María Adela Valero

Climate change effects on trematodiases, with emphasis on zoonotic fascioliasis and schistosomiasis.

The capacity of climatic conditions to modulate the extent and intensity of parasitism is well known since long ago. Concerning helminths, among the numerous environmental modifications giving rise to changes in infections, climate variables appear as those showing a greater influence, so that climate change may be expected to have an important impact on the diseases they cause. However, the confirmation of the impact of climate change on helminthiases has been reached very recently. Only shortly before, helminthiases were still noted as infectious diseases scarcely affected by climate change, when compared to diseases caused by microorganisms in general (viruses, bacteriae, protozoans). The aim of the present paper is to review the impact of climate change on helminthiases transmitted by snails, invertebrates which are pronouncedly affected by meteorological factors, by focusing on trematodiases. First, the knowledge on the effects of climate change on trematodiases in general is reviewed, including aspects such as influence of temperature on cercarial output, cercarial production variability in trematode species, influences of magnitude of cercarial production and snail host size, cercarial quality, duration of cercarial production increase and host mortality, influence of latitude, and global-warming-induced impact of trematodes. Secondly, important zoonotic diseases such as fascioliasis, schistosomiasis and cercarial dermatitis are analysed from the point of view of their relationships with meteorological factors. Emphasis is given to data which indicate that climate change influences the characteristics of these trematodiases in concrete areas where these diseases are emerging in recent years. The present review shows that trematodes, similarly as other helminths presenting larval stages living freely in the environment and/or larval stages parasitic in invertebrates easily affected by climate change as arthropods and molluscs as intermediate hosts, may be largely more susceptible to climate change impact than those helminths in whose life cycle such phases are absent or reduced to a minimum. Although helminths also appear to be affected by climate change, their main difference with microparasites lies on the usually longer life cycles of helminths, with longer generation times, slower population growth rates and longer time period needed for the response in the definitive host to become evident. Consequently, after a pronounced climate change in a local area, modifications in helminth populations need more time to be obvious or detectable than modifications in microparasite populations. Similarly, the relation of changes in a helminthiasis with climatic factor changes, as extreme events elapsed relatively long time ago, may be overlooked if not concretely searched for. All indicates that this phenomenon has been the reason for previous analyses to conclude that helminthiases do not constitute priority targets in climate change impact studies.

Identification of genotypes of Giardia intestinalis of human isolates in Egypt

In Egypt, the genotyping study of Giardia intestinalis in human is limited. To determine the prevalence of G. intestinalis, faecal samples were collected from Egypt. Samples were concentrated using density gradient centrifugation. The samples were subjected to PCR and DNA sequence analysis for TPI gene. Prevalence of Giardia infection was 34.6% of 52 examined. DNA sequence showed that the Assemblage B was the most prevalent (80%) genotype, the 15% of the positive samples belonged to Assemblage E, and the 5% of them belonged to Assemblage A. Certainly, both genotypes A and B are highly common in human worldwide. However, up to now, Assemblage E had not been known to be infectious for humans. Therefore, this is the first time that Assemblage E is reported in human. However, further analyses of a second locus are required to confirm this result. The extent to which Giardia-infected cattle in Egypt might pose a risk of human infection is unknown.

Analysis of climatic data and forecast indices for human fascioliasis at very high altitude

Human infection with Fasciola hepatica has recently been recognized as an important health problem worldwide, and particularly at very high altitudes in South America. The highest prevalences and intensities of human fascioliasis known are those of the northern Bolivian Altiplano, where infected Lymnaea truncatula occur at altitudes of 3800-4100 m. In the present study, the climatic data for this area of the Altiplano, which differ markedly from those of endemic areas in the lowlands, were analysed. There is no marked seasonality in temperature but there are large variations in temperature within a daily, 24-h period. Rainfall is seasonal, with a long dry season, coinciding with the lowest minimum temperatures, and a long wet season. The rate of evapotranspiration is very high, and temporary water bodies dry out very quickly. Solar radiation at ground level is intense, not only because of the altitude but also because of the lack of trees and shrubs. Two climatic indices for forecasting fascioliasis, Mt and Wb-bs, were calculated. Modifications in these forecast indices are proposed, to reflect the environment at high altitude and low latitude. Estimates, based on climadiagrammes, of the durations of the wet and dry seasons were greatly effected by the inclusion of an aridity-index modification. The usefulness of the modified indices was examined using prevalence data for human and cattle fascioliasis collected in the neighbourhoods of the stations providing the meteorological data. Values for both indices indicated that conditions were optimum for transmission between December and March. The results were statistically significant for the modified Wb-bs index when the data for a meteorological station in which no lymnaeids were found were excluded. The modified Mt index did not appear sufficiently accurate to be useful. The values for the modified Wb-bs index permitted the study areas to be designated low-, moderate- or high-risk areas for the transmission of fascioliasis to man and domestic animals.

Risk of Gallstone Disease in Advanced Chronic Phase of Fascioliasis: An Experimental Study in a Rat Model

In Wistar rats experimentally infected with Fasciola hepatica, the association between time of infection, number of flukes, rat weight, and serum lipid levels and the risk of developing pigment stones in the main bile duct was examined using data obtained at 100, 200, 300, 400, and 500 days postinfection. Gallstone presence increased with infection time. The relative risk of gallstone disease increased when the number of flukes per rat and rat weight increased. The presence of gallstones was associated with serum high-density lipoproteins and triglyceride levels. In a multivariate analysis, the association between gallstones and rat weight disappeared after adjustment for serum lipids. The absence of an effect of rat weight independent from serum lipids suggests that serum lipids are more closely linked to gallstone pathogenesis than is overweight. The presence of gallstones was strongly associated with the number of flukes located in the bile duct. A high risk of developing gallstones may be expected in human subjects inhabiting areas where F. hepatica is highly endemic and where high egg outputs detected in humans suggest that liver fluke burdens may also be very high.

Phenotypic comparison of allopatric populations of Fasciola hepatica and Fasciola gigantica from European and African bovines using a computer image analysis system (CIAS)

The quantification of the different sizes and shapes of Fasciola hepatica and Fasciola gigantica from bovines has been achieved for the first time in natural allopatric populations. Linear measurements, areas and ratios of gravid adults and eggs of F. hepatica (from France and Spain) and F. gigantica (from Burkina Faso) were analysed using a computer image analysis system and an allometric model: % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada % WcgaqaamaabmaabaGaamyEamaaBaaaleaaruavP1wzZbItLDhis9wB % H5gaiuaacaWFYaGaaeyBaaqabaGccqGHsislcaWG5bWaaSbaaSqaai % aa-jdaaeqaaaGccaGLOaGaayzkaaaabaGaamyEamaaBaaaleaacaWF % YaaabeaaaaGccqGH9aqpcaWGJbWaamWaaeaadaWcgaqaamaabmaaba % GaamyEamaaBaaaleaacaWFXaGaaeyBaaqabaGccqGHsislcaWG5bWa % aSbaaSqaaiaa-fdaaeqaaaGccaGLOaGaayzkaaaabaGaamyEamaaBa % aaleaacaWFXaaabeaaaaaakiaawUfacaGLDbaadaahaaWcbeqaaiaa % dkgaaaaaaa!546F!

Neurological and ocular fascioliasis in humans.

{{\left( {y_{{2{\text{m}}}} - y_{2} } \right)}} \mathord{\left/ {\vphantom {{{\left( {y_{{2{\text{m}}}} - y_{2} } \right)}} {y_{2} }}} \right. \kern-\nulldelimiterspace} {y_{2} } = c{\left[ {{{\left( {y_{{1{\text{m}}}} - y_{1} } \right)}} \mathord{\left/ {\vphantom {{{\left( {y_{{1{\text{m}}}} - y_{1} } \right)}} {y_{1} }}} \right. \kern-\nulldelimiterspace} {y_{1} }} \right]}^{b}

Administration of triclabendazole is safe and effective in controlling fascioliasis in an endemic community of the Bolivian Altiplano.

, where y1=body area or body length, y2=one of the measurements analysed, y1m, y2m=maximum values towards which y1 and y2, respectively, tend and c, b=constants. All the measurements overlap in the two fasciolids, apart from the distance between the ventral sucker and the posterior end of the body, body roundness and body length/body width ratio. The results obtained may be useful in Fasciola species identification in countries where both species coexist.

Plant-Borne Trematode Zoonoses: Fascioliasis and Fasciolopsiasis

Background The Atlixco municipality, Puebla State, at a mean altitude of 1840 m, was selected for a study of Fasciola hepatica infection in schoolchildren in Mexico. This area presents permanent water collections continuously receiving thaw water from Popocatepetl volcano (5426 m altitude) through the community supply channels, conforming an epidemiological scenario similar to those known in hyperendemic areas of Andean countries. Methodology and Findings A total of 865 6–14 year-old schoolchildren were analyzed with FasciDIG coproantigen test and Lumbreras rapid sedimentation technique, and quantitatively assessed with Kato-Katz. Fascioliasis prevalences ranged 2.94–13.33% according to localities (mean 5.78%). Intensities were however low (24–384 epg). The association between fascioliasis and the habit of eating raw vegetables was identified, including watercress and radish with pronouncedly higher relative risk than lettuce, corncob, spinach, alfalfa juice, and broccoli. Many F. hepatica-infected children were coinfected by other parasites. Entamoeba histolytica/dispar, Giardia intestinalis, Blastocystis hominis, Hymenolepis nana and Ascaris lumbricoides infection resulted in risk factors for F. hepatica infection. Nitazoxanide efficacy against fascioliasis was 94.0% and 100% after first and second treatment courses, respectively. The few children, for whom a second treatment course was needed, were concomitantly infected by moderate ascariasis burdens. Its efficacy was also very high in the treatment of E. histolytica/E. dispar, G. intestinalis, B. hominis, H. nana, A. lumbricoides, Trichuris trichiura, and Enterobius vermicularis. A second treatment course was needed for all children affected by ancylostomatids. Conclusions Fascioliasis prevalences indicate this area to be mesoendemic, with isolated hyperendemic foci. This is the first time that a human fascioliasis endemic area is described in North America. Nitazoxanide appears as an appropriate alternative to triclabendazole, the present drug of choice for chronic fascioliasis. Its wide spectrum efficacy against intestinal protozooses and helminthiasis, usually coinfecting liver fluke infected subjects in human endemic areas, represents an important added value.