Dicrocoeliidae Family: Major Species Causing Veterinary Diseases.

This chapter analyses the taxonomic position of Dicrocoeliidae family and several of its genus and species. The biology of the major species causing veterinary diseases such Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum, has been reviewed. All these species have an indirect life cycle, involving two intermediate hosts (molluscs as first and ants, grasshoppers and lizards as second). Dicrocoelium dendriticum is a very widespread hepatic trematode in the ruminants of many countries in Europe, Asia, North Africa and North America, even affecting humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, whilst D. chinensis has mainly been found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite whose adults live in ruminant bile ducts, gall bladder, pancreatic ducts and intestines in Europe, Madagascar, Asia and South America. Adult P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information about the epidemiology, pathology, clinical aspect, diagnosis, treatment, control, prevention and economic impact mainly of Dicrocoeliosis produced by D. dendriticum, as well as of Eurytrematodosis and Platynosomiosis, has been included.

Pathological changes in cattle naturally infected by Calicophoron daubneyi adult flukes.

Local host response and parasite distribution were studied in the forestomachs, abomasum, duodenum and regional lymph nodes of cattle suffering from bovine paramphistomosis. The parasites were found attached, by its ventral sucker, to small conical papillae of the rumen and reticulum. Affected papillae, showed morphological changes denoted by very narrow stalks and expanded heads. Histologically, these changes were characterized by epithelial acanthosis-hyperkeratosis of the epithelium. Infiltration of inflammatory cells was often related with the epithelial changes, although it was also found in the duodenal mucosa and submucosa. These cells were arranged as aggregates or follicles but sparse infiltration of eosinophils, globule leukocytes, mast cells or macrophages was also observed in the lamina propria. Tissue damage and inflammatory reaction were more severe in the ruminal atrium, where the largest number of flukes and affected papillae were observed. In contrast, lesions in the ruminal dorsal sac were absent or mild. Statistical correlation between lesion severity and parasite burden was confirmed.

Calicophoron daubneyi (Paramphistomidae) in slaughtered cattle in Castilla y León (Spain).

The prevalence and aetiology of natural paramphistomosis was investigated in cattle slaughtered in the Castilla y León region (Spain) over a 3 year-period. The overall prevalence of positive animals was 6.20%. The parasite burden per animal ranged from 8 to 8005 (median=144) and the ruminal atrium had the highest parasite burden whereas the ruminal dorsal sac the lowest. The prevalence and parasite burden increased with age while these parameters were lower in cattle under intensive management. Calicophoron daubneyi was the only Paramphistomidae species identified using morphoanatomical, histological and molecular methods in the studied animals.

The wild boar (Sus scrofa Linnaeus, 1758) as secondary reservoir of Fasciola hepatica in Galicia (NW Spain).

Fasciolosis is an emerging or reemerging human and animal disease in numerous parts of the world. In Galicia (NW, Spain), the wild boar (Sus scrofa) is the main wild ungulate in terms of abundance and distribution. Its population has continuously increased over the past decades and this population growth has been accompanied by a reduction of habitats, so that the wild boar populations encroach more and more frequently onto agricultural lands. The increase of the interface area between livestock and the wild boars frequently involves the sharing of pastures and water sources, so that the circulation of common pathogens is propitiated. This is the first report concerning the importance of the wild boar as a possible reservoir of Fasciola hepatica infection in Spain. Livers from 358 hunted wild boars were analyzed showing that 11.2% were parasitized by F. hepatica, with burdens ranging from 1 to 14 flukes (mean=2.3). Fecal analysis demonstrated that 40.0% of parasitized animals shed F. hepatica eggs with a mean excretion of 6.1 eggs per gram of feces (epg). The presence of coproantigens analyzed by MM3-COPRO ELISA was positive in 62.9% of infected wild boars. After incubation, the percentage of hatched eggs ranged between 41.0% and 90.0% suggesting that the wild boar is very likely to contribute to the environmental contamination with viable parasite eggs. Comparative morphometric data were obtained using a computer image analysis system (CIAS) on the basis of standardized measurements. F. hepatica from cattle, sheep and wild boars from the same geographical area presents a similar body development and gravidity. Our study shows for the first time that the F. hepatica uterus from the wild boar presents an intermediate size between that found in primary reservoir hosts such as cattle and sheep, i.e., the individual potential egg output capacity of the wild boar does not greatly differ from that detected in Galician livestock. These results show that F. hepatica in Galicia has a normal development in wild boars, presenting its own characteristics in shape and size in comparison with other host species. The high prevalence of infection detected in the wild boar, the normal fluke development in the liver, and the possibility of shedding F. hepatica eggs capable of embryonating and giving rise to viable miracidia with the potential to infect intermediate hosts suggest a possible role of this species as a secondary reservoir in this Spanish region.

A tool for diagnosis of Dicrocoelium dendriticum infection: hatching eggs and molecular identification of the miracidium.

DNA primers were designed from the 18S rRNA sequence from the relevant digenean trematode Dicrocoelium dendriticum to evaluate a polymerase chain reaction-based diagnostic method of this parasite from its eggs in faeces of naturally and experimentally infected sheep. In order to get DNA from D. dendriticum eggs, several hatching mechanisms were studied. Successful results were obtained when the eggs were frozen to -80 °C and/or in liquid nitrogen and then defrosted. This method allowed the opening of the egg operculum and the liberation of the miracidium. DNA from D. dendriticum adults and from hatching egg miracidia was obtained and an amplification single band of 1.95 kb was observed using primers designed for the total 18S rRNA sequence in both cases as well as when the template DNA was from adults of the closely related parasite Fasciola hepatica; in addition, a single and specific 0.8-kb band was obtained when primers based on an internal partial 18S rRNA sequence were used. The method showed to be useful not only in samples coming from adults, but in eggs from gall bladder and faeces as well. F. hepatica internal 18S rRNA primers were also designed and used as a negative control to prove that the eggs in faeces came from D. dendriticum and not from F. hepatica. A molecular tool able to detect a minimum of about 40 D. dendriticum eggs in one of the definitive host faeces has been developed for the first time and could provide a useful molecular tool to improve the conventional coprological diagnosis for detecting D. dendriticum eggs.

Evaluación de dos modelos quimioterapéuticos para el control de fasciolasis bovina en clima cálido-húmedo en México / Evaluation of chemotherapeutic models for the control of Fasciola hepatica in cattle in humid warm climate in Mexico

Con el objetivo de evaluar dos modelos de control quimioterapéutico contra Fasciola hepatica, en ganado bovino infectado de manera natural y localizado en una finca en el municipio de Nautla, Veracruz, México, se aplicó el triclabendazol (tbz) en una o dos ocasiones, en diferentes meses, para reducir al máximo la eliminación de huevos. Además, se determinaron los valores de anticuerpos anti-F. hepatica y los niveles séricos de gamma-glutamil transpeptidasa (ggt) y aspartato aminotransferasa (ast). Se trataron dos grupos (G) de 23 animales cada uno, con dosis de 12 mg/kg de tbz, el G-1, testigo, en enero y el G-2 en enero y mayo. Cada 45 días, durante 10 ocasiones, se recolectaron muestras de heces de todos los animales, para realizar el recuento de huevos en 5 g (hpg). Al mismo tiempo, se tomaron muestras de sangre de 15 vacas de cada grupo, con el fin de detectar en el suero, mediante ELISA, los anticuerpos anti-F. hepatica, así como valorar los niveles de ggt y ast por espectometría. El porcentaje de reducción de tasa de la media de hpg fue 27.6 más alto en el G-2 que en el G-1, lo que concuerda con los valores más bajos de ggt detectados en el G-2. Los valores medios de la ast no rebasaron el límite normal. Los niveles de anticuerpos fueron positivos y no parecen verse afectados por el tratamiento con tbz en ninguno de los grupos.

Eficacia del fenbendazol por vía tópica contra nematodos gastrointestinales y pulmonares de ganado bovino en clima cálido húmedo / Efficacy of fenbendazole Pour-on againts gastrointestinal and lungworm nematodes in bovines in Mexico

Se hicieron dos experimentos para valorar la reducción en el número de huevos por gramo de heces (hpgh) de nematodos gastrointestinales y larvas de vermes pulmonares en bovinos, localizados en el Centro experimental Pecuario del Estado de Puebla, México. En el primer experimento se utilizaron cinco lotes de 11 a 13 becerros cada uno, parasitados de manera natural con nematodos gastrointestinales. Los animales de los lotes 1, 2 y 3 se trataron por vía tópica, con dosis de 5, 7.5 y 10 mg/kg de fenbendazol preparado para su aplicación por vía tópica; los del lote 4 recibieron una dosis oral de 5 mg/kg y los del lote 5 se mantuvieron como testigos. La eficacia en la reducción de huevos en los lotes tratados, a los 7 día postratamiento, fue de 82.01 por ciento, 98.35 por ciento, 96.42 por ciento y 93.40 por ciento, respectivamante. El segundo experimento se realizó en cuatro lotes de 12 becerros parasitados con nematodos gastrointestinales y positivos a larvas de Dictyocaulus viviparus. Tres lotes se trataron con 5, 7.5 y 10 mg/kg de fenbendazol por vía tópica y el 4º se dejó como testigo. La eficacia de dichas dosis en la reducción de hpgh de nematodos gastrointestinales, fue 99.33 por ciento, 99.16 por ciento y 100 por ciento, respectivamente, y en la reducción de las muestras positivas a larvas del D. viviparus fue de 100 por ciento, 91.66 por ciento y 100 por ciento, respectivamante. El moderado descenso observado en la eficacia del fenbendazol aplicado por vía tópica en el Experimento 1, pudo ser debido al deslave del antihelmíntico producido por el fuerte aguacero que cayó al finalizar la aplicación del tratamiento. Mediante el análisis de varianza de una vía y el test LSD se detectaron diferencias estadísticamente significativas en la eficacia del fenbendazol, en la reducción de huevos de nematodos gastrointestinales, ante el lote del primer experimento tratado con 5 mg/kg y cada uno de los restantes lotes tratados, de ambos experimentos, por la misma vía. Los géneros de dichos nematodos identificados en los coprocultivos a través de larvas III, en ambos experimentos, fueron: Haemonchus, Trichostrongylus, Cooperia, Oesophagostomum y Bunostomum