Neospora caninum DNA distribution in tissues of gerbils as experimental models of chronic neosporosis

ABSTRACT Neospora caninum is the main etiologic agent of neosporosis in domestic animals and its pathogenesis comprises two characteristic phases: acute and chronic. Rodents are used as experimental models to mimic acute and chronic bovine neosporosis. In this study, we inoculated a total of 27 female gerbils, with different doses of N. caninum tachyzoites aiming to induce chronic disease. DNA was extracted from different organs of each animal after spontaneous death or euthanasia. Encephalic tissues were submitted to a highly sensitive real time PCR aiming to detect chronically infected animals. All the other samples were submitted to standard PCR. A total of 11 gerbils died due to acute neosporosis, as confirmed by N. caninum DNA detection in organs. 5x103 tachyzoites/mL of N. caninum was the dosage of antigen that can induce chronic infection in gerbils. In the encephalon sections of some animals that showed clinical signs of persistent infection, we found 70% positive for the anterior encephalon section, suggesting this area as preferential for cyst formation. Therefore, we determined the doses of tachyzoites that cause acute or chronic infection and detection of positive tissues, preferably, systemic organs during acute and encephalon in chronic phases.

Chimeric Protein Designed by Genome-Scale Immunoinformatics Enhances Serodiagnosis of Bovine Neosporosis

ABSTRACT Neosporosis has become a concern since it is associated with abortion in cattle. Currently, in situ diagnosis is determined through anamnesis, evaluation of the history, and perception of the clinical signs of the herd. There is no practical and noninvasive test adapted to a large number of samples, which represents a gap for the use of new approaches that provide information about infections and the risks of herds. Here, we performed a search in the Neospora caninum genome by linear B-cell epitopes using immunoinformatic tools aiming to develop a chimeric protein with high potential to bind specifically to antibodies from infected cattle samples. An enzyme-linked immunosorbent assay with the new chimeric antigen was developed and tested with sera from natural field N. caninum-infected bovines. The cross-reactivity of the new antigen was also evaluated using sera from bovines infected by other abortive pathogens, including Trypanosoma vivax, Leptospira sp., Mycobacterium bovis, and Brucella abortus, and enzootic bovine leucosis caused by bovine leukemia virus, as well as with samples of animals infected with Toxoplasma gondii. The assay using the chimeric protein showed 96.6% ± 3.4% of sensitivity in comparison to healthy animal sera. Meanwhile, in relation to false-positive results provided by cross-reactivity with others pathogens, the specificity value was 97.0% ± 2.9%. In conclusion, immunoinformatic tools provide an efficient platform to build an accurate protein to diagnose bovine neosporosis based on serum samples.

Histopathological findings and immunohistochemical staining of Neospora caninum infection in placentas of animals for slaughter

Bovine neosporosis is a parasitic disease caused by the protozoan Neospora caninum, which is one of the main pathogens that cause abortions in cattle worldwide. It is responsible for large losses in dairy and beef cattle, especially with regard to the expenses associated with decreased productivity and increased discard. In the State of Maranhão, the occurrence of this parasite has already been confirmed in the dairy cattle of three microregions that make up the state’s dairy industry and in small ruminants of the municipalities of Amarante do Maranhão and Buritirana. This fact justifies the importance of determining the presence of N. caninum in cattle slaughtered in the slaughterhouses of the Island of São Luís, to help control the parasitic cycle in the cattle production system of the region under study, and the importance of its diagnosis. The objective of the research was to conduct a histopathological and immunohistochemical characterization of bovine placentas infected with N. caninum collected in slaughterhouses. Sixteen placenta samples from cows were randomly selected at the slaughterhouses of the city of São Luís for histological analysis and immunohistochemistry. Results showed that 31% of the placentas presented histopathological changes such as: inflammatory process, edema, hemorrhage and presence of hemosiderin. All slides with histopathological changes showed immunolabeling for N. caninum.