Significant changes in physical and biological systems are occurring on all continents and in most oceans, with a concentration of available data in Europe and North America. Most of these changes ...are in the direction expected with warming temperature. Here we show that these changes in natural systems since at least 1970 are occurring in regions of observed temperature increases, and that these temperature increases at continental scales cannot be explained by natural climate variations alone. Given the conclusions from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report that most of the observed increase in global average temperatures since the mid-twentieth century is very likely to be due to the observed increase in anthropogenic greenhouse gas concentrations, and furthermore that it is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica, we conclude that anthropogenic climate change is having a significant impact on physical and biological systems globally and in some continents.
. Elevated levels of enzymes show that biochemical resistance may play an important role in the manifestation of insecticide resistance in Trinidadian populations of
Aedes aegypti.
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▶ ...Detoxification enzymes involved in insecticide resistance in most Trinidadian
Aedes aegypti strains. ▶ PNPA-esterase not associated with temephos resistance. ▶ iAChE not important in most
Ae. aegypti field strains.
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 75
min, respectively; and 120
min 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.
Early in the 20th century, the Rockefeller Foundation (RF) assisted the southern United States in eradicating this disease. Soon other countries requested assistance and the Rockefeller Foundation ...responded by creating their International Health Commission to target the problem. Display omitted
► The hookworm programme saw the introduction and development of pubic health systems with units dedicated to health education (taking the message to the community using public lectures and films), environmental sanitation, public health legislation, and laboratory services which became the forerunner to the development of primary health care centres which are now permanent features in Ministries of Health in the Caribbean as well as other countries of the world. ► The upward economic and social mobility of the people enabled them to have modern privies, wearing of shoes even by farmers were also partly responsible for the reductions of infections. ► Further, the continuing ritual of mothers who now use new purgatives such as mebendazole, albendazole and flubendazole to purge their children also helped in reducing infections of hookworms and other geohelminths.
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 Haleland 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.
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 ≥ 1: 100, indicating exposure to the parasite, while 27·2% had a titre of ≥ 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.
Summary
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.
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.
Objetivo. Examinar los efectos del aumento de las temperaturas de desarrollo larvario sobre el estado de resistencia a los insecticidas organofosforados de las poblaciones de Aedes aegypti en ...Trinidad. Métodos. En 2007 y 2008 se llevaron a cabo ensayos biológicos y bioquímicos en larvas de A. aegypti recogidas en el 2006 de ocho áreas geográficamente separadas en Trinidad (Trinidad y Tabago). Las poblaciones larvarias se desarrollaron en cuatro temperaturas (28 + ó - 2gradosC, 32gradosC, 34gradosC y 36gradosC) antes de los ensayos biológicos con insecticidas organofosforados (fentión, malatión y temefós) y los análisis bioquímicos para las enzimas de esterasa. Resultados. La mayoría de las poblaciones larvarias que se desarrollaron a 28 + ó - 2gradosC fueron susceptibles al fentión (mortalidad mayor que o igual a 98%) pero resistentes al malation y al temefós (mortalidad < 80%). Se encontró una asociación positiva entre la resistencia a los insecticidas organofosforados y la mayor actividad de alfa y beta-esterasas en las poblaciones larvarias que se desarrollaron a 28 + ó - 2gradosC. Aunque las poblaciones larvarias que se desarrollaron a temperaturas mayores mostraron variaciones en la resistencia a los organofosforados, hubo un aumento general de la sensibilidad. Sin embargo, los aumentos o las disminuciones en los niveles de actividad de las enzimas no siempre se correspondieron con un aumento o disminución en la proporción de individuos resistentes desarrollados a las temperaturas más altas. Conclusiones. Aunque el recalentamiento del planeta puede causar un aumento de la transmisión del dengue, según los resultados de este estudio el uso de insecticidas para la prevención y el control del dengue todavía puede ser eficaz si las temperaturas aumentan según lo proyectado. Palabras clave Culicidae; aedes; control de mosquitos; resistencia a los insecticidas; insecticidas organofosforados; temperatura ambiental; Trinidad y Tobago. 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 + or - 2degreesC, 32degreesC, 34degreesC, and 36degreesC) prior to bioassays with OP insecticides (fenthion, malathion, and temephos) and biochemical assays for esterase enzymes. Results. Most larval populations reared at 28 + or - 2degreesC were susceptible to fenthion (greater than or equal to 98% mortality) but resistant to malathion and temephos (< 80% mortality). A positive association was found between resistance to OP insecticides and increased activities of alpha- and beta-esterases in larval populations reared at 28 + or - 2degreesC. 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. Key words Culicidae; aedes; mosquito control; insecticide resistance; insecticides, organophosphate; temperature; Trinidad and Tobago.
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 priorities of public health planners are often at variance with the community's own environmental sanitation priorities and perspectives. Public opinion about individual, collective, and ...governmental responsibilities in addressing these issues and priorities is of particular importance when designing community-based programs. In a study conducted in Trinidad and Tobago on knowledge, attitudes, and practice regarding dengue, its prevention and control, a high level of awareness about dengue and its etiology was evident, but there was poor understanding of the symptoms and hence little concern about the health risks associated with it. The most important household pest problem identified by the respondents was related to mosquito nuisance, particularly from night-biting mosquitoes. Rodents were also a major concern perceived as being responsible for economic losses, ruined food, and a health hazard. Unreliable water supply, a factor associated with Aedes aegypti abundance, was an environmental sanitation issue of major importance to householders in rural areas. No correlation was found between knowledge of dengue and levels of Ae. aegypti abundance as measured by larval surveys of the respondents' premises. The study gave a clear indication of the need for broad-based environmental sanitation strategies when planning community-based vector control initiatives for the prevention and control of dengue in Trinidad and Tobago.
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