Breed variability in the cellular mediated immune response to experimental Neospora caninum infection in heifers.

Protozoan parasite Neospora caninum causes abortion in infected cattle while others remain asymptomatic. Host immunity plays a critical role in the outcome of bovine neosporosis. Despite extensive research, there is a critical gap in therapeutic and preventive measures, and no effective vaccines are available. Both beef and dairy cattle can suffer from N. caninum-induced abortions, but cumulative evidence suggests a breed susceptibility being higher in dairy compared with beef breeds. It has been established that the response to N. caninum infection primarily involves a cell-mediated immune response (CMIR) regulated by T-helper type 1 (Th1) cells and specific cytokines. The delayed-type hypersensitivity (DTH) skin test has been used to measure the ability of livestock to generate CMIR, in the context of breeding for disease resistance and as a method for diagnosis of several diseases. In this study, we evaluated the immune response triggered by an N. caninum-induced DTH skin test between Holstein - a dairy breed intensively selected- and Argentinean Creole heifers - a beef breed with minimal genetic selection- to assess differences in CMIR following experimental N. caninum infection. The immune response, measured through skinfold thickness and histological and immune molecular analysis, revealed variations between the breeds. Our study found an increased CMIR in Argentinean Creole heifers compared to Holstein heifers. Differential gene expression of key cytokines was observed at the DTH skin test site. Argentinean Creole heifers exhibited elevated IFN-γ, IL-12, IL-10, and IL-4, while Holstein heifers only showed higher expression of IL-17. This finding could underscore genetic diversity in response to neosporosis, which could be used in breeding cattle strategies for disease resistance in cattle populations.

Use and comparison of serologic assays to detect anti-Neospora caninum antibodies in farmed red deer (Cervus elaphus).

Neospora caninum is a protozoan parasite that cause abortion in different ruminant species, including red deer ( Cervus elaphus). There are no validated assays to be performed with sera from red deer. At the present work, we evaluated the agreement among indirect fluorescent antibody test (IFAT), competitive inhibition ELISA based on a recombinant protein (ciELISA tSAG1) and immunoblot (IB) to detect anti- N. caninum antibodies in a red deer herd that presented reproductive losses due to N. caninum. In addition, we analyzed the relationship between the serologic results and 15 hinds were analyzed by IFAT, ciELISA tSAG1 and IB to detect anti- N. caninum antibodies. In the three assays, the cut-off established for cattle was used. Besides, sera were analyzed by IFAT to detect anti- Toxoplasma gondii antibodies. The hinds were monitored by ultrasound scanning during the gestational period to detect abortions. Gwet's agreement coefficient (AC1) and the percentage of agreement were used to estimate the agreement between pairs of assays. Chi-square test and odds ratio (OR) were used for the statistical association between abortion and seropositivity to N. caninum or to T. gondii. The N. caninum seropositivity rate was 53.9% (62/115), 57.4% (66/115) and 55.7% (64/115) for IFAT, ciELISA tSAG1 and IB, respectively. The AC1 and percentage of agreement were 0.760% and 87.8% for the pair ciELISA tSAG1 /IFAT, 0.793% and 89.6% for the pair IFAT/IB, and 0.966% and 98.3% for the pair IB/ciELISA tSAG1. The T. gondii seropositivity rate was 53.0% (61/115). Seropositive hinds to N. caninum were more likely to abort than seronegative hinds by the 3 assays. The OR for the association between N. caninum seropositivity and abortion was 72.70, 22.96 and 83.24 when ciELISA tSAG1, IFAT or IB assays were used, respectively. between T. gondii seropositivity and abortion. The three serologic assays were useful to detect N. caninum infected hinds. The validation of the assays for use in red deer would be an improvement for diagnosis of neosporosis in this species.

Antibody dynamics in Holstein Friesian heifers vaccinated with Brucella abortus strain 19, using seven serological tests.

The serological response induced by Brucella abortus strain 19 was evaluated in 52 Holstein females from a brucellosis-free herd using seven serological tests. Each calf was vaccinated at an age of 4 and 8 months old with 3 x 10(10) CFU B. abortus S19 and the antibody response was determined as the proportion of positive results to each test. The antibody dynamics, measured with the buffered plate antigen (BPA) test and the rapid automated presumptive (RAP) test, were similar. The proportion of positive reactions in these tests reached 100% one week after vaccination and remained at this level for seven weeks, after which the proportion of positive samples slowly declined to 8% (BPA) and 2% (RAP) at week 50. The response in the indirect enzyme immunoassay (i-ELISA) was similar, but shorter than that observed with the BPA/RAP. The antibody dynamic, measured using the seroagglutination test (SAT) in parallel with the 2-mercaptoethanol (2-Me) test and the complement fixation test (CFT) were similar to the RAP/BPA, but of slightly shorter duration. The competitive ELISA (c-ELISA) was positive in all animals for 3 weeks, followed by a rapid decline. The fluorescence polarization assay (FPA) reached a maximum of 68.5% positive animals at week 4 and then declined. Based on these data, the c-ELISA and FPA discriminated residual antibody activity due to vaccination more efficiently than the other tests.

Comparison of an indirect ELISA with the Brucella milk ring test for detection of antibodies to Brucella abortus in bulk milk samples.

An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of Brucella abortus antibodies in bovine bulk milk samples was evaluated. About 31 individual milk samples from B. abortus infected cows were diluted into bulk milk from a brucellosis free herd. Individual milk samples obtained from 96 negative or positive herds to ELISA or Brucella ring test (BRT), were tested by ELISA. All positive cows were bled and serum samples were tested by the complement-fixation test (CFT) which was considered the definitive test. A herd was considered infected if at least, one cow was positive in the CFT. Four samples were negative in the BRT at the dilution 1:10 but positive in the ELISA. For samples positive in both tests, BRT titers ranged from 1:10 to 1:480 while ELISA titers ranged from 1:10 to 1:3200. Using bulk milk samples, the sensitivity of the ELISA (98.1%) was higher than the BRT (72.2%) but the specificity of BRT (90.5%) was not statistically different (P=1.0) from the ELISA (88.1%). The implications of the results for brucellosis control are discussed.