Chemical pruning of plants.

The lower alkyl esters of the C(8) to C(12) fatty acids and the C(8) to C(10) fatty alcohols selectively kill or inhibit the terminal meristem without damaging the axillary meristems, foliage, or stem tissue of a wide variety of plants. The axillary meristems develop at nearly the same time as those of plants whose terminal meristems have been removed manually. The concentration of the fatty acid esters and alcohols required to kill the terminal meristem range from 0.025 to 0.05M for herbaceous plants, 0.05 to 0.16M for semi-woody plants, and 0.16 to 0.27M for woody plants.

Seasonal abundance of anopheline mosquitoes and their association with rainfall and malaria along the Matapí River, Amapá, [corrected] Brazil.

Three communities separated by 1.5-7.0 km, along the Matapí River, Amapá State, Brazil, were sampled monthly from April 2003 to November 2005 to determine relationships between seasonal abundance of host-seeking anophelines, rainfall and malaria cases. Out of the 759 821 adult female anophelines collected, Anopheles darlingi Root (Diptera: Culicidae) was the most abundant (56.2%) followed by An. marajoara Galvão & Damasceno (24.6%), An. nuneztovari Gabaldón (12.4%), An. intermedius (Chagas) (4.4%) and An. triannulatus (Neiva and Pinto) (2.3%). Vector abundance, as measured by human landing catches, fluctuated during the course of the study and varied in species-specific ways with seasonal patterns of rainfall. Anopheles darlingi and An. triannulatus were more abundant during the wet-dry transition period in June to August, whereas An. marajoara began to increase in abundance in February in two villages, and during the wet-dry transition in the other village. Anopheles nuneztovari and An. intermedius increased in abundance shortly after the rains began in January to February. A generalized linear mixed model (GLMM) analysis of 32 consecutive months of collections showed significant differences in abundance for each species by village and date (P < 0.0001). Correlations between lagged rainfall and abundances also differed among species. A strong positive correlation of An. darlingi abundance with rainfall lagged by 4 and 5 months (Pearson's r = 0.472-0.676) was consistent among villages and suggests that rainfall may predict vector abundance. Significant correlations were detected between numbers of malaria cases and abundances of suspected vector species. The present study shows how long-term field research may connect entomological and climatological correlates with malaria incidence.

Ecoregional classification of malaria vectors in the neotropics.

An ecoregional approach to the classification of malaria in the neotropics region can give health personnel a new prespective on how to manage malaria control programs. We propose an ecoregional classification based on vector distribution and important environmental determinants, including vegetation type, rainfall patterns, mean temperatures, elevation, and geomorphology. The following 5 ecoregions are described: (1) coastal, (2) piedmont, (3) savanna, (4) interior lowland forest, and (5) high valley. Subregional differences are classified when appropriate. Because human activities and extensive changes in land use usually leads to increased human-vector contact and alter local vector distribution and abundance, it is important that these changes be considered in the classification of vector ecoregions. Using this approach, risk areas can be classified as to the presence and potential abundance of particular vectors. Then, in combination with other components of malaria transmission (e.g., migration, cultural practices, living conditions), areas for surveillance and intervention can be prioritized. It is hoped that this forum will be a catalyst for discussion, future research, and the development of ecologically orientated malaria control programs.

Management of lone star ticks (Acari: Ixodidae) in recreational areas with acaricide applications, vegetative management, and exclusion of white-tailed deer.

A project on management of lone star ticks, Amblyomma americanum (L.), at Land Between the Lakes, a Tennessee Valley Authority recreational area in Kentucky-Tennessee, during 1984-1988, demonstrated the effectiveness and economics of three control technologies. Acaricide applications (chlorpyrifos at 0.28 kg [AI]/ha), vegetative management (mowing and removal of 40% overstory and 90-100% of midstory, understory, and leaf litter), and host management (white-tailed deer exclusion from a 71-ha campground with a single-line fence) provided 75, 70, and 64% mean controls of all life stages of the lone star tick, respectively. Combinations of acaricide applications + vegetative management, acaricide applications + host management, and acaricide applications + vegetative management + host management produced 94, 89, and 96% mean control of all life stages, respectively. The costs of acaricide applications (two per year), vegetative management (two mowings per year), and white-tailed deer exclusion (single-line fence) were $45, $150, and $30/ha/yr, respectively. Results of this project are used to design management strategies that could be considered for use against lone star ticks in recreational areas.

Malaria in Sucre State, Venezuela.

The author reviews the malaria research program in Sucre State, Venezuela, taking an ecosystem approach. The goal was to determine which methods could have been introduced at the onset that would have made the study more ecological and interdisciplinary. Neither an ecosystem approach nor integrated disease control were in place at the time of the study. This study began to introduce an ecosystem approach when two contrasting ecosystems in Sucre State were selected for study and vector control methods were implemented based on research results. The need to have a health policy in place with an eco-health approach is crucial to the success of research and control. The review suggests that sustainability is low when not all the stakeholders are involved in the design and implementation of the research and control strategy development. The lack of community involvement makes sustainability doubtful. The author concludes that there were two interdependent challenges for malaria control: development of an ecosystem approach for malaria research and control, and the implementation of an integrated disease control strategy, with malaria as one of the important health issues.

Wetlands and infectious diseases.

There is a historical association between wetlands and infectious disease that has led to the modification of wetlands to prevent disease. At the same time there has been the development of water resources projects that increase the risk of disease. The demand for more water development projects and the increased pressure to make natural wetlands economically beneficial creates the need for an ecological approach to wetland management and health assessment. The environmental and health interactions are many. There is a need to take into account the landscape, spatial boundaries, and cross-boundary interactions in water development projects as well as alternative methods to provide water for human needs. The research challenges that need to be addressed are discussed.

Ecology of malaria vectors in the Americas and future direction.

The resurgence of malaria in the Americas has renewed interest in Anopheles biology. Anopheles darlingi, An. albimanus, An. nuneztovai and An. aquasalis are reconfirmed as major malaria vectors and other species are playing important roles in regional malaria transmission. Adult biting activity and larval ecology are discussed in detail. Seasonal abundance and daily biting activity of Anophelines vary considerably among species and geographically for the same species. Anopheles albimanus has the least amount of variation in biting activity over its range and An. darlingi has the greatest. All species studied are more exophilic and exophagic than endophilic and endophagic. Anopheles darlingi is more anthropophilic, endophilic and endophagic than other Anophelines. Larval studies remain more descriptive than comprehensive. Research on Anophelines is becoming more integrated and biologists are using new biochemical techniques and ecological principles to answer critical questions. This "pluralization" will help us understand species complexes, population dynamics and malaria transmission. Integrated control programs will require more regional, in-depth ecological studies.

Use of Taylor's Power Law in examining the spatial distribution of free-living Boophilus microplus (Acari: Ixodidae) larvae in pastures in Puerto Rico.

Taylor's power law (y = amb) was used to analyze the spatial pattern of Boophilus microplus (Canestrini) larvae in tropical pastures. The index of aggregation b was 2.75 and showed that larvae were highly aggregated. The b-values differed significantly among certain pastures (LSD, P less than 0.05), and pasture type and use could have contributed to differences in b. The use of Taylor's power law to adjust for sampling inconsistencies that occur in tropical pastures where regimented sampling cannot always be followed is discussed.

Use of insecticide-impregnated mosquito nets and other impregnated materials for malaria control in the Americas.

This article reviews the current status of the use of insecticide-impregnated mosquito nets and other impregnated materials in the Americas. Studies from Brazil, Colombia, Ecuador, Guatemala, Peru, Suriname, and Venezuela are examined. It is concluded that most studies have suffered from experimental design errors, short duration problems, and/or inadequate measurement of health indicators. The review brings out the great difficulty of conducting scientific studies that attempt to measure the impact of insecticide-treated materials on malaria incidence. In particular, the low incidence of malaria in the Americas, the high prevalences of P. vivax and relapsing cases, and the relationship between human activity patterns and the crepuscular biting patterns of certain malaria vectors stand in the way of easy experimental design and execution. The utilization of impregnated mosquito nets or other impregnated materials as a major component of an integrated malaria control program would be premature at this time. However, it is recommended that well-conceived large-scale trials and interventions be considered when they are based on a thorough understanding of the dynamics of malaria transmission in the area of study.