Prevalence Of Submicroscopic Infection Research Articles

Meta-analysis of the prevalence of malaria associated with pregnancy in Colombia 2000-2020.

Knowledge about malaria associated with pregnancy is scarce in Latin America, and in Colombia, little is known about the magnitude of this infection. A systematic review was conducted to determine the prevalence of malaria associated with pregnancy (MAP) and each of its three forms: gestational (GM), placental (PM), and congenital (CM) tested using thick blood smear (TBS) and PCR. Also to compare the proportion of cases due to Plasmodium falciparum and Plasmodium vivax in Colombia from the year 2000–2020. We searched in Pubmed, Science Direct, EMBASE, EMCare, Cochrane Library, Scielo, Lilacs, Google Scholar, libraries, and repositories of Colombian universities, to obtain data on prevalence of GM, PM and CM with their respective testing method. We performed a meta-analysis with a random-effects model to obtain pooled prevalence of MAP and its three forms categorized by testing methods (TBS and PCR). We used data from 14 studies (out of 258 screened) contributing 7932, 2506 women for GM and PM respectively, also data on 1143 umbilical cord blood samples, and 899 peripheral blood of neonates. We found prevalence by TBS as, MAP 4.5% (95%CI = 2.9–6.9), GM 5.8% (95%CI = 3.8–8.7), PM 3.4% (95%CI = 1.7–6.7) and CM 1.3% (95%CI = 0.6–3.0). With PCR the prevalence was, MAP 14.4% (95%CI = 7.6–25.5), GM 16.7% (95%CI = 9.0–28.8), PM 11.0% (95%CI = 4.1–26.3) and CM 16.2% (95%CI = 8.2–29.5). The prevalence of submicroscopic infection was 8.5% (95%CI = 3.4–19.7) in GM, 10.1% (95%CI = 3.5–25.5) in PM and 22.0% (95%CI = 13.2–34.3) in CM. Infections by P. vivax was dominant over P. falciparum when tested with TBS, the PCR test gave similar proportions of P. falciparum and P. vivax. This meta-analysis has demonstrated high prevalence of MAP in Colombia, and highlights the urgent need to increase attention of researchers, research funding institutions, government agencies, and health authorities to study and intervene MAP, that has currently been under investigated.

Seasonal Variation in the Epidemiology of Asymptomatic Plasmodium falciparum Infections across Two Catchment Areas in Bongo District, Ghana.

Understanding the epidemiology of asymptomatic Plasmodium falciparum infections is critical for countries to move toward malaria elimination. Using different methods for parasite detection, we evaluated how seasonality, spatial location, and other factors affect the age-specific epidemiology of asymptomatic malaria in Bongo District, Ghana. Asymptomatic prevalence by microscopy decreased significantly from 42.5% at the end of the wet to 27.5% at the end of the dry season (P < 0.001). Using the 18S rRNA polymerase chain reactions (PCRs), all microscopy-negative samples were screened and prevalence of submicroscopic infections also decreased significantly from the wet (55.4%) to the dry (20.7%) season (P < 0.001). Combining detection methods, 74.4% and 42.5% of the population in the wet and dry seasons, respectively, had evidence of a P. falciparum infection. Interestingly in those > 20 years of age, we found evidence of infection in 64.3% of the population in the wet and 27.0% in the dry season. Using both microscopy and PCR, the asymptomatic P. falciparum reservoir peaks at the end of the wet season and infections in all age groups constitute the reservoir of malaria infection. At the end of the wet season, spatial heterogeneity in the prevalence and density of P. falciparum infections was observed between the two catchment areas surveyed in Bongo District. These results indicate that if elimination is to succeed, interventions will need to target not just P. falciparum infections in children but also in adults, and be implemented toward the end of the dry season in this area of West Africa.

Asymptomatic plasmodial infection in Colombian pregnant women

Information about asymptomatic plasmodial infection is scarce in the world, and the current antimalarial program goals (control, elimination, and eradication) demand this evidence to be well documented in different populations and malaria transmission settings. This study aimed to measure the prevalence of API in Colombian pregnant women at delivery. A retrospective prevalence survey was used. Women were recruited at hospital obstetric facility in each of the municipalities of Turbo, Necoclí in Antioquia department, and Puerto Libertador in Córdoba department. Malaria infection was tested by thick blood smear (TBS) and real-time quantitative PCR (qPCR). Ninety-six pregnant women at delivery were studied: 95% were asymptomatic (91/96), 45% had asymptomatic plasmodial infection (API) by qPCR (41/91), and only 8% (7/91) had API by microscopy. The prevalence of submicroscopic infections (TBS negative and qPCR positive) was very high, 37% (34/91) in asymptomatic women and 41% (39/96) in total women studied (91 asymptomatic and 5 symptomatic). The prevalence of API in Colombian pregnant women is much higher than which is expected for a country that does not have the level of malaria transmission as Sub-Saharan African countries.

Carriage of sub-microscopic sexual and asexual Plasmodium falciparum stages in the dry season at Navrongo, Ghana.

We investigated the prevalence of sub-microscopic Plasmodium falciparum infections and gametocyte carriage in asymptomatic individuals in Navrongo in northern Ghana, an area of seasonal malaria transmission. A cross sectional study of 209 randomly selected participants of all age-groups was conducted in February and March, 2015. Capillary blood samples collected from these individuals were used for the detection of both asexual and gametocyte stage parasites by microscopy, reverse transcriptase polymerase chain reaction (RT-PCR) and conventional nested PCR methods. The prevalence data as determined by microscopy and molecular methods were compared using chi-square tests. Parasitaemia from these asymptomatic infections ranged from 40 to 3,520 parasites/µl of blood (geometric mean parasitaemia = 732 parasites/µl). The prevalence of asymptomatic P. falciparum carriage was 4.8% (10/209) and 13.9% (29/209) using microscopy and RT-PCR respectively. The overall prevalence of sub-microscopic infections in the total number of samples analysed was 9.1% (19/209) and 66% (19/29) of the asymptomatic infections. P. falciparum gametocytemia detected by microscopy was 1% (2/209) and 3.8% (8/209) by PCR. This is the first report of sub-microscopic asexual and gametocytes infections in the dry season in a seasonal malaria transmission area in Ghana. It has established that persistent latent malaria infections occur and that these could supply the source of parasites for the next transmission season. The findings highlight the presence of sub-microscopic infections and therefore the need for active case detection surveillance to eliminate "asymptomatic reservoir" parasites and consequently break the transmission of the disease in Ghana. Bill and Melinda Gates Foundation grant awarded to Noguchi Memorial Institute for Medical Research Postdoctoral and Postgraduate Training in Infectious Diseases Research (Global Health Grant # OPP52155); National Institutes of Health grant (NIH-NIAID RO1 # 1RO1AI099623) to MDW; European Developing Countries Clinical Trials Partnership (EDCTP)-West African Network of Excellence for Clinical Trials in TB, AIDS and Malaria (WANETAM) (Project code CB.07.41700.007).

High prevalence of sub-microscopic infections in Colombia.

BackgroundMalaria transmission in Latin America is typically characterized as hypo-endemic and unstable with ~170 million inhabitants at risk of malaria infection. Although Colombia has witnessed an important decrease in malaria transmission, the disease remains a public health problem with an estimated ~10 million people currently living in areas with malaria risk and ~61,000 cases reported in 2012. This study aimed to establish the malaria prevalence in three endemic regions of Colombia to aid in designing new interventions for malaria elimination.MethodsA cross-sectional survey was conducted in three regions of Colombia with different malaria epidemiological profiles: Tierralta (Ta), Tumaco (Tu) and Buenaventura (Bv). The Annual Parasite Index (API) was 10.7, 6.9 and 3.1, respectively. Participants were asked to respond to a sociodemographic questionnaire and then were bled to determine the Duffy genotype and the prevalence of malaria infection by microscopy and quantitative real-time PCR (qPCR).ResultsThe study was conducted between October 2011 and January 2012. Eight sentinel sites with 1,169 subjects from 267 households were included. The overall prevalence of sub-microscopic infections measured by thick blood smear (TBS) was 0.3% (n = 4) whereas by qPCR it was 9.7% (n = 113), with a greater proportion (13%) in 40-50 years old individuals. Furthermore, different regions displayed different prevalence of sub-microscopic infections: Bv 12%, Ta 15%, and Tu 4%. From these 113 samples (qPCR), 74% were positive for P. vivax and 22% for P. falciparum, and 4% were mixed infections, which correlates to the overall parasite prevalence in Colombia. This study showed that in the southern Pacific coast of Colombia (Bv and Tu), around 56% of the population have a Duffy-negative genotype, compared to the northern region (Ta) where the percentage of Duffy-negative genotype is around 3%.ConclusionsSub-microscopic infections are prevalent across different regions in Colombia, particularly in areas with relatively low transmission intensity. The poor microscopy results suggest the need for more sensitive diagnostic tools for detection of sub-microscopic infections. This study underscores the importance of conducting active case surveillance to more accurately determine malaria incidence, and highlights the need for updating the malaria guidelines to track and treat sub-microscopic malaria infections.

The epidemiology of malaria in adults in a rural area of southern Mozambique

BackgroundEpidemiological studies of malaria in adults who live in malaria endemic areas are scarce. More attention to the natural history of malaria affecting adults is needed to understand the dynamics of malaria infection and its interaction with the immune system. The present study was undertaken to investigate the clinical, parasitological and haematological status of adults exposed to malaria, and to characterize parasites in these individuals who progressively acquire protective immunity.MethodsA cross-sectional survey of 249 adults was conducted in a malaria endemic area of Mozambique. Clinical, parasitological and haematological status of the study population was recorded. Sub-microscopic infections and multiplicity of infections were investigated using polymerase chain reaction (PCR) and restriction fragment length polymorphism of Plasmodium falciparum merozoite surface protein 2 (msp2).ResultsPrevalence of P. falciparum infection by microscopy (14%) and PCR (42%) decreased progressively during adulthood, in parallel with an increase in the prevalence of sub-microscopic infections. Anaemia was only related to parasitaemia as detected by PCR. Multiplicity of infection decreased with age and was higher in subjects with high P. falciparum densities, highlighting density-dependent constraints upon the PCR technique.ConclusionAdults of Manhiça progressively develop non-sterile, protective immunity against P. falciparum malaria. The method of parasite detection has a significant effect on the observed natural history of malaria infections. A more sensitive definition of malaria in adults should be formulated, considering symptoms such as diarrhoea, shivering and headache, combined with the presence of parasitaemia.