Residual blood specimens collected at health care facilities provide a low-cost and readily available specimen source to monitor population immunity through serological surveillance compared to more resource-intensive probability-based surveys. Despite concerns about the representativeness of these specimens, there has recently been increased interest in the use of residual specimens, driven by the need for rapid estimates of seroprevalence during outbreaks to inform response and prevention. Although residual specimen collection is a key component of surveillance systems in some settings, there is limited evidence of its implementation in low-and middle-income countries. We conducted a pilot project at three health facilities in two districts in Zambia between September 2021 through July 2022 to demonstrate the feasibility of residual blood specimen collection integrated into the health system to estimate measles seroprevalence. Through this pilot project, we were able to collect residual pediatric and adult specimens but with some modifications needed if residual specimen collection were to be implemented at scale, such as better integration into the routine functioning of laboratories and health facilities. This paper summarizes our experiences designing and implementing this residual blood specimen collection, including the lessons learned and recommendations for collecting residual specimens from hospitals.
The biodiversity of mosquito taxa beyond Anopheles malaria vectors has been understudied in many parts of Africa. Here, we provide a new species record of mosquitoes from Macha and its surrounding locations in southern Zambia, as well as an updated list of species from the region. With the addition of 19 new species records in this region, the total list of mosquito species reported in Macha is now 46. We present high-resolution focus-stacked photographs of some of these species, many of which were only previously available as text or drawing descriptions in mosquito identification books and articles. We also include 34 COI sequences from Zambian mosquito species, five of which had no prior genetic information on Genbank. This visual guide as well as additional COI sequences provide essential tools for accurate mosquito surveillance in southern Zambia and establishes a baseline data for future invasive species monitoring.
Increasing artemisinin partial resistance (ART-R) due to mutations in the gene encoding Kelch13 (Pfk13) protein in eastern Africa is of urgent concern, and mutations, such as Pfk13 P441L, continue to emerge. We used an amplicon deep-sequencing panel to estimate the prevalence of validated and candidate ART-R Pfk13 mutations in samples collected between 2018 and 2023 in southern Zambia. Pfk13 P441L was present in 30 of 501 samples (6%), and prevalence increased over time (0% to 7.2%). Further studies of the P441L mutation are needed to document its geographical origin, distribution and impact on treatment outcomes.
Eleven countries have been certified as malaria free since 2016, but none of these are in subSaharan Africa where elimination challenges are unique. The 1-3-7 focus investigation approach is an implementation strategy that requires case reporting, case investigation/classification, and focal classification/response to be completed one, three, and seven days, respectively, after index case diagnosis. Real-time short-messaging-service reports are sent at each step to add accountability and data transparency. Reactive case detection is one focal response of the 1-3-7 strategy. China, Thailand, Myanmar, and other countries cite high fidelity to deadlines and broad acceptability of 1-3-7, but this strategy has yet to be widely deployed in Africa. This mixed-methods study evaluated implementation and service outcomes of 1-3-7 focus investigation in a rural area of southern Zambia. Selected outcomes were fidelity, efficiency, feasibility, equity, and acceptability, assessed via program metadata and semi-structured interviews with program personnel. Fidelity was moderate with 61% of cases reported. Focus investigation and reactive case detection completion doubled in areas using 1-3-7, from 20% to 42%. However, reactive case detection, which involved screening community members residing within 140 meter of index cases with a rapid diagnostic test, detected few parasitemic individuals, suggesting this may not be the most efficient day 7 response in this setting. Mobile phone network coverage was a common challenge to feasibility that likely affected reporting rates and fidelity. Thirty-four percent of health-facility diagnosed cases were not eligible for 1-3-7 follow-up. Distance from the health center was a barrier to feasibility and equitable reach of services. Reporting was faster in areas where health workers classified transmission as higher and slower in areas with poor mobile phone network coverage. The strategy was widely accepted. Scale-up should include adherence-focused management strategies, spatially targeted interventions not reliant on RDTs, and complementary surveillance that targets hard-to-reach populations.
Post-campaign coverage surveys estimate the proportion of previously unvaccinated children vaccinated during supplementary immunization activities (SIA) but cannot address whether susceptible children seronegative to measles and rubella viruses were vaccinated during the SIA. We conducted a cross-sectional serosurvey nested within the November 2020 measles-rubella SIA in Zambia, systematically sampling children aged 9 months to 5 years at 30 SIA sites in Choma and Ndola Districts. A questionnaire administered to caregivers collected the child's demographic information and vaccination history. Dried blood spot specimens were collected from child participants and for Immunoglobulin-G antibodies to measles and rubella viruses by enzyme immunoassay. We used the expected vaccination probability by age derived from Demographic and Health Surveys to quantify the value of the immunization campaign, estimating the proportion of children who would not have otherwise received routine MR doses. Among children enrolled with MR vaccination data (N = 2,364), 2,214 (94%) reported at least one routine MR dose before the SIA. We estimate 5.0% [95%CI, 4.2-5.9%] (n = 118/2364) of children would not have otherwise received routine MR dose 1 without the SIA and 23.4% [95%CI, 21.7-25.1] (n = 553/2364) would not have otherwise received routine MR dose 2. Thus, 1 in 3.5 doses were given to an MR un- or under-vaccinated child who may not have received that dose in the absence of an SIA. Eighty-six percent and 90% of children were measles and rubella seropositive before vaccination during the SIA. Thirty-six percent of children with no prior routine MR dose were measles seropositive, while nine percent of children with two prior routine MR doses were measles seronegative. Although children vaccinated during this SIA were highly likely to have previously received routine vaccinations, the SIA reached a considerable number of susceptible children. Monitoring SIA effectiveness and efficiency through standardized metrics and formats is critical for impactful vaccine delivery strategies.
