Sleep, ageing and night work

Studies have shown that the frequency or worsening of sleep disorders tends to increase with age and that the ability to perform circadian adjustments tends to decrease in individuals who work the night shift. This condition can cause consequences such as excessive sleepiness, which are often a factor in accidents that occur at work. The present study investigated the effects of age on the daytime and nighttime sleep patterns using polysomnography (PSG) of long-haul bus drivers working fixed night or day shifts. A total of 124 drivers, free of sleep disorders and grouped according to age (<45 years, N = 85, and ≥45 years, N = 39) and PSG timing (daytime (D) PSG, N = 60; nighttime (N) PSG, N = 64) participated in the study. We observed a significant effect of bedtime (D vs N) and found that the length of daytime sleep was shorter [D: <45 years (336.10 ± 73.75 min) vs N: <45 years (398 ± 78.79 min) and D: ≥45 years (346.57 ± 43.17 min) vs N: ≥45 years (386.44 ± 52.92 min); P ≤ 0.05]. Daytime sleep was less efficient compared to nighttime sleep [D: <45 years (78.86 ± 13.30 percent) vs N: <45 years (86.45 ± 9.77 percent) and D: ≥45 years (79.89 ± 9.45 percent) and N: ≥45 years (83.13 ± 9.13 percent); P ≤ 0.05]. An effect of age was observed for rapid eye movement sleep [D: <45 years (18.05 ± 6.12 percent) vs D: ≥45 years (15.48 ± 7.11 percent) and N: <45 years (23.88 ± 6.75 percent) vs N: ≥45 years (20.77 ± 5.64 percent); P ≤ 0.05], which was greater in younger drivers. These findings are inconsistent with the notion that older night workers are more adversely affected than younger night workers by the challenge of attempting to rest during the day.

Sleep, ageing and night work.

Studies have shown that the frequency or worsening of sleep disorders tends to increase with age and that the ability to perform circadian adjustments tends to decrease in individuals who work the night shift. This condition can cause consequences such as excessive sleepiness, which are often a factor in accidents that occur at work. The present study investigated the effects of age on the daytime and nighttime sleep patterns using polysomnography (PSG) of long-haul bus drivers working fixed night or day shifts. A total of 124 drivers, free of sleep disorders and grouped according to age (<45 years, N = 85, and > or =45 years, N = 39) and PSG timing (daytime (D) PSG, N = 60; nighttime (N) PSG, N = 64) participated in the study. We observed a significant effect of bedtime (D vs N) and found that the length of daytime sleep was shorter [D: <45 years (336.10 +/- 73.75 min) vs N: <45 years (398 +/- 78.79 min) and D: > or =45 years (346.57 +/- 43.17 min) vs N: > or =45 years (386.44 +/- 52.92 min); P < or = 0.05]. Daytime sleep was less efficient compared to nighttime sleep [D: <45 years (78.86 +/- 13.30%) vs N: <45 years (86.45 +/- 9.77%) and D: > or =45 years (79.89 +/- 9.45%) and N: > or =45 years (83.13 +/- 9.13%); P < or = 0.05]. An effect of age was observed for rapid eye movement sleep [D: <45 years (18.05 +/- 6.12%) vs D: > or =45 years (15.48 +/- 7.11%) and N: <45 years (23.88 +/- 6.75%) vs N: > or =45 years (20.77 +/- 5.64%); P < or = 0.05], which was greater in younger drivers. These findings are inconsistent with the notion that older night workers are more adversely affected than younger night workers by the challenge of attempting to rest during the day.

Relationship between Brazilian airline pilot errors and time of day

Flight safety is one of the most important and frequently discussed issues in aviation. Recent accident inquiries have raised questions as to how the work of flight crews is organized and the extent to which these conditions may have been contributing factors to accidents. Fatigue is based on physiologic limitations, which are reflected in performance deficits. The purpose of the present study was to provide an analysis of the periods of the day in which pilots working for a commercial airline presented major errors. Errors made by 515 captains and 472 copilots were analyzed using data from flight operation quality assurance systems. To analyze the times of day (shifts) during which incidents occurred, we divided the light-dark cycle (24:00) in four periods: morning, afternoon, night, and early morning. The differences of risk during the day were reported as the ratio of morning to afternoon, morning to night and morning to early morning error rates. For the purposes of this research, level 3 events alone were taken into account, since these were the most serious in which company operational limits were exceeded or when established procedures were not followed. According to airline flight schedules, 35 percent of flights take place in the morning period, 32 percent in the afternoon, 26 percent at night, and 7 percent in the early morning. Data showed that the risk of errors increased by almost 50 percent in the early morning relative to the morning period (ratio of 1:1.46). For the period of the afternoon, the ratio was 1:1.04 and for the night a ratio of 1:1.05 was found. These results showed that the period of the early morning represented a greater risk of attention problems and fatigue.

Relationship between Brazilian airline pilot errors and time of day.

Flight safety is one of the most important and frequently discussed issues in aviation. Recent accident inquiries have raised questions as to how the work of flight crews is organized and the extent to which these conditions may have been contributing factors to accidents. Fatigue is based on physiologic limitations, which are reflected in performance deficits. The purpose of the present study was to provide an analysis of the periods of the day in which pilots working for a commercial airline presented major errors. Errors made by 515 captains and 472 co-pilots were analyzed using data from flight operation quality assurance systems. To analyze the times of day (shifts) during which incidents occurred, we divided the light-dark cycle (24:00) in four periods: morning, afternoon, night, and early morning. The differences of risk during the day were reported as the ratio of morning to afternoon, morning to night and morning to early morning error rates. For the purposes of this research, level 3 events alone were taken into account, since these were the most serious in which company operational limits were exceeded or when established procedures were not followed. According to airline flight schedules, 35% of flights take place in the morning period, 32% in the afternoon, 26% at night, and 7% in the early morning. Data showed that the risk of errors increased by almost 50% in the early morning relative to the morning period (ratio of 1:1.46). For the period of the afternoon, the ratio was 1:1.04 and for the night a ratio of 1:1.05 was found. These results showed that the period of the early morning represented a greater risk of attention problems and fatigue.

Sleep habits and complaints of adults in the city of São Paulo, Brazil, in 1987 and 1995

This study compares the prevalence of complaints of insomnia, excessive diurnal sleepiness, parasomnias, and sleep habits of the adult population in the city of São Paulo, Brazil, estimated in surveys carried out in 1987 and 1995. Representative samples of 1000 adult residents per survey were interviewed using a validated structured sleep questionnaire, the "UNIFESP Sleep Questionnaire". Difficulty maintaining sleep, difficulty initiating sleep and early morning awakening, occurring at least three times a week, were reported in 1987 and 1995, by 15.8/27.6, 13.9/19.1, and 10.6/14.2 percent of the interviewees, respectively, significantly increasing throughout time. These sleep problems were more often found among women. Frequencies of excessive diurnal sleepiness and sleep attacks were unchanged comparing 1987 with 1995 (4.5 vs 3.8 and 3.1 vs 3.0 percent, respectively). Parasomnia complaints remained unchanged, with the exception of leg cramps, which doubled in prevalence from 1987 to 1995 (2.6 to 5.8 percent). Snoring was the most common parasomnia (21.5 percent in 1995), reported more often by men than by women, and somnambulism was the least common (approximately 1 percent). Besides sleeping slightly less, interviewees went to bed and woke up later in 1995. Approximately 12 percent of the subjects in both surveys had consulted a physician due to sleep problems and 3.0 percent reported habitual use of sleep-promoting substances in 1995. Overall, there was a significant increase in insomnia complaints from 1987 to 1995 in the general population of the city of São Paulo. This major change over a little under a decade should be considered as an important public health issue.

Sleep habits and complaints of adults in the city of São Paulo, Brazil, in 1987 and 1995.

This study compares the prevalence of complaints of insomnia, excessive diurnal sleepiness, parasomnias, and sleep habits of the adult population in the city of São Paulo, Brazil, estimated in surveys carried out in 1987 and 1995. Representative samples of 1000 adult residents per survey were interviewed using a validated structured sleep questionnaire, the "UNIFESP Sleep Questionnaire". Difficulty maintaining sleep, difficulty initiating sleep and early morning awakening, occurring at least three times a week, were reported in 1987 and 1995, by 15.8/27.6, 13.9/19.1, and 10.6/14.2% of the interviewees, respectively, significantly increasing throughout time. These sleep problems were more often found among women. Frequencies of excessive diurnal sleepiness and sleep attacks were unchanged comparing 1987 with 1995 (4.5 vs 3.8 and 3.1 vs 3.0%, respectively). Parasomnia complaints remained unchanged, with the exception of leg cramps, which doubled in prevalence from 1987 to 1995 (2.6 to 5.8%). Snoring was the most common parasomnia (21.5% in 1995), reported more often by men than by women, and somnambulism was the least common (approximately 1%). Besides sleeping slightly less, interviewees went to bed and woke up later in 1995. Approximately 12% of the subjects in both surveys had consulted a physician due to sleep problems and 3.0% reported habitual use of sleep-promoting substances in 1995. Overall, there was a significant increase in insomnia complaints from 1987 to 1995 in the general population of the city of São Paulo. This major change over a little under a decade should be considered as an important public health issue.

Sleep disorders, sleepiness and traffic safety: a public health menace.

Sleep disorders are not uncommon and have been widely reported throughout the world. They have a profound impact on industrialized 24-h societies. Consequences of these problems include impaired social and recreational activities, increased human errors, loss of productivity, and elevated risk of accidents. Conditions such as acute and chronic insomnia, sleep loss, excessive sleepiness, shift-work, jet lag, narcolepsy, and sleep apnea warrant public health attention, since residual sleepiness during the day may affect performance of daily activities such as driving a car. Benzodiazepine hypnotics and zopiclone promote sleep, both having residual effects the following day including sleepiness and reduced alertness. In contrast, the non-benzodiazepine hypnotics zolpidem and zaleplon have no significant next-day residual effects when taken as recommended. Research on the effects of wakefulness-promoting drugs on driving ability is limited. Countermeasures for excessive daytime sleepiness have a limited effect. There is a need for a social awareness program to educate the public about the potential consequences of various sleep disorders such as narcolepsy, sleep apnea, shift-work-related sleep loss, and excessive daytime sleepiness in order to reduce the number of sleep-related traffic accidents.

Sleep disorders, sleepiness and traffic safety: a public health menace

Sleep disorders are not uncommon and have been widely reported throughout the world. They have a profound impact on industrialized 24-h societies. Consequences of these problems include impaired social and recreational activities, increased human errors, loss of productivity, and elevated risk of accidents. Conditions such as acute and chronic insomnia, sleep loss, excessive sleepiness, shift-work, jet lag, narcolepsy, and sleep apnea warrant public health attention, since residual sleepiness during the day may affect performance of daily activities such as driving a car. Benzodiazepine hypnotics and zopiclone promote sleep, both having residual effects the following day including sleepiness and reduced alertness. In contrast, the non-benzodiazepine hypnotics zolpidem and zaleplon have no significant next-day residual effects when taken as recommended. Research on the effects of wakefulness-promoting drugs on driving ability is limited. Countermeasures for excessive daytime sleepiness have a limited effect. There is a need for a social awareness program to educate the public about the potential consequences of various sleep disorders such as narcolepsy, sleep apnea, shift-work-related sleep loss, and excessive daytime sleepiness in order to reduce the number of sleep-related traffic accidents.

Videocapillaroscopy and Diabetes mellitus: area of transverse segment in nailfold capillar loops reflects vascular reactivity.

UNLABELLED: The value of measuring projected area of transverse segment of hand nailfold capillary loops using computerized videophotometry was studied in 17 healthy individuals (10 women and 7 men) group A and 17 patients with diabetes type 2 (10 women and 7 men) group B with comparable ages (49.94+/-8.62 x 49.11+/-14.63 years old P=0.49). Videocapillaroscopy (VC) was performed under controlled temperature environment (24-26 degrees C). The test of post-occlusive reactive hyperemia was performed using a sphygmomanometer attached to the fourth left hand finger, 20 mmHg above maximum arterial pressure during 1 min. Images were captured each 2 s during 1 min. Time averages to reach the maximum post-ischemia area were determined as well as the area's increment percent in both groups. Both averages were compared by the Mann-Whitney test. There was no differences between area increments percent averages among controls and patients with diabetes (52.49+/-22.6 x 67.99+/-47.48% P=0.67), but the time to reach it during reperfusion was significantly increased among diabetics (5.52+/-2.96 x 18.58+/-8.08 s P<0.0001). CONCLUSIONS: changes of capillary response to ischemia may be observed among patients with diabetes through bi-dimensional measures of projected area of capillary loops transverse segment in VC using a computerized system of image analysis. Patients with Diabetes mellitus do not have significantly different maximum area increments than controls, but spend more time to reach it during reperfusion.

Influence of infection with non-filarial helminths on the specificity of serological assays for antifilarial immunoglobulin G4.

Serological assays based on the detection of immunoglobulin (Ig) G4 antibodies to crude filarial extracts are widely used for epidemiological and diagnostic purposes. We tested 195 samples collected in 1998 from an area of Brazil where filariasis is not endemic and 13 (6.7%) had levels of antifilarial IgG4 antibodies that were defined as positive. Both Strongyloides infection and the presence of Strongyloides antibody responses were associated with higher antifilarial antibody responses. None of the specimens had a positive response to the Brugia malayi recombinant antigen (Bm14). These data suggest that serodiagnostic assays based on the use of crude filarial antigens should be interpreted with caution because of the potential for cross-reactivity with Strongyloides.

Localisation and distribution of Wuchereria bancrofti antigens recognised by antisera from tropical pulmonary eosinophilia and from individuals with intestinal helminths.

Serological analyses of sera from patients with a typical picture of filarial tropical pulmonary eosinophilia (TPE) and sera from patients from a region non-endemic for filariasis harbouring intestinal helminths, as Ascaris lumbricoides and Strongyloids stercoralis, revealed equally high titers of IgG4, usually considered diagnostic for filariasis. Ultrathin sections of adult worms of W. bancrofti embedded in the hydrophilic resin L.R. White were incubated with sera from patients with a typical picture of filarial tropical pulmonary eosinophilia (TPE) and sera from patients of a region that was non-endemic for filarial TPE but endemic for intestinal helminths. Both groups had a similar pattern of labelling, except that the labelling intensity was higher with the sera of patients with filarial TPE. The present study indicates relevant epitopes recognised by sera from TPE-patients and also individuals with intestinal helminths in all tissues of adult and intra-uterine microfilaria of W. bancrofti, instead of being localised in a specific nematode region. These findings suggest that people from areas not endemic for filariasis, but who harbour intestinal helminths, also share antifilarial antibodies in their serum that recognise antigens of adult worms and intrauterine microfilaria of W. bancrofti.

Acute effects of low doses of melatonin on the sleep of young healthy subjects.

This study was undertaken to evaluate the acute effects of single low doses of melatonin given to healthy volunteers in the evening. Six healthy male volunteers (age range 22-24 years) participated in this study, after signing an informed consent form. They received in a double-blind fashion placebo or 0.3 or 1.0 mg melatonin at three fixed times: 18:00, 20:00, and 21:00 hr. Polysomnographic recordings began immediately thereafter, with their being allowed to sleep. Prior to each experimental session and in the following morning, subjects completed a sleep quality questionnaire, the Profile of Mood States, the Stanford Sleepiness Scale, and underwent a visual reaction test. Significant decrease on sleep latencies was found following melatonin treatment at 18:00 and 20:00 hr. In addition, melatonin tended to improve sleep efficiency and to reduce intermittent wakefulness. However, at 21:00 hr, 0.3 mg melatonin increased latency to sleep onset and 1.0 mg melatonin had no effect on sleep variables. Furthermore, melatonin given at different times did not alter subjective sleepiness, mood, and reaction time in the following morning. The results from the present study support the notion that administration of low doses of melatonin, mimicking the nocturnal physiological concentration of this hormone may exert immediate sleep-inducing effects.

Capturing the circadian rhythms of free-running blind people with 0.5 mg melatonin.

We have recently shown that six of seven totally blind people (who had free-running circadian rhythms with periods longer than 24 h) could be entrained (synchronized) to a nightly dose of 10 mg melatonin. After treatment discontinuation and re-entrainment to the 10 mg dose, we further found in three of these subjects that the dose could be gradually reduced to 0.5 mg without loss of effect. The question then arose: can a de novo (starting) dose of 0.5 mg initially capture free-running rhythms? Following withdrawal of the stepped-down 0.5 mg dose and consequent release into a free-run, the same three individuals were given 0.5 mg of melatonin de novo. All entrained within a few weeks.

Clinical utility of the premenstrual assessment form as an instrument auxiliary to the diagnosis of premenstrual dysphoric disorder.

The Premenstrual Assessment Form (PAF) is a retrospective self-report questionnaire, yielding classification into syndromal categories and severity assessment (unipolar summary scales) of behavioral, psychological and physical premenstrual changes. However, the PAF has been criticized due to an overlap of its syndromal categories and the unipolar summary scores from symptomatic and asymptomatic women. PAF data from women seeking treatment for premenstrual symptoms and meeting a provisional diagnosis of premenstrual dysphoric disorder (PMDD; n=30) were compared to a control group (n=16). Results showed that 97% of the symptomatic group met the PAF depressive premenstrual syndrome criteria vs. only 12% of the control subjects (chi(2)=29.9, P<0.001). The symptomatic group also reported more severe premenstrual symptoms in all unipolar scales than the control subjects. Sixteen symptomatic women completed two menstrual cycles of prospective daily ratings, and half of them had their provisional diagnosis of PMDD confirmed. There were no significant differences in the scores of the PAF unipolar summary scales between the subgroups with or without the diagnosis confirmation. Most of the PAF scales displayed high sensitivity, but low specificity. These findings suggest that the PAF can be useful to differentiate clinical population and control samples, but it does not provide information to make a more definite diagnosis of PMDD.

Moclobemide effects on prolactin plasma levels in healthy individuals: the hormonal increase induced by a single dose is maintained during a 4-week period of drug intake.

Neuroendocrine challenge studies are frequently used to study the pathophysiology of psychiatric illnesses and the effects of psychotropic drug treatment on brain monoamine function. Moclobemide, a reversible inhibitor of monoamine oxidase, with predominant effects on the A-type of the enzyme, was administered to 15 healthy men. Seven out of the 15 also received single blind placebo a week before the moclobemide. The individuals received moclobemide as a single dose (150 mg), followed by doses of 150 mg three times a day, during a 4-week period. Plasma prolactin was measured in the morning over a 150-min period, following the single dose, and then at the end of weeks 1, 2 and 4 of moclobemide intake. The present data show an acute and transitory increase of plasma prolactin levels after the single dose, and also during the long-term moclobemide administration. It might indicate that steady-state moclobemide levels, during the long-term drug administration, were low and thus large fluctuations of drug levels occurred between doses. Thus, it is suggested that larger doses or administering smaller doses more frequently, or both, may induce hyperprolactinaemia with clinical consequences.

Comparative efficacy of three different diethylcarbamazine regimens in lymphatic filariasis.

To assess the efficacy of diethylcarbamazine (DEC) in clearing Wuchereria bancrofti microfilariae (mf) from the circulation, we conducted a single blind hospital-based therapeutic trial of 3 DEC regimens. All patients were assessed by filtration of 1 mL of venous blood taken before and 1, 3, 6 and 12 months after DEC administration. The efficacy of a 12 d course of 6 mg/kg DEC once daily was identical to that of a similar course with 2 mg/kg given 3 times daily, indicating that split-dose treatment does not improve mf clearance over single daily drug administration. Microfilarial densities in patients treated only once with 6 mg/kg DEC remained significantly higher at 1, 3, and 6 months after treatment. However, all 3 treatment regimens proved equally effective in controlling microfilaraemia after 12 months, when 41, 42 and 40% of patients in the 3 treatment groups were amicrofilaraemic. These results suggest that a single DEC dose of 6 mg/kg administered annually or biannually may be a suitable regimen to control bancroftian filariasis in Recife, Brazil.

Tolerance of diethylcarbamazine by microfilaraemic and amicrofilaraemic individuals in an endemic area of Bancroftian filariasis, Recife, Brazil.

To determine the tolerance to diethylcarbamazine (DEC) treatment of patients with Bancroftian filariasis, 193 individuals (138 asymptomatic microfilaraemic, 30 amicrofilaraemic diseased patients and 25 asymptomatic amicrofilaraemic endemic residents) were enrolled in a prospective trial with different dose schedules, in a hospital and outpatient clinic setting in Brazil. Systemic adverse reactions, localized adverse reactions, and side effects, related to microfilariae, adult worms and the drug itself, were evaluated. Systemic reactions occurred irrespective of the DEC dose and schedule in about 40% of the microfilariae carriers, but not in amicrofilaraemic diseased patients or residents; they usually consisted of microscopic haematuria, followed by fever and malaise. Localized reactions were manifested by the appearance of inflammatory reactions, mainly in the scrotal area. Nodules containing degenerating adult worms developed mainly in the scrotal lymphatics of microfilaraemic patients, diseased amicrofilaraemic patients, and residents. Drowsiness, which increased with higher doses of DEC, was the most common side effect in both microfilaraemic and amicrofilaraemic individuals, followed by nausea and gastric upset. The results indicate that the occurrence of systemic and local adverse reactions was unrelated to either the dose of DEC or the pretreatment microfilarial density. The severity of systemic reactions was proportional to the microfilarial density. Side effects were dependent on the drug dosage irrespective of infection status.

A study of placentas from Wuchereria bancrofti microfilaraemic and amicrofilaraemic mothers.

The prevalence of transplacental transfer of microfilariae and structural lesions in the placentas of amicrofilaraemic (n = 10) and Wuchereria bancrofti microfilaraemic (n = 10) pregnant women from the prenatal care unit of the Hospital das Clinicas, Recife, Brazil, was investigated. Study participants were selected by filtration (3 microns/13 mm) of nocturnal (2300-0100 h) venous blood. A detailed histopathological examination was performed to detect abnormalities in the placenta, the cord and the foetal membranes. Both study groups had similar obstetric profiles. Parasitaemia was present during labour in nine of ten microfilaraemic women, but no microfilariae were found by filtration of 5-10 ml cord blood. No macroscopic abnormalities were seen in placentas from microfilaraemic mothers; two placentas from the amicrofilaraemic cases contained, respectively, infarcted areas and cysts at the cut surface. Microscopy failed to detect microfilariae in the intervillous spaces, chorionic and decidual vessels, or the umbilical cord. Thus, transplacental transfer of Wuchereria bancrofti microfilariae seems to be a rare phenomenon, and microfilaraemia does not appear to be a risk factor for placental pathology.

[The importance of Strongyloides stercoralis revisited]. / Revendo a importância do Strongyloides stercoralis.

Strongyloidiasis is a worldwide parasitic disease and of great importance in Brasil. Among the diverse species of Strongyloides, only the following are of importance to man: S. stercoralis, S. fulleborni and S. fullerboni-like. Eventhough S. stercoralis is an intestinal helminth, strongyloidiasis is a systemic infection that can affect, beside the gastrointestinal tract, lungs, CNS, liver and biliary tract, pancreas, genitourinary tract and skin. The great majority of cases are asymptomatic, having a chronic and benign course. Among the symptomatic subjects, the gastrointestinal and pulmonary symptoms prevail. For unknown reasons, strongyloides infection may result in severe, disseminated disease. Immunosuppressive, therapy was identified as an important risk factor for disseminated illness. Diagnosing strongyloidiasis may be difficult, and eventhough the parasitological stool examination is the most used diagnostic test, sometimes larvae cannot be identified. Immunodiagnosis is not yet assessible for routine usage and is still a subject of research. Thiabendazole remains the drug of choice for treatment of strongyloidiasis, but other drugs, such as ivermectin, have been used. The purpose of this paper was to review the important aspects of the S. stercoralis infection in man.

Wuchereria bancrofti microfilarial density of autochthonous cases and natural Culex infectivity rates in northeast Brazil.

Autochthonous Wuchereria bancrofti microfilaraemic cases from three neighbouring cities of Northeast Brazil (Recife, Jaboatao and Olinda) were selected from thick smear or filtration positive individuals and classified by their microfilarial (mf) densities through polycarbonate membrane blood filtration. Individuals were subdivided into two groups: autochthonous cases without any previous specific drug administrations (group A) and those with one or more previous DEC treatments (group B). In Recife, unlike Jaboatao and Olinda (P less than 0.05), the majority of autochthonous cases were over 20 years old and no microfilaraemics were found under the age of 10. The majority of cases in Recife had lower levels of mf density (66.6%), while in Jaboatao and Olinda higher mf carriers (65.6%) prevailed when group A (n = 141) individuals were rearranged in mf density above and below 500 mf ml-1 (P less than 0.01). All subjects in group B (n = 110) had less than 501 mf ml-1 and the great majority less than 100 mf ml-1, but a significant difference (P less than 0.05) between Recife and the two other cities was observed. Captured mosquitoes in Recife, Jaboatao and Olinda totalled 7856, 8010 and 8003 respectively. The infectivity rate found in Recife (0.61%) was significantly lower than in Jaboatao (1.21%) and Olinda (1.31%) (P less than 0.001). The authors discuss the possible influences of previous disease control programmes (medicated salt and individual treatments) applied only to the city of Recife in relation to the outcome of this investigation.