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1.
New Phytol ; 190(4): 968-976, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21714183

RESUMO

Phosphorus (P)-limited plants produce higher amounts of root phosphatases, but research has mostly focused on phosphomonoesterases (PMEs). Because phosphate diesters can form a significant proportion of organic P in wetlands, we aimed to determine whether wetland plants produce both root PMEs and root phosphodiesterases (PDEs), and, if so, what factors influence activities of these enzymes. We measured the activities of root PMEs and PDEs colorimetrically in a wide range of macrophytes from natural and P-enriched wetlands. Hydrolyzable P in sediments was analyzed using commercially available PMEs and PDEs. In all species, both root PMEs and PDEs were always present, and their activities were closely correlated. Sedges and broadleaved emergents had the highest activity of both enzymes, while those of floating-leaved plants were the lowest. Redundancy analysis revealed close association between root enzymes and the proportion of monoesterase- and diesterase-hydrolyzable dissolved unreactive P. Both enzymes were positively correlated with root tissue N : P ratio. Both plant and sediment traits were important when explaining differences in enzyme activities. Although the activities are related to ambient P regime, the relationship was not close enough to use root enzymes as reliable predictors of dissolved unreactive P that is hydrolyzed by sediment phosphomono- and diesterases.


Assuntos
Diester Fosfórico Hidrolases/metabolismo , Monoéster Fosfórico Hidrolases/metabolismo , Fósforo/metabolismo , Raízes de Plantas/enzimologia , Brotos de Planta/enzimologia , Belize , Nitrogênio/análise , Nitrogênio/metabolismo , Diester Fosfórico Hidrolases/análise , Monoéster Fosfórico Hidrolases/análise , Fósforo/análise , Raízes de Plantas/metabolismo , Brotos de Planta/metabolismo , Plantas/enzimologia , Plantas/metabolismo , Solo/química , Microbiologia do Solo , Áreas Alagadas
2.
PeerJ ; 9: e12331, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34820168

RESUMO

Lake Atitlán has experienced a decline in water quality resulting from cultural eutrophication. Indigenous Mayans who already face disproportionate health challenges rely directly on the lake water. Our objectives were to: (1) estimate prevalence of shedding of water-borne fecal parasites among children 5 years of age and younger, (2) assess household-reported incidence of gastrointestinal illness in children, and (3) characterize water sources, treatment, and sanitation conditions in households. We hypothesized that household use of untreated lake water results in increased risk of shedding of parasites and gastrointestinal symptoms. A cross-sectional fecal sampling and physical exam of 401 children were conducted along with WASH surveys in partnership with healthcare providers in seven communities. Fecal samples were screened for Giardia lamblia and Cryptosporidium parvum, using a rapid ELISA, with a portion examined by microscope. The prevalence of parasite shedding was 12.2% (9.7% for Giardia; 2.5% for Cryptosporidium). Risk factors for Giardia shedding included age 3 years or older (3.4 odds ratio, z-stat = 2.781 p = 0.0054), low height-for-age z-score (2.3 odds ratio, z-stat = 2.225, p = 0.0216), lack of any household water treatment (2.5 odds ratio, z-stat = 2.492, p < 0.0012), and open access to household latrine (2.04 odds ratio, z-stat = 1.992, p = 0.0464). The majority (77.3%) of households reported water treatment, boiling and gravity fed filters as the most widespread practices. The vast majority of households (92%) reported usage of a latrine, while 40% reported open and shared access beyond their household. An overwhelming majority of households reported diarrhea and fever several times per year or greater, with approximately half reporting vomiting at that frequency. Lake water use was identified as a risk factor for households reporting frequent gastrointestinal symptoms (odds ratio of 2.5, 4.4, and 2.6; z-stat of 3.10, 3.65, and 3.0; p-values of 0.0021, 0.0003, and 0.0028, for diarrhea, vomiting, and fever, respectively) in children 5 years of age and younger. The frequency of gastrointestinal illness with a strong link to lake drinking water cannot be explained by the prevalence of protozoa, and risk from other enteropathogens must be explored. Improving access to water treatment and sanitation practices could substantially reduce the parasite burden faced by developing children in the region.

3.
Ecol Appl ; 20(1): 16-29, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20349828

RESUMO

Worldwide increases in human and wildlife diseases have challenged ecologists to understand how large-scale environmental changes affect host-parasite interactions. One of the most profound changes to Earth's ecosystems is the alteration of global nutrient cycles, including those of phosphorus (P) and especially nitrogen (N). Along with the obvious direct benefits of nutrient application for food production, anthropogenic inputs of N and P can indirectly affect the abundance of infectious and noninfectious pathogens. The mechanisms underpinning observed correlations, however, and how such patterns vary with disease type, have long remained conjectural. Here, we highlight recent experimental advances to critically evaluate the relationship between environmental nutrient enrichment and disease. Given the interrelated nature of human and wildlife disease emergence, we include a broad range of human and wildlife examples from terrestrial, marine, and freshwater ecosystems. We examine the consequences of nutrient pollution on directly transmitted, vector-borne, complex life cycle, and noninfectious pathogens, including West Nile virus, malaria, harmful algal blooms, coral reef diseases, and amphibian malformations. Our synthetic examination suggests that the effects of environmental nutrient enrichment on disease are complex and multifaceted, varying with the type of pathogen, host species and condition, attributes of the ecosystem, and the degree of enrichment; some pathogens increase in abundance whereas others decline or disappear. Nevertheless, available evidence indicates that ecological changes associated with nutrient enrichment often exacerbate infection and disease caused by generalist parasites with direct or simple life cycles. Observed mechanisms include changes in host/vector density, host distribution, infection resistance, pathogen virulence or toxicity, and the direct supplementation of pathogens. Collectively, these pathogens may be particularly dangerous because they can continue to cause mortality even as their hosts decline, potentially leading to sustained epidemics or chronic pathology. We suggest that interactions between nutrient enrichment and disease will become increasingly important in tropical and subtropical regions, where forecasted increases in nutrient application will occur in an environment rich with infectious pathogens. We emphasize the importance of careful disease management in conjunction with continued intensification of global nutrient cycles.


Assuntos
Doenças Transmissíveis Emergentes/veterinária , Nitrogênio , Fósforo , Animais , Animais Selvagens , Doenças Transmissíveis Emergentes/transmissão , Ecossistema , Fertilizantes , Interações Hospedeiro-Patógeno , Humanos , Modelos Biológicos , Zoonoses
4.
Expo Health ; 12(4): 835-848, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33748532

RESUMO

Available guidance to mitigate health risks from exposure to freshwater harmful algal blooms (HABs) is largely derived from temperate ecosystems. Yet in tropical ecosystems, HABs can occur year-round, and resource-dependent populations face multiple routes of exposure to toxic components. Along Winam Gulf, Lake Victoria, Kenya, fisher communities rely on lake water contaminated with microcystins (MCs) from HABs. In these peri-urban communities near Kisumu, we tested hypotheses that MCs exceed exposure guidelines across seasons, and persistent HABs present a chronic risk to fisher communities through ingestion with minimal water treatment and frequent, direct contact. We tested source waters at eleven communities across dry and rainy seasons from September 2015 through May 2016. We measured MCs, other metabolites, physicochemical parameters, chlorophyll a, phytoplankton abundance and diversity, and fecal indicators. We then selected four communities for interviews about water sources, usage, and treatment. Greater than 30% of source water samples exceeded WHO drinking water guidelines for MCs (1µg/L), and over 60% of source water samples exceeded USEPA guidelines for children and immunocompromised individuals. 50% of households reported sole use of raw lake water for drinking and household use, with alternate sources including rain and boreholes. Household chlorination was the most widespread treatment utilized. At this tropical, eutrophic lake, HABs pose a year-round health risk for fisher communities in resource -limited settings. Community-based solutions and site-specific guidance for Kisumu Bay and similarly impacted regions is needed to address a chronic health exposure likely to increase in severity and duration with global climate change.

5.
PLoS One ; 13(4): e0195570, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29684035

RESUMO

A survey of the ecological variability within 52 populations of Schoenoplectus californicus (C.A. Mey.) Soják across its distributional range revealed that it is commonly found in nitrogen (N) limited areas, but rarely in phosphorus limited soils. We explored the hypothesis that S. californicus supplements its nitrogen demand by bacterial N2-fixation processes associated with its roots and rhizomes. We estimated N2-fixation of diazotrophs associated with plant rhizomes and roots from several locations throughout the species' range and conducted an experiment growing plants in zero, low, and high N additions. Nitrogenase activity in rhizomes and roots was measured using the acetylene reduction assay. The presence of diazotrophs was verified by the detection of the nifH gene. Nitrogenase activity was restricted to rhizomes and roots and it was two orders of magnitude higher in the latter plant organs (81 and 2032 nmol C2H4 g DW-1 d-1, respectively). Correspondingly, 40x more nifH gene copies were found on roots compared to rhizomes. The proportion of the nifH gene copies in total bacterial DNA was positively correlated with the nitrogenase activity. In the experiment, the contribution of fixed N to the plant N content ranged from 13.8% to 32.5% among clones from different locations. These are relatively high values for a non-cultivated plant and justify future research on the link between N-fixing bacteria and S. californicus production.


Assuntos
Cyperaceae/metabolismo , Fixação de Nitrogênio , Nitrogênio/metabolismo , Raízes de Plantas/metabolismo , Rizoma/metabolismo , Áreas Alagadas , Proteínas de Bactérias/metabolismo , Cyperaceae/microbiologia , Nitrogênio/química , Nitrogenase/metabolismo , América do Norte , Oxirredutases/metabolismo , Fósforo/química , Fósforo/metabolismo , Dispersão Vegetal , Proteínas de Plantas/metabolismo , Rizoma/microbiologia , Solo/química , América do Sul , Especificidade da Espécie
6.
J Am Mosq Control Assoc ; 23(3): 276-82, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17939506

RESUMO

The recapture rates of wild-caught, unengorged Anopheles vestitipennis and Anopheles albimanus females were determined at 0, 400, and 800 m from a fixed release point in Belize, Central America. Three sampling trials, each consisting of two 12-hour collections, were performed at each distance during September-October 2003. A total of 1,621 An. vestitipennis and 1,326 An. albimanus were marked and released during the course of the study. The recapture rate of An. vestitipennis was greatest at 0 m (7.9%; 44/ 556) and declined from 3.0% (16/531) at 400 m to 0.2% (1/534) at 800 m. Anopheles albimanus females were recaptured only at the 0-m distance and in extremely low numbers (1.1%; 5/446). Biting patterns for the unmarked natural populations were similar to those previously described for Belize, and recaptures for both species occurred during these normal biting times. The overall recapture rates for An. vestitipennis (3.76%; 61/ 1,621) and An. albimanus (0.38%; 5/1,326) indicate that An. vestitipennis has a higher probability of being attracted to a human habitation.


Assuntos
Anopheles/fisiologia , Transmissão de Doença Infecciosa , Voo Animal/fisiologia , Habitação , Animais , Belize , Comportamento Alimentar/fisiologia , Feminino , Humanos
7.
J Vector Ecol ; 32(2): 176-87, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18260505

RESUMO

Larval habitats of the main malaria vectors in Belize are associated with three distinctly different aquatic environments: marshes with sparse macrophytes and cyanobacterial mats (Anopheles albimanus), tall dense macrophyte marshes (An. vestitipennis), and floating detritus assemblages within freshwater rivers (An. darlingi). We assessed species-specific habitat suitability based upon nutrient characteristics using larval survival rates (SR) and wing lengths (WL) from floating habitat enclosures. Anopheles albimanus showed a high SR (81%) in all three habitats, while An. vestitipennis had a similarly high SR in its own habitat (82%) and An. darlingi's habitat (81%). Anopheles darlingi only showed high SR (85%) in its own habitat. Both An. vestitipennis and An. darlingi showed very low SR in the An. albimanus habitat. There were no significant WL differences among field-caught, laboratory-reared, and experimental populations of An. vestitipennis and An. albimanus, with the exception of An. vestitipennis experimental populations and An. vestitipennis field populations placed in the An. albimanus habitat. Habitat quality indicators, particulate organic carbon (POC), dissolved organic carbon (DOC), and particulate organic nitrogen (PON), were consistently higher in An. vestitipennis habitats than in the habitats of the other two species. Correspondingly, An. vestitipennis adults were larger when measured both as dry mass and from WL. There were no differences in dry mass, lipids, or protein content among the same species reared at different locations. We compared SR and WL among mosquitoes from shaded and unshaded containers to test whether the high mortality rates for An. vestitipennis and An. darlingi in the An. albimanus habitat were due to intense sun exposure. There were no significant differences among developmental times, survivorship, or adult size for shaded versus sun-exposed populations. This indicates that other factors such as larval toxins, predator avoidance, interspecific species competition, etc. may be responsible for the higher mortality rates in those species not adapted to this particular habitat.


Assuntos
Anopheles/crescimento & desenvolvimento , Ecossistema , Insetos Vetores/crescimento & desenvolvimento , Animais , Belize , Carbono/análise , Feminino , Larva/crescimento & desenvolvimento , Mortalidade , Nitratos/análise , Nitrogênio/análise , Fosfatos/análise , Compostos de Amônio Quaternário/análise , Luz Solar , Poluentes da Água/análise , Asas de Animais/crescimento & desenvolvimento
8.
Energy Ecol Environ ; 2(2): 95-113, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32280742

RESUMO

Cyanobacterial blooms at Lake Atitlán in Guatemala threaten and compromise the livelihood and health of local residents. Indigenous Tz'utujil, Kaqchikel, and K'iche' rely directly on lake water for drinking, bathing, cleaning, cooking, and fishing. Nonpoint source runoff and untreated wastewater pumped directly into the lake contribute to high fecal pathogen loads into source waters. Concurrent nutrient loading results in cyanobacterial blooms further compromising water quality. A lakeside municipality facing high rates of childhood gastrointestinal illness volunteered to engage in community-based participatory research (CBPR) to evaluate efficacy, utility, and longevity of filters in households. The filters consistently reduced the risk of coliforms and E. coli in household water drawn from the lake based on World Health Organization guidelines. Household surveys were simultaneously administered through a student leadership group regarding water usage, water quality, and community health. Filters demonstrated ability to reduce high loads of fecal indicators from source waters and ability to remove a cyanobacterial toxin (microcystin) at 10 µg/L in deionized water. Further studies are imperative to determine longevity of use in households and CBPR provides a powerful avenue to test efficacy of a possible intervention while engaging stakeholders and empowering community members with sustainable solutions.

9.
J Med Entomol ; 43(3): 614-22, 2006 May.
Artigo em Inglês | MEDLINE | ID: mdl-16739424

RESUMO

Anthropogenic land use changes often alter natural patterns of disease transmission. The goal of this study was to determine whether phosphorus input from sugarcane, Saccharum officinarum L., cultivation in northern Belize could pose a significant environmental impact on malaria transmission by changing vegetation structure and composition of wetlands and associated larval habitats. Our primary focus was on the increased dominance of cattail, Typha domingensis Pers., a favored habitat for Anopheles vestitipennis Dyar & Knab. A land cover classification based on satellite imagery was used to select 20 marshes impacted by agricultural runoff and 20 marshes surrounded by forest (nonimpacted). A 100-m transect was established into each of the 40 marshes. Water, vegetation, and larval sampling were conducted at the 0-, 10-, 25-, 50-, and 100-m locations along the transect. Analyses of larval density data indicated that Anopheles albimanus Wiedemann was negatively correlated with percentage of cover of Typha (R2 = 0.39, P < 0.001) but positively correlated with sparse Eleocharis cellulosa Torr. (rush) cover (R2 = 0.19, P < 0.05) and presence of cyanobacterial mats (CBM) (R2 = 0.33, P < 0.0001). An. vestitipennis was found to be positively correlated with percentage of cover of Typha (R2 = 0.19, P < 0.001). Canonical correspondence analysis identified CBM and light as the variables associated with the presence of An. albimanuts larvae, Typha cover with An. vestitipennis larvae, and Eleocharis and absence of light with Anopheles crucians (Wiedemann). A positive correlation also existed between marshes adjacent to agricultural activities and presence of An. vestitipennis (R2 = 0.37, P < 0.05). These results indicate that marshes in proximity to agricultural fields are conducive for Typha growth, thereby providing habitat for the more efficient malaria vector


Assuntos
Anopheles/fisiologia , Malária/transmissão , Agricultura , Animais , Belize , Meio Ambiente , Insetos Vetores , Larva , Densidade Demográfica , Saccharum/crescimento & desenvolvimento , Estações do Ano , Typhaceae/crescimento & desenvolvimento
10.
J Med Entomol ; 43(2): 382-92, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16619625

RESUMO

Previous studies have identified several anopheline species integral to the transmission of malaria in Belize. The highly efficient vector, Anopheles darlingi Root, is currently considered the most important. The preferred larval habitat of An. darlingi has been described as floating detritus patches, which are commonly associated with overhanging spiny bamboo, Guadua longifolia (E. Fourn.), along river margins. The objectives of this study were to use remote sensing and geographic information system (GIS) tools to 1) define the landscape features (i.e., river curvature, land cover, and house locations) associated with An. darlingi-positive breeding habitats and 2) determine the association between cleared land cover and the growth of spiny bamboo. A systematic survey was conducted in which all detritus patches of at least 1 m2 were sampled, mapped using GPS, and characterized by cause of habitat lodging. Bamboo stretches growing along the river margins also were mapped. Spatial analyses of satellite imagery found no associations between river characteristics or land cover with positive An. darlingi habitats. In addition, there was no significant difference in cleared versus forested land cover in relation to the presence or absence of bamboo. Results indicate that the average distance from homes to negative habitats was significantly greater than from positive detritus mats. Based on the land cover and river characteristics used, our results do not support the use of remote sensing as a predictive tool to locate specific areas within rivers positive for An. darlingi habitats.


Assuntos
Anopheles/fisiologia , Ecossistema , Sistemas de Informação Geográfica , Insetos Vetores/fisiologia , Animais , Belize , Previsões , Geografia , Processamento de Imagem Assistida por Computador , Larva , Malária/prevenção & controle , Malária/transmissão , Poaceae , Reprodução/fisiologia , Medição de Risco/métodos , Rios , Comunicações Via Satélite , Árvores
11.
J Am Mosq Control Assoc ; 22(3): 573-5, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17067067

RESUMO

A delayed release mechanism was designed for a mark-recapture study that evaluated the flight behavior of anopheline mosquitoes in Belize, Central America. The design prevents marked mosquitoes from being released until after a set time. The time lag allows researchers to return to collecting posts before release and reduces the potential of marked females tracking an odor plume generated during the release procedure. This is especially important in study designs evaluating temporal host-seeking behavior patterns. Detailed descriptions of the design are presented.


Assuntos
Comportamento Animal , Culicidae , Animais , Belize , Entomologia/instrumentação , Entomologia/métodos , Feminino
12.
J Vector Ecol ; 31(1): 145-51, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16859103

RESUMO

Previous studies in Belize have shown the preferred breeding habitats of the malaria vector Anopheles darlingi were floating detritus patches within riverine systems that were associated with overhanging bamboo. The present study focused on an experimental evaluation of overhanging bamboo in An. darlingi habitat selection using larval counts as an indicator of attractiveness. Four sets of 1-m2 floating screened enclosures were placed at a location with a documented presence of both larval and adult An. darlingi populations. Each enclosure set comprised a control (i.e., open water) and three other experimental treatments consisting of: 1) detritus, 2) detritus with overhanging bamboo, and 3) overhanging bamboo alone. Larvae were sampled from all treatments on Day 5, Day 11, and Day 17 post-setup. A total of 2,461 An. darlingi larvae were collected and identified from three trials conducted from March-May 2002. Of these, 1,997 larvae were sampled from detritus treatments, 256 from enclosures with bamboo and detritus, 139 from bamboo treatments, and 69 from control enclosures. The detritus treatment had a significantly higher average count of An. darlingi larvae than the other treatments (P<0.01), and no difference existed between the control treatment and the treatment containing overhanging bamboo alone (P=0.423). More importantly, enclosures containing the overhanging bamboo with detritus treatments did not have greater larval populations than the enclosures with only detritus. These data suggest that bamboo does not contribute to An. darlingi larval habitat attractiveness but may function as a barrier to surface water flow causing the lodging of debris, the preferred habitat, that will then attract gravid females for oviposition.


Assuntos
Anopheles/crescimento & desenvolvimento , Meio Ambiente , Animais , Bambusa , Belize , Larva
13.
J Vector Ecol ; 31(1): 45-57, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16859089

RESUMO

The present study utilized an experimental hut to conduct human-baited landing collections for characterizing the all-night biting patterns and seasonal densities of adult Anopheles darlingi in the centrally located Cayo District of Belize, Central America. A total of 25 all-night collections (i.e., sunset to sunrise) were conducted from January 2002 to May 2003, capturing a total of 18,878 An. darlingi females. Anopheles darlingi exhibited a bimodal nightly biting pattern with one predominate peak occurring three h after sunset and a smaller peak occurring one h prior to sunrise. Biting females were collected throughout the night in higher densities indoors (9,611) than outside (9,267) the experimental hut (O:I=1.00:1.04). Seasonal adult collections show An. darlingi densities were highest during the transitional months between the end of the wet and beginning of the dry season (January) and the end of the dry season and beginning of the wet season (May). A total of 2,010 An. darlingi females was captured in 31 two-h, human-baited landing collections performed from January to October 2002. Anopheles darlingi monthly population densities were found to have no significant associations with high or low temperatures, precipitation, or river level. However, qualitative data examination indicates an inverse relationship between river level and An. darlingi adult collections suggesting a disturbance of larval habitats. All-night biting and seasonal distribution patterns for other anopheline species are also described. None of the adult specimens collected throughout the entire study tested positive for Plasmodium spp. infection using the VecTest rapid diagnostic kit.


Assuntos
Anopheles/fisiologia , Mordeduras e Picadas de Insetos , Insetos Vetores/fisiologia , Animais , Belize , Comportamento Alimentar , Humanos , Malária/transmissão , Plasmodium/isolamento & purificação , Chuva , Rios , Estações do Ano , Esporozoítos/isolamento & purificação , Temperatura
14.
J Med Entomol ; 42(2): 95-103, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15799516

RESUMO

Oviposition site selection has been recognized as critical both for the survival and population dynamics of mosquitoes. Volatile substances released from larval habitats have been implicated as potential olfactory cues mediating oviposition. In our continuing studies of cues involved in oviposition site selection, we collected material from the larval habitats of Anopheles albimanus Wiedemann and Anopheles vestitipennis Dyar & Knab, i.e., cyanobacterial mats and Typha domingensis Pers. litter, respectively. The volatile compounds were extracted by freeze-drying the material and trapping the volatilized material on a -55 degrees C titanium condenser. For oviposition trials conducted with wild-caught females, the tested volatile materials were pipetted onto filters floating on the surface of distilled water in Teflon beakers that were placed within oviposition cages. For both species, volatile materials in low concentrations increased oviposition, assessed as egg density, whereas there was a shift to reduced oviposition at higher concentrations. Volatile effect was strongly habitat/species-specific as shown by reciprocal treatment tests.


Assuntos
Larva/crescimento & desenvolvimento , Odorantes/análise , Oviposição/fisiologia , Animais , Anopheles , Feminino , Volatilização
15.
J Am Mosq Control Assoc ; 21(4): 366-79, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16506561

RESUMO

Knowledge of the flight behavior of local vectors is of paramount importance in mosquito control programs. The following study defined the recapture rate of wild-caught, unengorged Anopheles darlingi females at 0, 400, and 800 m from a fixed release point in Belize, Central America, using a newly designed portable experimental hut. Three sampling trials, each consisting of 2 12-h collections, were performed at all distances from July 2002 to June 2003. A total of 1,185 An. darlingi were marked and released during the course of the study. The recapture rate was greatest at 0 m (29.0%; 124/428) and declined from 11.6% (37/318) at 400 m to 5.8% (21/361) at the 800-m site. There was no difference between the average number of marked mosquitoes recaptured inside the experimental hut versus outside the hut at any distance location. Recapture rates of each trial were highest during the first night's collection at all locations. Further examination of the first night data revealed a variation in the peak time of recapture by distances from the release point. The peak in nightly recapture at both the 0- and 400-m sites occurred within the first 2 h after sunset, and the peak recapture at the 800-m site occurred during the 7th h after sunset. Information from the present study is the first to describe the flight behavior of An. darlingi in Belize and will benefit in the development of adult-density risk assessments at the house level based on distances from potential vector breeding sites.


Assuntos
Anopheles/fisiologia , Controle de Mosquitos/métodos , Animais , Comportamento Animal , Belize , Densidade Demográfica
16.
J Vector Ecol ; 30(2): 235-43, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16599158

RESUMO

Mowing and burning of emergent vegetation were evaluated as potential management strategies for the control of the malaria vector, Anopheles vestitipennis, in northern Belize, Central America. The primary aim was reduction of tall dense macrophytes (dominated by Typha domingensis) as preferred larval habitat for An. vestitipennis. Nine experimental plots were established in a Typha marsh in Orange Walk District, Belize. Three plots were burned, three were treated by subaquatic mowing, and three were unaltered controls. After treatment, Typha height was most dramatically affected by the mow treatment. Plant heights at 21 and 95 days post-treatment reflected an 89% and 48% decrease, respectively, compared to pretreatment conditions. The Typha height in the burn plots was not as severely affected. Heights at 21 days post-treatment were 39% lower than those of pre-treatment vegetation, with a return to near pre-test heights by 95 days post-treatment. Both treatments resulted in a significant reduction in the number of An. vestitipennis larvae collected as compared to control plots. Conversely, the treatments resulted in increased larval densities of several other vector and pest mosquito species. Larval population densities ofAn. albimanus, Ochlerotatus taeniorhynchus, and Culex coronator were significantly higher in burn plots. In mow plots, there were significant increases in An. albimanus and Oc. taeniorhynchus larval populations. Non-target invertebrate species affected by the treatments were adult Tropisternus collaris, larval Corythrella, and adult Parapleapuella.


Assuntos
Anopheles/crescimento & desenvolvimento , Insetos Vetores/crescimento & desenvolvimento , Malária/transmissão , Controle de Mosquitos/métodos , Typhaceae/parasitologia , Animais , Anopheles/microbiologia , Belize , Meio Ambiente , Humanos , Insetos Vetores/microbiologia , Larva , Controle Biológico de Vetores , Densidade Demográfica
17.
J Am Mosq Control Assoc ; 18(4): 241-76, 2002 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12542181

RESUMO

Data from mosquito collections made in Belize, Central America, between September 1990 and April 1993 are presented. A total of 537 collections yielding 15,139 specimens are summarized. One genus, 4 subgenera, and 31 species are recorded from Belize for the 1st time. A checklist of the 111 mosquito species now known to occur in Belize is presented.


Assuntos
Culicidae , Animais , Belize , Culex , Meio Ambiente
18.
J Vector Ecol ; 28(2): 200-7, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14714669

RESUMO

A life table study was conducted for recently established colonies of Anopheles albimanus and Anopheles vestitipennis in Belize, Central America. The colonies were reared in the northern Orange Walk District under uncontrolled environmental conditions (29-32 degrees C, 87-90% RH, and 13:11 L:D photoperiod). The mean time of larval development for An. albimanus was 10.8 days for males and 11.7 days for females. Mean times for An. vestitipennis larval development were 11.3 days for males and 13.5 days for females. Anopheles albimanus exhibited a 92% survival rate from egg hatch to adult emergence, while that of An. vestitipennis was 82%. Neither species showed a sex ratio that was significantly different from 1:1. Adult male An. albimanus lived for an average of 13.6 days, while the females lived for an average of 21.2 days. The An. vestitipennis adult males lived for a mean of 14.8 days, while the females lived considerably longer with a mean of 25.6 days. The reproductive rate and age of mean cohort reproduction were calculated as 287 and 11.3 days for An. albimanus and 302 and 13.4 days for An. vestitipennis. The r/B and B/D ratios of 0.13 and 1.15, respectively, for An. albimanus and 0.1 and 1.1, respectively, for An. vestitipennis indicate that these species have a low potential for colonization.


Assuntos
Anopheles/crescimento & desenvolvimento , Tábuas de Vida , Longevidade , Reprodução , Animais , Belize , Feminino , Larva/crescimento & desenvolvimento , Masculino , Dinâmica Populacional
19.
J Vector Ecol ; 27(1): 21-30, 2002 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12125869

RESUMO

Collections of Anopheles darlingi Root and An. albimanus Wiedemann from central and northern Belize were conducted as landing captures from 6:30 to 8:00 p.m. to define spatial distributions and outdoor:indoor ratios of biting during the early evening. In central Belize, collections were made at 31 houses in riparian zones (> or = 1 km from rivers) and 14 houses in upland zones (>1 km from rivers) during the dry and wet seasons of 1993 and 1994. Females of both species were abundant in houses < or = 1 km from rivers. Females were not present in houses located in upland areas during the dry season, but were present in the wet season. A total of 63 paired collections (representing 130 individual captures) from 42 houses showed An. darlingi females were more endophagic (ratio of 1:0.6) during the early evening than were An. albimanus females (ratio of 1:0.21). Paired landing collections from 22 houses in riparian zones in April-May were analyzed in an index of species abundance (ISA). ISA values rated An. darlingi as the dominant Anopheles mosquito indoors and An. albimanus was dominant outside. Although An. darlingi and An. albimanus were abundant in riparian zones, there was no association in their numerical abundance, suggesting that different environmental factors influenced their abundance. In northern Belize, one house for each of 16 villages was sampled during April and May 1994. Large numbers ofAn. albimanus were captured outdoors in houses located in riparian and marshland areas (means of 217.5 and 247.5/1.5 personhours outdoors, respectively). Numbers of An. albimanus were low at houses located away from rivers and marshes (12.2 per collection). Anopheles darlingi was uncommon at sites in northern Belize. Proportionally fewer An. albimanus females entered houses in the north (outdoor:indoor ratio of 1:0.16) compared to the central region (ratio of 1:0.21), which probably reflects differences in house construction, anti-mosquito behavior (i.e., closing windows and doors at sunset), and insecticide treatments. The ISA gave a quantitative assessment of vector dominance in relation to the parameters of spatial distribution and numerical abundance. The index was also sensitive to the variables of indoor and outdoor biting behaviors.


Assuntos
Anopheles , Meio Ambiente , Animais , Belize , Feminino , Habitação , Mordeduras e Picadas de Insetos , Masculino , Controle de Mosquitos , Periodicidade , Dinâmica Populacional , Estações do Ano
20.
J Vector Ecol ; 27(1): 63-9, 2002 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12125874

RESUMO

We studied the impact of reduced residual spraying in Belize by developing a logistic regression model on relationships between numbers of houses sprayed (mostly with DDT) and numbers of malaria cases. We defined the "minimum effective house spray rate" (MEHSR) as the level of spraying that will prevent increases in malaria rates for a defined population. Under the total coverage approach (all houses sprayed), the MEHSR for Belize was 134.6. The model also showed that the odds for decreasing malaria is 1.086 for each increase of 10 houses sprayed per 1,000 population. In further testing, highly significant and differential changes in malaria rates were documented for paired groups of years with house spray rates that were either above or below the MEHSR. Numbers of malaria cases since 1995 are used to show how stratification methods are used in Belize to spray fewer houses (at levels below the MEHSR of 134.6).


Assuntos
DDT , Inseticidas , Malária/prevenção & controle , Controle de Mosquitos/métodos , Animais , Belize , Previsões , Habitação , Dinâmica Populacional , Análise de Regressão
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