoxy-9-nor-8,5'-neolignan-7,8'-diene (2). Compounds 1 and 2 were shown to inhibit the growth of T. cruzi epimastigotes in axenic culture.

Sesquiterpenoid metabolites with antiplasmodial activity from a Caribbean gorgonian coral, Eunicea sp

A chemical investigation of the Caribbean gorgonian octocoral Eunicea sp. collected along the northwest coast of Puerto Rico has afforded seven new secondary metabolites, 1-7, belonging to several types of sesquiterpenes, including elemane, eudesmane, and germacrane types, along with the known steroidal glycoside 8. Some of the new metabolites, 4-7, carry an unusual ester side chain at the C-6 position. The structures of all compounds, including their relative stereochemistry, were determined by combined spectroscopic methods. The present compounds exhibited a significant inhibitory effect upon the growth of the malarial parasite Plasmodium falciparum.

Bielschowskysin, a gorgonian-derived biologically active diterpene with an unprecedented carbon skeleton

Bielschowskysin is a naturally occurring diterpene isolated from the Caribbean gorgonian octocoral Pseudopterogorgia kallos. Its highly oxygenated hexacyclic structure is based on a previously undescribed tricyclo[9.3.0.0(2,10)]tetradecane ring system that was established through spectroscopic analysis and X-ray crystallographic analysis. Bielschowskysin was shown to exhibit antimalarial activity against Plasmodium falciparum as well as strong anticancer activity against two human cancer cell lines.

New pseudopterosin and seco-pseudopterosin diterpene glycosides from two Colombian isolates of Pseudopterogorgia elisabethae and their diverse biological activities

As part of an ongoing program to explore the chemical constituents of Caribbean marine invertebrates, a family of 13 new diterpene glycosides, pseudopterosins P-Z (1-11) and seco-pseudopterosins H (12) and I (13), have been isolated from the organic extracts of two collections of the sea whip Pseudopterogorgia elisabethae procured near the Colombian Southwestern Caribbean Sea. The structures of compounds 1-13, including absolute stereochemistry, have been proposed on the basis of comprehensive spectral analyses, chemical transformations, specific rotation, and TLC chromatographic analyses. Pseudopterosin Q (2) inhibited thromboxane B2 (TXB2) (IC50 = 4.7 microM) and superoxide anion (O2-) (IC50 = 11.2 microM) generation from E. coli lipopolysaccharide (LPS) activated rat neonatal microglia in vitro. In contrast, pseudopterosins P (1), U (6), V (7), W (8), and X (9) as well as seco-pseudopterosins H (12) and I (13) demonstrated minimal effects on both TXB2 and O2- release. In addition, some of the new compounds displayed strong antituberculosis, antiviral, antimalarial, and anticancer activity.

Real-time polymerase chain reaction diagnosis of leishmaniasis in Panama from both fresh and frozen tissue

Skin biopsies stored in ethanol from 49 patients with suspected cutaneous leishmaniasis (CL) were tested in a real-time polymerase chain reaction (PCR) assay and compared with conventional diagnostic methods. With clinical diagnosis as the gold standard, PCR had a sensitivity of 96% (47/49) vs. 61% (30/49) for histopathology and 33% (16/49) for culture. In addition, DNA was extracted from 70 frozen smears of lesions from suspected cases of CL and tested with the same assay. In these samples, the PCR had a sensitivity of 61% (43/70) vs. 56% (39/70) for histopathology and 41% (29/70) for culture. In this study, real-time PCR offered a rapid diagnosis with an enhanced sensitivity over conventional methods. Although the yield of PCR diagnosis was lower when testing frozen smears, the assay still outperformed existing diagnostic modalities.

A novel DNA-based microfluorimetric method to evaluate antimalarial drug activity

This paper describes the development of a novel microfluorimetric assay to measure the inhibition of Plasmodium falciparum based on the detection of parasitic DNA by intercalation with PicoGreen. The method was used to determine parasite inhibition profiles and 50% inhibitory concentration values of known or potential antimalarial drugs. Values for parasite inhibition with known anti-malarial drugs using the PicoGreen assay were comparable with those determined by the standard method based upon the uptake of 3H-hypoxanthine and the Giemsa stain microscopic technique. The PicoGreen assay is rapid, sensitive, reproducible, easily interpreted, and ideally suited for screening of large numbers of samples for anti-malarial drug development.

Briarellins J-P and polyanthellin A: new eunicellin-based diterpenes from the gorgonian coral Briareum polyanthes and their antimalarial activity

A new chemical study of the hexane extract of the gorgonian Briareum polyanthes collected in Puerto Rico afforded 10 new diterpenes of the eunicellin class, briarellins 1-9 and polyanthellin A (10), along with the known diterpene briarellin D (11). The structures and relative stereochemistry of metabolites 1-10 were assigned on the basis of NMR studies, chemical methods, and comparisons to the spectral properties of 11. A reassessment of prior structural assignment for briarellin A and two known sclerophytin-type diterpenes, 13 and 14, is proposed. Antimalarial tests on 1-6 and 8-12 indicated that they were active against Plasmodium falciparum.

Antigenic significance of a Trypanosoma rangeli sialidase

The Trypanosoma rangeli-secreted sialidase was purified by bovine submaxillary gland mucin-sepharose affinity chromatography. In immunoblotting analysis, antibodies raised against this molecule recognized polypeptides of 73 kDa in T. rangeli medium supernatant (TrSialr) and of 70 kDa in the cell lysates of T. rangeli (TrSials) and T. cruzi (TcSialL) epimastigotes. TrSialr, TrSials, and TcSialL were subjected to proteolytic cleavage with papain; the resultant peptide pattern displayed differences in the immunoblotting profiles. TrSials was purified by immunoprecipitation, and this protein band was recognized by sera from T. cruzi-infected chronic mice and Chagas' disease patients. In contrast, TrSialr was not recognized by these sera. The antibodies from the infected mice also recognized a band of 70 kDa present in the medium. These preliminary observations imply that the released and somatic sialidases are partially different molecules, with probably different biological roles. The related proteins recognized in T. rangeli and T. cruzi epimastigotes share many antigenic characteristics but have some structural differences, probably related to their function in the parasitic cell. On the basis of the strong antigenicity of TrSials, this molecule is proposed as the antigen for the detection of antibodies arising during T. cruzi infection.

Toxoplasma gondii homologue of plasmodium apical membrane antigen 1 is involved in invasion of host cells

Proteins with constitutive or transient localization on the surface of Apicomplexa parasites are of particular interest for their potential role in the invasion of host cells. We describe the identification and characterization of TgAMA1, the Toxoplasma gondii homolog of the Plasmodium apical membrane antigen 1 (AMA1), which has been shown to elicit a protective immune response against merozoites dependent on the correct pairing of its numerous disulfide bonds. TgAMA1 shows between 19% (Plasmodium berghei) and 26% (Plasmodium yoelii) overall identity to the different Plasmodium AMA1 homologs and has a conserved arrangement of 16 cysteine residues and a putative transmembrane domain, indicating a similar architecture. The single-copy TgAMA1 gene is interrupted by seven introns and is transcribed into an mRNA of approximately 3.3 kb. The TgAMA1 protein is produced during intracellular tachyzoite replication and initially localizes to the micronemes, as determined by immunofluorescence assay and immunoelectron microscopy. Upon release of mature tachyzoites, TgAMA1 is found distributed predominantly on the apical end of the parasite surface. A approximately 54-kDa cleavage product of the large ectodomain is continuously released into the medium by extracellular parasites. Mouse antiserum against recombinant TgAMA1 blocked invasion of new host cells by approximately 40%. This and our inability to produce a viable TgAMA1 knock-out mutant indicate that this phylogenetically conserved protein fulfills a key function in the invasion of host cells by extracellular T. gondii tachyzoites.

A Toxoplasma lectin-like activity specific for sulfated polysaccharides is involved in host cell infection

Toxoplasma gondii is one of the most widespread parasites of humans and animals. The parasite has a remarkable ability to invade a broad range of cells within its mammalian hosts by mechanisms that are poorly understood at the molecular level. This broad host cell specificity suggests that adhesion should involve the recognition of ubiquitous surface-exposed host molecules or, alternatively, the presence of various parasite attachment molecules able to recognize different host cell receptors. We have discovered a sugar-binding activity (lectin) in tachyzoites of T. gondii that plays a role in vitro in erythrocyte agglutination and infection of human fibroblasts and epithelial cells. The ability to agglutinate erythrocytes can be reversed by a variety of soluble glycoconjugates, of which heparin, fucoidan, and dextran sulfate were the most effective. Interestingly, infectivity of tachyzoites for human foreskin fibroblasts, cells that are commonly used to grow T. gondii in vitro, was increased by low concentrations of the sulfated glycoconjugates that inhibited hemagglutination activity (i.e. dextran sulfate and fucoidan) whereas high concentrations inhibited parasite infection. Furthermore, inhibition of glycosaminoglycan biosynthesis and sulfation on the host cells reduced Toxoplasma infectivity. Finally, Toxoplasma tachyzoites showed a reduced ability to infect epithelial cell mutants deficient in the biosynthesis of surface proteoglycans. The probable identity of the hemagglutinin(s) was investigated by 1) direct binding of red blood cells to filter blots of Toxoplasma proteins separated by polyacrylamide gel electrophoresis, and 2) binding of metabolically labeled parasite proteins to fixed mammalian cells. Three parasite bands were thus identified as candidate adhesins. These results suggest that attachment of T. gondii to its target cell is mediated by parasite lectins and that sulfated sugars on the surface of host cells may function as a key parasite receptor.

Genetic and biochemical analysis of development in Toxoplasma gondii

Toxoplasma gondii has recently come under intense study as a model for intracellular parasitism because it has a number of properties that facilitate experimental manipulation. Attention is now being turned towards understanding the developmental biology of this complex parasite. The differentiation between the two asexual stages, the rapidly growing tachyzoites and the more slowly dividing, encysted bradyzoites, is of particular interest. Progression from the former to the latter is influenced by the host's immune response. This paper describes current progress on a number of research fronts, all aimed at understanding the triggers that push the tachyzoite-bradyzoite equilibrium in one or other direction and the changes that occur in gene expression (and ultimately metabolism and function). Chief among the techniques used for these studies are genetics and molecular genetics. Recent progress in these areas is described.