Generalized severe junctional epidermolysis bullosa with congenital absence of skin in churra lambs.

BACKGROUND: Up to 0.5% of churra lambs from two genetically related flocks showed congenital skin lesions of variable severity, jeopardizing the life of the lambs in the most severe cases. HYPOTHESIS/OBJECTIVES: The primary objective of this study was to classify the type of congenital epithelial disease suffered by these animals, based on the description of the macroscopic skin defects, the histological and ultrastructural changes and the hereditary nature of the condition. ANIMALS: Thirty affected newborn lambs from two genetically related flocks were studied. Three additional lambs acquired from two other flocks, which had no grossly apparent skin lesions and had died of infectious diseases, were studied as unaffected control animals. METHODS: Histological and ultrastructural examinations of skin and oral mucosa samples were performed. Pedigree analyses were used to investigate genealogical relationships. RESULTS: Generalized severe junctional epidermolysis bullosa with congenital absence of skin was described in all lambs studied and an autosomal recessive mode of inheritance was identified. CONCLUSIONS AND CLINICAL IMPORTANCE: The pathological findings and mode of inheritance in these lambs are similar to an inherited epidermolysis bullosa subtype of humans, which has not been reported previously in veterinary medicine.

Experimental infection of lambs with C and S-type strains of Mycobacterium avium subspecies paratuberculosis: immunological and pathological findings.

The two main genotypes of recognized isolates of Mycobacterium avium subsp. paratuberculosis (Map) are cattle (C) and sheep (S) strains. An experimental infection was conducted to establish the effect of Map strain on the pathogenesis of ovine paratuberculosis. Twenty-four out of thirty 1.5-month-old Assaf lambs were divided into 4 groups of 6 and infected orally with three low passage field isolates, two of S- (22G and the pigmented Ovicap49) and one of C- (764) type, and the reference K-10 strain (C type). The remaining six animals were unchallenged controls. Animals were euthanized at 150 and 390 days post-infection (dpi). Throughout the experiment, the peripheral immune response was assessed and histological and molecular (PCR) studies were conducted on samples of intestine and related lymphoid tissue. Specific antibody and IFN-γ production was significantly higher in animals infected with the C strains, while no consistent IFN- γ responses were observed in the S-type strain infected groups. A positive intradermal skin test response was detected in all infected groups. Lambs infected with S-type strains had granulomatous lesions restricted to the lymphoid tissue with no differences in the lesion intensity over time. In both C-type strain groups, lesions were more severe at 150 dpi while at 390 dpi lesions, characterized by well-demarcated granulomas with fibrosis, decreased in severity. Only infected lambs were positive to PCR. These results suggest that the strain of Map has a strong influence over the immune and pathological responses developed by the host. Lesions induced by C-type strains in lambs show a regressive character and tend to decrease as the infection progresses.

Hereditary lissencephaly and cerebellar hypoplasia in Churra lambs.

BACKGROUND: Lissencephaly is a rare developmental brain disorder in veterinary and human medicine associated with defects in neuronal migration leading to a characteristic marked reduction or absence of the convolutional pattern of the cerebral hemispheres. In many human cases the disease has a genetic basis. In sheep, brain malformations, mainly cerebellar hypoplasia and forms of hydrocephalus, are frequently due to in utero viral infections. Although breed-related malformations of the brain have been described in sheep, breed-related lissencephaly has not been previously recorded in a peer reviewed publication. RESULTS: Here we report neuropathological findings in 42 newborn lambs from a pure Churra breed flock, with clinical signs of weakness, inability to walk, difficulty in sucking and muscular rigidity observed immediately after birth. All the lambs showed near-total agyria with only a rudimentary formation of few sulci and gyri, and a severe cerebellar hypoplasia. On coronal section, the cerebral grey matter was markedly thicker than that of age-matched unaffected lambs and the ventricular system was moderately dilated. Histologically, the normal layers of the cerebral cortex were disorganized and, using an immunohistochemical technique against neurofilaments, three layers were identified instead of the six present in normal brains. The hippocampus was also markedly disorganised and the number and size of lobules were reduced in the cerebellum. Heterotopic neurons were present in different areas of the white matter. The remainder of the brain structures appeared normal. The pathological features reported are consistent with the type LCH-b (lissencephaly with cerebellar hypoplasia group b) defined in human medicine. No involvement of pestivirus or bluetongue virus was detected by immunohistochemistry. An analysis of pedigree data was consistent with a monogenic autosomal recessive pattern inheritance. CONCLUSIONS: The study describes the clinical and pathological findings of lissencephaly with cerebellar hypoplasia in Churra lambs for which an autosomal recessive inheritance was the most likely cause. Histopathological features observed in the cerebral cortex and hippocampus are consistent with a possible failure in neuronal migration during brain development. This report suggests that lissencephaly should be considered in the differential diagnosis of congenital neurological disease in newborn lambs showing weakness, inability to walk and difficulty sucking.

Nephrotoxicosis in Iberian piglets subsequent to exposure to melamine and derivatives in Spain between 2003 and 2006.

Between November 2003 and September 2006, 300 to 400 45-60-day-old Iberian piglets developed anorexia, polydipsia, and lethargy. Piglets were from 5 different farms in the western part of Spain. Morbidity was between 40% and 60%, and mortality ranged from 20% to 40% of the total population of postweaning piglets. In the 9 piglets in which postmortem examinations were conducted, kidneys were enlarged with yellow foci in the cortex and medulla. Microscopically, these foci were accumulations of crystals within the lumina of dilated distal tubules and collecting ducts, causing flattening of the renal tubular epithelial cells. The crystals displayed a multicolored birefringence under cross-polarized light. The multinucleated giant cells surrounding the crystals, interstitial fibrosis, and nonsuppurative infiltrates indicated a chronic inflammatory response. Toxicologic analysis of fixed kidney tissues from 4 piglets demonstrated the presence of melamine, ammeline, ammelide, and cyanuric acid. Ammelide concentrations were highest, ranging from 39,000 to 92,000 mg/kg, followed by ammeline (20,000-34,000 mg/kg), melamine (9,200-29,000 mg/kg), and cyanuric acid (2,200-9,100 mg/kg). The clinical, histologic, and toxicologic findings in affected piglets were similar to those reported in dogs and cats that died of melamine and melamine analogue-associated renal failure in 2004 and 2007. To the authors' knowledge, this is the first documented report of poisoning due to melamine and its analogues in pigs and demonstrates that contamination of pig feed occurred as early as 2003.

Ruminal Leiomyosarcoma in an adult cow.

An ulcerated and pedunculated intraluminal yellowish solitary mass was observed protruding into the ruminal lumen of an adult cow during an abattoir survey. Histologically, the neoplasm invaded the lamina propria-submucosa, eroded the ruminal epithelium and segmentally effaced the inner tunica muscularis. It was composed of pleomorphic spindle cells arranged in fascicles. Areas of hemorrhage, necrosis, microcystic changes as well as marked anisokaryosis, the presence of giant cells and scattered mitosis with atypical figures, were also observed. Immunohistochemically this tumor labeled positive for alpha smooth muscle actin, desmin and vimentin. With all the above findings, a diagnosis of ruminal leiomyosarcoma was confirmed. To the authors' knowledge, this is the first report of ruminal leiomyosarcoma in cattle.

Virulence attenuation of a Mycobacterium avium subspecies paratuberculosis S-type strain prepared from intestinal mucosa after bacterial culture. Evaluation in an experimental ovine model.

The differences in pathogenicity between an inoculum derived directly from an intestinal tissue homogenate from a paratuberculosis affected sheep and the S-type Mycobacterium avium subsp. partuberculosis (Map) strain isolated in laboratory media from the mentioned homogenate were assessed in two experiments in lambs. Specific peripheral immune responses were significantly lower in animals inoculated with the cultured organisms that showed only granulomatous lesions in the intestinal lymphoid tissue. However, in the homogenate group, more abundant granulomata also occurred in the lamina propria. Map was isolated only in lambs infected with the culture strain. Map DNA was demonstrated by nested-PCR in all the lambs but in a lower proportion (57.1% vs 100%) in those from the culture group. Under these particular experimental conditions, the results suggest that an attenuation of Map virulence has occurred in the cultured strain compared to the initial tissue homogenate, even after a low number of passages.

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.

Impact of maedi-visna in intensively managed dairy sheep.

Maedi-visna (MV) is a slow lentiviral disease of sheep that has a significant economic impact in many sheep-producing regions although there remains a paucity of data relating to actual production losses resulting from this disease. The objective of this study was to evaluate direct losses, through death or culling, from two dairy sheep flocks with high seroprevalences of infection over a 2 year period. Maedi-visna was found, either alone or in combination with other diseases, to be the most common disease diagnosed in these sheep, and the major cause of direct animal losses in the two flocks. Moderate to severe lesions associated with MV were found in 52% and 80% of the sheep, respectively, affecting the lungs, brain and/or mammary glands. Despite the similarity of the two flocks under study in terms of breed, number of animals, geographical proximity, and inter-change of rams, a striking difference was observed regarding the clinical presentation of the disease: in one flock the respiratory form was dominant while in the other 70% of animals died or were culled because of neurological signs.

Differences in the peripheral immune response between lambs and adult ewes experimentally infected with Mycobacterium avium subspecies paratuberculosis.

The peripheral immune response, and its relationship with the outcome of the infection according to the age of the animal, has been investigated in young lambs and adult ewes experimentally infected with two different doses of Mycobacterium avium subspecies paratuberculosis (Map). Sixteen 1.5-month-old lambs out of 24 and 23 adult ewes out of 30 were orally challenged with an ovine Map field isolate. Animals were divided into two groups: HD, infected with a higher dose of Map and LD, with a lower dose. The remaining animals were used as uninfected control groups. Animals were euthanized at 110-120 and 210-220 days post-infection (dpi). Along the experiment, the humoral response and the specific and non-specific IFN-γ production were assessed. An intradermal skin test (IDT), using avian PPD, was also performed at 90 and 195 dpi. Samples of intestine and related lymphoid tissue were taken for histological, bacteriological and PCR studies. The Ab and IFN-γ production as well as the IDT response appeared earlier and with more intensity in the adult ewes compared to the lambs. The basal non-specific IFN-γ levels increased only in the adult ewes from the HD group. Animals from the LD and HD groups were positive to PCR; however, lesions consistent with paratuberculosis were exclusively observed in the HD group, both in lambs and in adult sheep, but they only progressed to more advanced stages in the former. These results suggest that the peripheral immune response induced by Map infection in the adult ewes is more efficient to control the progression of the infection than in lambs. This could likely be due to the existence of previous contacts with Map or other mycobacteria in the adult sheep compared to the young lambs.