Biomedical subjects

P Carnevale

Publications and source records attributed to P Carnevale.

At least 19 recordsLinked to original sources

PubMed2003

Resistance to carbosulfan in Anopheles gambiae from Ivory Coast, based on reduced sensitivity of acetylcholinesterase.

Resistance to carbosulfan, a carbamate insecticide, was detected in field populations of the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) from two ecologically contrasted localities near Bouaké, Ivory Coast: rural M'bé with predominantly M form of An. gambiae susceptible to pyrethroids; suburban Yaokoffikro with predominantly S form of An. gambiae highly resistant to pyrethroids (96% kdr). The discriminating concentration of 0.4% carbosulfan (i.e. double the LC100) was determined from bioassays with the susceptible An. gambiae Kisumu strain. Following exposure to the diagnostic dosage (0.4% carbosulfan for 1 h), mortality rates of female An. gambiae adults (reared from larvae collected from ricefields) were 62% and 29% of those from M'bé and Yaokoffikro, respectively, 24 h post-exposure. Exposure for 3 min to netting impregnated with the operational dosage of carbosulfan 200 mg/m2 gave mortality rates of 88% of those from M'bé and only 12.2% for Yaokoffikro. In each case the control untreated mortality rate was insignificant. Biochemical assays to detect possible resistance mechanism(s) revealed the presence of insensitive AChE in populations of An. gambiae at both localities, more prevalent in the S form at Yaokoffikro than in M form at M'bé, as expected from bioassays results. Our study demonstrates the need to monitor carbamate resistance among populations of the An. gambiae complex in Africa, to determine its spread and anticipate vector control failure if these insecticides are employed.

Acetylcholinesterase↗

PubMed2003

First report of the oriental mosquito Aedes albopictus on the West African island of Bioko, Equatorial Guinea.

The invasive oriental mosquito Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) was detected on Bioko Island for the first time in November 2001. It was found to be well established breeding in artificial containers at Planta, near Malabo, the capital of Equatorial Guinea. Associated species of mosquito larvae were Aedes aegypti (L.), Ae. africanus (Theobald), Culex near decens Theobald, Cx. duttoni Theobald, Cx. quinquefasciatus Say, Cx. tigripes De Grandpré & De Charmoy, Eretmapodites quinquevittatus Theobald and Mansonia africana (Theobald). This is the third tropical African country to be invaded by Ae. albopictus, which has recently spread to many parts of the Americas and Europe--with vector competence for dengue, yellow fever and other arboviruses. In the Afrotropical environment, it will be interesting to monitor the ecological balance and/or displacement between introduced Ae. albopictus and indigenous Ae. aegpyti (domestic, peri-domestic and sylvatic populations).

Aedes↗

PubMed2003

Inland valley rice production systems and malaria infection and disease in the savannah of Côte d'Ivoire.

In sub-Saharan Africa, lowlands developed for rice cultivation favour the development of Anopheles gambiae s. l. populations. However, the epidemiological impact is not clearly determined. The importance of malaria was compared in terms of prevalence and parasite density of infections as well as in terms of disease incidence between three agroecosystems: (i) uncultivated lowlands, 'R0', (ii) lowlands with one annual rice cultivation in the rainy season, 'R1' and (iii) developed lowlands with two annual rice cultivation cycles, 'R2'. We clinically monitored 2000 people of all age groups, selected randomly in each agroecosystem, for 40 days (in eight periods of five consecutive days scheduled every 6 weeks for 1 year). During each survey, a systematic blood sample was taken from every sick and asymptomatic person. The three agroecosystems presented a high endemic situation with a malaria transmission rate of 139-158 infective bites per person per year. The age-standardized annual malaria incidence reached 0.9 malaria episodes per person in R0, 0.6 in R1 and 0.8 in R2. Children from 0 to 9-year-old in R0 and R2 had two malarial attacks annually, but this was less in R1 (1.4 malaria episodes per child per year). Malaria incidence varied with season and agroecosystem. In parallel with transmission, a high malaria risk occurs temporarily at the beginning of the dry season in R2, but not in R0 and R1. Development of areas for rice cultivation does not modify the annual incidence of malarial attacks despite their seasonal influence on malaria risk. However, the lower malaria morbidity rate in R1 could be explained by socio-economic and cultural factors.

Adolescent↗

PubMed2002

Stable chromosomal inversion polymorphisms and insecticide resistance in the malaria vector mosquito Anopheles gambiae (Diptera: Culicidae).

Anopheles gambiae Giles has been implicated as a major vector of malaria in Africa. A number of paracentric chromosomal inversions have been observed as polymorphisms in wild and laboratory populations of this species. These polymorphisms have been used to demonstrate the existence of five reproductive units in West African populations that are currently described as incipient species. They have also been correlated with various behavioral characteristics such as adaptation to aridity and feeding preference and have been associated with insecticide resistance. Two paracentric inversions namely 2La and 2Rb are highly ubiquitous in the wild and laboratory populations sampled. Both inversions are easily conserved during laboratory colonization of wild material and one shows significant positive heterosis with respect to Hardy-Weinberg proportions. Inversion 2La has previously been associated with dieldrin resistance and inversion 2Rb shows an association with DDT resistance based on this study. The stability and maintenance of these inversions as polymorphisms provides an explanation for the transmission and continued presence of DDT and dieldrin resistance in a laboratory strain of An. gambiae in the absence of insecticide selection pressure. This effect may also be operational in wild populations. Stable inversion polymorphism also provides a possible mechanism for the continual inheritance of suitable genetic factors that otherwise compromise the fitness of genetically modified malaria vector mosquitoes.

Animals↗

PubMed2002

[Dynamics of malaria transmission in Kafiné, a rice growing village in a humid savannah area of Côte d'Ivoire].

A study on malaria transmission based on samples of mosquitoes caught on human subjects was conducted from February to August 1995 in the rice growing area of Kafine, a village located in the Niakaramandougou district of northern Côte d'Ivoire. The village is surrounded by 117,500 acres of rice fields. Irrigation is sub-permanent in the rice field and harvests number two a year. During the 6 months of the study, 12.353 mosquitoes were caught. The average biting rate was 118.8 bites per man per night (b/m/n). Mansonia, Culex and Aedes represented only 17.5% of the total number of mosquitoes caught. Anopheles accounted for 82.5% of the number of anthropophilic mosquitoes. Anopheles gambiae s.s. represented 83.7% of the total Anopheles species. As a whole, the average biting rate recorded for the Anopheles was 98 b/m/n. The average biting rate of An. gambiae was 90.4 b/m/n. The highest rate (121.5 b/m/n) was recorded in April. During the dry and rainy season, the indoor biting cycle per hour of An. gambiae s.s. was studied from 6 p.m. to 6 a.m. In both seasons, a marked biting activity was noticed between 10 p.m. and 5 a.m. The average annual parity rate reached 40.2% but it ranged from 59.8% (n = 82) in February to 19% (n = 63) in May. The mean sporozoitic index of An. gambiae throughout the study period was 1.1% (14 positive salivary glands/1.251 dissected). The index ranged from 0 in April, May and June to 6.2 (n = 192) in July. The rate did not vary with rainfall but with the different stages of rice growing. The non-synchronisation of agricultural practises for each growing cycle seemed to be a conclusive factor in the transmission of malaria in this locality. Malaria transmission at Kafine can be characterised by 3 main elements: transmission is intensive with an estimated inoculation rate of 1 ib/m/n; transmission is more related to double phase rice cultivation (regardless of synchronisation on plots) than to rainfall; transmission shows particular variations linked to rice cultivation cycles with an increase during periods of ripeness and harvest. The nuisance caused by higher mosquito density has brought people to comply with use of pyrethroid impregnated bed nets advocated for wide use by the National Malaria Control Program.

Aedes↗

PubMed2002

[The epidemiology of malaria in the southwestern forests of the Ivory Coast (Tai region)].

An epidemiological study on malaria was undertaken between July 1995 and July 1996 in two villages (Zaïpobly and Gahably) and their encampments (Kouassikro, Hamanikro and Konankro), in the south-western forest area of Côte d'Ivoire (region of Taï). The parasitological scheme comprised a total of 2023 tests performed on children aged from 0 to 14 years. The species found were Plasmodium falciparum, P. malariae and P. ovale with a proportion of 84%, 14% and 2% respectively. The global parasite prevalence of all Plasmodium species was 85% and malaria was holoendemic. The average parasitic density decreased progressively as the age increased, in contrast to the plasmodic index which did not vary. All the malarial indexes were similar in the villages and their encampments. Only overall fever prevalence was permanent and in all age groups it was higher in the encampments than in the villages. The entomological findings showed that transmission was permanent and intense throughout the year, with a recrudescence during the rainy season. Transmission was attributed to Anopheles gambiae s.l. in 85% of the cases whereas An. funestus played a secondary role. The average sporozoïtic index was 7.6% and varied between 1.1% and 16.7%. The entomological inoculation rate was of 400 infected bites per person-year for An. gambiae s.l. In such conditions of intense transmission, acquisition of premunition starts at a very early age. This assertion is verified by the average parasite density and the frequency of high parasitic densities which were at their maximum between 1 and 4 years of age and decreased thereafter as the age increased. The paludometric and entomologic indexes obtained are the most elevated ever to have been observed in Côte d'Ivoire, as a result of considerable ecological changes linked to the deterioration of the forest environment over the past 30 years. This deterioration has probably been caused by demographic pressure resulting from internal and foreign immigration to the Taï region and more especially by the influx of Liberian refugees.

Adolescent↗

PubMed2002

[An experimental tool essential for the evaluation of insecticides: the testing huts].

The following study analyses the potentialities of the experimental huts built in M'be Valley (Côte d'Ivoire) where the evaluations of the insecticide products have been carried out for many years in line with the WHOPES protocol on the methodology of stage 2 assays. Starting a testing station first requires a good knowledge of the sensitivity of Anopheles gambiae to the main insecticide families. Then thanks to the experimental huts the efficacy of the various means of treatment can be compared with the one in untreated huts; this study focuses on house spraying using 100 mg a.i./m2 and bednets impregnated with lambda-cyhalothrin at a dose of 15 mg a.i./m2. The fipronil used in house spraying doesn't show any repellent effect, however it does have an irritating effect that increases the natural exophily of An. gambiae females entering the testing huts. The blood-feeding rate recorded in the treated huts was reduced to 24% and to 38% mortality rate consisting mainly of a 24 hours delayed mortality. The bednets treated with lambda-cyhalothrin have greatly reduced the contact between man and vector since the entry rate of An. gambiae females was cut down by 68% compared to the control. The exophily of this anopheles was twofold greater with the impregnated bednets and the blood-feeding rate reduced to 47%. Finally the global mortality rate, two thirds of immediate mortality, one third of delayed mortality, reached 35%. The experimental huts in the M'be Valley therefore provide essential information regarding the selection of the most efficacious insecticides against An. gambiae. This experimental method must be extended to other sites in order to finalize ever more selective and appropriate means of control against nuisance and disease-vector mosquitoes.

Animals↗

PubMed2001

Olyset Net efficacy against pyrethroid-resistant Anopheles gambiae and Culex quinquefasciatus after 3 years' field use in C te d'Ivoire.

Pyrethroid-impregnated bednets are advocated for personal protection against malaria vectors. To avoid the need for periodic re-treatment, it would be advantageous to have nets that retain insecticidal efficacy for years and withstand repeated washing. Such a type of commercially produced bednet with permethrin 2% incorporated in polyethylene fibres (trademark Olyset Net supplied by Sumika Life-Tech Co., Osaka, Japan) was evaluated against mosquitoes in veranda-trap huts at Yaokoffikro, near Bouaké, C te d'Ivoire, by standard WHOPES phase II procedures. Four Olyset Nets were compared with a standard untreated polyester net as control. They comprised three examples previously used in a village for over 3 years (one washed, one dirty, one very dirty) and a previously unused Olyset Net, newly unwrapped, from the same original batch. Bioassays with 3 min exposure of susceptible Anopheles gambiae Giles (Diptera: Culicidae) gave >99% mortality of female mosquitoes tested on the 'new' Olyset Net. The used Olyset Nets gave mortality rates averaging 83% for the washed net, 85% for the dirty net and 55% for the very dirty net (within 24-h following 3 min exposure). Thus, Olyset Nets were found to remain remarkably effective against susceptible An. gambiae for at least 3 years under field conditions. Wild pyrethroid-resistant populations of Culex quinquefasciatus Say and An. gambiae (savanna cytotype with 96% kdr) were assessed during June-August 1999 for their responses to sleepers protected by nets in the experimental huts. With regard to hut entry by foraging female mosquitoes, Olyset Nets showed some deterrency against An. gambiae (44% reduction by the new net, approximately 20% by the dirty nets, none by the washed net), but not against Cx. quinquefasciatus. Among mosquitoes entering the hut with untreated control net, 30-34% tried to leave (exophily) but were caught in the verandah trap. The permethrin repellency of Olyset Nets increased exophily by 19% for An. gambiae and 14% for Cx. quinquefasciatus. Blood-feeding rates were 16% An. gambiae and 35% Cx. quinquefasciatus in the hut with sleeper under the untreated net (showing considerable prevention of biting), 22-26% of both species in huts with washed or dirty used Olyset Nets (not significantly different from control), while the biting success rate of Cx. quinquefasciatus (but not kdr An. gambiae) was more than halved by the 'new' Olyset Net. Mortality rates of pyrethroid-resistant An. gambiae and Cx. quinquefasciatus from the huts were, respectively, 3% and 8% with the untreated polyester net, 27.5% and 17% with the 'new' Olyset, 15% and 17.5% with the washed Olyset, 16-25% and 17-20% with dirty old Olyset Nets. Kill differences between nets are significantly different for both An. gambiae and Cx. quinquefasciatus. Unfortunately the washed used Olyset Net showed least activity against resistant mosquitoes, despite its greatest activity against susceptible An. gambiae. In each case there was evidence that a high proportion of mosquitoes failed to feed through the net (many of them dying from starvation when they could not leave the closed hut), with indications that dirty Olyset nets enhanced this protective value.

Animals↗

PubMed2001

Combined pyrethroid and carbamate 'two-in-one' treated mosquito nets: field efficacy against pyrethroid-resistant Anopheles gambiae and Culex quinquefasciatus.

A new approach is proposed in the treatment of mosquito nets, using a 'two-in-one' combination of pyrethroid and non-pyrethroid insecticides applied to different parts of bednets. The objectives are mainly to overcome certain limitations of pyrethroid-impregnated bednets currently recommended for malaria control purposes. Apart from developing alternatives to pyrethroid dependency, we sought to counteract pyrethroid irritant effects on mosquitoes (excito-repellency) and resistance to pyrethroids. The idea takes advantage of the presumed host-seeking behaviour of mosquitoes confronted by a net draped over a bed, whereby the mosquito may explore the net from the top downwards. Thus, nets could be more effective if treated on the upper part with residual non-irritant insecticide (carbamate or organophosphate) and with a pyrethroid on the lower part. Sequential exposure to different insecticides with distinct modes of action is equivalent to the use of a mixture as a potential method of managing insecticide resistance. We also intended to improve the control of nuisance mosquitoes, especially Culex quinquefasciatus Say (Diptera: Culicidae) that often survive pyrethroids, in order to encourage public compliance with use of insecticide-treated nets (ITNs). Polyester bednets were pretreated with residual pyrethroid (bifenthrin 50 mg/m2 or deltamethrin 25 mg/m2) on the lower half and with carbamate (carbosulfan 300 mg/m2) on the upper half to minimize contact with net users. Unreplicated examples of these 'two-in-one' treated nets were field-tested against wild mosquitoes, in comparison with an untreated net and bednets treated with each insecticide alone, including PermaNet wash-resistant formulation of deltamethrin 50 mg/m2. Overnight tests involved volunteers sleeping under the experimental bednets in verandah-trap huts at Yaokofikro, near Bouaké in C te d'Ivoire, where the main malaria vector Anopheles gambiae Giles, as well as Culex quinquefasciatus Say, are highly resistant to pyrethroids. Efficacy of these ITNs was assessed in the huts by four entomological criteria: deterrency and induced exophily (effects on hut entry and exit), blood-feeding and mortality rates (immediate and delayed). Overall, the best impact was achieved by the bednet treated with carbosulfan alone, followed by 'two-in-one' treatments with carbosulfan plus pyrethroid. Blood-feeding rates were 13% An. gambiae and 17% Cx. quinquefasciatus in huts with untreated nets, but only 3% with carbosulfan ITNs, 7-11% with combined ITN treatment, 6-8% An. gambiae and 12-14% Cx. quinquefasciatus with pyrethroid alone. Mosquitoes that entered the huts were killed sooner by nets with combined treatment than by pyrethroid alone. Mortality-rates in response to ITNs with carbosulfan (alone or combined with pyrethroid) were significantly greater for Cx. quinquefasciatus, but not for An. gambiae, compared to ITNs with only pyrethroid. About 20% of sleepers reported potential side-effects (headache and/or sneezing) from use of ITN treated with carbosulfan alone. Further development of this new 'two-in-one' ITN concept requires a range of investigations (choice of effective products, cost-benefit analysis, safety, etc.) leading to factory production of wash-resistant insecticidal nets treated with complementary insecticides.

Animals↗

PubMed2001

[Investigation surrounding a fatal case of yellow fever in Côte d'Ivoire in 1999].

Côte d'Ivoire is an endemic country for yellow fever, but no case was officially notified in recent years. In July 1999, however, one fatal case was reported. A German citizen was infected in the national park of Comoe, in the north eastern area of the country. In order to evaluate the extent of amaril virus circulation and the risk for local people, a virological, entomological and epidemiological investigation was carried out by the ministry of health, the OCCGE, the Côte d'Ivoire Pasteur Institute (IPCI) and the World Health Organisation in the area where the fatal case had been staying. 18 suspected and 24 confirmed mosquito catchers were identified by interview and a blood specimen was collected from each of them. In addition, 159 batches of mosquitoes from which 94 batches of potential vectors were collected; among the suspected cases, 22% were immunised against yellow fever. Serological and virological analyses were made at IPCI and the Paris Pasteur Institute by ELISA technique and isolation on cells cultures and newborn mice. All the suspicious sera and 87.5% of the catchers were positive for IgG anti-amaril virus. One catcher's serum was positive for IgM anti-amaril virus. 11 suspected sera were positive for IgG anti-dengue virus with 1 positive for IgM. 1 strain of amaril virus and 3 strains of Zika virus were isolated from mosquitoes at IPCI and confirmed by CRORA in Dakar. These results indicated that there is a yellow fever and dengue virus are prevalent among the human and vector populations in the study area. Preventive measures must be adopted to protect human beings at risk for amaril infection.

Adolescent↗

PubMed2001

[Antimalarial guidelines and therapy practices of the population of Bouake, Ivory Coast].

This survey of 162 households in the city of Bouaké, Côte d'Ivoire was undertaken to study the behavior of the population in diagnosing and treating malaria. Findings indicate that awareness of symptoms and ability to evaluate the severity of malaria is high. In most cases, mild malaria is treated at home. In case of presumptive diagnosis of malaria, 87.6% of households undertake self-treatment, 9.3% seek institutional healthcare, 1.2% go to traditional healers, and 1.9% use traditional remedies. The most frequent drug for primary treatment is chloroquine (68.3%) which is generally obtained from pharmacies (98.8%). However, proper dosages are rarely used. If primary treatment fails, behavior is complex depending on the estimated severity of disease. Although many causes of malaria are mentioned, most people implicate mosquitoes (75.6%). In 95.1% of households surveyed, chloroquine prophylaxis was used for newborns. Most households (89.5%) practice mosquito bite protection but use of mosquito nets is low (4.9%). These results showing the preference for family-based management suggest that informational campaigns are needed to promote effective and consistent home treatment. Education is also needed to increase knowledge about mosquito nets and insecticides.

Adult↗

PubMed2000

Experimental and molecular genetic analysis of the impact of pyrethroid and non-pyrethroid insecticide impregnated bednets for mosquito control in an area of pyrethroid resistance.

Experimental huts in Côte d'Ivoire were used to evaluate the pyrethroid alpha-cypermethrin, the non-ester pyrethroid etofenprox, the organophosphate pirimiphos-methyl and the carbamate carbosulfan on bednets against pyrethroid-resistant Anopheles gambiae Giles. To test for selection for the resistance gene by the treated nets, A. gambiae collected live or dead from the huts were kept and analysed for the presence of the kdr gene using a new polymerase chain reaction followed by sequence-specific oligonucleotide probing (PCR-SSOP) for kdr-genotyping. Deliberately holed bednets freshly treated with pirimiphos-methyl or carbosulfan caused over 90% kill of A. gambiae s.s. and Culex spp. However, the mortality with alpha-cypermethrin or etofenprox treated nets was similar to that with untreated nets. Bloodfeeding of A. gambiae s.s. on the sleepers under the nets was only significantly reduced by alpha-cypermethrin and carbosulfan. Tests of the residual activity of the bednets after seven months showed that pirimiphos-methyl had lost its efficacy while carbosulfan still performed well. Once again the pyrethroid treated nets gave similar results to the untreated nets. Selection for the kdr-allele by alpha-cypermethrin and etofenprox, but not by carbosulfan, was indicated by PCR-SSOP genotyping of mosquitoes. Thus carbamates such as carbosulfan, or organophosphates of longer persistence than pirimiphos-methyl and of low mammalian toxicity, would seem to be a promising alternative to be used on bednets, particularly in areas of pyrethroid resistance.

Adult↗

PubMed2000

Modifications of pyrethroid effects associated with kdr mutation in Anopheles gambiae.

Effects of knockdown resistance (kdr) were investigated in three pyrethroid-resistant (RR) strains of the Afrotropical mosquito Anopheles gambiae Giles (Diptera: Culicidae): Kou from Burkina Faso, Tola and Yao from Côte d'Ivoire; compared with a standard susceptible (SS) strain from Kisumu, Kenya. The kdr factor was incompletely recessive, conferring 43-fold resistance ratio at LD50 level and 29-fold at LD95 level, as determined by topical application tests with Kou strain. When adult mosquitoes were exposed to 0.25% permethrin-impregnated papers, the 50% and 95% knockdown times (KdT) were 23 and 42 min for SS females, compared with 40 and 62 min for RS (F1 Kou x Kisumu) females. On 1% permethrin the KdT50 and KdT95 were 11 and 21 min for SS compared with 18 and 33 min for RS females. Following 1 h exposure to permethrin (0.25% or 1%), no significant knockdown of Kou RR females occurred within 24 h. Permethrin irritancy to An. gambiae was assessed by comparing 'time to first take-off' (TO) for females. The standard TO50 and TO95 values for Kisumu SS on untreated paper were 58 and 1044 s, respectively, vs. 3.7 and 16.5 s on 1% permethrin. For Kou RR females the comparable values were 27.3 s for TO50 and 294 s for TO95, with intermediate RS values of 10.1 s for TO50 and 71.9 s for TO95. Thus, TO values for RS were 2.7-4.4 times more than for SS, and those for RR were 7-18 times longer than for SS. Experiments with pyrethroid-impregnated nets were designed to induce hungry female mosquitoes to pass through holes cut in the netting. Laboratory 'tunnel tests' used a bait guinea-pig to attract mosquitoes through circular holes (5 x 1 cm) in a net screen. With untreated netting, 75-83% of laboratory-reared females passed through the holes overnight, 63-69% blood-fed successfully and 9-17% died, with no significant differences between SS and RR genotypes. When the netting was treated with permethrin 250mg ai/m2 the proportions that passed through the holes overnight were only 10% of SS vs. 40-46% of RR (Tola & Kou); mortality rates were 100% of SS compared with 59-82% of RR; bloodmeals were obtained by 9% of Kou RR and 17% of Tola RR, but none of the Kisumu SS females. When the net was treated with deltamethrin 25 mg ai/m2 the proportions of An. gambiae that went through the holes and blood-fed successfully were 3.9% of Kisumu SS and 3.5% of Yaokoffikro field population (94% R). Mortality rates were 97% of Kisumu SS vs. 47% of Yaokoffikro R. Evidently this deltamethrin treatment was sufficient to kill nearly all SS and half of the Yaokoffikro R An. gambiae population despite its high kdr frequency. Experimental huts at Yaokoffikro were used for overnight evaluation of bednets against An. gambiae females. The huts were sealed to prevent egress of mosquitoes released at 20.00 hours and collected at 05.00 hours. Each net was perforated with 225 square holes (2 x 2 cm). A man slept under the net as bait. With untreated nets, only 4-6% of mosquitoes died overnight and bloodmeals were taken by 17% of SS vs. 29% of Yaokoffikro R (P<0.05). Nets treated with permethrin 500 mg/m2 caused mortality rates of 95% Kisumu SS and 45% Yao R (P<0.001) and blood-feeding rates were reduced to 1.3% of SS vs. 8.1% of Yao R (P<0.05). Nets treated with deltamethrin 25 mg/m2 caused mortality rates of 91% Kisumu SS and 54% Yao R (P<0.001) and reduced blood-feeding rates to zero for SS vs. 2.5% for Yao R (P>0.05). (ABSTRACT TRUNCATED)

Animals↗

PubMed2000

[Impact of pyrethrin resistance on the efficacity of impregnated mosquito nets in the prevention of malaria: results of tests in experimental cases with deltamethrin SC].

The effects of impregnated bednets treated with deltamethrin at a dosage of 25 mg a.i./m2 were evaluated at two testing stations in Côte d'Ivoire. The first one was located in Yaokoffikro, where Anopheles gambiae s.s. are resistant to pyrethroids (including deltamethrin), and the second in M'be, close to a large rice-growing area where An. gambiae s.s. are susceptible pyrethroids. In both situations, treating bednets with deltamethrin was very effective in limiting contact between man and vector. 72% fewer female An. gambiae entered the huts in the susceptible area, whereas a decrease of 43% was recorded in the resistant area, indicating that deltamethrin still has a certain repellent effect on resistant populations of An. gambiae s.s. Overall mortality induced by bednets treated with insecticide was significantly higher in the resistant area (56.4% as versus 44.3%). An explanation for this apparent paradox is that the mosquitoes being less repelled by the insecticide remain on the treated material for longer periods of time and most of them eventually die. The results of this study indicate that bednets treated with deltamethrin are an effective prophylactic measure even in areas where An. gambiae s.s. are resistant to pyrethroids and should still be considered as a practical means of personal protection against malaria even in pyrethroid resistance areas with high frequency of kdr resistance genes.

Animals↗

PubMed1999

Imaging Trypanosoma cruzi within tissues from chagasic patients using confocal microscopy with monoclonal antibodies.

Confocal fluorescence microscopy combined with differential interference contrast imaging of tissues from chagasic patients enabled the unequivocal identification of the parasite Trypanosoma cruzi. Using different monoclonal antibodies that indicate the parasite form and replication stage in conjunction with DNA labelling, specimens derived from distinct clinical forms of the disease were examined. Intracellular amastigote forms of the parasite were clearly detected in heart, brain, skin, lung, and kidney. Dividing amastigotes as well as trypomastigote forms were recognized in samples obtained from patients undergoing either acute-phase or some form of reactivation caused by immunosuppression.

Adult↗

PubMed1999

[Laboratory evaluation of alpha-cypermethrin insecticide efficacy on Anopheles gambiae populations of Côte d'Ivoire resistant to permethrin and deltamethrin].

Susceptibility tests were carried out in laboratory conditions to evaluate the efficacy of alpha-cypermethrin (a synthetic pyrethroid never used in Côte d'Ivoire) for malaria vector control. Five wild populations of Anopheles gambiae originating from M'bé, Yaokoffikro, Korhogo, Kafiné and Daola and two laboratory reared strains (Kisumu susceptible and Kou permethrin resistant selected strain) were tested. The diagnostic dosage of alpha-cypermethrin for the sensitive strain Kisumu was 2.5 x 10(-3)%. A comparative study of the susceptibility of samples of wild populations of An. gambiae was carried out according to the WHO standard susceptibility test. Impregnated papers with 4% DDT, 0.25% permethrin, 0.025% deltamethrin and 0.0025% alpha-cypermethrin were used. The results showed that except for mosquitoes from M'bé, all the other populations were resistant to these insecticides. Bioassays were carried out with alpha-cypermethrin at the operational dosage of 20 mg a.i./m2 on the same population and laboratory reared strains. The results showed the efficacy of this insecticide on both the Kisumu strain and the population from M'bé, a maintained efficacy for the Daloa, Kafiné and Korhogo mosquito populations, but the wild anopheline population from Yaokoffikro clearly appeared fully resistant.

Animals↗

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

[ The aggressive cycle of Anopheles gambiae s.s. inside houses and malaria transmission in the Bouake region (Côte d'Ivoire). Value of using impregnated mosquito nets].

The biting indoor cycle of Anopheles gambiae s.s. was studied in a rural zone near Bouaké from 6 pm to 6 am. The cycle was characterized by a peak between midnight and 1 am (n = 19,181). The parturity rate of biting females regularly increased from 6 pm until 3 am, then remained at a high level up to 6 am (n = 14,239). Infected bites were observed from 7 pm to 6 am with a maximum between 0 and 3 am, and 96.7% of them were obtained between 11 pm and 4 am (n = 219). It appears that malaria transmission occurs essentially at the moment when villagers are in bed. The correct use of impregnated bed nets may thus greatly reduce malaria transmission.

Animals↗