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Cold Spring Harbor Perspectives in... Jan 2018In the mosquito-human life cycle, the six species of malaria parasites infecting humans (, , , , , and ) undergo 10 or more morphological states, replicate from single... (Review)
Review
In the mosquito-human life cycle, the six species of malaria parasites infecting humans (, , , , , and ) undergo 10 or more morphological states, replicate from single to 10,000+ cells, and vary in total population from one to many more than 10 organisms. In the human host, only a small number of these morphological stages lead to clinical disease and the vast majority of all malaria-infected patients in the world produce few (if any) symptoms in the human. Human clinical disease (e.g., fever, anemia, coma) is the result of the parasite preprogrammed biology in concert with the human pathophysiological response. Caveats and corollaries that add variation to this host-parasite interaction include parasite genetic diversity of key proteins, coinfections, comorbidities, delays in treatment, human polymorphisms, and environmental determinants.
Topics: Female; Humans; Malaria; Malaria, Cerebral; Placenta; Plasmodium; Pregnancy; Species Specificity; Virulence Factors
PubMed: 28533315
DOI: 10.1101/cshperspect.a025569 -
Le Infezioni in Medicina Jun 2016Malaria, the most common parasitic disease in the world, is transmitted to the human host by mosquitoes of the genus Anopheles. The transmission of malaria requires the... (Review)
Review
Malaria, the most common parasitic disease in the world, is transmitted to the human host by mosquitoes of the genus Anopheles. The transmission of malaria requires the interaction between the host, the vector and the parasite.The four species of parasites responsible for human malaria are Plasmodium falciparum, Plasmodium ovale, Plasmodium malariae and Plasmodium vivax. Occasionally humans can be infected by several simian species, like Plasmodium knowlesi, recognised as a major cause of human malaria in South-East Asia since 2004. While P. falciparum is responsible for most malaria cases, about 8% of estimated cases globally are caused by P. vivax. The different Plasmodia are not uniformly distributed although there are areas of species overlap. The life cycle of all species of human malaria parasites is characterised by an exogenous sexual phase in which multiplication occurs in several species of Anopheles mosquitoes, and an endogenous asexual phase in the vertebrate host. The time span required for mature oocyst development in the salivary glands is quite variable (7-30 days), characteristic of each species and influenced by ambient temperature. The vector Anopheles includes 465 formally recognised species. Approximately 70 of these species have the capacity to transmit Plasmodium spp. to humans and 41 are considered as dominant vector capable of transmitting malaria. The intensity of transmission is dependent on the vectorial capacity and competence of local mosquitoes. An efficient system for malaria transmission needs strong interaction between humans, the ecosystem and infected vectors. Global warming induced by human activities has increased the risk of vector-borne diseases such as malaria. Recent decades have witnessed changes in the ecosystem and climate without precedent in human history although the emphasis in the role of temperature on the epidemiology of malaria has given way to predisposing conditions such as ecosystem changes, political instability and health policies that have reduced the funds for vector control, combined with the presence of migratory flows from endemic countries.
Topics: Animals; Anopheles; Climate; Climate Change; Disease Reservoirs; Endemic Diseases; Female; Global Health; Hominidae; Humans; Insect Vectors; Life Cycle Stages; Malaria; Plasmodium; Population Dynamics; Primate Diseases; Species Specificity; Urbanization
PubMed: 27367318
DOI: No ID Found -
The American Journal of Tropical... Jul 2018Important strides have been made within the past decade toward malaria elimination in many regions, and with this progress, the feasibility of eradication is once again... (Review)
Review
Important strides have been made within the past decade toward malaria elimination in many regions, and with this progress, the feasibility of eradication is once again under discussion. If the ambitious goal of eradication is to be achieved by 2040, all species of infecting humans will need to be targeted with evidence-based and concerted interventions. In this perspective, the potential barriers to achieving global malaria elimination are discussed with respect to the related diversities in host, parasite, and vector populations. We argue that control strategies need to be reorientated from a sequential attack on each species, dominated by to one that targets all species in parallel. A set of research themes is proposed to mitigate the potential setbacks on the pathway to a malaria-free world.
Topics: Animals; Anopheles; Antimalarials; Chloroquine; Disease Eradication; Host-Parasite Interactions; Humans; Malaria; Malaria, Falciparum; Malaria, Vivax; Mosquito Vectors; Plasmodium falciparum; Plasmodium knowlesi; Plasmodium malariae; Plasmodium ovale; Plasmodium vivax; Primaquine
PubMed: 29761762
DOI: 10.4269/ajtmh.17-0869 -
Lancet (London, England) Sep 2013Malaria-eliminating countries achieved remarkable success in reducing their malaria burdens between 2000 and 2010. As a result, the epidemiology of malaria in these... (Review)
Review
Malaria-eliminating countries achieved remarkable success in reducing their malaria burdens between 2000 and 2010. As a result, the epidemiology of malaria in these settings has become more complex. Malaria is increasingly imported, caused by Plasmodium vivax in settings outside sub-Saharan Africa, and clustered in small geographical areas or clustered demographically into subpopulations, which are often predominantly adult men, with shared social, behavioural, and geographical risk characteristics. The shift in the populations most at risk of malaria raises important questions for malaria-eliminating countries, since traditional control interventions are likely to be less effective. Approaches to elimination need to be aligned with these changes through the development and adoption of novel strategies and methods. Knowledge of the changing epidemiological trends of malaria in the eliminating countries will ensure improved targeting of interventions to continue to shrink the malaria map.
Topics: Adolescent; Adult; Africa South of the Sahara; Aged; Civilization; Cluster Analysis; Cross-Sectional Studies; Developing Countries; Emigration and Immigration; Female; Humans; Malaria; Malaria, Falciparum; Malaria, Vivax; Male; Middle Aged; Occupational Diseases; Plasmodium malariae; Plasmodium ovale; Population Dynamics; Young Adult
PubMed: 23594387
DOI: 10.1016/S0140-6736(13)60310-4 -
Proceedings of the National Academy of... Oct 2020Asymptomatic carriers of parasites hamper malaria control and eradication. Achieving malaria eradication requires ultrasensitive diagnostics for low parasite density...
Asymptomatic carriers of parasites hamper malaria control and eradication. Achieving malaria eradication requires ultrasensitive diagnostics for low parasite density infections (<100 parasites per microliter blood) that work in resource-limited settings (RLS). Sensitive point-of-care diagnostics are also lacking for nonfalciparum malaria, which is characterized by lower density infections and may require additional therapy for radical cure. Molecular methods, such as PCR, have high sensitivity and specificity, but remain high-complexity technologies impractical for RLS. Here we describe a CRISPR-based diagnostic for ultrasensitive detection and differentiation of , , , and , using the nucleic acid detection platform SHERLOCK (specific high-sensitivity enzymatic reporter unlocking). We present a streamlined, field-applicable, diagnostic comprised of a 10-min SHERLOCK parasite rapid extraction protocol, followed by SHERLOCK for 60 min for species-specific detection via fluorescent or lateral flow strip readout. We optimized one-pot, lyophilized, isothermal assays with a simplified sample preparation method independent of nucleic acid extraction, and showed that these assays are capable of detection below two parasites per microliter blood, a limit of detection suggested by the World Health Organization. Our and assays exhibited 100% sensitivity and specificity on clinical samples (5 and 10 samples). This work establishes a field-applicable diagnostic for ultrasensitive detection of asymptomatic carriers as well as a rapid point-of-care clinical diagnostic for nonfalciparum malaria species and low parasite density infections.
Topics: Carrier State; Clustered Regularly Interspaced Short Palindromic Repeats; Diagnostic Techniques and Procedures; Genetic Techniques; Humans; Malaria; Plasmodium
PubMed: 32958655
DOI: 10.1073/pnas.2010196117 -
Parasites & Vectors Feb 2022Plasmodium ovale is a neglected malarial parasite that can form latent hypnozoites in the human liver. Over the last decade, molecular surveillance studies of...
BACKGROUND
Plasmodium ovale is a neglected malarial parasite that can form latent hypnozoites in the human liver. Over the last decade, molecular surveillance studies of non-falciparum malaria in Africa have highlighted that P. ovale is circulating below the radar, including areas where Plasmodium falciparum is in decline. To eliminate malaria where P. ovale is endemic, a better understanding of its epidemiology, asymptomatic carriage, and transmission biology is needed.
METHODS
We performed a pilot study on P. ovale transmission as part of an ongoing study of human-to-mosquito transmission of P. falciparum from asymptomatic carriers. To characterize the malaria asymptomatic reservoir, cross-sectional qPCR surveys were conducted in Bagamoyo, Tanzania, over three transmission seasons. Positive individuals were enrolled in transmission studies of P. falciparum using direct skin feeding assays (DFAs) with Anopheles gambiae s.s. (IFAKARA strain) mosquitoes. For a subset of participants who screened positive for P. ovale on the day of DFA, we incubated blood-fed mosquitoes for 14 days to assess sporozoite development.
RESULTS
Molecular surveillance of asymptomatic individuals revealed a P. ovale prevalence of 11% (300/2718), compared to 29% (780/2718) for P. falciparum. Prevalence for P. ovale was highest at the beginning of the long rainy season (15.5%, 128/826) in contrast to P. falciparum, which peaked later in both the long and short rainy seasons. Considering that these early-season P. ovale infections were low-density mono-infections (127/128), we speculate many were due to hypnozoite-induced relapse. Six of eight P. ovale-infected asymptomatic individuals who underwent DFAs successfully transmitted P. ovale parasites to A. gambiae.
CONCLUSIONS
Plasmodium ovale is circulating at 4-15% prevalence among asymptomatic individuals in coastal Tanzania, largely invisible to field diagnostics. A different seasonal peak from co-endemic P. falciparum, the capacity to relapse, and efficient transmission to Anopheles vectors likely contribute to its persistence amid control efforts focused on P. falciparum.
Topics: Animals; Anopheles; Cross-Sectional Studies; Humans; Malaria, Falciparum; Mosquito Vectors; Pilot Projects; Plasmodium falciparum; Plasmodium ovale; Prevalence; Tanzania
PubMed: 35164867
DOI: 10.1186/s13071-022-05181-2