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PubMed2005

Evolution of resistance toward Bacillus sphaericus or a mixture of B. sphaericus+Cyt1A from Bacillus thuringiensis, in the mosquito, Culex quinquefasciatus (Diptera: Culicidae).

The 2362 strain of Bacillus sphaericus (Bs) Neide is a highly mosquitocidal bacterium used in commercial bacterial larvicides primarily to control mosquitoes of the genus Culex. Unfortunately, Bs is at high risk for selecting resistance in mosquito populations, because its binary toxin apparently only binds to a single receptor type on midgut microvilli. A potential key strategy for delaying resistance to insecticidal proteins is to use mixtures of toxins that act at different targets within the insect, especially mixtures that interact synergistically. We tested this hypothesis for delaying the phenotypic expression of resistance by exposing Culex quinquefasciatus Say larvae to Bs alone or in combination with Cyt1A from Bacillus thuringiensis subsp. israelensis. Two laboratory lines of Cx. quinquefasciatus, one sensitive to Bs and the other containing Bs resistance alleles, were subjected to intensive selection pressure for 20 generations with either Bs 2362 or a 3:1 mixture of Bs 2362+Cyt1A. At the end of the study, the sensitive line had evolved >1000-fold resistance when selected with Bs alone, whereas the parallel line selected with Bs+Cyt1A exhibited only low resistance toward this mixture (RR95, 1.4). Similar results were observed in the lines containing Bs resistance alleles. Both lines selected with Bs+Cyt1A exhibited substantial resistance to Bs in the absence of Cyt1A. Although selection with Bs+Cyt1A did not prevent the underlying evolution of resistance to Bs, these results suggest that a mixture of Bs with other endotoxins, particularly one like Bs+Cyt1A in which the components interact synergistically, will provide longer lasting and more effective mosquito control than Bs alone.

Animals↗
PubMed1991

A program for prevention and control of epidemic dengue and dengue hemorrhagic fever in Puerto Rico and the U.S. Virgin Islands.

The ongoing resurgence of Aedes aegypti in the Americas--abetted by poor mosquito control, urbanization, and increased air travel--has led to dengue hyperendemicity, more frequent dengue epidemics, and the emergence of dengue hemorrhagic fever (DHF). This article describes a program developed to cope with this situation that emphasizes disease prevention rather than general mosquito control measures.

Aedes↗
PubMed1991

Evaluation of a microgel droplet formulation of Bacillus sphaericus 1593 M (Biocide-S) for control of mosquito larvae in rice fields in southern India.

A new microgel droplet formulation of Bacillus sphaericus 1593 M (Biocide-S) was tested at 2 rates against culicine vectors of Japanese encephalitis and Anopheles subpictus. A single application just after transplantation of rice seedlings prevented the buildup of anopheline as well as culicine populations, and gave 83-100% reduction of pupal density at the lower rate (2.2 kg/ha) and 87-100% reduction at the higher dosage (4.3 kg/ha) for at least 5 weeks. During the last 3 wk before harvest, density was naturally very low and the efficacy of the treatment could not be assessed. This formulation has a potential for control of riceland mosquitoes, but a suitable delivery system is required before it can be considered for practical control.

Agriculture↗
PubMed1962

Control of bancroftian filariasis in the Pacific.

Although the etiological agent and the vector of filariasis were recognized early in the history of tropical medicine, control programmes were slow in developing, mainly because efficient filaricides were not known. Following the discovery of diethylcarbamazine, however, control projects were inaugurated in many parts of the world, including a number among island populations of the Pacific, in ideal conditions for observation and assessment.This paper reviews the answers to questionnaires sent to twelve areas in the Pacific where control projects have been undertaken. The most rapid and effective results appear to have been obtained in the Society Islands and Niue and Atiue, where mass treatment of the whole population with diethylcarbamazine was employed simultaneously with mosquito control. The authors conclude from the answers received that most control projects support the combined use of diethylcarbamazine and mosquito control, and that, where a control programme has brought the microfilaraemia rate down to 5% or less, the launching of an eradication programme should be considered.

Diethylcarbamazine↗
PubMed1988

Efficacy and longevity of Bacillus sphaericus 2362 formulations for control of mosquito larvae in dairy wastewater lagoons.

Bacillus sphaericus strain 2362 was evaluated for the control of Culex larvae in dairy wastewater lagoons. Both initial and long-term efficacy were studied. Two primary powder preparations of ABG-6184 yielded mediocre and short-term control at the rates of 0.25 and 0.5 lb/acre (0.26 and 0.56 kg/ha), while level of control and persistence greatly increased as the dosages were increased to 1.0, 2.0 and 4.0 lb/acre (1.12, 2.24 and 4.48 kg/ha). The 1.0 and 2.0 lb/acre rates yielded almost 100% control for 4 weeks and the 4.0 lb/acre rate yielded control (99%) for 49 days or longer. A flowable concentrate preparation (BSP-2) yielded complete initial and persistent control of larvae for 14-21 days at 2.0, 4.0 and 5.0 lb/acre (2.24, 4.49 and 5.6 kg/ha). Granular formulations of B. sphaericus 2362 (ABG-6185) were also evaluated at 2.5, 5.0, 7.5, 10.0 and 20.0 lb/acre (2.8, 5.6, 8.4, 11.2 and 22.4 kg/ha) of the granules. Some of the formulations were more active than the others, yielding excellent initial and persistent control (80% +) for 14-21 days with one treatment.

Animals↗
PubMed1995

The future of microbial insecticides as vector control agents.

Insect vectors of human diseases are subject to diseases of their own caused by viruses, bacteria, fungi, protozoans, and nematodes. Over the past 30 years, many members of these groups have been evaluated as vector control agents, particularly for mosquito control. Most pathogens and nematodes occur primarily in larvae, and are only effective against this stage. The principal candidate control agents studied include iridescent and nuclear polyhedrosis viruses, the bacteria Bacillus thuringiensis and Bacillus sphaericus, the fungi Lagenidium giganteum, Culicinomyces clavosporus, and species of the genus Coelomomyces, the protozoan Nosema algerae, and the mermithid nematode Romanomermis culicivorax. Of these, the only one considered an operational success is the bacterium, Bacillus thuringiensis subsp. israelensis (B.t.i.), which has proven useful for control of both mosquito and blackfly larvae in programs where larviciding has been traditionally employed as a vector control tactic. The reasons for the success of B.t.i. are its cost-effectiveness and relative ease of use, which are due, respectively, to the ability of B.t.i. to be grown on artificial media and the development of formulations that can be applied using conventional insecticide application technology. Because few microbial insecticides are cost-effective, and those that are are only effective against larvae, these agents will likely play only a minor, but in some cases important, role in most future vector control programs.

Animals↗
PubMed2006

Effects of methoprene on oviposition by Aedes japonicus and Culex spp.

The mosquito larvicide methoprene is a juvenile growth hormone mimic that is widely used to control mosquitoes. This chemical disrupts normal mosquito development, drastically inhibiting emergence from the pupal to the adult stage. If the presence of methoprene attracts or deters mosquitoes from ovipositing it could have implications for mosquito control. This study evaluates whether methoprene attracts or deters mosquitoes likely to oviposit in catch basins. In a field experiment, methoprene formulated as liquid larvicide did not affect oviposition of either Culex spp. or Aedes japonicus in 19-1 plastic buckets.

Aedes↗
PubMed2003

Biosynthesis and control of mosquito gut proteases.

Earlier investigations of the proteases that digest the blood meal in mosquitoes identified the midgut epithelial cells as the source of the main blood digesting protease, trypsin. Surgical manipulations and cytoimmunochemical studies indicated that trypsin in the mosquito is not stored in the epithelial cells as an inactive enzyme, but is synthesized, activated and released into the gut lumen after the blood meal. Using molecular biology techniques the major trypsin genes have been sequenced and some information on the transcription factors that regulate the induction of the genes have been reported. Although all the hormone(s) and the factors that are responsible for the induction of trypsin biosynthesis are not known, the termination of trypsin biosynthesis is controlled by a decapeptide hormone; trypsin modulating oostatic factor (TMOF) that is secreted by the mosquito ovary. Genetic engineering and expression of TMOF in bacteria, yeast and algae is emerging as a potential future larval control of mosquitoes in the field.

Aedes↗
PubMed1991

Les maringouins du meche and the legacy of two men.

E. S. Hathaway and his colleague, A. B. Ritter, were directly responsible for establishing organized mosquito control in Louisiana in the late 1950s and early 1960s. They jointly sought to educate governmental officials and Louisiana citizens that mosquitoes could be controlled if the efforts were based on scientific knowledge, trained personnel and appropriate funding. These men were instrumental also in establishing the Louisiana Mosquito Control Association and subsequently involved with the formation of the first 5 parish-wide mosquito control districts in Louisiana.

History, 20th Century↗
PubMed1998

Failure-as-success: multiple meanings of eradication in the Rockefeller Foundation Sardinia project, 1946-1951.

In the history of malaria control programs there were important tensions between proponents of the concept of eradication and those of malaria control. In this debate the concept of eradication has had multiple meanings. This paper concerns the post-hoc interpretations of the outcomes of the Rockefeller International Health Foundation-sponsored project conducted in Sardinia between 1946 and 1951. The Ente Regionale per la Lotta Anti-Anofelica in Sardegna (regional agency for the anti-Anopheles struggle in Sardinia) (ERLAAS) project was conceived as a large-scale, field-based pilot demonstration project to test the feasibility of the strategy of "species eradication" in an area with an endemic malaria vector. Species eradication, a strategy championed by Soper, was aimed at the total annihilation of an anopheline vector from an area. Under the leadership of the Rockefeller Foundation, the ERLAAS project used postwar UNRRA funds to purchase local labor and imported DDT, oil-suspension, and war-surplus equipment in an "all-out" campaign against Anopheles labranchiae, even in sparsely populated areas. The original aim was entirely entomological; species eradication was expected to be completed in two years for a cost of $2.7 million. Ironically, malaria mortality on the island had already been lowered before WWII by a series of public health interventions. The ERLAAS project encountered severe technical and logistical difficulties; its ultimate failure was foreshadowed in the resignation of the first American director who doubted the feasibility of species eradication. Ultimately, the ERLAAS project was ended after four and a half years and an expenditure of $11.2 million. Although new malaria transmission on the island ended the project failed to eliminate A labranchiae. Finally, the regional government was counselled to continue mosquito control efforts; the continuation of a substantial mosquito control program for fifty years after this famous "malaria eradication" project runs contrary to the basic cost/benefit logic of the eradication concept. Nevertheless, in the popular press both in the U.S. and Italy, the project was presented and heralded as a major success in liberating the island from the age-old stranglehold and misery of malaria. In the course of the project, the goals of ERLAAS became transformed from species eradication to malaria eradication; this was an important political spin that was put on the evaluation of the program. The consequences of this tactical change in discourse included two important facts: the contribution of the Rockefeller Foundation to the island was exaggerated, and the legitimacy of the concept of global eradication was maintained. In the framework of the World Health Organization and the agreement for a global malaria eradication program, the "failure" of the Sardinia project was seldom recognized or mentioned. The technical, economic, and logistical problems faced by ERLAAS were very similar to the problems associated with the end of the WHO global malaria eradication policy in 1972. The Sardinia project is presented as a case of "failure-as-success"; an ideological transformation was made, not simply for local political expediency, but more importantly because of the predominance of the modernist cultural model of "progress through technology" that characterized international Public Health in the postwar era.

Animals↗
PubMed1992

Factors influencing the activity of Bacillus thuringiensis var. israelensis treatments.

Environmental factors influence the effectiveness of microbial control agents in mosquito control programs. Four of these factors (water temperature, larval density, sunlight and the effect of associated filter feeders) were studied with Bacillus thuringiensis var. israelensis under laboratory and semifield conditions in Europe using different instars of Aedes vexans, Ae. aegypti and Culex pipiens. Bioassays conducted at a low temperature (5 degrees C) yielded 10-fold higher LC50 and LC90 values compared with those conducted at a high temperature (25 degrees C). The efficacy of B.t.i. decreased in a linear manner with increasing larval density. Sunlight can reduce the effectiveness of B.t.i. by several times. Competition in food intake by filter feeding Daphnia resulted in lower mortality of mosquito larvae after B.t.i. applications.

Aedes↗
PubMed2005

Metro Atlanta responds to West Nile virus: a coordinated public health response.

Three and a half million people live in metropolitan Atlanta, in multiple counties with varying population bases, resources, issues and separate boards of health. Historically, public health issues have been managed within each county, with very little sharing of information among counties. The 1999 West Nile virus (WNV) outbreak in the Northeast caused public health officials in Atlanta to recognize the potential for the disease to spread to Georgia and the need to develop a coordinated, multi-jurisdictional response plan. This plan would need to address a new disease with little scientific data to predict how it might behave in a new environment and would also require closely coordinated communication among the local/state public health entities and elected officials. In early 2000, staff from the five health districts in the metro Atlanta area and the state health department voluntarily convened the Metro Atlanta Surveillance Task Force (MASTF) to create the Metro Atlanta West Nile Virus Response Plan. This plan utilizes a coordinated effort encompassing public education, surveillance, and mosquito control. With this plan in place, when the first human case of WNV was detected in Atlanta, the public heard consistent health messages about preventive measures to lower their risk of illness and the metro counties were able to carry out a successful uniform approach to mosquito control. This plan has received recognition by the National Association of County and City Health Officials (NACCHO) as a 2004 Model Practice, demonstrating exemplary and replicable qualities in response to a local public health need. Since the early days of the emergence of WNV in the metro Atlanta area, MASTF has continued to be a viable, evolving entity, managing and anticipating health issues. The MASTF plan is a successful effort to develop consistent policies and procedures for disease surveillance in a heavily populated area with multiple local health departments.

Communicable Disease Control↗
PubMed1978

Epidemiology of St. Louis encephalitis and other acute encephalitides.

Cases of acute encephalitis reported to the CDC are divided into five groups: arboviral (8% of the 1965 to 1974 total), enteroviral (2%), post-infection (25%), encephalitis due to other known agents (3%), and encephalitis of indeterminate etiology (62%). With increased use of live virus vaccines against measles, mumps, and rubella, postinfection encephalitis has decreased, and SLE had become one of the most common preventable encephalitides in the United States. In 1975 SLE virus caused at least 1,791 cases of encephalitis, 42% of the reported total. In addition, the age distribution of persons with encephalitis of indeterminate etiology suggests that SLE virus may be an important contributor to that caegory during the summer months. The warm-weather transmission cycle of the SLE virus is well established. The reservoir is birds. The principal vector is the peridomestic C. pipiens mosquito in the Midwest and South and the rural C. tarsalis in the West. Man is an incidental and dead-end host. The winter reservoir is unknown. Human illness occurs in the summer. Asymptomatic human infections are about 200 times more common than symptomatic infections. Clinical attack rates and severity of illness increase with age. Case-fatality ratios of 35 to 38% have been reported for persons 60 years of age and older. For unknown reasons, SLE virus causes periodic major epidemics. The epidemics are more noticeable and better studied in major cities, but they probably affect rural areas as well. SLE is more common in areas of the country with warm climates. Epidemics in the North, when they occur, begin later but are of the same duration as epidemics in the South. Presumably, large epidemics of SLE can be prevented by mosquito control programs. Cumbersome and possibly insensitive diagnostic techniques impair our evaluation and understanding of SLE and other encephalitides. Insufficient information about the factors causing or preceding SLE epidemics impedes successful preventive measures. The use of emergency mosquito control programs after an epidemic has started has not been shown to reduce the number of human cases.

Age Factors↗
PubMed2005

An entomopathogenic fungus for control of adult African malaria mosquitoes.

Biological control of malaria mosquitoes in Africa has rarely been used in vector control programs. Recent developments in this field show that certain fungi are virulent to adult Anopheles mosquitoes. Practical delivery of an entomopathogenic fungus that infected and killed adult Anopheles gambiae, Africa's main malaria vector, was achieved in rural African village houses. An entomological inoculation rate model suggests that implementation of this vector control method, even at the observed moderate coverage during a field study in Tanzania, would significantly reduce malaria transmission intensity.

Animals↗
PubMed2006

An edible vaccine for malaria using transgenic tomatoes of varying sizes, shapes and colors to carry different antigens.

Malaria, a disease caused by protozoan parasites of genus Plasmodium, is one of the world's biggest scourges. Over two billion individuals reside in the malaria endemic areas and the disease affects 300-500 million people annually. As a result of malarial-infection, an estimated three million lives are lost annually, among them over one million children (majority under 5 years of age). The mortality due to malaria has increased because of the spread of drug-resistant strains of the parasite, the breakdown of health services in many affected areas, the interaction of the disease with human immunodeficiency virus (HIV) infection, and possibly the effects of climate change. Infants and young children with malaria often die from severe anemia, cerebral involvement,or prostration caused by overwhelming infection; many new borns die from complications of low birth weight caused by maternal malaria during pregnancy. The scarce economic resources and lack of communication, infrastructure and adequate means of travel in the endemic areas make it extremely difficult to implement traditional infection control measures (i.e., mosquito control, preventive anti-malarial drugs and nets). To make the matter worse, both malarial parasites and its insect vectors are increasingly becoming resistant to anti-malarial agents (chloroquine) and insecticides (both DDT and melathione and related chemicals), respectively. By conventional wisdom, the immune mechanisms responsible for protection against malaria will require a multiple of 10-15 antigen targets for proper protection against various stages of malarial infection. By standard vaccination protocols, such a large number of targets would not be appropriate to be used for vaccination as a single dose due to antigenic competition. It would be almost impossible to immunize over two billion individuals who live in malaria susceptible areas with several carefully crafted immunization schedules delivered 4-6 weeks apart in the form of two different antigens as a single dose. Besides, if immunization schedules could be arranged, the stability of vaccines carrying different malarial antigens, their transport, and the logistics of vaccination would be an almost impossible task to achieve under the current fiscal constraints. We are proposing a unique way to circumvent these logistical difficulties to deliver the malaria vaccines to every susceptible home at a small fraction of a cost. We hypothesize that the anti-malaria edible vaccines in transgenic tomato plants where different transgenic plants expressing different antigenic type(s). Immunizing individuals against 2-3 antigens and against each stage of the life cycle of the multistage parasites would be an efficient, inexpensive and safe way of vaccination. Tomatoes with varying sizes, shapes and colors carrying different antigens would make the vaccines easily identifiable by lay individuals.

Administration, Oral↗