Developmental studies concerning the eggs of Ascaris lumbricoides var. suum.
TL;DR: The literature reveals that velocity curves for developmental stages of parasitic worms have not been reported and many authors have studied the development of parasite ova and larvae but in each case they failed to present comprehen-sive information regarding temperature and humidity effects.
Abstract: The literature reveals that velocity curves for developmental stages of parasitic worms have not been reported. Many authors have studied the development of parasite ova and larvae but in each case they failed to present comprehen-sive information regarding temperature and humidity effects. The majority of such reports merely give the period required for development to a given stage under natural conditions or at a particular temperature or at the minimum, maximum, or optimum temperature. For instance, Leuckart (1876) observed complete embryonation of the ova of Ascaris lumbricoides (human) in forty days at "mid-summer temperatures"; Raillet (1893) reported that at a "favorable temperature" Ascaris lumbricoides var. suumn ova contained motile embryos in thirty to forty days; and Wharton (1915) observed embryonation of Ascaris lumbricoides (human) ova in fifteen days at "summer temperatures" in the Philippine Islands. Similarly, Brown (192-7a) reported embryonation of Trichuris trichiura ova in twenty-one days and of A. lumbricoides (human) ova in fifteen days under "field conditions" in Panama.
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TL;DR: These are the first estimates at a continental scale to explicitly include the fine spatial distribution of infection prevalence and population, and suggest that continent-wide control of parasites is, from a financial perspective, an attainable goal.
Abstract: Soil-transmitted helminth (STH) infections are among the most prevalent of chronic human infections worldwide. Based on the demonstrable impact on child development, there is a global commitment to finance and implement control strategies with a focus on school-based chemotherapy programmes. The major obstacle to the implementation of cost-effective control is the lack of accurate descriptions of the geographical distribution of infection. In recent years, considerable progress has been made in the use of geographical information systems (GIS) and remote sensing (RS) to better understand helminth ecology and epidemiology, and to develop low-cost ways to identify target populations for treatment. This review explores how this information has been used practically to guide large-scale control programmes. The use of satellite-derived environmental data has yielded new insights into the ecology of infection at a geographical scale that has proven impossible to address using more traditional approaches, and has in turn allowed spatial distributions of infection prevalence to be predicted robustly by statistical approaches. GIS/RS have increasingly been used in the context of large-scale helminth control programmes, including not only STH infections but also those focusing on schistosomiasis, filariasis and onchocerciasis. The experience indicates that GIS/RS provides a cost-effective approach to designing and monitoring programmes at realistic scales. Importantly, the use of this approach has begun to transition from being a specialist approach of international vertical programmes to becoming a routine tool in developing public sector control programmes. GIS/RS is used here to describe the global distribution of STH infections and to estimate the number of infections in school-age children in sub-Saharan Africa (89.9 million) and the annual cost of providing a single anthelmintic treatment using a school-based approach (US$5.0-7.6 million). These are the first estimates at a continental scale to explicitly include the fine spatial distribution of infection prevalence and population, and suggest that traditional methods have overestimated the situation. The results suggest that continent-wide control of parasites is, from a financial perspective, an attainable goal.
592 citations
Cites background from "Developmental studies concerning th..."
...…development§ 35-39 °C 37-39 °C 40 °C Basic reproductive number‡ 1-5 4-6 2-3 † Data taken from Anderson (1982);Bundy & Cooper (1989);Crompton (2001) ‡ Data taken from Anderson & May (1991) § Data on A. lumbricoides (Seamster (1950); T. suis (Beer, 1976); hookworm (Nwosu, 1978; Smith & Schad, 1989)....
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...Points indicate experimental data (Seamster, 1950; Beer, 1973; Nwosu, 1978;Udonsi & Atata, 1987) and lines are fits derived from fractional polynomials analyses....
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...…free-living infective stages occur at temperatures between 28 and 32 °C, with development of A. lumbricoides and T. trichiura arresting below 5 and above 38 °C (Beer, 1976;Seamster, 1950), and development of hookworm larvae ceasing at 40 °C (Udonsi & Atata, 1987; Smith & Schad, 1989) (Figure 1b)....
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TL;DR: It is demonstrated that fish length-at-day (LaD), in most cases prior to maturation, is a strong linear function of the GDD metric that can explain >92% of the variation in LaD among 41 data sets representing nine fish species drawn from marine and freshwater environments, temperate and tropical climes, constant and variable temperature regimes, and laboratory and field studies.
Abstract: Growth rate in ectotherms, including most fish, is a function of temperature. For decades, agriculturalists (270+ years) and entomologists (45+ years) have recognized the thermal integral, known as...
287 citations
Additional excerpts
...…for at least 45 years in entomology, the time-based integral of the heat available for growth — heat transferred from the environment to the ectotherm — has been employed with remarkable success in explaining and predicting growth and development (e.g., Seamster 1950; Atkinson 1994; Bonhomme 2000)....
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TL;DR: These applications suggest a successful role for GIS/RS applications in investigating the spatial epidemiology of the major human helminths and the development and use of appropriate spatially-explicit statistical and modeling techniques in data analysis is required.
Abstract: Geographic information systems (GIS) and remote sensing (RS) technologies are being used increasingly to study the spatial and temporal patterns of infectious diseases. For helminth infections, however, such applications have only recently begun despite the recognition that infection distribution patterns in endemic areas may have profound effects on parasite population dynamics and therefore the design and implementation of successful control programmes. Here, we review the early applications of these technologies to the major human helminths (geohelminths, schistosomes and the major lymphatic filarial worms), which demonstrate the potential of these tools to serve as: (1) an effective data capture, mapping and analysis tool for the development of helminth atlases; (2) an environment for modeling the spatial distribution of infection in relation to RS and environmental variables, hence furthering the understanding of the impact of density-independent factors in underlying observed parasite spatial distributions and their effective prediction; and (3) a focal tool in parasite control programming given their abilities to (i) better define endemic areas, (ii) provide more precise estimates of populations-at-risk, (iii) map their distribution in relation to health facilities and (iv) by facilitating the stratification of areas by infection risk probabilities, to aid in the design of optimal drug or health measure delivery systems. These applications suggest a successful role for GIS/RS applications in investigating the spatial epidemiology of the major human helminths. It is evident that further work addressing a range of critical issues include problems of data quality, the need for a better understanding of the population biological impact of environmental factors on critical stages of the parasite life-cycle, the impacts and consequences of spatial scale on these relationships, and the development and use of appropriate spatially-explicit statistical and modeling techniques in data analysis, is required if the true potential of this tool to helminthology is to be fully realized.
254 citations
TL;DR: High and low land surface temperature and extremely arid environments were found to limit STH transmission, with differential limits identified for each species and provide an essential basis for estimating the global disease burden due to STH infection.
Abstract: Understanding the global limits of transmission of soil-transmitted helminth (STH) species is essential for quantifying the population at-risk and the burden of disease. This paper aims to define these limits on the basis of environmental and socioeconomic factors, and additionally seeks to investigate the effects of urbanisation and economic development on STH transmission, and estimate numbers at-risk of infection with Ascaris lumbricoides, Trichuris trichiura and hookworm in 2010. A total of 4,840 geo-referenced estimates of infection prevalence were abstracted from the Global Atlas of Helminth Infection and related to a range of environmental factors to delineate the biological limits of transmission. The relationship between STH transmission and urbanisation and economic development was investigated using high resolution population surfaces and country-level socioeconomic indicators, respectively. Based on the identified limits, the global population at risk of STH transmission in 2010 was estimated. High and low land surface temperature and extremely arid environments were found to limit STH transmission, with differential limits identified for each species. There was evidence that the prevalence of A. lumbricoides and of T. trichiura infection was statistically greater in peri-urban areas compared to urban and rural areas, whilst the prevalence of hookworm was highest in rural areas. At national levels, no clear socioeconomic correlates of transmission were identified, with the exception that little or no infection was observed for countries with a per capita gross domestic product greater than US$ 20,000. Globally in 2010, an estimated 5.3 billion people, including 1.0 billion school-aged children, lived in areas stable for transmission of at least one STH species, with 69% of these individuals living in Asia. A further 143 million (31.1 million school-aged children) lived in areas of unstable transmission for at least one STH species. These limits provide the most contemporary, plausible representation of the extent of STH risk globally, and provide an essential basis for estimating the global disease burden due to STH infection.
247 citations
Cites background from "Developmental studies concerning th..."
...Experimental and field studies indicate that the survival and development of STH free living stages, and hence STH transmission, are crucially dependent on ambient and surface temperature and humidity [22-25]....
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...The observed limiting relationship between all three STH species and climatic factors in Africa and the Middle East corroborate previous experimental and observational findings that transmission is implausible in extremely hot, cold or arid conditions [22-25,33,40], and likely reflects the dynamic processes involved in STH transmission, such as free-living infective stage development and survival [41]....
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195 citations
References
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Book•
01 Jan 1863
73 citations
TL;DR: It is argued that eggs of these species probably remain viable and infective in nature a corresponding length of time and this opinion has been supported further by the results of experiments by Baillet (1866) and Cram (1924) who found Ascaris and Trichuris eggs to be very resistant to freezing temperatures.
Abstract: Most of the data on the rate of development and viability of the eggs of Ascaris lumbricoides and Trichuris trichiura have been obtained from the laboratory experiments in which the incubation and storage of the eggs were in aqueous media. Railliet (1893) found that at a favorable temperature Ascaris eggs contained motile embryos in 30 to 40 days. Davaine (1858) noted the formation of embryos in 30 days when Ascaris eggs were kept at a temperature of about 40? C. Likewise Leuckart (1876) found that in mid-summer the embryos are completely formed at the end of 40 days. More recently Wharton (1915) has reported that at summer temperatures in the Philippines Ascaris eggs develop completely in 15 days. From such data most workers conclude that in nature under the most favorable conditions of temperature and moisture the eggs of Ascaris take from 30 to 40 days to develop and those of Trichuris about twice as long. Likewise from the experiments of Davaine (1863), Morris (1911) and Epstein (1892) in which the eggs of Ascaris and Trichuris remained infective as long as five years in preserved feces it has been argued that eggs of these species probably remain viable and infective in nature a corresponding length of time. This opinion has been supported further by the results of experiments by Baillet (1866) and Cram (1924) who found Ascaris and Trichuris eggs to be very resistant to freezing temperatures. Ross (1916) reported that Ascaris eggs were still viable after having been exposed dry to the hot sun of India for as long a period as six weeks. Later workers on the other hand have found 98? C. lethal to
41 citations
TL;DR: The daily egg production for several different species of parastic worms has been estimated by a comparison of the number of worms obtained by treatment with the egg output as determined by the dilution egg count as mentioned in this paper.
Abstract: The daily egg production for several different species of parastic worms has been estimated by a comparison of the number of worms obtained by treatment with the egg output as determined by the dilution egg count. By this method Stoll (1923) obtained a figure of about 9,000 eggs per day for a female of Necator americanus and Sweet (1924) and Cort, Stoll and Grant (1926) estimated the daily output of a female of Ancylostoma duodenale to be several times as large. For Fasciolopsis buski Stoll, Cort and Kwei (1927) have given an estimate of a daily output of about 25,000 eggs per worm. Faust and Khaw (1926) reported that the number of eggs produced by Clonorchis sinensis depended on the kind of host. For infestations in the cat their estimate was 2,400 eggs per day per worm, for the guinea pig 1,600, and for the dog 1,100. An egg output much higher than for any of these species would be expected for Ascaris lunibricoides, since these worms are of such large size and contain so many eggs in their uteri. Cram (1925) has recently estimated that the number of eggs in a single female ascaris may be as high as 27,000,000. We were, therefore, to some extent prepared for the high egg production figures obtained for this parasite from the study of two cases in which one of us (Brown) was able to make an egg-worm correlation in Panama.
34 citations
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