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Malaria Risk among Internally Mobile Individuals and Heterogeneous Mobility Patterns in Two Hypoendemic Communities: Implications for Malaria Elimination in the Peruvian Amazon.

BACKGROUND: Human mobility is increasingly recognized as a key factor influencing malaria transmission dynamics, particularly in low-transmission settings approaching elimination. This study aimed to assess mobility patterns and their association with malaria risk in two hypoendemic communities in the Peruvian Amazon. METHOD: A longitudinal study was conducted in the communities of Libertad and Urcomira&#xf1;o (Maz&#xe1;n River basin). Monthly population screenings were combined with weekly active and passive case detection. A total of 678 individuals were enrolled. Mobility patterns were assessed through structured questionnaires, and social network analysis was used to characterize travel connections. Log-binomial regression analysis was applied to identify risk factors associated with malaria infection. RESULT: Internally, mobile individuals in Libertad showed a higher malaria incidence (>32.47 cases per 1,000 person-months) than those in Urcomira&#xf1;o (<10.15 cases per 1,000 person-months). Travel networks were mainly connected to Mazan district and Iquitos city, followed by local streams such as Armas and Arahuana. Mobility was primarily driven by family, administrative and occupational activities. Male sex (PR = 2.15, 95% CI: 1.37 - 3.37) and age &#x2265;15 years (PR = 1.98, 95% CI: 1.24 - 3.19) were significantly associated with malaria infection (p-value < 0.05). CONCLUSION: Internally mobile populations represent a key high-risk group sustaining malaria transmission in hypoendemic settings. Targeted interventions focusing on mobile individuals should be integrated into malaria elimination strategies in the Peruvian Amazon and similar endemic regions.

Malaria elimination

Malaria-GENOMAP: a web-based tool for exploring genomic variation of malaria parasites.

MOTIVATION: Malaria, caused by Plasmodium parasites, imposes a significant public health burden. While Plasmodium falciparum remains the primary target of elimination strategies due to its high mortality rate, lesser-known species such as P. malariae, P. vivax, and P. knowlesi continue to contribute to substantial human morbidity. Genomic approaches, including whole-genome sequencing, offer powerful tools for understanding the biology, transmission, and emerging drug resistance of these neglected Plasmodium species. However, there is an urgent need for informatic tools to summarize and visualize the high-dimensional and complex genomic data generated. RESULTS: We developed Malaria-GENOMAP, a user-friendly web-based tool, which integrates genomic variant data, such as allele frequencies, with geographical maps and chromosome-wide to gene views for in-depth exploration. The tool includes variation from P. knowlesi (n&#x2009;=&#x2009;139), P. malariae (n&#x2009;=&#x2009;158), P. ovale curtisi (n&#x2009;=&#x2009;36), P. ovale wallikeri (n&#x2009;=&#x2009;47), P. simium (n&#x2009;=&#x2009;38), and P. vivax (n&#x2009;=&#x2009;1359). It enables the investigation of population structure, geographic associations of mutations, and putative drug resistance markers, offering valuable insights for malaria control efforts. AVAILABILITY AND IMPLEMENTATION: Malaria-GENOMAP is available online at https://genomics.lshtm.ac.uk/malaria-genomaps.

Internet

[Malaria in children, with special reference to cerebral malaria (author's transl)].

Those who live in areas where Malaria is endemic, acquire immunity by continuous contact. This immunity cannot be acquired during a short holiday. Children in endemic areas acquire a more severe form of malaria during the period of developing immunity and more often suffer complications like acute hemolytic anemia and, in the case of plasmodium falciparum infection, cerebral malaria. This is a report of 39 cases of cerebral malaria which corresponds to an acute encephslopathy with high temperatures, generalized tonic-clonic spasms and unconsciousness. All children were between 6 months and 5 years old. Cerebral malaria at higher ages is rarely seen in Malawi. But its frequency depends on the intensity of endemic infection and the geographic distribution of the types of malaria. 11 (29%) of the 39 children died. Treatment was with chloroquine against which there was no resistance in East Africa for falciparum infections and with plasmaexpanders. In 1 case permanent neurologic changes a spastic cerebral paresis, were seen. Unconsciousness lasting more than 36 hours appears to be a bad prognostic sign. The CSF is clear and normal except for an occasional rise in protein never higher than 90 mg%.

Age Factors

Clinical and laboratory presentation of malaria: an analysis of one thousand subjects with malaria parasitaemia.

In the context of this study the ethnic origin of the patients revealed no noteworthy difference in the clinical reaction to the parasite; neither did age or sex of the patients. Any minor differences whcih appeared in length of history before seeking treatment and frequency of repeat attacks were more a reflection of the cultural pattern of response to illness (i.e. resort to traditional medicines) and the distance between the patient's home and the doctor rather than any altered response on the part of the host to the parasite. However, the fact that about 35 per cent of all the episodes had a history of eight or more days (about 10 per cent more than 30 days) suggest that more "malaria consciousness" is called for in what is after all an endemic malaria area. The value (and necessity) of repeated examination of the blood to detect the parasite is confirmed but it is also encouraging to note that in 84% of cases a single careful examination of the blood revealed the parasite. Since in 49% of our malaria episodes the patient was afebrile when the parasite was discovered, it is obvious that in outpatient practice especially blood should be examined when the patient presents for treatment, irrespective of the presence or absence of pyrexia. As always, a prerequisite to the diagnosis of malaria is an awareness of its possible presence.

Adolescent

Free-flow electrophoresis for the separation of malaria infected and uninfected mouse erythrocytes and for the isolation of free parasites (Plasmodium vinckei): a new rapid technique for the liberation of malaria parasites from their host cells.

After aggregation of erythrocytes from malaria infected mice, the parasites (Plasmodium vinckei) could be set free using gentle mechanical forces. The mixture of freed parasites, infected and non-infected erythrocytes, and membraneous material was separated by free-flow electrophoresis. The free parasites produced were very pure and infectious. Morphological and enzymatic data on the separated fractions are presented. Free-flow electrophoresis also allowed the separation of infected and uninfected erythrocytes.

Animals

The chemotherapy of rodent malaria, XXVI. The potential value of WR 122,455 (a 9-phenanthrenemethanol) against drug-resistant malaria parasites.

The phenanthrenemethanol compound WR 122,455 is an effective blood schizontocide against lines of Plasmodium berghei that are highly resistant to primaquine, sulphonamides, pyrimethamine and cycloguanil. It is also active against the NS line that is moderately resistant to chloroquine. WR 122,455 is inactive against the RC line which is highly resistant to chloroquine. Resistance to WR 122,455 is fairly readily developed by the drug-sensitive N strain of P. berghei, using a relapse technique. Resistance develops very readily to the NS line of P. berghei. Both resistant lines exhibit cross-resistance to quinine, but a roughly normal response to chloroquine, primaquine, sulphonamides, dapsone, pyrimethamine and cycloguanil. Resistance to WR 122,455 is stable through cyclical transmission and through cryopreservation, as well as in the absence of drug selection pressure. The resistant parasites have an essentially normal morphology and virulence. A warning is given against the widescale use of WR 122,455 or similar new drugs for human malaria other than in a suitable combination, in order to minimize the danger of the development of resistance to them.

Animals

The seroepidemiology of malaria in Middle America. IV. Passage of malaria antibodies from mothers to infants.

In an area of El Salvador moderately endemic for malaria, use of the indirect fluorescent antibody test (IFA) showed that 44% of the infants born to mothers who had IFA responses to Plasmodium vivax of 1:20 or higher during the latter part of their pregnancy had positive IFA responses of 1:10 or higher to this antigen. No serum from an infant was positive in the absence of some level of malarial response in the mother.

Antibodies

Longitudinal malaria studies in rural Northeast Thailand. Chloroquine treatment of falciparum malaria infections.

The efficacy of chloroquine in the treatment of falciparum malaria was studied in two villages in Northeast Thailand, an area endemic for chloroquine-resistant falciparum infections. Chloroquine did not appear to reduce the duration or density of parasitemias experienced by asymptomatic villagers, but did benefit, usually temporarily, many subjects with symptomatic or high-density infections. These observations suggest that the high prevalence of chloroquine-resistant infections in the villages is similar to data from the hospital and clinics serving the area. The question whether chloroquine should remain available to this population should be evaluated.

Adult

[Malaria hypothesis--the significance of the hereditary red cell traits Hb S and glucose-6-phosphate dehydrogenase deficiency in malaria (author's transl)].

The high frequencies of the Hb S and G6PD-deficiency genes in the tropics are explained by their relative resistance against malarial infection. They may confer advantage through lower infection rates or through lower parasitaemia. There is evidence that heterozygote carriers of these genes are partially protected. The mechanism of resistance is known for Hb S but not completely understood for the G6PD-deficiency gene. Other red cell factors are discussed with respect to innate resistance against malaria.

Adult