Hypoendemic Region Research Articles

The quality of malaria case management in different transmission settings in Tanzania mainland, 2017-2018.

Tanzania is undergoing an epidemiological transition for malaria transmission with some areas of the country having <10% (hypoendemic) and other areas 10% - 50% malaria prevalence (mesoendemic). It is not known whether there is a difference in the quality of malaria case management based on endemicity in Tanzania mainland. We examined the influence of endemicity on the quality of malaria case management at health facilities. We conducted a cross-sectional analysis of 1713 health facilities in Tanzania mainland, using data collected by the National Malaria Control Program through an assessment tool to evaluate quality of malaria case management. The data was gathered from September 2017 to December 2018. Using standard quality factors, mean scores from facilities in the different endemicity regions were compared by a Student's t-test. Simple and multiple linear regression analyses were performed to determine the association between facility performance (score) and endemicity (mesoendemic vs. hypoendemic). Facilities in mesoendemic regions scored higher than those in hypoendemic regions on the overall quality of services [difference in mean scores ([Formula: see text]) = 2.52; (95% Confidence Interval (CI) 1.12, 3.91)], site readiness [[Formula: see text] = 2.97; (95% CI 1.30, 4.61)], availability of malaria reference materials [[Formula: see text] = 4.91; (95% CI 2.05, 7.76)], availability of Health Management Information System tools [[Formula: see text] = 5.86; (95% CI 3.80, 7.92)] and patient satisfaction [[Formula: see text] = 6.61; (95% CI 3.75, 9.48)]. Predictors associated with lower facility scores included; being located in a hypoendemic region [β: -2.49; (95% CI -3.83, -1.15)] and urban area [β: -3.84; (95% CI -5.60, -2.08)]. These findings highlight the differences in quality of malaria case management based on endemicity, but there is still a need to target improvement efforts in underperforming facilities, regardless of endemicity.

The global prevalence of human fascioliasis: a systematic review and meta-analysis.

Fascioliasis is a parasitic zoonosis that can infect humans and be a source of significant morbidity. The World Health Organization lists human fascioliasis as a neglected tropical disease, but the worldwide prevalence of fascioliasis data is unknown. We aimed to estimate the global prevalence of human fascioliasis. We performed a systematic review and prevalence meta-analysis. We used the following inclusion criteria: articles published in the English, Portuguese, or Spanish languages from December 1985 to October 2022 and studies assessing the prevalence of Fasciola in the general population with an appropriate diagnostic methodology, including longitudinal studies, prospective and retrospective cohorts, case series, and randomized clinical trials (RCTs). We excluded animal studies. Two reviewers independently reviewed the selected studies for methodological quality, performing critical standard measures from JBI SUMARI. A random-effects model was conducted of the summary extracted data on the prevalence proportions. We reported the estimates according to the GATHER statement. In all, 5617 studies were screened for eligibility. Fifty-five studies from 15 countries were selected, including 154,697 patients and 3987 cases. The meta-analysis revealed a pooled prevalence of 4.5% [95% confidence interval (CI): 3.1-6.1; I2 = 99.4%; T2 = 0.07]. The prevalence in South America, Africa, and Asia was 9.0%, 4.8%, and 2.0%, respectively. The highest prevalence was found in Bolivia (21%), Peru (11%), and Egypt (6%). Subgroup analysis showed higher prevalence estimates in children, in studies from South America, and when Fas2-enzyme-linked immunosorbent assay (ELISA) was used as a diagnostic method. A larger study sample size (p = 0.027) and an increase in female percentage (p = 0.043) correlated with a decrease in prevalence. Multiple meta-regression showed a higher prevalence for hyperendemic than hypoendemic (p = 0.002) or mesoendemic (p = 0.013) regions. The estimated prevalence and projected disease burden of human fascioliasis are high. Study findings support that fascioliasis continues to be a globally neglected tropical disease. Strengthening epidemiological surveillance and implementing measures to control and treat fascioliasis is imperative in the most affected areas.

Immunoinformatics Design and Assessment of a Multiepitope Antigen (OvMCBL02) for Onchocerciasis Diagnosis and Monitoring.

Onchocerciasis is a Neglected Tropical Disease that has a significant socioeconomic impact, especially in Sub-Saharan Africa. Numerous reports indicate that the Expanded Special Project for the Elimination of Neglected Tropical Diseases needs novel diagnostic tools before achieving its goal of successful elimination of onchocerciasis in Africa. The current diagnostic tests are either invasive, insensitive, or not applicable in the field and about 25% of persons infected cannot mount immune responses against the single antigen used in the only approved Ov-16 serological test. In the quest to identify novel biomarkers that can be used to certify that a patient is free from the disease, evaluate the progress of elimination programmes, and conduct post elimination surveillances, mass spectrometric analysis of Onchocerca volvulus crude extract revealed that 1392 proteins are expressed in the adult and microfilariae stages of the parasite. Computational analysis predicted six of the proteins as O. volvulus potential diagnostic targets. Linear B-epitopes were predicted from the six proteins and used to construct a multiepitope antigen (OvMCBL02). Serological analysis revealed that the OvMCBL02 test significantly differentiated between serum samples of onchocerciasis patients from the Kombone Health Area in the South West Region of Cameroon (n = 63) and control serum samples from Rwanda (n = 29) and Europe (n = 26) as well as between serum samples from the onchocerciasis hyperendemic region of Kombone Health Area (n = 63) and the hypoendemic region of Bandjoun Health District (n = 54). Interestingly, the test did not cross-react with serum samples from patients suffering from related nematode infections, thereby suggesting that further characterization of the OvMCBL02 multiepitope antigen will render it an additional member of the diagnostic toolbox for the elimination of onchocerciasis.

Human and animal cystic echinococcosis in Tataouine governorate: hypoendemic area in a hyperendemic country, myth or reality?

BackgroundCystic echinococcosis (CE) has a worldwide distribution and is especially prevalent in North African countries. With a mean annual surgical incidence (ASI) of CE of 12.7 per 100,000 inhabitants, Tunisia is one of the most CE endemic countries in the Mediterranean area. Tataouine governorate is considered to be the most CE hypoendemic region in Tunisia (ASI = 0.92) despite favourable socioeconomic conditions that enable maintenance of the Echinococcus granulosussensu lato (s.l.) life-cycle and a significant environmental contamination with E. granulosuss.l. eggs. The aim of this study was to assess human CE seroprevalence, prevalence of CE in food animals and environmental contamination by E. granulosus s.l. eggs in different districts of Tataouine governorate.MethodsThis study was conducted from January to December 2018. A total of 374 human sera samples were tested for the presence of immunoglobulin G antibodies against E. granulosus using a commercial ELISA kit. Specimens were also collected from animals slaughtered at the Tataouine abattoir (n = 8609) and examined for the presence of hydatid cysts; 111 hydatid cysts were genotyped. Eggs of E. granulosuss.l. were identified by PCR and DNA sequencing from dog faecal samples (n = 288).ResultsSerological tests showed that 8.5% of the sera samples tested were positive for E. granulosus-specific antibodies. The average prevalence of hydatidosis in livestock was 1.6%, and CE infection was more prevalent in cattle than in sheep, goats and dromedaries. The contamination rate of dog faeces by E. granulosus sensu stricto eggs varied significantly from 0 to 23.5% depending on the collection area. Molecular analyses only revealed the presence of the G1 genotype for cysts and eggs.ConclusionsBased on our findings, CE is likely to be more endemic in the Tataouine governorate than previously described. Thus, to implement an effective control programme against CE, a national survey should be carried out to determine human CE prevalence in the different Tunisian governorates.Graphical

Onchocerciasis Prevalence among Persons with Epilepsy in an Onchocerciasis Hypo-Endemic Area in the Democratic Republic of Congo: A Cross-Sectional Study.

A high epilepsy prevalence has been reported in onchocerciasis meso- and hyper-endemic regions in sub-Saharan Africa, including in the Democratic Republic of Congo (DRC). We investigated whether onchocerciasis-associated epilepsy can also be suspected in onchocerciasis hypo-endemic regions. Stored serum samples from 342 patients admitted with recent onset neurological symptoms admitted to Mosango general hospital, in the Kwilu province, DRC, between 2012 and 2015 were screened for onchocerciasis (OV16) antibodies by ELISA and Taenia solium antigen (using an in-house B158/B60 antigen test). Eighty-one (23.7%; 95% CI 19.5–28.5%) of these samples were positive for OV16 antibodies and 43/340 (12.6%; 95% CI 9.5–16.6%) were positive for T. solium antigen. Of the 58 persons clinically diagnosed with late onset epilepsy of unknown etiology, 19 (32.8%) were OV16 positive and nine (16%) T. solium antigen positive. In total, 16 persons with epilepsy were OV16 positive and T. solium negative, of whom 12 (75%) were between the ages seven to 31 years old, an age rage in which onchocerciasis-associated epilepsy is observed. Our study suggests that in onchocerciasis hypo-endemic areas, in T. solium antigen negative persons with epilepsy, onchocerciasis should be considered as a potential trigger of epilepsy.

A micro-epidemiological report on the unstable transmission of malaria in Aligarh, India

India contributes approximately 70% to the malaria burden of Southeast Asia. The transmission of disease in the country is generally hypoendemic, seasonal and unstable. Most researchers focus upon the hyperendemic malarious regions with stable malaria transmission. There is paucity of data regarding malaria transmission in hypoendemic regions, here we are presenting an epidemiological picture of clinical manifestations through a hospital-based survey in Aligarh, India, during 2016–18. Two thousand sixty-eight patients were diagnosed with malaria infection in Jawaharlal Nehru Medical College and Hospital (JNMCH), out of which 1104 were enrolled for clinical analysis. Ninety per cent of the cases were reported during July–November, and the rest in the dry season. A progressive increase in the prevalence rate was observed during the study period, i.e. 4.8, 7.57 and 8.7% in 2016, 2017 and 2018, respectively. Of the total cases, 75.77% had vivax malaria, while rest suffered from falciparum malaria. The risk of disease was significantly higher in the age group 0–15 years compared to all other age groups (p < .0001). The infection rate was higher in males (61%) compared to females (39%) p < .0001. Overall 8.6% of the patients had severe malaria who fulfilled the WHO criteria. The increasing rate of malaria infection during the study period and a considerable no. of severe vivax malaria cases warrant an efficient disease monitoring system, pointing towards the need to carry out micro-epidemiological studies in order to estimate the real burden of malaria in the country.

Leishmaniasis in Northern Syria during Civil War.

Since the onset of the ongoing civil war in Syria, the governmental surveillance system for leishmaniasis has lost access to provinces of northern Syria. The MENTOR Initiative, an international not-for-profit organization, was commissioned to implement an integrated leishmaniasis control program, providing an opportunity to reassess the epidemiology of leishmaniasis in northern Syria. Epidemiologic data and biologic samples for molecular species diagnostics were collected from collaborating local health centers. Incidence peaked in March 2015 at 7,743 estimated monthly cases. High levels of transmission were observed in traditional endemic regions but extended to previously hypoendemic regions, such as Al-Raqqa and Al-Hasakah. Incidence decreased to 3,209 in July 2015. Data indicate that the prewar trend of increasing incidence of cutaneous leishmaniasis accelerated during the beginning of armed conflict but declined after implementation of the comprehensive control program by the MENTOR Initiative. Molecular analysis revealed a spectrum of Leishmania species and sporadic cases of visceral leishmaniasis.

Vivax infection alters peripheral B-cell profile and induces persistent serum IgM.

B cell-mediated humoral responses are essential for controlling malarial infection. Studies have addressed the effects of Plasmodium falciparum infection on peripheral B-cell subsets but not much is known for P.vivax infection. Furthermore, majority of the studies investigate changes during acute infection, but not after parasite clearance. In this prospective study, we analysed peripheral B-cell profiles and antibody responses during acute P.vivax infection and upon recovery (30days post-treatment) in a low-transmission area in India. Dengue patients were included as febrile-condition controls. Both dengue and malaria patients showed a transient increase in atypical memory B cells during acute infection. However, transient B cell-activating factor (BAFF)-independent increase in the percentage of total and activated immature B cells was observed in malaria patients. Naïve B cells from malaria patients also showed increased TLR4 expression. Total IgM levels remained unchanged during acute infection but increased significantly at recovery. Serum antibody profiling showed a parasite-specific IgM response that persisted at recovery. A persistent IgM autoantibody response was also observed in malaria but not dengue patients. Our data suggest that in hypoendemic regions acute P.vivax infection skews peripheral B-cell subsets and results in a persistent parasite-specific and autoreactive IgM response.

Longitudinal surveillance of drug resistance in Plasmodium falciparum isolates from the China-Myanmar border reveals persistent circulation of multidrug resistant parasites

Multidrug-resistant Plasmodium falciparum in the Greater Mekong Subregion of Southeast Asia is a major threat to malaria elimination and requires close surveillance. In this study, we collected 107 longitudinal clinical samples of P. falciparum in 2007–2012 from the malaria hypoendemic region of the China-Myanmar border and measured their in vitro susceptibilities to 10 antimalarial drugs. Overall, parasites had significantly different IC50 values to all the drugs tested as compared to the reference 3D7 strain. Parasites were also genotyped in seven genes that were associated with drug resistance including pfcrt, pfmdr1, pfmrp1, pfdhfr, pfdhps, pfnhe1, and PfK13 genes. Despite withdrawal of chloroquine and antifolates from treating P. falciparum, parasites remained highly resistant to these drugs and mutations in pfcrt, pfdhfr, and pfdhps genes were highly prevalent and almost reached fixation in the study parasite population. Except for pyronaridine, quinine and lumefantrine, all other tested drugs exhibited significant temporal variations at least between some years, but only chloroquine and piperaquine had a clear temporal trend of continuous increase of IC50s. For the pfmrp1 gene, several mutations were associated with altered sensitivity to a number of drugs tested including chloroquine, piperaquine, lumefantrine and dihydroartemisinin. The association of PfK13 mutations with resistance to multiple drugs suggests potential evolution of PfK13 mutations amid multidrug resistance genetic background. Furthermore, network analysis of drug resistance genes indicated that certain haplotypes associated multidrug resistance persisted in these years, albeit there were year-to-year fluctuations of the predominant haplotypes.

High prevalence of very-low Plasmodium falciparum and Plasmodium vivax parasitaemia carriers in the Peruvian Amazon: insights into local and occupational mobility-related transmission

BackgroundThe incidence of malaria due both to Plasmodium falciparum and Plasmodium vivax in the Peruvian Amazon has risen in the past 5 years. This study tested the hypothesis that the maintenance and emergence of malaria in hypoendemic regions such as Amazonia is determined by submicroscopic and asymptomatic Plasmodium parasitaemia carriers. The present study aimed to precisely quantify the rate of very-low parasitaemia carriers in two sites of the Peruvian Amazon in relation to transmission patterns of P. vivax and P. falciparum in this area.MethodsThis study was carried out within the Amazonian-ICEMR longitudinal cohort. Blood samples were collected for light microscopy diagnosis and packed red blood cell (PRBC) samples were analysed by qPCR. Plasma samples were tested for total IgG reactivity against recombinant PvMSP-10 and PfMSP-10 antigens by ELISA. Occupation and age 10 years and greater were considered surrogates of occupation-related mobility. Risk factors for P. falciparum and P. vivax infections detected by PRBC-qPCR were assessed by multilevel logistic regression models.ResultsAmong 450 subjects, the prevalence of P. vivax by PRBC-PCR (25.1%) was sixfold higher than that determined by microscopy (3.6%). The prevalence of P. falciparum infection was 4.9% by PRBC-PCR and 0.2% by microscopy. More than 40% of infections had parasitaemia under 5 parasites/μL. Multivariate analysis for infections detected by PRBC-PCR showed that participants with recent settlement in the study area (AOR 2.1; 95% CI 1.03:4.2), age ≥ 30 years (AOR 3.3; 95% CI 1.6:6.9) and seropositivity to P. vivax (AOR 1.8; 95% CI 1.0:3.2) had significantly higher likelihood of P. vivax infection, while the odds of P. falciparum infection was higher for participants between 10 and 29 years (AOR 10.7; 95% CI 1.3:91.1) and with a previous P. falciparum infection (AOR 10.4; 95% CI 1.5:71.1).ConclusionsThis study confirms the contrasting transmission patterns of P. vivax and P. falciparum in the Peruvian Amazon, with stable local transmission for P. vivax and the source of P. falciparum to the study villages dominated by very low parasitaemia carriers, age 10 years and older, who had travelled away from home for work and brought P. falciparum infection with them.

Temporal genetic changes in Plasmodium vivax apical membrane antigen 1 over 19\xa0years of transmission in southern Mexico

BackgroundMexico advanced to the pre-elimination phase in 2009 due to a significant reduction in malaria cases, and since 2000, Plasmodium vivax is the only species transmitted. During the last two decades, malaria transmission has been mostly local and isolated to a few regions. It is important to gain further insights into the impact of control measures on the parasite population structure. Hence, the aim of the current study was to determine detailed changes in P. vivax genetic diversity and population structure based on analysing the gene that encodes the apical membrane antigen 1 (pvama1). This analysis covered from control to pre-elimination (1993–2011) in a hypo-endemic region in southern Mexico.ResultsThe 213 pvama1I-II sequences presently analysed were grouped into six periods of three years each. They showed low genetic diversity, with 15 haplotypes resolved. Among the DNA sequences, there was a gradual decrease in genetic diversity, the number of mixed genotype infections and the intensity of positive selection, in agreement with the parallel decline in malaria cases. At the same time, linkage disequilibrium (R2) increased. The three-dimensional haplotype network revealed that pvama1I-II haplotypes were separated by 1–11 mutational steps, and between one another by 0–3 unsampled haplotypes. In the temporal network, seven haplotypes were detected in at least two of the six-time layers, and only four distinct haplotypes were evidenced in the pre-elimination phase. Structure analysis indicated that three subpopulations fluctuated over time. Only 8.5% of the samples had mixed ancestry. In the pre-elimination phase, subpopulation P1 was drastically reduced, and the admixture was absent.ConclusionsThe results suggest that P. vivax in southern Mexico evolved based on local adaptation into three “pseudoclonal” subpopulations that diversified at the regional level and persisted over time, although with varying frequency. Control measures and climate events influenced the number of malaria cases and the genetic structure. The sharp decrease in parasite diversity and other related genetic parameters during the pre-elimination phase suggests that malaria elimination is possible in the near future. These results are useful for epidemiological surveillance.

Immunological Testing Reveals Exposure to Malaria in the Hypoendemic Region of Iran.

Background. South eastern parts of Iran remain endemic for malaria infection. There is some concern that malaria infection may spread into Bushehr, which is located in the south western part bordering the Persian Gulf and at the periphery of the declared endemic region Hormozgan province due to frequency of visitors from eastern endemic areas and from neighboring malaria endemic countries. We investigated malaria prevalence in Bushehr. Methods and Results. Attempts were made to identify malaria active infection in blood smears and malaria specific antibody and antigens in serum samples. Traditional blood smears prepared from 1955 blood specimens yielded no definitive malaria positive case by microscopic technique. A total of 270 (13.8%) serum samples were positive for malaria antibodies. Using specific ELISA kits, presence of histidine rich proteins and lactate dehydrogenase antigens were investigated in serum samples. No histidine rich proteins specific for P. falciparum were detected amongst 270 antibody positive samples. However, six samples representing 0.3% of total population, were found to be positive for plasmodium pan specific lactate dehydrogenase antigens. This suggested the possibility of low level exposure to malaria in Bushehr community. Conclusions. Out of a total of 1955 samples tested, 270 (13.8%) were positive for malaria antibodies and six (0.3%) of these were positive for plasmodium-specific lactate dehydrogenase antigen suggesting a low level exposure to malaria in a hypoendemic region based on immunological testing. Since none of the 270 antibody samples were positive for histidine rich protein antigens, there is scope for further testing of blood samples by molecular methods such as polymerase chain reactions to confirm the plasmodium species and provide information valuable for future investigations. Our testing strategy for hypoemdemic malaria can be used as a template for investing malaria in 32 eliminating countries for testing ongoing transmission. This approach may be useful as a method in epidemiological studies.

Relationship of regulatory T cells to Plasmodium falciparum malaria symptomatology in a hypoendemic region

BackgroundPrevious data have suggested that regulatory T cells (Tregs) balance protective immune responses with immune mediated pathology in malaria. This study aimed to determine to test the hypothesis that Treg proportions or absolute levels are associated with parasitaemia and malaria symptoms.MethodsTreg cells were quantified by flow cytometry as CD4+ CD25+, Foxp3+, CD127low T cells. Three patient groups were assessed: patients with symptomatic Plasmodium falciparum malaria (S), subjects with asymptomatic P. falciparum parasitaemia (AS) and uninfected control individuals (C).ResultsS, AS and C groups had similar absolute numbers and percentage of Tregs (3.9%, 3.5% and 3.5% respectively). Levels of parasitaemia were not associated with Treg percentage (p = 0.47).ConclusionNeither relative nor absolute regulatory T cell numbers were found to be associated with malaria-related symptomatology in this study. Immune mechanisms other than Tregs are likely to be responsible for the state of asymptomatic P. falciparum parasitaemia in the Peruvian Amazon; but further study to explore these mechanisms is needed.

Genotyping of Plasmodium falciparum using antigenic polymorphic markers and to study anti-malarial drug resistance markers in malaria endemic areas of Bangladesh

BackgroundIn the past many regions of Bangladesh were hyperendemic for malaria. Malaria control in the 1960s to 1970s eliminated malaria from the plains but in the Chittagong Hill Tracts remained a difficult to control reservoir. The Chittagong Hill Tracts have areas with between 1 and 10% annual malaria rates, predominately 90-95% Plasmodium falciparum. In Southeast Asia, multiplicity of infection for hypo-endemic regions has been approximately 1.5. Few studies on the genetic diversity of P. falciparum have been performed in Bangladesh. Anderson et al. performed a study in Khagrachari, northern Chittagong Hill Tracts in 2002 on 203 patients and found that parasites had a multiplicity of infection of 1.3 by MSP-1, MSP-2 and GLURP genotyping. A total of 94% of the isolates had the K76T Pfcrt chloroquine resistant genotype, and 70% showed the N86Y Pfmdr1 genotype. Antifolate drug resistant genotypes were high with 99% and 73% of parasites having two or more mutations at the dhfr or dhps loci.MethodsNested and real-time polymerase chain reaction (PCR) methods were used to genotype P. falciparum using antigenic polymorphic markers and to study anti-malarial drug resistance markers in malaria endemic areas of Bangladesh.ResultsThe analysis of polymorphic and drug resistant genotype on 33 paired recrudescent infections after drug treatment in the period 2004 to 2008 in the Chittagong Hill Tracts, which is just prior to countrywide provision of artemisinin combination therapy. Overall the multiplicity of infection for MSP-1 was 2.7 with a slightly smaller parasite diversity post-treatment. The 13 monoclonal infections by both GLURP and MSP-1 were evenly divided between pre- and post-treatment. The MSP-1 MAD block was most frequent in 66 of the samples. The prevalence of the K76T PfCRT chloroquine resistant allele was approximately 82% of the samples, while the resistant Pfmdr1 N86Y was present in 33% of the samples. Interestingly, the post-treatment samples had a small but significantly higher frequency of the sensitive PfCRT alleles by RT-PCR.ConclusionThe parasite population retains high population diversity despite hypo-endemic transmission with retention, but decrease in the chloroquine-resistant allele and Pfmdr1 resistant alleles in the Chittagong Hill Tracts of Bangladesh.

Investigation of Host Candidate Malaria-Associated Risk/Protective SNPs in a Brazilian Amazonian Population

The Brazilian Amazon is a hypo-endemic malaria region with nearly 300,000 cases each year. A variety of genetic polymorphisms, particularly in erythrocyte receptors and immune response related genes, have been described to be associated with susceptibility and resistance to malaria. In order to identify polymorphisms that might be associated with malaria clinical outcomes in a Brazilian Amazonian population, sixty-four human single nucleotide polymorphisms in 37 genes were analyzed using a Sequenom massARRAY iPLEX platform. A total of 648 individuals from two malaria endemic areas were studied, including 535 malaria cases (113 individuals with clinical mild malaria, 122 individuals with asymptomatic infection and 300 individuals with history of previous mild malaria) and 113 health controls with no history of malaria. The data revealed significant associations (p<0.003) between one SNP in the IL10 gene (rs1800896) and one SNP in the TLR4 gene (rs4986790) with reduced risk for clinical malaria, one SNP in the IRF1 gene (rs2706384) with increased risk for clinical malaria, one SNP in the LTA gene (rs909253) with protection from clinical malaria and one SNP in the TNF gene (RS1800750) associated with susceptibility to clinical malaria. Also, a new association was found between a SNP in the CTL4 gene (rs2242665), located at the major histocompatibility complex III region, and reduced risk for clinical malaria. This study represents the first association study from an Amazonian population involving a large number of host genetic polymorphisms with susceptibility or resistance to Plasmodium infection and malaria outcomes. Further studies should include a larger number of individuals, refined parameters and a fine-scale map obtained through DNA sequencing to increase the knowledge of the Amazonian population genetic diversity.

Age-dependent sex bias in clinical malarial disease in hypoendemic regions.

Background and ObjectivesExperimental models show a male bias in murine malaria; however, extant literature on biases in human clinical malaria is inconclusive. Studies in hyperendemic areas document an absence of sexual dimorphism in clinical malaria. Data on sex bias in clinical malaria in hypoendemic areas is ambiguous—some reports note a male bias but do not investigate the role of differential mosquito exposure in that bias. Moreover, these studies do not examine whether the bias is age related. This study investigates whether clinical malaria in hypoendemic regions exhibits a sex bias and whether this bias is age-dependent. We also consider the role of vector exposure in this bias.MethodsRetrospective passive clinical malaria datasets (2002–2007) and active surveillance datasets (2000–2009) were captured for the hypoendemic Mumbai region in Western India. To validate findings, passive retrospective data was captured from a primary malaria clinic (2006–2007) in hypoendemic Rourkela (Eastern India). Data was normalized by determining percent slide-positivity rates (SPRs) for males and females, and parasite-positivity distributions were established across age groups. The Mann–Whitney test, Wilcoxon Signed Rank test, and Chi-square analysis were used to determine statistical significances.ResultsIn both the Mumbai and Rourkela regions, clinical malaria exhibited an adult male bias (p<0.01). A sex bias was not observed in children aged ≤10. Post-puberty, male SPRs were significantly greater than females SPRs (p<0.01). This adult male bias was observed for both vivax and falciparum clinical disease. Analysis of active surveillance data did not reveal an age or sex bias in the frequency of parasite positivity.ConclusionThis study demonstrates an age-dependent sex bias in clinical malaria in hypoendemic regions and enhanced incidence of clinical malaria in males following puberty. Possible roles of sex hormones, vector exposure, co-infections, and other factors in this enhanced susceptibility are discussed.

Genetic variation of TLR-4, TLR-9 and TIRAP genes in Iranian malaria patients

BackgroundToll-like receptors (TLRs) recognize pathogen-associated molecular patterns and their activation leads to the induction of effector genes involving inflammatory cytokines that may have contribute to controlling parasite growth and disease pathogenesis. The current immunogenetic study was designed to analyse the key components of innate immunity, TLRs and TIRAP (Toll-interleukin-1 receptor domain-containing adaptor protein), also known as MAL (MYD88 adaptor-like), in Iranian patients with mild malaria.MethodsThe tlr-4 (D299G and T399I), tlr-9 (T-1486C and T-1237C) and tirap (S180L) genes were assessed in 640 Baluchi individuals (320 Plasmodium falciparum-infected and 320 non-infected, median age of 28 years) from malaria-endemic regions using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods.ResultsCommon tlr-4 SNPs and promoter SNPs of tlr-9 were distributed among P. falciparum-infected and non-infected groups (P > 0.05) that showed no association of these variants with mild clinical manifestation. The comparison of the tirap S180L genotypes between patients with mild malaria and those healthy individuals showed that the frequency of heterozygosity was significantly higher in infected than non-infected individuals (33.8 vs. 25.6; OR, 1.479; 95% CI, 1.051-2.081; P = 0.024). The result also revealed a significant association of tirap S180L (P < 0.05) with development of mild malaria, which is common in Baluchi populations, who are living in malaria hypoendemic region of Iran but not in African populations (0%-6%).ConclusionThese data point towards the need for addressing the exact role of TLRs in contributing to human genetic factors in malaria susceptibility/resistance/severity within different malaria settings in the world.

Non-variant specific antibody responses to the C-terminal region of merozoite surface protein-1 of Plasmodium falciparum (PfMSP-119) in Iranians exposed to unstable malaria transmission

BackgroundThe C-terminal region of Plasmodium falciparum merozoite surface protein-1 (PfMSP-119) is a leading malaria vaccine candidate antigen. However, the existence of different variants of this antigen can limit efficacy of the vaccine development based on this protein. Therefore, in this study, the main objective was to define the frequency of PfMSP-119 haplotypes in malaria hypoendemic region of Iran and also to analyse cross-reactive and/or variant-specific antibody responses to four PfMSP-119 variant forms.MethodsThe PfMSP-119 was genotyped in 50 infected subjects with P. falciparum collected during 2006-2008. Four GST-PfMSP-119 variants (E/TSR/L, E/TSG/L, E/KNG/F and Q/KNG/L) were produced in Escherichia coli and naturally occurring IgG antibody to these proteins was evaluated in malaria patients' sera (n = 50) using ELISA. To determine the cross-reactivity of antibodies against each PfMSP-119 variant in P. falciparum-infected human sera, an antibody depletion assay was performed in eleven corresponding patients' sera.ResultsSequence data of the PfMSP-119 revealed five variant forms in which the haplotypes Q/KNG/L and Q/KNG/F were predominant types and the second most frequent haplotype was E/KNG/F. In addition, the prevalence of IgG antibodies to all four PfMSP-119 variant forms was equal and high (84%) among the studied patients' sera. Immunodepletion results showed that in Iranian malaria patients, Q/KNG/L variant could induce not only cross-reactive antibody responses to other PfMSP-119 variants, but also could induce some specific antibodies that are not able to recognize the E/TSG/L or E/TSR/L variant forms.ConclusionThe present findings demonstrated the presence of non-variant specific antibodies to PfMSP-119 in Iranian falciparum malaria patients. This data suggests that polymorphism in PfMSP-119 is less important and one variant of this antigen, particularly Q/KNG/L, may be sufficient to be included in PfMSP-119-based vaccine.

IgG subclasses pattern and high-avidity antibody to the C-terminal region of merozoite surface protein 1 of Plasmodium vivax in an unstable hypoendemic region in Iran

The C-terminal region of Plasmodium vivax merozoite surface protein 1 (PvMSP-1 19) is a leading vaccine candidate for inclusion in a polyvalent malaria vaccine. In the present study, the IgG subclasses profile and the avidity of IgG to PvMSP-1 19 were evaluated in individuals ( n = 94) naturally exposed to P. vivax parasite in malaria endemic areas in Chabahar districts, Iran. In individuals with patent P. vivax malaria, 86.1% was sero-positive to PvMSP-1 19 and IgG1 (81.9%) was the predominant subclass. In addition, to determine the persistence of specific IgG, IgG1 and IgG3 antibodies to PvMSP-1 19, the frequency of antibodies was determined in the infected subjects ( n = 74) after treatment with standard chloroquine and it was detected that the frequency of responders was significantly reduced to 51.3%, 51% and 16.2%, respectively. The antigen-binding avidity of IgG antibodies to PvMSP-1 19 was measured in sero-positive sera and the high-avidity of IgG, IgG1 and IgG3 was found in 66.6%, 61% and 47% of the infected subjects with P. vivax, respectively. The present result shows that individuals who exposed to vivax malaria in the endemic region in Iran develop antibodies with high-avidity to PvMSP-1 19. These results could help to understand the interactions between the host and P. vivax parasite in development of MSP-1 19-based vaccine.

Molecular analysis of chloroquine resistance in Plasmodium falciparum in Yunnan Province, China

Resistance of Plasmodium falciparum to chloroquine (CQ) is determined by the mutation at K76T of the P. falciparum chloroquine resistance transporter (pfcrt) gene and modified by other mutations in this gene and in the P. falciparum multidrug resistance 1 (pfmdr1) gene. To determine the extent of polymorphisms in these genes in field P. falciparum isolates from Yunnan province of China, we genotyped the pfcrt codon 76, pfmdr1 codons 86 and 1246. Our results showed that although CQ has been withdrawn from treating falciparum malaria for over two decades, 90.3% of the parasites still carried the pfcrt K76T mutation. In contrast, mutations at pfmdr1 codons 86 and 1246 were rare. Sequencing analysis of the pfcrt gene in 34 parasite field isolates revealed CVIET at positions 72-76 as the major type, consistent with the theory of Southeast Asian origin of CQ resistance in the parasite. In addition, two novel pfcrt haplotypes (75D/144Y/220A and 75E/144Y/220A) were identified. Real-time polymerase chain reaction was used to determine pfmdr1 gene amplification, which is associated with mefloquine resistance. Our result indicated that in agreement with that mefloquine has not been used in this area, most (>90%) of the parasites had one pfmdr1 copy. Genotyping at two hypervariable loci showed relatively low levels of genetic diversity of the parasite population. Meanwhile, 28.4% of cases were found to contain mixed clones, which favour genetic recombination. Furthermore, despite a unique history of antimalarial drugs in Yunnan, its geographical connections with three malarious countries facilitate gene flow among parasite populations and evolution of novel drug-resistant genotypes. Therefore, continuous surveillance of drug resistance in this area is necessary for timely adjustment of local drug policies and more effective malaria control.