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.

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Global epidemiology, ecology and control of soil-transmitted helminth infections

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...

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The growing degree-day and fish size-at-age : the overlooked metric

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.

The potential of geographical information systems and remote sensing in the epidemiology and control of human helminth infections.

A Synopsis of the Monogenetic Trematodes.

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.

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The global limits and population at risk of soil-transmitted helminth infections in 2010

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.

Developmental studies concerning the eggs of Ascaris lumbricoides var. suum.

The subfamily Tetraonchinae is composed of twenty recognized genera (Sproston 1946). North American investigations on this group began in 1932 when Van Cleave and Mueller described Urocleidus aculeatus. Presently there are four North American freshwater genera and two exotic genera that have freshwater representatives on this continent. An additional genus was proposed by Mizelle (1955) and is defined herein. The present paper was planned to aid workers in this particular area of parasitology and to stimulate others to participate in research on the Monogenea. The host-list section enables an investigator to know the possibilities regarding the identity of a species after the host has been identified. Reference to the genera-and-species section will provide information concerning papers 1) containing original descriptions, 2) synonymy, and 3) the hosts and localities from which given species have been recorded together with the authors involved. In cases where a species has been cited from the same host and locality more than once by a given author, only the date of the first citation is given. The Reelfoot Lake locality has been changed in all cases from Ridgely, Tennessee to Tiptonville, Tennessee. This in no way changes the type locality in the case of new species but merely cites a more appropriate village near the lake as advised by Dr. C. L. Baker of Southwestern College at Memphis.

North American Freshwater Tetraonchinae

Host specimens, which constitute one hundred thirty-seven fish belonging to the -families Centrarchidae and Ameiuridae, were collected from streams and ponds in the vicinity of Stillwater, Oklahoma. After identification the hosts were either preserved by freezing or kept in laboratory aquaria pending experimentation. Parasites were collected and preserved according to the method described by Mizelle (1938b).

http://www.jstor.org/stable/pdfplus/2420296.pdf

Studies on Gill Trematodes from Oklahoma Fishes

anteriorly directed cuticular body spines along the posterior one fourth of the body. Total length 0.744 mm (0.590-0.990 mm); greatest body width 0.095 mm (0.060-0.140 mm) usually present in anterior body half. Eyespots four, members of posterior pair always larger and usually closer together than those of anteritor pair. Accessory melanistic granules, apparently same type as those comprising eyespots, often present in vicinity of eyespots. Cephalic lobes two; head organs donspicuous. Pharynx subcircular to broadly ovate (transversely) in outline and 0.032 mm (0.030-0.033 mm) in greatest diameter. Peduncle relatively long, tapered posteriorly with six rows of spine-like hooks along entire length. Each peduncular hook composed of a founded base, a relatively heavy shaft which tapers distally to a point, and an opposable piece. Lateral margins of shaft curved upward and toward mid-line of shaft. Peduncular hooks diminish in length in anterior direction (figs. 1-3). Haptor expanded laterally and more than twice as wide as the greatest body width. Haptor width approximately 0.285 mm (0.250-0.360 mm). A row of accessory spines situated dorsal and a row ventral to bars; individual spines diminish in length toward mid-haptoral line (fig. 16a, ventral row not shown) and each perforated near anterior end which occasionally appears frayed (figs. 4, 5). A single row of spines situated immediately anterior to ventral bar (fig. 16b). Two pairs of slightly curved accessory spines anterior to the row of spines above dorsal bars (fig. 16c). A clump of smaller spines appears lateral to each member of the posterior pair of last-named accessory spines (fig. 16d). Three haptoral bars present; ventral (fig. 8) longest with ends sharply tapered and gently curved, conspicuous longitudinal groove present, anterior border deeply notched at mid-length, posterior border with small tubercle opposite notch, length 0.172 mm (0.136-0.210 mm). Two dorsal bars (figs. 6, 7) of approximately equal size articulated to ventral bar; length 0.086 mm (0.073-0.095 mm),. Anchors similar in shape, approximately equal in size and possessing solid bases and with slightly curved shafts and recurved points (figs. 10-13). Dorsal anchbr with superficial root reduced and constricted near midportion to form rounded knob-like process, deep root well developed; dorsal anchor length 0.056 mm (0.042-0.065 mm); greatest width of base 0.010 mm (figs. 10, 11). Ventral anchors similar in shape to that of dorsal anchbrs but with superficial root more reduced; ventral anchor length 0.054 mm (0.045-0.063 mm); greatest width of base 0.010 mm (0.005-0.01 mm) (figs. 12, 13). Haptoral hooks 14 in number approximately equal in size and normal in arrangement (Mizelle 1938). Each hook composed of a gently curved shaft, a sickle-shaped termination, and opposable piece; hook base not dif

A new species of Rhamnocercinae.

A survey of the literature reveals only two papers concerning the Monogenea from fishes in Louisiana. Summers (1937) described Anchoradiscus triangularis from the "small sunfish" Lepomis symmetricus Forbes, and Summers and Bennett (1938) presented a brief survey of gill flukes from fishes collected near Baton Rouge and New Roads, Louisiana. The present paper presents the description of a new species, Urocleidus wadei from the flier sunfish Centrarchus macropterus (Lacepede) and a number of new host and distribution records. The new species is the first to be reported from the flier sunfish and is the only one recorded for this host.

Aaron Seamster

Papers

Developmental studies concerning the eggs of Ascaris lumbricoides var. suum.

North American Freshwater Tetraonchinae

Studies on Gill Trematodes from Oklahoma Fishes

A new species of Rhamnocercinae.

Gill parasites from Louisiana fishes with a description of Urocleidus wadein. sp.