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P Guillet

Publications and source records attributed to P Guillet.

At least 37 records · Page 2Linked to original sources
PubMed1999

Status of pyrethroid resistance in Anopheles gambiae sensu lato.

The present study confirms the presence of pyrethroid resistance among Anopheles gambiae s.l mosquitos in Côte d'Ivoire and reports the observation of such resistance in two other countries in West Africa (Benin and Burkina Faso). Malaria vector populations from Cameroon (Central Africa), Senegal (West Africa) and Botswana (southern Africa) were found to be susceptible to pyrethroids. In the most resistant mosquito populations, resistance to permethrin was associated with reduced mortality, not only with respect to this compound but also towards deltamethrin. Moreover, a significant increase in knockdown time was observed in some mosquito populations before any decrease in mortality, suggesting that knockdown time could be a good indicator for the early detection of pyrethroid resistance. In view of the current extension of such resistance, there is an urgent need to set up a network in Africa to evaluate its development. It is also vital that the impact of this resistance on pyrethroid-impregnated bednets be assessed.

Africa↗
PubMed1999

Pyrethroid cross resistance spectrum among populations of Anopheles gambiae s.s. from Côte d'Ivoire.

Field samples of Anopheles gambiae s.s. from Côte d'Ivoire were tested with 5 pyrethroids (cyfluthrin, lambda-cyhalothrin, alpha-cypermethrin, deltamethrin, permethrin), 1 pseudo-pyrethroid (etofenprox), and an organochlorine (DDT). With the use of World Health Organization diagnostic tests, 5 out of 6 samples were found cross-resistant to these insecticides. A strong decrease in knockdown effect and mortality was also observed when testing deltamethrin-impregnated nettings. With a polymerase chain reaction amplification of specific alleles diagnostic test, resistance was found associated with the presence of a kdr mutation. The strong correlation between kdr allelic frequency and resistance to DDT or etofenprox indicated that kdr was the main resistance factor for these 2 insecticides. On the contrary, a lower correlation was observed between kdr frequency and resistance to 4 of the 5 pyrethroids tested, suggesting that another mechanism was also involved, likely a metabolic detoxification. These results point out the necessity to monitor pyrethroid resistance and the presence of kdr before implementation of any impregnated bed-net programs for malaria control.

Alleles↗
PubMed1999

Diversity of malaria in rice growing areas of the Afrotropical region.

It is well known that 'in many instances the rice agrosystem perfectly fits the ecological requirements of pathogens or vectors' and in fact 'malaria, schistosomiasis and Japanese encephalitis are important vector-borne diseases associated with rice production in developing countries' (IRRI, 1987). In spite of these fears, rice cultivation has been on the increase in the African region in response to demographic and economic pressures. However, although rice fields provide suitable breeding places for Anopheles mosquitoes and rice cultivation leads to an increase in the biting rates, the species which are adapted to these sites are not the same in all parts of Africa. Several examples illustrate this phenomenon: An. funestus in the rice fields of Madagascar, An. pharoensis in saline water rice fields in the delta of the Senegal river, An. arabiensis in northern Cameroon and Burundi, An. gambiae Mopti form in the Kou Valley (Burkina Faso) and An. gambiae Savanna form in the rice fields of Kafine near Bouaké (Côte d'Ivoire). The vectorial capacities of these species are not the same and malaria inoculation rates are not necessarily increased in the riceland agroecosystem. The consequences for malaria of introducing rice cultivation depend on the situation before its introduction: it could be worsened in unstable malaria areas but not in stable malaria areas. Therefore, sound epidemiological and entomological knowledge are needed before causing any environmental modifications for agricultural purposes and there should be regular monitoring to avoid any outbreak.

Burkina Faso↗
PubMed1999

Current distribution of a pyrethroid resistance gene (kdr) in Anopheles gambiae complex from west Africa and further evidence for reproductive isolation of the Mopti form.

In the field, the kdr mutation, involved in pyrethroid resistance, has been found widely distributed in the Savanna form of Anopheles gambiae s.s., but never in wild populations of the Mopti form or An. arabiensis, even in areas where both occur in sympatry with resistant Savanna populations. Under laboratory conditions, Mopti and Savanna forms were fully able to interbreed and the kdr mutation was transmissible from one form to the other. Both forms appeared to be exposed to pyrethroid selection pressure in the field. The absence of the kdr mutation in the Mopti form and the total lack of Mopti-Savanna heterozygotes in field populations provides further evidence of a pre-copulatory barrier to gene flow between these two forms. Molecular markers, including kdr, are powerful tools for studying population genetics and circulation of resistance genes, and should be used through an integrated approach for a better understanding of the speciation process.

Africa, Western↗
PubMed1999

[Efficacy of permethrin-impregnated Olyset Net mosquito nets in a zone with pyrethroid resistant vectors. I--Entomologic evaluation].

The efficacy of permethrin-treated Olyset Net mosquito nets on malaria transmission and morbidity was studied in Kafine, a village located in the savanna region of the Cote d'Ivoire in Africa. After collecting sociodemographic, entomological, and parasitological data, bednets were distributed first in the southern half of the village and then in the whole village. Throughout the study period, mosquito specimens were captured on the skin of inhabitants at four points in the village between 6 PM and 6 AM both inside (but outside bednets) and outside houses. Prior to distribution of bednets, the mean biting rate (MBR) by Anopheles gambiae was 77.4 bites per man per night (b/m/n). The mean parturity rate (MPR) was 40.6 p. 100, the sporozootic index (SI) was 0.99 p. 100, and the mean entomological inoculation rate (MEIR) was 0.7 infectious bites per man per night (b+/m/n). Six months after distribution of bednets in the southern half of the village, MBR was 80.2 b/m/n, MPR was 32 p. 100, SI was 1.8 p. 100, and MEIR was 0.83 b+/m/n. After extending distribution to the whole village, data from November 1996 to July 1997 were as follows: MBR, 67.8 b/m/n; MPR, 20.1 p. 100; SI, 0.65 p. 100; and MEIR, 0.66 p. 100. From August 1977 to July 1998, data were as follows: MBR, 102.6 b/m/n; MPR, 26.2 p. 100; SI, 1.15 p. 100; and MEIR, 0.74 b+/m/n. Comparative analysis of these data showed that use of bednets had no effect on the bite or entomological inoculation rate. This is in agreement with the documented resistance of vectors in the study zone to permethrin. Despite the known stimulation/repulsion effect of permethrin, use of treated bednets had no real impact on transmission. This inefficacy could be related to the high prevalence (80 p. 100) of the Kdr gene (responsible for resistance) in the savanna form of Anopheles gambiae.

Adolescent↗
PubMed1998

Molecular characterization of pyrethroid knockdown resistance (kdr) in the major malaria vector Anopheles gambiae s.s.

Pyrethroid-impregnated bednets are playing an increasing role for combating malaria, especially in stable malaria areas. More than 90% of the current annual malaria incidence (c. 500 million clinical cases with up to 2 million deaths) is in Africa where the major vector is Anopheles gambiae s.s. As pyrethroid resistance has been reported in this mosquito, reliable and simple techniques are urgently needed to characterize and monitor this resistance in the field. In insects, an important mechanism of pyrethroid resistance is due to a modification of the voltage-gated sodium channel protein recently shown to be associated with mutations of the para-type sodium channel gene. We demonstrate here that one of these mutations is present in certain strains of pyrethroid resistant A. gambiae s.s. and describe a PCR-based diagnostic test allowing its detection in the genome of single mosquitoes. Using this test, we found this mutation in six out of seven field samples from West Africa, its frequency being closely correlated with survival to pyrethroid exposure. This diagnostic test should bring major improvement for field monitoring of pyrethroid resistance, within the framework of malaria control programmes.

Alleles↗
PubMed1998

Pyrethroid resistance in Culex quinquefasciatus from west Africa.

Pyrethroid resistance was investigated in thirty-three samples of Culex quinquefasciatus Say from twenty-five cities in Côte d'Ivoire and Burkina Faso. Permethrin resistance ratios at LC50 ranged from 9.5- to 82-fold in Côte d'Ivoire and from 17- to 49-fold in Burkina Faso. For deltamethrin, resistance ratios were lower and ranged from nine to thirty-eight in both countries. A strain was selected with permethrin to investigate resistance mechanisms. After forty-two generations of selection, permethrin resistance level reached 3750-fold, but deltamethrin resistance remained unexpectedly unchanged. This indicated that a specific mechanism was involved in permethrin resistance. Synergist assays and biochemical tests indicated that resistance was partly due to P450-dependent oxidases. A target site insensitivity (kdr) was also involved, associated with DDT cross resistance and a dramatic loss of permethrin knockdown effect on adults. This resistance should be taken into consideration when planning the use of pyrethroid-impregnated materials in urban areas, as Culex is by far the main source of nuisance. Any failure in nuisance control due to resistance is likely to demotivate people in using impregnated materials.

Africa, Western↗
PubMed1998

Origin and prevention of airport malaria in France.

Since 1969, 63 cases of airport malaria have been reported in Western Europe, 24 of which occurred in France. Most were due to Plasmodium falciparum. In 1994, 7 cases occurred in and around Roissy Charles de Gaulle airport (CDG), showing 4 types of contamination: among employees working on airstrips or opening containers, among residents living near the airport, among people living at some distance from the airport after a secondary transport of vectors, and by vectors transported in luggage. In-flight or stop-over infection is not considered as airport malaria. The infective anophelines originated from airports where malaria transmission occurs, mostly in subsaharan Africa. A tentative list is given taking into account aerial traffic with France. Surveys in the airports of Dakar (Senegal), Cotonou (Benin), Abidjan (Cote d'Ivoire) and Yaoundé (Cameroun) found potential vectors in all of these from July to September. After 1994, the Contrôle Sanitaire aux Frontières (CSF) in charge at CDG concentrated its efforts on the flights at risk, as well as information and sensitization of airline companies, which resulted in 73% and 87% of the flights at risk being properly disinsected in 1995 and 1996. Despite pyrethroid resistance in Anopheles gambiae s.s. in West Africa, the efficacy of aircraft spraying with permethrin aerosols is still acceptable. However, surveillance of resistance should be improved and search for nonpyrethroid insecticides suitable for aircraft strongly encouraged.

Africa, Western↗
PubMed1998

Outpatient treatment with subcutaneous interleukin-2 and interferon alfa administration in combination with fluorouracil in patients with metastatic renal cell carcinoma: results of a sequential nonrandomized phase II study. Subcutaneous Administration Propeukin Program Cooperative Group.

PURPOSE: We report the results of the Subcutaneous Administration Propeukin Program (SCAPP) II trial of an outpatient treatment in renal cell carcinoma using interleukin-2 (IL-2) and interferon alfa-2a (IFN-alpha) administered subcutaneously in combination with fluorouracil (5-FU). The objective of this multicenter trial was to confirm that the combination of IL-2, IFN-alpha, and 5-FU leads to a response rate greater than 20%. PATIENTS AND METHODS: Patients with metastatic renal cell carcinoma were included in this study. During the induction phase of the treatment, which lasted 10 weeks, IL-2 and IFN-alpha were administered subcutaneously three times a week for 8 weeks at doses of 18 MIU and 9 MIU, respectively. During these 8 weeks, every Monday, 5-FU was administered at a dose of 750 mg by intravenous infusion over 30 minutes. After evaluation, responding patients or patients with stable disease (SD) were given maintenance treatment, until disease progression (PD) or the appearance of unacceptable toxicity. Each maintenance cycle consisted of a 2-week treatment followed by a three-week rest period. During treatment, IL-2 and IFN-alpha were administered subcutaneously three times a week at doses of 18 MIU and 9 MIU, respectively. Every Monday, 5-FU was administered at a dose of 750 mg by intravenous infusion over 30 minutes. RESULTS: This trial was closed when the sixth sequential analysis showed the lack of benefit from this combination. At the end of the induction period, of 62 patients, 12 (19%; 95% confidence interval [CI], 10% to 31%) reached an objective response, including one complete response (CR), 16 presented with SD, and 27 showed PD. Twenty-seven patients (43%) developed severe toxicity that required reduction of the planned doses (13 patients), delayed treatment (eight patients), or treatment termination (six patients). Seventeen patients were given maintenance treatment. One- and 2-year survival rates were estimated at 55% and 33%, respectively. The 2-year survival rate was 15% in 11 patients who presented with three poor-prognosis factors and 41% in 51 patients who initially presented with no, one, or two poor-prognosis factors (P = .04). CONCLUSION: As in other recently published studies that used 5-FU, IL-2, and IFN-alpha, the multicenter SCAPP II trial in patients with metastatic renal cell carcinoma generated severe toxicity. This sequential trial failed to confirm the favorable results previously obtained by Atzpodien and Sella with this combination of three drugs. Its efficacy, assessed on the response and survival rates, is near to the results observed in programs that used IL-2 alone given subcutaneously.

Adult↗
PubMed1998

[Impact of resistance of Anopheles gambiae s.s. to permethrin and deltamethrin on the efficacy of impregnated mosquito nets].

Trials to assess the impact of resistance of Anopheles gambiae s.s. to permethrin and deltamethrin on the efficacy of insecticide-treated bednets were carried out from October 1997 to April 1998 in six experimental huts at the Yaokoffikro testing station in Côte d'Ivoire. Six polyester bednets were used. Two bednets were treated with permethrin at a dose of 500 mg/m2 and two with deltamethrin at 25 mg/m2. The remaining two untreated bednets served as controls. The number of Anopheles gambiae s.s. entering the hut was reduced 18% with permethrin-treated bednets and 43% with deltamethrin-treated bednets. Threefold fewer female mosquitoes were found under insecticide-treated bednets than under untreated nets (controls). The number of mosquitoes passing through the treated net was threefold lower. The number of mosquitoes exiting from the treated bednets increased twofold. The blood-feeding rate dropped by 55%. Forty percent of mosquitoes entering the permethrin-treated bednets and 56% entering the deltamethrin-treated bednets died. Immediate mortality was always greater (> 85%) than delayed mortality (< 15%). Bioassays confirmed the results from hut experiments. A lower knockdown effect was recorded with permethrin in the resistant strain. Conversely deltamethrin showed the same knockdown effects in the susceptible (Kisumu) and resistant (Yaokoffikro) strain. Mortality rates were low with both permethrin and deltamethrin. This study shows that, even in areas where Anopheles gambiae s.s. is resistant to permethrin and deltamethrin, bednets treated with these insecticides remain effective and can still be considered as an excellent method of personal protection.

Animals↗
PubMed1997

A Bayesian dosing method for carboplatin given by continuous infusion for 120 h.

Carboplatin (CBDCA), an analogue of cisplatin, exhibits reduced toxicity but wide interpatient variability of its pharmacokinetic parameters. Individualization of the CBDCA dose is therefore necessary. Although various formulas have been developed for this purpose, major side effects have been reported on CBDCA administration by short-term infusion (0.5 or 1 h). We therefore propose a new schedule of CBDCA administration. Instead of a dosing method based on the estimation of renal function when a classic administration schedule is used, we propose a pharmacokinetic dosing method (Bayesian method), whereby CBDCA is given by continuous infusion for 120 h. First, CBDCA was given to 21 patients to determine the population pharmacokinetic parameters of carboplatin. Then, on the basis of total platinum plasma concentration measurements and Bayesian estimation of pharmacokinetic parameters, it was possible to individualize the CBDCA dose within the first 24 h of the infusion. This new protocol for CBDCA administration was evaluated in 36 new patients (60 courses). Three theoretical end points at the end of the infusion were considered. For a given theoretical end point, 20 courses were taken into account. The theoretical end points (i.e., 1, 1.5, and 1.8 mg/l) were compared with the concentrations measured at the end of the infusion, which were 0.99 +/- 0.10, 1.41 +/- 0.13, and 1.72 +/- 0.20 mg/l, respectively. This Bayesian dosing method can easily be used in clinical practice, and the determination of predictive performances has shown that the method is precise and unbiased. With no more toxicity or practical difficulties than those produced by other methods, and with acceptable tolerance, it was possible to reach a median dose that was 20% higher than the usual dose (484 +/- 190 mg/m2 as compared with 400 mg/m2). In conclusion, this new schedule of CBDCA administration appears to be interesting in terms of tolerance. However, new studies are required to confirm that this new scheme leads to equal or better efficacy than the classic protocol.

Adult↗
PubMed1997

Distribution of organophosphate and carbamate resistance in Culex pipiens quinquefasciatus (Diptera: Culicidae) in West Africa.

The distribution of organophosphate and carbamate resistance was investigated in 33 samples of Culex pipiens quinquefasciatus Say from 25 cities in Côte d'Ivoire and Burkina Faso. Organophosphate resistance levels were higher in Côte d'Ivoire than in Burkina Faso. Chlorpyrifos resistance ratios at LC95 ranged from 4 to 30 times in Côte d'Ivoire and from 3 to 6 times in Burkina Faso. For temephos, ratios ranged from 3 to 18 and from 1 to 2, respectively. Of 27 samples from Côte d'Ivoire, 25 also displayed cross resistance to carbamates as shown by a mortality plateau in bioassays with propoxur and carbosulfan (similar to chlorpyrifos). Cross resistance to organophosphates and carbamates was caused by an insensitive acetylcholinesterase allele (AceR). This gene was absent from Burkina Faso, except in Niangoloko near the Côte d'Ivoire border. Organophosphate resistance also was associated with the presence of A2-B2 overproduced esterases which had higher frequencies in Côte d'Ivoire (75-100%) than in Burkina Faso (40-50%). Two other esterases with the same electrophoretic mobility as C2 from Puerto Rico and B1 from California were identified for the 1st time in West Africa. "C2" was widespread, whereas "B1" was present in only a few mosquitoes from Côte d'Ivoire. These differences in resistance patterns should be taken into consideration in planning urban mosquito control strategies within 2 countries.

Africa, Western↗
PubMed1997

[Clinical pilot study on repeated use of heparin, vancomycin, colimycine locked flush solution for central intravenous implanted catheter in oncology].

With an anti-infectious and an antithrombotic prophylaxis aims, a locked flush solution including heparin and vancomycin, was used systematically for implantable venous access system for each patient, from january to april 1995. Since the 6th of april 1995, in order to widen the antibiotic spectrum on Gram negative bacteriae, we added colimycin at the flush solution. In 1995, 342 hospitalised patients held this type of venous access and received chemotherapy and/or radiochemotherapy for cancer. Two thousand six hundred thirty three manipulations were done, 575 with the first flush solution, 2058 with the second. During the year, 15 implantable access system (4.4%) were considered as infected, only 3 (0.9%) were removed, in the first period. THe infectious rate seemed to be stable, but the bacterial assessment to be modified between the two periods. The Gram negative bacterial infections seemed to decrease with colimycin addition (33% versus 50%). These results must be confirmed by a long term and/or randomized study.

Anti-Bacterial Agents↗
PubMed1996

Dose-ranging study of riluzole in amyotrophic lateral sclerosis. Amyotrophic Lateral Sclerosis/Riluzole Study Group II.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive disease with no effective treatment. In an initial study, riluzole decreased mortality and slowed muscle-strength deterioration in ALS patients. We have carried out a double-blind, placebo-controlled, multicentre study to confirm those findings and to assess drug efficacy at different doses. METHODS: 959 patients with clinically probable or definite ALS of less than 5 years' duration were randomly assigned treatment with placebo or 50 mg, 100 mg, or 200 mg riluzole daily; randomisation was stratified by centre and site of disease onset (bulbar or limb). The primary outcome was survival without a tracheostomy. Secondary outcomes were rates of change in functional measures (muscle strength, functional status, respiratory function, patient's assessments of fasciculation, cramps, stiffness, and tiredness). The primary analysis was the comparison of the 100 mg dose with placebo by intention-to-treat. Drug-effect on survival was assessed before (log-rank test) and after adjustment for known prognostic factors (Cox's model). FINDINGS: At the end of the study, after median follow-up of 18 months, 122 (50.4%) placebo-treated patients and 134 (56.8%) of those who received 100 mg/day riluzole were alive without tracheostomy (unadjusted risk 0.79, p = 0.076; adjusted risk 0.65, p = 0.002). In the groups receiving 50 mg and 200 mg riluzole daily, 131 (55.3%) and 141 (57.8%) patients were alive without tracheostomy (relative to placebo 50 mg adjusted risk 0.76, p = 0.04; 200 mg 0.61, p = 0.0004). There was a significant inverse dose response in risk of death. No functional scale discriminated between the treatment groups. The most common adverse reactions were asthenia, dizziness, gastrointestinal disorders, and rises in liver enzyme activities; they were commonest with the 200 mg dose. INTERPRETATION: Overall, efficacy and safety results suggest that the 100 mg dose of riluzole has the best benefit-to-risk ratio. This study confirms that riluzole is well tolerated and lengthens survival of patients with ALS.

Amyotrophic Lateral Sclerosis↗
PubMed1996

[Individual dose adjustment of high-dose methotrexate in clinical practice].

Since its discovery in 1948 the clinical applications of methotrexate have widened; and in order to overcome resistances to methotrexate, the concept of high-dose methotrexate has been proposed. The use of rescue by folinic acid, as well as rapid dosage of MTX coupled with pharmacokinetic studies, have permitted us to administer an optimum dose of drug, with maximum therapeutic effects, but with reduced toxicity. Individual adaptation of posology, calculated using the test dose or according to population pharmacokinetic with a Bayesian method of parameter estimation (which allows us to adjust the dose of high-dose methotrexate during its infusion) permits control of inter and intra-individual variations of this drug. After analysis of the different methods proposed, we now present the results of 778 courses of treatment by high-dose methotrexate (while separating 238 courses for osteosarcoma as these formed a homogeneous group of patients). Theoretical maximum concentration and length of infusion were decided by physicians, followed by individual adaptation of posology by pharmacologists at the sixth hour of infusion of methotrexate. This treatment unites maximum security for the patient with no serious side effects (no grade 4 toxicity according to WHO classification), while receiving an optimum dose of methotrexate. In courses of MTX for osteosarcoma, the dose of MTX can be further intensified without risk, by administering on average 65% more than the usual dose in adults (8 g/m2) and 10% more than the usual dose in children (12 g/m2).

Antimetabolites, Antineoplastic↗
PubMed1996

A confirmatory dose-ranging study of riluzole in ALS. ALS/Riluzole Study Group-II.

ALS is a progressive motor neuron disease with no effective treatment. The anti-excitotoxic drug riluzole (100 mg/day) has been shown to decrease mortality and muscular deterioration in ALS patients. To confirm and extend the therapeutic effect of riluzole, we performed a double-blind, placebo-controlled, multicenter, international, dose-ranging (50, 100, 200 mg/day), stratified study in 959 ALS outpatients treated for up to 18 months. Primary efficacy criterion was survival and the effect of treatment was analyzed before (Wilcoxon and log rank tests) and after adjustment on prognostic factors (Cox model). Secondary efficacy criterion was disease progression assessed through change in functional measures. Tracheostomy-free survival rates were: 50.4% (placebo), 55.3% (50 mg riluzole) (p = 0.23, Wilcoxon test; p = 0.25, log-rank test), 56.8% (100 mg riluzole) (p = 0.05, Wilcoxon test; p = 0.076, log-rank test), and 57.8% (200 mg riluzole) (p = 0.061, Wilcoxon test; p = 0.075, log-rank test). At the end of the 18-month study, there was a significant dose-related decrease in risk of death or tracheostomy (p = 0.04). Adjustment for baseline prognostic factors showed a 35% decreased risk of death with the 100-mg dose compared with placebo (p = 0.002). No significant treatment effects were detected for the functional assessments. The most frequent dose-related adverse events included nausea, asthenia, and elevated liver enzyme levels. This study confirms the therapeutic effect of riluzole in a large representative ALS sample, over an 18-month period. Riluzole is well tolerated and decreases the risk of death or tracheostomy in ALS patients.

Amyotrophic Lateral Sclerosis↗
PubMed1995

Drastic reduction of populations of Simulium sirbanum (Diptera: Simuliidae) in central Sierra Leone after 5 years of larviciding operations by the Onchocerciasis Control Programme.

The major vectors of the blinding form of human onchocerciasis in West Africa are two blackfly species, Simulium sirbanum and Simulium damnosum s.s. (Diptera: Simuliidae), identified at the adult stage as the 'savanna group' of the Simulium damnosum complex. In 1988, in the central part of Sierra Leone, the average daily biting rate (females/man/day) by savanna blackflies (mostly S. sirbanum) during the peak of the dry season (April-May) was 59.9, making up 69.1% of total captures on average. There was evidence of a strong long-range immigration of adult females of S. sirbanum through eastern Guinea in the dry season, with a reverse movement towards Guinea in the rainy season. Therefore, in 1989, the World Health Organization's Onchocerciasis Control Programme (OCP) extended its vector control operations from central West Africa to rivers of central and northern Sierra Leone, and to rivers of eastern Guinea. Four years of efficient larviciding drastically reduced adult populations of S. sirbanum in Sierra Leone. In the peak of the dry seasons of 1993 and 1994, the average biting rate by savanna blackflies in central Sierra Leone had dropped to 1.0, making up only 4.3% of total captures on average. Yearly biting rates by S. sirbanum in central Sierra Leone were therefore reduced to 2% of their pre-intervention levels. Based on larval samples, the S. sirbanum has been replaced by two forest species, S. leonense in the south and S. squamosum in the north. Since 1992, it has been possible to calculate accurate transmission rates for blinding onchocerciasis, based on DNA-probe identifications. From 1993, the risk of transmission has not only been reduced by vector control but also by mass distribution of ivermectin to rural communities. In terms of control strategy, the authors conclude that larviciding operations could be alleviated in central Sierra Leone without increasing the risk of blinding onchocerciasis transmission, as long as the migration of S. sirbanum through eastern Guinea and northern Sierra Leone is prevented.

Animals↗