Seroepidemiology of selected alphaviruses and flaviviruses in bats in Trinidad.

A serosurvey of antibodies against selected flaviviruses and alphaviruses in 384 bats (representing 10 genera and 14 species) was conducted in the Caribbean island of Trinidad. Sera were analysed using epitope-blocking enzyme-linked immunosorbent assays (ELISAs) specific for antibodies against West Nile virus (WNV), Venezuelan equine encephalitis virus (VEEV) and eastern equine encephalitis virus (EEEV), all of which are zoonotic viruses of public health significance in the region. Overall, the ELISAs resulted in the detection of VEEV-specific antibodies in 11 (2.9%) of 384 bats. Antibodies to WNV and EEEV were not detected in any sera. Of the 384 sera, 308 were also screened using hemagglutination inhibition assay (HIA) for antibodies to the aforementioned viruses as well as St. Louis encephalitis virus (SLEV; which also causes epidemic disease in humans), Rio Bravo virus (RBV), Tamana bat virus (TABV) and western equine encephalitis virus (WEEV). Using this approach, antibodies to TABV and RBV were detected in 47 (15.3%) and 3 (1.0%) bats, respectively. HIA results also suggest the presence of antibodies to an undetermined flavivirus(es) in 8 (2.6%) bats. Seropositivity for TABV was significantly (P<0.05; χ2) associated with bat species, location and feeding preference, and for VEEV with roost type and location. Differences in prevalence rates between urban and rural locations were statistically significant (P<0.05; χ2) for TABV only. None of the aforementioned factors was significantly associated with RBV seropositivity rates.

Diel activity patterns of male Aedes albopictus in the laboratory.

This study was conducted to investigate the flight and dispersal behavior of male Aedes albopictus under laboratory conditions. Two different methods, the Observer and Ethovision software devices, were used to determine the total duration, the mean and maximum flight speed, and the distance covered by these mosquitoes. During 24 h, mosquitoes were more active from 0800 to 1200 h and from 1700 to 2100 h than during the rest of the day. Male Ae. albopictus displayed different activities at different times. The flight activity was 47 min and 57 sec over 24 h. During this period, sugar-fed males flew an average distance of 236.20 m at an average speed of 8.5 cm/sec. The unfed males flew significantly faster than recently fed males, with maximum flight speeds of 44.9 cm/sec and 33.6 cm/sec, respectively. The time used for resting (22 h 2 min +/- 13 min) was significantly higher (P < 0.0001) than walking and flying times (68 min +/- 10 sec and 49 min +/- 5 min, respectively). Overall, both methods allowed observations on flight activity, and the camera recordings allowed these activities to be quantified.

Studies on the post-oviposition blood-feeding behaviour of Aedes aegypti (L.) (Diptera: Culicidae) in the laboratory.

The blood-feeding behaviour of the Trinidad strain of Aedes aegypti was studied, under laboratory conditions, using one female per cage and monitoring blood feeding immediately, 12, and 24 hours after oviposition. To get large numbers of females that had newly completed their first gonotrophic cycle, the diel oviposition periodicity was conducted using single females per cage and monitoring at 2-hour intervals. The diel oviposition periodicity showed a small morning peak (8%) during the first 2 hours of the photophase after which oviposition declined: during the second half of the photophase, oviposition increased reaching a peak comprising 56% of eggs (G = 59·9, P>0·01) between 16:00 and 18:00 hours. At post-oviposition hour 0, only five (10%) of the females accepted a blood meal but at post-oviposition hour 12, significantly more (G = 46·98, P>0·02) females, 35 (70%) accepted a blood meal. This pattern was consistently observed when females were offered blood meals at 12 and 24 hours after completing their first gonotrophic cycle. Multiple feeding was observed among the blood-feeding females and the results of this study are discussed in the context of disease transmission patterns and physiological mechanisms which control their blood-feeding behaviours.

Impact of road networks on the distribution of dengue fever cases in Trinidad, West Indies.

This study examined the impact of road networks on the distribution of dengue fever cases in Trinidad, West Indies. All confirmed cases of dengue hemorrhagic fever (DHF) observed during 1998 were georeferenced and spatially located on a road map of Trinidad using Geographic Information Systems software. A new digital geographic layer representing these cases was created and the distances from these cases to the nearest classified road category (5 classifications based on a functional utility system) were examined. The distance from each spatially located DHF case to the nearest road in each of the 5 road subsets was determined and then subjected to an ANOVA and t-test to determine levels of association between minor road networks (especially 3rd and 4th class roads) and DHF cases and found DHF cases were located away from forests, especially 5th class roads). The frequency of DHF cases to different road classes was: 0% (1st class roads), 7% (2nd class roads), 32% (3rd class roads), 57% (4th class roads) and 4% (5th class road). The data clearly demonstrated that both class 3 and class 4 roads account for 89% of nearby dengue cases. These results represent the first evidence of dengue cases being found restricted between forested areas and major highways and would be useful when planning and implementing control strategies for dengue and Aedes aegypti mosquitoes.

Characterisation of DDT and pyrethroid resistance in Trinidad and Tobago populations of Aedes aegypti.

Insecticide resistance is an important factor in the effectiveness of Aedes aegypti control and the related spread of dengue. The objectives of this study were to investigate the status of the organochlorine dichlorodiphenyltrichloroethane (DDT) and pyrethroid (permethrin and deltamethrin) resistance in Trinidad and Tobago populations of Ae. aegypti and the underlying biochemical mechanisms. Nine populations of Ae. aegypti larvae from Trinidad and Tobago were assayed to DDT and PYs using the Centers for Disease Control and Prevention (CDC) time-mortality-based bioassay method. A diagnostic dosage (DD) was established for each insecticide using the CAREC reference susceptible Ae. aegypti strain and a resistance threshold (RT), time in which 98-100% mortality was observed in the CAREC strain, was calculated for each insecticide. Mosquitoes which survived the DD and RT were considered as resistant, and the resistance status of each population was categorised based on the WHO criteria with mortality <80% indicative of resistance. Biochemical assays were conducted to determine the activities of α and ß esterases, mixed function oxidases (MFO) and glutathione-S-transferases (GST) enzymes which are involved in resistance of mosquitoes to DDT and PYs. Enzymatic activity levels in each population were compared with those obtained for the CAREC susceptible strain, and significant differences were determined by Kruskal-Wallis and Tukey's non-parametric tests (P<0.05). The established DDs were 0.01 mg l(-1), 0.2 mg l(-1) and 1.0 mg l(-1) for deltamethrin, permethrin and DDT, respectively; and the RTs for deltamethrin, permethrin and DDT were 30, 75 and 120 min, respectively. All Ae. aegypti populations were resistant to DDT (<80% mortality); two strains were incipiently resistant to deltamethrin and three to permethrin (80-98% mortality). Biochemical assays revealed elevated levels of α-esterase and MFO enzymes in all Ae. aegypti populations. All, except three populations, showed increased levels of ß-esterases; and all populations, except Curepe, demonstrated elevated GST levels.Metabolic detoxification of enzymes is correlated with the manifestation of DDT and PY resistance in Trinidad and Tobago populations of Ae. aegypti. The presence of this resistance also suggests that knock down (kdr)-type resistance may be involved, hence the need for further investigations. This information can contribute to the development of an insecticide resistance surveillance programme and improvement of resistance management strategies aimed at combatting the spread of dengue in Trinidad and Tobago.

The diel oviposition periodicity of Aedes aegypti (L.) (Diptera: Culicidae) in Trinidad, West Indies: effects of forced egg retention.

The diel oviposition periodicity of two groups of Aedes aegypti females (Trinidad strain), (i) thoses allowed access to oviposition sites and (ii) females forced to retain-eggs for four days, were studied under laboratory conditions using one female per cage and monitoring by changing substrates every two hours. The individual females which were allowed access to oviposition sites showed peak oviposition between 16.00-18.00 h (50% of eggs), whereas individuals forced to retain eggs for four days showed a similar pattern but with a significantly (P<0.001) larger peak oviposition between 16.00-18.00 h (94% of eggs). However, females forced to retain eggs laid most or all of their eggs in one container (84%), while females given access to oviposition sites distributed their eggs among 2-4 containers. The results of this study are discussed in the context of the strength of the circadian rhythms, oviposition strategies and its impact on vector control activities.

Dengue cases and Aedes aegypti indices in Trinidad, West Indies.

This study was conducted to determine whether any relationships exist between Aedes aegypti indices, dengue seroprevalence and dengue transmission in County Victoria, Trinidad, West Indies. The cardinal points surveillance method was used to evaluate 50 suspected dengue fever (DF) cases. Thirty-three (33) confirmed DF cases were fully investigated within 48h of clinical diagnosis. Using retrospective data collected during the previous year (2003-2004) and study data, key premises and key containers were determined. Ninety-two percent of the houses were considered key premises, and 66% (22/33) of the houses with dengue positive cases harboured Ae. aegypti immature stages. These results showed that significantly (P<0.001) more adults (1050 vs 493) and immatures were collected during dengue case investigations than during routine inspection and treatment cycles. In addition, when the DF diagnosis was made the pupae per person rates increased from 0.65 to 1.35 with significantly (P<0.001) larger numbers of Ae. aegypti females emerging daily, increasing from 221 to 472.5. That is, the mosquito density required for DF transmission may be high for Trinidad given the high seroprevalence rates (94% among pregnant women). These results suggest that dengue transmission occurs, not at a fixed entomologic figure/quantity but rather at a variable level based on numerous factors including seroprevalence, mosquito density and climate. These findings have implications for effective programs: by combining cardinal points and the key premises approaches; vector control programs can now target the most productive containers in key premises thus reducing dengue transmission levels.

Oviposition strategies adopted by gravid Aedes aegypti (L.) (Diptera: Culicidae) as detected by ovitraps in Trinidad, West Indies (2002-2006).

Aedes aegypti oviposition strategies were studied weekly over a period of 5 years (2002-2006) in Curepe, Trinidad using modified ovitraps. From a total of 23,293 ovitraps collected, 10,156 were collected in the months of the dry season, with 3041 positive (30%) containing 99,577 Ae. aegypti eggs. In contrast, during the wet season from 13,137 ovitraps collected, 10,652 were positive (81.9%), containing 192,209 Ae. aegypti eggs. When, the number of eggs collected and the number of positive ovitraps were divided into different egg number categories, <30, 31-60, 61-90 and >91, significantly more eggs (G=89.6; d.f.=4; P<0.001) and more positive ovitraps (P<0.001) were collected within the <30 eggs range, followed by the egg categories 31-60, 61-90 and >91 eggs. The patterns of oviposition displayed by Ae. aegypti during the early, mid and late wet and dry seasons showed a significant (F=102.8; d.f.=5; P<0.002) decline in the number of eggs and oviposition occurrences from the early dry season to the late dry season among egg categories, <30 and 31-60 but no significant (F=3.98; d.f.=4; NS) decline in the other egg categories. In contrast, during the early, mid and late wet season, significant (F=209.8; d.f.=5; P<0.02) increases were observed in the number of eggs and positive ovitraps collected among egg categories <30, 31-60, and 61-90 but with similar numbers of eggs and oviposition occurrences recorded within the >91 egg category. These results suggest that the oviposition strategies adopted depend on numerous factors including the physical state of the oviposition site, the presence of eggs from conspecific females, whether the same or different individuals and the number or clutch size already present on the oviposition site. Therefore vector control workers should employ source reduction strategies to remove the small containers which may harbour 1-30 eggs and treat the larger permanent containers like water drums which may contain >60 eggs and may be the sites of superoviposition in nature. These combined strategies can effectively control the vector populations and reduce dengue transmission in Ae. aegypti infested countries.

Impact of pre-seasonal focal treatment on population densities of the mosquito Aedes aegypti in Trinidad, West Indies: a preliminary study.

A new pre-seasonal focal treatment strategy against Aedes aegypti L. (Diptera: Culicidae) mosquitoes is described for the first time. It was evaluated for 25 weeks using ovitraps, and larval and pupal surveys in the townships of Curepe (treated) and St. Joseph (untreated), Trinidad, West Indies. Both townships were similar with respect to number of houses, size of human populations, the number of Ae. aegypti infested houses and containers. In March 2003, a total of 9403 containers were inspected, of which 1.4 per cent in Curepe (63/4499) and 1.3 per cent in St. Joseph (64/4904) were positive for Ae. aegypti immature stages. Curepe had a lower percentage (12.7 per cent) of the main type of breeding container present (small miscellaneous containers) than St. Joseph (28.1 per cent). Following focal treatment during the month of April (2-3 weeks before the onset of the rainy season), the Ae. aegypti population declined significantly (P>0.01) from a Breteau index (BI; proportion of containers positive for larvae and pupae) of 19.0 to a minimum of 6.0 and a pupae/person index (PI) of 1.23 to a minimum of 0.35 in May, while in the untreated town of St. Joseph, the BI steadily increased from 23 to 38 and the PI rose from 0.96 to 2.00 in August. Similar declines in other measures of population density (the number of positive houses and number of eggs collected in ovitraps) were observed in Curepe, while St. Joseph maintained PI of >1.50 and BI of >28. Furthermore, the Curepe Ae. aegypti population did not return to pre-treatment levels until 9-11 weeks after treatment, far beyond the 6 weeks normally expected during vector suppression campaigns.

Aedes aegypti in Jamaica, West Indies: container productivity profiles to inform control strategies.

OBJECTIVE: To describe the Aedes aegypti container profile in the three parishes of Portland, St. Anns and St. Catherine, Jamaica. METHOD: Traditional stegomyia and pupae per person indices. RESULTS: A total of 8855 containers were inspected. A. aegypti were breeding in 19.2% of the 4728 containers in Portland, in 6.7% of the 2639 containers in St. Ann, and in 27.2% of the 1488 containers in Tryhall Heights, St. Catherine. Container types differed between Portland (P > 0.02) on one hand and St. Ann and Tryhall Heights, St. Catherine on the other hand: there were with no vases or potted plants with water saucers in St. Ann and St. Catherine. A. aegypti were breeding in more containers in St. Catherine (38%) (38% in wet season and 21% in the dry season) than in Portland (19%) or St. Ann (6%), both of which had more containers but A. aegypti breeding in fewer: 17.7% and 11.2% in the wet and 20.4% and 3.5% in the dry seasons respectively. The daily production of adult mosquitoes in the three study sites was 1.51, 1.29 and 0.66 adult female mosquitoes per person in Portland, St. Ann and St. Catherine during the dry season and 1.12, 0.23 and 1.04 female mosquitoes per person in the wet season respectively. CONCLUSION: All three communities are at risk for dengue outbreaks and vector control should concentrate on reducing the mosquito populations from the most productive containers before a new dengue virus serotype is introduced into Jamaica.

Aedes aegypti in Jamaica, West Indies: container productivity profiles to inform control strategies

OBJECTIVE: To describe the Aedes aegypti container profile in the three parishes of Portland, St. Anns and St. Catherine, Jamaica.METHOD: Traditional stegomyia and pupae per person indices.RESULTS: A total of 8855 containers were inspected. A. aegypti were breeding in 19.2% of the 4728 containers in Portland, in 6.7% of the 2639 containers in St. Ann, and in 27.2% of the 1488 containers in Tryhall Heights, St. Catherine. Container types differed between Portland (P > 0.02) on one hand and St. Ann and Tryhall Heights, St. Catherine on the other hand: there were with no vases or potted plants with water saucers in St. Ann and St. Catherine. A. aegypti were breeding in more containers in St. Catherine (38%) (38% in wet season and 21% in the dry season) than in Portland (19%) or St. Ann (6%), both of which had more containers but A. aegypti breeding in fewer: 17.7% and 11.2% in the wet and 20.4% and 3.5% in the dry seasons respectively. The daily production of adult mosquitoes in the three study sites was 1.51, 1.29 and 0.66 adult female mosquitoes per person in Portland, St. Ann and St. Catherine during the dry season and 1.12, 0.23 and 1.04 female mosquitoes per person in the wet season respectively.CONCLUSION: All three communities are at risk for dengue outbreaks and vector control should concentrate on reducing the mosquito populations from the most productive containers before a new dengue virus serotype is introduced into Jamaica.

Impact of pre-seasonal focal treatment on population densities of the mosquito Aedes aegypti in Trinidad, West Indies: a preliminary study.

A new pre-seasonal focal treatment strategy against Aedes aegypti L. (Diptera: Culicidae) mosquitoes is described for the first time. It was evaluated for 25 weeks using ovitraps, and larval and pupal surveys in the townships of Curepe (treated) and St. Joseph (untreated), Trinidad, West Indies. Both townships were similar with respect to number of houses, size of human populations, the number of Ae. aegypti infested houses and containers. In March 2003, a total of 9403 containers were inspected, of which 1.4% in Curepe (63/4499) and 1.3% in St. Joseph (64/4904) were positive for Ae. aegypti immature stages. Curepe had a lower percentage (12.7%) of the main type of breeding container present (small miscellaneous containers) than St. Joseph (28.1%). Following focal treatment during the month of April (2-3 weeks before the onset of the rainy season), the Ae. aegypti population declined significantly (P>0.01) from a Breteau index (BI; proportion of containers positive for larvae and pupae) of 19.0 to a minimum of 6.0 and a pupae/person index (PI) of 1.23 to a minimum of 0.35 in May, while in the untreated town of St. Joseph, the BI steadily increased from 23 to 38 and the PI rose from 0.96 to 2.00 in August. Similar declines in other measures of population density (the number of positive houses and number of eggs collected in ovitraps) were observed in Curepe, while St. Joseph maintained PI of >1.50 and BI of >28. Furthermore, the Curepe Ae. aegypti population did not return to pre-treatment levels until 9-11 weeks after treatment, far beyond the 6 weeks normally expected during vector suppression campaigns. The results suggest that timely application of pre-seasonal focal treatment with temephos together with standard control measures, such as source reduction of the most productive containers, can reduce the Breteau index to <5 and the pupae/person index to <0.71 (i.e., below the suggested dengue transmission thresholds for Trinidad), and extend the duration of vector suppression.

The diel oviposition periodicity of Aedes aegypti (L.) (Diptera: Culicidae) in the laboratory: substrate-movement effect.

The diel oviposition periodicity of females of the LSHTM strain of Aedes aegypti was studied, under laboratory conditions, using one female/cage and monitoring, by changing the substrate, every 1, 2, 4 or 24 h. The individual females monitored at hourly intervals showed peak oviposition at 18.00-19.00 hours (a period when 44% of the eggs observed were laid) whereas the individuals monitored at two-hourly intervals showed peak oviposition between 16.00-18.00 hours (38% of eggs). The four-hourly monitoring gave a result that was similar to that of the two-hourly monitoring, with 79% of eggs laid between 14.00-18.00 hours, indicating an earlier peak in oviposition than seen with the one-hourly monitoring. Care should therefore be taken when conducting similar studies in the laboratory and when comparing or considering data derived from experiments in which different monitoring intervals have been employed.

The elderly in Trinidad: health, social and economic status and issues of loneliness.

OBJECTIVES: To determine the general health and social status of elderly persons surveyed in Trinidad and to explore issues of loneliness. METHOD: An island-wide survey of persons aged 65 years and older was conducted in early 2002 in Trinidad Eight hundred and forty-five (845) elderly persons were chosen using systematic random sampling. The main survey instrument for data collection was a questionnaire that included structured as well as open-ended questions. The subjects were chosen in a house-to-house survey conducted in all eight counties in Trinidad. Elderly people who were unable to comprehend the questions were excluded from the survey. RESULTS: Those selected ranged in age from 65-102 years and represented all the ethnic groups in Trinidad. These elderly persons lived in a wide range of housing situations. The majority lived in the homes of family members (57%) and 16% lived on their own. A large proportion (80%) had at least one chronic medical problem, although 44% reported their health as "fairly good" or "good". More than a half of the males (53%) and 67% of the females were taking at least one prescribed medicine. The main sources of income were old age pension (85%) and National Insurance (15%). Thirty-three per cent reported feelings of loneliness. This figure includes 28% of those who did not live alone. CONCLUSION: The data revealed that across all ethnic groups more than one-third of the sample reported themselves to be in fair to good health. Many of these elders were lonely because their relatives were quite occupied with their own affairs.

Investigations of dengue-2 susceptibility and body size among Aedes aegypti populations.

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary global vector for dengue virus (DENV), yet considerable genetic variation exists among populations in terms of its competence to vector DENV. Variability in adult body size has also been observed among various mosquito populations and several studies have reported a relationship between body size and arbovirus dissemination, although most of these relied on artificially derived variation in body size. Here we examine the relationship between body size and disseminated DENV infection among 10 Ae. aegypti populations reared under optimum laboratory conditions. Body size variability was inferred from wing length measurements and DENV competence was evaluated as the proportion of individuals with disseminated infections following exposure to the dengue-2 JAM1409 strain. There were significant differences in mean wing lengths among populations (anova, F(9,22)= 7.10, P < 0.0001), ranging from 2.16 mm (Bangkok population) to 2.79 mm (MOYO-S [susceptible] population). We also observed significant differences among some populations in mean DENV infection rates (Waller-Duncan K-ratio t-test), ranging from 19.54% (MOYO-R [refractory] population) to 56.60% (MOYO-S population). However, we did not observe evidence for significant interactions between body size and DENV dissemination. We suggest that either the two traits are genetically independent or that our ability to detect interactions between them was limited by their respective inheritances as quantitative traits.

A knowledge, attitude and practices study of the issues of climate change/variability impacts and public health in Trinidad and Tobago, and St Kitts and Nevis.

OBJECTIVE: To determine the level of understanding of the issues of climate change (CC)/variability (CV) and public health by populations of St Kitts and Nevis (SKN) and Trinidad and Tobago (T&T) and to find whether respondents would be willing to incorporate these values into strategies for dengue fever (DF) prevention. DESIGN AND METHODS: Using a cluster sampling system, representative samples of the communities of SKN (227) and T&T (650) were surveyed for responses to a questionnaire document with questions on the impact of climate variability on health, the physical environment, respondents' willingness to utilize climate issues to predict and adapt to climate variability for DF prevention. Data were analyzed by Epi Info. RESULTS: Sixty-two per cent SKN and 55% T&T of respondents showed some understanding of the concept of climate change (CC) and distinguished this from climate variability (CV). With regard to causes of CC, 48% SKN and 50% T&T attributed CC to all of green houses gases, holes in the ozone layer burning of vegetation and vehicular exhaust gases. However some 39.3% SKN and 31% (T&T) did not answer this question. In response to ranking issues of life affected by CC/CV in both countries, respondents ranked them: health > water resources > agriculture > biodiversity > coastal degradation. The major health issues identified for SKN and T&T respondents were: food-borne diseases > water-borne diseases > heat stresses; vector-borne diseases were only ranked 4th and 5th for SKN and T&T respondents respectively. There was in both countries a significant proportion of respondents (p < 0.001) who reported wet season-related increase of DF cases as a CC/CV link. Respondents identified use of environmental sanitation (ES) at appropriate times as a method of choice of using CC/CV to prevent DF outbreaks. More than 82% in both countries saw the use of the CC/CV information for DF prevention by prediction and control as strategic but only 50-51% were inclined to become personally involved. Currently, only 50% SKN and 45% T&T respondents claimed current involvement in DF vector surveillance and control in the last two days. CONCLUSION: Despite the fact that knowledge and attitudes did not always coincide with practices of using ES for DF prevention, in both countries, even with CC/CV tools of prediction being available, it seems that respondents could be persuaded to use such strategies. There is a need for demonstration of the efficacy of CC/CV information and promotion of its usefulness for community involvement in DF and possibly other disease prevention.

The diel oviposition periodicity of Aedes aegypti (L.) (Diptera: Culicidae) in the laboratory: density disturbance.

The diel oviposition periodicities of the LSHTM and Trinidad strains of Aedes aegypti were studied under laboratory conditions, using different mosquito densities in the cages and monitoring at 2-h intervals. With both strains, the peak in oviposition occurred earlier in the day when there was only one female in a test cage (16.00-18.00 hours) than when 25 or 500 females were held in a cage (18.00-20.00 hours). It therefore appears that the numbers of females in the cages can affect the diel oviposition periodicity of Ae. aegypti in the laboratory and that, therefore, caution is necessary when using and comparing data from related laboratory studies in which the ovipositing mosquitoes have been held at various densities.

A knowledge, attitude and practices study of the issues of climate change/variability impacts and public health in Trinidad and Tobago, and St Kitts and Nevis / Un estudio de conocimientos, actitudes y prácticas (CAP) de los problemas del cambio climático/variabilidad de los impactos y salud pública en Trinidad y Tobago y St Kitts Nevis

OBJECTIVE: To determine the level of understanding of the issues of climate change (CC)/variability (CV) and public health by populations of St Kitts and Nevis (SKN) and Trinidad and Tobago (T&T) and to find whether respondents would be willing to incorporate these values into strategies for dengue fever (DF) prevention. DESIGN AND METHODS: Using a cluster sampling system, representative samples of the communities of SKN (227) and T&T (650) were surveyed for responses to a questionnaire document with questions on the impact of climate variability on health, the physical environment, respondents' willingness to utilize climate issues to predict and adapt to climate variability for DF prevention. Data were analyzed by Epi Info. RESULTS: Sixty-two per cent SKN and 55% T&T of respondents showed some understanding of the concept of climate change (CC) and distinguished this from climate variability (CV). With regard to causes of CC, 48% SKN and 50% T&T attributed CC to all of green houses gases, holes in the ozone layer burning of vegetation and vehicular exhaust gases. However some 39.3% SKN and 31% (T&T) did not answer this question. In response to ranking issues of life affected by CC/CV in both countries, respondents ranked them: health > water resources > agriculture > biodiversity > coastal degradation. The major health issues identified for SKN and T&T respondents were: food-borne diseases > water-borne diseases > heat stresses; vector-borne diseases were only ranked 4th and 5th for SKN and T&T respondents respectively. There was in both countries a significant proportion of respondents (p < 0.001) who reported wet season-related increase of DF cases as a CC/CV link. Respondents identified use of environmental sanitation (ES) at appropriate times as a method of choice of using CC/CV to prevent DF outbreaks. More than 82% in both countries saw the use of the CC/CV information for DF prevention by prediction and control as strategic but only 50-51...

OBJETIVO: Determinar los niveles de comprensión de los problemas del cambio climático (CC)/ variabilidad (CV) y salud pública por parte de las poblaciones de St Kitts y Nevis (SKN) y Trinidad y Tobago (T&T), y averiguar si los encuestados estarían dispuestos a incorporar estos valores en las estrategias para la previsión de la fiebre del dengue (FD). DISEÑO Y MÉTODOS: Usando un sistema de muestreo por conglomerados, muestras representativas de las comunidades de SKN (227) y de T&T (650) fueron encuestadas mediante un cuestionario en el que se les pedía responder preguntas sobre el impacto de la variabilidad del clima sobre la salud, el ambiente físico, y la disposición de los encuestados a aprovechar las cuestiones del clima para predecir y adaptarse a la variabilidad climática a fin de prevenir la FD. Los datos fueron analizados mediante Epi Info. RESULTADOS: Sesenta y dos por ciento de los encuestados de SKN y el 55% de los de T&T, mostraron cierta comprensión del concepto de cambio climático (CC) y fueron capaces de diferenciarlo de la variabilidad climática (CV). En relación con las causas del CC, el 48% (SKN) y el 50% (T&T) atribuyó el CC a los gases de efecto invernadero, los agujeros en la capa de ozono, la quema de la vegetación, y los gases de escape de vehículos.

Seroprevalence of dengue in Trinidad using rapid test kits: a cord blood survey.

A cross-sectional sero-epidemiological study was conducted to determine the prevalence of dengue in Trinidad. Two commercial rapid test kits, PanBio Dengue Duo IgM and IgG Rapid Strip Test and the Bio-Check Plus Dengue G/M Cassette Test (Brittney) were used. The immunosorbent assay (ELISA) (FOCUS Technologies, California) was used as the control. One hundred and twenty five cord blood samples were collected (46 from Mt. Hope Women's Hospital (MH) and 79 from the San Fernando General Hospital (SF)). All blood samples were tested in accordance with the two rapid kits and ELISA assay manufacturer's instructions. From 125 cord blood samples, the IgG FOCUS ELISA results showed 93.5 and 95% infections at MH and SF, respectively. Whereas the Brittney and PanBio kits showed 10.9 and 5.1%, and 26.1 and 50.6% for MH and SF, respectively. Based on the FOCUS ELISA (control) assays, the combined seroprevalence rate from north and south Trinidad was 94.4%. IgG and IgM sensitivity and specificity levels were higher in the PanBio than Brittney test kits. The high seroprevalence rates observed in Trinidad are discussed to stimulate more research to explain this phenomenon and to prevent the Southeast Asian scenario from developing in the Americas.

Climate, mosquito indices and the epidemiology of dengue fever in Trinidad (2002-2004).

Between January 2002 and December 2004, a population-based study on the effects of climate and mosquito indices on the incidences of dengue fever (DF) and dengue haemorrhagic fever (DHF) was conducted in Trinidad, West Indies. The incidence of DF was 5.05 cases/1000 population in 2002, largely as the result of a major outbreak, but declined to 0.49 case/1000 in 2004. The monthly Aedes aegypti (L.) Breteau indices (BI) did not decline over the 3-year study period, however, but increased from a mean of 29 in 2002 to one of 36 in 2004, with seasonal variations (BI of 30-46 and 20-34 were recorded in the wet and dry seasons, respectively). No significant correlations were observed between temperature and DF or DHF incidence but rainfall was found to be significantly correlated with DF incidence, with a clearly defined 'dengue season', between June and November, in two of the study years. The apparent decline in dengue transmission since 2002 appears to be largely attributable to the development of 'herd immunity' in the general population and not to the attempts at vector control. Since the introduction of new serotypes or the fading of the herd immunity could lead to an explosive epidemic of dengue in Trinidad, there is clearly a need for continued surveillance.