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PubMed1998

Pantropic retroviral vectors mediate somatic cell transformation and expression of foreign genes in dipteran insects.

The control of insects that transmit disease and damage crops has become increasingly difficult. The ability to genetically engineer insects would facilitate strategies to protect crops and block arthropod vector-borne disease transmission. Transformation vectors based on insect transposable elements have been developed, but most have limited host ranges. A promising alternative is the pantropic retroviral vector, which is packaged with the envelope glycoprotein from vesicular stomatitis virus and is replication-defective. We show here that pantropic murine retroviral vectors can mediate high-level expression of foreign genes in somatically transformed insect larvae and adults of three dipteran genera. This success demonstrates the potential for germline transformation mediated by pantropic retroviral vectors.

Aedes↗
PubMed1995

Post-inoculation changes in enzyme activity of Aedes aegypti infected with Chikungunya virus.

Levels of acetylcholinesterase, non-specific esterases, glutathione-S-transferase and glucose-6-phosphate dehydrogenase in Aedes aegypti (L.) mosquitoes inoculated intrathoracally with Chikungunya virus were elevated, as compared to uninoculated control insects. A number of these enzymes are important in the insects defence mechanism against xenobiotics, such as pesticides. Malathion bioassays indicated a reduction in the susceptibility of experimentally injected insects with virus or virus-free inoculum, compared to non-inoculated controls. However, insects which were mock-inoculated (injected with no inoculum) showed a similar reduction in susceptibility suggesting that the observed effect was due to the mobilization of a defence reaction in the mosquitoes in response to injury during inoculation.

Acetylcholinesterase↗
PubMedDate not supplied

[Current epidemiological malaria situation in Kyrgyzstan (1995-1999)].

Kyzgyzstan is situated in an area which is potentially at risk for malaria. In 1995-1999, 58 cases of malaria were recorded, six of them were local cases. The factors that promote the spread of malaria in Kyrgyzstan are the widespread and constant migration of people from Tajikistan and close economic ties between Kyrgyzstan and a number of Asian countries with widespread malaria epidemics. Most cases of malaria in Kyrgyzstan were imported from Tajikistan (39 cases or 75% of all imported cases). Plasmodium vivax, P. falciparum and P. malariae were identified in 95.9, 1.7, and 2.1%, respectively. There is a widespread irrigation network in the country, along with a large number of reservoirs, ponds, lakes, springs, streams, gullies, and marshy floodplains. As of 1 January 2000, there are 2833 water areas that can support Anopheles mosquitoes, with a total area of 5008.5 ha. The total length of the sewerage and drainage system is 5,440 km. There is a great potential for the spread of malaria in the south of the republic, i.e. the Osh and Zhalalabad Regions, especially due to a large number of state rice (paddy) fields covering an area of over 3,500 ha. Small rice-growing plots close to private dwellings, which are cultivated without any mosquito control measures, currently provide further breeding grounds for mosquitoes. Almost 80% of the population of these areas is at risk for malaria. Almost all species of malaria mosquitoes have been identified in Kyrgyzstan. An. claviger and An. messeae have too, two other species have also spread through the country, these are An. martinius and An. superpictus which became the main vectors of malaria epidemics in the south in the 1930s-1950s. Large-scale development of the pre-imago stages of the mosquito (a larval, water-based stage) takes place 5-7 months within which 4-6 mosquito generations develop. At present, there is a shortage of staff in Kyrgyzstan, especially at a local level, who has thorough knowledge of malaria and experience with its control and who can define the highest priorities and the most appropriate and effective within the Global Malaria Control Strategy at the current stage. Laboratory services are in need of considerable support: stocks of essential supplies for laboratory tests are almost exhausted, there is a shortage of essential equipment, the staff is not well enough trained. There is an acute shortage of insecticides and larvicides for mosquito control. Entomologists have no sufficient insect control equipment to treat water areas (e.g. sprayers), there is no equipment for monitoring water areas or introducing larvicidal fishlaria (Gambusiae) either, and local monitoring is hampered by shortages of vehicles, fuel, and lubricants. Since malaria control is an urgent problem, Kyrgyzstan has developed a comprehensive and integrated malaria programme for 2000-2004 and a plan of actions to study malaria vector resistance to insecticides in the Republic of Kyrgyzstan in 2000.

Humans↗
PubMed1978

[Test of O,O-dimethyl(1-hydroxy-2,2,2-trichloroethyl)phosphonate (Trichlorfon) for carcinogenic acitivity in rats by oral (oesphageal-gastric intubation) and intraperitoneal application (author's transl)].

O,O-Dimethyl (1-hydroxy-2,2,2-trichloroethyl)phosphonate (Trichlorfon) is produced at a large scale and used in many countries e. g. in agriculture and housholds to control insects and on animals to control parasties. The compound (dissolved in isotonic sodium chloride solution) was tested for carcinogenic activity in albino rats by oral (oesophageal-gastric intubation) and intraperitoneal administration. The period of treatment was 90 weeks. The experiment was terminated at 118 weeks. There was no statistically significant difference when the tumor incidence in the groups of treated and control animals was compared. No carcinogenic activity of the compound could be demonstrated in rats at either route of application.

Administration, Oral↗
PubMed1996

Vector insects and their control.

This paper emphasizes the huge influence that vector-transmitted disease has on humans using plague, epidemic typhus and nagana as examples. The continuing need for vector control in campaigns against insect-transmitted disease is shown by reference to current control programmes mounted against Chagas' disease, onchocerciasis, lymphatic filariasis and nagana. These successful campaigns have not been reliant on new breakthroughs but on the forging of available tools into effective strategies widely and efficiently used by the control authorities, and the long-lasting political commitment to the success of the schemes in question. A brief mention is made of current fashions in vector control research and that great care needs to be taken by policy-makers to achieve a balance between long-term research aiming at the production of fundamentally new control technologies and operational research aiming to forge the often highly effective tools we already have into sound control strategies.

Animals↗
PubMed1994

Inhibition of cuticular lipid synthesis and its effect on insect survival.

A new approach to insect control--using sodium trichloroacetate (NaTCA) to inhibit synthesis of the hydrophobic cuticular lipids that protect insects from dehydration--was tested on Triatoma infestans. In vivo and in vitro studies of incorporation of radioactive precursors showed diminished cuticular hydrocarbon synthesis after NaTCA treatment. Thin layer chromatography and scanning electron microscopy showed disruption of the cuticular lipid layer of NaTCA-treated insects, which also have increased mortality and altered molting cycles. NaTCA treatment enhanced the penetration and increased the lethality of a contact insecticide.

Animals↗
PubMed2006

Insects as chemosensors of humans and crops.

Insects transmit disease to hundreds of millions of people a year, and cause enormous losses to the world's agricultural output. Many insects find the human or plant hosts on which they feed, and identify and locate their mates, primarily through olfaction and taste. Major advances have recently been made in understanding insect chemosensation at the molecular and cellular levels. These advances have provided new opportunities to control insects that cause massive damage to health and agriculture across the world.

Animals↗
PubMed2003

[Occurrence of insect pests in hospitals in Poland].

The prevalent synantropic species present in hospitals in Poland was the German cockroach (Blattella germanica L.), found in about 70% hospitals. It was followed by Oriental cockroach (Blatta orientais L.) and Pharaoh's ant (Monomorium pharaonis L.) occurred in 40% and 17% of hospitals respectively. Kitchens, laundries and lavatories were the most often infested places. Preliminary investigation of German cockroaches caught in hospitals in Poland showed on their body surfaces presence of bacteria known as these causing nosocomial infection. Several strains were resistant to antibacterial drugs widely used for treatment and showed insensitivity to chemical disinfectants used for surface treatment. Additional risk elements in Poland could be high resistance levels to many insecticides used for insect control in hospitals.

Animals↗
PubMed2005

Quality of transgenic laboratory strains of Cochliomyia hominivorax (Diptera: Calliphoridae).

Genetically modified, mass reared insects present novel possibilities for the future of insect control. One concern about manipulation of insects is a possible loss of strain quality due to the introduction of a foreign gene of any sort into the insect genome. Eight transgenic strains of screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), were compared with the wild-type parental laboratory strain in laboratory culture. Measurements of average fertility, fecundity, larval productivity, and longevity were analyzed. Two transgenic strains had significantly lower larval productivity than controls, one of which was explained by a homozygous lethal insertion of the transgene. Another strain produced significantly fewer eggs than controls. Overall strain characteristics, including measurements from egg, larva, pupa, and adult stages, were compared. Transgenic colonies did not consistently show significantly lower individual or aggregate strain quality characteristics than the control parental colony; hence, the presence of the transgene used to produce the strains tested did not incur a discrete cost to the colonies of laboratory-reared C. hominivorax.

Animals↗
PubMed2003

Managing the pepper maggot (Diptera: Tephritidae) using perimeter trap cropping.

A perimeter trap crop barrier of hot cherry peppers, border-row insecticide applications, and a combination of the two management strategies were evaluated to see if they could protect a centrally located main crop of bell peppers from oviposition and infestation by the pepper maggot, Zonosemata electa (Say). In large plots, the main cash crop of bell peppers was protected from the majority of the oviposition and infestation by all three barriers. The combination sprayed/trap crop barrier provided the best protection against both oviposition and infestation and resulted in over 98% pest-free fruit at harvest. Maggots infested only 1.7% of the main crop fruit when protected by a sprayed or unsprayed trap crop barrier, compared with 15.4% in control plots. The perimeter sprayed/trap crop strategy was employed in three commercial fields in 2000 and 2001. The combination barrier resulted in superior insect control and reduced insecticide use at all commercial locations, compared with the same farms' past history or to farms using conventional and integrated pest management (IPM) methods. Economic analysis showed that the technique is more cost effective and profitable than relying on whole-field insecticide applications to control the pepper maggot. Farmer users were surveyed and found the perimeter trap crop technique simple to use, with many hard-to-measure benefits associated with worker protection issues, marketing, personnel/management relations, pest control and the environment. Use of the perimeter trap crop technique as part of an IPM or organic program can help improve crop quality and overall farm profitability, while reducing pesticide use and the possibility of secondary pest outbreaks.

Agriculture↗
PubMed2006

A purified Bacillus thuringiensis crystal protein with therapeutic activity against the hookworm parasite Ancylostoma ceylanicum.

Crystal (Cry) proteins produced by the soil bacterium Bacillus thuringiensis (Bt) are harmless to vertebrates, but they are highly toxic to insects and nematodes. Their value in controlling insects that destroy crops and transmit human diseases is well established. Although it has recently been demonstrated that a few individual Bt Cry proteins, such as Cry5B, are toxic to a wide range of free-living nematodes, the potential activity of purified Cry proteins against parasitic nematodes remains largely unknown. We report here studies aimed at characterizing in vitro and in vivo anthelminthic activities of purified recombinant Cry5B against the hookworm parasite Ancylostoma ceylanicum, a bloodfeeding gastrointestinal nematode for which humans are permissive hosts. By using in vitro larval development assays, Cry5B was found to be highly toxic to early stage hookworm larvae. Exposure of adult A. ceylanicum to Cry5B was also associated with significant toxicity, including a substantial reduction in egg excretion by adult female worms. To demonstrate therapeutic efficacy in vivo, hamsters infected with A. ceylanicum were treated with three daily oral doses of purified Cry5B, the benzimidazole anthelminthic mebendazole, or buffer. Compared with control (buffer-treated) animals, infected hamsters that received Cry5B showed statistically significant improvements in growth and blood hemoglobin levels as well as reduced worm burdens that were comparable to the mebendazole-treated animals. These data demonstrate that Cry5B is highly active in vitro and in vivo against a globally significant nematode parasite and that Cry5B warrants further clinical development for human and veterinary use.

Ancylostoma↗
PubMed2004

Enzyme inhibitors in biorational approaches for pest control.

Conventional insecticides of broad spectrum have been widely used as the main tools for controlling insect pests. However, as the consequence of their toxicity and deep environmental impact, new biorational, and more specific approaches have been developed. In this review we present an overview of those pest control approaches which have resulted from studies dealing with inhibition of the enzymes involved in the physiology, growth, molting, development and reproduction of insect pests. These approaches involve synthetic compounds from laboratory studies and natural chemicals present in the crop plants. Recent developments using inhibitors expressed in transgenic plants are also outlined.

Animals↗
PubMed2001

Recent advances in the chemistry of spinosyns.

The spinosyns are a new class of fermentation-derived insect control agents that are effective against a variety of chewing insect pests. The successful introduction of spinosad into the agricultural marketplace represents an important milestone in the use of natural products for commercial pest control. The development of a natural product presents additional limitations relative to a synthetic material. While the latter affords some degree of control in building appropriate physical attributes such as photostability, a natural product, designed to function in a different environment, is often less suited for traditional spray applications. Despite its intrinsic photolability, spinosad is stable enough to perform under field conditions. In an effort to generate analogs with improved physical characteristics, we have developed a variety of conditions for selectively modifying different portions of the molecule, and we have discovered analogs with greater activity against a broader spectrum of pests. The inability to translate improved greenhouse activity to actual field conditions resulted in a detailed study of the effects of formulations and crystallinity on biological activity. Through this effort, measurably improved field performance of synthetic spinosyn analogs relative to the natural product have now been observed.

Animals↗
PubMed2003

Juvenile hormone titre and egg production in Tenebrio molitor infected by Hymenolepis diminuta: effect of male and/or female infection, male age and mating.

Infection of Tenebrio molitor with Hymenolepis diminuta induces curtailment of female fertility. We examined ovulation and oviposition, and associated titres of juvenile hormone (JH), in relation to parasitism and mating. Oviposition was significantly increased in infected mated and virgin beetles by days 6 and 9 post-emergence. Ovulation was not changed by infection; by the end of the 18-day experiment, the total number of laid eggs was not significantly altered. On day 6, JH levels were significantly higher in virgin infected insects, compared to non-infected controls (236+/-37.7 and 107+/-9.62 pg/g wet weight). Oviposition increased after mating, but total eggs ovulated remained the same. JH levels were higher in mated females on days 12 and 18 post-emergence, for infected and control insects. Previous studies suggested that male reproductive potential might rise following infection, because uninfected females lay more eggs when mated to infected males. We tested whether this caused an increase in female JH. Males were mated on days 5 or 12, when significant changes in their reproductive physiology begin to be observed, and are maximal, respectively. However, male age was of greater significance in promoting JH levels in females (p=0.001), than infection status of either partner (p=0.33).

Age Factors↗
PubMed2002

Plant toxic proteins with insecticidal properties. A review on their potentialities as bioinsecticides.

To meet the demands for food of the expanding world population, there is need of new ways for protecting plant crops against predators and pathogens while avoiding the use of environmentally aggressive chemicals. A milestone in this field was the introduction into crop plants of genes expressing Bacillus thuringiensis entomotoxic proteins. In spite of the success of this new technology, however, there are difficulties for acceptance of these 'anti-natural' products by the consumers and some concerns about its biosafety in mammals. An alternative could be exploring the plant's own defense mechanisms, by manipulating the expression of their endogenous defense proteins, or introducing an insect control gene derived from another plant. This review deals with the biochemical features and mechanisms of actions of plant proteins supposedly involved in defense mechanisms against insects, including lectins, ribosome-inactivating proteins, enzymes inhibitors, arcelins, chitinases, ureases, and modified storage proteins. The potentialities of genetic engineering of plants with increased resistance to insect predation relying on the repertoire of genes found in plants are also discussed. Several different genes encoding plant entomotoxic proteins have been introduced into crop genomes and many of these insect resistant plants are now being tested in field conditions or awaiting commercialization.

Amino Acid Sequence↗
PubMed1958

A summary of recent insecticidal tests on some insects of medical importance in Taiwan.

The author describes some investigations carried out on a number of insects of medical importance in Taiwan (six species of Anopheles, one species of Culex, one of Aëdes, two subspecies of Musca domestica and one species of Cimex) with the object of finding out whether resistance to DDT and BHC had developed among them as a result of the insect-control campaigns which have been in operation in the island since 1948.Of the anophelines, certain strains of A. minimus and A. h. sinensis were found to have a relatively high and statistically significant tolerance to DDT, but whether this can be regarded as developed resistance remains to be ascertained. As to the other insects examined, some strains exhibited statistically significant differences in tolerance to DDT; in certain cases, however, the ancestors of the tolerant strains had never been exposed to DDT, and it has not been possible yet to find an explanation for this phenomenon.No significant difference in susceptibility to gamma-BHC was shown by three strains of Cimex hemipterus, two of which had previously been exposed to mixtures of DDT and BHC and one of which had not.

Aedes↗