RESUMO
Epidemics of visceral leishmaniasis (VL) in major Brazilian cities are new phenomena since 1980. As determinants of transmission in urban settings probably operate at different geographic scales, and information is not available for each scale, a multilevel approach was used to examine the effect of canine infection and environmental and socio-economic factors on the spatial variability of incidence rates of VL in the city of Teresina. Details on an outbreak of greater than 1200 cases of VL in Teresina during 1993-1996 were available at two hierarchical levels: census tracts (socio-economic characteristics, incidence rates of human VL) and districts, which encompass census tracts (prevalence of canine infection). Remotely sensed data obtained by satellite generated environmental information at both levels. Data from census tracts and districts were analysed simultaneously by multilevel modelling. Poor socio-economic conditions and increased vegetation were associated with a high incidence of human VL. Increasing prevalence of canine infection also predicted a high incidence of human VL, as did high prevalence of canine infection before and during the epidemic. Poor socio-economic conditions had an amplifying effect on the association between canine infection and the incidence of human VL. Focusing interventions on areas with characteristics identified by multilevel analysis could be a cost-effective strategy for controlling VL. Because risk factors for infectious diseases operate simultaneously at several levels and ecological data usually are available at different geographical scales, multilevel modelling is a valuable tool for epidemiological investigation of disease transmission.
Assuntos
Leishmaniose Visceral/epidemiologia , Modelos Estatísticos , Animais , Brasil/epidemiologia , Surtos de Doenças , Cães , Humanos , Incidência , Prevalência , Fatores de Risco , Fatores Socioeconômicos , População UrbanaRESUMO
First noted in the city of Teresina in 1981, the last decades have witnessed a remarkable increase in urban transmission of American visceral leishmaniasis (VL) in many Brazilian cities. Teresina, the site of this study, has faced two large outbreaks of VL. The first occurred from 1981-1985 when almost 1000 new cases were reported. The second started in the 1990s, and between 1993 and 1996 more than 1200 new cases were detected. This report describes the prevalence of infection with Leishmania chagasi in Teresina at the end of the second outbreak and gives estimates of the number of people who became infected during the epidemic. Between June 1995 and May 1996, 200 households were chosen at random from a list of addresses covering about 93% of Teresina's urban households. In each household, one person over the age of 1 year was screened for Leishmania antibodies and skin-tested. Nearly 50% of persons had a positive leishmanin reaction, but only 13.9% had detectable antibodies to L. chagasi. While prevalence estimates based on the leishmanin skin-test increased with age (P<0.001), those based on serological tests showed a lesser, and non significant, variation with age (P=0.31). Using a geometric growth equation, and assuming that the annual distribution of clinical cases may serve as an approximation to what would have been the distribution of infections by year, we estimated that over 320000 persons were infected during the epidemic. Little is known about the epidemiology of VL in urban areas, where social networks, population density, and relationships of housing with the natural environment are more varied and complex than in the rural scene. In those areas, control interventions have failed to eliminate transmission of the parasite and prevent new epidemics. Further epidemiological studies of VL in urban areas might be needed to inform control actions.
Assuntos
Surtos de Doenças , Leishmaniose Visceral/epidemiologia , Adolescente , Adulto , Anticorpos Antiprotozoários/isolamento & purificação , Brasil/epidemiologia , Criança , Pré-Escolar , Humanos , Lactente , Leishmaniose Visceral/imunologia , Prevalência , Estudos Soroepidemiológicos , População UrbanaRESUMO
The failure of control programs for visceral leishmaniasis (VL) that depend on elimination of infected dogs suggests that other reservoir hosts may participate in the transmission cycle. To determine whether persons infected with Leishmania chagasi can infect the vector sand fly, laboratory-reared Lutzomyia longipalpis were allowed to feed on Brazilian subjects with active, cured, and asymptomatic VL and on asymptomatic residents of houses of persons with active VL. Of 3747 insects that had fed, 26 acquired infection from 11 of the 44 persons with active VL, but none acquired infection from the 137 asymptomatic persons. Among persons <4 years old with active VL, a history of diarrhea and higher peripheral blood neutrophil counts were independent predictors of infectivity. Further experiments using larger numbers of insects are necessary to evaluate the reservoir competence of persons with asymptomatic infections, who represent a large segment of the population of several Brazilian cities.
Assuntos
Leishmania , Leishmaniose Visceral/transmissão , Adolescente , Animais , Brasil , Criança , Pré-Escolar , Reservatórios de Doenças , Cães , Ensaio de Imunoadsorção Enzimática , Humanos , Lactente , Reação em Cadeia da Polimerase , PsychodidaeRESUMO
In 1545, twenty-four years after the Spanish conquest of the Aztec empire, an epidemic of a malignant form of a hemorrhagic fever appeared in the highlands of Mexico. The illness was characterized by high fever, headache, and bleeding from the nose, ears, and mouth, accompanied by jaundice, severe abdominal and thoracic pain as well as acute neurological manifestations. The disease was highly lethal and lasted three to four days. It attacked primarily the native population, leaving the Spaniards almost unaffected. The hemorrhagic fevers remained in the area for three centuries and the etiologic agent is still unknown. In this report we describe, and now that more information is available, analyze four epidemics that occurred in Mexico during the colonial period with a focus on the epidemic of 1576 which killed 45% of the entire population of Mexico. It is important to retrieve such diseases and the epidemics they caused from their purely historical context and consider the reality that if they were to reemerge, they are potentially dangerous.
Assuntos
Surtos de Doenças/história , Febre Hemorrágica Americana/história , Febre Hemorrágica Americana/epidemiologia , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , Humanos , México/epidemiologiaRESUMO
Malaria parasites are genetically diverse at all levels of endemicity. In contrast, the merozoite surface protein (MSP) alleles in samples from 2 isolated populations of Yanomami Amerindians during an epidemic of Plasmodium falciparum were identical. The nonvariable restriction fragment length polymorphism patterns further suggested that the sequential outbreak comprised only a single P. falciparum genotype. By examination of serial samples from single human infections, the MSP characteristics were found to remain constant throughout the course of infection. An apparent clonal population structure of parasites seemed to cause outbreaks in small isolated villages. The use of standard molecular epidemiologic methods to measure genetic diversity in malaria revealed the occurrence of a genetically monomorphic population of P. falciparum within a human community.
Assuntos
Surtos de Doenças , Indígenas Sul-Americanos , Malária Falciparum/etnologia , Malária Falciparum/parasitologia , Plasmodium falciparum/genética , Animais , Antígenos de Protozoários/genética , Southern Blotting , DNA de Protozoário/análise , Eletroforese em Gel de Ágar , Genes de Protozoários , Humanos , Proteína 1 de Superfície de Merozoito/genética , Epidemiologia Molecular , Plasmodium falciparum/crescimento & desenvolvimento , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Proteínas de Protozoários/genética , População Rural , Venezuela/epidemiologiaRESUMO
To determine whether malaria perpetuates within isolated Amerindian villages in the Venezuelan Amazon, we surveyed malaria infection and disease among 1,311 Yanomami in three communities during a 16-month period. Plasmodium vivax was generally present in each of these small, isolated villages; asymptomatic infection was frequent, and clinical disease was most evident among children less than five years of age (odds ratio [OR] = 6.3, 95% confidence interval [CI] = 1.4-29.2) and among persons experiencing parasitemias > or = 1,000 parasites/mm3 of blood (OR = 45.0, 95% CI = 5.5-370.7). Plasmodium falciparum, in contrast, was less prevalent, except during an abrupt outbreak in which 72 infections resulted in symptoms in all age groups and at all levels of parasitemia, and occasionally were life-threatening. The observed endemic pattern of P. vivax infection may derive from the capacity of this pathogen to relapse, while the epidemic pattern of P. falciparum infection may reflect occasional introductions of strains carried by immigrants or residents of distant villages and the subsequent disappearance of this non-relapsing pathogen.
Assuntos
Indígenas Sul-Americanos , Malária Falciparum/epidemiologia , Malária Vivax/epidemiologia , Adolescente , Adulto , Distribuição por Idade , Animais , Anopheles/parasitologia , Criança , Pré-Escolar , Estudos Transversais , Feminino , Humanos , Lactente , Recém-Nascido , Malária Falciparum/parasitologia , Malária Vivax/parasitologia , Masculino , Parasitemia/parasitologia , Plasmodium falciparum/isolamento & purificação , Plasmodium vivax/isolamento & purificação , Estudos Prospectivos , Chuva , População Rural , Estações do Ano , Venezuela/epidemiologiaRESUMO
Enlarged regional lymph nodes have been reported to accompany the cutaneous lesions of Leishmania (Viannia) braziliensis (= L. braziliensis). A survey in Ceara State, Brazil indicated that 77% of persons (456 of 595) with parasitologically confirmed cutaneous leishmaniasis reported lymphadenopathy in addition to skin lesions. A group of 169 persons with recently diagnosed leishmaniasis and lymph nodes measuring > or = 2 cm in diameter (mean = 3.6 cm, maximum = 10.5 cm) underwent detailed clinical examination. Lymphadenopathy preceded the skin lesions in more than two-thirds of these, on the average by two weeks. Cultures of lymph node aspirates yielded Leishmania more frequently (86%) than cultures of aspirates of skin (53%) or biopsies of skin (74%). Parasites were isolated from the peripheral blood of one patient. Persons with lymphadenopathy gave a history of fever and had enlarged livers or spleens more often than a comparison group of 50 persons with cutaneous lesions but no lymphadenopathy. Persons with lymphadenopathy had more intense leishmanin skin reactions and lymphocyte proliferation following stimulation with specific antigens, whereas persons without lymphadenopathy had a higher frequency of previous infection. Isolates of parasites from both groups were identified as L. braziliensis. These data demonstrate the early spread of L. braziliensis beyond the skin and suggest differences in host immunity between persons with and without lymphadenopathy. Leishmaniasis braziliensis should be considered in cases of unexplained lymphadenopathy in endemic areas.
Assuntos
Leishmania braziliensis/isolamento & purificação , Leishmaniose Cutânea/patologia , Linfonodos/parasitologia , Doenças Linfáticas/parasitologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Biópsia por Agulha , Brasil , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Leishmania braziliensis/imunologia , Leishmaniose Cutânea/complicações , Linfonodos/patologia , Doenças Linfáticas/patologia , Ativação Linfocitária , Masculino , Pessoa de Meia-Idade , Pele/parasitologia , Pele/patologia , Testes CutâneosRESUMO
The evolution of Chagas' cardiomyopathy is poorly understood. We therefore examined the development of cardiac lesions in a rural Brazilian community for a period of 7 years. Initially, 42% of 1017 residents were seropositive for infection with Trypanosoma cruzi. Age-specific infection rates indicated that most had become infected before the age of 20 years. On follow-up, it appeared that those persons who developed cardiac lesions did so soon after infection, since the incidence of right bundle branch block and other ventricular conduction defects (VCDs) was also highest before age 20 years. The progressive nature of these lesions was demonstrated by frequent development of additional electrocardiographic abnormalities and high mortality among infected adults with VCDs. In contrast, mortality was low and approximately the same for seropositive and seronegative adults under 60 years who had normal electrocardiograms. Electrocardiography during the early asymptomatic stage of infection was able to distinguish persons with potentially lethal cardiac lesions from those with a benign prognosis.
Assuntos
Cardiomiopatia Chagásica/epidemiologia , Fatores Etários , Anticorpos/análise , Brasil , Cardiomiopatia Chagásica/diagnóstico , Cardiomiopatia Chagásica/mortalidade , Eletrocardiografia , Seguimentos , Humanos , Estudos Prospectivos , População Rural , Trypanosoma cruzi/imunologiaRESUMO
An outbreak of 20 cases of acute Chagas' disease followed the movement of Triatoma infestans into the county of Riacho de Santana, Bahia, Brazil. The outbreak was unusual in that the majority of cases occurred in adults. Vector control measures were implemented. Three years after the outbreak, a rural community was examined to determine the extent of human infection and disease due to Trypanosoma cruzi. Ninety of 440 residents (20.5%) had serologic evidence of infection, but rates of electrocardiographic (EKG) abnormalities were low. Comparison of age-specific rates of seropositivity and EKG abnormalities with rates from areas with endemic Chagas' disease supported the hypothesis of a recent epidemic. Control measures appear to have interrupted transmission in the region.
Assuntos
Doença de Chagas/epidemiologia , Surtos de Doenças , Adulto , Idoso , Anticorpos/análise , Brasil , Cardiomiopatia Chagásica/epidemiologia , Doença de Chagas/transmissão , Criança , Pré-Escolar , Estudos Transversais , Humanos , Lactente , Controle de Insetos , Insetos Vetores , Pessoa de Meia-Idade , População Rural , Triatoma , Trypanosoma cruzi/imunologiaRESUMO
This prospective study has shown that oxamniquine treatment controlled endemic schistosomiasis mansoni in a defined rural population in Castro Alves, north-east Brazil. Data before and after treatment spanning 11 years were collected for a cohort of 191 residents. Before treatment (1974-77), the cohort was heavily infected and the prevalence of associated hepatomegaly (greater than 86%) and splenomegaly (greater than 17%) was stable. The cohort was treated when oxamniquine became available in 1977; during the next 8 years, over 80% received further treatments from the Brazilian programme for the control of schistosomiasis. With treatment, the incidence of splenomegaly fell (10% to 2%) and the splenomegaly regression rate increased (43% to 91%). Declining disease rates were coincident with substantial falls in the prevalence and intensity of Schistosoma mansoni infections. The final prevalence rates for hepatomegaly (31%) and splenomegaly (3%) in Castro Alves approached the corresponding rates of 10% and 1% in a comparable uninfected control population.