Características clínicas e histopatológicas de melanoma subungueal en 57 pacientes mexicanos: una cohorte de 5 años / Clinical and Histopathologic Features of Subungual Melanoma in 57 Mexican Patients: A 5-Year Cohort Study

El melanoma subungueal es un tumor poco común, con peor pronóstico comparado con los de otras localizaciones. Corresponde al 1-23% de los melanomas, según la población. El objetivo de este estudio fue describir las características clínicas e histopatológicas del melanoma subungueal en la población mexicana. Se incluyeron 57 pacientes con melanoma subungueal (19% de los 303 melanomas totales), con una mediana de edad de 71 años. La localización predominante fueron los miembros inferiores (52,6% de los melanomas subungueales) y el primer dedo (75,4% de los casos). El subtipo histológico más frecuente fue el acral lentiginoso (50,9%). La mediana de Breslow fue de 3mm. El estadio IA fue el más frecuente (28,1%). Se encontró una tasa de recurrencia del 19,3% y de metástasis del 8,8%. Las características clínico-patológicas fueron semejantes a lo descrito en la literatura. Es importante realizar un diagnóstico y tratamiento tempranos de cara a mejorar su pronóstico.(AU)

Although subungual melanoma is uncommon, it is associated with worse outcomes than melanomas in other locations and accounts for 1% to 23% of all melanomas, depending on the population. The aim of this study was to describe the clinical and histopathologic features of subungual melanoma in a Mexican population. We identified 303 patients with melanoma, and of these, 19% (57 patients with a median age of 71 years) had subungual melanoma. The main sites affected were the lower limbs (52.6%) and the toe (75.4%). The most common histologic subtype was acral lentiginous melanoma (50.9%). Median Breslow thickness was 3 mm, and stage IA tumors were the most common (in 28.1% of patients). Recurrence and metastasis occurred in 19.3% and 8.8% of patients, respectively. The clinical and histopathologic features identified are similar to those described in the literature. Early diagnosis and treatment are crucial for improving prognosis.(AU)

[Translated article] Clinical and Histopathologic Features of Subungual Melanoma in 57 Mexican Patients: A 5-Year Cohort Study / Características clínicas e histopatológicas de melanoma subungueal en 57 pacientes mexicanos: una cohorte de 5 años

El melanoma subungueal es un tumor poco común, con peor pronóstico comparado con los de otras localizaciones. Corresponde al 1-23% de los melanomas, según la población. El objetivo de este estudio fue describir las características clínicas e histopatológicas del melanoma subungueal en la población mexicana. Se incluyeron 57 pacientes con melanoma subungueal (19% de los 303 melanomas totales), con una mediana de edad de 71 años. La localización predominante fueron los miembros inferiores (52,6% de los melanomas subungueales) y el primer dedo (75,4% de los casos). El subtipo histológico más frecuente fue el acral lentiginoso (50,9%). La mediana de Breslow fue de 3mm. El estadio IA fue el más frecuente (28,1%). Se encontró una tasa de recurrencia del 19,3% y de metástasis del 8,8%. Las características clínico-patológicas fueron semejantes a lo descrito en la literatura. Es importante realizar un diagnóstico y tratamiento tempranos de cara a mejorar su pronóstico.(AU)

Although subungual melanoma is uncommon, it is associated with worse outcomes than melanomas in other locations and accounts for 1% to 23% of all melanomas, depending on the population. The aim of this study was to describe the clinical and histopathologic features of subungual melanoma in a Mexican population. We identified 303 patients with melanoma, and of these, 19% (57 patients with a median age of 71 years) had subungual melanoma. The main sites affected were the lower limbs (52.6%) and the toe (75.4%). The most common histologic subtype was acral lentiginous melanoma (50.9%). Median Breslow thickness was 3 mm, and stage IA tumors were the most common (in 28.1% of patients). Recurrence and metastasis occurred in 19.3% and 8.8% of patients, respectively. The clinical and histopathologic features identified are similar to those described in the literature. Early diagnosis and treatment are crucial for improving prognosis.(AU)

[Translated article] Clinical and Histopathologic Features of Subungual Melanoma in 57 Mexican Patients: A 5-Year Cohort Study.

Although subungual melanoma is uncommon, it is associated with worse outcomes than melanomas in other locations and accounts for 1% to 23% of all melanomas, depending on the population. The aim of this study was to describe the clinical and histopathologic features of subungual melanoma in a Mexican population. We identified 303 patients with melanoma, and of these, 19% (57 patients with a median age of 71 years) had subungual melanoma. The main sites affected were the lower limbs (52.6%) and the toe (75.4%). The most common histologic subtype was acral lentiginous melanoma (50.9%). Median Breslow thickness was 3 mm, and stage IA tumors were the most common (in 28.1% of patients). Recurrence and metastasis occurred in 19.3% and 8.8% of patients, respectively. The clinical and histopathologic features identified are similar to those described in the literature. Early diagnosis and treatment are crucial for improving prognosis.

Clinical and Histopathologic Features of Subungual Melanoma in 57 Mexican Patients: A 5-Year Cohort Study. / Características clínicas e histopatológicas de melanoma subungueal en 57 pacientes mexicanos: una cohorte de 5 años.

Although subungual melanoma is uncommon, it is associated with worse outcomes than melanomas in other locations and accounts for 1% to 23% of all melanomas, depending on the population. The aim of this study was to describe the clinical and histopathologic features of subungual melanoma in a Mexican population. We identified 303 patients with melanoma, and of these, 19% (57 patients with a median age of 71 years) had subungual melanoma. The main sites affected were the lower limbs (52.6%) and the toe (75.4%). The most common histologic subtype was acral lentiginous melanoma (50.9%). Median Breslow thickness was 3 mm, and stage IA tumors were the most common (in 28.1% of patients). Recurrence and metastasis occurred in 19.3% and 8.8% of patients, respectively. The clinical and histopathologic features identified are similar to those described in the literature. Early diagnosis and treatment are crucial for improving prognosis.

Characterization of minimal lesions related to the presence of visna/maedi virus in the mammary gland and milk of dairy sheep.

BACKGROUND: In order to characterize the complete range of lesions, especially minimal, affecting mammary gland and viral antigen distribution and target cells using immunohistochemistry in naturally Visna/maedi (VM) 84 infected sheep were studied, forty-four from flocks with clinical cases (A) and 35 randomly sampled from two abattoirs (B) together with five negative controls (C). An immunocytochemistry technique was developed and further milk samples (n = 39) were used to study viral excretion, carrier cells and the role of milk and colostrum in the transmission of the disease. RESULTS: All sheep from group C and three sheep from group B were negative to VM in tissue sections by histopathology, immunohistochemistry and PCR, and also in serum using ELISA. Several degrees of CD3 + lymphocytic interstitial mastitis were observed in groups A and B: minimal (+) n = 26 sheep; moderate (++), n = 32 and severe (+++), n = 12. No differences in lesion distribution were observed between groups A and B. Viral presence was confirmed by immunohistochemistry using two different antibodies and/or PCR in every tissue with lesions while serology was negative in six sheep with lesions. Two milk samples taken from milk tanks from two flocks from group A and fourteen milk samples from 29 infected sheep from group B were positive to VM (most of them from animals with moderate and severe lesions). Positivity was only found in macrophages, even in focal and minimal lesions, while no positivity was observed in epithelial or any other cells in either tissue and milk samples. CONCLUSIONS: This new observation of the minimal lesions described in this work increased the prevalence of VM lesions in mammary gland up to 90.9% and VM should be considered as a differential diagnosis when minimal interstitial lesions are detected. A high prevalence of VM was observed in intensive milk-producing sheep, ELISA serology did not detect as positivity all infected animals, while histology, IHC or PCR showed higher sensitivity. The cytological technique developed was very useful in milk-cell studies using hematoxylin and eosin and immunocytochemistry. Viral detection in milk samples (16/39) confirms a potential but limited role of milk/colostrum in viral transmission.

Tspan33 is Expressed in Transitional and Memory B Cells, but is not Responsible for High ADAM10 Expression.

Tetraspanins are a family of transmembrane proteins that form membrane microdomains. They play important roles in migration, adhesion and other cellular processes. TspanC8, a subfamily of tetraspanins, was found to associate and promote ADAM10 trafficking and cell surface localization. One of its members, Tspan33, is expressed in activated B cells. Using RT-PCR and flow cytometry, we analysed the pattern of expression of Tspan33 in B cells from healthy donors. We found Tspan33 expression in early and late stages of B cell development. However, Tspan33 expression did not correlate with ADAM10 surface expression. We also found expression of Tspan33 early in the activation process. Given its predominant expression in activated B cells and in several lymphomas, but not in naive B cells, we hypothesize that Tspan33 could be a potential target for therapeutic purposes.

Retención urinaria posparto: conducta clínica y modelos experimentales para su estudio / Postpartum urinary retention: clinical behavior and experimental models for study

Resumen ANTECEDENTES: puesto que la retención urinaria posparto no es un suceso que se considere grave, la información de su tratamiento en las unidades obstétricas es muy limitada, sobre todo en América Latina. MÉTODO: búsqueda de información publicada, en español e inglés, entre los años 2000 y 2016 relacionada con las medidas preventivas y tratamientos de la retención urinaria posparto en dos bases de datos de bibliografía biomédica: Pubmed y Scopus. RESULTADOS: se encontraron 31 artículos científicos en inglés relacionados con el tratamiento de la retención urinaria posparto y pocos estudios en modelos animales de retención urinaria aguda, ninguno en español. El diagnóstico de la retención urinaria posparto se establece con el auxilio de métodos invasivos y no invasivos: catéteres y ultrasonido. El tratamiento incluye acciones preventivas (reducción de problemas del parto mediante adiestramiento adecuado del personal de las unidades obstétricas o la aplicación de masaje en la región sacra) y posteriores al parto (uso de catéteres uretrales o suprapúbicos). CONCLUSIONES: la retención urinaria posparto es una complicación clínica que requiere entender que el diagnóstico y tratamiento tempranos contribuyen sustancialmente a disminuir la alta prevalencia de disfunciones vesicales femeninas. En esta revisión se evidenció la necesidad de estudios preclínicos que permitan conocer la repercusión a largo plazo de la retención urinaria y probar nuevos tratamientos.

Abstract BACKGROUND: since postpartum urinary retention is not a condition that is considered severe, information of its treatment in obstetrical units is very limited, especially in Latin America. METHOD: search of published information in Spanish and English, between 2000 and 2016 related to preventive measures and treatment of postpartum urinary retention in two data bases of biomedical bibliography: Pubmed and Scopus. RESULTS: 31 scientific articles in English related to the treatment of postpartum urinary retention were found as well as a few studies of acute urinary retention in animal models, none of them in Spanish. The diagnosis of postpartum urinary retention is established using invasive and non-invasive methods: catheters and ultrasound. Treatment includes preventive measures (reduction of delivery issues through appropriate training of obstetrical unis or the use of massage on the sacral region) and after delivery (use of urethral or suprapubic catheters). CONCLUSIONS: postpartum urinary retention is a clinical complication, thus we have to understand that early diagnosis and treatment substantially contribute to decreasing the high prevalence of female bladder dysfunctions. In this review, we proved the need for preclinical tests that allow us to recognize the long term repercussion of urinary retention and test new treatments.

Estudio de los efectos de las lesiones del labrum acetabular en la cadera en un modelo experimental lagomorfo adulto / Study of the effects of the hip acetabular labrum damage in a rabbit animal model

Objetivo: El cartílago labral es una estructura cartilaginosa que recubre el acetábulo de la cadera. Su lesión es controvertida en cuanto a sus implicaciones debido a que no se conoce bien si es una causa de degeneración articular o sólo un cambio degenerativo más. Hemos diseñado un modelo animal en conejo para estudiar esta lesión. Material y metodología: Se utilizaron tres grupos de 13 animales a los que se lesionó una cadera dejando la otra como control y se les mantuvo estabulados al primer grupo 12 semanas, al segundo 18 y al tercero 30. Posteriormente se les realizó un estudio radiológico, otro por resonancia magnética y, tras su sacrificio, un estudio histológico. Resultados: No encontramos relación en nuestro modelo entre la lesión labral y los cambios degenerativos posteriores en los plazos citados. Tampoco encontramos daños labrales sin cicatrizar en el momento del sacrificio. Conclusión: En el modelo animal lagomorfo, la lesión labral no produce cambios degenerativos artrósicos y el cartílago labral podría presentar cierta capacidad de regeneración (AU)

Objective: The labrum is a cartilaginous structure that covers the hip acetabulum. The labral lesions are controverted because it is not known if the labral tears are a cause or a consequence of the hip osteoarthrosis. Material and methods: We designed a rabbit animal model to study the labral tears. We used three groups of 13 animals. We injured the labral cartilage of every rabbit in the right hip, and we used the left hip as a control. The animals were kept alive for 12, 18 and 30 weeks. We realized a radiologic, a magnetic resonance and a histological study in every rabbit to see the labral tears consequences. Results: We did not found in our model any significant relationship between the labral tears and the secondary osteoarthrosis in the studied time. We didn't found labral damage without heal when the animals were sacrificed. Conclusion: We can conclude, in the rabbit animal model, the labral tears don't produce degenerative changes in the hip. The labrum have regenerative capacity in the rabbit animal model (AU)

Time course of reendothelialization of stents in a normal coronary swine model: characterization and quantification.

Late thrombosis of coronary drug-eluting stents is an infrequent but serious complication of percutaneous transluminal coronary angioplasty. The best predictor of this event is the lack of endothelialization of stent struts. The objective of this study is to characterize and quantify the time course of endothelialization of different stents implanted in nonatherosclerotic swine coronary arteries. Thirty-three Carbofilm-coated stents were implanted percutaneously in 11 anesthetized domestic, crossbred pigs (weight 25 ± 3 kg, 2 months old). Each animal received 1 stainless steel stent (SS), 1 cobalt-chromium stent (CCS), and 1 tacrolimus-eluting stent (TES) in each coronary artery. Follow-up periods were 1 day (n = 9 stents), 3 days (n = 9 stents), and 7 days (n = 15 stents). Longitudinal sections of the stented vessels were examined using scanning electron microscopy. At 1 day, there was scarce, patchy endothelialization with areas of fibrin; the endothelialization rate was similar for all the stents (SS, 29% ± 23%; CCS, 29% ± 24%; TES, 31% ± 25%; P = .9). At 3 days, there were more endothelial cells but with immature features and giant cells over fibrin; the endothelialization was greater in SS and CCS than in TES (SS, 79% ± 14%; CCS, 81% ± 17%; TES, 46% ± 9%; P = .007). At 7 days, arteries showed better endothelialization with few giant cells; the endothelialization was greater in SS and CCS than in TES (SS, 95% ± 4%; CCS, 98% ± 4%; TES, 79% ± 9%; P = .01). In conclusion, the described model is useful for the analysis of endothelialization of coronary stents and facilitates measurement of its rate of formation and characterization of the involved cell types.

Undifferentiated high-grade pleomorphic sarcoma in a California sea lion (Zalophus californianus).

A tumour located in the pectoral region and the left front flipper was observed in a 29-year-old female California sea lion (Zalophus californianus) that died following signs of respiratory disease and inappetence. Metastases were present in the lung and adrenal gland. The histological pattern of the tumour was variable. In some areas the tumour consisted of pleomorphic fibroblast-like cells arranged in a storiform pattern, while in other areas it comprised oval or polygonal cells with round to oval nuclei and some bizarre cells arranged in an alveolar pattern. Occasionally, multinucleated giant cells were observed. Immunohistochemically, the neoplastic cells only expressed vimentin. On the basis of the microscopical and immunohistochemical features the tumour was diagnosed as an undifferentiated high-grade pleomorphic sarcoma. This type of neoplasm with disseminated involvement of other organs is rare in all species and has never been reported in California sea lions.

Effect of different vaccine formulations on the development of Glässer's disease induced in pigs by experimental Haemophilus parasuis infection.

Four groups of pigs immunized with different vaccines and a group of non-vaccinated controls were challenged intratracheally with a lethal dose (5 x 10(9) colony-forming units) of Haemophilus parasuis, the aetiological agent of Glässer's disease. A vaccine containing inactivated whole organisms gave strong protection against clinical signs, death, pathological changes and persistence of organisms in vivo. However, all non-immunized pigs, all pigs given a vaccine consisting of the recombinant transferring-binding protein (Tbp) B, some pigs given an outer membrane protein (OMP) formulation enriched with TbpB and some pigs immunized with a sub-lethal dose of live organisms died at various times after challenge, yielding positive cultures from most organs post mortem and having shown hyperthermia and other clinical signs before death. Animals that died showed fibrinosuppurative polyserositis, exudative pneumonia, and lesions compatible with acute septicaemia, e.g., disseminated intravascular coagulation with multiple fibrinous thrombi in arterioles and capillaries, depletion of splenic white pulp, and acute lymphadenitis. The results suggested that, in addition to the protection given by inactivated whole organisms, partial protection was given by the OMP formulation and by a sub-lethal dose of living organisms; however, the recombinant TbpB preparation gave no protection.

Histopathological and immunohistochemical characteristics of two canine lipid-rich mammary carcinomas.

Clinicopathological and immunohistochemical findings of two uncommon canine lipid-rich mammary carcinomas are described. The predominant histological feature in both tumours was the presence of at least 80% of cells with intracytoplasmic vacuoles which stained positively with Sudan IV but not with alcian-blue periodic acid-schiff method. In both tumours, small groups of non-vacuolated cells were identified among the vacuolated cells. However, histological and immunohistochemical differences were also found between these tumours. Thus, one of them was composed of tumour cells with a large and single vacuole, which were arranged in lobular pattern, while the other neoplasm showed an intraductal growth of tumour cells with a fine vacuolated cytoplasm. Immunohistochemically, in the first tumour most vacuolated cells were positive for CK (cytokeratin)8-7, indicating a secretory epithelial immunophenotype while CK5 and CK8-7-expressing non-vacuolated cells were associated with luminal duct immunophenotype. However, in the second tumour the expression of CK14 in most of vacuolated cells and alpha-smooth muscle actin (alpha-SMA) in non-vacuolated cells, alone or in combination with CK5 suggested a myoepithelial immunophenotype for both cell types. These results suggest heterogeneity of the cell type and growth pattern for this type of canine tumour as has been described in women but not in dogs.

Biological characterization of ovarian granulosa cell tumours of slaughtered cattle: assessment of cell proliferation and oestrogen receptors.

Of 1489 slaughtered cattle, 11 had ovarian granulosa cell tumours (GCTs). These GCTs were examined immunohistochemically for proliferating cell nuclear antigen (PCNA) and oestrogen receptor (ER) in relation to histopathological features (growth pattern, nuclear atypia and mitotic count). On the basis of nuclear atypia and mitotic count, the prognosis for GCTs with a diffuse growth pattern appeared less favourable than that for GCTs with a follicular or trabecular pattern. Increased PCNA expression was significantly associated with nuclear atypia but not with histological growth pattern or mitotic count. A novel finding was the presence of ERbeta but not ERalpha in bovine ovarian GCTs. However, ERbeta expression did not appear to be related to the histopathological features examined. The results indicate that PCNA expression may be of value in establishing the biological behaviour of bovine GCTs. However, a larger series of bovine GCTs should be examinated to assess the prognostic significance of ERbeta.

Expression of cytokeratins and vimentin in normal and neoplastic tissue from the bovine female reproductive tract.

The distribution of cytokeratins (CKs) and vimentin in the normal genital tract of calves and cows at different stages of the oestrous cycle and in epithelial tumours of the tract was studied immunohistochemically. Few differences in CK and vimentin immunolabelling were detected in relation to age or stage of the oestrous cycle. Coexpression of CKs in simple epithelia and in basal cells of stratified epithelia was detected in the oviduct and endocervix; this coexpression was different from that previously described in women. The demonstration of CKs but not vimentin in the neoplastic cells of a serous superficial ovarian papilloma suggested an origin from the ovarian surface epithelium, while the coexpression of CKs and vimentin in serous papillary and mucinous cystadenomas pointed to a possible origin from the rete ovarii. Studies on three uterine adenocarcinomas and the ovarian metastases from two of these showed an endometrial-CK phenotype. The intermediate filament profile of normal endometrium, conserved in uterine adenocarcinomas and their ovarian metastases, may be useful in discriminating between ovarian metastases from endometrial carcinomas and those originating from primary carcinomas in other organs.

Effects of retinoic acid exposure in utero on mouse vibrissal follicle development.

It is known that topical all-trans-retinoic acid (RA) modulates growth and differentiation of skin and its cutaneous appendages. To examine whether a pre-natal exposure to a potentially non-teratogenic dosage of all-trans-RA had any effect on vibrissal follicle development, the histologic and immunohistochemical responses to RA during its morphogenesis in NMRI mouse were investigated. After a single oral dose of 30 mg/kg body weight of all-trans-RA on day 11.5 of gestation, no fetal malformations were detected and the histological features and the distribution of keratin (K) proteins in comparable stages of vibrissal development were similar for the untreated, vehicle-treated and RA-treated mice. The absence of teratogenic response and of adverse effects on the vibrissae under the experimental conditions indicates that this protocol may be useful for investigation of the effects of pre-natal exposure to RA on the post-natal development of experimental tumours in the mouse skin.

Malignant fibrous histiocytoma (giant cell type) associated with a malignant mixed tumor in the salivary gland of a dog.

A 12-year-old male Boxer dog presented with a 5 x 5 x 7-cm partially encapsulated mass in the right mandibular salivary gland. Histologically, the mass was composed of neoplastic epithelial and mesenchymal cells. The mesenchymal component consisted of two cell populations arranged in different patterns: coalescing nodules of neoplastic mononuclear cells with rare osteoid and numerous osteoclastlike giant cells; and sheets of neoplastic spindle cells intermingled with neoplastic epithelial cells and containing osteoid and well-formed bone trabeculae lined by osteoblasts and few osteoclastlike giant cells. On the basis of these histological features, two malignant salivary tumors were diagnosed: a malignant fibrous histiocytoma (giant cell type) and a malignant mixed tumor. Immunohistochemical studies demonstrated keratin 5 and 8 expression by the neoplastic epithelial cells, indicating a probable salivary ductal origin, and vimentin expression by all mesenchymal elements, suggesting a fibroblastic line of differentiation.

Isolation of Actinobacillus seminis from the genital tract of rams in spain.

Actinobacillus seminis isolates were cultured from the semen (two isolates) and the left testis (one isolate) of two one-year-old rams in León, Spain. One animal showed lesions of chronic unilateral orchitis and epididymitis while the other appeared to suffer a subclinical infection and only a moderate number of pleomorphic rods and inflammatory cells were present in its semen. The isolates were biochemically similar to the A. seminis type strain NCTC 10851 and two other European A. seminis isolates, except that they produced acid from sorbitol; their identity was confirmed by arbitrarily primed polymerase chain reaction. The isolates were also tested against 30 antimicrobial agents, and only marbofloxacin was found active against all of them. As far as is known, this is the first report of A. seminis isolation from rams in southern Europe.

Extra-laryngeal head and neck tuberculosis.

OBJECTIVE: Extra-laryngeal head and neck tuberculosis is exceptional. Therefore, a retrospective multicenter study in patients with head and neck tuberculosis, excluding solitary lymphadenitis and laryngeal locations was carried out. METHODS: We reviewed the patients with these features and tuberculosis confirmation by culture and/or histologic granuloma with presence of acid-fast bacilli (AFB). RESULTS: We found 16 patients with the following locations: eight in oral cavity and/or pharynx, four in ear, two in salivary glands, one in nose and one in frontal sinuses. The average duration of symptoms was 11.5 months. Purified protein derivative (PPD) was positive (> 10 mm) in all but one patient in whom it was performed (six of seven). Except tuberculous otitis, which occured without reactive lymphadenitis, this was present in 50% of the rest (six of the 12). In all cases a biopsy was required for diagnosis. Only in four patients, all with pharyngeal locations, was coincident pulmonary tuberculosis confirmed. One patient with tuberculous otitis developed meningitis and died; three additional patients (two with otitis) were cured but with sequelae; the evolution of the remaining patients was satisfactory with medical therapy. CONCLUSIONS: Extra-laryngeal head and neck tuberculosis has a slow course. The diagnosis is difficult due to the common absence of lung involvement and the usual requirements for biopsy procedures. The outcome is usually favorable with antituberculous drugs alone although in tuberculous otitis there are possibilities of complications.

Histopathological and immunohistochemical study of lambs experimentally infected with Fasciola hepatica and Schistosoma bovis.

The aim of this study was to investigate the cross-resistance between Fasciola hepatica and Schistosoma bovis in lambs assessing parasitologic, gross pathologic, histopathologic and immunohistochemical changes in liver and small intestine. Thirty Castellana breed lambs were divided into five comparable groups and exposed to F. hepatical S. bovis (group F/S), S. bovis/F. hepatica (group S/F), S. bovis (group S) or F. hepatica (group F) and six unexposed lambs were used as non-infected controls (group C). Primary patent infection with F. hepatica induced a lower number of schistosome eggs and a higher number of lymphocytes in intestinal and liver schistosome egg-induced granulomas in group F/S than in the groups S/F and S, liver damage being mainly attributed to F. hepatica. S. bovis infection followed by challenge with F. hepatica particularly increased the severity of the most significant liver alterations (cholangiohepatitis by F. hepatica and mesoendophlebitis by S. bovis) and F. hepatica seemed not to have an influence on established S. bovis infection. In addition, immunohistochemical results suggested that the predominant local immune response in both double-infected groups was different, being mainly a cell-mediated immune response in group F/S and a mucosal response in group S/F.