Insecticide resistance in stable flies (Stomoxys calcitrans) on dairy farms in Germany.

Stable flies (Stomoxys calcitrans Linnaeus, 1758) can have a considerable negative impact on animal well-being, health, and productivity. Since insecticides constitute the mainstay for their control, this study aimed at assessing the occurrence of insecticide resistance in S. calcitrans on dairy farms in Brandenburg, Germany. First, the susceptibility of stable flies from 40 dairy farms to a deltamethrin-impregnated fabric was evaluated using the FlyBox® field test method. Then, S. calcitrans strains from 10 farms were reared in the laboratory, and the offspring was tested against the adulticides deltamethrin and azamethiphos and the larvicides cyromazine and pyriproxyfen. The FlyBox® method indicated 100% resistance in stable flies against deltamethrin. Later, to the offspring of those 10 established laboratory strains previously caught on suspected dairy farms, these field findings could be confirmed with mortalities well below 90% 24 h following topical application of the calculated LD95 of deltamethrin and azamethiphos. The ten strains could therefore be classified as resistant to the tested insecticides. In contrast, exposure to the insect growth regulators cyromazine and pyriproxyfen at their recommended concentrations demonstrated 100% efficacy. Both larvicides inhibited the moulting process of the stable fly larval stages completely, showing that the stable fly strains tested were susceptible to them. The intensive use of insecticides in recent decades has probably promoted the development of insecticide resistance. Systematic surveys in different livestock production systems and vigilance are therefore deemed necessary for estimating the risk of insecticide resistance development on a nationwide scale.

The impact of insecticide-treated material to reduce flies among pork outlets in Kampala, Uganda.

Synanthropic flies have adapted to the mass of decaying organic matter near human settlements. As such, they feed and breed on food, faeces and other organic material and are known vectors for various diseases. Many of these diseases are associated with food, and foodborne diseases are of growing concern in developing countries where human population and food consumption increase. This pilot study aims at investigating the impact of a novel application of insecticide-treated material (ZeroFly®) to reduce flies among pork outlets in Kampala, Uganda. A cross-sectional survey randomly selected 60 of 179 pork outlets in Kampala. A controlled longitudinal trial followed in which 23 out of the 60 pork outlets were recruited for an intervention with insecticide-treated material. The pork outlets were randomly allocated to a group of 18 netted pork outlets (intervention) and five non-netted pork outlets (control). Monitoring took place over 15 weeks including 2 weeks as the baseline survey. The units were monitored for fly abundance using non-attractant sticky traps, which were placed within the pork outlet once per week for 48 consecutive hours. Medians of fly numbers before and after the intervention indicated a decrease of fly numbers of 48% (p = 0.002). Fly bioassays showed that the insecticidal activity of the netting remained active over the entire intervention period and led to a total paralysis of flies within at least 6 h after exposure. Insecticide-treated material provides a practical and sustainable solution in controlling flies and is therefore recommended as a complementary strategy for an integrated vector control and hygiene management.

Field trials assessing deltamethrin (Butox®) treatments of sheep against Culicoides species.

Culicoides (Diptera: Ceratopogonidae) biting midges may transmit various diseases of economic importance, including bluetongue virus (BTV) and Schmallenberg (SV) virus, which affect ruminants. During the outbreak of BTV in central and northern Europe in 2006, and in the absence of BTV vaccines, many national veterinary services recommended the treatment of susceptible livestock with pyrethroids as a first-line defense against biting midges, although these insecticides were officially not registered and authorized for use against Culicoides midges. The efficacy of Butox® pour on (7.5 mg deltamethrin/mL) against biting midges was therefore evaluated in a double-blinded GCP field trial performed in Brandenburg, Germany. Forty female Merino sheep with an average body weight of 38 kg (±7 kg) were used for the study. Twenty randomly selected sheep were treated with 10 mL Butox® pour on. The remaining 20 sheep were left untreated and served as a control group. Midge collections took place in two separate drop traps covering two crush pens with three confined treated/untreated sheep standing inside, on weekdays at 1, 7, 14, 21, 28, and 35 days post treatment. A total of 19,057 midges were collected during this period. Midges were identified as belonging to the subgenus Avaritia, Fox (84.6%) and subgenus Culicoides, Latreille (15.4%). A total of 12,031 midges were collected inside the drop trap containing untreated sheep, in comparison to 7,026 midges collected from the vicinity of the treated sheep. Significantly, more midges had fed on control compared to treated sheep with 757 and 103 engorged midges, respectively. The results indicate that treatment of sheep with Butox® pour on provided a significant decrease in Culicoides feeding rates under field conditions for at least 35 days.

Analysis of Glossina palpalis gambiensis and Glossina tachinoides from two distant locations in Burkina Faso using MALDI TOF MS.

Riverine tsetse (Glossina) as Glossina palpalis gambiensis Vanderplank 1949 and Glossina tachinoides Westwood 1850 are the main vectors for African animal trypanosomoses in Burkina Faso. Vector control has been proven efficient in disease containment, but its success is endangered by the reinvasion of tsetse from neighbouring areas. Thus, identifying relic populations can enhance the success rate of vector control efforts. This is currently carried out through microsatellite analysis which is time-consuming and costly. Recently, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry-based analysis has become a routine method in microbial species identification. Owing to the rapidness and cost-effectiveness, this approach has been extended towards species identification of higher organisms such as tsetse. Following the recent experiences in distinguishing two genotypes of Prototheca spp., it is of interest to explore the validity of mass spectrometry for tsetse population differentiation. As a preliminary test, we submitted male and female G. palpalis gambiensis and G. tachinoides from Sideradougou and Folonzo, Burkina Faso (distance 60 km) to matrix-assisted laser desorption/ionisation analysis. The wing samples were utilized for protein extraction and mass spectra in a broad mass to charge ratio (2,000-20,000 kDa) were obtained. Specific peaks appeared to represent species, sex and location. Then, a peak list was extracted, containing the peaks in mass-to-charge ratio by revealing their intensities as well. These lists were used to compute a spectral dendrogram and a principle component analysis which displayed the differences among the samples from the two different regions. The results indicate that this technique can be extended with additional tsetse species, ideally with supporting genomic data, to later assist in designing rational vector control strategies.

Protection of confined cattle against biting and nuisance flies (Muscidae: Diptera) with insecticide-treated nets in the Ghanaian forest zone at Kumasi.

Insecticide-treated nets for the protection of cattle against Muscinae and Stomoxyinae were evaluated using four identical pens in Kumasi, Ghana, 2005. Two pens served as controls: pen A as negative control and pen C as a positive control containing two zebus and no netting protection. Pens B and D had two zebus each: B was protected with an untreated net (1 m height) while D had the same but deltamethrin-treated net with a persistency attaining 9 months. Nuisance fly densities were weekly monitored using mono-conical traps outside each pen at distances of 20-30 m. No Glossinidae were detected in an otherwise suitable habitat and fewer than ten Tabanidae per catch were recorded. Insect attacks were counted twice per week with photos of selected body regions. Video footages of each animal allowed recordings of defensive movements during 30 s. For the first 3 weeks, mean outside catches were highest around B and C with, respectively, 9.0 and 8.0 insects per trap per day compared with catches outside A and D with 1.8 and 3.3 insects. Catches increased sharply around pens B and C with, respectively, 155.7 and 172.8 insects during week 4 and following, while outside pens A and D significantly fewer insects (11.8 and 7.3) were caught. Pictures of selected body regions showed significantly fewer attacking insects inside pen D, leading to significant nuisance reductions. Feed-uptake and resting was undisturbed, contrasting with relentless disturbance of animals in pens B and C. Protecting confined cattle with a treated net prevented attacks by nuisance insects and reduced their densities.

Monitoring of putative vectors of bluetongue virus serotype 8, Germany.

To identify the vectors of bluetongue virus (BTV) in Germany, we monitored Culicoides spp. biting midges during April 2007-May 2008. Molecular characterization of batches of midges that tested positive for BTV suggests C. obsoletus sensu stricto as a relevant vector of bluetongue disease in central Europe.

PCR identification of Culicoides dewulfi midges (Diptera: Ceratopogonidae), potential vectors of bluetongue in Germany.

Due to the severe outbreaks of bluetongue disease (BTD) in the years 2006/2007 in Germany in the absence of the main African vector Culicoides imicola, a rapid and easy applicable method for identification of autochthonous Culicoides spp. had to be developed. Morphological identification is time-consuming, rendering impossible the identification of large numbers of midges in a short period of time. A polymerase chain reaction (PCR)-based procedure in connection with a species-specific primer greatly simplifies the identification process. The region of internal transcribed spacer 1 (ITS-1) of the ribosomal DNA has shown great potential for developing a reliable PCR-based procedure. Culicoides midges were caught with ultraviolet-light traps installed on different farms in Germany during 2007 and 2008. The midges were mounted on slides and morphologically characterised. Midge DNA was extracted and the ITS-1 region amplified using conservative primers. Potential primer regions within ITS-1 were determined and a species-specific Culicoides dewulfi primer was developed to correctly identify autochthonous C. dewulfi, one of the suspected BTV vectors in northwestern Europe. The developed primer was used to identify C. dewulfi in a pool of Culicoides midges from a farm in the state of Brandenburg.

Feeding patterns of biting midges of the Culicoides obsoletus and Culicoides pulicaris groups on selected farms in Brandenburg, Germany.

Host feeding patterns of engorged sibling species of the Culicoides obsoletus and Culicoides pulicaris groups captured during three nights on two selected farms maintaining either cattle, sheep, horses, and pigs (Seedorf, Brandenburg) or cattle, sheep, moufflons, and red and fallow deer (Paulinenaue, Brandenburg) were determined by polymerase chain reaction amplification using conserved primers and sets of species-specific primers derived from vertebrates mitochondrial cytochrome b. Out of a total of 177 blood meals analysed, 115 (65%) tested positive for a blood meal from vertebrates. 63.5% (n = 73) of the cyt b positive specimens could be further assigned down to the species level. Cattle appeared to be the most attractive hosts for Palaearctic biting midges (79.5%, n = 58) even if other large vertebrates were kept in their immediate vicinity. If pigs or horses were additionally maintained on a farm, they were likewise attacked by biting midges but at a distinctly smaller rate than cattle (pigs 13.7%, horses 2.7%). In this study, game animals appear to be less attractive than cattle since only a few engorged midges had taken a blood meal from red deer (4.1%). None of the blood meals analysed tested positive for sheep. Preliminary results reveal that biting midges of the C. pulicaris and C. obsoletus groups can feed on a range of vertebrate hosts but with a distinct preference for cattle even if other livestock are maintained in adjacent areas.

An appraisal of current and new techniques intended to protect bulls against Culicoides and other haematophagous nematocera: the case of Schmergow, Brandenburg, Germany.

The outbreak of bluetongue (BTV-8) in many parts of north-western Europe led to efforts to curb the spread of the disease, particularly in farms with valuable livestock, as on a stud bull farm in Schmergow, Brandenburg, Germany. In the abundance of the putative BT vectors, Palaearctic Culicoides species, several vector control methods were applied in the hope for a reduction of the target insect populations. Insecticide-impregnated ear tags and regular treatments at 6-week intervals of all bulls with deltamethrin pour on were expected to achieve the desired control of the biting midges. Additionally, insecticide-treated mosquito fences circumventing much of the pens were tried for the first time against Culicoides. Two suction black-light traps (BioGents(R) sentinel traps) helped to monitor the densities of Culicoides and other haematophagous nematocera during the trial period from July to December 2007. Despite all efforts, the densities of Culicoides were not distinctly reduced. Several thousand midges were repeatedly recorded during one-night catches. Examinations of midges and other haematophagous nematocera (Aedes and Anopheles species) revealed high percentages of successful feedings between 10% and 35% for Culicoides and more than 50% for Aedes and Anopheles species. Since all insects were caught inside the pens, the concept of endophily vs exophily or endophagy vs exophagy for some Culicoides species needs to be revised accordingly. Also, stabling of valuable livestock does not reduce the host-vector interface and, hence, the risk of transmission of BT.

Seasonal dynamics of biting midges (Diptera: Ceratopogonidae, Culicoides spp.) on dairy farms of Central Germany during the 2007/2008 epidemic of bluetongue.

The unforeseen outbreak of bluetongue in north-western Europe in August 2006 raised the question, which Culicoides spp. were involved in the transmission of bluetongue virus (BTV). Based on the decision 2007/20/EU of December 2006, a large-scale entomological surveillance programme was initiated in the five affected EU member states including Germany. This paper reports on the entomological findings obtained from March/April 2007 to May 2008 at 15 sampling sites in the federal states of Lower Saxony (eastern region), Mecklenburg-Western Pomerania, Brandenburg and Saxony-Anhalt: The number of captured biting midges in one trap varied from none or few Culicoides during winter (December 2007 to April 2008) to up to more than 12,500 individuals during summer and autumn. Catches of the C. obsoletus group were consistently higher than those of the C. pulicaris group. C. imicola, the principal afro-asiatic vector of BTV, was not detected. High numbers of midges were caught inside the cattle sheds. Eleven pools of biting midges were RT-PCR-positive to BTV-8 including pools of non-engorged midges of the C. obsoletus and of the C. pulicaris groups. The first BTV-genome positive pool of midges was detected in August 2007; the remaining genome-positive pools were detected during October and November 2007.

Bluetongue disease in Germany (2007-2008): monitoring of entomological aspects.

In the summer of 2006, a bluetongue epidemic started in the border area of Belgium, The Netherlands, and Germany, spread within 2 years over large areas of Western and Central Europe, and caused substantial losses in farm ruminants. Especially sheep and cattle were severely affected, leading to a case-fatality ratio of nearly 40% in sheep (Conraths et al., Emerg Inf Dis 15(3):433-435, 2009). The German federal ministry of food, agriculture, and consumer protection (BMELV) established a countrywide monitoring on the occurrence of the vectors of this virus, i.e., midges (family Ceratopogonidae) of the genus Culicoides. The monitoring was done on 91 sites, most of which were localized in the 150-km restriction zone that existed in December 2006. A grid consisting of 45 x 45 km(2) cells was formed that covered the monitoring area. As a rule, one trap was placed into each grid cell. The monitoring program started at the end of March 2007 and lasted until May 2008. It included the catching of midges by ultraviolet light traps-done each month from days 1 until 8, the selection of midges of the Culicoides obsoletus, Culicoides pulicaris group, and other Culicoides spp., the testing of midges for bluetongue virus (BTV) by polymerase chain reaction (PCR), and the daily registration of weather data at each trap site for the whole monitoring period. The following main results were obtained: (1) Members of the C. obsoletus group were most commonly found in the traps, reaching often 3/4 of the catches. The African and South European vector of BTV-the species Culicoides imicola-was never found. (2) Members of the C. obsoletus group were most frequently found infected with BTV besides a few cases in the C. pulicaris group and other species. (3) Members of the C. obsoletus group were also found in winter. Their numbers were reduced, however, and they were caught mostly close to stables. Therefore, a true midge-free period does not exist during the year in Germany. (4) The amounts of midges caught daily depended on the weather conditions. If it was cold and/or windy, the traps contained only a few specimens. Since the months from January to May 2008 were considerably colder (at all farms) than their correspondents in 2007, the growing of the population of midges started 2-3 months later in 2008 than in 2007. (5) The highest populations of midges occurred in both years (2007 and 2008) during the months September and October. This corresponded significantly to the finding of highest numbers of infected midges and to the number of diseased cattle and sheep during these 2 months. (6) It is noteworthy that in general, the first virus-positive midges of the species C. obsoletus were found about 1 1/2 months later than the first clinical cases had occurred or later than the first PCR-proven virus-positive sentinel animals had been documented. In 2007, the first BTV-positive cattle were detected in May in North Rhine-Westphalia, while the first positive Culicoides specimens were only found in August on the same farm. Evaluating these main results of the entomological monitoring and the fact that many wild ruminants have also been infected with BTV, it becomes evident that bluetongue disease has become endemic in Central Europe, and that only constant effort including vaccination and perhaps also insecticidal protection of cattle and sheep will keep the economical losses at a reasonable level. The following papers (1-10) in this journal will contribute more details obtained from this worldwide unique entomological monitoring: Bartsch et al. 2009; Bauer et al. 2009; Stephan et al. 2009; Clausen et al. 2009; Hörbrand and Geier 2009; Kiehl et al. 2009; Mehlhorn et al. 2009; Kiel et al. 2009; Vorsprach et al. 2009; Balczun et al. 2009.

How rational drug use reduces trypanosome infections in cattle in chemo-resistance hot-spot villages of northern Togo.

The study assessed an integrated trypanosomosis control strategy in drug-resistant hotspot villages of northern Togo. This strategy comprised (i) rational trypanocidal drug use in symptomatic cattle, (ii) vectors and ticks control by targeted bi-monthly insecticidal spraying of the lower body parts of cattle and (iii) strategic deworming with Albendazole in the beginning and the end of the rainy season. The program was implemented between June 2014 and October 2015 in four villages in northern Togo, which had been previously identified as drug resistant hotspots for diminazene diaceturate (DA) and isometamidium chloride (ISM). The integrated control strategy was implemented in eight cattle herds at risk of the disease from two villages. Twelve herds from two other villages served as controls where trypanosomosis management and deworming remained under control of the farmers. Trypanocidal drug use during the study period was recorded by the intervention team based on the farmers' reports and own observations. Cattle herds were followed-up for trypanosomosis symptoms which were recorded at 3 to 4-month intervals, while extensive trypanosome diagnostics and recording of the packed cell volume were done before and after the intervention. Intervention herds had a significantly lower risk of trypanosome infection with a risk ratio of 0.18 (95% CI: 0.04, 0.91; p = 0.03), but no significant effect on mean packed cell volume was observed. However, trypanocidal treatments per animal per year were lower in intervention herds compared to control herds (0.3 vs 5 for DA and 0.8 vs 2 for ISM). This study demonstrates that the implementation of an integrated best-bet strategy leads to a reduced trypanosome prevalence under lowered trypanocidal use.

Isometamidium sensitivity of Trypanosoma congolense stocks from cattle in West Africa tested in mice and the drug incubation infectivity test.

Four Trypanosoma (T.) congolense reference clones with known isometamidium sensitivity and 16 T. congolense stocks from cattle in Kénédougou in south-western Burkina Faso, an area with known history of drug resistance, were characterised with the standard mouse test (SMT) and the drug incubation infectivity test (DIIT). All field stocks from Kénédougou were resistant to 1.0 mg/kg bw isometamidium in the SMT. Fourteen stocks (87.5%) also proved to be refractory to 10 mg/kg bw. Testing with the DIIT confirmed the results of the SMT. By comparison to reference clones, all the Kénédougou populations expressed high levels of resistance to isometamidium.

Trypanocidal failure suggested by PCR results in cattle field samples.

The aim of this study was to assess, whether polymerase chain reaction (PCR) allows sensitive screening of treatment failure suspicions in areas, where drug resistance against African animal trypanosomosis (AAT) appears to be a problem. PCR was used to detect trypanosome infections prior to, 14 and 28 days after controlled treatment of 738 cattle from 10 villages in Kénédougou, Burkina Faso with isometamidium chloride and diminazene aceturate. Using three sets of primers, PCR was three-four times more sensitive and better at species identification, than standard microscopic examination. The better sensitivity and species specificity of PCR have important advantages for drug resistance studies in the field.

Field studies of drug-resistant cattle trypanosomes in Kénédougou Province, Burkina Faso.

Field studies were conducted to assess the occurrence of resistance to isometamidium chloride and diminazene aceturate in trypanosomes infecting cattle in Kénédougou Province of Burkina Faso. Forty-five of the 166 villages in Kénédougou were randomly sampled and visited to assess livestock numbers, trypanosomosis risk, and tsetse challenge. The proportion of cattle infections associated with drug-resistant trypanosomes was assessed in the nine villages with the highest trypanosome infection prevalence and one village with a confirmed history of drug-resistant infections. These studies showed that resistance to both isometamidium and diminazene was widespread. However, there was considerable variation between villages in drug-resistance parameters, with the proportion of treated cattle with trypanosome infections 3 months after isometamidium prophylaxis varying from 6.9 to 63.8% and the proportion of cattle having infections 2 weeks after treatment with diminazene varying from 0 to 36.8%. The demonstration of widespread resistance to both isometamidium and diminazene has important implications, as administration of trypanocides is the most commonly employed method to control trypanosomosis in this area.

[Acquisition and assessment of patient exposure in diagnostic radiology and nuclear medicine]. / Erfassung und Bewertung der Patientenexposition in der diagnostischen Radiologie und Nuklearmedizin.

The regular annual monitoring of patient exposure in radiation diagnostics, as performed by the Federal Office for Radiation Protection (BfS), plays an important role in evaluating the awareness of radiological quality and safety in Germany and the risk-benefit optimization for patients. For the reporting year 1997, X-ray diagnostics resulted in a mean effective dose of 2 +/- 0.5 mSv per head of population. The underlying frequency of medical X-ray examinations was approximately 136 million, i.e., 1.7 examinations annually per head of population. In terms of nuclear medicine diagnostics, the patients exposure amounted to approximately 0.15 mSv effective dose per head of population. In this case, the number of examinations amounted to approximately 4 million, corresponding to a frequency of approximately 0.05 examinations annually per head of population. The paper discusses factors influencing the calculation of exposure, as well as the lack of an internationally accepted protocol to evaluate patient exposure.

Feeding behaviour of Culicoides spp. (Diptera: Ceratopogonidae) on cattle and sheep in northeast Germany.

BACKGROUND: Culicoides spp. play an important role in the transmission of several vector-borne pathogens such as Bluetongue and Schmallenberg virus in Europe. To better understand the biology of local Culicoides species, a study divided into three parts was performed in northeast Germany to elucidate the feeding activity patterns (study A), preferential landing and feeding sites (study B) and host feeding preferences (study C) of Culicoides spp. using cattle and sheep as baits. METHODS: In study A, the activity of Culicoides spp. was monitored over a 72 h period by collecting insects at regular intervals from the interior of drop traps with cattle or sheep standing inside. In study B, Culicoides spp. were directly aspirated from the coat and fleece of cattle and sheep during the peak activity period of Culicoides. In study C, Culicoides spp. were collected using drop traps with either cattle or sheep standing inside and located 10 m apart. RESULTS: In study A, 3,545 Culicoides midges belonging to 13 species were collected, peak activity was observed at sunset. In study B, 2,024 Culicoides midges were collected. A significantly higher number of midges was collected from the belly and flank of cattle in comparison to their head region. In study C, 3,710 Culicoides midges were collected; 3,077 (83%) originated from cattle and 633 (17%) from sheep. Nearly half (46.7%) of the midges collected from cattle were engorged, significantly more than the number of engorged midges collected from sheep (7.5%). Culicoides from the Obsoletus complex (C. obsoletus and C. scoticus) were the most common Culicoides species encountered, followed by C. punctatus. Other species identified were C. dewulfi, C. chiopterus, C. pulicaris, C. lupicaris, C. pallidicornis, C. subfascipennis, C. achrayi, C. stigma, C. griseidorsum and C. subfagineus, the last two species are reported for the first time in Germany. Engorged C. chiopterus were collected in relatively high numbers from sheep, suggesting that this species may have a preference for sheep. CONCLUSIONS: An insight into the feeding behaviour of local Culicoides species under field conditions in northeast Germany was obtained, with implications for the implementation of control measures and midge-borne disease risk analysis.

Identification of Tsetse (Glossina spp.) using matrix-assisted laser desorption/ionisation time of flight mass spectrometry.

Glossina (G.) spp. (Diptera: Glossinidae), known as tsetse flies, are vectors of African trypanosomes that cause sleeping sickness in humans and nagana in domestic livestock. Knowledge on tsetse distribution and accurate species identification help identify potential vector intervention sites. Morphological species identification of tsetse is challenging and sometimes not accurate. The matrix-assisted laser desorption/ionisation time of flight mass spectrometry (MALDI TOF MS) technique, already standardised for microbial identification, could become a standard method for tsetse fly diagnostics. Therefore, a unique spectra reference database was created for five lab-reared species of riverine-, savannah- and forest- type tsetse flies and incorporated with the commercial Biotyper 3.0 database. The standard formic acid/acetonitrile extraction of male and female whole insects and their body parts (head, thorax, abdomen, wings and legs) was used to obtain the flies' proteins. The computed composite correlation index and cluster analysis revealed the suitability of any tsetse body part for a rapid taxonomical identification. Phyloproteomic analysis revealed that the peak patterns of G. brevipalpis differed greatly from the other tsetse. This outcome was comparable to previous theories that they might be considered as a sister group to other tsetse spp. Freshly extracted samples were found to be matched at the species level. However, sex differentiation proved to be less reliable. Similarly processed samples of the common house fly Musca domestica (Diptera: Muscidae; strain: Lei) did not yield any match with the tsetse reference database. The inclusion of additional strains of morphologically defined wild caught flies of known origin and the availability of large-scale mass spectrometry data could facilitate rapid tsetse species identification in the future.

The effect of deltamethrin-treated net fencing around cattle enclosures on outdoor-biting mosquitoes in Kumasi, Ghana.

Classic vector control strategies target mosquitoes indoors as the main transmitters of malaria are indoor-biting and -resting mosquitoes. However, the intensive use of insecticide-treated bed-nets (ITNs) and indoor residual spraying have put selective pressure on mosquitoes to adapt in order to obtain human blood meals. Thus, early-evening and outdoor vector activity is becoming an increasing concern. This study assessed the effect of a deltamethrin-treated net (100 mg/m(2)) attached to a one-meter high fence around outdoor cattle enclosures on the number of mosquitoes landing on humans. Mosquitoes were collected from four cattle enclosures: Pen A - with cattle and no net; B - with cattle and protected by an untreated net; C - with cattle and protected by a deltamethrin-treated net; D - no cattle and no net. A total of 3217 culicines and 1017 anophelines were collected, of which 388 were Anopheles gambiae and 629 An. ziemanni. In the absence of cattle nearly 3 times more An. gambiae (p<0.0001) landed on humans. The deltamethrin-treated net significantly reduced (nearly three-fold, p<0.0001) culicine landings inside enclosures. The sporozoite rate of the zoophilic An. ziemanni, known to be a secondary malaria vector, was as high as that of the most competent vector An. gambiae; raising the potential of zoophilic species as secondary malaria vectors. After deployment of the ITNs a deltamethrin persistence of 9 months was observed despite exposure to African weather conditions. The outdoor use of ITNs resulted in a significant reduction of host-seeking culicines inside enclosures. Further studies investigating the effectiveness and spatial repellence of ITNs around other outdoor sites, such as bars and cooking areas, as well as their direct effect on vector-borne disease transmission are needed to evaluate its potential as an appropriate outdoor vector control tool for rural Africa.

Detection of multiple drug-resistant Trypanosoma congolense populations in village cattle of south-east Mali.

BACKGROUND: Tsetse fly-transmitted African animal trypanosomosis causes annual losses that run into billions of dollars. The disease is assumed to cause hunger and poverty in most sub-Saharan countries since it represents a serious impediment to sustainable livestock production. Both a cross-sectional and a longitudinal study were carried out from November to December 2007 to evaluate trypanosomosis risk and susceptibility of trypanosomes to trypanocidal drug treatment in village cattle populations in south-east Mali. METHODS: Eight purposively selected villages participated in the study. In each village, eight traps deployed along drainage lines over 24 hour duration were used to catch tsetse. One hundred systematically selected cattle in the study villages were examined for trypanosomes. All trypanosome-positive cattle were randomly allocated into two treatment groups: a group treated with 0.5 mg/kg bw. isometamidium chloride (ISMM) and a group treated with 3.5 mg/kg bw. diminazene aceturate (DIM). The cattle were monitored for trypanosomes at day 14 and 28 post-treatment. RESULTS: Of the 796 cattle examined, 125 (15.7%) were trypanosome-positive. Village trypanosome prevalences ranged between 11% and 19%. There were no significant (p > 0.05) differences in the village trypanosome prevalences. Trypanosoma congolense was the dominant trypanosome species accounting for 73% (91/125) of the infections and T. vivax the remainder. Twenty (31.7%) of the 63 cattle on 0.5 mg/kg bw. ISMM treatment were still positive14 days post-treatment. Of the 43 aparasitaemic cattle monitored to day 28, 25.6% (11) became parasitaemic, resulting in a cumulative failure rate of 49.2% (31/63). Trypanosoma congolense accounted for 77.4% (24/31) of failed ISMM treatments. The 62 cattle treated with 3.5 mg/kg bw. DIM resulted in 30.6% (19/62) failed treatments. Although 42.2% (19/45) of T. congolense positive cattle did not respond to DIM treatment, all T. vivax positive cattle responded positively to DIM treatment. CONCLUSIONS: The overreliance on trypanocides in the control of trypanosomosis will ultimately lead to multiple drug-resistant trypanosome populations as detected in villages in south-east Mali rendering the use of drugs doubtful. Effective alternative methods for trypanosomosis control ought to substitute chemotherapy to ensure sustainable cattle production in these villages. Since there is no single strategy for containing trypanocidal drug resistance, promotion of an integrated approach combining proven trypanosomosis control approaches in high trypanosomosis risk areas is most desirous. The best-bet strategy this study recommended for areas with multiple drug resistance included area-wide community tsetse control, control of co-infections to exploit self-cure against resistant trypanosome populations and the rational use of trypanocidal drugs which should be urgently promoted at all levels as a way of containing or reversing resistance.