Impact of selection regime and introgression on deltamethrin resistance in the arbovirus vector Aedes aegypti - a comparative study between contrasted situations in New Caledonia and French Guiana

BACKGROUND

Pyrethroid insecticides such as deltamethrin have been massively used against Aedes aegypti leading to the spread of resistance alleles worldwide. In an insecticide resistance management context, we evaluated the temporal dynamics of deltamethrin resistance using two distinct populations carrying resistant alleles at different frequencies. Three different scenarios were followed: a continuous selection, a full release of selection, or a repeated introgression with susceptible individuals. The responses of each population to these selection regimes were measured across five generations by bioassays and by monitoring the frequency of knockdown resistance (kdr) mutations and the transcription levels and copy number variations of key detoxification enzymes.

RESULTS

Knockdown resistance mutations, overexpression and copy number variations of detoxification enzymes as a mechanism of metabolic resistance to deltamethrin was found and maintained under selection across generations. On comparison, the release of insecticide pressure for five generations did not affect resistance levels and resistance marker frequencies. However, introgressing susceptible alleles drastically reduced deltamethrin resistance in only three generations.

CONCLUSION

The present study confirmed that strategies consisting to stop deltamethrin spraying are likely to fail when the frequencies of resistant alleles are too high and the fitness cost associated to resistance is low. In dead-end situations like in French Guiana where alternative insecticides are not available, alternative control strategies may provide a high benefit for vector control, particularly if they favor the introgression of susceptible alleles in natural populations. © 2021 Society of Chemical Industry.

Non-Invasive versus Invasive Samples for Zika Virus Surveillance: A Comparative Study in New Caledonia and French Guiana in 2015-2016

Zika virus, an arbovirus responsible for major outbreaks, can cause serious health issues, such as neurological diseases. In the present study, different types of samples (serum, saliva, and urine), collected in 2015–2016 in New Caledonia and French Guiana from 53 patients presenting symptoms and clinical signs triggered by arbovirus infections, were analyzed using a recently developed, and in-house validated, 4-plex RT-qPCR TaqMan method for simultaneous detection and discrimination of the Zika and Chikungunya viruses. Subsequently, statistical analyses were performed in order to potentially establish recommendations regarding the choice of samples type to use for an efficient and early stage Zika infection diagnosis. On this basis, the use of only urine samples presented the highest probability to detect viral RNA from Zika virus. Moreover, such a probability was improved using both urine and saliva samples. Consequently, the added value of non-invasive samples, associated with a higher acceptance level for collection among patients, instead of serum samples, for the detection of Zika infections was illustrated.

MALDI-TOF MS: optimization for future uses in entomological surveillance and identification of mosquitoes from New Caledonia

Background

Mosquito vectors cause a significant human public health burden through the transmission of pathogens. Due to the expansion of international travel and trade, the dispersal of these mosquito vectors and the pathogens they carry is on the rise. Entomological surveillance is therefore required which relies on accurate mosquito species identification. This study aimed to optimize the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for mosquito identification.

Methods

Aedes aegypti of the Bora-Bora strain and 11 field-sampled mosquito species were used in this study. Analyses were performed to study the impact of the trapping duration on mosquito identification with MALDI-TOF MS. The best preservation methods to use for short, medium and long-term preservation before MALDI-TOF MS analysis were also assessed. In addition, the number of specimens per species required for MALDI-TOF MS database creation was determined. The first MALDI-TOF database of New Caledonian mosquitoes was assembled and the optimal threshold for mosquito species identification according to the sensitivity and specificity of this technique was determined.

Results

This study showed that the identification scores decreased as the trapping duration increased. High identification scores were obtained for mosquitoes preserved on silica gel and cotton at room temperature and those frozen at − 20 °C, even after two months of preservation. In addition, the results showed that the scores increased according to the number of main spectrum patterns (MSPs) used until they reached a plateau at 5 MSPs for Ae. aegypti. Mosquitoes (n = 67) belonging to 11 species were used to create the MALDI-TOF reference database. During blind test analysis, 96% of mosquitoes tested (n = 224) were correctly identified. Finally, based on MALDI-TOF MS sensitivity and specificity, the threshold value of 1.8 was retained for a secure identification score.

Conclusions

MALDI-TOF MS allows accurate species identification with high sensitivity and specificity and is a promising tool in public health for mosquito vector surveillance.

Introduction of the Anopheles bancroftii Mosquito, a Malaria Vector, into New Caledonia

In June 2017, an Anopheles mosquito species was detected in New Caledonia. Morphologic identification and genomic sequencing revealed that the specimens tested belong to An. bancroftii genotype A1. This introduction underscores the risk for local malaria transmission and the vulnerability of New Caledonia to vector introduction.

Radioreceptor assays of ipratropium bromide in plasma and urine

Ipratropium bromide (Ipbr) is a frequently used quaternary anticholinergic administered by inhalation in the treatment of chronic obstructive lung diseases. Hardly any pharmacokinetic data are available, which can be useful in the optimisation of anticholinergic therapies. Hence, a radioreceptor assay (RRA) for Ipbr has been developed. The RRA is based on the competition between (3)H-N-methylscopolamine chloride ((3)H-NMS) and Ipbr for binding to lyophilised muscarinic receptors from calf brains. The assay has been optimised in respect of incubation conditions and extraction by ion-pair formation with sodium picrate. Detection limits of the drug were 5 ng ml(-1) in urine and 500 pg ml(-1) in plasma, after extraction of 2-ml samples. The method is applicable to monitoring the drug in plasma and urine after therapeutic dosing.

Relationship between antimicrobial drug usage and antimicrobial susceptibility of gram-positive mastitis pathogens

The objective of this study was to analyze relationships between usage of antimicrobial drugs on dairy farms and results of antimicrobial susceptibility testing of mastitis pathogens. Exposure to selected antimicrobial drugs (n = 10) was standardized by calculation of the number of defined daily doses used per cow. Farms (n = 40) were categorized based on amount of antimicrobial exposure: organic (no usage); conventional-low usage (conventional farms not using or using less than or equal to the first quartile of use of each compound); and conventional-high usage (conventional farms using more than the first quartile of a particular compound). The minimum inhibitory concentration (MIC) of selected antimicrobial drugs was determined using a commercial microbroth dilution system for isolates of Staphylococcus aureus (n = 137), coagulase-negative staphylococci (CNS, n = 294), and Streptococcus spp. (n = 95) obtained from subclinical mastitis infections. Most isolates were inhibited at the lowest dilution tested of most antimicrobial drugs. Survival curves for Staph. aureus and CNS demonstrated heterogeneity in MIC based on the amount of exposure to penicillin and pirlimycin. For CNS, farm type was associated with the MIC of ampicillin and tetracycline. For Streptococcus spp., farm type was associated with MIC of pirlimycin and tetracycline. For all mastitis pathogens studied, the MIC of pirlimycin increased with increasing exposure to defined daily doses of pirlimycin. The level of exposure to most other antimicrobial drugs was not associated with MIC of mastitis pathogens. A dose-response effect between antimicrobial exposure and susceptibility was observed for some pathogen-antimicrobial combinations, but exposure to other antimicrobial drugs commonly used for prevention and treatment of mastitis was not associated with resistance.

Treatment practices and quantification of antimicrobial drug usage in conventional and organic dairy farms in Wisconsin

The objective of this study was to develop a method to quantify antimicrobial drug usage and treatment practices on conventional and organic dairy farms that had been recruited to represent a broad spectrum of potential exposure to antimicrobial drugs. Data on disease prevalence and treatment practices of organic (n = 20) and conventional (n = 20) farms were obtained during a farm visit using a survey instrument. A standardized estimate of antimicrobial drug usage was developed using a defined daily dose (DDD) of selected compounds. Density of antimicrobial drug usage was expressed as the number of DDD per adult cow per year. Differences in prevalence and management of selected diseases between conventional and organic farms were identified. The overall estimated prevalence of selected diseases was greater for conventional farms compared with organic farms. Organic farmers reported use of a variety of nonantimicrobial compounds for treatment and prevention of disease. Conventional farmers reported that penicillin was the compound most commonly used for dry cow therapy and cephapirin was most commonly used for treatment of clinical mastitis. On conventional farms, the estimated overall exposure to antimicrobial drugs was 5.43 DDD per cow per year composed of 3.58 and 1.85 DDD of intramammary and parenteral antimicrobial drugs, respectively. Of total intramammary antimicrobial drug usage, treatment of clinical mastitis contributed 2.02 DDD compared with 1.56 DDD attributed to the use of dry cow therapy. Of total parenteral treatments, the distribution of exposure was 0.52 (dry cow therapy), 1.43 (clinical mastitis treatment), 0.39 (treatment of foot disease), 0.14 (treatment of respiratory disease), and 0.32 (treatment of metritis) DDD. For treatments of foot infections (0.33 DDD), respiratory infections (0.07 DDD), and metritis (0.19 DDD), the mean density of ceftiofur usage was significantly greater compared with other compounds.

Different phenotypes among slow/beta myosin heavy chain-containing fibres of rabbit masseter muscle: a novel type of diversity in adult muscle

Difference in the phenotype of different mammalian muscle fibres are usually attributed to differences in the expression of the product of different myosin heavy chain (MyHC) genes, which are known as isoforms. We studied differences in phenotype among fibres containing a single MyHC isoform (slow/beta) of the masseter muscle of adult rabbits. Four different monoclonal antibodies to slow/beta MyHC were used to stain serial sections from muscles in males and females. All antibodies recognize a single band on immunoblots and stain the same set of fibres in rabbit postcranial muscles. However, differential staining was observed in the masseter muscles. Antibody BA-D5 reacts with the most fibres, antibody A4.951 reacts with a subset of these fibres, and antibody A4.840 reacts with a subset of these fibres, and antibody A4.840 reacts with a subset of A4.951-positive fibres. Antibody S58 reacts only with an even smaller subset of fibres. Even though differential staining using four antibodies might allow for the expression of as many as 15 different staining patterns, or patterns, or phenotypes, only four were observed on > 99% of over 30 000 fibres studied. In females, nearly 40% of the fibres stain exclusively with antibody BA-D5, while in males, fewer than 8% of the fibres express this phenotype. The proportions of fibres of the other phenotypes do not differ so strikingly with gender. We conclude that an epitope diversity exists among muscle fibres in the adult rabbit masseter and that it is not necessarily a consequence of differences in gene expression. We feel that it is a regulated process and that, at least for some phenotypes, this regulation may be hormonally influenced.

[Immunoglobulin A and human immunodeficiency virus type 1 infection in parenteral drug abuse addicts]

BACKGROUND

To evaluate the usefulness of serum immunoglobulin A (IgA) as a prognostic marker of human immunodeficiency virus type 1 (HIV-1) in parenteral drug abusers (PDA).

METHODS

The serum IgA levels and HIV-1 antibodies were assessed in 374 PDAs admitted for infective diseases or for treatment of addiction.

RESULTS

The prevalence of HIV infection was 70%; the frequency of serum IgA above the upper normal limit (440 mg/dl) was 8% in seronegative and 4% in seropositive subjects (NS). The IgA levels in the 274 seropositive subjects, classified for infective stages, were significantly higher in those fulfilling the criteria for acquired immunodeficiency syndrome (AIDS) or AIDS related complex (group IV) than in asymptomatic subjects (group II) or in those with generalized lymphadenopathy (group III) (p less than 0.01).

CONCLUSIONS

Serum IgA levels in PDAs with HIV infection may be a useful marker of progression to AIDS.

Subcutaneous mastectomy as ultimate treatment of galactorrhea

Galactorrhea, caused by hyperprolactinemia can successfully be treated by bromocriptine. Continuous long-term use of this drug is not always desirable or possible because of side-effects. In cases of hyperprolactinemia with severe galactorrhea, where surgical or radiological therapy is not possible and long-term treatment with bromocriptine is not acceptable, subcutaneous mastectomy might be considered as an ultimate solution.