Dynamics of Fasciola hepatica transmission in the Andean Patagonian valleys, Argentina.

We described the transmission dynamics of Fasciola hepatica at its southern distribution range. Studies of prevalence and egg output in cattle and population dynamics and infection in snails were performed in a farm in the Andean Patagonian valleys, Argentina, between December 1998 and February 2002. Snail surveys were conducted from spring to autumn. Infection was diagnosed coprologically in the whole herd at the beginning and end of the study, and in a cohort of heifers at the beginning and end of 2001. A twice-a-year anthelmintic treatment was implemented in 1999. The relationship of the variables mentioned above with temperature and rainfall was determined. Lymnaea viatrix showed a life-span of about 15 months and an annual pattern of population dynamics. Specimens were frequently found in temporary environments and lagoons, and rarely in streams. Snail abundance and soil-water availability were directly related in temporary environments and inversely related in lagoons. Overall prevalence in L. viatrix was 0.67% (range: 0.9-14%) and infection was detected in summer and autumn. At the beginning of the study, calves were the least infected age group (15%). Prevalences and median egg counts in grazing animals were similar at the beginning (heifers: 81%, 3.3 epg; cows: 60%, 1.3 epg) and end of the study (heifers and cows: around 51%, 1 epg). Likewise, the prevalence in the cohort of heifers remained similar (around 40%) between surveys. Transmission to cattle was highly effective despite of the short activity period and the low infection rate of snails, and the regular anthelminthic treatment. There would be two seasonal transmission peaks, one in summer-autumn, when infected snails were present, and the other in early spring due to overwintering metacercariae. Some recommendations based on the climatic conditions of the region are provided to minimize snail infection and ultimately to reduce the incidence of fasciolosis in cattle.

[A focus study from a case of human fascioliasis in Neuquén]. / Estudio del foco en un caso de fasciolosis humana en Neuquén.

An epidemiological focal study was performed in Loncopué, Neuquén, Argentina, in November 2002 to detect the origin of the infection in a human case of fascioliasis confirmed by an indirect-ELISA test, six months before the study. Thirty five individual fecal samples were taken from domestic livestock, and watercress plants and snails were collected from the irrigation ditches connected to a main canal in the surroundings of the patient's house. A new blood sample was taken from the already recovered patient. The patient was still seropositive to Fasciola hepatica antigens. No metacercariae were found in the 222 watercress leaves checked. All the snails collected (n=130) were identified as Lymnaea viatrix and two out of 101 (2%) were infected with F. hepatica larvae. Coprological analysis showed F. hepatica eggs in 100% of goats (10/10), 82% of sheep (9/11) and 86% of bovines (6/7). The number of eggs per gram shed by positive goats (median=20.7, Q1=6.2, Q3=34.5) and sheep (4, 1.8, 13) was significantly higher than in cows (0.3, 0.3, 1.7) (p < 0.01). Local veterinary control programs were apparently not effective in this case. Anthelmintics used and treatment schedule should be revised and small herds raised at households should also be included and treated.

Southernmost finding of Lymnaea viatrix orbigny, 1835 (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica (Linnaeus, 1758) (Trematoda: Digenea), in urban and rural areas of Patagonia, Argentina.

We report the first finding of Lymnaea viatrix south of parallel 41 masculine S, in rural and urban areas from Argentina. Ninety snails were collected during year 2000, from a concrete pond at a Public Square in El Bolsón Village, Río Negro province, and 811 snails in November 1999, and during 2000 from waterbodies within a farm at Cholila locality, Chubut province. Fasciola hepatica infection was detected in 0.9% snails from the rural area. We discuss the potential risk of L. viatrix to public health in urban areas and its epidemiological importance in rural areas of the Andean Patagonian region.

First report of Lymnaea columella Say, 1817 (Pulmonata: Lymnaeidae) naturally infected with Fasciola hepatica (Linnaeus,1758) (Trematoda: Digenea) in Argentina.

We report the first evidence of natural infection of Lymnaea columella with Fasciola hepatica in Argentina. A sample of 601 snails was collected in May 2003 in northeastern Corrientes, a province bounded on the north by Paraguay, on the east by Brazil and on the southeast by Uruguay. Among 500 examined snails, 44 (8.8%) were exclusively infected with F. hepatica. Parasite identification was based on morphological features of cercariae from snails, and of eggs and adult flukes from Wistar rats. We discuss the events suggesting that an enzootic transmission cycle of F. hepatica has been recently established in northeastern Corrientes.

Fasciola hepática (linnaeus, 1758) (trematoda, digenea) en liebres europeas (lepus europaeus, pallas 1778) (lagomorpha, leporidae) en la región Cordillerana Patagónica, Chubut, Argentina / Fasciola hepatica (linnaeus, 1758) (trematoda, digenea) in the hare Lepus europaeus, pallas 1778 (lagomorpha, leporidae) from the Andean Patagonian Region, Chubut Province, Argentina

La liebre europea (Lepus europaeus) ha sido encontrada naturalmente infectada por Fasciola hepatica en varios países, pero en la Argentina no se han realizado estudios al respecto. Este trabajo tuvo por objetivo la búsqueda de infección en liebres de la zona cordillerana de la provincia del Chubut. Durante 1999 se faenaron 162.328 animales provenientes del noroeste de la provincia y se buscaron juveniles y adultos de F. hepatica. En enero y marzo de 2001 se recolectaron boñigas en cuerpos de agua de un establecimiento ganadero de la localidad de Cholila, al noroeste de la provincia del Chubut, donde estudios previos confirmaron la infección en ganado y caracoles. El 0,08 por ciento de las liebres faenadas presentó infección y en el ambiente se encontraron 6/10 boñigas positivas para F. hepatica en un charco (mediana de hpg = 2). A pesar de las bajas prevalencias halladas, el rol de L. europaeus en la transmisión del parásito podría ser importante si se considera que la especie comparte ambientes con el ganado y el caracol, su abundancia es alta, y la densidad de huevos que aporta al medio es mayor que la de bovinos.

Southernmost finding of Lymnaea viatrix orbigny, 1835 (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica (Linnaeus, 1758) (Trematoda: Digenea), in urban and rural areas of Patagonia, Argentina

We report the first finding of Lymnaea viatrix south of parallel 41ºS, in rural and urban areas from Argentina. Ninety snails were collected during year 2000, from a concrete pond at a Public Square in El Bolsón Village, Río Negro province, and 811 snails in November 1999, and during 2000 from waterbodies within a farm at Cholila locality, Chubut province. Fasciola hepatica infection was detected in 0.9 percent snails from the rural area. We discuss the potential risk of L. viatrix to public health in urban areas and its epidemiological importance in rural areas of the Andean Patagonian region.

First report of Lymnaea columella Say, 1817 (Pulmonata: Lymnaeidae) naturally infected with Fasciola hepatica (Linnaeus,1758) (Trematoda: Digenea) in Argentina

We report the first evidence of natural infection of Lymnaea columella with Fasciola hepatica in Argentina. A sample of 601 snails was collected in May 2003 in northeastern Corrientes, a province bounded on the north by Paraguay, on the east by Brazil and on the southeast by Uruguay. Among 500 examined snails, 44 (8.8 percent) were exclusively infected with F. hepatica. Parasite identification was based on morphological features of cercariae from snails, and of eggs and adult flukes from Wistar rats. We discuss the events suggesting that an enzootic transmission cycle of F. hepatica has been recently established in northeastern Corrientes.