Toxoplasma gondii (T. gondii) is an important human disease-causing parasite. In the USA, T. gondii infects >10% of the population, accrues economic losses of US$3.6 billion/year, and ranks as the second leading culprit of foodborne illness-related fatalities. We assessed toxoplasmosis risk among the Old Order Amish, a mostly homogenous population with a high prevalence of T. gondii seropositivity, using a questionnaire focusing on food consumption/preparation behaviours and environmental risk factors. Analyses were conducted using multiple logistic regression. Consuming raw meat, rare meat, or unpasteurised cow or goat milk products was associated with increased odds of seropositivity (unadjusted Odds Ratios: 2.192, 1.613, and 1.718 , respectively). In separate models by sex, consuming raw meat, or consuming unpasteurised cow or goat milk products, was associated with increased odds of seropositivity among women; washing hands after touching meat with decreased odds of seropositivity among women (adjusted OR (AOR): 0.462); and cleaning cat litterbox with increased odds of seropositivity among men (AOR: 5.241). This is the first study to assess associations between behavioural and environmental risk factors and T. gondii seropositivity in a US population with high seroprevalence for T. gondii. Our study emphasises the importance of proper food safety behaviours to avoid the risk of infection.

The Functional Visual Field (FVF) offers explanatory power. To us, it relates to existing literature on the flexibility of attentional focus in visual search and reading (Eriksen & St. James 1986; McConkie & Rayner 1975). The target article promotes reflection on existing findings. Here we consider the FVF as a mechanism in the Prevalence Effect (PE) in visual search.

The MIAMI* facility at the University of Huddersfield is one of a number of facilities worldwide that permit the ion irradiation of thin foils in-situ in a transmission electron microscope. MIAMI has been developed with a particular focus on enabling the in-situ implantation of helium and hydrogen into thin electron transparent foils, necessitating ion energies in the range 1 – 10 keV. In addition, however, ions of a variety of species can be provided at energies of up to 100 keV (for singly charged ions), enabling studies to focus on the build up of radiation damage in the absence or presence of implanted gas.

This paper reports on a number of ongoing studies being carried out at MIAMI, and also at JANNuS (Orsay, France) and the IVEM / Ion Accelerator Facility (Argonne National Lab, US). This includes recent work on He bubbles in SiC and Cu; the former work concerned with modification to bubble populations by ion and electron beams and the latter project concerned with the formation of bubble super-lattices in metals.

A study is also presented consisting of experiments aimed at shedding light on the origins of the dimensional changes known to occur in nuclear graphite under irradiation with either neutrons or ions. Single crystal graphite foils have been irradiated with 60 keV Xe ions in order to create a non-uniform damage profile throughout the foil thickness. This gives rise to varying basal-plane contraction throughout the foil resulting in almost macroscopic (micron scale) deformation of the graphite. These observations are presented and discussed with a view to reconciling them with current understanding of point defect behavior in graphite.

*Microscope and Ion Accelerator for Materials Investigations

Following a 14-day uniformity period when they were stall-fed to appetite on a grass silage-grass ration, 18 cows in mid lactation were allocated to three treatments on which they received during the following 28 days either 100%, 75% or 50% of their previous voluntary feed intakes.

Treatment effects were measured on milk yield and composition, live weight, liveweight change and fasted live-weight change. Twice during uniformity period, and on the 7th, 14th, 22nd and 26th days of the treatment period, samples of jugular blood were obtained from each cow immediately before and 3 h after the first meal of the day. These were analysed for percentage packed cell volume, blood acetone and β-hydroxybutyrate levels, plasma glucose, non-esterified fatty acid, and total fatty acid concentrations.

Alternative methods of collecting blood samples, involving cannulation of the vein and venipuncture, were compared. Obtaining samples through cannulae took nearly three times as long as by venipuncture, but the method of sampling did not significantly affect the concentrations of individual blood metabolites. Blood samples collected before as contrasted with after feeding had significantly higher concentrations of nonesterified fatty acids and glucose, and lower concentrations of acetone and β-hydroxybutyrate.

The feed requirements of the cows were assessed using data on live weights, fasted live-weight change and milk production by calculating the regression of estimated net attributable energy/kg LW0·75 on digestible energy intake/kg LW0·75, from data for the full 28-day period. The maintenance requirement was 124 kcal net energy/kg LW0·75, and the efficiency of conversion of digestible energy to milk and body-tissue loss or gain was 60%. These data were used with each animal's live weight, milk yield and liveweight change appropriate to each blood-sampling day to calculate individual feed requirements on every occasion. Ratios of actual feed consumed to estimated requirements were calculated subsequently to provide quantitative indices involving all cows and feeding levels. Regressions of these indices on individual blood metabolites were examined to assess the value of the latter as predictors of the relative nutritional status of the cows as defined in this way. Of the blood metabolites studied, only plasma NEFA were consistently significantly correlated with these indices, and relationships were specific to each feeding level. Thus although, at a common feeding level, plasma NEFA can be used to categorize lactating cows according to degree of nutritional stress, they will have limited values as predictors if applied indiscriminately to the wide range of feed availabilities and intakes which exist between herds at similar stages of lactation.

The results have been discussed relative to previously published work, mainly with sheep and beef cattle.

The hypothesis that the parasite Toxoplasma gondii manipulates the behaviour of its intermediate rat host in order to increase its chance of being predated specifically by its feline definitive host, rather than a non-definitive host predator species, was tested. The impact of a range of therapeutic drugs, previously demonstrated to be effective in preventing the development of T. gondii-associated behavioural and cognitive alterations in rats, on definitive-host predator specificity was also tested. Using a Y-shaped maze design, we demonstrated that T. gondii-associated behavioural changes, apparently aimed to increase predation rate, do appear to be specific to that of the feline definitive host – there were significant and consistent differences between the (untreated) infected and uninfected rats groups where T. gondii-infected rats tended to choose the definitive host feline-predator-associated maze arm and nest-box significantly more often than a maze arm or nest-box treated with non-definitive host predator (mink) odour. Drug treatment of infected rats prevented any such host-specificity from being displayed. We discuss our results in terms of their potential implications both for T. gondii epidemiology and the evolution of parasite-altered behaviour.

The Randomized Badger Culling Trial (RBCT) began in 1998 to determine the impact of badger culling in controlling bovine tuberculosis in cattle. A total of 1166 badgers (14% of total) proactively culled during the RBCT were found to be tuberculous, offering a unique opportunity to study the pathology caused by Mycobacterium bovis in a large sample of badgers. Of these, 39% of adults (~6% of all adults culled) had visible lesions (detectable at necropsy) of bovine tuberculosis; cubs had a lower prevalence of infection (9%) but a higher percentage of tuberculous cubs (55·5%) had visible lesions. Only ~1% of adult badgers had extensive, severe pathology. Tuberculous badgers with recorded bite wounds (~5%) had a higher prevalence of visible lesions and a different distribution of lesions, suggesting transmission via bite wounds. However, the predominance of lesions in the respiratory tract indicates that most transmission occurs by the respiratory route.

Heat-transfer measurements have been made in normal liquid He contained within a rotating, cylindrical, cryogenic Bénard cell with variable aspect ratio. Data are presented for a range of dimensionless angular velocities 0 ≤ Ω < 600 and Prandtl numbers 0.49 ≤ Pr < 0.76 and for three aspect ratios Γ of 7.81, 4.93 and 3.22. Where possible, comparisons are made with theoretical predictions and past experiments concerning heat transfer in rotating fluids.

Equipment is described for performing measurements of the Rayleigh–Bénard instability in a sample of rotating liquid 4He. Data are presented on the dependence of the critical Rayleigh number for the onset of convection on Prandtl number in the range 0·49 < Pr < 0·76 and over a range of dimensionless angular velocities 0 < Ω < 200. Evidence for the existence of subcritical convection is presented.

We describe the dynamics of co-infections of Plasmodium falciparum and P. vivax in 28 asymptomatic children by genotyping these species using the polymorphic loci Msp2 and Msp3α, respectively. The total number of Plasmodium spp. infections detected using 3 day sampling over 61 days varied between 1 and 14 (mean 6·6). The dynamics of P. falciparum and P. vivax genotypes varied greatly both within and amongst children. Periodicity in the detection of P. falciparum infections is consistent with the synchronous replication of individual genotypes. Replication synchrony of multiple co- infecting genotypes was not detected. In 4-year-old children P. falciparum genotype complexity was reduced and episodes lasted significantly longer (median duration > 60 days) when compared to children aged 5–14 years (median duration 9 days). P. vivax genotype complexity was not correlated with age but the episode duration was also longer for this species in 4-year-olds than in older children but was not as long as P. falciparum episodes. Recurrence of P. falciparum and P. vivax genotypes over weeks was observed. We interpret these major fluctuations in the density of genotypes over time as the result of the mechanism of antigenic variation thought to be present in these Plasmodium species.

Polymerase chain reaction (PCR)-based genotyping of oocysts dissected from mosquito midguts has previously been used to investigate overall levels of inbreeding within malaria parasite populations. We present a re-analysis of the population structure of Plasmodium falciparum malaria using diploid genotypes at three antigen-encoding loci in 118 oocysts dissected from 34 mosquitoes. We use these data to ask whether mating is occurring at random within the mosquito midgut, as is generally assumed. We observe a highly significant deficit of heterozygous oocysts within mosquitoes at all three loci, suggesting that fusion of gametes occurs non-randomly in the mosquito gut. A variety of biological explanations, such as interrupted feeding of mosquitoes, positive assortative mating and outcrossing depression, could account for this observation. However, an alternative artefactual explanation – the presence of non-amplifying or null alleles – can account for the observed data equally well, without the need to invoke non-random mating. To evaluate this explanation further, we estimate the frequencies of null alleles within the oocyst population using maximum likelihood, by making the assumption that non-amplifying oocysts at any of the three loci are homozygous for null alleles. Observed levels of visible heterozygotes fit closely with those expected under random mating when non-amplifying oocysts are accounted for. Other lines of evidence also support the artefactual explanation. Overall inbreeding coefficients have been recalculated in the light of this analysis, and may be considerably lower than those estimated previously. In conclusion, we suggest that the deficit of heterozygotes observed is unlikely to indicate non-random mating within the mosquito gut and is better explained by misscoring of heterozygotes as homozygotes.

Schwannomas of the head and neck are uncommon tumours that arise from any peripheral, cranial or autonomic nerve. Twenty-five to 45 per cent of extracranial schwannomas occur in the head and neck region and thus are usually in the domain of the otolaryngologist. They usually present insidiously and thus are often diagnosed incorrectly or after lengthy delays, however, better imaging and cytological techniques have lessened this to some degree more recently. For benign lesions conservative surgical excision is the treatment of choice bearing in mind possible vagal or sympathetic chain injury. Malignant schwannomas are best treated with wide excision where possible. The role of adjuvant therapy remains uncertain and irrespective of treatment modality prognosis is poor with an overall survival of 15 per cent. However, recent advances in ras oncogene inhibitors may hold hope for the future.

A prospective study into the aetiology of acute food bolus obstruction (AFBO) was carried out on 17 consecutive patients who presented with this complaint. There were nine males and eight females. Twelve patients (71 per cent) had symptoms of oesophageal disease and 10 patients (59 per cent) had prior food bolus obstruction. Investigations included endoscopy, barium swallow, oesophageal pH and manometry studies. Evidence of oesophageal pathology was found in 12/14 (86 per cent) of patients investigated. No patients had malignancy and the most common abnormality, gastroesophageal reflux (GOR) was found in eight out of 14 (57 per cent) of cases. Oesophageal dysmotility was seen in five out of 12 (42 per cent) patients who had manometric studies.

With such a high incidence of recurrence of AFBO, we suggest that patients with this condition be investigated to exclude malignancy and to identify benign oesophageal pathology using techniques such as oesophageal pH and manometry. Appropriate treatment of oesophageal disease may help prevent recurrence of this distressing condition.

Tonsillectomy is a commonly performed operation in children. Although the justification for this procedure has been debatable in the past, more rigorous criteria in defining the need for tonsillectomies are becoming established. The role of the primary care physician in the management of tonsillar disease in children is important as the decision to refer a child for tonsillectomy is made by the general practitioner. A questionnaire survey of 400 general practitioners (GPs) and 31 consultant ENT surgeons was carried out to establish the important criteria used in deciding the need for paediatric tonsillectomy. We found that in general there was a good correlation between GP and Consultant indications for tonsillectomy. However there were two important areas of difference, while most of the GPs felt that recurrent ear infections and ‘glue ear’ were important indications for tonsillectomy, Consultants did not. Therefore we must be aware of the current recommendations for tonsillectomy and inform present and future GPs.