A retrospective examination of sporozoite- and trophozoite-induced infections with Plasmodium falciparum in patients previously infected with heterologous species of Plasmodium: effect on development of parasitologic and clinical immunity.
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A retrospective examination was made to determine parasitemia and episodes of fever in 97 patients, previously infected with Plasmodium malariae, P. ovale, and/or P. vivax, who were reinfected with P. falciparum for treatment of neurosyphilis, the standard treatment at the time. Data were collected at the National Institutes of Health laboratories in Columbia, South Carolina and Milledgeville, Georgia during the period 1940 to 1963. Results were compared with observations recorded for patients following primary infection with P. falciparum. The mean daily percentage of patients with fever > or = 101 degrees F during the first 20 days of primary infection with P. falciparum was 42.4; the percentage with fever > or = 104 degrees F was 19.9%. Those previously infected with P. ovale, P. vivax, and P. malariae had mean daily percentages of fever > or = 101 degrees F and > or = 104 degrees F of 39.1% and 14.8%, 39.1% and 19.4%, and 28.4%, and 11.3%, respectively. Previous infection with P. ovale or P. vivax had little, if any, effect on subsequent clinical malaria due to P. falciparum, whereas infection with P. malariae resulted in reduced frequencies of fever. A similar comparison was made for parasite counts > or = 1,000/microl and > 10,000/microl. The percentages for 268 patients during the first 20 days of primary infection with P. falciparum parasite counts > or = 1,000/microl and > or = 10,000/microl were 58.2% and 29.9%, respectively. Those previously infected with P. ovale, P. vivax, and P. malariae had mean daily percentages of parasitemia > or = 1,000/microl and > or = 10,000/microl of 58.0% and 24.3%, 57.3% and 31.1%, and 45.9% and 19.0%, respectively. Previous infection with P. malariae resulted in a reduction in the frequency of high-density parasitemia (> or = 10,000/microl) as well as an asexual parasite count > or = 1,000/microl. These results suggest that P. falciparum and P. malariae share common antigens that are able to induce parasitologic and clinical protection when infection with P. falciparum follows that with P. malariae. The results did not suggest that protection to P. falciparum is provided by previous infection with P. ovale or P. vivax. (+info)
Breeding structure of the sand fly Lutzomyia longipalpis (Lutz & Neiva) in Brazil.
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Eleven populations of Lutzomyia longipalpis (Lutz & Neiva), the sand fly vector of Leishmania chagasi, from different areas of Brazil were analyzed for genetic variation at 16 enzyme loci. In this region, the prevalence of visceral leishmaniasis (VL) caused by L. chagasi is spotty and reproductive isolation among populations of Lu. longipalpis has been reported. It is thought that morphologically similar cryptic species with varying vectorial capacity may be responsible for the discontinuous distribution of VL. The aim was to study the genetic structure of populations within this region and to identify demes that may represent sibling species. Genotypic frequencies within populations were in close compliance to Hardy-Weinberg expectations, suggesting there are no sympatric species among these 11 populations. Levels of genetic distance between pairs of populations were very low (< 0.03), consistent with local populations within a single sand fly species. When genotypic frequency data for all populations were pooled, 9 of the 13 polymorphic loci deviated from Hardy-Weinberg expectations, indicating some degree of genetic substructuring. Estimates of effective migration rates (N(e)m) among all populations were low, 2.73, suggesting that gene flow is restricted among populations, which is probably the reason for the observed genetic substructuring. (+info)
Epidemic O'Nyong-Nyong fever in southcentral Uganda, 1996-1997: entomologic studies in Bbaale village, Rakai District.
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Entomologic studies were conducted between January 27 and February 2, 1997, in Bbaale village in southcentral Uganda during an o'nyong-nyong (ONN) virus epidemic, which began in mid 1996 and continued into 1997. The objectives were to confirm the role of anophelines in ONN virus transmission and to examine other mosquito species as epidemic vectors of ONN virus. Of 10,050 mosquitoes collected using light traps and pyrethrum knockdown sprays, Anopheles (Cellia) funestus Giles was presumed to be the principal vector because it was the most abundant mosquito species from which a strain of ONN virus was isolated. This virus was isolated for the first time from a culicine species, Mansonia (Mansonioides) uniformis Theobald. Bwamba virus and Nyando virus were also isolated from An. funestus. (+info)
Density of sand flies (Diptera: psychodidae) in domestic and wild animal shelters in an area of visceral Leishmaniasis in the state of Rio Grande do Norte, Brazil.
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The objective of the present study was to determine the association of sand flies with the presence of domestic and wild animals in the peridomiciliary area. The sand flies were collected using direct aspiration and CDC light traps placed in animal shelters. The results suggest that different sand flies species have different behavioral characteristics in an apparent preference for animal baits and that Lutzomyia longipalpis and Lu. evandroi were the most eclectic species regarding their biotope choice. Lu. longipalpis showed a distinct preference for horses and Lu. evandroi for armadillos. (+info)
Changes in the sexual dimorphism of triatominae in the transition from natural to artificial habitats.
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A shift from large to small average sizes was observed in Triatoma infestans and Rhodnius domesticus between field and domestic (or laboratory) conditions of life. It was more pronounced in the female specimens, leading to a subsequent reduction of sexual size dimorphism. This feature is discussed in terms of genetic and populational changes occurring from natural to artificial habitats, in particular those related to population densities. Sexual size dimorphism is then recommended as a new character to be used in the study of species of Triatominae adapting to domestic ecotopes. (+info)
Chagas disease in an area of recent occupation in Cochabamba, Bolivia.
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INTRODUCTION: A descriptive, entomological and seroepidemiological study on Chagas disease was conducted in a place of recent occupation on the outskirts of Cochabamba, Bolivia: Avaroa/Primer de Mayo (population:3,000), where the socio-economic level is low and no control measures have been made available. METHODS: The immunofluorescent antibody test (IFAT) was used for IgG and IgM anti-Trypanosoma cruzi antibodies in filter paper bloodspot eluates from 128 subjects (73 females, 55 males) selected by systematic sampling. Concerning each subject age, gender, birthplace, occupation, duration of residence and building materials used in their houses were recorded. Vectors were captured both in domestic and peridomestic environments. RESULTS: Seropositive, 12.5% (16/128): females, 15.1% (11/73); males, 9.1% (5/55). Average time of residence: 6.1 years for the whole population sample and 7.4 years for the seropositive subjects. Most houses had adobe walls (76. 7%, n= 30), galvanized iron rooves (86.7%) and earthen floors (53. 4%) 80% of the walls had crevices. One hundred forty seven specimens of Triatoma infestans were captured, of which 104 (70.7%) were domestic, and 1 peridomestic Triatoma sordida. Precipitin host identification: birds, 67.5%; humans, 27.8%; rodents, 11.9%; dogs, 8. 7%; cats, 1.6%. House infestation and density indices were 53.3 and 493.0 respectively. We found 21 (14.3%) specimens of T. infestans infected with trypanosomes, 18 (85.7%) of which in domestic environments. DISCUSSION: The elements for the vector transmission of Chagas disease are present in Avaroa/Primer de Mayo and the ancient custom of keeping guinea pigs indoors adds to the risk of human infection. In neighboring Cochabamba, due to substandard quality control, contaminated blood transfusions are not infrequent, which further aggravates the spread of Chagas disease. Prompt action to check the transmission of this infection, involving additionally the congenital and transfusional modes of acquisition, is required. (+info)
Contribution to the sand fly fauna (Diptera: Phlebotominae) of Rio Grande do Sul, Brazil and Leishmania (Viannia) infections.
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American cutaneous leishmaniasis (ACL) is endemic in the State of Rio Grande do Sul, Brazil. As reports of nearby hospitals suggest, the Parque Estadual do Turvo seems to serve as a source for the disease. During three months from November 1996 to February 1997 we collected, in this park, 2,228 sandflies (10 Lutzomyia species and 2 6species). We applied the polymerase chain reaction to 920 females which belong to the following species: Lutzomyia migonei, Lu. pessoai, Lu. fischeri, Lu. misionensis, Lu. lanei, Lu. neivai, Lu. shannoni, and Lu. monticola, in an attempt to verify natural infection by Leishmania (Viannia), the causative agent of ACL. Le. (Viannia) infections were demonstrated by DNA amplification from two Lu. pessoai and one Lu. misionensis female. Lu. pessoai have been found with leptomonas in the gut believed to be Le. (V.) braziliensis in other endemic areas of northeastern and southeastern Brazil. However, Lu. misionensis has never been found carrying a natural infection of Le. (Viannia). (+info)
Bloodmeal microfilariae density and the uptake and establishment of Wuchereria bancrofti infections in Culex quinquefasciatus and Aedes aegypti.
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The relationship between ingestion of microfilariae (mf), production of infective larvae (L3) and mf density in human blood has been suggested as an important determinant in the transmission dynamics of lymphatic filariasis. Here we assess the role of these factors in determining the competence of a natural vector Culex quinquefasciatus and a non vector Aedes aegypti to transmit Wuchereria bancrofti. Mosquitoes were infected via a membrane feeding procedure. Both mosquito species ingested more than the expected number of microfilariae (concentrating factor was 1.28 and 1.81 for Cx. quinquefasciatus and Ae. aegypti, respectively) but Cx. quinquefasciatus ingested around twice as many mf as Ae. aegypti because its larger blood meal size. Ae. aegypti showed a faster mf migration capacity compared to Cx. quinquefasciatus but did not allow parasite maturation under our experimental conditions. Similar proportions of melanized parasites were observed in Ae. aegypti (2. 4%) and Cx. quinquefasciatus (2.1%). However, no relationship between rate of infection and melanization was observed. We conclude that in these conditions physiological factors governing parasite development in the thorax may be more important in limiting vectorial competence than the density of mf ingested. (+info)