Chemical Vector Control Research Articles

Insecticidal properties of essential oils from Lippia turbinata and Lippia polystachya (Verbenaceae) against Culex quinquefasciatus (Diptera: Culicidae)

Mosquitoes are important vectors of diseases to humans and domestic animals. Chemical control of vectors remains a main resource for the prevention and control of vector-borne diseases. Due to the development of insecticide resistance and risks to human health and the environment of synthetic compounds, the search for alternative pesticides is encouraged. This work assessed the insecticidal activity of essential oils (EOs) from Lippia turbinata and L. polystachya from Argentina on Culex quinquefasciatus mosquitoes. EOs were extracted by hydro-distillation and analyzed with gas-liquid chromatography and mass spectrometry. The insecticidal activity against mosquito larvae, pupae, and adults were evaluated according to World Health Organization protocols. Concentrations ranking from 10 to 160 ppm were assessed at 1, 2, 3, and 24 h posttreatment. The composition of the EO of L. polystachya and L. turbinata were qualitatively similar, with alpha-thujone and carvone as main constituent; differences were mostly due to the proportion of each component. beta-caryophyllene was also an important constituent of the EO of L. turbinata. Both EO were larvicidal at concentrations of 80 ppm or higher, but only L. turbinata was adulticidal. No pupal mortality was detected. The potential of these EOs for vector control is discussed.

Comparative genomics of insect juvenile hormone biosynthesis

The biosynthesis of insect juvenile hormone (JH) and its neuroendocrine control are attractive targets for chemical control of insect pests and vectors of disease. To facilitate the molecular study of JH biosynthesis, we analyzed ESTs from the glands producing JH, the corpora allata (CA) in the cockroach Diploptera punctata, an insect long used as a physiological model species and compared them with ESTs from the CA of the mosquitoes Aedes aegypti and Anopheles albimanus. The predicted genes were analyzed according to their probable functions with the Gene Ontology classification, and compared to Drosophila and Anopheles gambiae genes. A large number of reciprocal matches in the cDNA libraries of cockroach and mosquito CA were found. These matches defined known and suspected enzymes of the JH biosynthetic pathway, but also several proteins associated with signal transduction that might play a role in the modulation of JH synthesis by neuropeptides. The identification in both cockroach and mosquito CA of homologs of the small ligand binding proteins from insects, Takeout/JH binding protein and retinol-binding protein highlights a hitherto unsuspected complexity of metabolite trafficking, perhaps JH precursor trafficking, in these endocrine glands. Furthermore, many reciprocal matches for genes of unknown function may provide a fertile ground for an in-depth study of allatal-specific cell physiology.

Dengue and dengue hemorrhagic fever epidemics in Brazil: what research is needed based on trends, surveillance, and control experiences?

Dengue epidemics account annually for several million cases and deaths worldwide. The high endemic level of dengue fever and its hemorrhagic form correlates to extensive domiciliary infestation by Aedes aegypti and multiple viral serotype human infection. This study analyzed serial case reports registered in Brazil since 1981, describing incidence evolutionary patterns and spatial distribution. Epidemic waves followed the introduction of every serotype (DEN 1 to 3), and reduction in susceptible individuals possibly accounted for decreasing case frequency. An incremental expansion of affected areas and increasing occurrence of dengue fever and its hemorrhagic form with high case fatality were noted in recent years. In contrast, efforts based solely on chemical vector control have been insufficient. Moreover, some evidence demonstrates that educational measures do not permanently modify population habits. Thus, as long as a vaccine is not available, further dengue control depends on potential results from basic interdisciplinary research and intervention evaluation studies, integrating environmental changes, community participation and education, epidemiological and virological surveillance, and strategic technological innovations aimed to stop transmission.

Biology of Disease Vectors, 2nd ed.

This edition is a massive, 7-section, 57-chapter medical entomology reference text. The chapters are written by 72 experts from around the world and provide an understanding of disease vectors on a broad front, including biologic requirements of vectors, epidemiology, molecular biology, genetics, principles of control, and insecticide resistance. The text consistently emphasizes molecular biologic approaches to these topics. This book begins by discussing the vectors themselves, with chapters on mites, ticks, true bugs, lice, fleas, mosquitoes, and various dipterans such as tsetse flies and sand flies. Line drawings and black-and-white pictures abound. The number of color photos is limited; those in the kissing bug/bed bug chapter and the flea chapter are especially beautiful. Subsequent sections delve into the physiologic and genetic basis of vector biology. The final 2 sections concern controlling insects and acarines and special (laboratory) methods associated with vectors. The last section, which deals with laboratory methods, is like a giant appendix in which updates are given for the care, maintenance, and experimental infection of various disease vectors, including notes on handling, housing, rearing facilities, containment, and safety issues. One of the most helpful chapters for this reviewer was the one entitled, Systematic Relationships among Disease Vectors, which defines molecular systematics terminology and explains how phylogenetic relationships among species are inferred from molecular data. I wish every traditional taxonomist and systematist would read this chapter. This book contains a few misspellings (e.g., the chapter title in the Table of Contents, Chapter 46), but no major errors. Its only weakness seems to be one of disunity. The title doesn't match the book's content, and the text is so comprehensive that it seems unfocused. There are chapters on chemical and genetic control of vectors, cell culture, and even research safeguards for transgenic mosquitoes. How these fit under the title biology of vectors was difficult to discern. Perhaps in future editions, the chief editor could split the book into several separate volumes, each with a more appropriate title. Nevertheless, this book is an indispensable reference and a wonderful treasure trove of information about medical entomology. Its only flaws are organizational, not factual. The chief editor, section editors, and authors are to be congratulated on this scholarly work.

Cucurbit biotechnology-the importance of virus resistance

The cucurbit family includes a number of valuable crop species (melon, cucumber, squash/pumpkin, watermelon). Much of this review is concerned with transgenic resistance to viruses, shown to be the major application of biotechnology in the cucurbit family. Progress made with the production of transgenic cucurbit crops is discussed. Published data on field tests of transgenic cucurbits are reviewed, showing that much progress has been made with multiple virus-resistant cucurbit crops which can be productive without chemical control of insect virus vectors. Modes of virus resistance in trangenic cucurbits are discussed, as is the bio-safety of such crops. For the first time a detailed analysis has been made of world-wide and US field test applications for cucurbit crops. World-wide, most field test applications were for melon (54%), followed by squash (32%). World-wide most field test applications were for virus resistance (84%), and most applications (77%) were in the USA. Two transgenic multiple virus-resistant squash crops have been deregulated (released for sale). Additionally, the analysis shows that there are transgenic multiple virus-resistant crops in all major cucurbit species already available, for which several different companies have applied for field tests. This would imply that such crops are ready to be marketed should conditions permit, which would have an impact world-wide in reduction of ecological damage due to chemical control of the insect viral vectors.

A experiência do município de Paraty (Rio de Janeiro, Brasil) na prevenção e controle da leishmaniose tegumentar americana

American tegumentary leishmaniosis (ATL) is an important zoonosis in Rio de Janeiro State, Brazil, and it represents an increasing public health problem. The municipality of Paraty is an endemic area, where 76 human cases were reported in 2002. In June of 2002 the Municipal Health Department had started an ATL control program, according with methodologies recommended by National Health Foundation (FUNASA) on the ATL Control Manual of 2000. The control strategies were based on capture of sandflies in Atlantic Forest areas and identification of vectors species, chemical control of vectors through periodic domiciliary and peridomiciliary insecticide application, serological investigation of suspect dogs and elimination of infected dogs, rodents control, investigation of new possible cases and educational measures to the local community. This paper presents the municipality of Paraty experience on implanting a control program of ATL and its efficiency. After the adoption of these measures, it had occurred 52 new cases in 2003. This result indicates that there was a decrease of 31,6%, in relation to the cases reported on 2002.

Effects of Chemical Control of Aphid Vectors and of Cross-Protection on Increase and Spread of Citrus tristeza virus

Author(s): Gottwald, T. R.; Abreu-Rodriguez, E.; Yokomi, R. K.; Stansly, P. A.; Riley, T. K.

Controlling Vectors and Hosts of Parasitic Diseases Using Fishes

Current estimates of the global prevalence of parasitic diseases range from 600 million cases caused by protozoan and metazoan parasites (Kolberg 1994) to more than 1 billion total cases (Goodman 1994). Strategies for reducing the transmission of these diseases include: immunization programs; reduction of parasite loads in human populations via chemotherapy; modification of cultural practices through public health education, clean water, and sanitation projects; habitat modification (e.g., drainage of stagnant water bodies); and biological and chemical vector and host control (Warren and Mahmoud 1990, WHO 1990). Due Much of the published research on the use of

The chemical control of vectors of leishmaniasis.

The chemical control of vectors of leishmaniasis.

Ecological aspects of the vectorial control of Chagas' disease in Brazil.

The feasibility and most important ecological aspects of vectorial Chagas' disease control are discussed. The spread and maintenance of this disease involve multiple ecological and sociopolitical factors that must be taken into account when control programs are planned, executed and evaluated. In spite of its complexity, Chagas disease can be controlled using methods that target specific mechanisms of transmission, the most important being vectorial and transfusional. Major ecological problems in Chagas' disease control do not exist, even in the case of the chemical control of triatomine vectors. The main challenges for the Brazilian Control Program at this moment are: its maintenance as a political priority; the threat of peridomestic vectors; and the consolidation of permanent horizontal and participative epidemiological surveillance systems against the vector.

Animal indicators for side-effects of chemical vector control

In many places in the tropics pesticides are applied in the natural environment to control insects either for crop protection, or for human health. The present study concerns the side-effects of insecticides that are applied in West Africa against tsetseflies (Glossina spp), which are the vectors of human and animal sleeping sickness. Pyrethroids and endosulfan were sprayed either by helicopter or by ground spraying on riverine forests and on forests around villages.Because of the complexity of the terrestrial and aquatic ecosystems under study, a selection was made of populations in which side-effects were assessed (so-called indicators). Fish and benthic arthropods were studied in the rivers; Diptera, Hymenoptera and spiders in the forest. Observations on short-term effects revealed the most vulnerable populations (indicators for effects) depending on the insecticide and the method of application. Long-term studies, up to two years, revealed the differences amongst these populations in ability to recover from local depletion. The populations which recovered most slowly were regarded as indicators for recovery.Differences in hydrological regime between climatic zones are regarded to be highly related to differences in vulnerability of ecosystems to irreversible damage by pesticides.