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

May, Jürgen; Mockenhaupt, Frank P.; Ademowo, Olusegun G.; Falusi, Adeyinka G.; Olumese, P.E.; Bienzle, Ulrich; Meyer, Christian G.

doi:10.4269/ajtmh.1999.61.339

Cited by 75 publications

(54 citation statements)

References 30 publications

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“…King and P. Zimmerman, unpublished). PCR diagnosis detected similarly high rates of infections in a rural village in Nigeria (P. malariae = 26.1%, P. ovale = 14.8% [60]) and in pregnant women in Kenya (P. malariae = 24.5%, P. ovale = 22.5% [61]). However, in a study in southern Mozambique that typed infections by PCR, substantial spatial and seasonal variations in the prevalence of P. malariae were observed [62].…”

Section: Improved Diagnosis Of P Malariae and P Ovale Infections Bymentioning

confidence: 84%

Plasmodium malariae and Plasmodium ovale – the ‘bashful’ malaria parasites

Müeller

Zimmerman

Reeder

2007

Trends in Parasitology

270

245

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Although Plasmodium malariae was first described as an infectious disease of humans by Golgi in 1886 and Plasmodium ovale identified by Stevens in 1922, there are still large gaps in our knowledge of the importance of these infections as causes of malaria in different parts of the world. They have traditionally been thought of as mild illnesses that are caused by rare and, in case of P. ovale, short-lived parasites. However, recent advances in sensitive PCR diagnosis are causing a re-evaluation of this assumption. Low-level infection seems to be common across malaria-endemic areas, often as complex mixed infections. The potential interactions of P. malariae and P. ovale with Plasmodium falciparum and Plasmodium vivax might explain some basic questions of malaria epidemiology, and understanding these interactions could have an important influence on the deployment of interventions such as malaria vaccines. Geographical distributionAlthough distribution of Plasmodium malariae infection is reported as being patchy, it has been observed in all major malaria-endemic regions of the world [1]. P. malariae infections are most common in sub-Saharan Africa and the southwest Pacific, where age-specific prevalence in mass blood surveys have exceeded 15-30% [2][3][4][5][6][7][8]. By contrast, when P. malariae has been detected in malaria-endemic regions of Asia [9][10][11][12], the Middle East [13], South America [14] and Central America [15], it is observed as an infrequent infection, with blood-smear light microscopy (LM) prevalence rarely exceeding 1-2%. Much higher levels of infection were, however, found in montagnard refugees from the Cambodian-Vietnamese border [16]. In South America, P. malariae is thought to be a zoonotic infection because the genetically identical Plasmodium brasilianum infects new-world monkeys [17] and both monkeys and humans in endemic areas show high levels of seropositivity to P. malariae and P. brasilianum antigens [18].Plasmodium ovale was thought to have a much more limited distribution, with endemic transmission traditionally described as being limited to areas of tropical Africa, New Guinea, the eastern parts of Indonesia and the Philippines [19,20]. Infections with P. ovale, however, have also been reported in the Middle East [13], the Indian subcontinent [21] and different parts of Southeast Asia [11,22,23]. In West Africa (and to a lesser extent Central Africa), age specific LM prevalence of >10% have been observed [3,6] places where P. ovale is observed, it is relatively uncommon and its prevalence (as detected by LM) rarely exceeds 3-5% [22,[24][25][26].Indepth descriptions of the epidemiology of both infections based upon LM data are, thus, restricted almost exclusively to highly endemic areas in Africa and the Southwest Pacific. Detailed epidemiological studies from South America and Asia are lacking. Variation in parasite prevalenceIn West Africa, P. malariae prevalence has been reported to peak at ages similar to those of P. falciparum (i.e. in children under ten years of...

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Section: Improved Diagnosis Of P Malariae and P Ovale Infections Bymentioning

confidence: 84%

Plasmodium malariae and Plasmodium ovale – the ‘bashful’ malaria parasites

Müeller

Zimmerman

Reeder

2007

Trends in Parasitology

270

245

View full text Add to dashboard Cite

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“…Malaria is holoendemic in this area. 15 Two hundred twenty-eight children without overt signs of malaria were enrolled from a nursery and a primary school during the dry season between December 1996 and May 1997. The study group has been previously described.…”

Section: Methodsmentioning

confidence: 99%

“…The study group has been previously described. 15 One hundred samples positive for P. falciparum were randomly selected and typed for the two variants at position 76 of the parasite pfcrt gene. Informed consent was obtained from parents/guardians of children, and the study was reviewed and approved by the Joint Ethical Committee of the University of Ibadan/University College Hospital.…”

Section: Methodsmentioning

confidence: 99%

Association of Plasmodium Falciparum Chloroquine Resistance Transporter Variant T76 With Age-Related Plasma Chloroquine Levels

May

Meyer²

2003

The American Journal of Tropical Medicine and Hygiene

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Abstract. The mutation leading to the substitution of a threonine (T76) for a lysine at position 76 of the Plasmodium falciparum chloroquine resistance transporter (PfCRT) was genotyped in 100 Nigerian children with asymptomatic parasitemia. Isolates containing both pfcrt variants were found to harbor higher numbers of parasite clones (P < 0.002). The prevalence of the pfcrt T76 variant decreased with age (P < 0.0001) and increased with blood levels of chloroquine (CQ) (P < 0.0001). Whereas the K76 allele was more frequent in individuals without detectable plasma CQ levels (79.7%), only the pfcrt T76 variant was observed in children with CQ levels > 150 nmol/L. In individuals without detectable plasma CQ, the proportion of those with pfcrt T76 decreased from 60% in children < 2 years old to 23.5% in children Ն 6 years old (P < 0.01). The association of actual blood levels of CQ and the occurrence of pfcrt T76 underlines that the pfcrt T76 variant is in fact the mediator of CQ resistance.

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“…Notably, a feature of P. falciparum infections in many areas where this organism is endemic is the occurrence of multiclonal infections, which are characterized by a variety of mutations not only in the pfdhfr gene but also in other genes (9,10).…”

Section: Discussionmentioning

confidence: 99%

“…A common feature of P. falciparum malaria in areas where the disease is endemic is the occurrence of multiclonal infections (9,10), with individuals frequently and simultaneously being infected with the wild type and with strains exhibiting different drug resistance phenotypes. The quality of assays for the determination of resistant strains is, therefore, dependent on their ability to detect resistant clones of low parasitemia in multiclonal P. falciparum infections.…”

mentioning

confidence: 99%