Spatial Variation In Prevalence Research Articles

Spatial and Temporal Variability in Prevalence Rates of Members of the Borrelia burgdorferi Species Complex in Ixodes ricinus Ticks in Urban, Agricultural and Sylvatic Habitats in Slovakia.

Lyme borreliosis (LB) is the most prevalent tick-borne human infection in Europe, with increasing incidence during the latest decades. Abundant populations of Ixodes ricinus, the main vector of the causative agent, spirochetes from the Borrelia burgdorferi sensu lato (Bbsl) complex, have been observed in urban and suburban areas of Europe, in general, and Slovakia, particularly. Understanding the spread of infectious diseases is crucial for implementing effective control measures. Global changes affect contact rates of humans and animals with Borrelia-infected ticks and increase the risk of contracting LB. The aim of this study was to investigate spatial and temporal variation in prevalence of Bbsl and diversity of its species in questing I. ricinus from three sites representing urban/suburban, natural and agricultural habitat types in Slovakia. Ixodes ricinus nymphs and adults were collected by dragging the vegetation in green areas of Bratislava town (urban/suburban habitat), in the Small Carpathians Mountains (natural habitat) (south-western Slovakia) and in an agricultural habitat at Rozhanovce in eastern Slovakia. Borrelia presence in ticks was detected by PCR and Bbsl species were identified by restriction fragment length polymorphism (RFLP). Borrelia burgdorferi s.l. species in coinfected ticks were identified by reverse line blot. Significant spatial and temporal variability in prevalence of infected ticks was revealed in the explored habitats. The lowest total prevalence was detected in the urban/suburban habitat, whereas higher prevalence was found in the natural and agricultural habitat. Six Bbsl species were detected by RFLP in each habitat type -B. burgdorferi sensu stricto (s.s.), B. afzelii, B. garinii, B. valaisiana, B. lusitaniae and B. spielmanii. Coinfections accounted for 3% of the total infections, whereby B. kurtenbachii was identified by RLB and sequencing in mixed infection with B. burgdorferi s.s, B. garinii and B. valaisiana. This finding represents the first record of B. kurtenbachii in questing I. ricinus in Slovakia and Europe. Variations in the proportion of Bbsl species were found between nymphs and adults, between years and between habitat types. Spatial variations in prevalence patterns and proportion of Bbsl species were also confirmed between locations within a relatively short distance in the urban habitat. Habitat-related and spatial variations in Borrelia prevalence and distribution of Bbsl species are probably associated with the local environmental conditions and vertebrate host spectrum. Due to the presence of Borrelia species pathogenic to humans, all explored sites can be ranked as areas with high epidemiological risk.

Malaria in Kenya during 2020: malaria indicator survey and suitability mapping for understanding spatial variations in prevalence and risk

Abstract. Despite the availability of effective interventions malaria continues to be a major public health issue in Kenya, where young children and pregnant women are particularly vulnerable. In this study we examined the spatial distribution of malaria incidence and how this relates to the environmental conditions required for malaria in 2020. The Kenya Malaria Indicator Survey (N=11,549) for 2020 was used with the Local Indicators of Spatial Autocorrelation (LISA) method to determine spatial clusters of malaria and assess their significance as well as interventions in use. Climate data was used with a Fuzzy Overlay method to create malaria risk maps. The findings suggest that malaria incidence is not evenly distributed across Kenya, with some regions having higher rates of transmission and others having lower rates. High-rate clusters of malaria and high-risk areas of malaria transmission could benefit from increased vector control measures.

Natural history of the parasite Waddycephalus in the Townsville region of north-east Australia.

Waddycephalus is an understudied genus of pentastomids native to Australia and south-east Asia. The genus was recognized in 1922 but there has been little research on these pentastomid tongue worms over the last century. A few observations suggest a complex life cycle through 3 trophic levels. We aimed to add knowledge to the Waddycephalus life cycle in woodland habitats in the Townsville region of north-east Australia. We used camera trapping to identify the most likely first-intermediate hosts (coprophagous insects), we conducted gecko surveys to identify multiple new gecko intermediate host species and we dissected road-killed snakes to identify additional definitive hosts. Our study paves the way for further research into the intriguing life cycle of Waddycephalus, investigation of spatial variation in prevalence and impacts of the parasite on host species.

Spatial distribution of psychotic disorders in an urban area of France: an ecological study

Previous analyses of neighbourhood variations of non-affective psychotic disorders (NAPD) have focused mainly on incidence. However, prevalence studies provide important insights on factors associated with disease evolution as well as for healthcare resource allocation. This study aimed to investigate the distribution of prevalent NAPD cases in an urban area in France. The number of cases in each neighbourhood was modelled as a function of potential confounders and ecological variables, namely: migrant density, economic deprivation and social fragmentation. This was modelled using statistical models of increasing complexity: frequentist models (using Poisson and negative binomial regressions), and several Bayesian models. For each model, assumptions validity were checked and compared as to how this fitted to the data, in order to test for possible spatial variation in prevalence. Data showed significant overdispersion (invalidating the Poisson regression model) and residual autocorrelation (suggesting the need to use Bayesian models). The best Bayesian model was Leroux’s model (i.e. a model with both strong correlation between neighbouring areas and weaker correlation between areas further apart), with economic deprivation as an explanatory variable (OR = 1.13, 95% CI [1.02–1.25]). In comparison with frequentist methods, the Bayesian model showed a better fit. The number of cases showed non-random spatial distribution and was linked to economic deprivation.

Temporal consistency in background mortality of four dominant coral taxa along Australia’s Great Barrier Reef

Studies on the population and community dynamics of scleractinian corals typically focus on catastrophic mortality associated with acute disturbances (e.g., coral bleaching and outbreaks of crown-of-thorns starfish), though corals are subject to high levels of background mortality and injuries caused by routine and chronic processes. This study quantified prevalence (proportion of colonies with injuries) and severity (areal extent of injuries on individual colonies) of background mortality and injuries for four common coral taxa (massive Porites, encrusting Montipora, Acropora hyacinthus and branching Pocillopora) on the Great Barrier Reef, Australia. Sampling was conducted over three consecutive years during which there were no major acute disturbances. A total of 2276 adult colonies were surveyed across 27 sites, within nine reefs and three distinct latitudinal sectors. The prevalence of injuries was very high (>83%) across all four taxa, but highest for Porites (91%) and Montipora (85%). For these taxa (Montipora and Pocillopora), there was also significant temporal and spatial variation in prevalence of partial mortality. The severity of injuries ranged from 3% to more than 80% and varied among coral taxa, but was fairly constant spatially and temporally. This shows that some injuries have considerable longevity and that corals may invest relatively little in regenerating tissue over sites of previous injuries. Inter-colony variation in the severity of injury also had no apparent effect on the realized growth of individual colonies, suggesting that energy diverted to regeneration has a limited bearing on overall energetic allocation, or impacts on other life-history processes (e.g., reproduction) rather than growth. Establishing background levels of injury and regeneration is important for understanding energy investment and life-history consequences for reef-building corals as well as for predicting susceptibility to, and capacity to recover from, acute disturbances.

Mapping the Risk of Soil-Transmitted Helminthic Infections in the Philippines.

BackgroundIn order to increase the efficient allocation of soil-transmitted helminth (STH) disease control resources in the Philippines, we aimed to describe for the first time the spatial variation in the prevalence of A. lumbricoides, T. trichiura and hookworm across the country, quantify the association between the physical environment and spatial variation of STH infection and develop predictive risk maps for each infection.Methodology/Principal FindingsData on STH infection from 35,573 individuals across the country were geolocated at the barangay level and included in the analysis. The analysis was stratified geographically in two major regions: 1) Luzon and the Visayas and 2) Mindanao. Bayesian geostatistical models of STH prevalence were developed, including age and sex of individuals and environmental variables (rainfall, land surface temperature and distance to inland water bodies) as predictors, and diagnostic uncertainty was incorporated. The role of environmental variables was different between regions of the Philippines. This analysis revealed that while A. lumbricoides and T. trichiura infections were widespread and highly endemic, hookworm infections were more circumscribed to smaller foci in the Visayas and Mindanao.Conclusions/SignificanceThis analysis revealed significant spatial variation in STH infection prevalence within provinces of the Philippines. This suggests that a spatially targeted approach to STH interventions, including mass drug administration, is warranted. When financially possible, additional STH surveys should be prioritized to high-risk areas identified by our study in Luzon.

Schizophrenia in East County Cavan: Spatial Variations in Prevalence and their Aetiological Implications

Schizophrenia prevalence rates in Ireland have been amongst the highest in (he world For over a century. These rates do not necessarily indicate a high risk of mental illness in the community, but they could reflect elevated risks associated with either genetic factors or unidentified factors associated with the Irish social or physical environment. This study examines spatial variations in prevalence in east County Cavan. By confining the study to a small area. The effects of nosocomial factors and diagnostic variability can be assumed to be minimal. Also, given that the study area receives few immigrants, drift processes, which complicate most other small-area studies, may be discounted. Various statistical tests indicate that the prevalence of schizophrenia in east Cavan is significantly uneven. After considering various alternative explanations, it is concluded that the observed spatial variations in prevalence possibly reflect the influence of unidentified environmental factors.

Kilometer-scale Spatial Variation in Prevalence of the Rhizocephalan Lernaeodiscus porcellanae on the Porcelain Crab Petrolisthes cabrilloi

Abstract We studied spatial variation in the prevalence of the rhizocephalan barnacle Lernaeodiscus porcellanae on its porcelain crab host, Petrolisthes cabrilloi, at four southern California intertidal sites separated by only a few km. The prevalence of rhizocephalan externae varied significantly among sites in 2008-2009, with the southernmost site, White Point, consistently showing higher prevalence than the others. Externa prevalence was a good proxy of estimated true prevalence, i.e., the prevalence of rhizocephalans as a whole, not just those that had formed externae. We examined several hypotheses that might explain the observed spatial variation in prevalence. Host susceptibility to infection (indicated by the proxy of damage to host limbs, some of which are used to remove parasite infective stages), did not differ among sites. At all sites, prevalence was slightly higher in female crabs than in males, and the sex ratio at White Point was slightly female-biased while that at the other sites was mal...

ASSOCIATIONS BETWEEN SHOREBIRD ABUNDANCE AND PARASITES IN THE SAND CRAB, EMERITA ANALOGA, ALONG THE CALIFORNIA COAST

I investigated spatial variation in the prevalence and abundance of 4 species of parasites in the sand crab, Emerita analoga, on 8 sandy beaches along 800 km of the California coast, to assess the importance of bird abundance for the distribution of parasites among sand crab populations. I collected sand crabs and counted shorebirds and gulls at each beach during June and November 1994. Sand crabs served as intermediate hosts for 4 species of parasites, including a trematode, Spelotrema nicolli (Cable and Hunnienen, 1938); an acanthocephalan, Polymorphus kenti (Van Cleave, 1947); a nematode, Proleptus sp., and an unidentified trypanorhynch tapeworm. Among sand crab populations, there was substantial spatial variation in the prevalence and abundance of each parasite species. No latitudinal pattern was apparent for any of the 4 species observed. Temporally, parasite prevalence and abundance was significantly different between dates for all 4 parasites. Specifically, sand crab populations experienced higher trematode, nematode, and trypanorhynch prevalence and abundance in November than in June. In contrast, prevalence and abundance of acanthocephalans were higher in June than in November. There were strong positive associations between bird abundance and prevalence of parasitic infection for trematodes and acanthocephalans for some dates but not for nematodes or trypanorhynchs, which use elasmobranchs as definitive hosts. The spatial variation in prevalence and abundance of trematodes and acanthocephalans observed among sand crab populations may be attributed to the distribution and abundance of shorebirds and gulls that serve as definitive hosts.

An assessment of government policy response to HIV/AIDS in Ghana

The HIV/AIDS epidemic in Africa has assumed a dimension raising heartbreaking anxiety among national governments and civil society groups. In Ghana for example, the pandemic is well-documented and has gone beyond a health problem, and now encompasses all socio-economic aspects of life. The estimated rate of infection from the mid-1980s to 2000 has more than doubled, and in spite of the control efforts by various groups and organisations, prevalence of the disease has not declined notably. This paper assesses government policy, programmes and strategies to combat the disease, using analysis of time trend sentinel data and weighting these against control efforts. The assessment revealed that 380 000 adults and 36 000 children are currently infected. There are wide spatial variations in prevalence across the country and the overall national prevalence has fluctuated over time, standing at 2.6% in 2000, 3.6% in 2002 and 3.1% in 2004. This appears relatively lower than in adjacent countries, where prevalence is around 5% and over 25% in East and Southern African countries. Although the review found a robust multipronged government intervention approach to containing the disease, we are hesitant to claim that the fairly stable or low national prevalence in Ghana compared with its immediate neighbours may have been the consequence of the effectiveness of national AIDS control programmes and impact of government interventions.

Seasonal dynamics of mycoplasmal conjunctivitis in eastern North American house finches

SummaryMycoplasma gallisepticumis an emerging eye disease that spread rapidly among wild house finches (Carpodacus mexicanus) in the eastern United States following initial reports of infected birds in 1994. The hallmark signs of infection have allowed systematic monitoring of disease at both local and continent‐wide scales for more than 7 years since the onset of the epidemic.Using data collected by a network of citizen science volunteers, we examined both long‐term trends and seasonal dynamics of mycoplasmal conjunctivitis in three different climatic regions in eastern North America over a 77‐month period (November 1994–March 2001).Time‐series prevalence data from all three regions suggest that following establishment, marked seasonal fluctuations in prevalence each year were characterized by autumn–winter epidemics (in October and February) and consistent summer declines (with prevalence falling close to zero from May to July).The maximum peak, annual rates of increase and timing of epidemics varied among three geographical locations that were delineated by minimum winter temperatures. Annual autumn prevalence in the South increased more rapidly, and maximum prevalence was nearly three times greater in the South than in the colder North and Central regions.Longer‐term trends showed evidence for multiyear fluctuations in prevalence that were characterized by greater amplitude in the southern region.Finally, monthly estimates of house finch flock sizes derived from a similar citizen science data set showed that winter flock sizes were associated positively with average monthly prevalence in the northern and central regions, although regional differences in flock sizes did not correspond to regional differences in maximum prevalence.This study represents the first evidence of multiyear fluctuations, regional differences and highly predictable annual outbreaks of this recently emerged wildlife pathogen. Several factors associated with house finch life history and behaviour are likely to contribute to temporal and spatial variation in prevalence, including annual changes in host reproduction, social behaviour and environmental effects on host stress or immunocompetence.

Geographical variation in blood parasites in feral pigeons: the role of vectors

Prevalence and intensity of blood parasites are known to vary in space within a same species, yet the causes underlying such variation are poorly known. Theoretically, blood parasites variation can be attributed to differences to exposure to parasite vectors and/or to differences in host susceptibility. Here, we show that prevalence of Haemoproteus columbae in feral pigeons Columba livia varied among five near‐by populations (range 15%‐100%), paralleled by variation in the abundance of its main vector, the louse flies Pseudolynchia canariensis. Geographic variation in intensity of blood parasites did not covary with abundance of vectors. Within populations, older individuals had a higher probability of being parasitized than younger ones, whereas younger birds, when infected, suffered higher intensities. Furthermore, we found no evidence of sex‐related differences neither in prevalence nor in intensity of blood parasite infections. To demonstrate that geographical variation in prevalence was actually due to differences in vector exposure, we conducted two experiments based on translocation of unparasitized pigeons from a vector‐free area to an area where both the parasite and vector were abundant. With the first experiment, we demonstrated that unparasitized pigeons were not resistant to the parasite because when transmission was possible pigeons became parasitized in a few months. With the second experiment, in which half of the pigeons were prevented from contacts with the vector, we ruled out the posibility that pigeons we considered as unparasitized would have suffered from latent infections. Therefore, both observational and experimental evidence supports the view that vector abundance is the major factor influencing the spatial variation in prevalence of H. columbae in pigeons.

Schizophrenia in East County Cavan: Spatial Variations in Prevalence and their Aetiological Implications

Schizophrenia prevalence rates in Ireland have been amongst the highest in (he world For over a century. These rates do not necessarily indicate a high risk of mental illness in the community, but they could reflect elevated risks associated with either genetic factors or unidentified factors associated with the Irish social or physical environment. This study examines spatial variations in prevalence in east County Cavan. By confining the study to a small area. The effects of nosocomial factors and diagnostic variability can be assumed to be minimal. Also, given that the study area receives few immigrants, drift processes, which complicate most other small-area studies, may be discounted. Various statistical tests indicate that the prevalence of schizophrenia in east Cavan is significantly uneven. After considering various alternative explanations, it is concluded that the observed spatial variations in prevalence possibly reflect the influence of unidentified environmental factors.