Detection of Very Low Level Plasmodium falciparum Infections using the Nested Polymerase Chain Reaction and a Reassessment of the Epidemiology of Unstable Malaria in Sudan

Roper, Cally; Elhassan, Ibrahim M.; Hviid, Lars; Giha, Hayder A.; Richardson, W A R; Babiker, Hamza A.; Satti, Gwiria M. H.; Theander, Thor G.; Arnot, David E.

doi:10.4269/ajtmh.1996.54.325

Cited by 169 publications

(111 citation statements)

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“…2 Re-evaluations of the epidemiology of unstable malaria have now shown that the prevalence of submicroscopic P. falciparum infections is far higher than has previously been expected. 3 Until the PCR came into use it had been difficult to assess correlations of submicroscopic parasitemia with particular features of malarial infections such as spleen size or antibody titers.Although simultaneous infections with different Plasmodium species have been described in humans, 4 detailed reports of prevalences in holoendemic areas were rare before species-specific PCR assays became available. 5 The extent of interspecies interactions in mixed infections is currently the subject of discussion.…”

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High rate of mixed and subpatent malarial infections in southwest Nigeria.

May¹,

Mockenhaupt²,

Ademowo³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

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Abstract. The rate of malarial parasitemia in children and adults was assessed by microscopy and the polymerase chain reaction in a holoendemic area in Nigeria. A high rate of subpatent Plasmodium falciparum parasitemia (19.6%) was found. Plasmodium malariae and P. ovale infections were common in a rural area (26.1% and 14.8%) but were observed sporadically in individuals from an urban area. Simultaneous infections with P. falciparum, P. malariae, and P. ovale were frequent in the rural area (11.7% triple infections). The rate of triple infections was higher than expected from the prevalences of each species (P Ͻ 0.00001). Spleen enlargement was associated with mixed infections of P. falciparum and P. malariae (odds ratio [OR] ϭ 5.9, 95% confidence interval [CI] 3.0-11.7) and less frequently observed in individuals without detectable parasitemia (OR ϭ 0.06, 95% CI ϭ 0.01-0.3). Spleen enlargement and titers of antibodies to schizonts were positively correlated with parasite densities. The results also suggest that in some individuals a long-lasting subpatent parasitemia might occur.In areas holoendemic for Plasmodium falciparum infection, clinical malaria affects mostly young children. Adults have acquired a partial immunity after years of successive exposure to a variety of different parasite strains. An antidisease immunity evolves in early childhood, while an antiparasite immunity develops at the age of 15-20 years. 1 It is yet unclear to what extent subpatent parasitemia contributes to acquired immunity and whether clinically asymptomatic infections reflect effective parasite control or may eventually convert to manifest disease.The polymerase chain reaction (PCR) allows the detection of parasitemia below the threshold of conventional microscopy. 2 Re-evaluations of the epidemiology of unstable malaria have now shown that the prevalence of submicroscopic P. falciparum infections is far higher than has previously been expected. 3 Until the PCR came into use it had been difficult to assess correlations of submicroscopic parasitemia with particular features of malarial infections such as spleen size or antibody titers.Although simultaneous infections with different Plasmodium species have been described in humans, 4 detailed reports of prevalences in holoendemic areas were rare before species-specific PCR assays became available. 5 The extent of interspecies interactions in mixed infections is currently the subject of discussion. In a recent study, it has been suggested that cross-immunity between P. falciparum and P. vivax antigens might occur. 6 However, there is a controversy whether anti-disease-and anti-parasite immunity are in fact species-specific. 7 In a cross-sectional study in an urban and a rural setting of southwest Nigeria, we determined the rates of simultaneous P. falciparum, P. malariae, and P. ovale infections, including submicroscopic parasitemia. Furthermore, we looked at associations of different plasmodial infections with spleen size and with antibody titers against crude schizont antigen. P...

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mentioning

confidence: 99%

mentioning

confidence: 99%

High rate of mixed and subpatent malarial infections in southwest Nigeria.

May¹,

Mockenhaupt²,

Ademowo³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

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Section: Polymerase Chain Reaction (Pcr)mentioning

confidence: 99%

“…The PCR technique has also been used to investigate non-intestinal parasites. The effectiveness of PCR in detecting parasite species such as Leishmania and Plasmodium has already been studied (13)(14)(15)(16)(17)(18)(19)(20)(21)(22).To detect Leishmania in clinical samples, several PCR assays have been developed (17). In studies of visceral Leishmania, PCR has been used for several purposes in addition to diagnosis, such as treatment monitoring and epidemiological studies.…”

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Molecular techniques for the study and diagnosis of parasite infection

Tavares¹,

Staggemeier²,

Borges³

et al. 2011

J. Venom. Anim. Toxins incl. Trop. Dis

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Abstract:In parasitology, routine laboratory diagnosis involves conventional methods, such as optical microscopy, used for the morphological identification of parasites. Currently, molecular biology techniques are increasingly used to diagnose parasite structures in order to enhance the identification and characterization of parasites. The objective of the present study was to review the main current and new diagnostic techniques for confirmation of parasite infections, namely: polymerase chain reaction (PCR), real-time polymerase chain reaction (RT-PCR), loop-mediated isothermal amplification (LAMP), Luminex xMAP, random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), and restriction fragment length polymorphism (RFLP), in addition to microsatellites. Molecular assays have comprehensively assisted in the diagnosis, treatment and epidemiological studies of parasitic diseases that affect people worldwide, helping to control parasitic disease mortality.Key words: parasite infection, diagnosis, molecular techniques, molecular epidemiology. Review ARticle The Journal of Venomous Animals and Toxins including Tropical Diseases ISSN 1678-9199 | 2011 | volume 17 | issue 3 | pages 239-248 INTRODUCTIONIn parasitology, routine laboratory diagnosis involves conventional methods, such as optical microscopy, used for the morphological identification of parasites (1). However, the occasional difficulty of identifying these parasite structures may decrease the sensitivity of such methods. Currently, because of these difficulties, molecular biology has been employed to detect parasites responsible for parasitic diseases (2).Traditional parasitological analyses have the advantage of being less costly without requiring expensive reagents and equipment. Additionally, such analyses can be easily performed when a trained microscopist is available. On the other hand, molecular technology demonstrates the presence of parasites based on their antigenic components or DNA segments (3). These tests are not influenced by environmental factors that usually can interfere with the results of a stool test, for example, thus ensuring highly reliable results (4).Current laboratory diagnostic methods for the identification of parasites include: polymerase chain reaction (PCR), random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP), microsatellite marker method, Luminex xMAP-based technology (areas of multianalyte profiling), loop-mediated isothermal amplification (LAMP), and the recently added real-time PCR (5-12).The objective of the present article was to review the applications of molecular biology techniques in parasitology by evaluating and discussing their uses and benefits. MOLECULAR METHODS FOR DETECTION OF PARASITE STRUCTURESSeveral molecular tests to detect parasites have been developed in the last decade. Their specificity and sensitivity have gradually increased, and parasites that were previously difficult to diagnose usi...

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“…Los individuos con gametocitos observables por microscopía son los más infecciosos, aunque aquéllos con gametocitos por debajo del nivel de detección por microscopía de luz, también producen infecciones en los mosquitos (15). Esta observación es importante, puesto que los individuos asintomáticos pueden tener parásitos en densidades muy bajas (detectables por PCR) durante varios meses (16,17).…”

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Ausencia de malaria asintomática en escolares de Quibdó, Chocó.

2004

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La malaria asintomática es considerada común en zonas de alta transmisión en África y prácticamente ausente en zonas de baja transmisión en Latinoamérica. Sin embargo, algunos reportes sugieren que el hallazgo de casos asintomáticos en zonas de alta y moderada transmisión en Latinoamérica es relativamente frecuente. La malaria asintomática tiene consecuencias graves no sólo para el individuo portador de parásitos, sino también para la comunidad donde vive. Los individuos crónicamente infectados se constituyen en un reservorio de la enfermedad que es difícil de identificar por medio de la vigilancia rutinaria de los programas de control. En el marco de un estudio de la epidemiología de la malaria en Quibdó, Chocó, se estimó la prevalencia de malaria asintomática en escolares. El objetivo fue establecer si los individuos con infección asintomática podrían constituir un reservorio importante de infección, capaz de mantener la transmisión local en esta ciudad. Se seleccionaron 255 estudiantes de cinco escuelas de Quibdó, de los cuales, 223 se incluyeron en el análisis. Algunos niños refirieron cefalea (34%), tos (32%) y diarrea (9%). Todos los resultados de gota gruesa fueron negativos. Además, el análisis por inmunofluorescencia indirecta de anticuerpos contra Plasmodium en una submuestra de 25 niños fue negativo. La prevalencia estimada de malaria asintomática en los escolares de Quibdó es, entonces, de 0% (IC95%: 0-1,4). La presencia de malaria asintomática en adultos no se puede descartar aunque es probable que, si existe, sea en una proporción muy baja. Palabras clave: malaria asintomática, Colombia, Chocó Absence of asymptomatic malaria in schoolchildren of Quibdó, ChocóAsymptomatic malaria is characteristic of high intensity transmission areas in Africa but unusual in low transmission areas in Latin America. Nevertheless, asymptomatic malaria has been reported to be frequent in areas in Latin America with high and moderate intensity of transmission. Asymptomatic malaria can affect both individuals who carry parasites and are cryptic carrier reservoirs for the community. Individuals chronically infected with malaria parasites are usually unidentifiable by most malaria control programmes. In order to identify whether asymptomatic individuals harboring malaria parasites are an important reservoir of infection in Quibdó, Chocó, the prevalence of asymptomatic malaria was assessed in schoolchildren. This study was part of a major study of the epidemiology of malaria in Quibdó. A total of 255 children from 5 schools were examined, of which 223 were included in the analysis. Children reported headache (34%), cough (32%), and diarrhoea (9%). None of the children presented a positive thick smear. In addition, IFA tests in a subsample of 25 children were negative. By these criteria, the prevalence of asymptomatic malaria in Quibdó schoolchildren is 0% (95%C.I.: 0.0-1.4). Although asymptomatic malaria in adults possibly occurs, a very low prevalence is predicted.

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Detection of Very Low Level Plasmodium falciparum Infections using the Nested Polymerase Chain Reaction and a Reassessment of the Epidemiology of Unstable Malaria in Sudan

Abstract: We have used the nested polymerase chain reaction (PCR) to assay for low level Plasmodiumfalciparum

Cited by 169 publications

References 13 publications

High rate of mixed and subpatent malarial infections in southwest Nigeria.

High rate of mixed and subpatent malarial infections in southwest Nigeria.

Molecular techniques for the study and diagnosis of parasite infection

Ausencia de malaria asintomática en escolares de Quibdó, Chocó.

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