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PubMed2001

Mosquito larval control with Bacillus sphaericus: reduction in adult populations in low-income communities in Nonthaburi Province, Thailand.

During 1999 and 2000 several larvicidal treatments of Bacillus sphaericus strain 2362 water dispersible granular (WDG) formulations were made at 50 to 200 mg/m2 in mosquito developmental sites in low-income communities in Nonthaburi Province, Thailand to determine whether larviciding dense populations would results in a noticeable reduction of adult mosquitoes in small treated areas. In the treated area in 1999 (Soi Jumpa), immature populations were suppressed to extremely low levels for extended periods, especially at the higher dosages. This decline in immature populations was followed by a substantial decline in adult mosquitoes. There was a lag of 7 to 14 days post-larval treatments before maximum decline in adults was noted. Adults that emerged prior to treatments survived for 7-14 days or longer, thus no drastic reduction was noted soon after treatments. Despite a slight resurgence in adult mosquitoes during the middle of the experimental period, adult female mosquitoes (over 98% Cx quinquefasciatus), remained low during the 5-month period of trials. During the last 2 weeks (17 days post last treatment) of the experimental period, female populations reached the pre-treatment level. During the 2000 tests at Wat Pikul reduction in larvae was 87-98% for 7 weeks after first treatment at 200 mg/m2, resulting in a reduction of 24 to 73% (2 and 7 days post-treatment respectively) and 87 to 98 (2-6 weeks) in the adults. In the second and third treatments at 50 mg/m2, larval control and subsequent adult reduction were lower and shorter-lived than at the high dosage, and the fourth treatment at 100 mg/m2 did not yield a high level of reduction in the larvae (18 to 33%), but reduction of adults was still 80%. The final fifth treatment at 200 mg/m2 yielded only 18% control of larvae, suggesting tolerance to B. sphaericus at this site. It was shown that at both treated sites repeated treatments with a larvicide such as B. sphaericus could result in substantial reduction in adult mosquitoes. Vigilance for detection of resistance development should be practiced, as resistance could emerge in certain populations following a few treatments.

Animals↗

PubMedDate not supplied

Control of Chagas disease vectors.

Most Latin American countries are making dramatic progress in controlling Chagas disease, through a series of national and international initiatives focusing on elimination of domestic populations of Triatominae, improved screening of blood donors, and clinical support and treatment of persons infected with Trypanosoma cruzi. Some countries, particularly Uruguay, Chile and Brazil, are sufficiently advanced in their programmes to initiate detailed planning of the subsequent phases of Chagas disease control, while others such as Peru, Ecuador, and Mexico, are currently applying only the initial phases of the control campaigns. In this review, we seek to provide a brief history of the campaigns as a basis for discussion of future interventions. Our aim is to relate operational needs to the underlying biological aspects that have made Chagas disease so serious in Latin America but have also revealed the epidemiological vulnerability of this disease. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.

Animals↗

PubMed2005

Efficacy of botanical insecticides from Piper species (Piperaceae) extracts for control of Ruropean chafer (Coleoptera: Scarabaeidae).

Biopesticides, including botanicals, can offer a safe and effective alternative to conventional insecticides for controlling major insect pests within an integrated pest management program. The current study highlights the practical application of a botanical insecticide for controlling a major insect pest of turfgrass: European chafer, Rhizotrogus majalis (Razoumowsky). Greenhouse and field trials were conducted to test the efficacy of a botanical formulation based on black pepper, Piper nigrum L. (Piperaceae), seed extracts to R. majalis larvae. The 7-d P. nigrum extract LC50 for R. majalis third instars was 2.5%. Successful treatment in the field was accomplished with the application of a 2% P. nigrum formulation to turfgrass infested with R. majalis second and third instars, whereas 4% extract was required in a second field trial with older third instars. The 2% pepper extract activity was comparable with the conventional insecticide diazinon in the first field trial. However, the 4% pepper extracts significantly affected the earthworm populations in treated plots compared with diazinon in the second field trail. The analysis of soil residues for piperamides in the P. nigrum extract determined a half-life of 1 - 2.6 d in the first and second field trials, respectively. This confirmed the expectation that under field conditions the residual activity would be less than conventional insecticides, thereby reducing the environmental risk associated with pesticide use. We recommend the pepper formulation for spot treatment applications when population densities reveal an epicenter of infestation rather than broadcasting over large areas, thus helping to minimize cost and negative affects on nontarget invertebrates.

Animals↗

PubMed1996

The USDA Forest Service pesticide spray behavior and application development program--an overview.

The USDA Forest Service, even though a minor user of pesticides, has maintained an active program for understanding the performance, atomization, evaporation, efficacy, environmental fate, atmospheric dispersion, and environmental impact of chemical and biological insecticides. Since its self-imposed ban on use of dichloro diphenyl trichloroethane (DDT) in 1964, the USDA Forest Service has pursued insecticides that are less persistent and have reduced potential for impact on nontarget organisms, application technology that supports their efficient and efficacious use, and computer models that predict insecticide fate in the environment. This program has been active over the last 3 decades, beginning with research for chemical insecticide substitutes for DDT, progressing in time to biological insecticides and other biorational control agents. In our effort to make the less persistent insecticides work under forestry conditions, it was necessary to investigate insecticide monitoring, detection, and sampling methods; application systems; atmospheric influences; tank mixes and adjuvants; nozzles and atomization; evaporation; spray deposition and canopy penetration; biological response; and environmental fate. This paper reviews some of this work that might be applicable to mosquito control.

Animals↗

PubMed1993

An historical review of malaria, kala-azar and filariasis in Bangladesh in relation to the Flood Action Plan.

This paper reviews the evidence of a link between flood control and vector-borne disease in Bengal/Bangladesh. Malaria is historically associated with reduced flooding and embankment construction in the flood plains of Bengal. The land west and south of the Jamuna river was highly malarious in 1916 but is not so today. The lands east of the Jamuna now have a higher, though still small, risk. The reduction in health risk can be attributed to the intensification of land use and human population density. Although there are many mosquito species, the abundance of the former malaria vector appears to have declined as environmental change removed its breeding sites. Visceral leishmaniasis (kala-azar) is a serious disease which is fatal if left untreated. It occurs in irregular, periodic epidemics and is currently increasing in Bangladesh. In the past, malaria and kala-azar were confused and the prevalence of both may have been increased by embankment programmes. Both diseases are unstable and there is insufficient historical information to predict, with certainty, the consequences of environmental change. Reduced flooding accompanied by increased pollution will probably control the malaria vector. More information is needed about the response of the kala-azar vector to flooding. Bancroftian filariasis is non-fatal but causes chronic morbidity. It has had a widespread but usually low prevalence in Bangladesh, with both rural and urban foci. There are few recent data. Increasing organic pollution and drainage obstruction are expected to favour the vector and increase transmission.

Animals↗

PubMed1996

Effect of tsetse control on trypanosome prevalence in livestock: problems of experimental design and statistical interpretation--a case study in northern Côte d'Ivoire.

As part of a study on livestock productivity under trypanosomosis risk in the region of Boundiali, northern Côte d'Ivoire, 21 herds of cattle (N'Dama, Baoulé and Zebu crosses) and 20 flocks of Djallonké and Djallonké x Sahel sheep were monitored monthly for body weight, packed red cell volume and trypanosomal parasitaemia over various periods between January 1984 and December 1992. A tsetse control campaign using biconical traps impregnated with alpha-cypermethrin started in December 1987. Tsetse control reduced the relative tsetse density by over 95% between 1988 and 1992, and this was associated with reductions in the prevalence of Trypanosoma congolense over the same period of over 90% both in sheep and cattle. Average reductions in the prevalence of T. vivax were lower, on average 68% in adults and 85% in young animals. Attempts were made in the design of the study to allow comparisons between controlled and uncontrolled areas; however, there were too many confounding and uncontrollable factors to allow such comparisons to be made. It was necessary, therefore, to compare data collected from all herds and flocks before and after the intervention, with the consequential difficulties in accounting for uncontrollable year-to-year variations in factors affecting trypanosome prevalence in livestock.

Animal Husbandry↗

PubMed1988

A model of tsetse-transmitted animal trypanosomiasis.

The data needed to develop analytical models of trypanosomiasis transmission have become available only recently. By making some simplifying assumptions, models of the dynamics of the disease in vector, cattle and wild mammal populations can be constructed in order to determine criteria for successful disease control by mass and targetted chemotherapy, and by vector control. The heterogeneity in transmission due to tsetse fly feeding preferences and the variability of immunological characteristics among the vertebrate hosts account for differences in prevalence of Trypanosoma vivax and T. congolense, and also lead to an increase in the basic reproductive rates of the parasites and a corresponding decrease in the vector population density threshold for disease eradication or persistence. The long life-span of the vectors relative to the duration of the parasites' developmental period lead to high infection rates in the vector and high values of R0. The efficacy of chemotherapeutic regimes depends on the relationship between treatment rate and the duration of prophylaxis conferred by the drugs used. The model's predictions of the effects of vector control are shown to be in broad agreement with published field data for Mkwaja Ranch, Tanzania. Vector control programmes are frequently blighted by reinvasion, and the implications of this are discussed in terms of a model for fly immigration. With immigration of vectors, the disease is always endemic, though the infection rate in the fly population is modified by the effect of differential mortalities inside and outside the controlled area on cohorts of incubating flies. Sensitivity analysis of the model, using Monte-Carlo methods, enables an assessment of the relative importance of the parameters to be made. The results emphasize the need for studies of the wild animal reservoir to be carried out alongside entomological surveys. The relative accuracy with which field measurements need to be made in order to minimize the uncertainty in predictions of trypanosomiasis prevalence is discussed.

Animals↗

PubMed1969

Variations in the ecology of Glossina spp. with special reference to Nigerian populations of Glossina tachinoides.

During the last decade, an increasing number of instances have been noted of tsetse flies occupying unusual, and often man-made, habitats. Recently, some aberrant populations have become important, either because they have drawn attention to new aspects of trypanosomiasis transmission or because they have necessitated modifications of established tsetse control methods.From observations made on atypical tsetse populations in Nigeria, the author has classified the various types of intra-specific behaviour patterns observed and offers an interpretation. At least 1 species, Glossina tachinoides, is normally extremely versatile ecologically but some populations are now so adapted to man-made habitats that they can probably be explained only on the basis of subspeciation. Some populations of other species of tsetse, such as G. fuscipes and G. morsitans, seem also to be involved in atypical behaviour patterns.The investigations emphasize the need to clarify the role of tsetse flies in the epidemiology of the trypanosomiases and the suitability of established tsetse control measures in areas where the pattern of vector behaviour differs from that of more conventional foci of disease transmission. Much of the African continent is rapidly changing to meet the needs of large human populations and it is therefore envisaged that many more tsetse populations will become adapted to habitats dominated by man, as the only alternative to extinction, so that the problem of trypanosomiasis may remain as great, or become greater, in the future.

Animals↗

PubMed1999

[Elimination of vectorial transmission of Chagas disease in Brazil].

The control of vectorial transmission of Chagas disease in Brazil has been systematized and structured into a national program since 1975 when regulations were set up on the basis of entomological and sero-epidemiological studies which permitted the delimitation of areas at risk of vectorial transmission in the whole country as well as the orientation of the chemical control of domiciliary vector populations. The authors present the original data collected throughout the years comparing them with the present data. The evaluation reveals a virtual interruption of the transmission for Triatoma infestans and the remaining possibility of transmission, at very low levels, for native vector species in different areas of the country. It is emphasized that it is important to maintain constant entomological vigilance in order to prevent the reestablishment of transmission.

Animals↗

PubMed1997

Breeding habitats of vector sandflies and their control in India.

In India Phlebotomus argentipes and Phlebotomus papatasi are the proven and suspected vectors of visceral leishmaniasis respectively. In the past, only a few samples from the field yielded sandfly immatures though there were many adults in the vicinity. This might be because of dearth of information on the various factors influencing the oviposition of the gravid females as well as survival and development of immatures. Therefore, available information on these aspects has been reviewed so as to highlight the imperative of undertaking further studies on the ecology of immatures in field conditions.

Animals↗

PubMed2002

[Variability according to the individual of the efficacy of repellents with a base of vegetable oils in the individual protection against Simulium damnosum s. l. bites].

In Ivory Coast, treatments against black flies larva are interrupted since December 1998 and these flies are back everywhere in abundance. They are now a severe source of discomfort, so it is therefore very important to propose to rural populations a personal protection method against their bites. This article is about the individual attraction of fly boys on the efficiency of lotions and creams of the different repellents (coconut, palm nut, gobi). Our works were carried out in savanna zone (Niakaramandougou) and in forest zone (Soubré) in Ivory Coast. The methodology consisted in capturing black flies on volunteers whose legs were rubbed with repellent. Coconut, palm nut and gobi formulas (lotions and creams) were tested on Simulium damnosum s.l. During each session, which lasted from 07:00 am to 12:00 and from 03:00 pm to 06:00 pm, one person without repellent was used as a control person. The results show that the least efficient repellent (gobi) ensures nonetheless a reduction of 90% of the number of bites that an individual would have received if he was not protected by the repellent. Experimentations allows to say that for a given repellent and formulas (lotion and cream), there is no significant difference between the number of Simulium damnosum s. l. bites received by fly boys.

Animals↗

PubMed1991

Current status of kala-azar and vector control in China.

Kala-azar, which was prevalent in the vast area of China that lies to the north of the Yangtze River from the 1920s to the 1950s, is now effectively under control as a result of strenuous intervention since the founding of the People's Republic of China in 1949. Apart from 15-20 new cases that occur annually in the Keshi plain, Xinjiang Autonomous Region, the achievements of control practised in other former endemic areas in the plains have been significant and consolidated. In the mountainous areas in north-west China, where the vector, Phlebotomus chinensis, is abundant and canine visceral leishmaniasis is common, there are still sporadic cases of kala-azar. Also, in recent years, new infections have often occurred in the deserts of Xinjiang and western Inner Mongolia, although the reservoir of the infection has not been identified.

Adolescent↗

PubMed1990

Community participation in the control of tsetse flies. Large scale trials using the pyramid trap in the Congo.

An experiment of Glossina palpalis control was carried out by rural communities in 55 villages of the Niari river sleeping sickness focus (Bouenza region, Republic of the Congo). It was based on the use of a new trap, not requiring insecticide impregnation, in which the captured Glossina are preserved. The results show that this simple, cheap trap is an effective method of control, resulting in a considerable decrease in the tsetse population and is easily operated by the villagers. Screening surveys, using the indirect immunofluorescent test, conducted regularly in this focus, showed a decrease in the prevalence rate after the elimination of the flies. Long-term community participation is limited and must be improved by a better understanding of socio-cultural aspects and in certain cases must be associated with the work of a specialized team.

Animals↗

PubMed2006

Control of onchocerciasis.

Onchocerciasis is a filarial infection which causes blindness and debilitating skin lesions. The disease occurs in 37 countries, of which 30 are found in Africa (the most affected in terms of the distribution and the severity of the clinical manifestations of the disease), six in the Americas and one in the Arabian Peninsula. The latest WHO Expert Committee on Onchocerciasis estimated that in 1995 around 17.7 million persons were infected, about 270,000 of whom were blind and another 500,000 severely visually impaired. The disease is responsible for 1 million DALYs. Eye disease from onchocerciasis accounts for 40% of DALYs annually although severe skin disease is also recognized as of public health significance. Great progress has been made in the last thirty years in the control of onchocerciasis, both in Africa and the Americas, and this progress has been due largely to international public-private partnerships, sustained funding regional programmes, and new tools and technology. Landmarks in the global control of river blindness include the significant success of the Onchocerciasis Control Programme of West Africa (1975-2002), and the donation of ivermectin (Mectizan) by Merck & Co. Inc., in 1988, a medicine that is distributed to millions free of charge each year. Future major technical challenges of onchocerciasis control include ivermectin mass administration in areas co-endemic for the parasite Loa loa in the light of possible severe adverse reactions, ivermectin treatment in hypoendemic areas hitherto excluded from African control programmes, sustainability of ivermectin distribution, post-control surveillance for recrudescence detection, surveillance for emergence of resistance, and decisions of when to stop mass ivermectin treatments. There is the need to develop the appropriate information systems and diagnostic tools to help in accomplishing many of these tasks. A search for a second-line treatment or as an additional drug to ivermectin as well as a search for a macrofilaricide are issues that need to be addressed in the future.

Africa↗

PubMed2005

Laboratory study to investigate the efficacy of cyfluthrin EW treated nets against phlebotomine sandflies.

Toxic and feeding inhibition effect of cyfluthrin treated nets was assessed and compared with the activity of deltamethrin impregnated nets, before and after 2 and 4 washes against Phlebotomus papatasi. Impregnated cyfluthrin nets (50, 25, 12.5 mg active ingredient (a.i.)/m2) caused knock down and mortality rates higher than 90%, being of 100% at the highest dose, while the nets impregnated with deltamethrin (25, 12.5, 6.25 mg a.i./m2) showed low mortality rates (13.3-43.5%). Also after washing cyfluthrin at the dose of 50 mg a.i./m2 provided higher activity than deltamethrin (25 mg a.i./m2), being mortality rates within 24 hs of 66.7 and 48.9% for cyfluthrin and 38.0 and 2.1% for deltamethrin, respectively after 2 and 4 washes. Before washing, cyfluthrin (50 mg a.i./m2) significantly prevented blood feeding, with respect to both untreated (88.6%) and deltamethrin impregnated nets (56.8%). Deltamethrin (25 mg a.i./m2) showed low feeding inhibition (48.4%), although it was significantly higher than control. The washing of cyfluthrin impregnated nets (50 mg a.i./m2) produced a decrease of the feeding inhibition, being the reduction of 26.6% and 41.3%, respectively after 2 and 4 washes. Two washes of deltamethrin impregnated nets (25 mg a.i./m2) yielded a very high reduction of antifeeding inhibition (68.8%). These laboratory results if confirmed by field evaluation indicate cyfluthrin as good candidate for treatment of mosquito nets to be used against phlebotomine sandflies.

Animals↗

PubMed1986

[Control of vectors by trapping and its impact on sleeping sickness in a zone of high density of Glossina fuscipes quanzensis (Lefini River, People's Republic of the Congo)].

Tsetse control by trapping and its impact on the transmission of sleeping sickness in the high density area of Glossina fuscipes quanzenis (Léfini river, People's republic of Congo). The focus of human sleeping sickness of the Léfini river is of strategic importance for the People's Republic of Congo as it is located at an important junction which allows the trypanosomiasis to spread over the whole country. A campaign of tsetse control by trapping was undertaken in this focus, where an adjacent game reserve provides a continuous source of flies. The only practicable strategy was the use of a new model of trap with a permanent "killing cage" and which does not need to be impregnated with an insecticide. Transmission of sleeping sickness has been reduced by 1) decreasing the density of flies which are in close contact with man, 2) constantly eliminating flies likely to become infected and transmit the disease.

Animals↗

PubMed1991

Attraction of Glossina longipalpis (Diptera: Glossinidae) in Guinea-Bissau to odor-baited biconical traps.

The catches of tsetse flies, Stomoxys, and tabanids in biconial traps baited with different synthetic odors were compared in the Jopá-Cobiana Forest, northwestern Guinea-Bissau. Thirty-six traps, the baits of which were randomly interchanged each of 10 sampling days, were baited either with (a) 1-octen-3-ol (octenol) + phenols [4-methylphenol + 3-propylphenol] + acetone + N'dama cow urine ("urine"), (b) octenol + phenols + acetone, (c) octenol + phenols, (d) acetone, (e) acetone + urine, or (f) urine. Six of the traps were not baited (controls). A total of 3,172 tsetse flies (96% Glossina longipalpis Widemann, 3% G. morsitans submorsitans Newstead, and 1% G. palpalis gambiensis Vanderplank), 286 Stomoxys, and 571 Tabanidae was captured. G. longipalpis was caught in statistically greater numbers in traps baited with octenol + phenols + acetone. Traps baited with octenol + phenols, with or without acetone, caught the greatest numbers of tabanids. N'dama urine did not increase the catch of G. longipalpis. Stomoxys was not significantly attracted to any of the odors.

Animals↗

PubMed1998

Can anything be done to maintain the effectiveness of pyrethroid-impregnated bednets against malaria vectors?

Pyrethroid-treated bednets are the most promising available method of controlling malaria in the tropical world. Every effort should be made to find methods of responding to, or preventing, the emergence of pyrethroid resistance in the Anopheles vectors. Some cases of such resistance are known, notably in An. gambiae in West Africa where the kdr type of resistance has been selected, probably because of the use of pyrethroids on cotton. Because pyrethroids are irritant to mosquitoes, laboratory studies on the impact of, and selection for, resistance need to be conducted with free-flying mosquitoes in conditions that are as realistic as possible. Such studies are beginning to suggest that, although there is cross-resistance to all pyrethroids, some treatments are less likely to select for resistance than others are. Organophosphate, carbamate and phenyl pyrazole insecticides have been tested as alternative treatments for nets or curtains. Attempts have been made to mix an insect growth regulator and a pyrethroid on netting to sterilize pyrethroid-resistant mosquitoes that are not killed after contact with the netting. There seems to be no easy solution to the problem of pyrethroid resistance management, but further research is urgently needed.

Animals↗