Concomitant malaria and filariasis infections in Georgetown, Guyana

OBJECTIVE: To determine the prevalence of concomitant malaria and bancroftian filariasis among febrile patients in Georgetown, Guyana, South America. METHODOLOGY: From January to December 1997, all patients visiting the Georgetown Malaria and Filariasis Clinics were enrolled in the study. At the Filariasis Clinic, nocturnal thick blood smears prepared from blood taken between 8:00 pm and 12:00 midnight were dried and stored overnight. At the Malaria Clinic, thick blood smears were taken during the period 8:30 am to 4:00 pm, representing the diurnal study. All slides were stained using the standard Giemsa protocol and microscopically examined for the presence of filariasis and malaria. RESULTS: Of 1,267 persons, 83 percent were of African descent, 10 percent were of East Indian descent, and 7 percent were mixed or of other ethnic origins. Sixty-one per cent (769/1267) of smears were prepared from nocturnal blood samples whereas 509/1267 (40 percent) were diurnal samples from the Malaria Clinic. One hundred and three of 769 nocturnal blood smears were positive for only W bancrofti and 3 smears contained mixed infections, W bancrofti and malaria parasites. Only 21/509 diurnal blood smears had malaria parasites while 17 persons had both malaria and microfilaria parasites. CONCLUSION: The 20 cases of concomitant infection of malaria and bancroftian filariasis in this study may represent the first report of the occurrence of this phenomenon in Guyana.(AU)

Laboratory studies of diel oviposition, fecundity, survival, and gonotrophic cycles of Anopheles bellator Dyar and Knab in Trinidad, West Indies

Diel oviposition patterns of Anopheles bellator were determined for field collected females from platanal forest, Cumaca, Trinidad. The time of oviposition and number of eggs laid were monitored at two-hour intervals for a set of 30 individual females and a group of 120 females. Individual females of An. bellator displayed bimodal nocturnal patterns of oviposition. During the first gonotrophic cycle, two waves of oviposition occurred between 1600 and 2400 h (80.9 percent of eggs laid; 78 percent of occurrences) and between 0200 and 0600 h (19.1 percent of eggs laid; 22 percent of occurrences). During the second gonotrophic cycle the oviposition pattern was similar to that observed during the first gonotrophic cycle, except that oviposition ended at 0400 h rather than at 0600 h. A similar oviposition pattern was observed among the 120 caged adults as found during the second gonotrophic cycle of individual females. The length of the gonotrophic cycle ranged from 57 to 120 hours (means 72.3 hours) for the first gonotrophic cycle and from 61 to 78 hours (means 70.3 hours) for the second cycle. The fecundity of An. bellator averaged 56.6 +/- 25.0 (range 13 to 101 eggs) and 39.3 +/- 13.3 (range 23 to 59 eggs) for the first and second gonotrophic cycle, respectively. Females survived in the laboratory for a maximum of 19 days. These observations on An. bellator oviposition patterns are the first to be described and may be useful for future attempts at colonization.(AU)

Social economics of childhood glucocorticoid stress response and health

This study examines socioeconomic conditions, psychosocial stress, and health among 264 infants, children, adolescents, and young adults aged 2 months to 18 years residing in a rural Caribbean village in Dominica. Fieldwork was conducted over a 9 year period (1988-1996). Research methods and techniques include salivary cortisol radioimmunoassay (N = 22, 438), systematic behavioral observation, psychological questionnaires, health evaluation, medical records, informal interviews, and participant observation. Analyses of data indicate complex relations among socioeconomic conditions, stress, and health. Household income, land ownership, parental education, and other socioeconomic measures are weakly associated with child illness. There is no evidence that apparent material benefits of high socioeconomic status such as improved housing, diet, work loads, and access to private health care have important direct effects on child health in this population. However, social relationship, especially family environment, may have important effects on childhood psychosocial stress and illness. Abnormal glucocorticoid response profiles, diminished immunity, and frequent illness are associated with unstable mating relationships for parents/caretakers and household compositon. We suggest that family relationships and concomitant stress and immunosuppression are important intermediary links between socioeconomic conditions and child health.(AU)

Diel oviposition and fecundity of Anopheles oswaldoi in Trinidad, West Indies

The diel oviposition periodicity of wild-caught Anopheles oswaldoi collected from the forest-ecotone habitat in Valencia, Trinidad, was studied in the laboratory by recording the performance of egg-laying individuals and a colony at 2-h intervals. Oviposition was almost exclusively nocturnal, with 95.3 percent of eggs and 91.3 percent of oviposition occurrences being observed during the scotophase. During the rest of the day, only 4.7 percent of eggs (8. 7 percent ocurrences) were recorded after dawn (0600-0800 h). Wild caught females engorged on human blood under laboratory conditions matured, on average, 61.1 +/- 32.3 follicles 9range 56-135). Ranges of 50-69, 70-89, 90-109, and > 110 follicles were matured by 12, 4, 4, and 3 gravid females, respectively. These findings provide vector operators with a window of time to maximize the impact of insecticides on An oswaldoi populations. (Au)

Melatonin rhythms and pineal structure in a tropical bat, Anoura geoffroyi, that does not use photoperiod to regulate seasonal reproduction

It has been hypothesized that pineal structure and function might differ between temperature zone and tropical species of mammals because of lower amplitudes of seasonal change in photoperiod and, in some areas, less seasonal climatic variation. Anoura geoffroyi produce a single offspring in November or December of each year on the Caribbean island of Trinidad, at 10 degrees N latitude in the deep tropics. Previous work has shown that this population lacks reproductive responses to photoperiod, and must be enforcing seasonal breeding using a non-photoperiodic cue. Anoura geoffroyi have a minute, thin, and rod-like pineal gland. Throughout much of its length, the pineal courses irregularly within the ventrolateral wall of the great cerebral vein. This intimate relationship may have functional implications. Despite having a very small pineal gland, this species produced a nocturnal rise in serum melatonin. Serum melatonin levels in most individuals were below or near undetectable levels during the light period and rose to a peak averaging 100 pg/ml in the last third of the dark period. Our results indicate that, although the pineal gland of A. geoffroyi is extremely small, serum melatonin levels are comparable to those of other mammals.(AU)

Urinary fluoride excretion in Jamaica in relation to fluoridated salt

The purpose of this study was to compare the urinary fluoride levels in subtropical Jamaican just before the beginning of salt fluoridation (250mg/kg salt) in 1987 and again 20 months later. Four age groups were studied in three locations with low to intermediate fluoridation as compared with 23.7-67.4 æg/h 20 months after the beginning of the sale of fluoridated salt. The fluoride excretions obtained from 24-hour collections ranged from 169 to 485 æg/24h in 1987 and increased to 304-657 æg/24 h in 1989. In 1987, the morning fluoride excretions approximated those of French and Swiss children who had a low fluoride intake, but the fluoride levels of 1989 were similar to the data obtained from children who had an intake of 1.2-1.7 mg F/day or consumed fluoridated water (AU)

Daily variability in resting levels of cardiovascular variable in normal subjects and those with homozygous sickle cell disease

Measurements were made of cardiovascular variables and oral temperature in 16 male subjects with homozygous sickle cell disease (SS) and in 17 matched controls (AA) at 10.00 a.m, 1.00 p.m and 4.00 p.m. All subjects were in a rested state throughout. At 10.00 a.m. mean arterial pressure was lower, while heart rate, total forearm blood flow and cutaneous red cell flux in the forearm were higher in SS than AA. Vascular resistance in total forearm and forearm skin, calculated by dividing arterial pressure by blood flow or red cell flux, were lower in SS but hand cutaneous red cell flux and vascular resistance were not significantly different in SS and AA. In both SS and AA, there were parallel increase over the three sessions, in mean arterial pressure (by approximately 12 and 10 percent respectively) forearm vascular resistance (by approximately 17 and 27 percent) and hand cutaneous vascular resistance and hand cutaneous resistance (by approximately 2240 and 350 percent) whereas forearm blood flow and hand cutaneous red cell flux fell. By contrast, forearm cutaneous resistance showed no change during the day in SS, but increased progressively in AA (by approximately 75 percent). These results indicate that, during the day, there is progressive vasconstriction in forearm muscle and hand skin in SS and AA and also in forearm skin of AA that contributes to a progressive rise in the resting level of mean arterial pressure. We suggest this daily variability should be considered in studies of cardiovascular function: within a given study they should be performed at the same time of day.(AU)

Resting and ambulatory blood pressure differences in Afro-Caribbeans and Europeans

To investigate why mortality from stroke in people of Afro-Carribean origin is twice the average for England and Wales, we examined 11166 Europeans and Afro-Caribbean people in London. Age-standardized median systolic blood pressure was 6mm Hg higher (128 versus 122mm Hg) in Afro-Caribbean than European men and 17mm Hg higher (135 versus 118 mm Hg) in Afro-Carribean than European women. Migrants from West Africa and the Caribbean had similar bloood pressure. Body mass index was higher in Afro-Caribbean than European women, accounting for 4mm Hg of the systolic difference. Diabetes prevalence was 16 percent in Afro-Caribbeans and 5 percent in Europeans (P < .001), accounting for 1mm Hg of the diffference in systolic pressure in men and 2mm Hg in women. In participants not taking antihypertensive medication, mean fall in ambulatory systolic pressure between daytime and nighttime, adjusted for resting blood pressures, was 24 mm H g in Eropeans and 18 mm Hg in Afro-Caribbeans (P = 015), and percent day-night fall in systolic blood pressure adjusted for resting systolic pressure was 17 percent in Europeans and 12 percent Afro-Caribbeans (P < .05). This difference persisted when men and women and normotensive and hypertensive individuals were examined separately. We estimate that the differences in blood pressure between Afro-Caribbean and Europeans may be enough to account for ethnic differences in stroke mortality in women but not men. The reasons for the high prevalence of hypertension and related morbidity in this and other populations of African descent remain to be established (AU)

Epidemiology and control of malaria in Suriname: with special reference to Anopheles darlingi

From 1982 to 1986 a study was made on the distribution of Anopheles spp. in Suriname. Malaria is endemic in the Surinamese interior and although A. darlingi occurs all over the interior, its northward distribution is limited by savannahs and tidal movements of the rivers. At night only the A. darlingi feeds indoors and at the beginning of the night it is the most prevalent species to feed on persons outdoors. Because of a favourable waterlevel in the rivers, the number of malaria cases reached an epidemic level. A. darlingi stings mostly between 22.00 and 24.00 o'clock. Thus malaria transmission occurs mainly outdoors. Spraying the houses with DDT seemed ineffective because of the chinks in the walls. Impregnating mosquito nets with permethrin is ineffective because the mosquito nets are washed weekly. Transmission of Plasmodium falciparum occurs mainly in the Upper-Marowijne region. Priority should be given to malaria eradication in this region. A program for eradication of the vector (A. darlingi) is desirable

Observations on the seasonal incidence and diel oviposition periodicity of haemagogus mosquitoes (Diptera: Culicidae) in Trinidad, W.I.: part I

The diel oviposition periodicity of sylvan Haemagogus janthinomys Dyar in the Pt. Gourde Forest, Trinidad, West Indies was monitored weekly for 53 weeks using conventional ovitraps. During the wet season (September to November 1981 and May to September 1982) a large well-defined unimodal peak occurred six to eight hours after sunrise (comprising 94 percent of eggs laid and 91 percent occurrences). During the dry season (December 1981 to May 1982), a small less-well-defined peak occurred two to four hours before sunset (comprising 6 percent of eggs laid). The combined data showed a diurnal oviposition pattern with eggs laid from noon to sunset. The numbers of eggs and of used ovitraps found during the wet season were significantly (P<0.001) higher than those found during the dry season.(AU)

Diel biting activity of Culex (Melanoconion) caudelli in Trinidad, West Indies

The diel biting periodicity of the arbovirus vector Culex (Melanoconion) caudelli Dyar and Knab (Diptera; Culicidae) in the Aripo-Wallerfield forest, Trinidad, was studied by collecting mosquitoes attracted to mouse-baited traps at 2-hourly intervals during eight 24 h periods. Biting females of Cx. caudelli were collected during all night-time hours, 18.00-06.00 hours, within overall unimodal pattern, i.e. one well-defined peak between 22.00 and 04.00 hours. This contrasts with previous reports that Cx. caudelli is diurnally active. During the four moon phases, the period of peak biting activity varied from 22.00 to 24.00 hours at fullmoon, from 22.00 to 04.00 hours at first quarter, and from 24.00 to 02.00 hours at new moon and last quarter phases, the highest (152/24 h) being collected in the first lunar quarter and the lowest (71/24 h) in the last lunar quarter. Cloud cover and rainfall had no significant effect on the diel biting periodicity of Cx. caudelli.(AU)

Landing periodicity of the mosquito Aedes aegypti in Trinidad in relation to the timing of insecticidal space-spraying

Diel landing periodicity (biting cycle) of domestic Aedes aegypti (L.) in Trinidad, West Indies, was monitored using human bait during January-August 1980. The periodicity of females was predominantly diurnal (95.2 percent arriving during daylight or twilight) and bimodal, with consistent peaks at 06.00-07.00 and 17.00-18.00 hours. The diel periodicities at indoor and outdoor sites were virtually identical. Larger numbers of adults were collected outside than inside houses. It is recommended that the time of insecticidal ULV adulticiding should coincide with peaks in landing periodicity of the Ae. aegypti adults. (AU)

Paroxysmal nocturnal haemoglobinuria in Jamaica

There was delay of from 2 weeks 2 years before the diagnosis of praoxysmal noctural haemoglobinuria (PNH) was confirmed in 6 patients, the first to be describe from Jamaica and the English-speaking Caribbean. Three had nocturnal haemoglobinuria when they presented, but 3 others presented atypically. Then diagnosis would have been established earlier if the acidified serum (Ham) test and the sucrose haemolysis test had been performed earlier. The possibility of PNH should be investigated in patients with aplastic or refractory anaemia, in those in whom increased haemolysis is associated with iron deficiency, and with a variety of other disorders, when common causes are excluded. The pathogenesis of the haemolysis in PNH, and the variety of haematologic changes which may accompany this disorder are discussed (AU)