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PubMed1995

Mark-release-recapture experiments to estimate the efficiency of the light trap in collecting Japanese encephalitis vector mosquitoes.

Efficiency of the light trap in collecting females of Culex tritaeniorhynchus, the principal vector mosquito of Japanese encephalitis, was evaluated by mark-release-recapture experiments. Females collected with dry ice in the field were marked and released in a pigsty. The recapture rate of marked females by the light trap was so low as around 1% or lower. Owing to this low efficiency, it is not likely that the light trap can be a useful tool in the control of Japanese encephalitis.

Animals↗
PubMed1991

Chagas disease control in Brazil: which strategy after the attack phase?

The main target of Brazilian Chagas Disease Programme (CDP) has been the control of domestic triatomine bugs, since more than 80% of human disease is attributable to transmission by these vectors. The global CDP attack phase began in 1983, after a political and technical decision to cover all the 2,400 municipalities of the endemic area with regular insecticide spraying. At present, this vertical and almost military approach is ending, with good entomological results in nearly 70% of the whole area and drastic reduction of the disease. The consolidation of the programme now presupposes the development of a vigilance phase, carried out at regional levels and supported by intensive community participation. Not only residual triatomine foci, but chiefly those resulting from eventual house invasion by secondary sylvatic or peri-domestic species must be detected and sprayed, so avoiding new colonization. More than 700 Brazilian municipalities are in this phase, still controlled by the Ministry of Health ("SUCAM"), with regional voluntary posts established in each municipality to coordinate and respond to any denuciation of infested premises. Special attention is given to the peridomestic environment, where most of the foci are being detected after the attack phase and where the current insecticides do not work so well as indoors. The great challenge is to maintain a continuous and effective surveillance against triatomines, chiefly in the poorest and more isolated rural areas. At medium term, the trend of domestic Brazilian triatomines will depend on three different kinds of factors such as: those linked to the improvement and continuity of the programme (political decision), those that depend on human activity over the environment (extensive agriculture, deforestation, urbanization, etc.) and those associated with promotion and organization of the communities. New strategies and improvement of the existing ones must still be a target for research in the present context of Brazilian triatomines. Also, new ecological situations must be foreseen, such as the expansion of agricultural frontier, rupture of the Amazonian barrier, etc. Finally, an integrated control of Chagas Disease must emphasise complementary activities such as housing improvement and the active control of blood banks to eliminate transfusional transmission, besides the development of a realistic medical care system.

Animals↗
PubMed1995

Field trial of an ecological approach for the control of Phlebotomus argentipes using mud & lime plaster.

A pilot study for the control of Ph. argentipes, a known vector of kala-azar in India, was carried out using an ecological approach. Of the 15 houses selected for the study 10, including the cattle sheds and latrines, were plastered with a mixture of mud and lime, up to a height of 1.22 m taking care to seal all cracks and crevices. The remaining five houses were left unplastered and were considered as control areas. The pre-treatment and post-treatment resting densities of the sandfly were monitored both in treated and untreated houses. A sudden drop in the sandfly density was noticed in the treated houses, whereas there was no significant reduction in the check houses, suggesting an effective control.

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PubMed1997

Vector abundance and behaviour in an area of low malaria endemicity in Bataan, the Philippines.

The vectorial importance of known and potential vectors in Morong, Bataan, Philippines was assessed based on human and animal baited collections of adult mosquitoes and on larval collections. Anopheles flavirostris, the principal vector in the Philippines, was the most abundant among human landing catches, followed by An. maculatus sensu lato (s.l.). Both showed similar seasonal abundance with a peak during the early drier part of the year, which coincided with the peak in malaria cases. Both An. flavirostris and An. maculatus s.l. fed throughout the night with the broad peak of capture from 00:00 to 04:00 and from 22:00 to 00:00, respectively. The two species had similar parous rates (0.76 and 0.72, respectively) giving an average life span equivalent to four feeding cycles. Neither vector was abundant with average human landing rates on collectors of 0.6 and 0.4 mosquitoes per person per night, respectively over the study period. An. maculatus s.l. showed a stronger preference for outdoor feeding compared to An. flavirostris. An. maculatus s.l. was markedly zoophilic with a biting rate on water buffalo 50 times the human landing rate. An. flavirostris was less zoophilic with a corresponding ratio of 7.5. It was concluded that in this area, An. flavirostris is the principal vector. The combination of localised transmission, late night biting pattern and localised breeding sites of An. flavirostris suggest that the use of bed nets and environmental management are relevant control measures that can be implemented through community participation.

Animals↗
PubMed1998

Susceptibility to trypanosomosis of three Bos indicus cattle breeds in areas of differing tsetse fly challenge.

Studies to assess the differences in susceptibility to trypanosomosis among Bos indicus cattle breeds (Maasai Zebu, Orma Boran and Galana Boran) were conducted under conditions of varying tsetse fly challenge at the Nguruman escarpment in south-western Kenya, for a period of 1 year. It was found that under tsetse challenge quantified as high, Maasai Zebu and Orma Boran were less susceptible than Galana Boran to trypanosome infections, as judged by the significantly lower incidence of infection, development of less severe anaemia, fewer requirements for trypanocidal drug treatments, higher growth rates and fewer mortalities. In the area where tsetse challenge was considered low as a result of a tsetse fly control operation using odour-baited traps, only the Maasai Zebu and Orma Boran were compared. No significant differences in the incidence of infection, degree of anaemia or growth rates were observed between the two breeds, but all were significantly different from their counterparts in the high tsetse challenge area. These results suggest that there is variation in resistance to trypanosomosis among Bos indicus cattle breeds that could be exploited as part of the integrated trypanosomosis control programmes in East Africa.

Anemia↗
PubMed2006

Malaria transmission and insecticide resistance of Anopheles gambiae (Diptera: Culicidae) in the French military camp of Port-Bouët, Abidjan (Côte d'Ivoire): implications for vector control.

An important vector control program is ongoing to lower the risk of malaria transmission in the French military camp of Port-Bouët, Abidjan (Côte d'Ivoire). However, some autochthonous malaria cases are regularly suspected. An entomological survey was conducted in June 2004 in the camp to assess malaria transmission and evaluate the pyrethroid and organophosphate resistance of the malaria vectors. The average mosquito biting rate was 178.0 bites per person per night. Mosquitoes belonging to the Anopheles gambiae (Diptera: Culicidae) complex and the Anopheles funestus group were collected. An. gambiae s.s. molecular form M was the only species of the An. gambiae complex present. The average number of An. gambiae bites was approximately 44.3 per person per night. The circumsporozoite index was 0.38% and the entomological inoculation rate estimated to be 1.2 infective bites per week for the study period. The kdr and ace1 gene frequencies in the An. gambiae population were 0.70 and 0.15, respectively. Personnel living in the French barracks of Port-Bouët are thus at high risk of being bitten by parasite-infected mosquitoes. Such an entomological inoculation rate, usually found in African peri-urban environments, was unexpected considering the extensive effort deployed to control mosquitoes in the camp. Insecticide resistance could explain the inefficacy of the vector control program but the spraying strategy is also questionable.

Animals↗
PubMed2006

Laboratory evaluation of pyriproxyfen and spinosad, alone and in combination, against Aedes aegypti larvae.

In this study, the efficacy of pyriproxyfen and spinosad, alone and in combination, was evaluated against the dengue vector Aedes aegypti (L.). Larval bioassays were carried out on susceptible mosquito larvae to determine the concentration-mortality responses of mosquitoes exposed to each insecticide alone and in mixture. Synergism between pyriproxyfen and spinosad was determined by the calculation of a combination index (CI) by using the isobologram method. For pyriproxyfen, LC50 and LC95 were 1.1 x 10(-4) (1.0 x 10(-4)-1.1 x 10(-4)) and 3.2 x 10(-4) (2.9 x 10(-4)-3.6 x 10(-4)) mg/liter, respectively. Pyriproxyfen acted at very low concentrations by inhibiting the adult emergence of Ae. aegypti (97% inhibition rates at 3.3 x 10(-4) mg/liter). Spinosad activity was -500 times lower than that of pyriproxyfen against the Bora strain, with LC50 and LC95 values estimated at 0.055 (0.047-0.064) and 0.20 (0.15-0.27) mg/liter, respectively. A binary mixture of pyriproxyfen and spinosad was realized at the ratio 1:500 by considering the values of the LC50 obtained for each product. The LC50 and LC95 of the mixture were 0.019 (0.016 - 0.022) and 0.050 (0.040 - 0.065) mg/liter, respectively. The mixture combined both the larvicidal activity of spinosad and the juvenoid action of pyriproxyfen. From the LC70 to LC99 a significant synergism effect was observed between the two insecticides (CI ranged from 0.74 to 0.31). This strong synergism observed at high concentrations allows a reduction by five and nine-fold of pyriproxyfen and spinosad amounts to kill almost 100% mosquitoes. Combination of pyriproxyfen and spinosad may then represent a promising strategy to improve mosquito control in situations with insecticide-resistant Aedes dengue vectors.

Aedes↗
PubMed2006

Fumigant and repellent properties of essential oils and component compounds against permethrin-resistant Pediculus humanus capitis (Anoplura: Pediculidae) from Argentina.

The repeated use of permethrin and other insecticides for the control of head lice, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), during past decades has resulted in the development of marked levels of resistance. Thus, new alternative insecticides are needed for the control of head lice. We studied the fumigant and repellent properties of essential oils from 16 native and exotic plants in Argentina, and 21 chemical components against permethrin-resistant head lice from Argentina. With a direct vapor-exposure bioassay, the most effective oil was from the native Myrcianthes cisplatensis Cambess (Myrtaceae) with a time to 50% knockdown (KT50) of 1.3 min, followed by exotic species, Eucalyptus cinerea F.V. Muell., Eucalyptus viminalis Labill., and Eucalyptus saligna Smith. with KT50 values of 12.0, 14.9, and 17.4 min, respectively. The most effective components were 1,8-cineole and anisole, with KT50 values of 11.1 and 12.7 min, respectively. Regression analysis of KT50 values and vapor pressures and water-partition coefficients for the essential oil components revealed that the most effective fumigants were among the more volatile components. Repellency assays indicated that the essential oil from Mentha pulegium L. and its benzyl alcohol component were the most effective repellents, having repellency indices of 75.5 and 57.8%, respectively. Thus, some Argentinean plants contain essential oils and components that function as fumigants or as repellents and thereby show potential for development of new control products for head lice.

Animals↗
PubMedDate not supplied

[40 cases of dengue (serotype 3) occurring in a military camp during an epidemic in New Caledonia (1989). The value of vector control].

An epidemic of dengue occurred at the beginning of 1989 in New Caledonia. About 18 p.c. of the population was stricken (25,000 to 30,000 estimated clinical cases). The military camp of Plum was stricken too, but a prompt vector control was established. 8.6 p.c. of the strength was affected by classical dengue without severe hemorrhagic manifestations. Such prevalence is lower than the one rated in the civil population, demonstrating the major importance of vector control to limit spreading of such an epidemic as a tetravalent vaccine is not yet available.

Aedes↗
PubMed1981

Studies on biting Simulium damnosum s.l. at a breeding site in the Onchocerciasis Control Programme area during and after an interruption of insecticidal treatments.

The increase of population of biting S. damnosum s.l. at a breeding site situated within the Onchocerciasis Control Programme area of West Africa following a temporary cessation of insecticidal treatments was studied by making every day collections on human bait at five catching sites and for 2--3 days per week at seven others, between 17 January and 9 April 1977. Observations on pupal and larval densities, water and air temperatures, relative humidity and water level were also made. The results showed that there was an interval of 23 days between the last application of insecticide and the appearance of the first nulliparous biting flies. This coincided with the finding of the first S. damnosum larvae. Subsequently, the biting densities increased following a geometric progression from about 10 flies per day to a maximum of 188 per day, giving a daily rate of increase of 1.07. Ten days after the re-application of insecticide, biting densities had fallen to about 5% of the pre-control level giving a daily rate of decrease of 0.74. Very little dispersion was observed with biting rates falling to 5% at 3000 m. perpendicular to the river. At these sites nullipars predominated. Conversely along the axis of the river densities at 1000 m away had to only 68% and were composed mainly of parous flies. Studies on diel activity showed the greatest biting activity between 15.00 h and 18.00 h with a lesser period of activity between 07.00 and 10.00 h. The significance of these observations in future planning of control strategy is discussed.

Animals↗
PubMed1993

Chagas' disease: control and surveillance through use of insecticides and community participation in Mambaí, Goiás, Brazil.

This article describes the nature and effectiveness of methods developed for longitudinal surveillance and control of Chagas' disease vectors in Mambaí, Brazil. The surveillance effort made use of an education program in the schools, community leader and resident participation, specific surveillance equipment (Gómez-Núñez boxes, instructive posters, and instructive calendars with special detection papers), periodic manual collection of triatomines, and a network of collection posts. Spraying of infested houses was accomplished partly by community leaders who received special training for this purpose. The methods used offer an affordable approach to triatomine surveillance and control well-suited to use in large-scale national programs.

Animals↗
PubMed2000

[Peridomiciliary changes and implications for Triatoma brasiliensis control].

A total of 9,906 annexes from 1,541 rural dwellings of Boa Viagem County, Ceará, Brazil, infested by Triatoma brasiliensis and Triatoma pseudomaculata were investigated and immediately sprayed with pyrethroid insecticide, followed by revisions at 6, 12, and 18 months. The initial infestation rate of annexes was 4.0%, with predominant infestation in animal shelters (7.0%). Mean insect density was low, regardless of triatomine species or type of annex. A progressive decrease in the number of initial annexes was observed (66% of remaining annexes), mainly those classified as "piles of materials". Only 3% of the annexes were modified by the population. New constructed annexes were important as new foci of infestation. Some 25% were infested at the end of observation period, significantly more than the "old" annexes (4.0%), a difference attributed to insecticide spraying at the beginning of the intervention. Reinfestation occurred slowly and was more frequent in animal shelters No differences were observed between traditional pyrethroid and slow-release organophosphate formulations. Selective spraying of "new" annexes is recommended.

Animals↗
PubMed1992

Control of Oropsylla hirsuta, a plague vector, by treatment of prairie dog burrows with 0.5% permethrin dust.

Permethrin, a pyrethroid insecticide, applied on two plots with a pressurized hand-held duster at mean rates of 2.3 and 4.0 g per burrow, was used to determine control levels for Oropsylla hirsuta fleas, a vector of bubonic plague, in black-tail prairie dog, Cynomys ludovicianus, burrows in northern Colorado during the summer of 1988. Burrows were sampled by "flagging" at day 0 and weeks 1, 3, 6, 9, and 12 to determine the mean number of fleas per burrow and percentage of burrows with at least one flea. The 4.0 g per burrow rate was highly effective (P less than 0.001) in controlling fleas for a period of 3 mo, whereas the 2.3 g per burrow rate was not.

Animals↗
PubMedDate not supplied

A pilot study to control Lutzomyia umbratilis (Diptera:Psychodidae), the major vector of Leishmania braziliensis guyanensis, in a peri-urban rainforest of Manaus, Amazonas State, Brazil.

In the second half of 1980, 112 (or ca. 16%) of the inhabitants of the new settlement of São José, city of Manaus, contracted cutaneous leishmaniasis whilst clearing their properties of terra firme rainforest. With the aid of SUCAM, the authors carried out a pilot study to investigate the feasibility of reducing populations of Lutzomyia umbratilis, the local silvatic vector of Leishmania braziliensis guyanensis, by spraying insecticide on its favoured diurnal resting sites, the bases of the larger forest trees. Most manvector contact is at these resting sites and, therefore, it was encouraging to record a marked reduction of the tree-base populations of L. umbratilis for 21 days following just one application of D.D.T. emulsion in an area 200m square. Most of the treated trunks were not occupied by L. umbratilis for at least eleven months. Suggestions for extending the pilot study are made, and the need for collaboration with a clinical team is emphasized. Leishmania b. guyanensis is the aetiological agent of "pain bois", which is hyperendemic from French Guiana to central Amazônia. In the absence of proven vaccines or methods of vector control, some simple methods for limiting transmission of Le. b. guyanensis to man are listed.

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