Estimating the impact of bias in causal epidemiological studies: the case of health outcomes following assisted reproduction

Researchers interested in causal questions must deal with two sources of error: random error (random deviation from the true mean value of a distribution), and bias (systematic deviance from the true mean value due to extraneous factors). For some causal questions, randomization is not feasible, and observational studies are necessary. Bias poses a substantial threat to the validity of observational research and can have important consequences for health policy developed from the findings. The current piece describes bias and its sources, outlines proposed methods to estimate its impacts in an observational study, and demonstrates how these methods may be used to inform debate on the causal relationship between medically assisted reproduction (MAR) and health outcomes, using cancer as an example. In doing so, we aim to enlighten researchers who work with observational data, especially regarding the health effects of MAR and infertility, on the pitfalls of bias, and how to address them. We hope that, in combination with the provided example, we can convince readers that estimating the impact of bias in causal epidemiologic research is not only important but necessary to inform the development of robust health policy and clinical practice recommendations.

Risk factors for dementia and self-harm: A linkage study

INTRODUCTION

People living with dementia experience poor mental health and high rates of self-harm. We investigated risk factors for self-harm in people aged > 40 years living with dementia and risk factors for dementia after self-harm.

METHODS

Using linked hospital data from New South Wales, Australia, we defined a dementia cohort (n = 154,811) and a self-harm cohort (n = 28,972). Using survival analyses, we investigated predictors of self-harm for the dementia cohort, and predictors of dementia for the self-harm cohort.

RESULTS

We found self-harm or dementia diagnoses occurred most often within 24 months of a dementia diagnosis or initial self-harm presentation, respectively. Men living with dementia, and people with complex psychiatric profiles, had the greatest risk of self-harm. Men who had self-harmed had the greatest risk of dementia diagnoses.

DISCUSSION

Men and people with complex psychiatric profiles and dementia may particularly benefit from post-diagnosis mental and behavioral support to reduce risk of self-harm.

Factors associated with discharge from hospital to residential aged care for younger people with neuropsychiatric disorders: an exploratory case-control study in New South Wales, Australia

OBJECTIVES

To examine the sociodemographic and diagnostic factors associated with a discharge from hospital to residential aged care (RAC) for younger people (aged 15-64 years) with neuropsychiatric disorders.

DESIGN

An exploratory case-control study using a historic cohort of people with neuropsychiatric disorders. Cases were people transferred to RAC on hospital discharge during the study period. Controls were people not transferred to RAC on discharge during the study period.

SETTING

Public and private hospital admissions in New South Wales (NSW), Australia.

PARTICIPANTS

People aged 15-64 years with a neuropsychiatric disorder hospitalised in NSW between July 2002 and June 2015 (n=5 16 469).

OUTCOME MEASURES

The main outcome was transferred to RAC on discharge from hospital. We calculated ORs for sociodemographic and diagnostic factors to determine factors that may impact discharge to RAC.

RESULTS

During the period of data capture, 4406 people were discharged from hospitals to RAC. Discharge to RAC was most strongly associated with diagnoses of progressive neurological and cognitive disorders. Acute precipitants of RAC transfer included a broad range of conditions and injuries (eg, Wernicke's encephalopathy, stroke, falls) in the context of issues such as older age, not being partnered (married or de facto), living in areas of lower socioeconomic status, functional issues and the need for palliative care.

CONCLUSIONS

There are multiple intersecting and interacting pathways culminating in discharge from hospital to RAC among younger people with neuropsychiatric disorders. Improved capacity for interdisciplinary home care and alternative housing and support options for people with high support needs are required.

Hospital service utilisation of people previously hospitalised with different subtypes of psychotic disorder: A record linkage study

OBJECTIVE

Little research has examined the physical and mental comorbidities, and health service use patterns, of people diagnosed with psychotic disorder subtypes other than schizophrenia spectrum disorders. This study aims to examine the physical and mental comorbidities, and subsequent hospital service use patterns, of individuals previously hospitalised with various psychotic disorder subtypes using linked health service data.

METHODS

We included individuals hospitalised with a psychotic disorder in New South Wales, Australia, between 1 July 2002 and 31 December 2014 (N = 63,110). We examined the demographic profile of the cohort and rates of subsequent acute hospital care and ambulatory mental health service use. We compared the rates of subsequent hospital admissions, emergency department presentations and ambulatory mental health treatment days of people hospitalised with different psychotic disorder subtypes to people hospitalised with schizophrenia spectrum disorders using Poisson regression.

RESULTS

People most recently hospitalised with mood/affective disorders and psychotic symptoms had a higher rate of subsequent hospital admissions than those most recently hospitalised with schizophrenia spectrum and delusional disorders (adjusted incident rate ratio = 1.06; 95% confidence interval = [1.02, 1.10]), while people most recently hospitalised with drug-induced and other organic (adjusted incident rate ratio = 1.19; 95% confidence interval = [1.12, 1.27]) and acute psychotic disorders (adjusted incident rate ratio = 1.10; 95% confidence interval = [1.03, 1.18]) had more subsequent emergency department presentations than those most recently hospitalised with schizophrenia spectrum and delusional disorders. All three groups had fewer subsequent mental health ambulatory days than those most recently hospitalised with schizophrenia spectrum and delusional disorders (adjusted incident rate ratios = 0.85-0.91).

CONCLUSION

The health profiles and subsequent hospital service use patterns of people previously hospitalised with different psychotic disorder subtypes are heterogeneous, and research is needed to develop targeted health policies to meet their specific health needs.

The health service contact patterns of people with psychotic and non-psychotic forms of severe mental illness in New South Wales, Australia: A record-linkage study

OBJECTIVE

To describe and compare the health profiles and health service use of people hospitalised with severe mental illness, with and without psychotic symptoms.

METHODS

We conducted a historical cohort study using linked administrative datasets, including data on public hospital admissions, emergency department presentations and ambulatory mental health service contacts in New South Wales, Australia. The study cohort comprised 169,306 individuals aged 12 years and over who were hospitalised at least once with a mental health diagnosis between 1 July 2002 and 31 December 2014. Of these, 63,110 had a recorded psychotic illness and 106,196 did not. Outcome measures were rates of hospital, emergency department and mental health ambulatory service utilisation, analysed using Poisson regression.

RESULTS

People with psychotic illnesses had higher rates of hospital admission (adjusted incidence rate ratio (IRR) 1.26; 95% confidence interval [1.23, 1.30]), emergency department presentation (adjusted IRR 1.17; 95% confidence interval [1.13, 1.20]) and ambulatory mental health treatment days (adjusted IRR 2.90; 95% confidence interval [2.82, 2.98]) than people without psychotic illnesses. The higher rate of hospitalisation among people with psychotic illnesses was driven by mental health admissions; while people with psychosis had over twice the rate of mental health admissions, people with other severe mental illnesses without psychosis (e.g. mood/affective, anxiety and personality disorders) had higher rates of physical health admissions, including for circulatory, musculoskeletal, genitourinary and respiratory disorders. Factors that predicted greater health service utilisation included psychosis, intellectual disability, greater medical comorbidity and previous hospitalisation.

CONCLUSION

Findings from this study support the need for (a) the development of processes to support the physical health of people with severe mental illness, including those without psychosis; (b) a focus in mental health policy and service provision on people with complex support needs, and (c) improved implementation and testing of integrated models of care to improve health outcomes for all people experiencing severe mental illness.

Reviewing causes of death of individuals with intellectual disability in New South Wales, Australia: a record-linkage study

BACKGROUND

People with intellectual disability (ID) have a much higher mortality rate than the general population. To reduce the rate of mortality of people with ID, it is critical that causes of death are properly understood, recorded and reported. Formal reviews of causes of death are used in some countries to ensure that causes of death are accurate. To date, the impact of these formal reviews on understanding causes of death of people with ID has not been quantified.

METHODS

The study aimed to quantify the impact of formal reviews of deaths on the understanding of causes of death of people with ID who died while living in residential care. Individuals (851) with ID who died in residential care in New South Wales (NSW), Australia, between 1 December 2002 and 31 December 2013, who had a cause of death recorded in both the NSW Cause of Death Unit Record File (COD-URF; cause of death recorded at time of death) and NSW Ombudsman dataset (cause of death recorded after in-depth review) were included in the study. We assessed agreement in coding for cause of death by comparing the International Classification of Diseases 10th Revision (ICD-10) codings at three levels of diagnostic specificity, for both underlying and additional causes of death. We conducted our analysis through both descriptive comparison and through two boosted regression trees.

RESULTS

Approximately half of the underlying causes of death were different after review by the NSW Ombudsman compared with the COD-URF. Certain causes of death (determined by ICD-10 chapter) were less likely to predict matches between the dataset than others, with individuals with mental, behavioural and neurodevelopmental disorders recorded in the COD-URF least likely to have a matching cause of death in NSW Ombudsman dataset. For deaths where there was no agreement at any level between the datasets, a high level of unknown causes of death was recorded.

CONCLUSIONS

Formal review of deaths of people with ID in residential care is important to determining true causes of death and therefore developing appropriate health policy for people with ID.

Protection from uncertainty in the exploration/exploitation trade-off

The exploration/exploitation trade-off (EE trade-off) describes how, when faced with several competing alternatives, decision-makers must often choose between a known good alternative (exploitation) and one or more unknown but potentially more rewarding alternatives (exploration). Prevailing theory on how humans perform the EE trade-off states that uncertainty is a major motivator for exploration: the more uncertain the environment, the more exploration that will occur. The current article examines whether exploratory behavior in both choice and attention may be impacted differently depending on whether uncertainty is onset suddenly (unexpected uncertainty), or more slowly (expected uncertainty). It is shown that when uncertainty was expected, participants tended to explore less with their choices, but not their attention, than when it was unexpected. Crucially, the impact of this "protection from uncertainty" on exploration only occurred when participants had an opportunity to learn the structure of the task before experiencing uncertainty. This suggests that the interaction between uncertainty and exploration is more nuanced than simply more uncertainty leading to more exploration, and that attention and choice behavior may index separate aspects of the EE trade-off. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Out of fright, out of mind: impaired memory for information negated during looming threat

People often need to update representations of information upon discovering them to be incorrect, a process that can be interrupted by competing cognitive demands. Because anxiety and stress can impair cognitive performance, we tested whether looming threat can similarly interfere with the process of updating representations of a statement's truthfulness. On each trial, participants saw a face paired with a personality descriptor. Each pairing was followed by a signal indicating whether the pairing was "true", or "false" (a negation of the truth of the statement), and this signal could be followed by a warning of imminent electric shock (i.e., the looming threat). As predicted, threat of shock left memory for "true" pairings intact, while impairing people's ability to label negated pairings as untrue. Contrary to our predictions, the pattern of errors for pairings that were negated under threat suggested that these mistakes were at least partly attributable to participants forgetting that they saw the negated information at all (rather than being driven by miscategorization of the pairings as true). Consistent with this, linear ballistic accumulator modelling suggested that this impaired recognition stemmed from weaker memory traces rather than decisional processes. We suggest that arousal due to looming threat may interfere with executive processes important for resolving competition between mutually suppressive tags of whether representations in memory are "true" or "false".

Constraints on Dark Matter Properties from Observations of Milky Way Satellite Galaxies

We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and marginalizes over uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk. Our results are consistent with the cold, collisionless DM paradigm and yield the strongest cosmological constraints to date on particle models of warm, interacting, and fuzzy dark matter. At 95% confidence, we report limits on (i) the mass of thermal relic warm DM, m_{WDM}>6.5  keV (free-streaming length, λ_{fs}≲10h^{-1}  kpc), (ii) the velocity-independent DM-proton scattering cross section, σ_{0}<8.8×10^{-29}  cm^{2} for a 100 MeV DM particle mass [DM-proton coupling, c_{p}≲(0.3  GeV)^{-2}], and (iii) the mass of fuzzy DM, m_{ϕ}>2.9×10^{-21}  eV (de Broglie wavelength, λ_{dB}≲0.5  kpc). These constraints are complementary to other observational and laboratory constraints on DM properties.

Cosmological Constraints from Multiple Probes in the Dark Energy Survey

The combination of multiple observational probes has long been advocated as a powerful technique to constrain cosmological parameters, in particular dark energy. The Dark Energy Survey has measured 207 spectroscopically confirmed type Ia supernova light curves, the baryon acoustic oscillation feature, weak gravitational lensing, and galaxy clustering. Here we present combined results from these probes, deriving constraints on the equation of state, w, of dark energy and its energy density in the Universe. Independently of other experiments, such as those that measure the cosmic microwave background, the probes from this single photometric survey rule out a Universe with no dark energy, finding w=-0.80_{-0.11}^{+0.09}. The geometry is shown to be consistent with a spatially flat Universe, and we obtain a constraint on the baryon density of Ω_{b}=0.069_{-0.012}^{+0.009} that is independent of early Universe measurements. These results demonstrate the potential power of large multiprobe photometric surveys and pave the way for order of magnitude advances in our constraints on properties of dark energy and cosmology over the next decade.

Wide-Field Lensing Mass Maps from Dark Energy Survey Science Verification Data

We present a mass map reconstructed from weak gravitational lensing shear measurements over 139  deg2 from the Dark Energy Survey science verification data. The mass map probes both luminous and dark matter, thus providing a tool for studying cosmology. We find good agreement between the mass map and the distribution of massive galaxy clusters identified using a red-sequence cluster finder. Potential candidates for superclusters and voids are identified using these maps. We measure the cross-correlation between the mass map and a magnitude-limited foreground galaxy sample and find a detection at the 6.8σ level with 20 arc min smoothing. These measurements are consistent with simulated galaxy catalogs based on N-body simulations from a cold dark matter model with a cosmological constant. This suggests low systematics uncertainties in the map. We summarize our key findings in this Letter; the detailed methodology and tests for systematics are presented in a companion paper.

Ticks and associated diseases: a retrospective review

This is a retrospective review of contributions to the understanding of ticks and associated diseases published in Medical and Veterinary Entomology since its first issue. It highlights the large and significant changes in the style and conduct of this field over the last 25 years. The selected papers refer to disease-related categories of host immunity to ticks, population dynamics, pathogen transmission and tick control.

Nutritional status and food security in Sub-Saharan Africa: Predictions for 2020

The subject of the future regarding nutritional status and food security, and of their ramifications in terms of nutrition-related disorders/diseases in Sub-Saharan African (SSA) populations, is a complex one. As well as social unrest, a country's socioeconomic situation may affect food availability and, crucially, influence the generally low proportions of the Gross National Product devoted to health services. Additional determinants include changes in the roles of non-dietary adverse factors (i.e. smoking practice, alcohol consumption, physical inactivity) and of infections (i.e. gastroenteritis, malaria, tuberculosis and, particularly, HIV). As to future health in 2020, major increases in socioeconomic status are very unlikely; in fact, there has been a deterioration in some countries with food shortages affecting nutrition status and food security. However, with some measures of prosperity there are likely to be decreases in family size and falls in the proportions of children born with low birthweights or with protein-energy-malnutrition (PEM), and of children lying under the 5th percentile of growth reference standards. Simultaneously, though. there will be variable rises, especially in urban dwellers, in the occurrence of hypertension, diabetes, cardiovascular disease and certain cancers. Improvements in the health status of both children and adults are likely to be strongly affected by whether HIV infection can be controlled or whether it becomes rampant.

Genotypic diversity, a survival strategy for the apicomplexan parasite Theileria parva

The tick-borne protozoan parasite Theileria parva causes East Coast fever (ECF), a severe lymphoproliferative disease of cattle that is a major constraint to the improvement of livestock in eastern, central and southern Africa. Studies in cattle experimentally infected with T. parva have shown that the protective cytotoxic T lymphocyte (CTL) response is tightly focused, with individual animals recognizing only one or two dominant antigens, the identity of which varies with MHC class I phenotype. It is well known that cross-protection between T. parva stocks is limited, but precise evaluation of genetic diversity in field populations of the parasite has been hampered by a lack of molecular markers spanning the genome. A recently described panel of satellite markers has provided evidence for substantial genotypic diversity and recombination but does not provide cover for large segments of the genome. To address this deficiency, we undertook to identify additional polymorphic markers covering these regions and we report herein 42 newly identified PCR-RFLP markers distributed across the 4 T. parva chromosomes, as well as 19 new satellite markers for chromosomes 1 and 2. This brings the total number of available polymorphic markers to 141 for the 8.5 Mb genome. We have used these markers to characterise existing parasite stabilates and have also shown that passage of the parasite through naïve cattle and ticks can lead to substantial changes of parasite populations in resulting stabilates. These markers have also been used to show that passage of mixed parasites through an immunised calf results in the removal of the immunising genotype from the parasite population produced by ticks fed on this animal.

Endophytic actinobacteria induce defense pathways in Arabidopsis thaliana

Endophytic actinobacteria, isolated from healthy wheat tissue, which are capable of suppressing a number wheat fungal pathogens both in vitro and in planta, were investigated for the ability to activate key genes in the systemic acquired resistance (SAR) or the jasmonate/ethylene (JA/ET) pathways in Arabidopsis thaliana. Inoculation of A. thaliana (Col-0) with selected endophytic strains induced a low level of SAR and JA/ET gene expression, measured using quantitative polymerase chain reaction. Upon pathogen challenge, endophyte-treated plants demonstrated a higher abundance of defense gene expression compared with the non-endophyte-treated controls. Resistance to the bacterial pathogen Erwinia carotovora subsp. carotovora required the JA/ET pathway. On the other hand, resistance to the fungal pathogen Fusarium oxysporum involved primarily the SAR pathway. The endophytic actinobacteria appear to be able to "prime" both the SAR and JA/ET pathways, upregulating genes in either pathway depending on the infecting pathogen. Culture filtrates of the endophytic actinobacteria were investigated for the ability to also activate defense pathways. The culture filtrate of Micromonospora sp. strain EN43 grown in a minimal medium resulted in the induction of the SAR pathway; however, when grown in a complex medium, the JA/ET pathway was activated. Further analysis using Streptomyces sp. strain EN27 and defense-compromised mutants of A. thaliana indicated that resistance to E. carotovora subsp. carotovora occurred via an NPR1-independent pathway and required salicylic acid whereas the JA/ET signaling molecules were not essential. In contrast, resistance to F. oxysporum mediated by Streptomyces sp. strain EN27 occurred via an NPR1-dependent pathway but also required salicylic acid and was JA/ET independent.

Cloned Theileria parva produces lesser infections in ticks compared to uncloned T. parva despite similar infections in cattle

Experimental transmissions of cloned Theileria parva in cattle with Rhipicephalus appendiculatus ticks were compared to transmissions with uncloned T. parva during studies on the potential for genetic recombination during syngamy of Theileria to produce antigenic diversity for evasion of bovine immunity. Prevalence and abundance of T. parva infection in adult ticks, which resulted from the feeding of nymphs on the calves, were significantly higher in the uncloned compared to the cloned T. parva. Development of sporoblasts of T. parva in the ticks to produce infective sporozoites was similar. There was no statistically significant difference in the clinical course of infection in cattle between cloned and uncloned T. parva. It was concluded that cloned T. parva has characteristics that reduce its viability during the tick stages of its life cycle.

Validation of the Proposed International Society for Heart and Lung Transplantation Grading System for Primary Graft Dysfunction After Lung Transplantation

BACKGROUND

A scoring system was recently proposed to grade the severity of primary graft dysfunction (PGD), a frequent early complication of lung transplantation. The purposes of this study are to: (1) validate the PGD grading system with respect to patient outcomes; and (2) compare the performance of criteria employing the arterial oxygenation to fraction of inspired oxygen (P/F) ratio to an alternative grading system employing the oxygenation index (OI).

METHODS

We retrospectively reviewed the medical records of 402 patients having undergone lung transplantation at our institution from 1992 through 2004. The ISHLT PGD grading system was modified and grades were assigned up to 48 hours post-transplantation as follows: Grade 1 PGD, P/F > 300; Grade 2, P/F 200 to 300; and Grade 3, P/F < 200. A worst score T(0-48) was also assigned, which reflects the highest grade recorded between T0 and T48.

RESULTS

The prevalence of severe PGD (P/F Grade 3) declined after transplant, from 25% at T0 to 15% at T48. Grouping patients by P/F grade at T48 demonstrated the clearest differentiation of 90-day death rates (Grade 1, 7%; Grade 2, 12%; Grade 3, 33%) (p = 0.0001). T48 OI grade also differentiates 90-day death rates. There was no difference in longer-term survival between patients with PGD Grades 1 and 2. OI grade at T0 qualitatively improved differential mortality between Grades 1 and 2; however, the differences did not reach statistical significance. Patients with a worst score T(0-48) of Grade 3 PGD did have significantly decreased long-term survival, as well as longer ICU and hospital stay, when compared with Grades 1 and 2 PGD. Significant risk factors for short- and long-term mortality in our multivariate model were P/F Grade 3 [worst score T(0-48) as well as T0 grade], single-lung transplant, use of cardiopulmonary bypass and high pre-operative mean pulmonary artery pressure.

CONCLUSIONS

There is an increased risk of short- and long-term mortality and length of hospital stay associated with severe (Grade 3) PGD. The proposed ISHLT grading system can rapidly identify patients with poor outcomes who may benefit from early, aggressive treatment. Refinement of the scoring system may further improve patient risk stratification.

The known distribution and ecological preferences of the tick subgenus Boophilus (Acari: Ixodidae) in Africa and Latin America

A compilation of the known distribution of Boophilus ticks in Africa and Latin America is presented, together with details on climate preferences. B. annulatus is recorded mainly in the western part of a strip from the equator to parallel 20 degrees N. It associates with woodlands and forests (lowland rain forest and secondary grassland). This species is also present in the Mediterranean region, associated to woodland and open areas. B. decoloratus extends southern to parallel 20 degrees N, in woodland with montane vegetation and Zambezian miombo; some records have been collected in the highveld grassland. B. geigyi is mainly collected in the western range of a stripe extending between parallels 5 degrees N and 18 degrees N, associated with Sudanian woodland, lowland rain forest with secondary grassland and woodland. Confirmed records of microplus in Africa are restricted to Malagasy region and south and eastern Africa, being predominant in the Zambezian miombo, deciduous forest with secondary grassland, and woodland. In Latin America, microplus is abundant in the Mesoamerican corridor to Venezuela and Colombia, and southern in Brazil and Argentina. The tick is mainly associated to the biomes of Chaco and Pampas in Argentina, the North-central moist Andes, the Atlantic forest (southern range) and the moist Meso-American vegetation (northern range). Most collections of B. annulatus and B. geigyi came from areas where winter minimum temperature is above 15 degrees C, maximum temperatures remain between 33 and 36 degrees C and maximum rainfall is recorded between June and September. B. decoloratus and African B. microplus are recorded in sites with low temperatures in May-September. Minimum temperature requirements are similar for both B. decoloratus and African B. microplus, and both are around 4 degrees C less than the value recorded for collections of Latin-American B. microplus. The rainfall pattern observed for decoloratus shows a minimum in May and June. The requirements of total rainfall are highest for B. microplus in Latin America, while records of African B. microplus are concentrated in areas of low rainfall between May and October, and high rainfall between November and March (low rainfall in the same period for B. decoloratus). Statistical analysis revealed the existence of populations (demes) with ecologically different requirements within each tick species. Both B. annulatus and B. decoloratus showed many different demes clearly associated to defined areas. The collections of Latin American B. microplus are very homogeneous according climate preferences and well separated from the African counterpart.

Outcomes of febrile children presumed to be immunocompetent who present with leukopenia or neutropenia to an ambulatory setting

To determine significant medical outcomes in febrile children presenting to an ambulatory setting with neutropenia and/or leukopenia.

METHODS

Retrospective medical record review conducted on febrile patients who had a blood culture drawn, with white blood cell counts less than 5,000/mm3 and/or an absolute neutrophil count less than 1000/mm3. Ninety-one patients were identified; 5 with positive blood culture results, 13 with significant non-oncologic disease, and 3 patients with leukemia who had involvement of 2 or more cell lines.

CONCLUSIONS

In the majority of patients, clinical judgment, physical findings, and review of all cell lines of the complete blood cell count identified those with significant disease.

Ticks associated with wild mammals in Ghana

The host ranges of a collection of 21 tick species found on wild mammals in the savanna, forests and coastal zone of Ghana suggested that most species were adapted to feeding mainly on host species within a single mammalian order, i.e. on artiodactyls (bovids/suids), carnivores, rodents or pholidotes (pangolins). Only a few species were dispersed evenly across a range of orders. Seven out of ten of the most common ticks on forest mammals were significantly associated with a particular host species or a group of closely related host species, which could be viewed as their major host or hosts, but they were also recorded much less frequently on a wide range of host species. Two other species were confined to their major hosts. Only one species appeared to be widely dispersed on forest mammals and to lack a particular major host. The majority of tick species therefore occurred on hosts with very distinctive biological, behavioural and ecological characteristics. The study provided no evidence to support the view that host specificity is an artefact of sampling. Finding that the tick species on Ghanaian wild mammals occurred on particular hosts, as well as in distinct habitats, indicated that tick-host associations are important for tick survival and confirmed the importance of climate and vegetation in tick distribution.

Incidence and prevalence of tick-borne haemoparasites in domestic ruminants in Ghana

Giemsa-stained thin blood smears prepared monthly from cattle, sheep and goats in the Greater Accra region of Ghana between May 1994 and December 1996 were examined for presence of tick-borne haemoparasites. The majority of animals were less than 2 months old at the start of the survey. Monthly and cumulative incidences are presented of Anaplasma sp., Babesia bigemina, Borrelia sp., Eperythrozoon sp., Theileria mutans and Theileria velifera in cattle, Anaplasma sp., Borrelia sp., and Theileria sp. in sheep, and Anaplasma sp. in goats. T. mutans was the commonest parasite in cattle, with 100% incidence in calves by 10 months of age, and Anaplasma was commonest in small ruminants. The relative prevalence of these haemoparasites in blood smears from cattle, sheep and goats sampled on a single occasion at sites in all 10 regions of Ghana was found to be similar, though actual infection rates were lower. Packed cell volume (PCV) measurements from the sampled animals are also presented; no seasonal trends were evident in the PCV of the cattle, sheep and goats sampled monthly. In animals sampled on a single occasion, mean PCV was significantly higher in cattle and sheep without detectable haemoparasite infection, and in cattle was lowest in animals positive for both Babesia and Anaplasma, while there was no difference in mean PCV levels between parasitised and non-parasitised goats.

Ehrlichia ruminantium seroprevalence in domestic ruminants in Ghana. II. Point prevalence survey

Serum samples collected on a single occasion from cattle, sheep and goats at sites in all 10 regions of Ghana were tested for antibodies to Ehrlichia (previously Cowdria) ruminantium, the causative agent of heartwater, by polyclonal competitive ELISA (PC-ELISA). The survey revealed the presence of heartwater-exposed ruminants throughout the country, with local seroprevalence up to 100%. Seronegative, and therefore presumably susceptible, animals were also present in all regions, in some areas in numbers high enough to indicate local endemic instability. Overall seroprevalences in cattle, sheep and goats were 61, 51 and 28% respectively, and were generally higher in the northern part of the country and lower in the forest zone. Amongst animals over 1 year old, two thirds of cattle and sheep, and around one third of goats throughout the country had been exposed to E. ruminantium. In the north, seroprevalence in sheep sampled with and without cattle was similar, whereas in the south seroconversion rates in sheep were significantly higher in areas where cattle were present.

Ehrlichia ruminantium seroprevalence in domestic ruminants in Ghana; I. Longitudinal survey in the Greater Accra Region

Serum samples collected monthly over a 34-month period from cattle, sheep and goats in the Greater Accra Region of Ghana were tested for antibodies to Ehrlichia (previously Cowdria) ruminantium, the causative agent of heartwater, by polyclonal competitive ELISA (PC-ELISA). Maternal antibodies, detected in about half of animals followed from under 1 month old, declined to negative levels within 2-4 months. Amblyomma variegatum tick vectors were present on livestock in rural areas throughout the year, and first seroconversion occurred at any age, although the majority of calves seroconverted between 1 and 10 months old, sheep by 11 months, and goats by 7 months. All the cattle in the study became seropositive by 20 months of age, except one animal which subsequently died of heartwater. Following seroconversion, 25% of bovine sera tested negative in the PC-ELISA. Just over half the sheep in the survey seroconverted before or during the study period; following seroconversion, less than 3% of ovine sera became PC-ELISA negative. About a quarter of the goats seroconverted, and 34% of their post-seroconversion sera tested negative in the PC-ELISA. Overall, the serology indicated that virtually all cattle on the survey farms were exposed to E. ruminantium without suffering disease, but that a substantial proportion of sheep and goats escaped exposure and thus formed a susceptible population. E. ruminantium was detected in brains of 14, 36 and 4% of cattle, sheep and goats submitted for post mortem at the Accra Veterinary Laboratory, indicating that sheep were most at risk from heartwater disease.

An updated list of the ticks of Ghana and an assessment of the distribution of the ticks of Ghanaian wild mammals in different vegetation zones

Twenty one species of ticks belonging to five genera of the family Ixodidae (Order Acari, sub-order Ixodida) - Amblyomma, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus (including the sub-genus Rhipicephalus (Boophilus)) - were collected from 1260 mammals, representing 29 species, 14 families and 6 orders, in four vegetation zones in Ghana during the period 1971-1978. Four other species were collected from humans in 1977. In all, eight species appeared to be new records for Ghana: Amblyomma tholloni Neumann; Dermacentor circumguttatus Neumann; Haemaphysalis houyi Nuttall & Warburton; Ixodes loveridgei Arthur; Ixodes oldi Nuttall; Ixodes vanidicus Schultze; Rhipicephalus complanatus Neumann; Rhipicephalus cuspidatus Neumann. The updated list of tick species in Ghana given here includes 41 species of ixodid ticks and four species of argasid ticks. Most species have been found in neighbouring regions of West Africa but 56 of the 121 different combinations of ixodid tick species and host species found in the collection described here have not apparently been reported before. The new combinations recorded here bring the total number of different combinations of ixodid tick species and mammalian host species now reported in Ghana to 151. The tick species found on wild mammals in Ghana mostly differed from those reported from domestic stock by other authors. The data showed that different tick species occurred in different vegetation zones and that most species displayed a pronounced preference for certain groups of related host species. Some tick species were found in the savanna feeding mainly on large bovids and/or suids; others were found in forests feeding mainly on small bovids, large rodents or small carnivores.

Some puzzling situations in the onset, occurrence and future of coronary heart disease in developed and developing populations, particularly such in sub-Saharan Africa

Coronary heart disease (CHD) was rare in developed populations until the early 1900s; this prevailed even among the small segments who were prosperous and who, in measure, had most of the currently recognised risk factors. However, in the 1930s, with improved circumstances from general rises in socio-economic state, there were major increases in the occurrence and mortality rate from the disease, the latter reaching a third of the total mortality in some countries, as in the United Kingdom (UK). Puzzlingly, the inter-population diversity of the increases in CHD has been such that there are as much as five fold differences in CHD mortality rates, as, for example, between Poland and Spain. Within recent years, with appropriate treatments, the mortality rate has halved in some countries, again, as in the UK. However, the incidence rate of the disease has diminished little or hardly at all. Risk factors include a familial component and, nutritionally, over-eating, a high fat intake, relatively low intakes of plant foods, especially of vegetables and fruit and, non-nutritionally, smoking, excessive alcohol consumption and a low level of everyday physical activity. On the one hand, known risk factors, broadly, are considered to be capable of explaining only about half of the variation in the occurrence of the disease. Even at present, known risk factors far from fully explain the epidemiological differences in mortality rates. Yet, on the other hand, there is abundant evidence that in population groups, among whom risk factors are low or have been reduced, CHD incidence and mortality rates are lower. Notwithstanding this knowledge, broadly, there is very little interest in the general public in taking avoiding measures. As to the situation in developing populations, in sub-Saharan Africa, in urban Africans, as in Johannesburg, South Africa, despite considerable westernisation of life style and with rises in risk factors, CHD remains of very low occurrence, the situation thereby resembling, historically, its relatively slow emergence in developed populations. In most eastern countries, mortality rates remain relatively low, as in Russia and Japan. However, in major contrast, in India, rates have risen considerably in urban dwellers. Indeed, in Indian immigrants, as in those in the UK, their rate actually exceeds that in the country's white population. In brief, much remains to be explained in the epidemiology of the disease.

The feeding behaviour and Plasmodium infection of Anopheles mosquitoes in southern Ethiopia in relation to use of insecticide-treated livestock for malaria control

Anopheles arabiensis and An. quadriannulatus species B mosquitoes were collected at sites of human and livestock housing and analysed for blood feeding patterns and infection with malaria sporozoites. A low percentage of human blood meals at some sites suggested that zooprophylaxis could be effective in reducing challenge from Plasmodium falciparum.

World pandemic of obesity: the situation in Southern African populations

Among sub-Saharan Africans in general, a generation or so ago, there was very little gain in weight, or in blood pressure, with age. Even at present, in most populations, especially in the indigent masses, obesity prevalence remains very low, at 1-5%. However, in South Africa and some neighbouring countries, Botswana, Namibia and Zimbabwe, with rise in socio-economic status, urbanization, and diminishing physical activity, the proportion affected has increased. Rises, as noted in Cape Town, have been only slight in men, to 8%; but in women much more so, to 34%, ie to a level similar to that of African-American women. Dietarily, energy intake has increased slightly, that from fat from 15-20% to 25-30%. However, there have been falls in dietary fibre intake, to 20-25 g and 15-20 g daily, in rural and urban areas, respectively. Evidence suggests that the health disadvantage of obesity in African women is less than that in white women, and would seem to have little influence on their proneness to hypertension, coronary heart disease and breast cancer. Traditionally, and even currently, sociologically, the disorder carries little opprobrium. As to the future, the prevalence in women may well increase still further. Regarding treatment, unfortunately among African women desirous of losing weight, sustained reducing measures are near impossible; moreover, pharmacological treatment is too costly to implement.

A novel plastid-targeted J-domain protein in Arabidopsis thaliana

Arabidopsis cDNAs encoding ATJ11, the smallest known J-domain protein, have been isolated and characterized. The precursor protein of 161 amino acid residues was synthesized in vitro and imported by isolated pea chloroplasts where it was localized to the stroma and cleaved to a mature protein of 125 amino acid residues. The mature protein consists of an 80 amino acid J-domain, and N- and C-terminal extensions of 24 and 21 amino acid residues, respectively, which show no similarity to regions in other DnaJ-related proteins. ATJ11 produced in Escherichia coli stimulated the weak ATPase activity of E. coli DnaK, but was unable to stimulate refolding of firefly luciferase by DnaK, and inhibited refolding by DnaK, DnaJ and GrpE. ATJ11 is encoded by a single-copy gene on chromosome 4, and is expressed in all plant organs examined. A paralogue of ATJ11, showing 72% identity, is encoded in a 4.5 Mb duplication of chromosome 4 on chromosome 2. These proteins represent a novel class of J-domain proteins.

Changes in public health in South Africa from 1876

The present population in South Africa, roughly 43 million inhabitants, is made up of Africans (77.2%), whites (10.5%), Coloureds (mixed race) (8.8%) and Indians (2.5%). In 1900 the infant mortality rate (IMR) among Africans was 330 per 1,000 live births; this has now fallen to 50-60. In Soweto, a primarily African city, IMR averages 20-25. Life expectancy in the past was only 25-30 years; by 1995, this reached 63 years. However, this could fall again due to the rapidly spreading HIV/AIDS epidemic. Life expectancy could fall to 40-45 years by 2010 with the AIDS epidemic being the cause of half of all deaths--a disastrous change from the previous relatively commendable public health situation. Formerly, the most common causes of deaths in young people were infections, diseases associated with malnutrition and gastroenteritis. Adults died almost solely from infections, including typhoid, dysentery, malaria and tuberculosis (TB). Even though diseases associated with malnutrition are less common today, many infections still remain a major problem, particularly TB, which is increasing. As late as 1970, Africans who reached 50 years had longer life expectancy than whites due to the low prevalences of the chronic diseases of lifestyle. This is no longer so, due to the recent rises in non-communicable disorders/diseases, principally obesity in women, hypertension, diabetes, stroke and the cancers of prosperity. In the not so distant future, the level of control of HIV/AIDS related diseases will be the major health/disease regulating factor among Africans. Among white, Coloured and Indian populations, there have been falls in the mortality rates of the young and, despite rises in lifestyle diseases, increases in life expectancy are continuing. For all populations other important public health regulatory factors include water supply, sanitation, clinic/hospital services and personal environmental factors, employment, dietary pattern and intake, smoking practices and alcohol consumption and physical activity, particularly in urban dwellers. Unfortunately, public health expenditure, also a highly regulating factor, has fallen from 8.2% of the gross domestic product in 1994 to 4.1% in 2000.

Acute hemorrhagic complication of diagnostic lumbar puncture

OBJECTIVE

To present a case of an epidural hematoma after lumbar puncture in a pediatric patient without known risk factors for such a complication and to review the literature regarding this complication.

DESIGN

Case report, review of the literature, and discussion.

DATA SOURCES

A review of MEDLINE (1966-1998) for keywords "lumbar puncture" and "hemorrhage" or "hematoma" was conducted, and each bibliography was reviewed for other sources extending to 1911. Articles describing a case of spinal hematoma after a lumbar puncture for any procedure were included.

RESULTS

A 5-year-old boy underwent a lumbar puncture for evaluation of lethargy and fever, and subsequently developed marked back pain and severe pain on flexion of his legs. Magnetic resonance imaging revealed an epidural blood collection. The patient's symptoms resolved over the next few days in association with steroid administration. Multiple reports of epidural and subdural hematomas were found on literature review, most occurring in the setting of coagulation abnormalities. These reports involve lumbar puncture in anesthetic, interventional, and diagnostic settings.

CONCLUSION

Lumbar puncture is a frequently employed procedure. Known complications include epidural, subdural, and subarachnoid hemorrhage, usually in the setting of abnormal coagulation. The case presented is unusual in that the patient is a child and lacks any known risk factors for a hemorrhagic complication. Such a complication appears to be rare; only five of the 64 cases discovered in the literature review occurred following this diagnostic procedure in patients without known risk factors.

Risk factors in habitats of the tick Ixodes ricinus influencing human exposure to Ehrlichia phagocytophila bacteria

Ixodes ricinus L. (Acari: Ixodida) were sampled during 1996-99 in southern Scotland, on vegetation using cloth drags, on humans by removal from clothing and on roe deer (Capreolus capreolus L.) by searching legs of culled deer. Developmental microclimate was recorded by automatic recorders and questing microclimate by portable instruments during tick collections. Ticks and deer were examined for infection with Ehrlichia phagocytophila bacteria (Rickettsiales) using microscopy and polymerase chain reaction. This pathogen causes tick-borne fever of sheep in Europe and human granulocytic ehrlichiosis in North America, but in Europe human clinical ehrlichiosis due to E. phagocytophila has not been recorded despite serological evidence of exposure. Among three types of habitat, coniferous woodland was most infested with questing ticks (560 ticks/km of drag; mean numbers collected on long trousers: 24.3 larvae, 13.5 nymphs and 0.8 adult ticks/km walked), deciduous woodland had slightly lower infestation (426 ticks/km drag) and upland sheep pasture had much lower infestation (220 ticks/km drag). Of the three main vegetation types, bracken was least infested (360 ticks/km drag), ericas most (430 ticks/km drag) and grassland had intermediate infestation density (413 ticks/km drag). Questing and developmental microclimates were poor predictors of exposure within these habitats, except lower infestation of pastures was attributed to greater illumination there. Collectors who walked a total of 300 km through all habitats (taking 360 h in all seasons), wearing cotton trousers hanging outside rubber boots, were bitten by only four nymphs and 11 larvae of I. ricinus (but no adult ticks). There was a negative correlation between densities of deer and ticks collected, although presence of deer remains a major indicator of exposure. The proportion of infected ticks was fairly uniform at four sites studied. Overall prevalence of E. phagocytophila in I. ricinus was 3.3% in nymphs (40/1203) but only approximately 1.5% in adults of both sexes (although males do not bite). It was estimated that nymphs of I. ricinus gave 4.4% probability of one infected bite/person/year (for occupational exposure during this research) due to presence in all seasons and habitats, their human biting rate of 0.011 nymphs/h or 0.013 nymphs/km and widespread infection with E. phagocytophila. The frequency distribution of intensity of infection in ticks was approximately normal (mean 98 morulae/nymph infected), thus there is a high risk of receiving a high dose from any one infected tick bite.

With increasing ageing in Western populations, what are the prospects for lowering the incidence of coronary heart disease?

Coronary heart disease (CHD), rare in the early 1900s, in the 1970s was responsible for almost a third of deaths in Western populations. Although its mortality rate has fallen in the last 20 years, considerably in certain populations, it remains the leading cause of death, and there is little evidence of any fall in its incidence rate. The primary risk factors, which include pattern of diet, smoking practice, and level of physical activity, are well known, but explain only approximately 50% of variation in its occurrence. Despite the numerous health improvement recommendations made, alterations in diet have been relatively slight. Although smoking practice has halved in some populations, its prevalence is now rising in the young. The extent of physical activity is low, compared with that in the past, and may even be decreasing in the young. With the general ageing of populations, the near absence of strong encouragement from the state, and individuals' general failure to reduce risk factors significantly, the chances of decreases in the incidence of CHD appear remote.

Tick-Theileria interactions in response to immune activation of the vector

Watt, D. M., Walker, A. R., Lamza, K. A., and Ambrose, N. C. 2001. Tick-Theileria interactions in response to immune activation of the vector. Experimental Parasitology 97, 89-94. Immune mechanisms towards the haemoprotozoan parasite Theileria parva were investigated in their tick vector, Rhipicephalus appendiculatus. The exoskeletons of adult ticks were initially pierced with bacteria-coated, saline-coated, or sterile dry glass needles. Haemolymph was extracted from the ticks at 6, 24, 48, and 72 h postinjection and applied to bacterial plates to measure the growth inhibition effects. The inhibition zones were larger with all the injected groups compared to uninjected controls. The largest inhibition zones were seen 24 h after injection with bacteria-coated needles. An experiment was carried out to investigate whether antibacterial immune responses were relevant to the parasite/tick relationship and, if so, which parasite form was most vulnerable. R. appendiculatus nymphs were infected with T. parva by feeding on an infected calf and were then injected with needles on days 7, 13, 15, and 17 throughout their moult in an attempt to induce tick immune responses at the same time as different lifecycle forms of T. parva would be present. Salivary glands from the moulted adult ticks in the control and different treatment groups were dissected out and examined for the presence of T. parva sporoblasts. No difference in infection levels was seen in any of the treatment groups compared with the controls, suggesting that immune responses in R. appendiculatus, induced by bacterial injection, do not affect T. parva infections. The fecundity of injected ticks was compared with that of uninjected controls to ensure that the injection procedure itself was not detrimental to the ticks. Injected females had higher engorgement masses than controls but reduced levels of egg hatching.

Age structure of a population of Ixodes ricinus (Acari: Ixodidae) in relation to its seasonal questing

Three sites in south west Scotland, each having one deciduous and one coniferous woodland with populations of roe deer, were sampled over three years for Ixodes ricinus Linnaeus ticks using cloth drags. Nymphs and adult ticks were age graded by dissection of gut and Malpighian tubules and staining for lipid with Sudan red. Temperature and relative humidity were recorded in developmental and questing microclimates. Two annual cohorts of both nymphs and adults were found. For both instars one cohort became apparent in early spring and the other in autumn. The timing of the cohorts of nymphs corresponded to peaks of numbers questing, but neither females nor males had any clear seasonal pattern of questing. The maximum life of questing nymphs and adults was three to four months. Nymphs and adults were found questing at all months of the year and at temperatures ranging from 3.5 degrees C to 29.3 degrees C. Questing of larvae in summer peaks of numbers was positively correlated with temperature and negatively correlated with relative humidity. These results are explained by a descriptive model which invokes behavioural and morphogenetic diapause. Tests of the model are discussed and it is proposed that the main adaptive advantage of the complex life cycle is to permit moulting and oviposition to occur at favourable summer temperatures in ticks that have engorged at any time of the year.

Hyponatremic seizures in infancy: association with retinal hemorrhages and physical child abuse?

We present two cases of infants with hyponatremic seizures who had an unexpected finding of retinal hemorrhages. A review of the literature found no prior association between hyponatremic seizures and retinal hemorrhages. The retinal hemorrhages found in the first patient were a result of shaken baby syndrome (SBS) and associated with long bone fractures and a subdural hematoma. The second patient had retinal hemorrhages and cerebral edema, presumed to be a result of SBS. We suggest that children who become hyponatremic owing to neglect, lack of education, or intentional water poisoning may be at risk for other forms of child abuse. Additional research needs to be done to further elucidate the relationship between hyponatremic seizures and child abuse.

The frequency of blood pressure measurements in children in four EDs

The study's objective was to assess the frequency of triage blood pressure measurements in pediatric patients and the recognition of an elevated blood pressure. The design was retrospective and included chart review. The setting consisted of four emergency departments associated with one medical school, including one level I academic center, two level II Community departments, and a regional children's hospital. A convenience sample of 437 patients, aged 1 month to 18 years, was selected. The frequency of triage blood pressure measurements was recorded. The number of patients whose blood pressure was higher than the 90th percentile for age and sex as established by the Second Task Force on Blood Pressure Control in Children was also recorded. The frequency of a second blood pressure measurement in patients with an elevated initial blood pressure was recorded. All frequency data were stratified by hospital and by age group. The results showed 294/437 (66%) of children had blood pressures measured at triage. Of these measurements, 153/294 (52%) reflected blood pressures greater than the 90th percentile for age and sex, but only 58/153 (38%) of patients with such blood pressures had a second blood pressure measured. Hospitals varied in their frequency of blood pressure measurement. Adolescents had their blood pressure measured more frequently, 981105 (93%) than two to 12-year-olds, 144/185 (78%) or 1-month to 2-year-olds, 52/147 (35%). Frequency of triage blood pressure measurements in children varied by institution and increased in frequency with age.