A study to identify the presence of Aedes Spp. using BG-Sentinel® Traps and larval/pupal surveys in communities around Belmopan, Cayo District.

The knowledge of the presence of Aedes Spp. mosquitoes is very important for the prevention and control of emerging and remerging diseases caused by Arboviruses such as: Yellow fever, Dengue, Chikungunya and Zika. While Chikungunya and Dengue are endemic to Belize, Zika is currently a threat with local transmission having been established in several Caribbean and Central American Countries. The objective of the study is to survey the presence of Ae. aegypti and Ae. albopictus in the communities of San Martin, Salvapan and Las Flores, Belmopan City. The study was conducted from March 14 to April 2, 2016 whereby adult mosquitoes were captured using BG-Sentinel® Traps and larvae/pupae collection surveys were also done. Three hundred meter zone(s) were determined within localities and 1 BG-Sentinel® trap was deployed for 3 days at 24-hour intervals both indoors and outdoors at 2 residences randomly selected in each community. Larvae/Pupae collection surveys were done at 5 private premises within the predetermined zones in each of the three communities. Captured larvae and Pupae were reared for 6 days and adults obtained were used for identification. The identification of adult Ae. aegypti and Ae. albopictus was done using a stereoscopic microscope and pictorial keys that are used for the identification of mosquitoes. The presence of Ae. aegypti was identified in all 3 communities through both adult mosquito and larvae/pupae collections. However, Ae. albopictus was present only in San Martin and Salvapan communities. The presence of Ae. aegypti and/or Ae. albopictus will determine which appropriate vector control interventions are needed considering the different characteristic breeding habitats of these mosquitoes.(AU)

Manual on integrated vector management for community health workers and voluntary collaborators in Belize

The objectives of the presentation are to enable participants to identify: the vectors of malaria, dengue, chikungunya and chagas diseases; the signs and symptoms for malaria, dengue, chagas and chikungunya diseases; and the transmission cycle for malaria, dengue, chikungunya and chagas diseases.

The Mosquito Book: An awareness and activities manual promoting ecological management of urban mosquitoes

This manual is the 2005 second edition edited by Ed Boles. It provides environmental knowledge and detailed ecology of mosquitoes that encourages all to bring environmental education into their homes and environment helping to reduce mosquito breeding habits. It is designed to educate you on the different types of mosquitoes and their effects and diseases which can be transmitted to humans.

Mosquitoes and tourism in Grenada - Poster abstract

The global public health importance of mosquitoes cannot be over-emphasised. The tourist industry relies heavily on customer satisfaction and this study examined the importance of mosquitoes as a cause of dissatisfaction amongst tourists visiting Grenada. Tourists who had spent three days or more at four popular hotels were included in the study. This study also examined the species and breeding site distribution of mosquitoes in the hotels selected. Three cross sectional surveys were carried out in both the dry and wet seasons at various time intervals and ovitraps were placed in various parts of each hotel for up to a week. Eggs collected from these traps were identified. Aedes sp were more numerous than Culex sp eggs and were more numerous in the rainy season. Of the tourists interviewed by questionaire, 87 percent had been bitten by mosquitoes during their stay; 74 percent had been bitten twice, 18 percent twenty times and 8 percent more than 20 times. Seventy-seven percent (77 percent) of tourists perceived mosquitoes as a severe biting nuisance whilst 16 percent and 7 percent perceived them as moderate or mild, respectively. Biting nuisance was most severe in the wet season and the dining room was reported as the most important site where biting took place for all hotels studied. Potential breeding sites were identified and appropriate mosquito control measures have been suggested to the hotels.(AU)

Landing periodicity of Aedes aegypti with implications for dengue transmission in Trinidad, West Indies

OBJECTIVE: To monitor the diel periodicity of the Trinidad strain of Aedes aegypti (L) using human bait during January to August, 1999. METHODS: Adult mosquitoes were collected by two men, one stationed indoors and the other outdoors at one urbansite (Woodbrook) and one rural area (Tableand) for three 8-hour shifts. During each hour, light intensities were measured both indoors and outdoors at both urban and rural sites using a standard Weston Master 11 photographic light meter (Model 753). RESULT: The periodicity of females was both diurnal and nocturnal, with 90 percent arriving during daylight and twilight and 10 percent during the night. The pattern of landing was trimodal, with consistent peaks at 0700 h, 1100 h and 1700 h. The diel periodicities at indoor and outdoor urban sites were virtually identical. In contrast, the periodicities in rural areas were different with no nocturnal activities being recorded at indoor and outdoor sites. At both urban and rural sites, larger numbers of adults were collected outside rather than inside houses. Significant correlations between light intensities and mosquito landing patterns were observed CONCLUSIONS: Changing light intensities were possibly responsible for changing landing pattern of Ae aegypti mosquitoes.(AU)

Spatial distribution of insecticide resistance in Caribbean populations of Aedes aegypti and its significance

To monitor resistance to insecticides, bioassays were performed on 102 strains of the dengue vector Aedes aegypti (L.) from 16 countries ranging from Suriname in South America and through the chain of Caribbean Islands to the Bahamas, where the larvicide temephos and the adulticide malathion have been in use for 15 to 30 years. There was wide variation in the sensitivity to the larvicide in mosquito populations within and among countries. Mosquito strains in some countries such as Antigua, St Lucia, and Tortola had consistently high resistance ratios (RR) to temephos, ranging from 5.3 to 17.7. In another group of countries - eg. Anguilla and Curacao - mosquitoes had mixed levels of resistance to temephos (RR = 2.5 - 10.6), and in a third group of countries, including St. Kitts, Barbados, Jamaica, and Suriname, mosquitoes had consistently low levels of resistance to temephos (RR = 1-4.6) (P < 0.05). On occasion significantly different levels of resistance were recorded from neighboring A. aegypti communities, which suggests there is little genetic exchange among populations. The impact of larval resistance expressed itself as reduced efficacy of temephos to kill mosquitoes when strains were treated in the laboratory or in the field in large container environments with recommended dosages. Although a sensitive strains continued to be completely controlled for up to 7 weeks, the most resistant strains had 24 percent survival after the first week. By week 6, 60 percent to 75 percent of all resistant strains of larvae were surviving the larval period. Responses to malathion in adult A. aegypti varied from a sensitive population in Suriname (RR = 1.3) to resistant strains in St. Vincent (RR = 4.4), Dominica (RR = 4.2), and Trinidad (RR = 4.0); however, resistance was generally not on the scale of that observed to temephos in the larval stages and had increase only slightly when compared to the levels that existed 3 to 4 years ago. Suggestions are made for a pesticide usage policy for the Caribbean region, with modifications for individuals countries. This would be formulated based on each country's insecticide-resistance profile. Use of physical and biological control strategies would play a more critical role than the use of insecticides.(AU)

Natural variation in blood-feeding kinetics of four mosquito vectors

The blood-engorgement kinetics of Anopheles aquasalis, Aedes aegypti, Haemagogus janthinomys, and Culex quinquefasciatus were determined under laboratory conditions using females collected from three sites in Trinidad. Most An. aquasalis, Ae. aegypti, and Hg. janthinomys completed probing within 70 s but Cx. quinquefasciatus had the longest gut filling time (222.8 s). Aedes aegypti and Hg. janthinomys had similiar gut filling durations, 87.7 s and 90.4 s, respectively. More than 70 percent of An. aquasalis, Ae. aegypti, Cx. quinquefasciatus, and Hg. janthinomys showed prediuresis. Anopheles aquasalis exhibited the shortest mean duration of prediuresis (77.3 s) and Cx. quinquefasciatus the longest (526.9 s). Most individual mosquitoes spent less time filling their guts than in prediuresis. Overall, An aquasalis exhibited the shortest total feeding time (135.7 s) and Cx. quinquefasciatus the longest (661.9 s). Individual An. aquasalis mosquitoes showed a high degree of variability in their ability to agglutinate human erythrocytes immediately upon blood engorgement, with individuals agglutinating <25 percent of the ingested erythrocytes and others >/= 90 percent. Among Ae. aegypti and Cx. quinquefasciatus, the proportion showing agglutination varied from 0 percent (67 percent and 69 percent respectively) to <50 percent. The parity of the field collected mosquito vectors had no significant effect on probing, duration of blood-feeding, duration of prediuresis, or erythrocyte agglutination. The inter- and intra-specific variation in blood-feeding and erythrocyte processing observed for the four vector species collected from the field in Trinidad are described in terms of vector competence and evolution of these behaviors (AU)

Seasonal abundance, biting cycle and parity of the mosquito Haemagogus leucocelaenus in Trinidad, West Indies

Adult female populations of Haemagogus leucocelaenus (Dyar and Shannon), the sylvan vector of yellow fever, were monitored weekly during 1981-82 by human collectors on the ground at Point Gourde in Chaguaramas Forest, 16 km west of Port-of-Spain, Trinidad. Hg.leucocelaenus showed only diurnal landing activity, from 06.00 to 18.00 hours (sunrise to sunset, universal time), with a single peak of activity between 10.00 and 14.00 hours. Densities of Hg.leucocelaenus during the wet season (May-November) were about double the level recorded during the dry season (December-April). Monthly parous rates averaged 53.9 percent (range 25-90 percent) and some females were up to five pars. Retained eggs (range 2-6, mean 4/female) were found in the ovaries of 0.34 percent of landing females, all of which had stage 1 ovarian follicles for the next gonotrophic cycle. Therefore blood-feeding is not inhibited by egg retention. Hg.leucocelaenus vector potential is reappraised in the light of these findings (AU)

Country-wide prevalence of Ascogregarina Culicis (Apicomplexa: Lecudinidae), a protozoan parasite of Aedes Aegypti in Trinidad, West Indies

The prevalence of the gregarine parasite Ascogregarina culicis was determined for Aedes aegypti populations in Trinidad, West Indies. Over 5 months, a total of 5,651 Ae. aegypti larvae were collected and identified from 419 sites throughout Trinidad as part of a national dengue surveillance program. Ascogregarina culicis infections were detected in 13.4 percent of 1,986 Ae. aegypti larvae dissected. In 7 of 8 countries or major subdivisions where this parasite was detected in Trinidad, the prevalence per locality ranged from 9.6 to 17.1 percent with an associated parasite density of 19.1-51.9 trophozoites/larva. Confirming that Ae. aegypti populations in Trinidad are highly susceptible to infection with A. culicis parasites, experimental studies showed that a strain of A. culicis from Florida readily infected 3 strains of Ae. aegypti from Trinidad with essentially no associated mortality. This report extends the known geographic range of A. culicis in Ae. aegypti populations and represents one of the first country-wide surveys for this gregarine parasite (AU)

Proportions of eggs laid by Aedes aegypti on different substrates within an ovitrap in Trinidad, West Indies

Ovitraps were exposed outdoors during wet and dry seasons in Trinidad to determine the proportions of eggs laid on three substrates: the widely-used hardboard 'paddle' (P), the water surface (W) and the inside surface of the ovitrap wall (S) in three types of blackened ovitrap: round, glass (RG), round, plastic (RP) and rectangular, plastic (SP). Of the 3556 eggs obtained, most (86.4 percent) were laid during the wet season when statistically significant differences were detected between substrates but not between ovitrap types. Most eggs (>80 percent) were laid on P, significantly fewer (P<0.005) on W, on S and on W+S, thus confirming the superiority of the paddle as a device for monitoring oviposition activity. Implications of these findings for the interpretation of Aedes studies using ovitraps are discussed (AU)

Water storage and dengue in Trinidad and Tobago: community perception and reality - abstract

A knowledge, attitude and practices (KAP) survey of 591 householders and inspection of 753 households for production of the dengue vector Aedes aegypti revealed that as many as 78 percent of households in Trinidad and Tobago stored water. Tanks (63 percent), drums/barrels (29 percent) and buckets (26 percent) were the commonest potential vector production sites, while drums >cans>buckets>tyres, proved to be the major actual producers of Ae aegypti. However, most of these were perceived as "useful by 100 percent of the population; 60 percent thought that old tyres were "useful" and only containers such as coconut shells and small bottles were perceived by 40 percent of the population as "garbage". Special messages of mosquito source reduction will need to be designed. Dengue was recognized as a "serious" illness but only 54 percent were aware of its manifestations. The urban population of Woodbrook where the experience of dengue (16.3 percent) was highest could better tell of the symptoms of dengue (56.8 percent). Conversely, in Tobago with no history of the disease, only 18.3 percent knew of any symptom of the illness. The community that had experienced the highest dengue prevalence as a whole showed least mosquito production - based on the house, container and Breteau indices for the whole country. The authors conclude that health education messages which emphasize the symptoms of Dengue and especially Dengue Haemorrhagic Fever (DHF) and link the transmission of these diseases to the nuisance mosquito, Ae, aegypti, may be one of the most important tools encouraging behaviour modification. This could lead to reduced mosquito production and a mitigation of dengue transmission (AU)

From "forest malaria" to "bromeliad malaria": a case-study of scientific controversy and malaria control

The article analyses the evolution of knowledge and rationale of control of a special case of malaria transmission based on Bromelia-Kerteszia complex. Since bromeliaceae function as a 'host of the carrier' and were previously associated with natural forests, the elucidation of bromeliad malaria historically elicited controversies concerning the imputation of Kerteszaie as transmitters as well as over control strategies directed to bromelia eradication (manual removal, herbicides and deforestation), use of insecticides and chemoprophylaxis. Established authority, disciplinary traditions, conceptual premises and contemporary criteria for validating knowledge in the field partly explain the long time gap since Adolpho Lutz announced as the beginning of the century the existence of a new mosquito and breeding site as responsible for a 'forest malaria' epidemic occurring at a high altitude. The article brings attention to how economic, political and institutional determinants played an important role in redefining studies that led both in Trinidad and Brazil to the recognition of the importance of kerteszia transmission, including urban areas, and establishing new approaches to its study, most relevant of all the concurrence of broad ecological research. The article then describes the Brazilian campaign strategies which showed significant short-term results but had to wait four decades to achieve the goal of eradication due to the peculiar characteristics of this pathogenic complex. Finally, it brings attention to the importance of encompassing social values and discourses, in this case, environmental preservation, to understanding historical trends of malaria control programs(AU)

A model of the transmission of dengue fever with an evaluation of the impact of ultra-low volume (ULV) insecticide applications on dengue epidemics

We have developed a deterministic susceptible, exposed, infectious, resistant or removed (SEIR) model of dengue fever transmission that enables us to explore the behavior of an epidemic, and to experiment with vector control practices. Populations of both host and vector are divided into compartments representing disease status (susceptible, exposed, infectious, and , for humans, resistant), and the flow between compartments is described by differential equations. Examination of the equilibrium points leads to a formulation of the basic reproduction rate (Zo) of the dsease. With a base set of parameters, Zo=1.9 and the model realistically reproduces epidemic transmission in an immunologically naive population. Control of adult mosquitoes by ultra-low volume (ULV) aerosols is simulated by an abrupt decrease in vector densities, followed by gradual recovery of the vector population. The model indicates that ULV has little impact on disease incidence, even when multiple applications are made, although the peak of the epidemic may be delayed. Decreasing the carrying capacity of the environment for mosquitoes, and thus the basic reproduction rate of the disease, by source reduction or other means, is more effective in reducing transmission. (AU)

Laboratory colonization and maintenance of Toxorhynchites moctezuma

A colony of Toxorhynchites moctezuma was established at the Caribbean Epidemiology Centre in Trinidad in 1984. Toxorhynchites moctezuma was maintained in cages with high humidities. Eggs were deposited most frequently in a cut bicycle tire containing water. A minimum of 42 h was required for hatching, but 94 percent hatched between 43 and 51 h. Aedes aegypti larvae were supplied as prey. Larval development times varied with the quantity of prey offered, but when fed ad lib, peak developmental time was 18 days. Mean pupal developmental time was 5.5 days. Although only 12 percent of larvae survived to pupation in 3 years of production, our experience indicates this species would be a likely candidate for mass production and release.(AU)

Seasonal incidence and diel oviposition periodicity of Haemagogus mosquitoes (Diptera: Culicidae) in Trinidad, W.I. Part III. Haemagogus celeste (Dyar and Nunez Tovar) and Haemagogus leucocelaenus (Dyar and Shannon).

The seasonal incidence and diel oviposition patterns of sylvan Haemagogus celeste and Hg. leucocelaenus in the Pt. Gourde Forest, Trinidad, were monitored weekly for 53 consecutive weeks using conventional ovitraps. During the dry season peak oviposition by Hg. celeste occured between 10:00 and 12:00 hours, and that by Hg. leucocelaenus between 12:00 and 14:00 hours; during the wet season peak oviposition by both species occurred between 12:00 and 14:00 hours. Diurnal patterns of oviposition were observed for both species during the wet and dry seasons. The numbers of ovipositions and of eggs laid during the wet season were, for both species, significantly higher (P greater than 0.001) than those observed during the dry season. (AU)

Yellow fever studies in Trinidad, 1988-1989: attempts to demonstrate Transovarial Transmission of yellow fever virus in Haemagogus mosquitoes collected in nature

Subsequent to an epizootic of yellow fever (YF) in monkeys and the isolation of yellow fever (YF) virus from sylvatic mosquitoes in December, 1988 and January, 1989 in south-east Trinidad, ovitrapping for mosquito eggs was started in January, 1989, in an attempt to demonstrate transovarial transmission of the virus. Multi-paddle ovitraps were used. From a total of 52,632 eggs collected in various parts of the country, the following species of mosquitoes were reared: Haemagogus janthinomys (54 percent), Hg. leucocelaenus (32 percent), Aedes insolitus (12 percent), Hg. equinus (1 percent). When mosquito eggs were removed from the hard board paddles then vacuum-treated for hatching, the process proved very economical in storage space. Most eggs were obtained at the start of the wet season, four to five months after the isolation yellow fever virus from wild caught adult mosquitoes and monkey carcasses. When adult mosquitoes reared from eggs were processed for yellow fever virus, no virus was detected from any of the mosquito pools to indicate that transovarial transmission had occurred (AU)

Aedes aegypti surveillance at the airports in Trinidad and Tobago: an eight year study

A Programme of surveillance for Aedes aegypti mosquitoes was instituted at the airports of Trinidad and Tobago following an epidemic of yellow fever in 1978. The Surveillance system consisted of the use of ovitraps to collect Ae. aegypti eggs. After a period of eight years and the examination of 54,136 ovitrap paddles, 53 paddles were found positive. Only one of the positives came from Tobago. In Trinidad, ovitraps set in the car park and areas easily accessible to the general public were the ones most frequently found positive for Ae. aegypti eggs. The quick detection of positive paddles and close liaison with the Ministry of Health allowed prompt treatment of the affected areas, reducing the risks of possible transport of these mosquitoes by aircraft to other countries (AU)

Yellow fever: evolution of ideas concerned with demonstrating the natural occurrence of transovarial transmission of virus in mosquitoes

In November 1978, an outbreak of disease among wild simians of south Trinidad alerted officials to the presence of jungle yellow fever (YF). Learning of the epizootic and having recently been involved in studies establishing transovarial transmission (TOT) of YF virus, this laboratory urged Trinidad workers to undertake demonstration of the natural occurence of TOT in the forest environment. The idea as well as a suggested procedural protocol involving vector mosquitoes (Haemagogus spp.) was accepted and acted upon. Initial procedures called for undertaking studies in areas where sick or dead monkeys were observed, collecting larvae as well as adult female Haemagogus from which eggs were to be obtained, hatched, and the ensuing larvae reared to adults and tested for virus. As time passed, various problems were encountered necessitating changes in field procedures. The most important was the substitution of ovitraps for adult female collections as a source of eggs. By 1980, the epizootic/epidemic was waning. Funding for additional studies became available from Canadian sources and the author was invited to be a consultant. Field and laboratory procedures were again modified and streamlined. Described are: (1) choice of field sites, (2) choice of ovitraps, (3) siting of ovitraps, (4) frequency of collections, (5) laboratory procedures, (6) search for male Haemagogus and female ovipositing activity, and (7) duration of a TOT study and conclusions (AU)