Automated dispensers that dilute concentrated disinfectants with water are commonly used in healthcare facilities. In a point-prevalence product evaluation, 9 of 10 (90%) hospitals using dilutable disinfectants had 1 or more malfunctioning dispensers. Twenty-nine of 107 (27.1%) systems dispensed product with lower-than-expected concentrations, including 15 (14.0%) with no detectable disinfectant.

Over the last 25 years, radiowave detection of neutrino-generated signals, using cold polar ice as the neutrino target, has emerged as perhaps the most promising technique for detection of extragalactic ultra-high energy neutrinos (corresponding to neutrino energies in excess of 0.01 Joules, or 1017 electron volts). During the summer of 2021 and in tandem with the initial deployment of the Radio Neutrino Observatory in Greenland (RNO-G), we conducted radioglaciological measurements at Summit Station, Greenland to refine our understanding of the ice target. We report the result of one such measurement, the radio-frequency electric field attenuation length $L_\alpha$. We find an approximately linear dependence of $L_\alpha$ on frequency with the best fit of the average field attenuation for the upper 1500 m of ice: $\langle L_\alpha \rangle = ( ( 1154 \pm 121) - ( 0.81 \pm 0.14) \, ( \nu /{\rm MHz}) ) \,{\rm m}$ for frequencies ν ∈ [145 − 350] MHz.

On coronavirus disease 2019 (COVID-19) wards, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid was frequently detected on high-touch surfaces, floors, and socks inside patient rooms. Contamination of floors and shoes was common outside patient rooms on the COVID-19 wards but decreased after improvements in floor cleaning and disinfection were implemented.

For patients with methicillin-resistant Staphylococcus aureus (MRSA) colonization, a traditional fist-bump greeting did not significantly reduce MRSA transfer in comparison to a handshake. However, transfer was reduced with a modified fist bump that minimized the surface area of contact and when hand hygiene was performed before the handshake.

In Canada, recreational use of cannabis was legalized in October 2018. This policy change along with recent publications evaluating the efficacy of cannabis for the medical treatment of epilepsy and media awareness about its use have increased the public interest about this agent. The Canadian League Against Epilepsy Medical Therapeutics Committee, along with a multidisciplinary group of experts and Canadian Epilepsy Alliance representatives, has developed a position statement about the use of medical cannabis for epilepsy. This article addresses the current Canadian legal framework, recent publications about its efficacy and safety profile, and our understanding of the clinical issues that should be considered when contemplating cannabis use for medical purposes.

Dietary restriction for the weight-loss management of obese horses limits the natural trickle-feeding behaviour. During feed restriction, wood shavings are often advised as bedding to prevent dietary supplementation from non-feed sources. Data from twelve overweight/obese horses and ponies of mixed breed and sex, bedded on wood shavings during 16 weeks of feed restriction, were retrospectively evaluated. DM intake (DMI) was restricted to 1·25 % of body mass (BM) daily. Animals were randomly assigned to one of two diets (hay/chaff, n 6; hay/balancer meal, n 6). BM was recorded weekly. Feeding behaviour was recorded by continual observation over 24 h during week 15. The apparent digestibility (gross energy (GE), acid-detergent fibre (ADF) and DM) of feed was determined for all animals by total faecal collection (72 h, week 16). Rates of weight loss were independent of diet type, DM (R2 0·15), GE (R2 0·20) and ADF digestibilities (R2 0·18). Despite similar DMI, faecal DM ranged between 0·52 and 1·16 % of BM daily and was associated with wide ranges in apparent digestibility (GE − 11·34 to 53·08 %; ADF − 50·37 to 42·83 % and DM 2·14 to 57·32 %), which were improbably low for some animals. Apparent digestibilities were associated with DM output (GE R2 0·96; ADF R2 0·99 and DM R2 0·99) and time spent feeding (GE R2 0·62; DM R2 0·61 and ADF R2 0·59), indicating that feed intake was supplemented with wood shavings in at least five of the twelve animals. Quantities of wood shavings ingested (negligible to >3·0 kg/d) were back-calculated from predicted feed digestibilities. All animals remained healthy. Implications of ‘feed-bulking/energy dilution’ for feed-restricted animals need further consideration.

Cytoplasmic incompatibility consists of sterility in cross matings, the crossing type being maternally inherited. It can be explained by the action of Wolbachia symbionts which are transmitted through the egg cytoplasm and leave an imprint on the sperm which prevents it fertilizing unless it is ‘rescued’ by the action of the same type of Wolbachia in the egg. Thus matings between infected males and uninfected females are sterile, but the reciprocal matings are fertile. Hence uninfected females are at risk of failing to transmit their uninfected cytoplasm if they cross mate, but infected females are at no such risk. Therefore natural selection favours the infected state and in two wild insect populations the infection has been observed spreading. If a gene for inability to transmit malaria could be introduced into Wolbachia and if this could be introduced into Anopheles (where these symbionts appear not to occur naturally), release of a limited number of such insects should trigger a process of displacement of malaria vectors, by the non-vector type. A simple model is used to demonstrate the limitations to this process which would be introduced by immigration.

Three West African strains of Anopheles gambiae Giles were intensively selected for DDT resistance at the adult stage using both mass selection and family selection with inbreeding. The LT50s for 4% DDT were thereby raised to 2–6 h, i.e. 6–18 × that of a susceptible strain. The selected strains were found to show DDT resistance as first-instar larvae and permethrin resistance as adults. The results of tests for the number of genes involved in causing the resistance and their linkage to genes for dieldrin resistance were equivocal. One of the DDT-resistant strains was bred in population cages with overlapping generations. Releases were made of males of the R70 translocation strain which transmit DDT and dieldrin susceptibility to their female progeny. When DDT selection on the cage population was relaxed, the releases caused a more rapid and complete loss of resistance than occurred in a control population. When selection for DDT resistance was applied to females of the cage population, the releases were able to prevent a build-up of resistance. The use of male releases is discussed as a possible means of countering insecticide resistance in mosquitoes.

Simple one- and multi-generation models are used to show the essential features of the dynamics of selection for resistance to one insecticide or two unrelated insecticides in insect populations, part of which are unexposed to either compound. The use of a mixture appears advantageous provided that resistance is not fully dominant, but, if it is, linkage disequilibrium builds up rapidly and nullifies the advantage of the mixture

A technique, based on the release and recapture of marked females, was used to measure the mating competitiveness of sterile males of Culex pipiens fatigans Wied. in villages in Delhi Union Territory, India. Experiments were carried out with chemosterilised and cytoplasmically incompatible translocated (IS-31B) males simultaneously with prolonged release trials with these two types of male. The fertile males in the tests were the indigenous population and the females used were in most cases of wild origin. With each type of male, one test was conducted with a moderate (ca. 13:1) ratio of released to wild males and the other tests used high (ca. 40:1) ratios. The estimated mean mating competitiveness of IS-31B males was somewhat higher than that of chemosterilised males, but the difference was found to be non-significant using a specially devised method of testing statistical significance. In the four experiments 77–94% of the egg rafts laid by recaptured females were sterile, indicating that both types of sterile male were sufficiently competitive to induce a high level of egg sterility in an isolated wild population.

From previous studies in Garki, Nigeria, it was deduced that the population of Anopheles gambiae Giles s.l. there includes a proportion of individuals which consistently rest out of doors and are therefore not vulnerable to insecticide residues inside houses, but may still be able to maintain malaria transmission. A direct test for the existence of such individuals in A. gambiae s.l. and A. funestus Giles in a village in Tanzania was made by catching resting mosquitoes indoors and in outdoor pits, differentially marking them according to their site of capture and releasing them from a single site. Recaptures indoors and in the pits showed no significant association between the sites of capture and recapture among the females of either species, i.e. no evidence for an invariably outdoor-resting type of female. It is concluded that behavioural polymorphism is unlikely to interfere with the successful use of house spraying for malaria control in this area. From data on the proportion of the captures found to be marked and on the parity rate, estimates were calculated of the total mosquito population available for sampling in the village.

In a Gambian village, the peak collections of females of the complex of Anopheles gambiae Giles occurred three months after the onset of the heaviest rains; 32% of these were A. melas Theobald, and 54% of blood-meals were identified as originating from man. Counts of A. gambiae s.l. in rooms containing permethrin-treated bed nets were compared with those in rooms containing placebo-treated nets. The numbers in the permethrin-treated nets were far lower than in placebo-treated nets. A higher rate of exophily was noted in rooms containing permethrin-treated nets. The numbers of unfed A. gambiae s.l. found inside the rooms with placebo-treated nets were significantly higher than those with permethrin-treated nets. However, the proportion fed and the mortality in the exit traps were not significantly affected by permethrin treatment. Three-minute bioassays conducted on four different fabric types impregnated at the same concentration showed that the toxicity varied between the fabrics. Handwashing severely reduced the toxicity and approximately halved the permethrin content. Bed nets are frequently washed in Gambian villages, and this could be a problem in the application of permethrin impregnation of bed nets for vector control. Methods are discussed to overcome this problem at the village level.

Pieces of netting and sheeting of various types were impregnated by dipping them in permethrin emulsion. Bioassays were performed in which three species of mosquitoes were exposed to the impregnated fabrics for periods of between 15 s and 8 min. When pieces of netting and sheeting were dipped in permethrin emulsion at ambient temperature, the amount of insecticide absorbed was generally proportional to the weight of liquid taken up, i.e. there was no evidence of selective absorption. Diffusion of permethrin did not occur between pieces of netting and sheeting sewn together. The LD50 on cotton nets was found to be about three times as great as on nylon nets. Aedes aegypti (L.) was found to be more susceptible than Anopheles gambiae Giles, which was more susceptible than Culex quinquefasciatus Say. Although for most other groups of insecticides variation in time and dose have equivalent effects, for permethrin on netting this was not found to be true, i.e. on having the exposure time the LD50 was less than doubled.

The use of chromosome translocations for the control of pests, with particular reference to Glossina, is proposed. A translocation arises if two non-homologous chromosomes in the same cell undergo breakage and the fragments re-join with the wrong partners. At meiosis in an individual heterozygous for a translocation, gamete nuclei with several different combinations of chromosomes are produced. Some of these are diploid for one part and lack completely another part of the normal chromosome set; when such unbalanced gametes fertilise normal gametes inviable embryos are produced. It has been found in a number of organisms that about half the gametes of translocation heterozygotes are of the unbalanced type and such heterozygotes are described as semi-sterile. If an individual inherits the same translocation from both parents it is described as a translocation homozygote; this is often inviable but, if not, its fertility is usually normal.

Adult males of G. austeni Newst. have been irradiated and each of their progeny are being screened for the occurrence of semi-sterility. Any individuals found to be semi-sterile would probably be translocation heterozygotes and their progeny will be inbred to try to produce a viable stock, homozygous for a translocation. If this can be done, large numbers of such translocation homozygotes could be reared and released into a wild population, where matings with wild types would produce heterozygotes, and hence a reduction in the fertility of the population.

Using simple assumptions, the effects of releasing translocation homozygotes were computed. Provided the numbers released were such that the translocation frequency approached the optimum value of 50 per cent., the reduction in population fertility would be prolonged for many generations after the releases had finished. It is shown that it would be more efficient to release the translocation homozygotes at successive generations rather than all at once and that the homozygotes released could with advantage be of both sexes. For this reason, and because of the prolonged effect of releases of translocations, it is concluded that the number of individuals that would have to be reared to achieve a given result by the translocation method might be considerably less than if the sterile-male method was used. However, the reduction in population fertility at each generation that can be achieved with the translocation method is limited, and the method would therefore be ineffective against populations whose size was strongly buffered by density-dependent factors.