Plasmodium Species Distribution Research Articles

A Comprehensive Study on Prevalence, Species Distribution, and Influencing Factors of Malaria in Dir Lower, Pakistan

Background: Malaria remains a significant public health challenge in Pakistan, particularly in the Khyber Pakhtunkhwa province. Tehsil Samarbagh in the Dir Lower region exemplifies the areas heavily burdened by this parasitic disease. Understanding the prevalence and distribution of malaria and its causative Plasmodium species is crucial for developing targeted interventions. Objective: This study aimed to assess the prevalence of malaria, identify the distribution of Plasmodium species, and evaluate the factors influencing malaria infection in Tehsil Samarbagh, Dir Lower, Pakistan. Methods: A cross-sectional study was conducted from January to December 2023. Non-probability convenient sampling was employed to collect 1,925 blood samples from suspected malaria patients across various Union Councils in Tehsil Samarbagh. Malaria diagnosis was performed using thin and thick blood films stained with Giemsa, and species identification was achieved through microscopy. Data on demographic variables, clinical symptoms, and environmental conditions were also collected and analyzed using SPSS version 25. Results: The overall prevalence of malaria was found to be 15.01%. Plasmodium vivax was the predominant species, accounting for 71% of the positive cases, followed by Plasmodium falciparum at 21%, and mixed infections at 8%. Prevalence varied significantly across different Union Councils, with the highest rate observed in Samarbagh (18.96%). Males were more affected (17.66%) than females (11.44%). The age group most at risk was 31-40 years (19.69%). Seasonal variation was evident, with the highest prevalence in September (22.42%) correlating with peak temperatures and humidity levels. Conclusion: The study underscores the continued public health challenge posed by malaria in Tehsil Samarbagh, highlighting the dominance of Plasmodium vivax. Variations in prevalence by geographic area, gender, age, and season necessitate targeted public health interventions and enhanced diagnostic capabilities for malaria control and prevention.

The Occurrence and Distribution of Plasmodium Species in Woyn Wuha Health Center, Ethiopia.

Plasmodium species is an important causative agent of malaria in the world including Ethiopia, and the majority of people were at risk of infection. The study's general objective was to determine the occurrence and distribution of Plasmodium species in the study area through microscopic examination of blood films. A cross-sectional study was carried out in the study sites from September 2016 to February 2017. Out of 512 participants, 32 (6.25%) were malaria positive. Of these, 17 (53.12%, 95% CI: 0.358, 0.704) were P. vivax, 12 (37.5%, 95% CI: 0.207, 0.543) P. falciparum, and 3 (9.375%, 95% CI: -0.007, 0.195) mixed out of the total positive case. The occurrence of parasites was greater in rural villages (59.375%) than in urban villages (40.625%) but not significant (χ2 = 1.2917, df = 1, p = 0.2557). More males were infected compared to females but not significant (χ2 = 0.0005665, df = 1, p = 0.981). The monthly distribution of Plasmodium species was higher in September and October but there was no significant variation in each month (χ2 = 10.142, p = 0.4281). Due to the high occurrence of Plasmodium vivax in the study area, the result contrasts with the national figure of the Plasmodium species report. The result of the current study may be useful to those individuals who work in Plasmodium species control and prevention program.

Malaria Prevalence and Distribution of Plasmodium Species in Southern Region of Ethiopia.

Malaria is caused by Plasmodium species and transmitted by Anopheles mosquitoes, which is the most common medical concern all over the world, including in Ethiopia. The current systematic review's goal was to determine the overall malaria prevalence and Plasmodium species distribution in Ethiopia's southern area. To achieve these objectives, 716 articles were manually searched from online databases such as PubMed, Scopus, Google Scholar, Science Direct, and Web of Science. The pooled metalogistic regression was calculated with the STATA 16 software to present the pooled prevalence with a 95% confidence interval (CI). Eighteen full-text articles met the inclusion criteria and were included in the study, out of the 716 studies initially identified. The majority of the articles in the systematic review used a cross-sectional study design, with sample sizes ranging from 160 to 583,668 participants. The study's lowest and highest malaria prevalence was 0.93% and 82.84%, respectively. During the current systematic review, the estimated malaria prevalence was 19.19% (95% CI: 14.67–23.70). There were 263,476 positive individuals in the study, accounting for 148,734, 106,946, and 7,796 cases of P. falciparum, P. vivax, and mixed infections, respectively. The overall prevalence of P. falciparum and P. vivax was 8.97% (95% CI: 6.31, 11.63) and 7.94% (95% CI: 6.56, 9.33), respectively. According to the systematic review, the most predominant Plasmodium species responsible for malaria disease in the study area was P. falciparum. The highest malaria rates were found in this systematic review. In the systematic review, P. falciparum was the most dominant Plasmodium species that was responsible for malaria disease in the study area. This systematic review indicates the highest malaria prevalence in the southern regions of Ethiopia. Therefore, existing malaria prevention and control strategies in the southern region of Ethiopia should be revised.

Plasmodium interspecies interactions during a period of increasing prevalence of Plasmodium ovale in symptomatic individuals seeking treatment: an observational study

The epidemiology and severity of non-falciparum malaria in endemic settings has garnered little attention. We aimed to characterise the prevalence, interaction, clinical risk factors, and temporal trends of non-falciparum Plasmodium species among symptomatic individuals presenting at health-care facilities in endemic settings of Kenya. We diagnosed and analysed infecting malaria species (Plasmodium falciparum, Plasmodium ovale curtisi, Plasmodium ovale wallikeri, and Plasmodium malariae) via PCR in clinical samples collected between March 1, 2008, and Dec 31, 2016, from six hospitals located in different regions of Kenya. We recruited patients aged 6 months or older who presented at outpatient departments with symptoms of malaria or tested positive for uncomplicated malaria by malaria rapid diagnostic test. Descriptive statistics were used to describe the prevalence and distribution of Plasmodium species. A statistical model was designed and used for estimating the frequency of Plasmodium species and assessing interspecies interactions. Mixed-effect linear regression models with random slopes for each location were used to test for change in prevalence over time. Samples from 2027 symptomatic participants presenting at care facilities were successfully analysed for all Plasmodium species. 1469 (72·5%) of the samples were P falciparum single-species infections, 523 (25·8%) were mixed infections, and only 35 (1·7%) were single non-falciparum species infections. 452 (22·3%) were mixed infections containing P ovale spp. A likelihood-based model calculation of the population frequency of each species estimated a significant within-host interference between P falciparum and P ovale curtisi. Mixed-effect logistic regression models identified a significant increase in P ovale wallikeri (2·1% per year; p=0·043) and P ovale curtisi (0·7% per year; p=0·0002) species over time, with a reciprocal decrease in P falciparum single-species infections (2·5% per year; p=0·0065). The frequency of P malariae infections did not significantly change over time. Risk of P falciparum infections presenting with fever was lower if co-infected with P malariae (adjusted odds ratio 0·43, 95% CI 0·25-0·74; p=0·0023). Our results show a prevalence of non-falciparum species infections of 27·5% among symptomatic individuals presenting at care facilities, which is higher than expected from previous cross-sectional surveys. The proportion of infections with P ovale wallikeri and P ovale curtisi was observed to significantly increase over the period of study, which could be due to attenuated responsiveness of these species to malaria drug treatment. The increase in frequency of P ovale spp could threaten the malaria control efforts in Kenya and pose increased risk of malaria to travellers. Armed Forces Health Surveillance Branch and its Global Emerging Infections Surveillance Section.

Immune Responses in Malaria and Vaccine Strategies.

Malaria is a pandemic with nearly half of global population at risk, caused by parasite Plasmodium species, particularly P. falciparum with a high morbidity and mortality, especially among children. There is an urgent need for development of population protective vaccines, such as in sub-Saharan low-income countries, where P. falciparum malaria is endemic. After years of endeavour with children and adults for safety and efficacy clinical trials, the P. falciparum circumsporozoite protein antigen, is targeted by specific antibodies induced by recombinant vaccine, called TRS,S. TRS,S has been authorized by WHO and Malawi Government to be the first malaria vaccine for up to 2years of aged children for protection against malaria. Other malaria vaccines in clinical trials are also very promising candidates, including the original live, X-ray attenuated P-sporozoite vaccine, inducing antigen-specific T cell immunity at liver stage. Malaria parasite at blood symptomatic stage is targeted by specific antibodies to parasite-infected erythrocytes, which are important against pathogenic placenta-infected erythrocyte sequestration. Here, the demographic distribution of Plasmodium species and their pathogenicity in infected people are discussed. The role of innate phagocytic cells and malaria antigen specific T cell immunity, as well as that of specific antibody production by B cells are highlighted. The paramount role of cytotoxic CD8+ T cellular immunity in malaria people protection is also included.

Molecular surveillance and temporal monitoring of malaria parasites in focal Vietnamese provinces

BackgroundWhile the World Health Organization (WHO) Southeast Asia region has the second highest incidence of malaria worldwide, malaria in Vietnam is focal to few provinces, where delayed parasite clearance to anti-malarial drugs is documented. This study aims to understand Plasmodium species distribution and the genetic diversity of msp1 and msp2 of parasite populations using molecular tools.MethodsA total of 222 clinical isolates from individuals with uncomplicated malaria were subjected to Plasmodium species identification by nested real-time PCR. 166 isolates positive for Plasmodium falciparum mono infections were further genotyped for msp1 (MAD20, K1, and RO33), and msp2 allelic families (3D7 and FC27). Amplicons were resolved through capillary electrophoresis in the QIAxcel Advanced system.ResultsMono-infections were high and with 75% P. falciparum, 14% Plasmodium vivax and 9% P. falciparum/P. vivax co-infections, with less than 1% Plasmodium malariae identified. For msp1, MAD20 was the most prevalent (99%), followed by K1 (46%) allelic family, with no sample testing positive for RO33 (0%). For msp2, 3D7 allelic family was predominant (97%), followed by FC27 (10%). The multiplicity of infection of msp1 and msp2 was 2.6 and 1.1, respectively, and the mean overall multiplicity of infection was 3.7, with the total number of alleles ranging from 1 to 7.ConclusionsGiven the increasing importance of antimalarial drugs in the region, the genetic diversity of P. falciparum msp1 and msp2 should be regularly monitored with respect to treatment outcomes and/or efficacy studies in regions, where there are ongoing changes in the malaria epidemiology.

Malaria distribution and performance of malaria diagnostic methods in Malaysia (1980\u20132019): a systematic review

BackgroundMalaysia has already achieved remarkable accomplishments in reaching zero indigenous human malaria cases in 2018. Prompt malaria diagnosis, surveillance and treatment played a key role in the country’s elimination success. Looking at the dynamics of malaria distribution during the last decades might provide important information regarding the potential challenges of such an elimination strategy. This study was performed to gather all data available in term of prevalence or incidence on Plasmodium infections in Malaysia over the last four decades.MethodsA systematic review of the published English literature was conducted to identify malaria distribution from 1980 to June 2019 in Malaysia. Two investigators independently extracted data from PubMed, Scopus, Web of Science and Elsevier databases for original papers.ResultsThe review identified 46 epidemiological studies in Malaysia over the 39-year study period, on which sufficient information was available. The majority of studies were conducted in Malaysia Borneo (31/46; 67.4%), followed by Peninsular Malaysia (13/46; 28.3%) and in both areas (2/46; 4.3%). More than half of all studies (28/46; 60.9%) were assessed by both microscopy and PCR. Furthermore, there was a clear trend of decreases of all human malaria species with increasing Plasmodium knowlesi incidence rate throughout the year of sampling period. The summary estimates of sensitivity were higher for P. knowlesi than other Plasmodium species for both microscopy and PCR. Nevertheless, the specificities of summary estimates were similar for microscopy (40–43%), but varied for PCR (2–34%).ConclusionsThis study outlined the epidemiological changes in Plasmodium species distribution in Malaysia. Malaria cases shifted from predominantly caused by human malaria parasites to simian malaria parasites, which accounted for the majority of indigenous cases particularly in Malaysia Borneo. Therefore, malaria case notification and prompt malaria diagnosis in regions where health services are limited in Malaysia should be strengthened and reinforced to achieving the final goal of malaria elimination in the country.

Sero-prevalence of Plasmodium falciparum and Plasmodium malariae among HIV-positive patients in Jos, Plateau State, North-central Nigeria

Malaria is a leading cause of disease burden in Nigeria, although surprisingly few contemporary, age-stratified data exist on malaria epidemiology in the country. Transmission of Plasmodium falciparum and P. Malariae among HIV –infected individuals was studied in Jos, Central Nigeria to ascertain the prevalence of malaria and HIV infection with a specific focus on how risk factors differ between demographic groups. Blood samples were collected from individuals by venepuncture in 5 ml vacutainers and tubes containing Ethylene diamine tetra acetic acid (EDTA). Thick and thin blood smears were made and stained with Giemsa. These were screened for HIV and microscopically examined for malaria parasites according to standard procedure. The demographic data of the patients were obtained and documented. Out of 933 HIV-infected individuals screened for Plasmodium parasites, an overall malaria prevalence of 16.2% (151/933) was observed. Of this number, 120(12.8%) were infected with P. falciparum, 28(3.0%) were infected with P. malariae while 3(0.3%) had mixed infections. P. falciparum and P. malariae were found more in patients under 15 years of age (33.3%). Malaria was least common among the 15 to 25 year old age group (14.2%). There was however no significant difference (p>0.05) in the Plasmodium species distribution among the different age groups. This study shows that HIV/AIDS, P. falciparum and P. malariae are prevalent within the population and calls for concerted effort and intervention by the government, policy makers and indeed all and sundry to stop the spread. Effective policies and services are needed to reduce the substantial disease burden among the general population.

Distribution of Plasmodium species and assessment of performance of diagnostic tools used during a malaria survey in Southern and Western Provinces of Zambia

BackgroundZambia continues to make strides in reducing malaria burden through the use of proven malaria interventions and has recently pledged to eliminate malaria by 2021. Case management services have been scaled up at community level with rapid diagnostic tests (RDTs) providing antigen-based detection of falciparum malaria only. Key to national malaria elimination goals is the ability to identify, treat and eliminate all Plasmodium species. This study sought to determine the distribution of non-falciparum malaria and assess the performance of diagnostic tests for Plasmodium falciparum in Western and Southern Provinces of Zambia, two provinces planned for early malaria elimination.MethodsA sub-set of individuals’ data and samples from a cross-sectional household survey, conducted during peak malaria transmission season in April and May 2017, was used. The survey collected socio-demographic information on household members and coverage of malaria interventions. Malaria testing was done on respondents of all ages using blood smears and RDTs while dried blood spots were collected on filter papers for analysis using photo-induced electron transfer polymerase chain reaction (PET-PCR). Slides were stained using Giemsa stain and examined by microscopy for malaria parasites.ResultsFrom the 1567 individuals included, the overall prevalence of malaria was 19.4% (CI 17.5–21.4) by PCR, 19.3% (CI 17.4–21.4) by RDT and 12.9% (CI 11.3–14.7) by microscopy. Using PET-PCR as the gold standard, RDTs showed a sensitivity of 75.7% (CI 70.4–80.4) and specificity of 94.2% (CI 92.8–95.4). The positive predictive value (PPV) was 75.9% (CI 70.7–80.6) and negative predictive value (NPV) was 94.1% (CI 92.1–95.4). In contrast, microscopy for sensitivity, specificity, PPV, and NPV values were 56.9% (CI 51.1–62.5), 97.7% (CI 96.7–98.5), 85.6% (CI 80.0–90.2), 90.4% (CI 88.7–91.9), respectively. Non-falciparum infections were found only in Western Province, where 11.6% of P. falciparum infections were co-infections with Plasmodium ovale or Plasmodium malariae.ConclusionFrom the sub-set of survey data analysed, non-falciparum species are present and occurred as mixed infections. As expected, PET-PCR was slightly more sensitive than both malaria RDTs and microscopy to detecting malaria infections.

Evaluating seroprevalence to circumsporozoite protein to estimate exposure to three species of Plasmodium in the Brazilian Amazon

BackgroundBrazil has seen a great decline in malaria and the country is moving towards elimination. However, for eventual elimination, the control program needs efficient tools in order to monitor malaria exposure and transmission. In this study, we aimed to evaluate whether seroprevalence to the circumsporozoite protein (CSP) is a good tool for monitoring the exposure to and/or evaluating the burden and distribution of Plasmodium species in the Brazilian Amazon.MethodsCross-sectional surveys were conducted in a rural area of Porto Velho, Rondônia state. Parasite infection was detected by microscopy and polymerase chain reaction. Antibodies to the sporozoite CSP repeats of Plasmodium vivax, P. falciparum, and P. malariae (PvCS, PfCS, and PmCS) were detected using the enzyme-linked immunosorbent assay technique. Human leukocyte antigen (HLA)-DRB1 and DQB1 genes were typed using Luminex® xMAP® technology.ResultsThe prevalence of immunoglobulin G against P. vivax CSP peptide (62%) was higher than P. falciparum (49%) and P. malariae (46%) CSP peptide. Most of the studied individuals had antibodies to at least one of the three peptides (72%), 34% had antibodies to all three peptides and 28% were non-responders. Although the majority of the population was not infected at the time of the survey, 74.3% of parasite-negative individuals had antibodies to at least one of the CSPs. Importantly, among individuals carrying the haplotypes DRB1*04~DQB1*03, there was a significantly higher frequency of PfCS responders, and DRB1*16~DQB1*03 haplotype for PvCS and PfCS responders. In contrast, HLA-DRB1*01 and HLA-DQB1*05 allelic groups were associated with a lack of antibodies to P. vivax and P. falciparum CSP repeats, and the haplotype DRB1*01~DQB1*05 was also associated with non-responders, including non-responders to P. malariae.ConclusionsOur results show that in low transmission settings, naturally acquired antibody responses against the CSP repeats of P. vivax, P. falciparum, and P. malariae in a single cross-sectional study may not represent a valuable marker for monitoring recent malaria exposure, especially in an area with a high prevalence of P. vivax. Furthermore, HLA class II molecules play an important role in antibody response and require further study with a larger sample size. It will be of interest to consider HLA analysis when using serosurveillance to monitor malaria exposure among genetically diverse populations.

Distribution and prevalence of malaria parasites among long-tailed macaques (Macaca fascicularis) in regional populations across Southeast Asia.

BackgroundPlasmodium knowlesi and Plasmodium cynomolgi are two malaria parasites naturally transmissible between humans and wild macaque through mosquito vectors, while Plasmodium inui can be experimentally transmitted from macaques to humans. One of their major natural hosts, the long-tailed macaque (Macaca fascicularis), is host to two other species of Plasmodium (Plasmodium fieldi and Plasmodium coatneyi) and is widely distributed in Southeast Asia. This study aims to determine the distribution of wild macaques infected with malarial parasites by examining samples derived from seven populations in five countries across Southeast Asia.MethodsPlasmodium knowlesi, P. cynomolgi, P. coatneyi, P. inui and P. fieldi, were detected using nested PCR assays in DNA samples from 276 wild-caught long-tailed macaques. These samples had been derived from macaques captured at seven locations, two each in the Philippines (n = 68) and Indonesia (n = 70), and one each in Cambodia (n = 54), Singapore (n = 40) and Laos (n = 44). The results were compared with previous studies of malaria parasites in long-tailed macaques from other locations in Southeast Asia. Fisher exact test and Chi square test were used to examine the geographic bias of the distribution of Plasmodium species in the macaque populations.ResultsOut of 276 samples tested, 177 were Plasmodium-positive, with P. cynomolgi being the most common and widely distributed among all long-tailed macaque populations (53.3 %) and occurring in all populations examined, followed by P. coatneyi (20.4 %), P. inui (12.3 %), P. fieldi (3.4 %) and P. knowlesi (0.4 %). One P. knowlesi infection was detected in a macaque from Laos, representing the first documented case of P. knowlesi in wildlife in Laos. Chi square test showed three of the five parasites (P. knowlesi, P. coatneyi, P. cynomolgi) with significant bias in prevalence towards macaques from Malaysian Borneo, Cambodia, and Southern Sumatra, respectively.ConclusionsThe prevalence of malaria parasites, including those that are transmissible to humans, varied among all sampled regional populations of long-tailed macaques in Southeast Asia. The new discovery of P. knowlesi infection in Laos, and the high prevalence of P. cynomolgi infections in wild macaques in general, indicate the strong need of public advocacy in related countries.

An investigation on the prevalence and efficiency of immunochromatographic testing in suspected malarial patients of Rawalpindi and Islamabad, Pakistan.

The prevalences of Plasmodium falciparum and Plasmodium vivax are increasing rapidly in Pakistan, but recent data on the epidemiology of malaria are not properly reported with scarce diagnostic methods for quick diagnosis. This study was designed to determine the current prevalence and distribution of Plasmodium species in the vicinity of Rawalpindi and Islamabad and report on the validity of the immunochromatographic test (ICT) in diagnosing malarial infections. A total of 1500 blood samples obtained from a local hospital were screened during the course of this study via microscopic examination and ICT. It was seen that malaria was highly endemic in this region. Both P. vivax and P. falciparum were prevalent in all age groups with high seasonal variations, showing a summer peak for P. vivax and a winter peak for P. falciparum. In a comparative study of the diagnostic methods it was observed that the ICT is 95% sensitive and 100% specific for both P. falciparum and P. vivax, while microscopic study was 100% sensitive and 96.8% specific. Epidemiological study of the malarial parasites showed that majority of the patients were from Rawalpindi as compared to Islamabad and that P. vivax was the dominant cause of malarial infection.

Prevalence of malaria, prevention measures, and main clinical features in febrile children admitted to the Franceville Regional Hospital, Gabon.

Recently, major progress has been made in controlling malaria in Africa. However, in Gabon, little information is available on the role of malaria in childhood febrile syndromes, the use and efficacy of preventive measures, and Plasmodium species distribution. Here, we characterized malaria in febrile children in Franceville, Gabon through a cross-sectional study at the pediatric unit of the Franceville Regional Hospital. We registered 940 febrile children. Their general condition was markedly altered in 11.7% of cases (n = 89/760); among them 19 (21.4%) had a severely altered condition. Malaria was the second most frequent etiology (22.0%; n = 162/738), after respiratory tract infections (37.3%; n = 275/738). Children with malaria (63 ± 39 months) were older than children without malaria (40 ± 37 months) (p = 0.0013). Hemoglobin, red blood cell, white blood cell, and platelet values were lower in children with malaria than in those without malaria (p < 0.0001). Anemia was the most common feature of severe malaria (70.6%; n = 12/17), followed by neurological involvement (23.5%; n = 4/17). The prevalence of malaria was significantly higher in children older than 60 months than in younger children (40% vs. 15.5%; p < 0.0001). Plasmodium falciparum accounted for 97.5% of cases (158/162), followed by Plasmodium malariae (2.5%; n = 4/162). Bed net use was high (74.4%; n = 697/936) and contributed to malaria prevention (p = 0.001). Good basic knowledge of malaria also had a preventive effect (p < 0.0001). The prevalence of malaria in children in Franceville did not decrease significantly from 2009 to 2012, remaining at about 20%, highlighting that preventive measures should be reinforced.

Distribution of Plasmodium species on the island of Grande Comore on the basis of DNA extracted from rapid diagnostic tests.

In the Union of Comoros, interventions for combating malaria have contributed to a spectacular decrease in the prevalence of the disease. We studied the current distribution of Plasmodium species on the island of Grande Comore using nested PCR. The rapid diagnostic tests (RDTs) currently used in the Comoros are able to identify Plasmodium falciparum but no other Plasmodium species. In this study, we tested 211 RDTs (158 positive and 53 negative). Among the 158 positive RDTs, 22 were positive for HRP2, 3 were positive only for pLDH, and 133 were positive for HRP2 and pLDH. DNA was extracted from a proximal part of the nitrocellulose membrane of RDTs. A total of 159 samples were positive by nested PCR. Of those, 156 (98.11%) were positive for P. falciparum, 2 (1.25%) were positive for P. vivaxI, and 1 (0.62%) was positive for P. malariae. None of the samples were positive for P. ovale. Our results show that P. falciparum is still the most dominant species on the island of Grande Comore, but P. vivax and P. malariae are present at a low prevalence.

Prevalence and distribution of human Plasmodium infection in Pakistan

BackgroundBoth Plasmodium vivax and Plasmodium falciparum are prevalent in Pakistan, yet up-to-date data on the epidemiology of malaria in Pakistan are not available. This study was undertaken to determine the current prevalence and distribution of Plasmodium species across the country.MethodsA malariometric population survey was conducted in 2011 using blood samples collected from 801 febrile patients of all ages in four provinces and the capital city of Islamabad. Microscopically confirmed Plasmodium-positive blood samples were reconfirmed by polymerase chain reaction (PCR). Confirmed parasite-positive samples were subjected to species-specific PCR capable of detecting four species of human malaria.ResultsOf the 707 PCR-positive samples, 128 (18%) were P. falciparum, 536 (76%) were P. vivax, and 43 (6%) were mixed P. falciparum and P. vivax. Ninety-four microscopy-positive samples were PCR-negative, and Plasmodium malariae and Plasmodium ovale were not detected. Prevalence of P. vivax ranged from 2.4% in Punjab Province to 10.8% in Sindh Province and prevalence of P. falciparum ranged from 0.1% in Islamabad to 3.8% in Balochistan.ConclusionsPlasmodium infections in Pakistan are largely attributed to P. vivax but P. falciparum and mixed species infections are also prevalent. In addition, regional variation in the prevalence and species composition of malaria is high.

Malaria infections are randomly distributed in diverse holoendemic areas of Papua New Guinea.

Malaria is holoendemic in the lowlands of Papua New Guinea (PNG), and interactions among Plasmodium species may influence prevalence of mixed infections. Previously, field samples from a cross-sectional survey in Dreikikir, East Sepik Province, analyzed by blood smear and polymerase chain reaction (PCR), showed that mixed infections were common and randomly distributed in this malaria endemic region. To evaluate further whether Plasmodium species distribution is random, blood smear- and PCR/sequence-specific oligonucleotide probe hybridization-based analyses of cross-sectional survey samples were conducted in 2 additional malaria holoendemic regions of northern PNG. Despite ecologic, species prevalence, and transmission season differences in these new surveys, all 4 Plasmodium species were found to be randomly distributed in each area; random distribution patterns also were observed when study populations were divided into age groups. These findings provide consistent evidence that Plasmodium species infections occur independently of one another in PNG malaria holoendemic sites. This independent occurrence suggests that age-dependent, acquired malaria immunity has limited influence on the distribution pattern of Plasmodium species infections in endemic human populations; infection by 1 human malaria parasite species does not reduce susceptibility to infection by others; and malaria vaccines would exhibit limited protection against blood-stage infection by heterologous Plasmodium species.