Phylogenetic analysis of classical swine fever virus (CSFV) field isolates from outbreaks in South and Central America.

To date, there is little information concerning the epidemiological situation of classical swine fever (CSF) in the Americas. Besides summarizing the available data, genotyping of isolates from outbreaks in domestic pigs in several countries of South and Central America was performed. For this, a 190 base fragment of the E2 envelope glycoprotein gene was used. European strains and isolates, and historical isolates from the United States (US) were included for comparison. In contrast to the situation in most parts of Europe, where group 2 isolates predominate, it was found that all the isolates from the American continent analyzed belonged to group 1 and were further resolved into three subgroups. The Cuban isolates clustered in subgroup 1.2, whereas the isolates from Honduras and Guatemala clustered in subgroup 1.3. The remaining isolates from Argentina, Brazil, Colombia and Mexico generated four poorly resolved clusters in subgroup 1.1, together with the vaccine strains, with historical European and US isolates, and with a recent Russian isolate. While the vaccine strains and the historical European isolates formed a relatively distinct cluster, one of the US isolates clustered together with the Mexican, and another one with Colombian isolates. Historically, CSF (hog cholera) was observed almost simultaneously in the US and in Europe in the first half of the 19th century, and its origin remains a matter of discussion. Our results showed that the US isolates are closely related to isolates from South America, while appearance of isolates in Cuba on one hand and in Honduras and Guatemala on the other hand, seems to have been due to unrelated events. This allows to speculate that at least in the American continent, CSF virus may have appeared independently in several regions, and spreading may have been a secondary effect.

Testing meningeal strains of Streptococcus suis to detect M protein genes.

Previous reports have suggested that the surface proteins found in meningeal strains of Streptococcus suis might be similar to the M protein of group A streptococci. Fifty-five strains of S suis, including human and swine meningeal and pneumonic isolates, were tested for M protein genes by DNA probes representing the constant domain of the 3' end of the group A, M protein gene. None of the S suis strains examined was positive, indicating that these organisms either lack M protein genes or harbour different genes, not expressing the constant domains of protein M from group A.

Identification of epidemic strains of Streptococcus suis by genomic fingerprinting.

A natural outbreak of Streptococcus suis meningitis in two closed swine herds was studied. DNA fingerprinting, serotyping, and biochemical profiles were assessed. Multiple serotypes were recovered from these herds. In farm A, 50 S. suis strains were isolated from 330 swabs collected. Eighteen strains belonged to serotype 2, and 32 strains belonged to serotypes 3, 5, 6, 8, 9, and 11. In farm B, 16 S. suis strains were recovered from a total of 70 samples. Eight strains belonged to serotype 7 and eight belonged to serotypes 2, 3, 5, and 8. In each epidemiological situation, a single strain characterized by a distinctive restriction fragment pattern predominated among affected penmates. The epidemic serotype 2 strain was detected in farm A in weaned pigs between the ages of 5 and 7 weeks. In contrast, the pathogenic strain in farm B belonged to serotype 7 and was isolated from pigs up to 3 weeks of age. The results from both farms strongly suggest a lateral spread of these organisms. No vertical transmission could be shown in either herd. It was concluded that genomic fingerprinting is an appropriate method to distinguish outbreak isolates of S. suis from nonoutbreak strains, within the same serotype or from epidemiologically unrelated clusters of strains.

Characterization of prototype and clinically defined strains of Streptococcus suis by genomic fingerprinting.

A collection of Streptococcus suis strains from animal and human infections was examined for DNA-banding patterns after restriction endonuclease digestion and agarose gel electrophoresis. The endonuclease HaeIII produced the most discriminating restriction profiles among 23 serotypes studied. DNA from serotypes 9, 11, 12, and 16 was resistant to HaeIII cleavage. DNA from serotypes 9 through 16 was cleaved with HindIII and showed substantial genomic differences. We also examined 106 epidemiologically unrelated strains isolated from cases of pig meningitis or pneumonia and 5 strains isolated from cases of human meningitis in order to compare genomic fingerprinting and serotyping as epidemiological tools. Heterogeneity was found among fingerprints of serologically identical isolates, indicating genetic diversity within some serotypes. DNA fingerprints of some serotype 2 strains from different sources appeared identical, suggesting a clonal relationship among strains of this serotype. The data suggest that this technique represents an important tool for examining the natural history of disease caused by S. suis.

Serological study of ovine toxoplasmosis in Colombia: epidemiological study of a field outbreak.

A serological study, using the indirect haemagglutination test, of an outbreak of toxoplasmosis in a flock of blackface sheep is described. The serological aspects of the disease are discussed with reference to this incident, and possible sources of infection are suggested.

Serological study of ovine toxoplasmosis in Colombia: prevalence of haemagglutinating antibodies to toxoplasma in sheep.

A total of 1655 ovine sera from the six principal sheep rearing areas of Colombia were examined for toxoplasma antibodies using the indirect haemagglutination test. It was shown that 58 per cent of these samples had titres of 1/16 or greater. Seropositive animals were distributed throughout all the areas studied. The possible factors affecting the distribution of seropositive sheep in one of the areas are discussed.