Assessing the effects of temperature on the population of Aedes aegypti, the vector of dengue.

Dengue is a vector-borne disease transmitted by the mosquito Aedes aegypti. The incidence of dengue disease shows a clear dependence on seasonal variation. How does the temperature affect the incidence? We addressed this question indirectly by estimating the size of the A. aegypti population for different temperatures applying population dynamics theory. In order to achieve this objective we designed temperature-controlled experiments to assess the entomological parameters regarding the mosquito's life-cycle at different temperatures. By obtaining the mortality, transition and oviposition rates for different stages of the life-cycle of the mosquito we were able to calculate the basic offspring number Q(0), which is the capacity of vector reproduction and ultimately gives the size of the vector population.

Assessing the effects of temperature on dengue transmission.

The incidence of dengue infection, a vector-borne disease transmitted by the mosquito Aedes aegypti, shows clear dependence on seasonal variation. Based on the quantification method that furnishes the size of the A. aegypti population in terms of the estimated entomological parameters for different temperatures, we assessed the risk of dengue outbreaks. The persistence and severity of epidemics can be assessed by the basic reproduction number R(0), which varies with temperature. The expression for R(0) obtained from 'true' and 'pseudo' mass action laws for dengue infection is discussed.

[Triatoma infestans in area under entomological surveillance for Chagas' disease in São Paulo State, Brazil]. / Triatoma infestans em área sob vigilância entomológica para doença de Chagas, Estado de São Paulo, Brasil.

In response to notification of the capture of a winged triatomine bug by local inhabitants, an epidemiological investigation was investigated in the rural area of the Municipality of Paulínia, São Paulo State (Brazil). This led to the collection of 109 specimens of Triatoma infestans from peridomiciliary breeding sites. Local conditions favored colonization by triatomine bugs: many abandoned outbuildings were inhabited by pigeons and sparrows, which meant abundant feed for these bugs. Thus, surveillance is mandatory as long as conditions for triatomine breeding persist. Nevertheless, entomological and serological indicators ruled out immediate concern over vectorial transmission of Chagas' disease in this municipality. All domiciliary units of the region were sprayed with residual-effect insecticides and the triatomine breeding sites were destroyed by the use of mechanical control of bird nests. The importance of reporting the occurrence of triatomine bugs, particularly Triatoma infestans, in this region, is emphasized.

[Chagas' disease in São Paulo State: a comparative study between systematic search and inhabitants' report of bugs in the area under entomological surveillance]. / Doença de Chagas no Estado de São Paulo: comparação entre pesquisa ativa de triatomíneos em domicílios e notificação de sua presença pela população em área sob vigilância entomológica.

Entomological surveillance of Chagas' disease in São Paulo State has adopted a scheme that uses the locality as a unit for field work. Actions are prioritized according to infestation levels obtained by systematic search of triatomine (routine actions), bugs in areas with high infestation levels and in houses whose inhabitants report the presence of the bugs (reply to notification). The most prevalent triatominic species in Sao Paulo State at present are Triatoma sordida and Panstrongylus megistus. A comparative study of infestation levels obtained in houses and surroundings in routine search and replies to notification in the two-year periods of 90/91, 92/93 and 94/95, has shown average percentage positivity of 1.3 indoors in routine activity and 6.2 in the reply to notification. For the house surroundings the values were 8.6 and 18.2 respectively, no differences being found between the two-year periods. Replies to notification showed average percentage positivity (focus) in 26% of the houses. It was verified that the notifications had come from localities with prior infestation levels equal to zero (I = O), intermediary infestation levels (I < 5) and high infestation levels (I > 5), although the percentages of positive replies to notification were higher in those localities with high prior infestation levels. These results reinforce the importance of notification in the surveillance of vector species of the invasive type like those currently prevalent in Sao Paulo State.

[American tegumentary leishmaniasis: Phlebotominae in an area of disease transmission, the city of Pedro de Toledo, southern region of the state of Sao Paulo, Brazil]. / Leishmaniose tegumentar americana: flebotomíneos de área de transmissão, no município de Pedro de Toledo, região sul do Estado de São Paulo, Brasil.

Considered as an American tegumentary leishmaniasis (ATL) endemic area, Ribeira Valley, in the south region of São Paulo State, presented 929 notified cases in the last 15 years. Aiming to identify the phlebotomine fauna, captures were performed fortnightly in the rural area of Pedro de Toledo County during one year, from may 1994 onwards. Set at dusk Shannon traps were used in the peridomicile and CDC light traps both intra and peridomiciliarly and at the edge and in the forest. Eight species summing to 11,096 specimens were caught, L. intermedia being the dominant one (96.4%). More frequent all over the year during the first half of the night preferably in the domicile surroundings this species clearly indicated its preference for the anthropic environment. The data presented in this paper ratify L. intermedia as an important ATL vector species in the Ribeira Valley.

Leishmaniose tegumentar americana: flebotomíneos de área de transmissão, no município de Pedro de Toledo, região sul do Estado de São Paulo, Brasil / American tegumentary leishmaniasis: Phlebotominae in an area of disease transmission, the city of Pedro de Toledo, southern region of the state of Sao Paulo, Brazil

Considerado como área endêmica de leishmaniose tegumentar americana (LTA), o Vale do Ribeira, na região sul do Estado de São Paulo, teve 929 casos notificados nos últimos 15 anos. Com o objetivo de identificar a fauna flebotomínea, foram realizadas capturas quinzenais em área rural do município de Pedro de Toledo, durante um ano, a partir de maio de 1994. Foram utilizadas armadilhas de Shannon no peridomicílio e armadilhas luminosas, tipo CDC, nos ambientes: domiciliar (intra e peri) e florestal (margem e interior), instaladas a partir do crepúsculo vespertino. Foram coletadas 8 espécies de flebotomíneos, totalizando 11.096 exemplares, sendo Lutzomyia intermedia a espécie dominante (96,4%). Esta espécie mostrou-se mais freqüente na primeira metade da noite, ocorrendo o ano inteiro, preferencialmente no ambiente domiciliar, o que indica sua preferência por ambiente antrópico. Os dados do presente trabalho ratificam L. intermedia como importante espécie vetora de LTA no Vale do Ribeira.

Considered as an American tegumentary leishmaniasis (ATL) endemic area, Ribeira Valley, in the south region of São Paulo State, presented 929 notified cases in the last 15 years. Aiming to identify the phlebotomine fauna, captures were performed fortnightly in the rural area of Pedro de Toledo County during one year, from may 1994 onwards. Set at dusk Shannon traps were used in the peridomicile and CDC light traps both intra and peridomiciliarly and at the edge and in the forest. Eight species summing to 11,096 specimens were caught, L. intermedia being the dominant one (96.4%). More frequent all over the year during the first half of the night preferably in the domicile surroundings this species clearly indicated its preference for the anthropic environment. The data presented in this paper ratify L. intermedia as an important ATL vector species in the Ribeira Valley.

[Sandflies (Diptera, Psychodidae) from the transmission area for American cutaneous leishmaniasis in the town of Itupeva, the southeastern region of São Paulo state, Brazil]. / Flebotomíneos (Diptera, Psychodidae) de área de transmissão de leishmaniose tegumentar americana, no município de Itupeva, região sudeste do Estado de São Paulo, Brasil.

The present study was effected aiming the verification of the seasonal, spatial and hourly of the phlebotominic species found in the county of Itupeva. Captures were performed fortnightly and 864 sand flies were collected between april/94 and march/95. 81.3% of the captured specimens belonged to 4 species: L. migonei (32.4%), L. whitmani (26.0%), L. intermedia (12.0%) e L. fischeri (10.9%). Such species showed larger densities during the cold and dry season of the year (from april to september/94) and were more active between the second and the fifth hour after twilight. L. migonei predominated almost in all the investigated surroundings being followed by L. whitmani and L. longipalpis in the domestic environments. In conclusion it is thought that in conjunction with L. intermedia, a suspect vector in the State of São Paulo, L. migonei and L. whitmani may have an important role in the transmission of cutaneous leishmaniasis in the area under study.

[American cutaneous leishmaniasis: sandflies from the transmission area in the town of Teodoro Sampaio, the southeastern region of São Paulo state, Brazil]. / Leishmaniose tegumentar americana: flebotomíneos de área de transmissão no município de Teodoro Sampaio, região sudoeste do Estado de São Paulo, Brasil.

Sandflies were captured in a secondary forest zone in the county of Teodoro Sampaio, São Paulo, during 12 months as from May 1994. Two houses located respectively at 240 m and 850 m from the semi-deciduous forest were selected. Night Center of Disease Control trap captures were performed fortnightly from twilight to dawn intradomiciliarily, in the edge and the interior of the forest and in the peridomicile of each one of the houses. Captures were realized as well in the peridomicile using Shannon traps during 6 hour for 24 captures and 4 quarter captures from twilight to dawn. The dominant species was Lutzomyia intermedia (93.5%). A larger number of insects were captured in the traps located in the edge of the forest. In the peridomicile of both houses an equivalent number of insects were captured, although a clear predominance of males was observed in the more distant located house. In the interior of the house located near the forest a larger number of specimens predominantly female were captured. L. intermedia and L. whitmani peaks occurred in the first hour and were characteristically more abundant in May, September and December when the mean temperature varied from 21 to 25.7 degrees C and the pluviometric index as from 66.7 to 195.1 mm.

[Triatoma infestans: importance, control and elimination of the species in the state of São Paulo, Brazil]. / Triatoma infestans: importância, controle e eliminação da espécie no Estado de São Paulo, Brasil.

Considerations about the control of the vectors of Chagas' disease are made in the State of Sao Paulo, mainly those activities that led to the elimination of T. infestans. First of all, the authors discuss different aspects of the biology of T. infestans mainly those that permitted it to adapt itself in rural areas of the State in the first middle of the century. Secondary factors that helped the control such as rural exodus are also analysed. The article shows that since 1965 the control became a campaign with different phases due to the epidemiological situation, the acquired knowledge and the entomological surveillance. After 25 years of work, the elimination of all the focus of T. infestans was finally reached and the campaign was ended. However, due to the possibility of reintroduction of the vector in rural areas by passive transportation besides the presence of secondary vectors (T. sordida and P. megistus) in several localities, the vector control activities were not interrupted and the surveillance is continuous.

Triatoma infestans: importância, controle e eliminação da espécie no Estado de São Paulo, Brasil / Triatoma infestans: importance, control and elimination of the species in the state of São Paulo, Brazil

Os autores tecem considerações a respeito do controle dos transmissores da doença de Chagas no Estado de São Paulo, especialmente sobre as atividades que levaram à eliminação do T. infestans. Inicialmente, fazem um apanhado histórico e apresentam as características principais da espécie que possibilitaram sua adaptação à situação vigente na zona rural do Estado, na primeira metade do século. Destacam também os fatores coadjuvantes às ações de controle, particularmente o êxodo rural. Mostram que a partir de 1965 o combate tomou a forma de uma verdadeira campanha, com fases distintas em função das alterações epidemiológicas, experiência adquirida e pressão dos custos. Descrevem cada fase: arrastão, expurgo seletivo, prioridades e vigilância entomológica. Após 25 anos de trabalho a campanha foi considerada encerrada, com a eliminação dos focos da espécie do planalto paulista. Porém, em função da possibilidade da reintrodução de T. infestans (transporte passivo) e da presença, em diversas localidades, de exemplares de espécies vetoras semidomiciliares (T. sordida e P. megistus) as atividades de controle não foram interrompidas e em conseqüência continua em andamento a Vigilância/ Manutenção.

Considerations about the control of the vectors of Chagas' disease are made in the State of Sao Paulo, mainly those activities that led to the elimination of T. infestans. First of all, the authors discuss different aspects of the biology of T. infestans mainly those that permitted it to adapt itself in rural areas of the State in the first middle of the century. Secondary factors that helped the control such as rural exodus are also analysed. The article shows that since 1965 the control became a campaign with different phases due to the epidemiological situation, the acquired knowledge and the entomological surveillance. After 25 years of work, the elimination of all the focus of T. infestans was finally reached and the campaign was ended. However, due to the possibility of reintroduction of the vector in rural areas by passive transportation besides the presence of secondary vectors (T. sordida and P. megistus) in several localities, the vector control activities were not interrupted and the surveillance is continuous.

Autochthonous acute Chagas' disease in São Paulo State, Brazil: epidemiological aspects.

Since the beginning of the seventies the natural transmission of Chagas' infection has been considered to be under control in the State of São Paulo and not even a case of American Trypanosomiasis, transmitted by triatomine bugs, has been detected by the epidemiological surveillance system. This situation justifies the report of a case of acute Chagas' disease that occurred in a forest area considered free of domiciliary triatomines along the Southern seacoast of São Paulo State. In May, 1995 the presence of trypomastigote forms of Trypanosoma cruzi had been diagnosed in a retired 57 year-old male patient, born and living in Santos (São Paulo State), complaining of fever, fatigue and malaise. The patient reported that 40 days before he had participated with 17 friends in a 7-day excursion in a forest area of the municipalities of Itanhaém and Peruíbe. During this period the group had been lodged in three houses located within the forest. Eight days after the end of the excursion the patient began to have fever, malaise and fatigue. During the next 31 days he had received medical care both as an inpatient and an outpatient, without any significant improvement. After the detection of T. cruzi trypomastigotes in his blood stream the patient began to be treated with benzonidazole in a hospital but died 8 days after the beginning of treatment. The epidemiological investigation carried out showed no signs of the presence of triatomine bugs in the three houses where the group had been lodged, or any indication of Chagas' infection in other excursionists.

Epidemiology of Chagas' heart disease.

Chagas' disease is a major public health problem in Latin America. About 16 million persons are affected and 90 million others are exposed to the risk of being infected by the parasite. The knowledge of epidemiological aspects of the disease allowed to delineate the strategies for the control of the disease related with the vectorial transmission. However, these strategies have had no priority in all endemic countries. Rural-urban migration in most endemic areas carried infected individuals to urban centers increasing the problem of Chagas' disease by blood transfusion. In Brazil the control program has reached good results in the last years and in several states the vectorial transmission was controlled. More recently, hemotherapic practices are performed using screening procedures but this practice must be improved in order to eliminate the possibility of Chagas' disease transmission by another ways (congenital, accidental, oral, etc.). An adequate health care to the infected persons must be improved in order to diminish the social costs of the severe cardiopathy which has been responsible for the adults premature deaths.

[Epidemiological aspects of malaria in the State of São Paulo, Brazil, 1983 to 1992]. / Aspectos epidemiológicos da malária no Estado de São Paulo, Brasil, 1983 a 1992.

Epidemiological aspects of malaria in the State of S. Paulo, Brazil, based on the cases motified between 1983 and 1992 are presented. In the period 20,200 cases, of which 65.7% presented Plasmodium vivax (P.v.) and 27.3% P. falciparum (P.f.), were confirmed. No differences as between the years was observed. No differences in the distribution by sex (85.4% male) or age (63.6% whit ages between 20 and 39 years) were noted. The epidemiological investigations demonstrated that in 2.0% the transmission of malaria has occurred in two different areas of the State of S. Paulo. One of these areas is covered with Atlantic forest where malaria is considered endemic, with a predominance of P. vivax and low parasitaemias associated with Kerteszia. The other area is the Paulista plateau, where Nyssorhynchus and patients with imported malaria were responsible for pochets P.V. and P.f. It was noted that 91.6% of the cases came from other regions of the country, 89.0% of them from Rondomia, Mato Grosso and Pará. The increase in the number of cases from Mato Grosso, corresponding to 51.7% of the total in 1992, was verified over this ten-year period. Malaria induced by blood transfusion and among drug users represented 27 and 58 cases, respectively. The lethality rate was 5.0/1,000 patients and occurred among patients with first time and late diagnosis of P. falciparum malaria. The study of this information adds its contributions for malaria surveillance.

[Hemotherapy and transfusional Chagas' disease in Brazil]. / Hemoterapia e doença de Chagas transfusional no Brasil.

With the increased presence of Chagas' disease in urban areas and the rising importance of transfusional transmission of Trypanosoma cruzi, a proper and realistic approach to hemotherapeutic treatment has become crucial in Brazil. Bringing together data from various institutions, this study analyzed hemotherapy and the problem of transfusional Chagas' disease in 850 Brazilian municipalities from 1988 to 1989. It was found that some type of hemotherapy was practiced in 68.8% of these municipalities at the time, this practice being qualitatively and quantitatively proportional to the population size of the municipality. The official blood bank system supplied the blood used in 13% of these services. In relation to prevention of the main diseases transmissible by transfusion, prior screening of donors was carried out by 75.2% of the services for syphilis, 65.4% for hepatitis, 53.8% for AIDS, and 66.9% for Chagas' disease. These percentages vary by region and by size of the municipality. The majority of donors are classified as voluntary, with only 2% categorized as paid donors. In the case of Chagas' disease, most services used only one serologic technique to screen donors, most commonly hemagglutination or immunofluorescence, while only 10.3% of services had previous experience with chemoprophylaxis using gentian violet. The proportion of potential donors with positive serology for anti-Trypanosoma cruzi antibodies was around 1%. These data were confirmed by information from blood banks and Brazilian hemotherapy professionals.

[Chagas' disease as main cause of death in the southeastern region of Brazil: presence of contributory causes]. / Doenca de Chagas como causa básica de óbito na região sudeste do Brasil: presença de causas contributárias.

Death certificates of all persons who died in in the State of S.Paulo, Brazil and which presented Chagas' disease as the principal cause of death, were studied with a view to analysing the existing additional information available as to contributory causes. After a direct reading of the 1,308 death certificates, the contributory causes were identified and registered. They were mentioned in 261 (20%) of the certificates, 185 of them presenting only one, and 75 two of them. The 6 more frequent contributory causes were: "megas", embolism, chronic pulmonary disease, infections (other than Chagas' disease), arterial hypertension and malnutrition. When analysing the presence of the contributory causes in two groups-persons of less than 50 years old, and those older than 50 a higher proportion of them was observed in the older group and a distinct profile of causes was found for each group. No statistic association was observed between contributory causes and sex or site of residence.

[Control of hemotherapy and transfusional Chagas disease: 1988 and 1990]. / Controle da hemoterapia e da doença de Chagas transfusional: 1988 e 1990.

An inquiry with the objective of bringing the study of the hemotherapy situation in the state of S. Paulo, up-to-date was undertaken in 1990 and compared with that carried out in 1988. In 1990 research was undertaken in 62 counties, 48 of which performed blood transfusions through 104 services, with hemocenter participation in 13.5% of these latter. In 1988 the respective figures were 57, 40, 71 and 8.5%. The number of donors and transfusions and prevalence of serological positivity for Chagas' disease were, respectively: 105,170; 79,544 and 1.24%, while in 1988 the corresponding numbers were: 51,614; 49,211 and 1.52%. Evaluating the serological selection it was found that the following percentages of the services performed serological tests: for Chagas' disease (94.2%), syphilis (94.2%), hepatitis (94.2%), HIV (92.3%) and malaria (20.2%) while in 1988 only 69.0%; 70.4%; 67.6%, 63.4% and 16.9%, respectively, of the services utilized these same tests. In respect of the serological trial specific for Chagas' disease the results were: complement fixation-4.9%; latex-4.0%; indirect immunofluoresce-80%; direct hemaglutination-24.0%, indirect hemaglutination-69.0% and ELISA-59.0% of all services. In the preceding inquiry only 14.3% of the services performed the ELISA test, and complement fixation was utilized in 28.6%. The results show that the services are utilizing ever more sensitive techniques in the serological routine. Further it was observed that in 1988, 77.6% of all the services studied used only one technique for the diagnosis of Chagas' disease while in 1990 92.9% utilized two or more different techniques. It is concluded that the quality of the hemotherapy undertaken in the state of S. Paulo has improved significantly.

[Transfusional Chagas infection detected in the program for the control of Chagas disease in the state of São Paulo (Brazil)]. / Infecção chagásica transfusional detectada no programa de controle da doença de Chagas no Estado de São Paulo (Brasil).

A system of surveillance for Chagas' disease aiming at a systematic investigation of the occurrence of triatominae in human dwellings in S. Paulo, Brazil was proposed. It included a serological survey of residents in house considered to be potential breeding places for blood-sucking triatomines. Serologically positive cases were observed to be distributed in age groups from 19 years of age upwards. Case-investigation revealed that the infection had been acquired either in S. Paulo in the past or recently in other States. A serologically positive (titre = 128 - IgG) case of an 8-year-old male child, was detected by the In direct Fluorescent Antibody Technique (IFAT). In S. Paulo State natural transmission is now of low probability. An epidemiological investigation disclosed the fact that this was a case of blood transfusion infection. The donor was found to be serologically positive (IFAT, titre = 1024 - IgG). His case-history was typical of vector transmitted infection. It is worthy of note that blood had been donated by this patient in four instances, without his condition having been diagnosed. The necessity of organizing an integrated Public Health Service to take more efficient care of such cases is stressed.

[Mortality due to Chagas disease in São Paulo State (Brazil): subsidy for the planning of chagasic patient care]. / Mortalidade por doença de Chagas no Estado de São Paulo (Brasil): subsídios para o planejamento da assistência ao chagásico.

In order to estimate the size of the population with Chagas' disease, an essential parameter for the establishment of an adequate health care policy for this group of patients, data from 1,646 death certificates from the "Fundação Sistema Estadual de Análises de Dados" in which Chagas' disease was mentioned in the State of S. Paulo in 1987 were examined. The population under study comprised adults between 15 and 70 years of age. Objectives also included the determination of Proportional Mortality, Potentially Lost Years of Life and regional distribution of the events in the counties of the State of S. Paulo. Chagas disease accounted for 0.9% of the totality of the causes of death, Proportional Mortality was 1.2% and the proportional participation of Chagas' disease in the Potentially Lost Years of Life was 1.1%. Corresponding data for Ischemic Heart Disease were, 4.0% and 1.2%. 20.8% of the deaths occurred in counties other than the county of residence, the indexes of evasion varying from 17.8% to 29.1% for different regions. Males (22.8%) more often than females (17.4%) died outside their county of residence. The largest number of deaths occurred in the metropolitan area of S. Paulo, although Ribeirão Preto county presented the highest mortality indexes.

[Malaria induced in the state of Sao Paulo, Brazil]. / Malária induzida no Estado de São Paulo, Brasil.

A review is presented of 58 induced malaria cases diagnosed in the São Paulo State, from January 1983 to July 1990. These cases represent 0.3% of the malaria notifications. The parameters sex, age, parasitaemia, clinical symptoms, clinical course and mean time interval between disease onset and diagnosis were studied in 25 blood-transmitted cases and 28 related to sharing needles. Plasmodium vivax was diagnosed in 79.4% and in 5.6% Plasmodium vivax and Plasmodium falciparum were seen. Lower mean age (p < 0.005) in intravenous drug users when compared in the blood-transmitted group were observed. The former also had a mean time interval between disease onset and diagnosis (33.6 days) and patients with blood-transmitted disease (20.6 days). No statistical significant differences were observed (p > 0.10). Even though few induced malaria cases have been diagnosed in São Paulo, State, and considering that blood-transmitted malaria is now under control, the occurrence of malaria due to sharing needles among intravenous drug users should be regarded as a risk for the reintroduction of the disease in malaria--free areas of São Paulo State.