Small Ruminant Lentiviruses in Sheep: Pathology and Tropism of 2 Strains Using the Bone Marrow Route.

The objective of this work was to comparatively study the tissue tropism and the associated pathology of 2 autochthonous small ruminant lentivirus (SRLV) field strains using an experimental infection in sheep through the bone marrow. Fifteen male, SRLV-free lambs of the Rasa Aragonesa breed were inoculated with strain 697 (nervous tissue origin, animals A1-A6), with strain 496 (articular origin, animals B1-B6), or with uninfected culture medium (C1-C3). Clinical, serologic, and polymerase chain reaction (PCR) evaluations were performed periodically. Two lambs from each infected group and a control animal were euthanized at 134, 273, and 319 days postinfection. Tissues were analyzed by gross and histopathologic evaluation; immunohistochemistry for CD3, CD4, CD8, CD68, and FoxP3 cell markers; lung morphometric evaluation; and tissue proviral quantification by PCR. All infected animals became positive either by enzyme-linked immunosorbent assay and/or PCR, with group B lambs showing the highest serologic values and more consistently positive PCR reactions. Group A lambs showed representative lung lesions but only mild histopathologic changes in the central nervous system (CNS) or in carpal joints. Contrarily, group B lambs demonstrated intense carpal arthritis and interstitial pneumonia but an absence of lesions in the CNS. Proviral copies in tissues were detected only in group B lambs. Experimental infection with these SRLV strains indicates that strain 496 is more virulent than strain 697 and more prone to induce arthritis, whereas strain 697 is more likely to reproduce encephalitis in Rasa Aragonesa lambs. Host factors as well as viral factors are responsible for the final clinicopathologic picture during SRLV infections.

Small ruminant lentivirus-induced arthritis: clinicopathologic findings in sheep infected by a highly replicative SRLV B2 genotype.

We describe the clinicopathologic features of an arthritis outbreak in sheep induced by small ruminant lentivirus (SRLV), linked to the presence of a new SRLV isolate phylogenetically assigned to caprine arthritis encephalitis virus-like subgroup B2. Thirteen SRLV seropositive Rasa Aragonesa adult ewes were selected from 5 SRLV highly infected flocks (mean seroprevalence, 90.7%) for presenting uni- or bilateral chronic arthritis in the carpal joint. A complete study was performed, including symptomatology, histopathology, immunocytochemistry, immunohistochemistry, in situ hybridization, and microbiology. The carpus was the joint almost exclusively affected, with 10 sheep (76%) showing a moderate increase in carpal joint size (diameter range, 18-20 cm; normal range, 15-16 cm) without signs of locomotion problems and with 3 ewes (23%) showing severe inflammation with marked increase in diameter (21-24 cm), pain at palpation, and abnormal standing position. Grossly, chronic proliferative arthritis was observed in affected joints characterized by an increased thickness of the synovial capsule and synovial membrane proliferation. Microscopically, synovial membrane inflammation and proliferation and hyperplasia of synoviocytes were observed. More positive cases of SLRV infection were detected by immunocytochemistry of articular fluid than of bronchoalveolar lavage fluid. Immunohistochemistry and in situ hybridization also detected positive cells in the subsynovial connective tissue, lung, mediastinal lymph node, mammary gland, and mammary lymph node. All animals were negative for the presence of Mycoplasma or other bacteria in the articular space. The present outbreak likely represents an adaptation of a caprine virus to sheep. Our results underline the importance of the arthritis induced by SRLV in sheep, a clinical form that might be underestimated.

Ovine TRIM5α can restrict visna/maedi virus.

The restrictive properties of tripartite motif-containing 5 alpha (TRIM5α) from small ruminant species have not been explored. Here, we identify highly similar TRIM5α sequences in sheep and goats. Cells transduced with ovine TRIM5α effectively restricted the lentivirus visna/maedi virus DNA synthesis. Proteasome inhibition in cells transduced with ovine TRIM5α restored restricted viral DNA synthesis, suggesting a conserved mechanism of restriction. Identification of TRIM5α active molecular species may open new prophylactic strategies against lentiviral infections.

First report of a primitive neuroectodermal tumor of the bladder in a newborn.

Primitive neuroectodermal tumor (PNET) is part of the Ewing sarcoma family of tumors. The present case reports a primitive neuroectodermal tumor (PNET) of rare location in the bladder in a newborn. It was evaluated with prenatal ultrasound and postnatal tomography that revealed a mass in the posterior wall of the bladder. The patient underwent partial cystectomy with subsequent analysis of the surgical piece removed, the histopathological study indicated a tumor of mesenchymal origin, and immunohistochemical staining confirmed the diagnosis of PNET of the bladder. Satisfactory result and short-term follow-up.

Epithelial-Mesenchymal Transition in a Case of Metastatic Thyroid Carcinoma in a Brown Bear (Ursus arctos).

A 20-year-old male brown bear (Ursus arctos) with a 20 × 25 cm necrotic mass adjacent to the trachea was diagnosed as having an anaplastic thyroid carcinoma. Metastases were observed in the lungs and one adrenal gland and, histologically, these had anaplastic and follicular carcinoma patterns, respectively. E-cadherin labelling was observed in the adrenal mass only, while N-cadherin immunolabelling was detected in the thyroid gland and lung masses. Thyroid-specific markers (thyroid transcription factor-1, thyroglobulin) were expressed in the adrenal gland metastasis. This case illustrates an example of a primary epithelial-mesenchymal transition (EMT) enabling metastasis to distant organ sites, followed by a mesenchymal-epithelial transition within the adrenal gland microenvironment, allowing invasion and reacquisition of thyroid epithelial cell features. EMTs help to understand the phenomenon of carcinoma cell plasticity in enabling colonization and growth of metastases.

From the bluetongue vaccination campaigns in sheep to overimmunization and ovine ASIA syndrome.

The use of vaccines has proven to be very effective in controlling and eradicating infectious diseases, both in veterinary and human medicine; however, vaccines can be also the source of an array of problems caused by procedures such as overimmunization. Bluetongue, an orbiviral disease that affects ruminants, is best controlled by the use of inactivated vaccines. During the last years of the past decade, these vaccines were applied all over Europe to control the spreading of the disease, a goal that was accomplished; however, at the same time, several adverse effects related to the vaccination were reported. Especially in sheep, this vaccination campaign brought out a new cachectic and neurologic disease with harmful consequences for the ovine industry. This disease is now recognized as the ovine version of the autoimmune/inflammatory syndrome induced by adjuvants (ASIA syndrome) and poses an immense challenge in veterinary medicine, immunology, and vaccinology.

Molecular characterization and phylogenetic study of Maedi Visna and Caprine Arthritis Encephalitis viral sequences in sheep and goats from Spain.

Small ruminant lentiviruses (SRLV) are widely spread in many countries, including Spain. However, little is known about the genetic characteristics of Spanish goat and sheep SRLV. In this study, segments from three genomic regions (pol, gag-p25 and LTR) were amplified using DNA isolated from three Spanish autochthonous sheep (one) and goats (two). Animals (one per flock) belonged to distantly located, single-species flocks (goat or sheep). Sequence analysis showed conservation of regions that are putatively relevant to viral survival. Sequences of Spanish goat and sheep SRLV were allocated into phylogenetic trees (phylograms) with known SRLV groups. The phylograms corresponding to the pol, gag-p25 and LTR regions analyzed presented a compatible topology. This showed that Spanish caprine and ovine SRLV sequences belonged to the A or D phylogenetic groups and were closer to sheep SRLV prototypes (A1 group) than to goat SRLV prototypes (B or C groups), according to the current classification [Shah, C., Boni, J., Huder, J.B., Vogt, H.R., Muhlherr, J., Zanoni, R., Miserez, R., Lutz, H., Schupbach, J., 2004a. Phylogenetic analysis and reclassification of caprine and ovine lentiviruses based on 104 new isolates: evidence for regular sheep-to-goat transmission and worldwide propagation through livestock trade. Virology 319 (1), 12-26]. It was not possible to amplify in the three genetic regions the expected fragment in additional Spanish caprine and ovine SRLV proviral DNA sequences with the PCR primers used. This suggests that there is heterogeneity at the primer binding site among Spanish SRLV sequences. It also illustrates the need to develop diagnostic tests that are sensitive in local breeds.

Horizontal Maedi-Visna virus (MVV) infection in adult dairy-sheep raised under varying MVV-infection pressures investigated by ELISA and PCR.

A three year long experimental study was carried out to investigate horizontal MVV-infection by PCR and ELISA, in 191 one year-old latxa dairy-sheep raised in two separate groups under low and high MVV-infection pressure, respectively. Sheep originated from a previous MVV-transmission study in lambs and seroprevalence among one year-old sheep in both groups was 15% approximately. The high infection-pressure group (H-group) consisted of 147 replacement ewes that joined a milk-producing, housed dairy-flock with 42-66% MVV-seroprevalence and the low infection-pressure group (L-group) were castrated males raised in a separate shed. In contrast to results obtained when infection was investigated in lambs, the overall degree of agreement between ELISA and PCR results was very good and there was some indication that it increased further as sheep became older. MVV-prevalence did not change in the L-group and increased to 57% in three year-old sheep in the H-group (p<0.001). Random effects logistic regression confirmed seroconversion was significantly higher in the H-group compared to the L-group and was highest during the year after the sheep were introduced in the dairy flock and did not increase with age as in previous studies using less sensitive antibody assays. The evidence that horizontal transmission can be very low in spite of prolonged close contact between infected and non-infected sheep is valuable for MVV-control purposes. Furthermore it highlights the need to investigate virus excretion dynamics in infected animals and animal to animal transmission to improve our overall understanding of horizontal MVV transmission in MVV endemic populations.

Relative contribution of colostrum from Maedi-Visna virus (MVV) infected ewes to MVV-seroprevalence in lambs.

Maedi-visna virus (MVV) seroprevalence associated with consumption of colostrum from seropositive ewes was investigated in 276 housed lambs from birth to 300 days-old. At birth, lambs were allocated to five experimental groups according to the maternal MVV-serological status, source and mode of feeding colostrum (bovine or ovine and bottle fed or suckled from the dam) and type of horizontal MVV-exposure (raised with the dam or separately with other lambs). The risk of being seropositive at 300 days-old was associated with feeding ovine colostrum from seropositive ewes and increased with intake of bottle-fed ovine colostrum and was higher in lambs separated from their dams and raised with other experimental lambs compared to lambs raised with their dams. Approximately 75-87% of ELISA-positive results in lambs that had ovine colostrum was attributable to colostrum itself. However, approximately only 16% of naturally raised and 29-61% of bottle-fed ovine colostrum lambs were ELISA-positive as a result feeding ovine colostrum. These results confirm that ovine colostrum from seropositive ewes can be a major source of MVV but its overall contribution to seroprevalence in natural conditions is relatively low, and shows that horizontal MVV transmission can be an important source of infection in new-born lambs.

Small ruminant lentivirus infections and diseases.

Small ruminant lentiviruses include viruses with diverse genotypes that frequently cross the species barrier between sheep and goats and that display a great genetic variability. These characteristics stress the need to consider the whole host range and to perform local surveillance of the viruses to opt for optimum diagnostic tests, in order to establish control programmes. In the absence of effective vaccines, a comprehensive knowledge of the epidemiology of these infections is of major importance to limit their spread. This article intends to cover these aspects and to summarise information related to characteristics of the viruses, pathogenesis of the infection and description of the various syndromes produced, as well as the diagnostic tools available, the mechanisms involved in transmission of the pathogens and, finally, the control strategies that have been designed until now, with remarks on the drawbacks and the advantages of each one. We conclude that there are many variables influencing the expected cost and benefits of control programs that must be evaluated, in order to put into practice measures that might lead to control of these infections.

Effect of a new benzodiazepine derivate, clobazam, in anxious patients with gastrointestinal disorders.

Thirty-four anxious patients with gastrointestinal disorders were studied in order to evaluate the effectiveness of a new 1,5-benzodiazepine antianxiety agent (HR 376). The disorders were classified as organic or functional according to the presence or absence of radiologic signs of ulcer. Dietetic measures, gastric antacids, anticholinergic agents, and antianxiety treatment were applied for six weeks. Anxiolytic treatment consisted of 30 mg/day clobazam (HR 376) or 15 mg/day diazepam, given in a randomized, double-blind manner. Clinical follow-up was performed with the PEN Personality Inventory (PEN), Taylor Manifest Anxiety Scale (TMAS), Hamilton Anxiety Scale (HAS), and Wittenborn Psychiatric Rating Scales (WPRS). The score of the psychoticism dimension of the PEN inventory was significantly higher in organic than in functional patients. Significant differences occurred in the reduction of the rating scores of HAS and WPRS before/after treatment in the clobazam and diazepam groups. This would express a modification of state anxiety. The TMAS, which evaluates trait anxiety, disclosed statistically significant improvement in the clobazam group. This group showed an early reduction of the HAS and TMAS scores, which would suggest an early onset of action.

Nontraditional nutrition education interventions: the radio ECCA method.

OBJECTIVE: To evaluate a nutrition education intervention using a radio programme in the Canary Islands. DESIGN: Pre-post quasiexperimental epidemiological study. SETTING: Free living population in the Canary Islands, Spain. SUBJECTS: A sample of 1753 individuals out of 6846 volunteers participating in the educational programme. INTERVENTIONS: A 6-week radio programme consisting of 12 didactic units with supplementary print support material and four optional attendance-based healthy cooking seminars. RESULTS: At 2 months postintervention, an increased consumption of pulses, salads, fruits and juices, cereals and fish, and a decreased consumption of meat, sausages, pastries, French fries, bread and eggs were observed.

Effect of in vitro maedi-visna virus infection on adherence and phagocytosis of staphylococci by ovine cells.

This work was aimed at studying the effect of maedi-visna virus (MVV) infection in vitro on the ability of sheep cells to adhere to staphylococci (Staphylococcus aureus and Staphylococcus epidermidis), and phagocytose these bacteria. Adherence was studied in sheep choroid plexus cells (SCPC) using an ELISA test and phagocytosis was studied in pulmonary alveolar macrophages (PAM) by chemiluminescence. A 5- and 7-day of in vitro MVV infection resulted in syncytium formation and a significant increased adherence (P < 0.01) of SCPC to bacteria. SCPC endogenous fibronectin was significantly higher (P < 0.01) on days 5 and 7 than on day 0 of MVV infection. A significantly decreased phagocytosis (P < 0.05) was also observed on days 5 and 7 of MVV infection in PAM when compared to MVV-free controls. Comparatively, phagocytosis was highest for S. aureus non-slime producing strains, followed by S. epidermidis, and S. aureus slime producing strains, in that order. Finally, increased expression of both, class I and class II major histocompatibility antigens was also observed in MVV-infected PAM on days 5 and 7, whereas SCPC only demonstrated upregulation of MHC class I. These results, indicative of an alteration of some cell functions in MVV-infected cells, may help to understand interactions between MVV-infected cells and bacteria in simultaneous infections and may provide clues to the possible in vivo interactions of both pathogens.

CD8+ lymphocytes in bronchoalveolar lavage and blood: in vivo indicators of lung pathology caused by maedi-visna virus.

A study to determine the putative relationship between lymphocyte phenotypic alterations in bronchoalveolar lavage fluid and stage of lung pathology in maedi-visna infected sheep has been carried out. Twenty-one ewes (16 Texel and five Scottish blackface) naturally infected by maedi-visna virus and three Oxford controls were used. Animals were killed, lungs were removed, bronchoalveolar lavage was performed and pathological studies were completed. Blood samples were also obtained from 16 animals. Lymphocytes in both bronchoalveolar lavage and peripheral blood were labelled with monoclonal antibodies against the main T lymphocyte subsets (CD4, CD8, CD5 and gamma delta TCR) in order to perform flow cytometric studies. Three aspects of pathology were studied: lymphoid interstitial pneumonia, lymphoid follicular hyperplasia and smooth muscle hyperplasia. Percentages of CD4+, CD5+, gamma delta + T cells and the value for the CD4+ / CD8+ ratio in bronchoalveolar lavage of maedi-visna infected animals were significantly decreased (P < 0.05) when compared to controls, while percentages of CD8+ lymphocytes were increased in bronchoalveolar lavage of infected sheep and they were very close to being significant (P = 0.07) when compared to controls. Lesions were evaluated and simple least-squares regression tests demonstrated that there were several significant correlations between various lymphocyte subsets and pathological parameters studied in this work. However, when a multiple regression test was applied to the data, it was observed that only the CD8+ T cell subset both in bronchoalveolar lavage and in blood was significantly correlated with severity of lung pathology. It is concluded that CD8+ lymphocytes are key cells in the development of the interstitial reaction and the lymphocytic alveolitis observed in maedi-visna infected ewes and that the CD8+ alveolitis is a parallel feature to the intensity of lung lesions. It is further suggested that the percentage of CD8+ lymphocytes in bronchoalveolar lavage and in blood may act as in vivo indicators of lung pathology in maedi-visna infected sheep.

A study on lymphocyte activation in maedi-visna virus induced pneumonia.

The stage of activation of bronchoalveolar lavage fluid (BALF) lymphocytes and peripheral blood lymphocytes (PBL) from maedi-visna virus (MVV) infected (n = 7) and control (n = 7) sheep was investigated by assessing four parameters of lymphocyte activation; lymphocyte size and complexity, loss of CD5+ T cells, expression of cell surface interleukin-2 receptor (IL-2R) and expression of DR and DQ MHC Class II molecules. BALF lymphocytes from MVV-infected animals had a significant loss of CD5+ lymphocytes (P < 0.05) and upregulation of DR and DQ MHC Class II molecules compared with controls, consistent with BALF lymphocyte activation. No changes in cell size and complexity or expression of IL-2R were observed. No evidence of PBL activation was detected. These findings suggest an impaired BALF lymphocyte activation during MVV infection.

Quantitation of transforming growth factor-beta in plasma and pulmonary epithelial lining fluid of sheep experimentally infected with maedi-visna virus.

A model of experimental infection with EV1, a lytic British isolate of maedi-visna virus (MVV), was developed. Ten Texel sheep were allocated to two groups and inoculated by the respiratory route with different inocula. Six of the animals received 10(7.2) TCID50 (tissue culture infective dose) of EV1 strain, while four sheep were sham-inoculated with identically prepared virus-free buffer solution. Experimental infection was followed for 8 weeks post-inoculation (PI), with development of precipitating antibodies to MVV developed in the MVV-inoculated animals during the first 4 weeks PI. Transforming growth factor-beta (TGF-beta) levels, in both bronchoalveolar lavage fluid supernatant and plasma samples, were measured. Concentrations of pulmonary epithelial lining fluid (PELF) TGF-beta were calculated. TGF-beta concentrations in PELF were approximately 165-fold higher than in plasma. No significant differences in the concentrations of plasma or PELF TGF-beta, either within or between groups, were observed.

In vitro response of lymphocytes from bronchoalveolar lavage fluid and peripheral blood to mitogen stimulation during natural maedi-visna virus infection.

To investigate the effects of maedi-visna virus (MVV) infection on cell-mediated immunity, the in vitro response of bronchoalveolar lavage fluid (BALF) and peripheral blood (BP) lymphocytes (PBL) to exogenous mitogen was analysed. BALF and PBL from control (n = 9) and MVV-infected (n = 7) animals were cultured fro 3 days in the presence and absence of concanavalin A (Con A). Lymphocyte expression of the interleukin-2 receptor (IL-2R) antigen, a parameter of lymphocyte activation, was quantified by dual-colour flow cytometry using the bovine anti-IL-2R monoclonal antibody IL-A111. IL-2R expression by lymphocytes in BALF and PB from control and MVV-infected animals, with and without Con A stimulation, were compared. In the absence of Con A stimulation, the proportion of cultured BALF CD8+ and gamma delta T cells expressing IL-2R was significantly (P < 0.05) lower for MVV-infected animals than for controls. After Con A stimulation the proportion of BALF CD4+ lymphocytes from MVV-infected animals that expressed IL-2R remained significantly (P < 0.05) lower than for controls. Comparisons within group showed that, after Con A stimulation, the proportion of all the T cell subsets in the control group expressing IL-2R, namely CD4+ (P < 0.001), CD8+ (P < 0.001) and gamma delta T cells (P < 0.05), was significantly increased. In the MVV-infected group, this increase was significant (P < 0.05) for CD4+ and CD8+ T cells, but not for gamma delta T cells. In vitro mitogen stimulation of PB T lymphocytes from both control and MVV-infected animals induced a significant elevation in the proportion of all T cell subsets expressing IL-2R when compared to cultured unstimulated control cells. However, there was considerable heterogeneity in the response to Con A of PB T cells from both groups of animals. The expression of IL-2R followed a different pattern to that of BALF lymphocytes, the proportion of unstimulated gamma delta / IL-2R+ T cells from MVV-infected animals being significantly (P < 0.05) higher than that of controls, and the proportion of cultured unstimulated CD8+ / IL-2R+ T cells from MVV-infected animals being significantly (P < 0.05) lower than that from controls. From these studies it can be concluded that the BALF T lymphocyte immune dysfunction observed during natural MVV infection, characterized by impaired IL-2R expression, is maintained under in vitro conditions.

Early pulmonary cell response during experimental maedi-visna virus infection.

A model of experimental infection with EV1, a British isolate of maedi-visna virus (MVV), has been developed. Twelve male Texel sheep were allocated to three groups and inoculated by the respiratory route with different inocula. Six of the animals received 10(7.2) tissue culture infective dose (TCID50) of MVV EV1 strain. Two sheep were inoculated with the same dose of heat inactivated MVV EV1 strain. An additional group of four sheep was sham-inoculated with identically prepared virus-free culture media. Experimental infection was followed for 16 weeks. Prior to inoculation, routine haematology, bronchoalveolar lavage (BAL) and flow cytometric analysis of bronchoalveolar lavage fluid (BALF) lymphocytes were performed in all animals to provide baseline parameters. Flow cytometric analysis of BALF lymphocytes and differential BALF cell counts were performed. Precipitating antibodies to MVV developed in all MVV-inoculated animals during the first 4 weeks post-inoculation, while the rest remained seronegative to MVV. MVV-infected animals had significantly decreased (P < 0.05) percentages of macrophages and significantly increased (P < 0.05) percentages of lymphocytes in BALF 4 weeks post-inoculation. Phenotypic changes in BALF T lymphocytes from MVV-inoculated animals, compared with the other two groups, showed significantly decreased (P < 0.05) percentages of CD4+ and gamma delta + T lymphocytes, significantly increased (P < 0.05) percentages of CD8+ lymphocytes and significant inversion (P < 0.05) of the CD4+/CD8+ ratio at different sampling times, but between 2 and 12 weeks post-inoculation. These findings indicate that during experimental MVV-infection an early, short-term cellular reaction occurs in the lung, that is characterised by T lymphocyte phenotypic changes that are very similar, if not identical, to those observed in natural MVV infection.

Early detection of maedi-visna (ovine progressive pneumonia) virus seroconversion in field sheep samples.

The aim of this work was to investigate whether an enzyme-linked immunosorbent assay (ELISA) was useful for early detection of maedi-visna virus (MVV) infection in sheep under field conditions. An ELISA based on p25 recombinant protein and a gp46 synthetic peptide was used. Sequentially obtained serum samples (n = 1,941) were studied for 4 years. ELISA results were compared with those of the agar gel immunodiffusion (AGID) test, and results of both tests were compared with a reference result established using consensus scores for at least 2 of 3 serologic techniques (AGID, ELISA, and western blotting, which was used to resolve result discrepancies between the other 2 techniques). A total of 247 discrepancies were observed between ELISA and AGID. Of these, 131 were due to an earlier detection of 120 sera by the ELISA and 11 sera by AGID. The remaining discrepancies (116) were due to the presence of false reactions in both tests. Fewer false-negative results were found by ELISA than with AGID (6 vs. 69 sera, respectively), whereas the number of false-positive results was virtually the same for ELISA and AGID (21 vs. 20, respectively). In relation to the reference result, ELISA sensitivity and specificity were 97.8% and 98.2%, respectively, whereas values for AGID were 76.3% and 98.3%, respectively. The agreement between ELISA and the reference result was higher than that between AGID and the reference result (K value: 0.96 and 0.77, respectively). A variation in the ELISA signal (based on optical density) was observed during the study period, suggesting different antibody levels throughout the animal's life. The ELISA was useful for detecting MVV-infected sheep in field conditions and has potential for use in control and eradication programs.

Fetal anasarca (Hydrops foetalis) associated with lymphoid tissue agenesis possibly due to an autosomal recessive gene defect in sheep.

Fourteen hydrops fetalis cases appeared in a sheep flock in the Soria province of Central Spain in two lambing seasons in 2000. There were no previous cases of hydrops fetalis in this flock. Normal delivery could not be completed because fetal weights ranged from 12 to 16 kg and fetuses had massive subcutaneous edema. Five affected pregnant females were studied. The complete lack of lymph nodes in the fetuses was the most outstanding finding, this anomaly likely being the origin of generalized fluid accumulation. Karyotypes were normal. A blind protocol of parentage testing was performed by means of DNA microsatellite analysis, and one of the five existing rams was found to be the only compatible sire of the affected fetuses. This male had been selected from the same flock while the other rams had all been acquired from other farms. The first cases appeared when this ram began breeding, and no cases were observed after replacing it. Male and female fetuses were affected in similar proportions. The existence of a recessive allele affecting normal lymph node embryonic development in this flock is proposed as the most appropriate hypothesis. As a consequence, the use of rams from different farms is indicated as an efficient emergency measure in similar situations, while the affected flock should be excluded from selection programs as long as the anomalous gene remains unidentified.