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The cyst-forming protozoan parasite Neospora caninum is one of the main causes of bovine abortion worldwide and is of great economic importance in the cattle industry. Recent studies have revealed extensive genetic variation among N . caninum isolates based on microsatellite sequences (MSs). MSs may be suitable molecular markers for inferring the diversity of parasite populations, molecular epidemiology and the basis for phenotypic variations in N . caninum , which have been poorly defined. In this study, we evaluated nine MS markers using a panel of 11 N . caninum -derived reference isolates from around the world and 96 N . caninum bovine clinical samples and one ovine clinical sample collected from four countries on two continents, including Spain, Argentina, Germany and Scotland, over a 10-year period. These markers were used as molecular tools to investigate the genetic diversity, geographic distribution and population structure of N . caninum . Multilocus microsatellite genotyping based on 7 loci demonstrated high levels of genetic diversity in the samples from all of the different countries, with 96 microsatellite multilocus genotypes (MLGs) identified from 108 N . caninum samples. Geographic sub-structuring was present in the country populations according to pairwise F ST. Principal component analysis (PCA) and Neighbor Joining tree topologies also suggested MLG segregation partially associated with geographical origin. An analysis of the MLG relationships, using eBURST, confirmed that the close genetic relationship observed between the Spanish and Argentinean populations may be the result of parasite migration (i.e., the introduction of novel MLGs from Spain to South America) due to cattle movement. The eBURST relationships also revealed genetically different clusters associated with the abortion. The presence of linkage disequilibrium, the co-existence of specific MLGs to individual farms and eBURST MLG relationships suggest a predominant clonal propagation for Spanish N . caninum MLGs in cattle.

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Necropsies were performed on 354 fetuses from dairy and beef herds submitted from 1994 to 2000 to the diagnostic laboratories at Instituto Nacional de Tecnología Agropecuaria, Balcarce, Argentina. Samples from the fetuses were examined for pathogenic organisms and processed for microscopic examination. An aetiological diagnosis was made for 161 (45.5%) of the fetuses. No diagnosis was made for 193 (54.5%) fetuses. Infectious agents were isolated from 122 (34.4%) of the fetuses, bacterial agents being involved in 80 (22.6%) of these. The most common bacterial agents isolated from the fetuses were Brucella abortus in 28 fetuses, Campylobacter fetus in 26 cases, and Escherichia coli in 9 cases. Bovine herpesvirus and bovine viral diarrhoea virus were found in 9 and 6 cases, respectively. Neospora caninum was detected by an immunohistochemical technique in 26 cases (7.3%). Congenital abnormalities, dystocia and mummifications were found in 8, 19 and 11 cases, respectively.

In the present work, evidence of Listeria monocytogenes antigens based on the avidin-biotin complex (ABC) immunoperoxidase technique was performed on formalin-fixed central nervous system tissues (CNS) from a total of 23 natural cases of encephalitis (four ovine and 19 bovine). Listeria monocytogenes serotype 4 was isolated from 10 of 17 cultured specimens. Meningoencephalitis characterized by focal necrosis, microabscesses, perivascular cuffing, and gliosis with presence of macrophages and/or neutrophils was observed at histological examination. Positive L. monocytogenes antigens were successfully identified by immunohistochemistry (IHC) in the CNS of all 23 cases. Paraffin-embedded tissues assayed were stored up for 17 years. Morbidity of the outbreaks was between 0.3-3% and 0.1-1% for ovine and bovine cases, respectively. In all the ovine cases, flocks involved were under extensive grazing conditions. In nine of the 19 bovine cases (47.3%), supplementation with corn silage was used. The ABC test can help as a practical tool for the diagnosis of natural cases of L. monocytogenes encephalitis on formalin-fixed specimens from ovine and bovine.