Identification of associated risk factors for serological distribution of hepatitis B virus via machine learning models

BACKGROUND

The provincial-level sero-survey was launched to learn the updated seroprevalence of hepatitis B virus (HBV) infection in the general population aged 1-69 years in Chongqing and to assess the risk factors for HBV infection to effectively screen persons with chronic hepatitis B (CHB).

METHODS

A total of 1828 individuals aged 1-69 years were investigated, and hepatitis B surface antigen (HBsAg), antibody to HBsAg (HBsAb), and antibody to B core antigen (HBcAb) were detected. Logistic regression and three machine learning (ML) algorithms, including random forest (RF), support vector machine (SVM), and stochastic gradient boosting (SGB), were developed for analysis.

RESULTS

The HBsAg prevalence of the total population was 3.83%, and among persons aged 1-14 years and 15-69 years, it was 0.24% and 4.89%, respectively. A large figure of 95.18% (770/809) of adults was unaware of their occult HBV infection. Age, region, and immunization history were found to be statistically associated with HBcAb prevalence with a logistic regression model. The prediction accuracies were 0.717, 0.727, and 0.725 for the proposed RF, SVM, and SGB models, respectively.

CONCLUSIONS

The logistic regression integrated with ML models could helpfully screen the risk factors for HBV infection and identify high-risk populations with CHB.

Equine influenza outbreak in Eastern of Algeria in 2021: The first introduction of Florida Clade 1 to Maghreb area

We have performed an equine influenza (EI) serological study of the equine population in Algeria by testing 298 serum samples collected between February and August 2021 from 5 provinces. The results were obtained performing an NP-ELISA. Our results revealed that 49.3% (147/298) samples positive for antibodies to EI (H3N8). During this study and after a gap of one decade an outbreak of EI was reported in Algeria in the first week of March 2021. The disease was confirmed by virus detection from the nasal swabs (n = 39) by qRT-PCR and by identifying 5 EI seroconversion. The virus sequences were identified as H3N8 by sequencing the haemagglutinin (HA) and neuraminidase (NA) genes. Alignment of HA1 amino acid sequence confirmed that viruses belong to Clade 1 of the Florida sublineage in the American lineage. This study indicate the first detection of FC1 strain of EIV in Maghreb area.

Immunity of Canadians and risk of epidemics workshop - Conference report

On November 18-19, 2019, the Immunity of Canadians and Risk of Epidemics (iCARE) Network convened a workshop in Toronto, Ontario, Canada. The objectives of the workshop were to raise the profile of sero-epidemiology in Canada, discuss best practice and methodological innovations, and strategize on the future direction of sero-epidemiology work in Canada. In this conference report, we describe the presentations and discussions from the workshop, and comment on the impact of the COVID-19 pandemic on serosurveillance initiatives, both in Canada and abroad.

Incidence rate and predictors of COVID-19 in the two largest cities of Burkina Faso - prospective cohort study in 2021 (ANRS-COV13)

BACKGROUND

Early data on COVID-19 (based primarily on PCR testing) indicated a low burden in Sub-Saharan Africa. To better understand this, this study aimed to estimate the incidence rate and identify predictors of SARS-CoV-2 seroconversion in the two largest cities of Burkina Faso. This study is part of the EmulCOVID-19 project (ANRS-COV13).

METHODS

Our study utilized the WHO Unity protocol for cohort sero-epidemiological studies of COVID-19 in general population. We conducted random sampling stratified by age group and sex. Individuals aged 10 years and older in the cities of Ouagadougou and Bobo-Dioulasso, Burkina Faso were included and surveyed at 4 time points, each 21 days apart, from March 3 to May 15, 2021. WANTAI SARS-CoV-2 Ab ELISA serological tests were used to detect total antibodies (IgM, IgG) in serum. Predictors were investigated using Cox proportional hazards regression.

RESULTS

We analyzed the data from 1399 participants (1051 in Ouagadougou, 348 in Bobo-Dioulasso) who were SARS-CoV-2 seronegative at baseline and had at least one follow-up visit. The incidence rate of SARS-CoV-2 seroconversion was 14.3 cases [95%CI 13.3-15.4] per 100 person-weeks. The incidence rate was almost three times higher in Ouagadougou than in Bobo-Dioulasso (Incidence rate ratio: IRR = 2.7 [2.2-3.2], p < 0.001). The highest incidence rate was reported among women aged 19-59 years in Ouagadougou (22.8 cases [19.6-26.4] per 100 person-weeks) and the lowest among participants aged 60 years and over in Bobo-Dioulasso, 6.3 cases [4.6-8.6] per 100 person-weeks. Multivariable analysis showed that participants aged 19 years and older were almost twice as likely to seroconvert during the study period compared with those aged 10 to 18 years (Hazard ratio: HR = 1.7 [1.3-2.3], p < 0.001). Those aged 10-18 years exhibited more asymptomatic forms than those aged 19 years and older, among those who achieved seroconversion (72.9% vs. 40.4%, p < 0.001).

CONCLUSION

The spread of COVID-19 is more rapid in adults and in large cities. Strategies to control this pandemic in Burkina Faso, must take this into account. Adults living in large cities should be the priority targets for vaccination efforts against COVID-19.

SARS-CoV-2 sero-prevalence in the workforces of three large workplaces in South Wales: a sero-epidemiological study

BACKGROUND

Sero-prevalence studies quantify the proportion of a population that has antibodies against SARS-CoV-2, and can be used to identify the extent of the COVID-19 pandemic at a population level. The aim of the study was to assess the sero-prevalence of SARS-CoV-2 antibodies in the workforce at three workplaces: a food factory, non-food factory and call-centre.

METHODS

Nine hundred ninety-three participants were recruited from three workplaces in South Wales. Participants completed a questionnaire and had a lateral flow point-of-care SARS-CoV-2 antibody test administered by a healthcare professional. The data were analysed using multivariable logistic regression, both using complete records only and following multiple imputation.

RESULTS

The sero-prevalence of SARS-CoV-2 antibodies ranged from 4% (n = 17/402) in the non-food factory to 10% (n = 28/281) in the food factory (OR 2.93; 95% CI 1.26 to 6.81). After taking account of confounding factors evidence of a difference remained (cOR comparing food factory to call centre (2.93; 95% CI 1.26 to 6.81) and non-food factory (3.99; 95% CI 1.97 to 8.08) respectively). The SARS-CoV-2 antibody prevalence also varied between roles within workplaces. People working in office based roles had a 2.23 times greater conditional odds (95% CI 1.02 to 4.87) of being positive for SARS-CoV-2 antibodies than those working on the factory floor.

CONCLUSION

The sero-prevalence of SARS-CoV-2 antibodies varied by workplace and work role. Whilst it is not possible to state whether these differences are due to COVID-19 transmission within the workplaces, it highlights the importance of considering COVID-19 transmission in a range of workplaces and work roles.

COVID-19 epidemiological, sociological and anthropological investigation: study protocol for a multidisciplinary mixed methods research in Burkina Faso

BACKGROUND

The world has high hopes of vaccination against COVID-19 to protect the population, boost economies and return to normal life. Vaccination programmes are being rolled out in high income countries, but the pandemic continues to progress in many low-and middle-income countries (LMICs) despite implementation of strict hygiene measures. We aim to present a comprehensive research protocol that will generate epidemiological, sociological and anthropological data about the COVID-19 epidemic in Burkina Faso, a landlocked country in West Africa with scarce resources.

METHODS

We will perform a multidisciplinary research using mixed methods in the two main cities in Burkina Faso (Ouagadougou and Bobo-Dioulasso). Data will be collected in the general population and in COVID-19 patients, caregivers and health care professionals in reference care centers: (i) to determine cumulative incidence of SARS-CoV-2 infection in the Burkinabe population using blood samples collected from randomly selected households according to the WHO-recommended protocol; (ii) develop a score to predict severe complications of COVID-19 in persons infected with SARS-CoV-2 using retrospective and prospective data; (iii) perform semi-structured interviews and direct observation on site, to describe and analyze the healthcare pathways and experiences of patients with COVID-19 attending reference care centers, and to identify the perceptions, acceptability and application of preventive strategies among the population.

DISCUSSION

This study will generate comprehensive data that will contribute to improving COVID-19 response strategies in Burkina Faso. The lessons learned from the management of this epidemic may serve as examples to the country authorities to better design preventive strategies in the case of future epidemics or pandemics. The protocol was approved by the Ministry for Health (N° 2020-00952/MS/CAB/INSP/CM) and the Health Research Ethics Committee in Burkina Faso (N° 2020-8-140).

Sero-epidemiology and associated factors of HIV, HBV, HCV and syphilis among blood donors in Ethiopia: a systematic review and meta-analysis

BACKGROUND

Transfusion transmissible infections (TTIs) remain a major public health problem in developing countries including Ethiopia. In Ethiopia, comprehensive information about sero-epidemiology of major TTIs is lacking at the national level. Therefore, this systematic review and meta-analysis was aimed at providing the pooled estimate of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV) and syphilis among blood donors in Ethiopia.

METHODS

Relevant studies published until May 31, 2019 were searched through PubMed/Medline, EMBASE, SCOPUS, HINARI, Cochrane database library, Web of Science, Google Scholar and Google. The methodological quality of articles was assessed using Joanna Brigg's Institute critical appraisal checklist for prevalence and analytical studies. The pooled sero-epidemiology of HIV, HBV, HCV and syphilis were determined using the random-effects model. Heterogeneity between the studies was assessed using the I² statistics. Publication bias was assessed by visual inspection of the funnel plot and Egger's statistics.

RESULTS

A total of 7921 articles were retrieved, and 7798 were screened for eligibility after duplicates removed. Forty-nine full-text articles were assessed for eligibility; of which 45 were eligible for qualitative and quantitative synthesis: categorized as 36, 34, 31 and 23 studies for estimations of HBV, HIV, HCV and syphilis, respectively. In the random-effects model, the pooled sero-epidemiology of HBV, HIV, HCV and syphilis was 5.20, 2.83, 0.93 and 1.50%, respectively. Moreover, being a male blood donor was significantly associated with HBV and syphilis infection, whereas being a replacement blood donor was significantly associated with a high burden of HIV, HBV and HCV infections.

CONCLUSION

The pooled sero-epidemiology of major TTIs among blood donors was high. Therefore, there is a need to design prevention and control strategies in a comprehensive approach to reduce the burden.

Demographic, socioeconomic and disease knowledge factors, but not population mobility, associated with lymphatic filariasis infection in adult workers in American Samoa in 2014

Background

Prevalence of lymphatic filariasis (LF) antigen in American Samoa was 16.5% in 1999. Seven rounds of mass drug administration (MDA) programmes between 2000 and 2006 reduced antigen prevalence to 2.3%. The most efficient methods of surveillance after MDA are not clear, but testing specific at-risk groups such as adults may provide earlier warning of resurgence. The role of migration from LF endemic countries in maintaining transmission also needs investigation. Few studies have investigated knowledge about LF and how that relates to infection risk. This study aims to investigate associations between socio-demographics, population mobility, disease knowledge and LF infection risk.

Methods

In 2014, we surveyed 670 adults aged 16–68 years (62% female) at two worksites in American Samoa. Sera were tested for LF antigen and antibodies (Bm14 and Wb123) by rapid test and/or ELISA. Multivariate logistic regression was used to assess association between seromarkers and demographic factors, household socioeconomic status (SES), residence, travel history, and knowledge of LF.

Results

Overall, 1.8% of participants were positive for antigen, 11.8% for Bm14, 11.3% for Wb123 and 17.3% for at least one antibody. Recent travel outside American Samoa was not associated with positivity for any seromarker. Men had higher seroprevalence than women for all outcomes (any antibody: adjusted odds ratio (aOR) = 3.49 (95% CI: 2.21–5.49). Those aged over 35 years (compared to 15–24 years) had higher prevalence of Bm14 antibody (aOR = 3.75, 3.76 and 4.17 for ages 35–44, 45–54 and ≥ 55 years, respectively, P < 0.05). Lower SES was associated with seropositivity (antigen: aOR = 2.89, 95% CI: 1.09–7.69; either antibody: aOR = 1.51, 95% CI: 1.12–2.05). Those who knew that mosquitoes transmitted LF had lower Wb123 antibody prevalence (aOR = 0.55, 95% CI: 0.32–0.95).

Conclusions

Opportunistic sampling of adults at worksites provided an efficient and representative way to assess prevalence and risk factors for LF in American Samoa and in hindsight, foreshadowed the resurgence of transmission. Risk of LF infection, detected by one or more serological markers, was not related to recent travel history, but was strongly associated with male gender, older age, lower SES, and lack of knowledge about mosquito transmission. These results could guide future efforts to increase MDA participation.

Evaluation of a PGP3 ELISA for surveillance of the burden of Chlamydia infection in women from Australia and Samoa

Serological assays can be used to investigate the population burden of infection and potentially sequelae from Chlamydia. We investigated the PGP3 ELISA as a sero-epidemiological tool for infection or sub-fertility in Australian and Samoan women. The PGP3 ELISA absorbance levels were compared between groups of women with infertility, fertile, and current chlamydial infections. In the Australian groups, women with chlamydial tubal factor infertility had significantly higher absorbance levels in the PGP3 ELISA compared to fertile women (P < 0.0001), but not when compared to women with current chlamydial infection (P = 0.44). In the Samoan study, where the prevalence of chlamydial infections is much higher there were significant differences in the PGP3 ELISA absorbance levels between chlamydial sub-fertile women and fertile women (P = 0.003). There was no difference between chlamydial sub-fertile women and women with a current infection (P = 0.829). The results support that the PGP3 assay is effective for sero-epidemiological analysis of burden of infection, but not for evaluation of chlamydial pathological sequelae such as infertility.

High varicella zoster virus susceptibility in Caribbean island populations: Implications for vaccination

OBJECTIVES

Varicella zoster virus (VZV) infection is reported regularly among adolescents and adults in Caribbean island populations. The disease more often runs a severe course among these populations, causing a substantial burden. The aim of this sero-epidemiological study was to obtain an insight into VZV susceptibility and its determinants in island populations of the Caribbean Netherlands (CN).

METHODS

Participants from Bonaire, St. Eustatius, and Saba (n = 1829, aged 0-90 years) donated a blood sample and completed a questionnaire. VZV-specific IgG antibodies were determined using a bead-based multiplex immunoassay. Risk factors were analysed using a logistic regression model.

RESULTS

Overall seroprevalence in CN was 78%, being lowest on St. Eustatius (73%) and highest on Bonaire and Saba (79%). Seropositivity increased gradually with age, with 60% and 80% at ages 10 years and 30 years, respectively, and ranging between 80% and 90% thereafter. Higher odds for VZV seronegativity were seen among persons who were born in CN or had resided there since early childhood, and among single-person households.

CONCLUSIONS

VZV susceptibility is relatively high among adolescents and adults in CN. In order to reduce the burden of VZV-related disease in these populations, routine varicella vaccination is recommended. As data are scarce, the study findings can serve as a blueprint for the epidemiology in tropical regions.

Vaccine acquired pertussis immunity was weakened at 4 years of age and asymptomatic pertussis infection was suspected based on serological surveillance

Serological surveillance of pertussis antibodies was performed in 118 children aged 1-12 years. The positivity of pertussis toxin (PT) antibodies was low at 4-6 years and significantly higher at 8-9 years, compared with those at 6 years. Fimbriae 2 (Fim2) antibody showed similar response to the PT antibody. Higher antibody titers against Fim3 were observed among subjects ≥5 years and highest at 8 years. Data demonstrated that the vaccine-induced antibodies decayed by 4-5 years and subclinical pertussis infection was suspected thereafter, suggesting the need for additional dose at around 4-5 years.

Profiling of serum antibodies against human papillomavirus antigens in Korean women with cervical intraepithelial neoplasia and cervical cancer

Sero-epidemiological studies of human papillomavirus (HPV) have been undertaken over the last two decades. In this study, the prevalences of nine serum antibodies (anti-E6, E7 and L1 antibodies of HPV types 16, 18, and 58) were evaluated in normal (control) Korean women and women with cervical intraepithelial neoplasia (CIN) I, CIN II, CIN III, and cervical cancer. The frequencies of all types of anti-HPV antibodies were higher in the CIN stages and cervical cancer than in normal women, and those of anti-HPV16 E6 and E7, anti-HPV18 E6 and E7, and anti-HPV58 E7 antibodies were higher in the cervical cancer group than in the CIN stages. The frequencies of antibodies against HPV16, 18, and 58 E7 tended to increase with increasing severity of cervical lesions. However, there were few differences in the frequencies of antibodies against the L1 antigens of HPV16, 18 and 58 in cervical cancer versus CIN stages. The anti-HPV antibodies were detected in 26.5% of normal, 46.3% of CIN I, 62.5% of CIN II, 51.6% of CIN III, and 75% of cancers when any of the nine antigens was used as a criterion. Correlations between HPV DNA positivity and seropositivity for anti-HPV E6, E7, or L1 antibodies were found only in HPV16 DNA-positive cervical cancers for anti-HPV16 E6 and L1 antibodies. In addition, strong positive correlations in seropositivity were found between anti-HPV16 E7 and anti-HPV58 E7 antibodies, and between anti-HPV18 E6 and anti-HPV58 E6 antibodies. These findings should advance global profiling of the seroprevalences of antibodies against HPV antigens.

[A sero-epidemiological survey of Toxoplasma gondii infections in high-risk populations in Hangzhou City]

OBJECTIVE

To understand the status of Toxoplasma gondii infections and the awareness of toxoplasmosis prevention and control knowledge among high-risk populations in Hangzhou City.

METHODS

The serum anti-T. gondii antibodies were detected in 100 HIV/AIDS patients, 100 cancer patients, 100 pregnant women and 100 healthy controls, and the awareness of toxoplasmosis prevention and control knowledge was investigated using a questionnaire.

RESULTS

The sero-prevalence of T. gondii infection was 31%, 30% and 21% in HIV/AIDS patients, cancer patients and pregnant women, which was all significantly higher than in healthy controls (χ² = 14.68, 13.96 and 7.56, all P values < 0.01). The pregnant women had a high awareness rate of toxoplasmosis prevention and control knowledge, and the healthy controls had a low awareness rate. In addition, the subjects had a low awareness rate regarding the questions including"Do you know the damages of Toxoplasma gondii infections?", "Do you know that consumption of raw or uncooked meat may cause Toxoplasma gondii infections?", and"Do you know that contact with contaminated soil may cause Toxoplasma gondii infections?".

CONCLUSIONS

The sero-prevalence of T. gondii infection is high among the high-risk populations in Hangzhou City, including the HIV/AIDS patients, cancer patients and pregnant women, and these high-risk populations have a low awareness rate of some toxoplasmosis prevention and control knowledge. Therefore, it is essential to improve the health education of toxoplasmosis prevention and control knowledge among the high-risk populations, so as to effectively prevent and control human T. gondii infections.

[Investigation on Toxoplasma gondii infection and awareness of toxoplasmosis-related knowledge in women with poor pregnant outcomes in Wuxi City]

OBJECTIVE

To investigate the prevalence of Toxoplasma gondii infection and awareness of toxoplasmosis-related knowledge among women with poor pregnant outcomes in Wuxi City.

METHODS

A total of 217 women with poor pregnant outcomes from Wuxi City during the period of January 2011 to December 2015 were randomly selected as the study subjects (a study group), while 250 women with normal pregnancy were served as controls (a control group). The sero-prevalence of T. gondii infection was detected by using ELISA and compared between the study and control groups. The awareness of toxoplasmosis-related knowledge was investigated by using a self-designed questionnaire and compared between the study and control groups.

RESULTS

The positive rate of anti-Toxoplasma antibody was 30.88% in the study group, which was significantly higher than that (8.8%) in the control group (χ² = 36.7, P < 0.01). The positive rates of anti-Toxoplasma IgG and IgM antibodies were 20.74% and 10.14% in the study group respectively, which were significantly higher than those (6% and 2.8%) in the control group (χ² = 22.53 and 10.74, both P values < 0.01). In addition, the positive rates of anti-Toxoplasma, anti-Toxoplasma IgG and IgM antibodies were significantly higher in the women with missed miscarriage, natural abortion, stillbirth and birth defect than those in the women with normal pregnancy (all P values < 0.05). The awareness rates of "Do you hear about Toxoplasma or toxoplasmosis?" (P < 0.01), "Do you know that breeding pet cats or dogs may cause Toxoplasma infection?" (P < 0.05) and "Do you know that pregnancy women require the detection of Toxoplasma infection?" (P < 0.01) were significantly lower in the study group than those in the control group, while no significant differences were seen in the awareness rates of "Do you know that eating hot pot may cause Toxoplasma infection?", "Do you know that the use of chopping block in regardless of cooked and uncooked food may cause Toxoplasma infection?", "Do you know that Toxoplasma infection may transfer from mother to fetus?", "Do you know that Toxoplasma infection may cause adverse pregnant outcomes like abortion, stillbirth or fetal abnormalities ?", and "Do you know that the women infected with T. gondii during pregnancy require treatment?" between the two groups (all P values > 0.05).

CONCLUSIONS

This study demonstrates higher prevalence of T. gondii infection in women with poor pregnant outcomes than in those with normal pregnancy in Wuxi City. Considering the harm of T. gondii infection during pregnancy and the low awareness of toxoplasmosis-related knowledge in pregnant women, the health education of toxoplasmosis-related knowledge should be strengthened, especially for pregnant women, so as to reduce the prevalence of T. gondii infection among pregnant women to improve the better child-bearing and rearing level.

Sero-epidemiology of bluetongue virus (BTV) infection in sheep and goats of Khyber Pakhtunkhwa province of Pakistan

Bluetongue virus (BTV) infection is an emerging hazard in small ruminants having socio-economic impacts on animals and associated people. The current study was aimed to estimate the sero-prevalence and associated risk factors in sheep and goat from Khyber Pakhtunkhwa (KP) province of Pakistan. Three distinct zones (northern, central and southern) with four districts (Mansehra, Abbottabad, Swabi, and Kohat) with a higher population of small ruminants were selected. A total of n = 408 sera originating from sheep (n = 212) and goats (n = 196) were randomly collected for detection of BTV group specific antibodies through competitive ELISA (c-ELISA). Univariable and multiple logistic regressions were applied to assess the potential risk factors associated with the occurrence of this disease. Results showed an overall prevalence of 50.00% (CI = 44.17-54.83) of BTV in both sheep and goats with a significant difference (p < 0.05) among different districts. The prevalence of BTV in sheep was found higher (56.60%, CI = 49.6-63.4) than goats (42.86%, CI = 35.8-50.1). The risk factors identified based on chi-square test were; 1-2 year of animals, herd size and location in sheep while, milking status, ticks infestation, location and herd size for goats (p < 0.05). On the basis of univariable analysis, 1-2 year of animals, and location for sheep while, ticks infestation and location for goats (OR > 1). Multiple logistic regressions conferred only herd size and location as potential risk factors (OR > 1) for BTV in sheep and goats. The study concluded higher prevalence of BTV in sheep than the goats, the risk factors were significantly associated with the occurrence of disease, and together ascertaining the needs to design appropriate disease management and control strategies in sheep and goats.

Characterization of Plasmodium falciparum and Plasmodium vivax recent exposure in an area of significantly decreased transmission intensity in Central Vietnam

Background

In Vietnam, malaria transmission has been reduced to very low levels over the past 20 years, and as a consequence, the country aims to eliminate malaria by 2030. This study aimed to characterize the dynamics and extent of the parasite reservoir in Central Vietnam, in order to further target elimination strategies and surveillance.

Methods

A 1-year prospective cohort study (n = 429) was performed in three rural communities in Quang Nam province. Six malaria screenings were conducted between November 2014 and November 2015, including systematic clinical examination and blood sampling for malaria parasite identification, as well as molecular and serological analysis of the study population. Malaria infections were detected by light microscopy (LM) and quantitative real time PCR (qPCR), while exposure to Plasmodium falciparum and Plasmodium vivax was measured in the first and last survey by ELISA for PfAMA1, PfGLURP R2, PvAMA1, and PvMSP1-19. Classification and regression trees were used to define seropositivity and recent exposure.

Results

Four malaria infections (2 P. falciparum, 2 P. vivax) were detected in the same village by qPCR and/or LM. No fever cases were attributable to malaria. At the same time, the commune health centre (serving a larger area) reported few cases of confirmed malaria cases. Nevertheless, serological data proved that 13.5% of the surveyed population was exposed to P. falciparum and/or P. vivax parasites during the study period, of which 32.6% were seronegative at the start of the study, indicating ongoing transmission in the area. Risk factor analysis for seroprevalence and exposure to P. falciparum and/or P. vivax identified structural or economic risk factors and activity/behaviour-related factors, as well as spatial heterogeneity at the village level.

Conclusions

Previous studies in Central Vietnam demonstrated high occurrence of asymptomatic and sub-microscopic infections. However, in this study very few asymptomatic infections were detected despite serological evidence of continued transmission. Nonetheless, the factors associated with spatial heterogeneity in transmission could be evaluated using serological classification of recent exposure, which supports the usefulness of serological methods to monitor malaria transmission.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2326-1) contains supplementary material, which is available to authorized users.

Sero-epidemiology and hemato-biochemical study of bovine leptospirosis in flood affected zone of Pakistan

The bovine leptospirosis is an economically important zoonotic disease of flood affected areas worldwide, but scarce information is available about its epidemiology in Pakistan. This is a first study on sero-epidemiology of bovine leptospirosis in Pakistan. The objectives of this study were to investigate the sero-prevalence and associated risk factors of bovine leptospirosis in flood affected zone of Punjab, Pakistan. A total of 385 serum samples were randomly collected from four tehsils of district Muzaffargarh, Pakistan. The serum samples were subjected to indirect ELISA for the detection of anti-leptospira antibodies. The overall sero-prevalence of leptospirosis was 30.39%. The prevalence was significantly higher (p<0.001) in cattle (56.25%) than buffaloes (4.66%). The key risk factors identified based on multivariable logistic regression were; confined system of rearing, flooded area, and lesser to graduate level of education as risk factors for leptospirosis. The values of hematological parameters varied significantly (p<0.05) for Hb, TEC and PCV while there was no significant (p>0.05) difference among TLC values among sero-positive and sero-negative animals. The serum biochemical profile revealed significant differences (p<0.05) in values of ALT, AST and creatinine among the sero-positive and negative animals. Hence, it can be concluded that leptospirosis is an emerging and neglected disease in flood affected zone of Pakistan, and the disease needs to be explored comprehensively in other parts of the country to sort out solid strategies for its control and eradication.

Seroprevalence of hepatitis B and factors potentially associated in a population-based study in Medellin, Colombia

The seroprevalence of hepatitis B (HB) and of potentially associated factors in Medellin, Colombia, were investigated 17years after the start of universal vaccination. Biological and sociodemographic data from a population survey with a multistage random sampling were analyzed in 6-64year old individuals. HB surface antigen, total HB core antibodies and HB surface antibodies, and in some cases IgM antibodies to HB core antigen, were tested in 2077 samples. Factors potentially associated with and natural, and vaccine immunity relative to susceptibility (absence of any marker) were analyzed using a multinomial logistic regression. The prevalence of serological patterns was: chronic infection 0.20% (95% CI 0.11-0.71), vaccine immunity 25.10% (95% CI 21.72-28.83) and natural immunity 2.60% (95% CI 1.80-3.74). No markers were detected in 71.30% (95% CI 67.70-74.83) of the individuals and evidence of recent infection was not detected. Relative to the absence of markers, natural immunity was potentially associated with age (6-17years and 41-64years) and sleeping less than 6 hours, while vaccine immunity was associated with age (6-17years), reporting vaccination against HB, belonging to high socioeconomic strata, home ownership and being obese, after adjusting for other variables. These results may be a population effect of mass vaccination. It is recommended to complete the vaccination schedule and to study in detail, persistence of antibodies and the role of obesity and socioeconomic strata in the vaccine immunity.

A cross sectional survey measuring sero-incidence of pertussis infection among Japanese junior and senior high school students in 2013 and 2014

Pertussis in adolescents has been increasingly documented in recent years, but diagnosis from the clinical symptoms is difficult. Serological diagnosis with IgG antibody to pertussis toxin (IgG PT) is useful for detecting pertussis cases in this population. However, no serological criterion for recent infection has been fully validated and large-scale, longitudinal serological data among Japanese junior and senior high school students are lacking. Paired serum samples of 3243 junior and senior high school students, collected in 2013 and 2014, were analyzed for IgG PT and its relationship to possible risk factors. Regression analysis showed an average decrease of 35% in IgG PT between 2013 and 2014. In 2013, 4.4% of the students showed IgG PT levels ≥100EU/mL, as did 3.7% in 2014. The seroincidence, defined as [IgG PT] change from <100 in 2013 to ≥100EU/mL in 2014, was 10.3 cases per 1000 person-years. A 4-fold rise in IgG PT was seen in 2.1% of the students, with significant differences between schools and significant correlations to two risk factors, "over 2weeks coughing" and "exposure to a person with over 2weeks coughing". A substantial number of students had IgG PT ≥100EU/mL despite the observed 35% yearly decrease in IgG PT level. The local foci of ≥4-fold IgG PT increase in specific schools suggests the persistent circulation of B. pertussis in Japanese adolescents. The results also support a "≥4-fold rise in IgG PT" as a useful component of the sero-epidemiological surveillance for pertussis.

A systematic review on malaria sero-epidemiology studies in the Brazilian Amazon: insights into immunological markers for exposure and protection

Background

Considerable success in reducing malaria incidence and mortality has been achieved in Brazil, leading to discussions over the possibility of moving towards elimination. However, more than reporting and counting clinical cases, elimination will require the use of efficient tools and strategies for measuring transmission dynamics and detecting the infectious reservoir as the primary indicators of interest for surveillance and evaluation. Because acquisition and maintenance of anti-malarial antibodies depend on parasite exposure, seroprevalence rates could be used as a reliable tool for assessing malaria endemicity and an adjunct measure for monitoring transmission in a rapid and cost-effective manner.

Methods

This systematic review synthesizes the existing literature on seroprevalence of malaria in the Brazilian Amazon Basin. Different study designs (cross-sectional surveys and longitudinal studies) with reported serological results in well-defined Brazilian populations were considered. Medline (via PubMed), EMBASE and LILACS databases were screened and the articles were included per established selection criteria. Data extraction was performed by two authors and a modified critical appraisal tool was applied to assess the quality and completeness of cross-sectional studies regarding defined variables of interest.

Results

From 220 single records identified, 23 studies were included in this systematic review for the qualitative synthesis. Five studies reported serology results on Plasmodium falciparum, 14 papers assessed Plasmodium vivax and four articles reported results on both Plasmodium species. Considerable heterogeneity among the evaluated malarial antigens, including sporozoite and blood stage antigens, was observed. The majority of recent studies analysed IgG responses against P. vivax antigens reflecting the species distribution pattern in Brazil over the last decades. Most of the published papers were cross-sectional surveys (73.9%) and only six cohort studies were included in this review. Three studies pointed to an association between antibodies against circumsporozoite protein of both P. falciparum and P. vivax and malaria exposure. Furthermore, five out 13 cross-sectional studies evidenced a positive association between IgG antibodies to the conserved 19-kDa C-terminal region of the merozoite surface protein 1 of P. vivax (PvMSP1₁₉) and malaria exposure.

Conclusions

This systematic review identifies potential biomarkers of P. falciparum and P. vivax exposure in areas with variable and unstable malaria transmission in Brazil. However, this study highlights the need for standardization of further studies to provide an ideal monitoring tool to evaluate trends in malaria transmission and the effectiveness of malaria intervention programmes in Brazil. Moreover, the score-based weighted tool developed and used in this study still requires further validation.

Sero-epidemiology of cystic echinococcosis (Echinococcus granulosus) in the livestock of Oman

A cross-sectional serological survey of cystic echinocossis was carried out on 2802 randomly collected sera of camels (n=706), cattle (n=687), goats (n=701) and sheep (n=708) from all governorates of Oman. The samples were analysed by in house indirect ELISA (iELISA) using Echinococcus granulosus antigen B (EgAgB) of naturally infected camels. The overall percentage of antibodies against EgAgB was found to be 14.6%. The highest percentage of positive was observed in sera from camels (22.4%) followed by cattle (12.9%), sheep (12.2%) and goats (10.9%). The highest percentage of seropositivity was observed in females (15.4%) as compared to male animals (10.6%). The imported livestock were found more seropositive (15.2%) as compared to local (14.7%) and crossbred livestock (14.1%). The highest exposure was observed in animals with the age group of above 5years (18.3%) followed by the age group of up to 2years (15.1%,) and those between 2 and 5years (12.4%). The univariate analysis has indicated that camels (OR:2.33, CI 1.74, 3.14), cattle (OR:1.21, CI 0.87, 1.67), sheep (OR:1.12, CI 0.81, 1.55) were more likely to test positive than goats. Furthermore, females (OR: 1.53, CI 1.11, 2.11) were more likely to test seropositive. Sera from animals above 5years of age (OR:1.58, CI 1.25, 2.01) and between 2 and 5years old (OR:1.30, CI 0.98, 1.71) were found more likely to test seropositive than those up to 2years of age. The multivariable analysis at individual level indicated that camels (OR: 2.07, CI 1.66, 2.56, p<0.001) and female (OR: 1.43, CI 1.04, 1.98, p=0.030) were more likely to acquire CE. At herd level, the final multivariable model indicated that herds located in Dofar and Musandam (OR: 4.48, CI 2.69, 7.45, p<0.001), in areas receiving seasonal rains (OR: 2.54, CI 1.09, 5.90, p<0.001) and practicing transhumance (OR: 4.22, CI 1.84, 9.65, p<0.001) and sedentary (OR: 2.07, CI 1.38, 3.12, p=0.001) farming system were more likely to acquire CE in Oman. The study documents the serological evidence of CE in livestock of Oman and a carefully planned control program should be devised after further epidemiological and molecular investigations in the intermediate and final hosts.

Epidemiological Study of Toxocar canis in Children under 14-Years-Old and Dogs in Zabol and Chabahar Districts, Southeast of Iran

BACKGROUND

The purpose of this study was seroepidemiological and parasitological assessment of Toxocara canis infection in children and dogs in Zabol and Chabahar, Iran.

METHODS

This study was a descriptive-analytic study with a simple random sampling of children under 14 yr old, referring to urban, rural, and tribal laboratories of Zabol and Chabahar, Sistan and Baluchestan Province, Iran in 2016. Demographic data, clinical, and laboratory conditions of patients were collected through interviews, questionnaires, and blood count measuring. The prevalence of IgG antibodies against T. canis was assessed by ELISA. T. canis eggs in dogs (as the original host) were also assessed by examining animal feces. Then the data were analyzed using SPSS 19 software and descriptive statistics, chi-square and ANOVA statistical tests.

RESULTS

Totally, 364 patients were enrolled, of which 51.6% were female and mean±SD age of participants was 7.2 (±3.7) yr. IgG antibodies against T. canis was observed in 3.8% of cases. A significant association was found between the seroprevalence of T. canis and eosinophil (P=0.003) and red blood cell count (P=0.04). We also found a significant association between serological prevalence of T. canis and demographic parameters, such as city of residence (P=0.003), gender (P=0.04), consumption of vegetables (P=0.01), and the living place (P=0.04). Mean antibody titration was 2.2 ±1.1, with statistically significant difference among age groups (P=0.001). In addition, T. canis infection was positive in 27.5% of dogs living in the study areas.

CONCLUSION

High risk of infection represented in patients referring to laboratories of Zabol and Chabahar. In addition, given the fact that dogs are the final hosts to transfer Toxocara infection to humans, this study emphasizes the need to control the population of stray dogs in the region to prevent the development of disease in the human society.

Seroepidemiology of Human Hydatidosis Using AgB-ELISA Test in Isfahan City and Suburb Areas, Isfahan Province, Central Iran

BACKGROUND

The aim of this study was to conduct a sero-epidemiological survey in Isfahan City and suburb areas, central Iran to detect the rate of human hydatidosis using ELISA test.

METHODS

Overall, 635 serum samples were collected from subjects referred to different health centers in urban and rural regions of the city. Sera were analyzed using Ag-B ELISA test. Ten μg/ml antigens, serum dilutions of 1:500 and conjugate anti-human coombs with 1:10000 dilutions were utilized to perform the test. All subjects filled out a questionnaire and an informed consent. Data analysis was conducted using SPSS 18 software. Cut-off was calculated as X+3 SD.

RESULTS

Cut-off value was calculated 0.19. Seven cases (1.1%) were seropositive for hydatidosis by ELISA test. The sero-prevalence of hydatidosis was 0.27% among females and 2.24% among males (P=0.019). Age group of 60-69 years old, with 2.59% as prevalence had the highest rate of positivity. There was no significant difference as regards age groups, job, residency, contact by dog and literacy. According to job, self-employed people had the highest rate of infection as 3.05%. The sero-prevalence of infection was 1.14% in diploma and 1.13% in illiterates. As regards residency, urban life (1.49%) showed no significant difference with rural life.

CONCLUSION

The rate of prevalence in this region showed that necessary cautions should be taken into account to monitor the spread of human hydatidosis in this region. In comparison with other studies, the rate of infection was roughly less than other regions.

Seroprevalence of leptospiral infection in feline population in urban and dairy cattle herds in Mashhad, Iran

The importance of cats in the Leptospira epidemiology is due to the possibility of transferring leptospirosis to wild and domesticated animals. The purpose of this survey was to determine the prevalence of Leptospira infection in shorthair cats in different location of Mashhad, Iran. Totally, 147 blood samples were taken from 42 (28.57%), 52 (35.37%) and 53 (36.05%) households, stray and cats which lived in industrial dairy cattle herds of Mashhad, Iran, respectively. Sera were tested with seven live Leptospira antigens using microscopic agglutination test (MAT). Sera with 50.00% agglutination at the dilution of ≥ 1/100 were considered as positive samples. Agglutination at dilutions of < 1/100 considered as suspected to Leptospira infection. Overall, 19 (12.92%) out of 147 cats showed reaction in MAT. The seroprevalence at a titer ≥ 1:100 and < 1:100 were 10 (6.80%) and 9 (6.12%), respectively. Serum samples showed positive reaction against Leptospira intterogans hardjo (no = 10; 52.63%), pomona (no = 5; 26.31%) and icterohaemorrhagiae (no = 4; 21.05%). Eight cats (42.10%) belong to dairy cattle herds had the most infection only by L. I. hardjo with 1:200 titer. There were no significant differences among the weight' age and sex of infected cats. However, there were significant differences between the infected cats in dairy cattle herds and the cats in the urban area (p < 0.05). It is concluded that cats can be infected by Leptospira spp. especially in commercial dairy cattle herds. Cats can be considered as a sanitation hazards in the area for this zoonotic disease.

Sero-epidemiology and risk factors for Toxoplasma gondii among pregnant women in Arab and African countries

The epidemiology of toxoplasmosis in pregnancy is a major issue for public health. Primary infection in pregnant women can lead to serious sequelae. This review examined current sero-epidemiology and risks factor data for Toxoplasma gondii in pregnant women in Arab and African countries. A systematic electronic search of published literature was conducted. Data were extracted from relevant studies. Seropositivity is high in both regions. African countries have higher seropositivity than Arab countries due to differences in risk factors. Data on T. gondii infection in pregnancy are scant in many countries, especially where there is lack of political stability. Identified risk factors included eating raw meat, proximity with cats, undercooked food, and increasing maternal age. Toxoplasmosis in pregnancy in Arab and African countries is an underestimated health problem. Further research is needed. This report is a foundation for strategies and policies for intervention needed to combat the consequences of congenital toxoplasmosis.

Association between antibodies to multiple infectious and food antigens and new onset schizophrenia among US military personnel

INTRODUCTION

Multiple studies have documented immune activation in many individuals with schizophrenia suggesting that antigens capable of generating a prolonged immune response may be important environmental factors in many cases of this disorder. While existing studies have found single-agent associations of antibodies to food and neurotropic infectious agents with schizophrenia, a simultaneous examination of multiple agents may shed light on agent interactions or possible etiopathogenic pathways.

METHODS

We used traditional regression and novel statistical techniques to examine associations of single and combined infectious and food antigens with schizophrenia. We tested 6106 serum samples from 855 cases and 1165 matched controls.

RESULTS

Higher antibody levels to casein were borderline significant in the prediction of schizophrenia (HR=1.08, p=0.06). Study participants with higher cytomegalovirus (CMV) IgG antibody levels had a reduced risk of developing schizophrenia (HR=0.90; p=0.02). While IgG antibodies to gliadin, Toxoplasma gondii, vaccinia, measles, and human herpesvirus-6 (HHV-6) showed no significant independent associations with schizophrenia, the increase in antibody levels to several combinations of agents, to include casein, measles, CMV, T. gondii and vaccinia, was predictive of an 18-34% increase in the risk of developing schizophrenia.

CONCLUSION

Certain patterns of antibodies, involving some agents, were predictive of developing schizophrenia, with the magnitude of association rising when the level of antibodies increased to two or more agents. A heightened antibody response to a combination of several infectious/food antigens might be an indicator of an altered immune response to antigenic stimuli.

Serological and molecular study of hepatitis E virus among illegal blood donors

AIM: To investigate the seroprevalence and molecular characteristics of hepatitis E virus (HEV) in the illegal blood donors (IBDs) of central China in the early 1990s.

METHODS: A total of 546 blood samples were collected from the IBDs in Maanshan city, a questionnaire was completed by each subject, detailing the age, sex, and periods of blood or plasma donation. Anhui Province and tested for the anti-HEV antibodies. The seropositive samples were subjected to nested reverse transcription-polymerase chain reaction and sequencing to analyze HEV partial genome.

RESULTS: The prevalence of IgG and IgM HEV antibody in IBDs was 22.7% and 1.8%, and genotype 4 was the dominant circulating HEV type in IBDs. The prevalence of anti-HEV IgG was significantly related to sex (OR = 4.905, P = 0.004) and increased with age (OR = 2.78, P = 0.022), which ranged from 13.0% in those < 40 years old to 30.6% among older persons aged > 60 years. Moreover, frequency of blood donation was significantly associated with HEV seropositivity (OR = 2.06, P = 0.006). HEV partial sequences of ORF2 and obtained 3 sequences in serum samples of 10 IBDs which developed HEV specific IgM.

CONCLUSION: This study helps define one of the possible routes of transmission of sporadic HEV infection and provides guidance to screen HEV in the blood donors so as to guarantee safe blood banks in China.

Epidemiological aspects of visceral leishmaniasis in baft district, kerman province, southeast of iran

BACKGROUND

Visceral leishmaniasis (kala-azar) is an endemic disease in some areas of Iran. A cross- sectional study was conducted for sero-epidemiological survey of visceral leishmaniasis (VL) in Baft district from Kerman Province, southeast of Iran.

METHODS

Blood samples were collected from children up to 12 years old and 10% of adult population from Baft villages with a multi-stage randomized cluster sampling. In addition, blood samples were collected from 30 domestic dogs from the same areas. All the collected blood samples were tested by direct agglutination test (DAT) for the detection of anti-Leishmania antibodies in both human and dog using the cut-off value of ≥1:3200 and ≥1:320, respectively. Parasitological, molecular, and pathological were performed on infected dogs. Chi-square and Fisher exact tests were used to compare sero-prevalence values.

RESULTS

From 1476 collected human serum samples, 23 (1.55%) showed anti-Leishmania antibodies at titers of 1:800 and 1:1600 whereas 14 (0.95%) showed anti-Leishmania infantum antibodies at titers of ≥1:3200. No statistically significant difference was found between male (1.18%) and female (0.69%) sero-prevalence (P=0.330). Children of 5-8 years showed the highest sero-prevalence rate (3.22%). Seven out of 30 domestic dogs (23%) showed anti-Leishmania antibodies at titers ≥1:320. Leishmania infantum was identified in five infected dogs by nested - PCR assay.

CONCLUSION

It seems that visceral leishmaniasis is being endemic in southern villages of Baft district, southeast of Iran.

Epidemiology and transmission of hepatitis B and C viruses in Kazakhstan

AIM: To investigate the epidemiology of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in the two major ethnic groups in Kazakhstan.

METHODS: A cross-sectional prospective study of HBV and HCV seroprevalence was performed among individuals born in Kazakhstan with no history of chronic hepatitis or liver disease.

RESULTS: There were 290 volunteers (140 Russians and 150 Kazakhs) aged 10 to 64 years, males accounted for 46%. Active HBV infection (HBsAg positive) was present in 3.8%, anti-HBc in 30%. The prevalence was similar in females and males (33% vs 25%) (P = 0.18). The prevalence of anti-HBc increased from 19% in 10-29 years old volunteers to 53% in 50-years and older volunteers. The prevalence of HBV infection was higher in married than in single adults (38% vs 26%, respectively) (P = 0.2) and more common in Kazakhs (35%) than in Russians (24%) (P = 0.07). HCV infection was present in 9 subjects (3.2%), 5 of them also were positive for anti-HBc in the absence of HBsAg.

CONCLUSION: The frequency of active HBV infection (3.8%) coupled with a high prevalence of HBV exposure in those > 50 years of age increases with age, which suggests that horizontal transmission likely relates to the use of contaminated needles. The low prevalence of HCV infection suggests that HBV and HCV are acquired differently in this group of subjects.