A multidisciplinary analysis of over 53,000 fascioliasis patients along the 1995-2019 countrywide spread in Vietnam defines a new epidemiological baseline for One Health approaches.

Fascioliasis, only foodborne trematodiasis of worldwide distribution, is caused by Fasciola hepatica and F. gigantica, liver flukes transmitted by freshwater snails. Southern and southeastern Asia is an emerging hot spot of F. gigantica, despite its hitherto less involvement in human infection. In Vietnam, increasing cases have been reported since 1995, whereas only sixteen throughout 1800-1994. A database was created to include epidemiological data of fascioliasis patients from the 63 Vietnam provinces throughout 1995-2019. Case profiles were based on serology, symptoms, eosinophilia, imaging techniques, stool egg finding, and post-specific-treatment recovery. Radio broadcasting about symptoms and costless diagnosis/treatment led patients to hospitals after symptom onset. Yearly case numbers were modelled and spatio-temporally analyzed. Missing data and confounders were assessed. The countrywide spread has no precedent. It started in the central coast, including 53,109 patients, mostly adults and females. Seasonality, linked to vegetable consumption, peaks in June, although the intensity of this peak differs according to relief/climatic zones. Incidence data and logistic regression curves are obtained for the first time in human fascioliasis. Fasciolid hybrids accompanying the spreading F. gigantica flukes, and climate change assessed by risk index correlations, are both ruled out as outbreak causes. Human-guided movements of livestock from an original area prove to be the way used by fasciolids and lymnaeid vectors to expand geographically. Radix viridis, a highly efficient transmitting and colonizing vector, played a decisive role in the spread. The use of irrigated crop fields, widely inhabited by R. viridis, for livestock grazing facilitated the transmission and spread of the disease. General physician awareness and diagnostic capacity improvement proved the successful impact of such knowledge transfer in facilitating and increasing patient infection detection. Information, education and communication to the public by radio broadcasting demonstrated to be very helpful. Fasciola gigantica is able to cause epidemic and endemic situations similar to F. hepatica. The magnitude of the human outbreak in Vietnam is a health wake-up call for southern and southeastern countries of Asia which present the highest human population densities with increasing food demands, uncontrolled livestock inter-country exchange, foreign import practices, and monsoon's increasing climate change impact.

Erythrocyte micronucleus cytome assay of 17 wild bird species from the central Monte desert, Argentina.

Birds have the potential to be considered valuable bioindicators of the quality of ecosystems and the environmental impact of pollutants. The aims of this study were to determine the micronuclei frequency and other nuclear abnormalities in erythrocytes by analyzing a wild bird community from central Monte desert (Argentina) and to clarify if there were any differences among certain species. Frequencies of nuclear abnormalities were determined in 73 wild birds belonging to 17 species and two orders (Passeriformes and Columbiformes). A high proportion of individuals, 90.4 and 80.9 %, had erythrocytes with micronuclei and nuclear buds, respectively. Notched nuclei, binucleated cells, nuclear tails, and nucleoplasmic bridges were also recorded. Certain species appeared to be more informative than others with regard to the possibility of being used as bioindicators of genetic damage. Saltator aurantiirostris and Columbina picui were the only species that showed significantly different frequencies of nuclear alterations, in comparison with the other species. The frequencies here presented are the first reported for these bird species from the orders Passeriformes and Columbiformes. This research supports the notion that the use of these biomarkers could be effectively applied to evaluate spontaneous or induced genetic instability in wild birds.

Liver fluke (Fasciola hepatica) naturally infecting introduced European brown hare (Lepus europaeus) in northern Patagonia: phenotype, prevalence and potential risk.

Fascioliasis has recently been included in the WHO list of Neglected Zoonotic Diseases. Besides being a major veterinary health problem, fascioliasis has large underdeveloping effects on the human communities affected. Though scarcely considered in fascioliasis epidemiology, it is well recognized that both native and introduced wildlife species may play a significant role as reservoirs of the disease. The objectives are to study the morphological characteristics of Fasciola hepatica adults and eggs in a population of Lepus europaeus, to assess liver fluke prevalence, and to analyze the potential reservoir role of the European brown hare in northern Patagonia, Argentina, where fascioliasis is endemic. Measures of F. hepatica found in L. europaeus from northern Patagonia demonstrate that the liver fluke is able to fully develop in wild hares and to shed normal eggs through their faeces. Egg shedding to the environment is close to the lower limit obtained for pigs, a domestic animal whose epidemiological importance in endemic areas has already been highlighted. The former, combined with the high prevalence found (14.28%), suggest an even more important role in the transmission cycle than previously considered. The results obtained do not only remark the extraordinary plasticity and adaptability of this trematode species to different host species, but also highlight the role of the European brown hare, and other NIS, as reservoirs capable for parasite spillback to domestic and native cycle, representing a potentially important, but hitherto neglected, cause of disease emergence.

Modeling the extrinsic incubation of Dirofilaria immitis in South America based on monthly and continuous climatic data.

The spread and recrudescence of dirofilariosis across several regions, either caused by Dirofilaria immitis or D. repens, responds to many factors. Building upon the temperature model by Slocombe et al. (1989), a number of studies have been performed to generate predictive models for dirofilariosis. These studies have demonstrated the length of transmission periods and the number of Dirofilaria generations supported throughout several regions of the world (either at large or at small-scale). The usual procedure have proved to be extremely time consuming, as it appears impractical when assessing potential transmission at large scale, such as at a country or large-scale level. Due to the increasing need to suggest standardized surveillance protocols and apply adequate preventive measures at national and regional levels, a model for calculation of Dirofilaria HDUs based on monthly data was adapted for large-scale regional use. The models proposed are based on both point data (meteorological stations) and interpolated climate data layers (WorldClim). Three different models (daily and monthly models based on point data, and monthly model based on continuous data) were developed and compared statistically. When compared with the results from the classical daily model, the monthly models proposed accurately predicted the locations were extrinsic incubation was possible. These models proved to be adequate for the regional analysis of the extrinsic incubation of D. immitis and, hence, the relative risk of transmission in South America. Further, these models confirm that favorable temperatures for heartworm transmission in South America are present in most of the countries. D. immitis extrinsic incubation follows a seasonal pattern in Argentina, Chile, Uruguay, eastern Paraguay and southeastern Brazil; while in northern half of South America (less than 25° S) transmission may occur year-round. Moreover, high risk areas suitable for dirofilariasis transmission are not geographically constant throughout the year. The validation procedures indicate that the predicted HDU and HG maps are good predictors of dirofilariosis potential distribution, but estimating dirofilariosis prevalences based on them might not be completely accurate. The resulting distribution and seasonal maps would be useful for heartworm prevention by chemoprophylaxis in different regions known to be endemic for canine dirofilariasis. The information here provided can be an important tool in veterinary public health, as well as a guide for future research.

Detection of Dirofilaria immitis in mid-western arid Argentina.

Dirofilariosis, caused by Dirofilaria immitis and D. repens, is (re-) emerging worldwide. Dogs are the main reservoirs, while human infection has recently become an important focus of interest and attention. In Argentina, canine D. immitis infection has been described in eastern and northern subtropical and temperate humid regions, but never reported in mid-western arid regions so far. In this research note we report for the first time the occurrence of autochthonous human and canine D. immitis infection in the region.

Analysis of climate and extrinsic incubation of Dirofilaria immitis in southern South America.

Dirofilariosis, caused by Dirofilaria immitis and D. repens, is spreading in several geographic regions. The development of infective larvae in the mosquito vector (extrinsic incubation) needs an accumulated total of 130 degree-days above the 14 °C threshold, normally expressed as heartworm development units (HDUs). Based on this information, temperature- based models have been developed and applied to evaluate the distribution and spread of Dirofilaria infections in various countries and continents. Despite the confirmed presence of D. immitis in most South American countries, the available information about its epidemiology remains scarce. We analysed the temporal and spatial extrinsic incubation of this parasite in Argentina, Chile and Uruguay, taking into account daily temperatures from 49 meteorological stations during a 30-year period (1982-2012). The theoretically possible number of D. immitis generations was calculated based on the number of meteorological stations that reached the 130-HDUs threshold. The resulting information was spatially interpolated using the inverse weighted distance (IWD) model to produce thematic maps. The model shows that 41 of the meteorological stations reach the threshold needed and that D. immitis transmission is markedly seasonal with a peak in late spring (December), stable during summer (January to March) and declining in the autumn (April and May). Suitable temperatures exist in Uruguay and most of Argentina, whereas D. immitis transmission in Chile is only possible in the north and in the central inlands. The results suggest that the climatic impact on D. immitis transmission must have been minimal in the countries investigated since the annual meteorological records did not change much during the 30-year period analysed.

Análisis espacial de la fascioliasis humana y animal en la provincia de Mendoza / Spatial analysis of human and animal fascioliasis in the province of Mendoza

INTRODUCCIÓN En América, la fascioliasis es ocasionada por fasciola hepática. En Argentina, la fascioliasis animal es ampliamente reconocida, en tanto que la afección humana no es considerada de importancia. OBJETIVOS Mapear la distribución de la fascioliasis humana y animal en la provincia de Mendoza. Relacionar la distribución detectada a través del análisis espacial de factores ambientales. MÉTODOS Se relevó la presencia de vectores y de animales afectados por fasciola hepática en Mendoza. A partir de los sitios con presencia confirmada, se extrajeron los valores de variables ambientales seleccionadas, que se utilizaron para componer un modelo de distribución. Finalmente, se elaboraron mapas que representaban las zonas de mayor riesgo de transmisión. RESULTADOS Se observó que la distribución potencial de vectores y el área de transmisión de fascioliasis ocupan un 20,5% y un 17,9%, respectivamente. En el oeste montañoso, ambas distribuciones se limitarían a valles andinos, con pendientes no mayores a 5 grados y condiciones ambientales propicias. Un 5,1% y 7,3% de la superficie total de la provincia son altamente propicios para la presencia de vectores y de alto riesgo de transmisión, respectivamente. DISCUSIÓN La aparente abundancia de reservorios, la amplia difusión del vector y las áreas propicias para la transmisión sugieren que la casuística humana en la provincia de Mendoza no refleja la verdadera situación epidemiológica.