Spatial Distribution Of Cases Research Articles

Epidemiology of Childhood Hyperthyroidism in France: A Nationwide Population-Based Study.

Hyperthyroidism affects all age groups, but epidemiological data for children are scarce. To perform a nationwide epidemiological survey of hyperthyroidism in children and adolescents. A cross-sectional descriptive study. Identification of entries corresponding to reimbursements for antithyroid drugs in the French national insurance database. All cases of childhood hyperthyroidism (6 months to 17 years of age) in 2015. National incidence rate estimated with a nonlinear Poisson model and spatial distribution of cases. A total of 670 cases of childhood hyperthyroidism were identified. Twenty patients (3%) had associated autoimmune or genetic disease, with type 1 diabetes and Down syndrome the most frequent. The annual incidence for 2015 was 4.58/100,000 person-years (95% CI 3.00 to 6.99/100,000). Incidence increased with age, in both sexes. This increase accelerated after the age of 8 in girls and 10 in boys and was stronger in girls. About 10% of patients were affected before the age of 5 years (sex ratio 1.43). There was an interaction between age and sex, the effect of being female increasing with age: girls were 3.2 times more likely to be affected than boys in the 10 to 14 years age group and 5.7 times more likely to be affected in the 15 to 17 years age group. No conclusions about spatial pattern emerged. These findings shed light on the incidence of hyperthyroidism and the impact of sex on this incidence during childhood and adolescence. The observed incidence was higher than expected from the results published for earlier studies in Northern European countries.

Clinical Cysticercosis epidemiology in Spain based on the hospital discharge database: What's new?

BackgroundCysticercosis (CC) is a tissue infection caused by the larval cysts of the pork tapeworm Taenia solium. It is usually acquired by eating contaminated food or drinking water. CC Cysts can develop in the muscles, the eyes, the brain, and/or the spinal cord. T. solium is found worldwide, but its prevalence has decreased in developed countries due to stricter meat inspection and better hygiene and sanitation. Nevertheless, CC is still a leading cause of seizures and epilepsy. In Spain, The disease is not nationally reportable and data on CC infected animals are also missing, despite the European Directive 2003/99/EC.Methodology/Principal findingsWe performed a retrospective descriptive study using the Spanish Hospitalization Minimum Data Set (CMBD). Data with ICD-9 CM cysticercosis code (“123.1”) placed in first or second diagnostic position from 1997 to 2014 were analyzed. Hospitalization rates were calculated and clinical characteristics were described. Spatial distribution of cases and their temporal behavior were also assessed. A total of 1,912 hospital discharges with clinical cysticercosis were identified. From 1998 to 2008, an increasing trend in the number of CC hospitalizations was observed, decreasing afterwards, in parallel with a decrease in the external migration rate. The Murcia region had the highest median hospitalization rate (13.37 hospitalizations/100,000 population), followed by Navarra and Madrid. The 16–44 age group was the most represented (63.6%). The three most frequent associated diagnoses were epilepsy and convulsions (49.5%), hydrocephalus (11.8%) and encephalitis/myelitis/meningitis (11.6%).Conclusions/SignificanceThere is a need for a common strategy on data collection, monitoring and reporting, which would facilitate a more accurate picture on the CC epidemiological scenario. Even if most cases might be imported, improving the human and animal CC surveillance will result useful both in gaining extended disease knowledge and reducing morbidity and related-costs.

Risk factors and prediction analysis of cutaneous leishmaniasis due to Leishmania tropica in Southwestern Morocco

Cutaneous leishmaniasis is currently a serious public health problem in northern Africa, especially in Morocco. The causative parasite is transmitted to a human host through the bite of infected female sandflies of the genus Phlebotomus. The objective of the present study is to characterize the causative organisms and to predict the risk of cutaneous leishmaniasis (CL) cases in six provinces in southwestern Morocco, based on the spatial distribution of cases in relation to environmental factors and other risk factors such as socio-economic status and demographics. A molecular study was carried out using ITS1 PCR-RFLP method of the ribosomal DNA of Leishmania. An epidemiological study on CL cases was reported between 2000 and 2016 in this current investigation in six provinces in southwestern Morocco. Statistical analysis was performed using a linear regression model to identify the impact as well as the interaction between all predictor variables on the distribution of CL in the studied provinces. The forecast Holt-Winters (HW) method was used to describe the trend and seasonality of CL cases. The ITS1-PCR- RFLP analysis revealed the presence of Leishmania tropica in all studied provinces. The spatial distribution of CL cases documented in all studied provinces during the sixteen years showed a heterogeneous pattern and fluctuation trend with an average prevalence of 9.92 per 100,000 inhabitants. In addition, the forecast HW model predicts continued variability of trend and seasonality of CL cases in the upcoming years. This study confirmed the importance of socioeconomic factors, in particular poverty and the vulnerability rate, on distribution and emergence of CL. This study revealed a relationship between increasing risk of CL occurrence due to Leishmania tropica, as well as the distribution and emergence thereof, and socioeconomic factors in the investigated area.

Sarcoidosis in an Italian province. Prevalence and environmental risk factors.

Background and aimSarcoidosis is a systemic granulomatous inflammatory disease whose causes are still unknown and for which epidemiological data are often discordant. The aim of our study is to investigate prevalence and spatial distribution of cases, and identify environmental exposures associated with sarcoidosis in an Italian province.MethodsAfter georeferentiation of cases, the area under study was subdivided with respect to Municipality and Health Districts and to the altitude in order to identify zonal differences in prevalence. The bioaccumulation levels of 12 metals in lichen tissues were analyzed, in order to determine sources of air pollution. Finally, the analysis of the correlation between metals and between pickup stations was performed.Results223 patients were identified (58.3% female and 41.7% male of total) and the mean age was 50.6±15.4 years (53.5±15.5 years for the females and 46.5±14.4 for the males). The mean prevalence was 49 per 100.000 individuals. However, we observed very heterogeneous prevalence in the area under study. The correlations among metals revealed different deposition patterns in lowland area respect to hilly and mountain areas.ConclusionsThe study highlights a high prevalence of sarcoidosis cases, characterized by a very inhomogeneous and patchy distribution with phenomena of local aggregation. Moreover, the bioaccumulation analysis was an effective method to identify the mineral particles that mostly contribute to air pollution in the different areas, but it was not sufficient to establish a clear correlation between the onset of sarcoidosis and environmental risk factors.

Deaths by tuberculosis in a priority city for disease control in the Brazilian Northeast: sociodemographic-operational characteristics and vulnerable territories.

Introduction: Incorporating spatial approaches into epidemiological research is a challenge in public health research. The goal in this study was to analyze the spatial distribution of cases of deaths by tuberculosis in Imperatriz – MA (Brazil) and to characterize these events according to sociodemographic and operational characteristics.
 Methods: In this ecological study, all deaths from tuberculosis as the primary cause registered in the Mortality Information System from 2005 to 2014 were considered. The research variables were subject to descriptive analysis, point density analysis (Kernel Intensity Estimation) and area analysis.
 Results: Fifty cases of deaths by TB were identified, particularly the pulmonary clinical form. Male patients were predominant, with a median age of 59 years, mulatto race/color, single, who had finished secondary education. Most deaths happened at the hospital, with medical care before death and without autopsy. Most events happened at the hospital, with medical care delivery by an assistant physician and without autopsy. The point density revealed heterogeneity in the spatial distribution of the deaths, with rates of up to 2.33 deaths/km2. The area analysis by census sector presented age standardized mortality rates of 0.00 to 4.00 deaths/100,000 inhabitants-year.
 Conclusion: The results contributed to the knowledge on the spatial distribution of cases of deaths by Tuberculosis and their characteristics in the research scenario. The importance of space is highlighted as a methodological alternative to support the planning, monitoring and assessment of health actions, targeting interventions to the control of the disease in vulnerable territories.
 Keywords: Tuberculosis; Health Information Systems; Mortality; Spatial analysis.

Mediterranean spotted fever in Spain, 1997-2014: Epidemiological situation based on hospitalization records.

IntroductionMediterranean spotted fever (MSF) is a zoonotic disease caused by Rickettsia conorii. In Spain, deficiencies in the official reporting result in misreporting of this disease. This study aims to describe the clinical and temporal-spatial characteristics of MSF hospitalizations between 1997 and 2014.Materials and methodsWe performed a retrospective descriptive study using the Hospitalization Minimum Data Set (CMBD). All CMBD’s hospital discharges with ICD-9 CM code 082.1 were analyzed. Hospitalization rates were calculated and clinical characteristics were described. Spatial distribution of cases and their temporal behavior were also assessed.ResultsA total of 4,735 hospitalizations with MSF diagnosis were recorded during the study period, out of which 62.2% were male, mean age of 48. Diabetes mellitus, alcohol dependence syndrome, and chronic liver disease occurred in 10.8%, 2.4% and 2.8% hospitalizations, respectively. The median annual hospitalization rate showed a decreasing trend from a maximum of 12.9 in 1997 to a minimum rate of 3.1 in 2014. Most admissions occurred during the summer, showing a significant annual seasonal behavior. Important regional differences were found.DiscussionAlthough MSF hospitalization rates have decreased considerably, it remains a public health problem due to its severity and economic impact. Therefore, it would be desirable to improve its oversight and surveillance.

Modelling H5N1 in Bangladesh across spatial scales: Model complexity and zoonotic transmission risk

Highly pathogenic avian influenza H5N1 remains a persistent public health threat, capable of causing infection in humans with a high mortality rate while simultaneously negatively impacting the livestock industry. A central question is to determine regions that are likely sources of newly emerging influenza strains with pandemic causing potential. A suitable candidate is Bangladesh, being one of the most densely populated countries in the world and having an intensifying farming system. It is therefore vital to establish the key factors, specific to Bangladesh, that enable both continued transmission within poultry and spillover across the human–animal interface. We apply a modelling framework to H5N1 epidemics in the Dhaka region of Bangladesh, occurring from 2007 onwards, that resulted in large outbreaks in the poultry sector and a limited number of confirmed human cases. This model consisted of separate poultry transmission and zoonotic transmission components. Utilising poultry farm spatial and population information a set of competing nested models of varying complexity were fitted to the observed case data, with parameter inference carried out using Bayesian methodology and goodness-of-fit verified by stochastic simulations. For the poultry transmission component, successfully identifying a model of minimal complexity, which enabled the accurate prediction of the size and spatial distribution of cases in H5N1 outbreaks, was found to be dependent on the administration level being analysed. A consistent outcome of non-optimal reporting of infected premises materialised in each poultry epidemic of interest, though across the outbreaks analysed there were substantial differences in the estimated transmission parameters. The zoonotic transmission component found the main contributor to spillover transmission of H5N1 in Bangladesh was found to differ from one poultry epidemic to another. We conclude by discussing possible explanations for these discrepancies in transmission behaviour between epidemics, such as changes in surveillance sensitivity and biosecurity practices.

Inglês

Ischemic heart disease (IHD) are among the leading causes of death in the world and Brazil is one of the developingcountries where occurs more deaths from this cause. Studies indicate that socioeconomic features are related to incidence ofIHD. This study aimed to analyze the spatial distribution of cases of death from IHD that occurred in 2010 in the city of Foz doIguacu-PR, correlating it with variables related to income and literacy. This is an ecological study, based on analysis of secondaryand retrospective data where the units were its 320 urban census sectors. The analysis demonstrated that the specific mortalityrate (SMR) ranged from 0 to >258 deaths per 100,000 inhabitants. The Moran Global analysis identified significant positivespatial autocorrelation of the census sectors according to SMR by IHD, meaning that census sectors with high and low SMR werenot randomly distributed. There was a significant positive correlation of variables 'literacy of responsible' and 'per capita incomeby household' (progressively from 1 to 10 minimum wages). For the variable 'per capita income from ½ to 1 minimum wages'there was no significant correlation. It is concluded that there are census sectors with high SMR by IHD in Foz do Iguacu,especially in Northern, East and West districts of the city and were primarily related to the medium and higher income populationand higher literacy rates, consisting of regions and populations where educational measures of health promotion and lifestylechange incentives, such as physical exercise, should be encouraged aiming at preventing IHD.

Breast Cancer in the Bahamas in 2009-2011.

BACKGROUNDBreast cancer is the most common form of cancer affecting women in the Bahamas, which consists of many islands. This is the first attempt to identify which island has the highest occurrence of breast cancer.OBJECTIVEThe aim of this study was to describe the sociodemographical and spatial features of breast cancer in the Bahamas in 2009–2011.METHODSA review of the medical records of all women with a confirmed diagnosis of breast cancer during the period January 1, 2009–December 31, 2011, was undertaken. Data were first obtained from the National Oncology Board of the Bahamas and validated by a review of the medical records. The patient address was geocoded and mapped using ArcGIS 10.0 Environmental Systems Research Institute (ESRI) to satellite images obtained from The Nature Conservancy in the Bahamas.RESULTSWe recruited 270 patients who satisfied the entry criteria. The cumulative incidences of breast cancer for the years 2009–2011 were 51.4, 45.4, and 51.4, respectively. Breast cancer occurred most often in women of African origin with a mean age at diagnosis of 56.6 ± 13.8 years. Ductal carcinoma was the most common histological type observed with most cancers occurring in Grade II or higher and presenting as late stage (≥ Stage II). Surgery was the preferred method of treatment with modified radical mastectomy being the procedure of choice. Spatial distribution of cases across the Bahamas revealed one cluster, which is present on the island of New Providence. Further analysis of New Providence showed a consistently skewed kernel density in the central and eastern regions, compared with a scattered distribution in the southern and western regions.CONCLUSIONThe island of New Providence had the highest occurrence of breast cancer among all the islands of the Bahamas. The increasing incidence of breast cancer in young women is likely to impose a significant burden on the future of Bahamian health care.

Human subcutaneous/ocular dirofilariasis in the Russian Federation and Belarus, 1997–2013

This study was performed to determine the yearly frequency, trends in spread, and clinical-epidemiological characteristics of human subcutaneous/ocular dirofilariasis (HSOD) in the Russian Federation and Belarus. The surveillance data of HSOD cases occurring between January 1997 and June 2013, obtained from the regional health administrations of the Russian Federation and Belarus, were analyzed. The spatial distribution of cases was assessed using a GIS map, and the clinical-epidemiological characteristics were defined using 719 cases for which information on anatomical location, age, sex, and area of residence was available. The statistical analysis was performed using the Chi-square test. One thousand two hundred and seventy-two clinical cases of HSOD were identified, the majority of them reported in the south-western regions of the Russian Federation. The disease has spread into northern areas, changing its limit from latitude 45°N in 1997 to latitude 61°N in 2013. The statistical analysis of the data showed that the disease is more frequent in the ocular location, in women, in patients aged between 41 and 60 years, and in patients living in urban areas. Alternative sources to the scientific literature could be necessary to assess the epidemiological situation regarding HSOD in some areas where it has become an emerging condition. There is an urgent need for uniform criteria for reporting and retrieving human cases of dirofilariasis.

Generalizing the spatial relative risk function

The spatial relative risk function is defined as the ratio of densities describing respectively the spatial distribution of cases and controls. It has proven to be an effective tool for visualizing spatial variation in risk in many epidemiological applications over the past 20years. We discuss the generalization of this function to spatio-temporal case-control data, and also to situations where there are covariates available that may affect the spatial patterns of disease. We examine estimation of the generalized relative risk functions using kernel smoothing, including asymptotic theory and data-driven bandwidth selection. We also consider construction of tolerance contours. Our methods are illustrated on spatio-temporal data describing the 2001 outbreak of foot-and-mouth disease in the United Kingdom, with farm size as a covariate.

Recent Trends in the Incidence, Geographical Distribution, and Survival From Thyroid Cancer in Wales, 1985–2010

Previous studies of thyroid cancer incidence in Wales have given varying results with suggestions of an excess of cases in geographic areas that were previously exposed to the radioactive fallout from the 1986 Chernobyl nuclear reactor incident. Our objective in this study was to provide an up-to-date comprehensive analysis of time trends in the incidence, geographical distribution, and survival from thyroid cancer in Wales. We identified thyroid cancer cases, registered from 1985 through 2010 in the Welsh Cancer Intelligence and Surveillance Unit (WCISU). Age standardized rates were determined from the European standard population. A Poisson regression model was fitted to assess temporal trends and rate ratios (RRs) and confidence intervals (CIs) were determined and compared across consecutive time periods: 1985-1997 and 1998-2010. Standardized incidence ratios were calculated for each of the 22 local authority areas. Relative survival and Kaplan-Meier curves were computed to analyze all cause and thyroid cancer-specific survival. A total of 1747 thyroid cancer cases were registered from 1985 to 2010. Age standardized incidence rates were 2.8 and 1.2 per 100,000 population per year for females and males respectively. Incidence rates increased with time (RR 1.3 [CI 1.2-1.5], p < 0.001; 1998-2010 vs. 1985-1997). The incidence of papillary cancer increased progressively over the study period (RR 2.22 [CI 1.91-2.57], p < 0.001; 1998-2010 vs. 1985-1997), while rates for other (nonpapillary) histological subtypes remained static (RR 0.95 [CI 0.84-1.08], p = 0.45; 1998-2010 vs. 1985-1997). We identified two geographical areas of increased incidence, but the spatial distribution of cases was inconsistent with exposure to radioactive fallout. Five-year relative survival from all-cause mortality improved from 74.2 [CI 66.8-80.1] in 1985-1989 to 82.6 [CI 77.1-86.9] in 2000-2004, but remained poor for patients over the age of 65 years (p < 0.001, > 65 years vs. 15-64 years) and patients with anaplastic thyroid cancer (p < 0.001; anaplastic vs. other histological varieties). The incidence of thyroid cancer has increased in Wales, predominantly due to an increase in papillary cancers. The current geographical distribution of cases does not support a radiation effect in the region. Survival has remained poor for patients over the age of 65 years and those with anaplastic carcinoma.

Abstract 5028: Epidemiology of childhood leukemia/lymphoma in resource-poor countries: Nature's manifestation of Ludwik Gross's experiments on environmental influence on animal leukemogenesis.

Abstract Epidemiological features of childhood hematological neoplastic diseases (CHND) in resource-poor countries (RPC) that differentiate them from those of affluent countries (AC) include ∼10-fold decreased (DCR) incidence (INC) (x10−5) of common acute lymphoblastic leukemia (c-ALL) subtype, &amp;gt;5-fold increased (ICR) INC of B-ALL subtype/Burkitt's lymphoma (BL), and 20-60-fold ICR INC of chloroleukemia, as well as absence of peak ALL INC among under-5 year olds in RPC (Nigerian data) as compared to AC. To assess lifestyle influences on CHND in an African city, patients (pts) receiving care for CHND at the University College Hospital, Ibadan, Nigeria (IBN) between 9/1982 and 12/1984 underwent routine laboratory assessment and immunophenotypic cell studies, using standard international reagents and indirect fluorescent microscopy. Spatial distribution of cases and disease INC in locales of the city (LC), one of Africa's largest indigenous cities (population 1-2 million), was determined and correlated with lifestyle indices of inhabitants. LC were: central area (75%) lacking in sanitary infrastructure and inhabited by poor illiterate peasant farmers and petty traders (annual income [AI] &amp;lt;$1,000) (zone 1), surrounded by semi-developed area (zone 2) (12.5%), of semi-skilled/literate workers and traders (AI: $1500-$9000) and modern suburbs (zone 3) (12.5%) of educated professionals (AI: &amp;gt;$10,000). In zone 1, BL INC: 1.81-3.62 or &amp;gt;9-fold, AML/AMML± chloroma (CA), INC: 0.41-0.82 or &amp;gt;2-fold, and ALL INC: 0.25-0.50 or 0.3 compared to zone 2+3. BL INC: 0 in zone 3. In zone 1, time-space clustering (TSC) occurred13 times in 35 BL pts, 4 times in 9 AML/AMML±CA pts, but none in ALL. No TSC of BL or AML/AMML±CA, but 3 of ALL in 9 pts occurred in zones 2+3. Conclusion: CHND in IBN is reminiscent of the experiments of Ludwik Gross: following underfeeding of AK mice, a delay in the onset and a reduction in the rate of virus-induced leukemia occurred. Thymectomy inhibited or considerably delayed the development of lymphatic leukemia, and frequently caused the myelogenous forms to appear later in life, often in the form of chloroleukemia. At least, two other hypothetical models have been proposed to explain the pathogenesis of childhood leukemias, including “abnormal immune response to common infection(s)” (Greaves), and “population mixing” (Kinle). There are probably many causes of CHND. Given the high-risk of calorie-malnutrition in zone 1, and the associated risk of maternal and fetal malnutrition causing thymo-lymphatic deficiency, CHND pattern in zone 1 may be Nature's manifestation of the outcome of Gross's experiments, while other models may be relevant for the observation in zones 2+3 of IBN and other RPC. CHND studies in RPC with appropriate technology and reagents could unveil potentials for universal control and prevention of CHND. Citation Format: Christopher K.O. Williams. Epidemiology of childhood leukemia/lymphoma in resource-poor countries: Nature's manifestation of Ludwik Gross's experiments on environmental influence on animal leukemogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5028. doi:10.1158/1538-7445.AM2013-5028

Including the third dimension: A spatial analysis of TB cases in Houston Harris County

To reach the tuberculosis (TB) elimination goals established by the Institute of Medicine (IOM) and the Centers for Disease Control and Prevention (CDC), measures must be taken to speed the currently stagnant TB elimination rate and curtail a future peak in TB incidence. Increases in TB incidence have historically coincided with immigration, poverty, and joblessness; all situations that are currently occurring worldwide. Effective TB elimination strategies will require the geographical elucidation of areas within the U.S. that have endemic TB, and systematic surveillance of the locations and location-based risk factors associated with TB transmission. Surveillance data was used to assess the spatial distribution of cases, the yearly TB incidence by census tract, and the statistical significance of case clustering. The analysis revealed that there are neighborhoods within Houston/Harris County that had a heavy TB burden. The maximum yearly incidence varied from 245/100,000-754/100,000 and was not exclusively dependent of the number of cases reported. Geographically weighted regression identified risk factors associated with the spatial distribution of cases such as: poverty, age, Black race, and foreign birth. Public transportation was also associated with the spatial distribution of cases and census tracts identified as high incidence were found to be irregularly clustered within communities of varied SES.

Geoprocessing in health area

The map's usage and the concerns about geographic distribution related with diseases are not a recent issue. A classical example is the John Snow survey -maps were used to locate cholera's cases and related them with the water supplying. The spatial representation techniques are fewer used in health sectors due to troubles in managing such information. So, the aim of this survey was to establish the disease spatial distribution in Ribeirão Preto, 2002. Secondary data were used to elaborate this study. The spatial distribution of cases was realized by using the MapInfo 7.8 software. Although many cases were concentrated in the northeast region in the city, which consists the quarters of low economical income. The results contribute to show the Tb spatial distribution in Ribeirao Preto, they also reinforce the space category as a methodological alternative to manage, to monitor and to evaluate the health actions by directing interventions to decrease the iniquities.

SPATIAL CLUSTERING AND EPIDEMIOLOGICAL ASPECTS OF VISCERAL LEISHMANIASIS IN TWO ENDEMIC VILLAGES, BARINGO DISTRICT, KENYA

Visceral leishmaniasis (VL) seroprevalence in Kenya is unknown because of the lack of a practical and accurate diagnostic test or surveillance system. A novel serological assay was used to estimate the seroprevalence of Leishmania-specific antibodies, and Global Information System and spatial clustering techniques were applied to study the presence of spatial clusters in Parkarin and Loboi villages in Baringo District in 2001. VL seroprevalences were 52.5% in Parkarin and 16.9% in Loboi. Significant associations among seropositivity and house construction, age, and proximity to domestic animal enclosures were found. A significant spatial cluster of VL was found in Loboi. The spatial distribution of cases in the two villages was different with respect to risk factors, such as presence of domestic animals. This study suggests that disease control efforts could be focused on elimination of sand fly habitat, placement of domestic animal enclosures, and targeted use of insecticides.

Leishmaniasis: Public health aspects and control

Cutaneous leishmaniasis (CL) places a major burden on the health authorities in Saudi Arabia. Information about the geographical reach and seasonality of CL in Asir province remains limited. Therefore, this study aimed to investigate the epidemiological features of CL in southwest Saudi Arabia.Retrospective data from CL patients was collected from the regional vector control unit in Asir province over 9 years. Information analysis was performed using R statistic language (version 4.0.5) and the spatial distribution of cases was mapped using QGIS (version 3.20.0).A total of 1565 CL cases were recorded from 2011 to 2020. Saudi male citizens were at the highest risk of CL infection. However, children under the age of 13 years were most at risk of contracting CL. CL lesions were primarily located on the face and most cases were reported in the winter and autumn seasons. Spatially, the governates of Abha, Sarat-Abidah and Khamis-Mushait had the highest CL infection prevalence. Moreover, a geographical expansion of CL from Abha to Khamis-Mushait governate was noted during past ten years.This is the first large scale study to investigate the seasonality, spatial distribution and demographics of CL in Asir province. It describes how the geographical change of CL incidence differs in Asir province and reveals those people most at of CL infections. This study highlights the importance of incorporating improved living conditions, school education and public awareness in the development of CL control policies.

Geographical distribution of Alzheimer's disease cases at birth and the geochemical profile of Saguenay-Lac-Saint-Jean/Qu�bec, Canada (image project)

Accepting as founded the hypothesis of a multifactorial origin for the Alzheimer's disease (AD), we explore the possible links between the geographical distribution of AD cases according to their birth place and the geochemical profile of the Saguenay-Lac-Saint-Jean (SLSJ) territory in the province of Quebec. The method used for factor analysis of correspondances (FAC) and another one based on the differences between the residential and municipal geochemical concentrations (DRMC) have been used for this purpose. The geochemical matrix of SLSJ relates the highest concentrations of nickel, copper and zinc to the sector surrounding the Jonquiere municipality. Moreover, high concentrations of iron, lead and manganese were found in the northern sector of the Lac Saint-Jean. The DRMC method corroborates this strong correlation between iron, lead and manganese. Furthermore, these concentrations do not differ from the north-american geochemical standards. No single geochemical element seems to be associate with the spatial distribution of cases. It is, however, still possible that a certain synergistic effect between two or several elements could be implied in the development of the disease. According to the results of the soil analysis, there does not seem to be any association between the spatial distribution of cases and the concentration of aluminum, a chemical element that has been thought to be implied in the etiology of AD. These results are compared with those obtained by other workers in the micronesian islands, where abnormally high frequencies of amyotrophic lateral sclerosis and parkinsonism dementia have already been observed.

Landscape epidemiology of mosquito-borne canine heartworm (Dirofilaria immitis) in northern California, USA. I. Community-based surveys of domestic dogs in three landscapes.

Endemic patterns of canine filariasis in northern California were studied in 3 communities differing in ecological landscape: Tehama City (riparian-agricultural), Palo Cedro (oakpine woodland), and Cedar Ridge (conifer-oak forest). Dog populations were surveyed by household for canine-infecting filariids; both microfilaremic and amicrofilaremic patent Dirofilaria immitis infections were documented (Knott, IFA/ELISA tests). Of 403 dogs resident in these communities, 111 were on preventive diethylcarbamazine (DEC) citrate therapy (55% tested), and 292 had no recent DEC history (87% tested). Dirofilaria immitis was highly endemic in all communities, with point prevalence rates of 34.3% (Tehama City), 28.0% (Cedar Ridge), and 21.1% (Palo Cedro). Amicrofilaremic occult infections constituted 14–29% of total cases. The frequency distribution of microfilaremic densities in community dogs was highly skewed (median = 4040 mf/ml). Dipetalonema reconditum microfilariae were found in 4.9% of dogs in the Tehama community. Significant heartworm risk factors were Residence period, exposure, and SEX as determined from stepwise logistic regression analysis. Heartworm risk increased with length of residence, compared to a reference population resident ≤ 1 year. Adjusted odds ratios were 3.1 in dogs resident 1–3 years, 5.5 (3–5 years), and 12.2 (>5 years) (98.7% confidence). Dogs kept strictly outside were at 5.4× greater risk of patent heartworm disease than animals kept indoors for at least part of the 24-h day (97.5% confidence). Increased risk was also quantified for spayed females (R = 4.2) and for all males (R = 3.0), compared to intact females (98.3% confidence). Heartworm cases in Cedar Ridge were clustered adjacent to areas of disrupted forest landscape, suggesting a focal mosquito vector originating from the disturbed area. In Tehama City, cases were evenly scattered throughout the town, suggesting highly dispersive mosquito vector populations. The spatial distribution of cases in Palo Cedro indicated a woodland-associated vector with limited dispersal ability. Dipetalonema reconditum cases were mostly clustered by neighborhood in Tehama City.