Dengue fever is one of the most severe insect-borne viral infections; it is potentially fatal and is currently endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, Southeast Asia and the Western Pacific, with Southeast Asia and the Western Pacific being the most seriously affected (WHO, 1997). It is a flu-like illness but may develop into the more serious dengue haemorrhagic fever/dengue shock syndrome, which can result in death. In the Caribbean, virological evidence of dengue fever was first obtained in the 1950s, although the disease is believed to have existed there for the past 200 years (Ehrenkranz et al, 1971). The outbreak of dengue haemorrhagic fever in Cuba in 1981, which affected almost half the population, is considered to be one of the most important events in the history of dengue in the Americas (CAREC, 1997). Since this event there have been confirmed or suspected cases of dengue haemorrhagic fever almost every year in the American region. The last large epidemic in Jamaica occurred about ten years ago.

OBJECTIVE:To examine the effects of increasing larval rearing temperatures on the resistance status of Trinidadian populations of Aedes aegypti to organophosphate (OP) insecticides.METHODS:In 2007-2008, bioassays and biochemical assays were conducted on A. aegypti larvae collected in 2006 from eight geographically distinct areas in Trinidad (Trinidad and Tobago). Larval populations were reared at four temperatures (28 ± 2ºC, 32ºC, 34ºC, and 36ºC) prior to bioassays with OP insecticides (fenthion, malathion, and temephos) and biochemical assays for esterase enzymes.RESULTS:Most larval populations reared at 28 ± 2ºC were susceptible to fenthion (>98% mortality) but resistant to malathion and temephos (< 80% mortality). A positive association was found between resistance to OP insecticides and increased activities of α- and β-esterases in larval populations reared at 28 ± 2ºC. Although larval populations reared at higher temperatures showed variations in resistance to OPs, there was a general increase in susceptibility. However, increases or decreases in activity levels of enzymes did not always correspond with an increase or decrease in the proportion of resistant individuals reared at higher temperatures.CONCLUSIONS:Although global warming may cause an increase in dengue transmission, based on the current results, the use of insecticides for dengue prevention and control may yet be effective if temperatures increase as projected.

Dengue fever is one of the most severe insect-borne viral infections; it is potentially fatal and is currently endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, Southeast Asia and the Western Pacific, with Southeast Asia and the Western Pacific being the most seriously affected (WHO, 1997). It is a flu-like illness but may develop into the more serious dengue haemorrhagic fever/dengue shock syndrome, which can result in death. In the Caribbean, virological evidence of dengue fever was first obtained in the 1950s, although the disease is believed to have existed there for the past 200 years (Ehrenkranz et al, 1971). The outbreak of dengue haemorrhagic fever in Cuba in 1981, which affected almost half the population, is considered to be one of the most important events in the history of dengue in the Americas (CAREC, 1997). Since this event there have been confirmed or suspected cases of dengue haemorrhagic fever almost every year in the American region. The last large epidemic in Jamaica occurred about ten years ago.

AbstractInsecticide resistance is an important factor in the effectiveness ofAedes aegypticontrol 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 ofAe. aegyptiand the underlying biochemical mechanisms. Nine populations ofAe. aegyptilarvae 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 susceptibleAe. aegyptistrain 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 β 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−1and 1.0 mg l−1for deltamethrin, permethrin and DDT, respectively; and the RTs for deltamethrin, permethrin and DDT were 30, 75 and 120 min, respectively. AllAe. aegyptipopulations 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 allAe. aegyptipopulations. All, except three populations, showed increased levels of β-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 ofAe. 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.

Like other countries around the globe where conditions existed for the parasites causing hookworm disease to thrive, this disease was a serious problem to settlers in countries of the Commonwealth Caribbean, i.e. those countries that were formerly part of the British Empire. Early in the 20th century, the Rockefeller Foundation (RF) assisted the southern United States in controlling this disease. Soon other countries requested assistance and the Rockefeller Foundation responded by creating their International Health Commission to target the problem. Guyana (then British Guiana) was the first country where work was started. Through a system of chemotherapy, sanitation with the provision of latrines and health education the RF assisted the Commonwealth Caribbean countries during the period 1914-1925 in controlling the disease. Most countries continued the programmes started by the Rockefeller Foundation and this paper provides evidence through a series of surveys to show that hookworm disease is no longer a public health problem.

Aedes aegypti larvae from 8 sites in Trinidad and 1 in Tobago were assayed against temephos, malathion, and fenthion using the Centers for Disease Control and Prevention time-mortality based bioassay method. Resistance ratios (RRs) and resistance thresholds (RTs) for each insecticide were calculated in relation to the Caribbean Epidemiology Center reference susceptible strain. Results showed that the Hale land Park and Tobago strains were susceptible to fenthion and malathion, respectively (RRs < 1), while the San Fernando strain had a high RR (33.92) to malathion. All other strains had low-level resistance to fenthion and malathion. Resistance to temephos was more intense with 4 strains showing high-level resistance. The established RT was 60 min for fenthion, 75 min for bendiocarb, and 120 min for temephos and malathion. At the RTs, all Trinidad strains were resistant to temephos (11.50-74.50% mortality), 7 resistant to fenthion (21.25-78.75% mortality), and 5 resistant to malathion (56.25-77.50% mortality). The other strains were incipiently resistant (80-97% mortality). Despite the discrepancies between the RR levels and RT status, it is evident that the organophosphate insecticide resistance is prevalent in Trinidad and Tobago populations of Ae. aegypti. These results suggest that operational failure could soon occur and alternative strategies should be developed and implemented to reduce the probability of further selection pressure on resistant Ae. aegypti populations in Trinidad and Tobago.

Bioassays and biochemical assays were conducted on eight Trinidadian strains of Aedes aegypti larvae to determine the involvement of biochemical mechanisms in resistance to insecticides. Larval strains were assayed to dichlorodiphenyltrichloroethane (DDT), bendiocarb, temephos and permethrin, using the Centers for Disease Control and Prevention (CDC) time-mortality bioassay method. A Resistance Threshold (RT) was calculated for each insecticide in relation to the CAREC reference susceptible Ae. aegypti strain and larval strains with <80% mortality were considered to be resistant. Biochemical assays were performed to determine the activities of nonspecific esterases (α- and β-), PNPA-esterases, mixed function oxidases (MFO), glutathione-S-transferases (GST) and acetylcholinesterase (AChE) enzymes which are involved in insecticide resistance in mosquitoes. Enzyme profiles of each strain were compared with those of the CAREC reference susceptible strain by Kruskal–Wallis and Dunn's multiple comparison tests (p<0.05). The CAREC 99th percentile was calculated for each enzyme and the percentage of individuals with enzyme activities above that of the CAREC 99th percentile was calculated. Activities were classified as unaltered (<50%), incipiently altered (15–50%) or altered (>50%) for each strain.The established RTs for permethrin and bendiocarb were 30 and 75min, respectively; and 120min for DDT and temephos. All strains were resistant to DDT (1.00–40.25% mortality) and temephos (11.50–74.50% mortality) while six strains were resistant to bendiocarb (51.50–78.50% mortality) and five to permethrin (6.50–42.50% mortality). Biochemical assays revealed that the median activity levels for all enzymes varied significantly (p<0.05). The Curepe strain had incipiently altered levels of α-esterase while the other seven strains had altered activity with five of them registering 100%. The St Clair strain showed altered activity levels of β-esterase while three strains had incipiently altered levels. The majority of strains had altered activity of MFO enzymes but only the St Clair strain showed altered activity of GST. PNPA-esterases activity was unaltered in all strains and only the Haleland Park strain showed altered remaining AChE activity in the presence of propoxur.Elevated levels of enzymes (incipiently altered or altered), except in the case of PNPA-esterases, show that biochemical resistance may play an important role in the manifestation of insecticide resistance in Trinidadian populations of Ae. aegypti. It is therefore important for insecticide resistance surveillance to be ongoing as the detection of resistance before it spreads throughout an entire population makes it possible for early intervention.

OBJECTIVES:Given the occurrence of autochthonous malaria in non-endemic island countries in the last 10 years, this study evaluates the risk factors for malaria transmission in the malaria "endemic and "non-endemic" countries of the Caribbean region.DESIGN:Data on imported and autochthonous malaria for the 27-year period (1980-2006) were gathered from surveillance units in the 21 Caribbean Epidemiology Centre (CAREC) Member Countries (CMCs) via the CAREC epidemiology unit. Anopheles mosquito data were also gathered from various sources. The vector and malaria data were correlated to determine the current risk of malaria transmission.RESULTS:Imported cases. For the 26-year period (1980-2005), there were 897 reported cases in the CMC islands. Jamaica (38.4%) > Trinidad and Tobago (19.5%) > Bahamas (15.8%) > Cayman Islands (12.5%) were mostly affected. Only the smallest CMCs eg Anguilla and British Virgin Islands reported no imported malaria. Indigenous malaria. Over the same time period, malaria was seen mainly in the three mainland countries of Guyana (514 386 cases) > Suriname (275 361) > Belize (85 313). However, for the period 1995-2005, Belize and Guyana reported reduction in case numbers of 84% and 54% respectively. At the same time, Suriname reported a cyclical pattern of reported cases resulting in 77% increase in cases between 1995 and 2005. "Non-endemic" CMCs such as Trinidad and Tobago, and Bahamas, did report autochthonous malaria. In 2006/7, Jamaica reported 340 P falciparum cases, coming just 1-2 years after a massive 505% increase in imported malaria in the region--88% in Jamaica. Anopheles spp: There was a rich diversity of Anopheles mosquitoes--29 spp. in CMCs. Mainland CMCs and nearby island countries had most spp. recorded. Smaller countries with limited ecological niches such as St Kitts, Anguilla, Turks and Caicos Islands (TCI) and Bermuda had little or no Anopheles spp. Two main Anopheles axes were identified--An albimanus in the northern CMCs and An aquasalis in the southern Caribbean.CONCLUSION:All the essential malaria transmission conditions--vector, imported malaria organism and susceptible human host--now exist in most CMCs. A call is now made for enhanced surveillance, vector control and anti-malaria skills to be established in CMCs, in particular in: Recognizing the possible impact of climate change on the spread of anopheles and malaria transmission. Improving vector control skills for anopheles in CMCs. Strengthening malaria surveillance skills. Upgrading malaria therapy and prophylaxis. Emphasizing malaria prevention and educationfor all community and professional sectors.

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.

This study was conducted to guide the prioritisation of efforts to manage Cryptosporidum contamination of drinking water supplies in Trinidad, W.I. The main objective was to investigate the relative importance of three main types of sources of Cryptosporidium oocysts: urban, agriculture and wildlife. Weekly surface water samples were collected from 19 sites distributed among three watersheds, and examined for the presence of oocysts. A stratified random sampling design was used with each watershed representing one of the three main sources of oocysts listed above. Results showed a significant association between watershed and the occurrence of positive samples (chi(2)=16.523, d.f. =2, p = 0.000), indicating that land use influenced the presence of oocysts. Urban and forested lands were the two most important sources of oocysts. There was no apparent association between agriculture and the presence of oocysts, and there was no significant difference between the percentage of positive samples at sites below agricultural facilities and sites not associated with agriculture within a single watershed (chi(2)=2.45, d.f. =1, p = 0.117). We conclude that urban and wildlife are the main types of sources of Cryptosporidium contamination of surface water, whereas the contribution of agriculture is minor.

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.

This study was carried out to provide some evidence for the interruption of transmission of lymphatic filariasis (LF) among schoolchildren in Trinidad and Tobago. A cross-sectional survey for LF antigenaemia was performed among 63 (13.2%) of the 479 primary schools located in eight administrative (and geographical) regions of Trinidad and Tobago. From these communities, 2597 schoolchildren aged 6–12 years were sequentially selected for a survey of bancroftian antigenaemia. From each child, 100 μl (finger-prick) whole blood sample was applied to a Binax immunochromatographic card test (ICT), and read for the presence of antigenaemia. The ICT results showed a negative finding for LF antigenaemia and suggest that LF transmission has been interrupted in the survey areas.

Lymphatic filariasis and malaria are endemic in Guyana, South America. To determine the prevalence of concomitant infections, we conducted a 1-year survey of febrile patients attending the malaria (day) and filariasis (night) clinics in Georgetown. In all, 1278 thick blood smears were collected: 769 for filariasis, of which 103 were positive for Wuchereria bancrofti, and three for both W. bancrofti and malaria parasites; and 509 for malaria, 21 of which tested positive for malaria and 17 for both malaria and filariasis. The age groups and sex of the infected persons with malaria and W. bancrofti are described. These results suggest that the incidence of concomitant infections in Guyana may be quite low but efforts should be made to reduce the disease burden in Georgetown, Guyana.

The seroprevalence of toxocariasis was investigated in 1997/98 in 1009 schoolchildren (aged 5-12 years) throughout Trinidad. Infection, as measured by titre, was found to be high compared to values obtained from children in other countries. Using an excretory-secretory antigen and performing an ELISA test, it was found that 62.3% of children had an IgG antibody titre of > or = 1:100, indicating exposure to the parasite, while 27.2% had a titre of > or = 1:800, indicating a current or recent infection. Relationships were explored between seroprevalence and host factors including age, sex, school location, and other risk factors including geophagia, thumb-sucking, presence of other gastrointestinal-tract parasitism and pet ownership. There was no significant relationship between age and the presence of current or recent infection (P = 0.746). Boys were significantly more commonly infected than girls as were the attendees of rural schools versus urban schools (P < 0.001). The percentage of seropositivity among children varied widely from school to school. Pet ownership and the absence of pipe-borne water in the household were found to be significantly associated with positive serology (P < 0.05). Clinical symptoms mostly associated with positive serology were eczema, seizures and chronic cough. Recommendations derived from this study include health education in order to increase the public awareness on the transmission of the disease, de-worming all dogs and cats periodically and the curbing of stray dogs and cats. Environmental sanitation measures should include keeping children away from contaminated areas and practising proper hygiene after play.

The 185 patients who presented at the dermatology clinic of Georgetown Public Hospital, Guyana, between 1992 and 1998, with skin ulcers indicative of American cutaneous leishmaniasis (ACL) were retrospectively reviewed. The laboratory-confirmed cases of ACL were identified and the corresponding data were analysed for risk factors such as age, gender, areas of residence and of possible exposure to the causative agent (Leishmania braziliensis guyanensis), ethnic origin, longevity of the ulcers, and treatment regimes prior to the definitive diagnosis. Eighty-one (43%) of the 185 subjects were confirmed to be infected with Le. b. guyanensis. Although 53 (66%) of the cases lived in or close to the capital city, Georgetown, most of the cases had travelled to (and probably been infected in) region X in the interior of Guyana (32%) or regions VII (23%), VIII (23%), IX (11%), VI (5%), I (3%) or III (3%), usually because they were involved in the mining (41%) or lumber (21%) industries, the army or hunting. Almost all (95%) of the cases were male and most (58%) were aged 20-39 years. In general, the cases had had their skin lesions for many days before presenting for treatment: 46% for 1-5 weeks and 3% for > 6 months. Prior to presentation at the clinic, many of the cases had attempted to cure themselves, using local herbal remedies (37%), antibiotics and antifungal remedies (39%), other creams (5%), household chemicals (9%) or miscellaneous remedies such as lead salts (especially lead sulphate) and battery acid, all without success. Recommendations are made for an epidemiological study of active ACL among forest workers, eco-tourists and residents of high-risk areas. Diagnostic centres need to be sited in the regions most at-risk, particularly in or near environments in which the main vectors - sandflies such as Lutzomyia umbratilis, Lu. anduzei and Lu. whitmani - are known to be prevalent.

Two populations of Aedes aegypti, i.e. Phnom Penh (temephos-treated area) and Kampong Cham (area untreated with temephos) were evaluated for their susceptibility to temephos. Larval bioassays were carried out in accordance with WHO standard methods. Results showed that, when compared with the WHO diagnostic dosage of 0.02mg/l, the Phnom Penh population was resistant (LC95: 0.034mg/l) whereas that of Kampong Cham was susceptible (LC95: 0.015mg/l). 95% confidence intervals of 0.0298 - 0.0382 and 0.0115 - 0.0193, respectively, did not overlap, indicating that the difference in susceptibility between the two populations was significant. Resistance of Ae. aegypti to temephos appears to be incipient in Cambodia. More studies are requried with wider representations of localities.