M.C. Ferreras

Diagnosis of the nervous form of maedi-visna infection with a high frequency in sheep in Castilla y León, Spain

Between 1997 and March 2004, the nervous form, or visna, of maedi-visna infection was diagnosed in 71 of 1631 sheep (4·35 per cent) examined in the Castilla y León region of Spain, of which 634 had shown nervous signs. The presence of the virus was confirmed by immunohistochemistry and in some cases by PCR on frozen-thawed or paraffin-embedded tissue samples. The main clinical signs were hindleg ataxia and paresis, but blindness or nystagmus were also observed. Thirty-three of the affected sheep (46·5 per cent) were two years old or younger. The affected sheep showed variable degrees of a non-suppurative meningoencephalitis, and immunohistochemistry identified positive cells in all cases, with no relation to the intensity of the inflammatory lesion.

Maedi-Visna: the Meningoencephalitis in Naturally Occurring Cases

Lesions were examined at different levels of the central nervous system (CNS) in 64 sheep with natural maedi-visna (MV) meningoencephalitis. All animals showed lesions in more than one of the CNS locations examined; the lesions in the cranial regions were periventricular, while those in the spinal cord affected the white matter funicles. Lesions were found particularly in the cerebellar peduncles (non-suppurative meningoencephalitis), followed by the corpus callosum, hippocampus and thoracic spinal cord. Vascular, infiltrative and malacic histopathological patterns were recognized. One pattern predominated in each section examined, although mixed forms occurred. Vascular lesions occurred with similar frequency at all CNS levels, but infiltrative and malacic lesions predominated at rostral and caudal levels, respectively. Cells consistent with macrophages and shown immunohistochemically to be associated with MV virus were seen in malacic and infiltrative lesions, at the periphery of damaged areas.

Comparison of Three Immunological Diagnostic Tests for the Detection of Avian Tuberculosis in Naturally Infected Red Deer (Cervus Elaphus)

Cases of tuberculosis due to Mycobacterium avium subsp. avium in 52 adult red deer (Cervus elaphus) from a farm were studied using different diagnostic techniques. Immunological probes consisted of the comparative cervical tuberculin (CCT) skin test, the interferon-γ (IFN-γ) assay, and 2 enzyme-linked immunosorbent assays (ELISAs) employing either avian purified protein derivatives or protoplasmatic antigen (PPA-3) as antigens. Three of the animals were euthanized due to severe weakness, loss of weight, and emaciation. Macroscopically, the 3 animals showed tuberculous lesions located mainly in lymph nodes of the digestive system and small intestine but also in other organs and lymph nodes. Polymerase chain reaction was carried out on samples from the 3 deer using primers to detect IS901, IS900, and IS6110, specific for Mycobacterium avium subsp. avium, Mycobacterium avium subsp. paratuberculosis, and Mycobacterium tuberculosis complex, including Mycobacterium bovis, respectively. The last 2 agents cause pathologies very similar to avian tuberculosis in deer. The 3 deer were strongly positive by both ELISAs, slightly positive by the IFN-γ test, and 1 of 2 was positive by the CCT test. As with domestic ruminants, ELISA could detect deer in an advanced stage of infection, with large numbers of mycobacteria.

Aleutian Disease Serology, Protein Electrophoresis, and Pathology of the European Mink (Mustela lutreola) from Navarra, Spain

Abstract The European mink, Mustela lutreola, has suffered a dramatic decline in Europe during the 20th century and is one of the most endangered carnivores in the world. The subpopulation of European mink from Navarra, Spain, estimated to number approximately 420, represents approximately two thirds of the total number of mink in Spain. Aleutian Disease Virus (ADV) is a parvovirus with a high degree of variability that can infect a broad range of mustelid hosts. The pathogenesis of this virus in small carnivores is variable and can be influenced by both host factors (e.g., species, American mink genotype, and immune status) and viral strain. A cross-sectional study was conducted during the pre-reproductive period of February–March 2004 and 2005 and the postreproductive period of September–December 2004. Mink were intensively trapped along seven rivers that were representative of the European mink habitat in Navarra. Antibody counter immunoelectrophoresis against ADV was performed on 84 European mink blood samples. All the samples were negative. Protein electrophoresis was performed on 93 plasma samples. Nine of those samples (9.6%) had gamma globulin levels exceeding 20% of the total plasma protein. Complete necropsies were performed on 23 cadavers of European mink collected in the area between 2000 and 2005. Seventeen of the mink (74%) had traumatic and hemorrhagic lesions compatible with vehicular impact injuries. Although there were no histopathologic lesions associated with ADV, this study documents the first description of a naturally occurring canine distemper virus infection in a European mink. In addition, pulmonary adiaspiromycosis in three European mink from Spain was reported.

Ovine Toxoplasmosis: A New Look at its Pathogenesis

Conditions causing reproductive failure are a significant concern in the livestock industry, and amongst these, ovine toxoplasmosis is one of the most important. Despite decades of research, there remain gaps in knowledge about this disease, especially regarding the pathogenesis of abortion in sheep. As for other diseases causing ovine abortion, such as chlamydial abortion or border disease, the consequences of infection with Toxoplasma gondii depend largely on the stage of gestation, but the mechanisms involved are not well understood. Immunological modulation occurring during gestation has been proposed as the main mechanism accounting for this clinical variation. However, the extent and effect of such modulation has not yet been identified clearly in sheep and the involvement of other unknown factors has been proposed. Recent experimental studies have defined an unacknowledged clinical presentation of ovine toxoplasmosis, where abortions occur during the acute phase of infection, resulting in as high as 100% fetal loss in susceptible sheep. The pathogenesis of this clinical form differs from that of classically described ovine toxoplasmosis, and its pathological features resemble those of the perinatal syndrome known as cerebral palsy in man. A range of variables, including individual susceptibility, isolate virulence and infective dose, have been proposed as key factors in the development of one or the other of these clinical forms and warrants further investigation in this important disease.