A Spatial Analysis of Rift Valley Fever Virus Seropositivity in Domestic Ruminants in Tanzania

Rift Valley fever (RVF) is an acute arthropod-borne viral zoonotic disease primarily occurring in Africa. Since RVF-like disease was reported in Tanzania in 1930, outbreaks of the disease have been reported mainly from the eastern ecosystem of the Great Rift Valley. This cross-sectional study was carried out to describe the variation in RVF virus (RVFV) seropositivity in domestic ruminants between selected villages in the eastern and western Rift Valley ecosystems in Tanzania, and identify potential risk factors. Three study villages were purposively selected from each of the two Rift Valley ecosystems. Serum samples from randomly selected domestic ruminants (n = 1,435) were tested for the presence of specific immunoglobulin G (IgG) and M (IgM), using RVF enzyme-linked immunosorbent assay methods. Mixed effects logistic regression modelling was used to investigate the association between potential risk factors and RVFV seropositivity. The overall RVFV seroprevalence (n = 1,435) in domestic ruminants was 25.8% and species specific seroprevalence was 29.7%, 27.7% and 22.0% in sheep (n = 148), cattle (n = 756) and goats (n = 531), respectively. The odds of seropositivity were significantly higher in animals sampled from the villages in the eastern than those in the western Rift Valley ecosystem (OR = 1.88, CI: 1.41, 2.51; p<0.001), in animals sampled from villages with soils of good than those with soils of poor water holding capacity (OR = 1.97; 95% CI: 1.58, 3.02; p< 0.001), and in animals which had been introduced than in animals born within the herd (OR = 5.08, CI: 2.74, 9.44; p< 0.001). Compared with animals aged 1-2 years, those aged 3 and 4-5 years had 3.40 (CI: 2.49, 4.64; p< 0.001) and 3.31 (CI: 2.27, 4.82, p< 0.001) times the odds of seropositivity. The findings confirm exposure to RVFV in all the study villages, but with a higher prevalence in the study villages from the eastern Rift Valley ecosystem

Demographic and Behavioural Factors in Tanzanian and Norwegian Patients with Sexually Transmitted Infections.

To evaluate whether differences in demographic or behavioural factors might explain differences in reported or diagnosed sexually transmitted infections (STI), we have compared data from 1097 Tanzanian and Norwegian STI patients. Most demographic data were similar, whereas some behavioural data differed. Norwegian patients reported significantly higher numbers of sexual partners than Tanzanian. Thirty-three percent of Tanzanian patients tested positive for HIV antibodies, females more often (43%) than males (26%). Approximately one-third and two-thirds of the female HIV-positive Tanzanian STI patients had already seroconverted at the age of 25 and 30 years, respectively. The national differences encountered probably reflect cultural differences, different panoramas of STI and a lower accessibility to optimal health services in Tanzania. Lack of expected statistical associations between some of the data in the Tanzanian STI group might question the validity of the retrospectively collected data in this group, or indicate that questions not included in the questionnaire might be of importance

Exploring H.pylori seropositivity as a risk factor for type 2 diabetes

Background: In the US, the percentage of adults with diagnosed diabetes are higher in members of racial and ethnic minority groups compared to non-Latino Whites. Understanding why such disparities exist has been less forthcoming. Methods: Secondary data analysis was conducted using the National Health and Nutrition Examination Survey (NHANES) 1999-2000 cross-sectional data. Results: H.pylori seropositivity was highest in Mexican Americans (43.7%), lowest in non-Hispanic Whites (18.1%). Diabetes was highest in non-Hispanic Blacks (5.9%); lowest in non-Hispanic whites (4.3%). H.pylori seropositivity was associated with greater likelihood of having type 2 diabetes (1.927, 95% CI 1.142, 3.257) compared to H.pylori negative in unadjusted model. After adjustment, H.pylori seropositivity was no longer associated with diabetes. Obesity (aOR 4.94, 95% CI 2.672,9.133) was associated with having type 2 diabetes compared to normal weight. Non-Hispanic Blacks (2.436, 95% CI 1.489,3.984) and Mexican Americans (1.896, 95% CI 1.002,3.587) had greater odds of diabetes compared to Whites. For nearly all stratified analyses, H.pylori did not have a significant association with type 2 diabetes although several other noteworthy findings emerged. A chance finding, where H.pylori was associated with greater likelihood of diabetes in Mexican Americans, 60-85, \u3e25 BMI, may be worth a closer look. Conclusion: Findings indicate weight status, obesity in particular, is the strongest predictor of diabetes followed by Black race. Stratified analyses suggest increasing racial disparities over the course of the life span

Porcine reproductive and respiratory syndrome virus (PRRSV) in GB pig herds : farm characteristics associated with heterogeneity in seroprevalence

Background: The between- and within-herd variability of porcine reproductive and respiratory syndrome virus (PRRSV) antibodies were investigated in a cross-sectional study of 103 British pig herds conducted 2003–2004. Fifty pigs from each farm were tested for anti-PRRSV antibodies using ELISA. A binomial logistic model was used to investigate management risks for farms with and without pigs with PRRSV antibodies and multilevel statistical models were used to investigate variability in pigs' log ELISA IRPC (relative index × 100) in positive herds. Results: Thirty-five herds (34.0%) were seronegative, 41 (39.8%) were seropositive and 27 (26.2%) were vaccinated. Herds were more likely to be seronegative if they had < 250 sows (OR 3.86 (95% CI 1.46, 10.19)) and if the nearest pig herd was ≥ 2 miles away (OR 3.42 (95% CI 1.29, 9.12)). The mean log IRPC in seropositive herds was 3.02 (range, 0.83 – 5.58). Sixteen seropositive herds had only seropositive adult pigs. In these herds, pigs had -0.06 (95% CI -0.10, -0.01) lower log IRPC for every mile increase in distance to the nearest pig unit, and -0.56 (95% CI -1.02, -0.10) lower log IRPC when quarantine facilities were present. For 25 herds with seropositive young stock and adults, lower log IRPC were associated with isolating purchased stock for ≥ 6 days (coefficient - 0.46, 95% CI -0.81, -0.11), requesting ≥ 48 hours 'pig-free time' from humans (coefficient -0.44, 95% CI -0.79, -0.10) and purchasing gilts (coefficient -0.61, 95% CI -0.92, -0.29). Conclusion: These patterns are consistent with PRRSV failing to persist indefinitely on some infected farms, with fadeout more likely in smaller herds with little/no reintroduction of infectious stock. Persistence of infection may be associated with large herds in pig-dense regions with repeated reintroduction

Enteropathogen antibody dynamics and force of infection among children in low-resource settings.

Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG responses to eight enteropathogens (Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica, enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni, norovirus) in cohorts from Haiti, Kenya, and Tanzania. We studied antibody dynamics and force of infection across pathogens and cohorts. Enteropathogens shared common seroepidemiologic features that enabled between-pathogen comparisons of transmission. Overall, exposure was intense: for most pathogens the window of primary infection was &lt;3 years old; for highest transmission pathogens primary infection occurred within the first year. Longitudinal profiles demonstrated significant IgG boosting and waning above seropositivity cutoffs, underscoring the value of longitudinal designs to estimate force of infection. Seroprevalence and force of infection were rank-preserving across pathogens, illustrating the measures provide similar information about transmission heterogeneity. Our findings suggest antibody response can be used to measure population-level transmission of diverse enteropathogens in serologic surveillance

Risk factors for human acute leptospirosis in northern Tanzania

Introduction: Leptospirosis is a major cause of febrile illness in Africa but little is known about risk factors for human infection. We conducted a cross-sectional study to investigate risk factors for acute leptospirosis and Leptospira seropositivity among patients with fever attending referral hospitals in northern Tanzania. Methods: We enrolled patients with fever from two referral hospitals in Moshi, Tanzania, 2012–2014, and performed Leptospira microscopic agglutination testing on acute and convalescent serum. Cases of acute leptospirosis were participants with a four-fold rise in antibody titers, or a single reciprocal titer ≥800. Seropositive participants required a single titer ≥100, and controls had titers &#60;100 in both acute and convalescent samples. We administered a questionnaire to assess risk behaviors over the preceding 30 days. We created cumulative scales of exposure to livestock urine, rodents, and surface water, and calculated odds ratios (OR) for individual behaviors and for cumulative exposure variables. Results: We identified 24 acute cases, 252 seropositive participants, and 592 controls. Rice farming (OR 14.6), cleaning cattle waste (OR 4.3), feeding cattle (OR 3.9), farm work (OR 3.3), and an increasing cattle urine exposure score (OR 1.2 per point) were associated with acute leptospirosis. Conclusions: In our population, exposure to cattle and rice farming were risk factors for acute leptospirosis. Although further data is needed, these results suggest that cattle may be an important source of human leptospirosis. Further investigation is needed to explore the potential for control of livestock Leptospira infection to reduce human disease

Longitudinal Monitoring of SARS-CoV-2 IgM and IgG Seropositivity to Detect COVID-19.

BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a novel beta-coronavirus that has recently emerged as the cause of the 2019 coronavirus pandemic (COVID-19). Polymerase chain reaction (PCR) based tests are optimal and recommended for the diagnosis of an acute SARS-CoV-2 infection. Serology tests for viral antibodies provide an important tool to diagnose previous exposure to the virus. Here we evaluate the analytical performance parameters of the Diazyme SARS-CoV-2 IgM/IgG serology assays and describe the kinetics of IgM and IgG seroconversion observed in patients with PCR-confirmed COVID-19 who were admitted to our hospital.MethodsWe validated the performance of the Diazyme assay in 235 presumed SARS-CoV-2 negative subjects to determine specificity. Subsequently, we evaluated the SARS-CoV-2 IgM and IgG seroconversion of 54 PCR-confirmed COVID-19 patients and determined sensitivity of the assay at three different timeframes.ResultSensitivity and specificity for detecting seropositivity at ≥15 days following a positive SARS-CoV-2 PCR result, was 100.0% and 98.7% when assaying for the panel of IgM and IgG. The median time to seropositivity observed for a reactive IgM and IgG result from the date of a positive PCR was 5 days (IQR: 2.75-9 days) and 4 days (IQR: 2.75-6.75 days), respectively.ConclusionsOur data demonstrate that the Diazyme IgM/IgG assays are suited for the purpose of detecting SARS-CoV-2 IgG and IgM in patients with suspected SARS-CoV-2 infections. For the first time, we report longitudinal data showing the evolution of seroconversion for both IgG and IgM in a cohort of acutely ill patients in the United States. We also demonstrate a low false positive rate in patients who were presumed to be disease free

Historical Patterns of Arboviral Seroprevalence across Africa and Asia

The emergence and resurgence of arboviruses in recent history is challenging our scientific understanding of mosquito-borne diseases and their transmission. To better contextualize recent epidemics and gain insight into historical trends in arbovirus incidence, we conducted a literature review to identify serosurveys from Africa and Asia. We compiled all serosurvey data into a table and tested for variation in disease incidence across countries and between age categories. Our analysis showed that disease incidence was consistently higher in the \u3e15 age category than the \u3c15 age category and revealed significant variation in incidence across countries. In addition, the mean incidence of yellow fever virus was substantially higher than the incidences of the other diseases included in the analysis. Higher incidence in the \u3e15 age category is likely due to the long-term persistence of antibodies in human sera, while a higher incidence of yellow fever can likely be attributed to widespread vaccine use. Characteristics of countries with high disease incidence included a tropical climate, extended rainy season, and flat terrain, and countries with low disease incidence occurred at higher elevations and/or reflected a desert climate. This analysis can hopefully reveal the conditions most important in facilitating an arbovirus outbreak, leading to targeted prevention strategies in high-risk areas. It also highlights the need for continued serosurveys as a method of documenting disease spread

Wastewater workers and hepatitis A virus infection.

The main occupational hazard of wastewater workers (WWs) is the direct exposure to the variety of infectious agents present in sewage material, with hepatitis A virus (HAV) being the most frequent one. Most epidemiological studies have shown a higher risk of hepatitis A among WWs, although some studies have produced conflicting evidence. To evaluate the hypothesis of increased risk of HAV infection in WWs. The prevalence of antibodies toHAV in 869WWswas compared to 311 other subjects and analysed to detect the main potentially confounding variables. Univariate analysis demonstrated that occupational exposure to sewage was not significantly associated with the prevalence of anti-HAV(1). The anti-HAV(1) prevalence was strongly associated with age and shellfish consumption (P,0.05) when the subcategories of workers were examined separately (WWs and control group) and jointly. In the logistic regression model, a significant association between anti-HAV(1) prevalence and duration of employment (P,0.05) was found. The interaction term(age3duration of employment) was significant (P,0.001) when included in the logistic model. This study shows that working in a wastewater treatment plant does not seem to be related to a greater prevalence of antibodies to hepatitis A. Moreover, the relative risk of HAV infection among WWs seems to be correlated with low anti-HAV(1) prevalence in the general population

Effect of pig production system and transport on the potential pathogen transfer risk into the food chain from Salmonella shed in pig faeces

The prevalence of faecal Salmonella shedding has been compared in organic, conventional outdoor, and indoor finishing pig herds in a Danish survey with participation of 34 herds. Individual faecal and meat juice samples were collected from 30-50 pigs per herd and analysed for presence of Salmonella, and Salmonella antibodies, respectively. The results showed a low level of on-farm Salmonella shedding (<0,2 %) in organic and conventional outdoor herds compared to 2,5 % in indoor pigs (P<0,0001), and also a lower prevalence of Salmonella shedding in outdoor systems at slaughter (<2 %) compared to 4,1 % in indoor systems (P<0,01). The overall seroprevalence was 8,5 % with no significant differences between systems. Seropositivity was a significant predictor of Salmonella shedding at slaughter in individual pigs from conventional systems, but not in organic pigs. The duration of transport did not affect the risk of Salmonella shedding at slaughter