Size at Maturity and Fecundity of Oreochromis niloticus and Mouth Brooding Tilapiines Indigenous to Kafue Flood Plain Fishery, Zambia.

The present investigation was conducted to ascertain whether or not Size at maturity, Fecundity, and Total Length-Fecundity variation could explain the population dominance of Oreochromis niloticus (Linnaeus 1758) over three spot breams Oreochromis andersonii (Castelnau 1861) and Green-Headed Bream Oreochromis macrochir (Boulenger 1912) in the Kafue Flood Plain during the spawning season (October 2020 to March 2021). Fish samples caught using a full standard multifilament net with mesh sizes ranging from 25 to 150 mm increments of 12.5 mm were purchased from Local Fishermen at Chanyanya and Kasaka fishing camps. The Total length of each fish was recorded to the nearest 0.1 cm using the fish measuring board. Reproductive stages of the three Tilapiine fish species were determined using standard keys. Whole ovaries from sexually mature females (ripe) were weighed and preserved in 10% formalin solution; logistic regression lines were used to determine size at maturity (L50). Fecundity was determined using gravimetric procedures. The O. andersonii matured at a Total length of 210.98 mm, O. macrochir at 199.48 mm, while O. niloticus matured at 189.82 mm. The O andersonii had mean Fecundity of 1843.92 ± 68.805; O. macrochir had 1640.82 ± 92.164 while O. niloticus had 1422.24 ± 91.103. The relationship between Fecundity and Total length was found to be strongest in O. macrochir (y=12.845x-1175; r=0.8770), followed by O. niloticus (y = 12.912x – 1614.3; r=0.8104) and finally O. andersonii (y=10.715x-591.91; r=0.7606). The studied characteristics among the Tilapiines indicated that O. niloticus was superior in reproductive biology. There should be proper guidelines in the laws and regulations regarding the introduction of O. niloticus into other water bodies. The O. niloticus must be promoted in aquaculture because of its reproductive advantages compared to the local Tilapiines

Investigation of Methods and Motives for Water Theft in A Suburb Township

Theft of water from water urban authorities is fast growing to a level of severe concern with the perpetrators moving several steps ahead of water utility companies. Consequently, counter-measures that are in tandem with the ever-changing business environment are greatly desired to empower water utility companies with effective methods to prevent the ever-growing water theft challenges.  To ascertain the significance of the methods used to steal water, a study was undertaken in one of the suburbs of Blantyre in Malawi. A questionnaire survey was employed to elicit data on the methods used for stealing water and the motivations behind the thefts.  The results indicated that the most prevalent method for stealing water was bursting pipes followed by vandalizing. Poor service was the most compelling reason behind water theft from the water utility company. The severity indices for the constructs used to steal water in this study can be used to design intervention frameworks for water utility companies. Additionally, iso-theft-index maps can be produced for suburb areas where water utility companies have water distribution networks to guide surveillance operations. Keywords: water theft methods, non-revenue water, challenges, Malawi DOI: 10.7176/JEES/12-8-04 Publication date:August 31st 202

Development and Characterization of a Luminescence-Based High-Throughput Serum Bactericidal Assay (L-SBA) to Assess Bactericidal Activity of Human Sera against Nontyphoidal Salmonella

Salmonella Typhimurium and Salmonella Enteritidis are leading causative agents of invasive nontyphoidal Salmonella (iNTS) disease, which represents one of the major causes of death and morbidity in sub-Saharan Africa, still partially underestimated. Large sero-epidemiological studies are necessary to unravel the burden of disease and guide the introduction of vaccines that are not yet available. Even if no correlate of protection has been determined so far for iNTS, the evaluation of complement-mediated functionality of antibodies generated towards natural infection or elicited upon vaccination may represent a big step towards this achievement. Here we present the setup and the intra-laboratory characterization in terms of repeatability, intermediate precision, linearity, and specificity of a high-throughput luminescence-based serum bactericidal assay (L-SBA). This method could be useful to perform sero-epidemiological studies across iNTS endemic countries and for evaluation of antibodies raised against iNTS vaccine candidates in upcoming clinical trials

Understanding the epidemiology of iNTS disease in Africa in preparation for future iNTS- vaccine studies in endemic countries: Seroepidemiology in Africa of iNTS (SAiNTS) Study Protocol [Version 9.0]

Background: Non-typhoidal Salmonella (NTS) are a major cause of bloodstream infections amongst children in sub-Saharan Africa. A clear understanding of the seroepidemiology and correlates of protection for invasive NTS (iNTS) in relation to key risk factors (malaria, anaemia, malnutrition) in children in Africa is needed to inform strategies for disease control including vaccine implementation. Method: ology:  The SAiNTS study is a prospective community cohort study with paired serology samples from 2500 children 0-5 years at baseline and three months to measure age-stratified acquisition of lipopolysaccharide (LPS) O-antigen antibody (IgG) and serum bactericidal activity to the main serovars causing iNTS ( Salmonella typhimurium and S. enteritidis ). Children are selected from mapped and censused randomly selected households in Chikwawa, Malawi; an area with substantial malaria burden. The sampling framework is set within a malaria vaccination (RTS,S/ AS01) phase 4 cluster randomized trial (EPIMAL), allowing exploration of the impact of malaria vaccination on acquisition of immunity to NTS. Data on risk factors for invasive disease: malaria, anaemia and malnutrition as well as indicators of socioeconomic status and water and sanitation, will be collected using rapid diagnostic tests, anthropometry and electronic CRF’s. Stool sample analysis includes NTS culture and pan-Salmonella polymerase chain reaction to assess enteric exposure and biomarkers of environmental enteric dysfunction. Cases with iNTS disease will be followed up for comparison with community controls. Conclusions: :  The final cohort of 2500 children will allow investigation into the impact of risk factors for iNTS on the acquisition of immunity in children 0-5 years in an endemic setting, including comparisons to partner sero-epidemiology studies in three other sub-Saharan African sites. The data generated will be key to informing iNTS disease control measures including targeted risk factor interventions and vaccine implementation through investigation of correlates of protection and identifying windows of immune susceptibility in at-risk populations

High SARS-CoV-2 seroprevalence in health care workers but relatively low numbers of deaths in urban Malawi

Background: In low-income countries, like Malawi, important public health measures including social distancing or a lockdown have been challenging to implement owing to socioeconomic constraints, leading to predictions that the COVID-19 pandemic would progress rapidly. However, due to limited capacity to test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, there are no reliable estimates of the true burden of infection and death.  We, therefore, conducted a SARS-CoV-2 serosurvey amongst health care workers (HCWs) in Blantyre city to estimate the cumulative incidence of SARS-CoV-2 infection in urban Malawi. Methods: We recruited 500 otherwise asymptomatic HCWs from Blantyre City (Malawi) from 22 nd May 2020 to 19 th June 2020 and serum samples were collected from all participants. A commercial ELISA was used to measure SARS-CoV-2 IgG antibodies in serum. Results: A total of 84 participants tested positive for SARS-CoV-2 antibodies. The HCWs with positive SARS-CoV-2 antibody results came from different parts of the city. The adjusted seroprevalence of SARS-CoV-2 antibodies was 12.3% [CI 8.2 - 16.5]. Using age-stratified infection fatality estimates reported from elsewhere, we found that at the observed adjusted seroprevalence, the number of predicted deaths was eight times the number of reported deaths. Conclusions: The high seroprevalence of SARS-CoV-2 antibodies among HCWs and the discrepancy in the predicted versus reported deaths suggests that there was early exposure but slow progression of COVID-19 epidemic in urban Malawi. This highlights the urgent need for development of locally parameterised mathematical models to more accurately predict the trajectory of the epidemic in sub-Saharan Africa for better evidence-based policy decisions and public health response planning

Characterization of Enzyme-Linked Immunosorbent Assay (ELISA) for Quantification of Antibodies against <i>Salmonella</i> Typhimurium and <i>Salmonella</i> Enteritidis O-Antigens in Human Sera

Nontyphoidal Salmonella (NTS) is a leading cause of morbidity and mortality caused by enteric pathogens worldwide in both children and adults, and vaccines are not yet available. The measurement of antigen-specific antibodies in the sera of vaccinated or convalescent individuals is crucial to understand the incidence of disease and the immunogenicity of vaccine candidates. A solid and standardized assay used to determine the level of specific anti-antigens IgG is therefore of paramount importance. In this work, we presented the characterization of a customized enzyme-linked immunosorbent assay (ELISA) with continuous readouts and a standardized definition of EU/mL. We assessed various performance parameters: standard curve accuracy, dilutional linearity, intermediate precision, specificity, limits of blanks, and quantification. The simplicity of the assay, its high sensitivity and specificity coupled with its low cost and the use of basic consumables and instruments without the need of high automation makes it suitable for transfer and application to different laboratories, including resource-limiting settings where the disease is endemic. This ELISA is, therefore, fit for purpose to be used for quantification of antibodies against Salmonella Typhimurium and Salmonella Enteritidis O-antigens in human samples, both for vaccine clinical trials and large sero-epidemiological studies