Idiopathic thrombocytopenic purpura due to vivax malaria in the Brazilian Amazon.

We describe a rare case of idiopathic thrombocytopenic purpura (ITP) triggered by Plasmodium vivax infection. The patient developed thrombocytopenia and bleeding associated with three episodes of malaria, and became dependent on corticosteroid therapy. The mechanisms by which this parasite evokes thrombocytopenia remain obscure.

A probability model of vector behavior: effects of DDT repellency, irritancy, and toxicity in malaria control.

A probability model of how DDT residues may function within a malaria control program is described. A step-wise organization of endophagic behaviors culminates in a vector acquiring a human blood meal inside the house. Different vector behaviors are described, epidemiologically defined, temporally sequenced, and quantified with field data. Components of vector behavior and the repellent, irritant, and toxic actions of insecticide residues are then assembled into a probability model. The sequence of host-seeking behaviors is used to partition the total impact of sprayed walls according to the three chemical actions. Quantitatively, the combined effect of repellency and irritancy exert the dominant actions of DDT residues in reducing man-vector contact inside of houses. These relationships are demonstrated with published and unpublished data for two separate populations of Anopheles darlingi, for Anopheles gambiae and Anopheles funestus in Tanzania, and Anopheles punctulatus in New Guinea.

[Malaria treatment with artesunate (retocaps) in children of the Brazilian Amazon]. / Tratamento da malária com artesunate (retocaps) em crianças da Amazônia brasileira.

We evaluated the clinical and therapeutic response to artesunate retocaps in 32 children admitted to the Fundação de Medicina Tropical do Amazonas (Amazon Foundation of Tropical Medicine) with clinical characteristics of moderate and severe malaria. Of these, 29 were infected with P. falciparum and 3 with P. vivax. They improved clinically 24 hours after the beginning of therapy, with 33. 3% of patients without fever, and after 48 hours, 77.2% of the children had no fever. The monitoring of asexual forms of the parasites showed that on D2 (day 2 of treatment) 58.6% of children with P. falciparum infection had no more parasites in the blood stream, on D4 all children had negative slides both for P. falciparum and for P. vivax infection. In a long-term follow up, we found 66.6% recrudescence in P. falciparum patients. The results enabled the conclusion that artesunate retocaps are efficient in practice and their use rapidly reduces the parasitemia and improves the patients' clinical picture. However, in P. falciparum malaria the recrudescence rate was very high. We observed no side effects from this drug.

Plasmodium falciparum infection in the pregnant patient.

Malaria should be considered a risk factor in women who are pregnant, principally when the infection is Plasmodium falciparum. Moreover, the risk is greater if the woman is pregnant for the first time; if she has no immunity for malaria; if the diagnosis is made late; or if P. falciparum shows resistance to antimalarial drugs. This article presents the most significant aspects of P. falciparum malaria during pregnancy, including information about treatments and prophylaxis.

Description of a possible clonal expansion of Plasmodium vivax in Manaus-Amazonas-Brazil.

Atypical P. vivax cases reported in Manaus municipality led us to detect a genetic isolate of P. vivax. Variable regions of SSUrRNA were examined from the initial time of infection and in the two recrudescences/relapses from a patient exhibiting chloroquine and primaquine resistance. A unique isolate, found at all stages of infection, suggests the presence of a clonal expansion.

Plasmodium vivax resistance to chloroquine (R2) and mefloquine (R3) in Brazilian Amazon region.

We report for the first time a patient with malaria due to Plasmodium vivax who showed R2 resistance to chloroquine and R3 resistance to mefloquine in the Brazilian Amazon region based on WHO clinical criteria for diagnosis of malaria resistance. Failure was observed with unsupervised oral chloroquine, chloroquine under rigorous supervision and mefloquine in the same scheme. Finally, the patient was cured with oral artesunate.

Malaria diagnosis: standardization of a polymerase chain reaction for the detection of Plasmodium falciparum parasites in individuals with low-grade parasitemia.

In Brazil, no study has been done concerning the detection of malaria parasites by polymerase chain reaction (PCR) related to the diagnosis of Plasmodium falciparum malaria. In the present report we describe a highly sensitive methodology for malaria diagnosis using a nested PCR method based on amplification of the p126 P. falciparum gene detected by simple ethidium bromide staining. The P. falciparum Palo Alto strain (culture samples) was serially diluted in blood from an uninfected donor to a final level of parasitemia corresponding to 10(-8)% and was processed for PCR amplification. In each of these dilutions a parasitological examination was performed to compare the sensitivity with that of PCR amplification. Blood samples (field samples) were obtained from 51 malarious patients with positive thick blood smears (TBS) who were living in endemic regions of the Brazilian Amazon. They corresponded to 42 P. falciparum and 9 P. vivax cases, with parasitemia levels ranging from only 16 to 20,200 parasites/microliter for P. falciparum disease and from 114 to 11,000 parasites/microliter for P. vivax malaria. We demonstrate that the use of nested PCR allows the detection of 0.005 parasites/microliter without the use of radioactive material. The use of a 1-ml sample volume and the organic DNA extraction method should be suitable in blood banks and for the evaluation of patients during and after drug treatment.

A field trial with Lambda-cyhalothrin (ICON) for the intradomiciliary control of malaria transmitted by Anopheles darlingi root in Rondonia, Brazil.

A two stage field trial comparing the effects of Lambdacyhalothrin (ICON) and DDT when used as residual sprays on the inside surfaces of houses, was conducted in the Machadinho and Jaru areas of Rodonia, Brazil, in 1987 and 1988. In 1987 houses along two 16 km contiguous stretches of a main and a side road were sprayed and the effects on malaria vectors monitored for the succeeding year. In the second stage approximately 55,000 houses in both districts were sprayed with ICON and the effect on malaria incidence measured by passive case detection. Of the eleven species of Anopheles caught in indoor and peridomiciliary collections A. darlingi was the commonest and is recognised as the most important vector in Brazil. ICON at either of two concentrations in bioassays killed more mosquitoes than DDT at each test from seven to twelve months after spraying. A rise in the number of A. darlingi collected eight months after spraying with DDT was not so marked in the ICON areas. Side effects of the insecticide were limited. The number of reported Plasmodium falciparum cases in the second phase declined 76% in Machadinho after spraying with ICON to 2851 cases. In Jaru there was a 28% reduction. The observed efficacy of the insecticide, its ready acceptance by the local populace, and its cost effectiveness make it a more useful insecticide for anti-malaria campaigns than DDT.

[Response of Anopheles darlingi to spraying with DDT in Amazonas, Brazil]. / Respuesta de Anopheles darlingi al rociamiento con DDT en Amazonas, Brasil.

To investigate the effectiveness of the malaria control program, the behavior of Anopheles darlingi females was studied following spraying of DDT on the walls of house-holds along the Ituxi river in the state of Amazonas, Brazil. The study was carried out on two four-walled dwellings, one of which was sprayed with 2 g of DDT per m2 of wall. Three methods were used to study the mosquitoes' activity before and immediately after the spraying, as well as at 2 and 12 months post-spraying. These methods were: capturing the mosquitoes in the act of resting on human baits, capturing them in traps as they entered or exited the dwellings, and liberating females tagged with fluorescent powder inside the house and then following them with ultraviolet light. Immediately after the spraying, the females stopped going in and out of the house and ceased biting inside the sprayed dwelling. In addition, the tagged females that had been set loose inside the house fled almost immediately. These phenomena were not observed in the unsprayed dwelling. The reaction of the A. darlingi to spraying is considered to indicate true repellency and not simply irritation from contact. Since the dwellings in the locality have only 2.2 walls on average, the persistence of malaria in the territory could be due to the type of household construction.

Behavioral response of Anopheles darlingi to DDT-sprayed house walls in Amazonia.

The behavioral response of Anopheles darlingi females to spraying of house walls with DDT was studied along the Ituxi River in Amazonas, Brazil, using a house sprayed with 2 g DDT per square meter of wall surface and an untreated house serving as a control. It was found that hardly any An. darlingi females entered, exited, or took blood meals inside the treated house after it was sprayed with DDT, and that specimens marked and released inside the house tended to depart immediately. This behavior appears to constitute true repellency rather than contact irritability. Since the typical house in the vicinity of the study site had only two walls, the persistence of malaria in the local area was probably due to home construction practices.

Capture-recapture studies with the South American malaria vector Anopheles darlingi, Root.

A capture-recapture experiment was undertaken in October 1987, in the Jaru district of Rondonia, Brazil, with the malaria vector Anopheles darlingi. On two consecutive nights, 160 blood-fed, 78 unfed biting and 81 unfed resting mosquitoes were released. Recapture rates of 12-19% and survival rates of 0.59-0.57 per oviposition cycle were obtained for all releases, indicating that blood-feeding was not an obstacle for this population, which had a high vectorial capacity. Two A. darlingi were collected 7.2 km from the release site nine days after release. In contrast, recapture rates for 259 anophelines of nine other species released were only 2.3%. These other species also had a limited flight time and range in comparison with A. darlingi, which indicates that the latter is the only malaria vector of importance in this part of Brazil.

The house-frequenting, host-seeking and resting behavior of Anopheles darlingi in southeastern Amazonas, Brazil.

Studies on the behavior of Anopheles darlingi were conducted at a site along the Ituxi River, Amazonas, Brazil. Patterns of host-seeking activity inside and outside a single-walled house both presented activity peaks at sunset and sunrise, but biting activity inside a four-walled house peaked after sunset then gradually decreased during the night. Major movements of females into and out of the four-walled house occurred at sunset and sunrise, respectively. Marked engorged and unengorged females released indoors were observed to preferentially rest on the ceiling. These behavior patterns were confirmed by replication and/or with more than one sampling technique or study method. Additional observations on exit sites, spatial distribution of resting females and physiological condition of exiting specimens were recorded.