[Epidemiology of caprine and ovine brucellosis in Formosa province, Argentina]. / Epidemiología de la brucelosis caprina y ovina en la provincia de Formosa, Argentina.

An epidemiological study of brucellosis was carried out in 516 goats and mixed flocks (goat/sheep) from the three agro-ecological regions of Formosa province, Argentina. Serum samples from a total of 25401 goats and 2453 sheeps were analyzed using buffered plate agglutination test (BPAT) and complement fixation test (CFT). Bacteriological and PCR analyses on milk samples from goats in three flocks with a history of brucellosis and recent abortions were also performed. Brucellosis was detected in four of the nine departments of the province with an overall prevalence of 2% and an intra-flock prevalence ranging between 1% and 40%. The proportion of infected flocks was 3.6%, 12% and 36% for the eastern, central and western regions, respectively. Brucella melitensis bv. 1 was isolated efrom goats for the first time in the province. The expected fragments of 827bp from the omp2ab gene (Brucella spp.) and 731bp from the insert IS711 (B. melitensis) were amplified by PCR. Detection of antibodies by BPAT and FCT in sheep cohabiting with goats suggests that infections could have been caused by B. melitensis, posing an additional risk to public health. Control and eradication programs for brucellosis should consider mixed flocks as a single epidemiological unit. The results indicate that brucellosis by B. melitensis bv1 is highly endemic in the central and western regions of Formosa province.

Evaluation of a competitive inhibition ELISA based on the recombinant protein tSAG1 to detect anti-Neospora caninum antibodies in cattle.

Neospora caninum is a protozoan parasite that causes abortion and important economic losses in cattle worldwide. There are no treatments or vaccines available; disease control is based on diagnosis and herd management strategies. We developed, validated, and evaluated under field conditions a competitive inhibition ELISA based on the truncated SAG1 protein (tSAG1), expressed in Escherichia coli, and the RafNeo5 monoclonal antibody (ciELISAtSAG1). A criterion based on the 3-y sequential serologic analysis of 230 dairy cows by IFAT was used as the gold standard. The assay was validated using 860 serum samples from cows that were consistently positive or negative by IFAT throughout the study period. ciELISAtSAG1 was then used to evaluate the prevalence of neosporosis in 16 beef cow herds (22 samples per herd, 352 total samples). The results were compared with those from IFAT and a commercial cELISA (cELISAVMRD). The ciELISAtSAG1 cutoff was ≥ 29%I, with a diagnostic sensitivity of 98.7% (95% CI = 96.8-99.7%) and a diagnostic specificity of 97.9% (95% CI = 96.4-99.0%). Concordance among IFAT, cELISAVMRD, and ciELISAtSAG1 was 90.3%. The agreement (κ) between ciELISAtSAG1 and the other 2 tests was ≥ 0.81. The overall prevalence of neosporosis in the 16 beef herds was 30% (range: 5-60%). The ciELISAtSAG1 could be useful for large-scale detection of anti-N. caninum antibodies in cattle and seroepidemiologic investigations, given its appropriate sensitivity and specificity, and the simplicity of production.

Efficiency of a recombinant MSA-2c-based ELISA to establish the persistence of antibodies in cattle vaccinated with Babesia bovis.

Bovine babesiosis is caused by Babesia bovis and B. bigemina in Argentina. These protozoans are prevalent north of parallel 30 degrees S, where their natural vector Rhipicephalus (Boophilus) microplus is widespread. To prevent babesiosis outbreaks in endemic areas, an increasing population of 4-10-month-old calves are vaccinated with low virulence B. bovis R1A (BboR1A) and B. bigemina S1A (BbiS1A) strains. In non-endemic areas, an additional calf population is also vaccinated and boostered as adults, before they are relocated to R. microplus-endemic areas of the country. Serological tests are currently utilized not only to determine the status of natural Babesia spp. infections, but also to confirm the infection caused by vaccine strains. For this purpose, an indirect enzyme immunoassay (ELISA) based on the recombinant major surface antigen-2c (rMSA-2c) of B. bovis expressed in Escherichia coli, was standardized using sera from Babesia spp. experimentally infected cattle. ELISA(rMSA-2c) was validated using sera obtained weekly during 336 days from steers primed and boostered with BboR1A and/or BbiS1A on days 0 and 154, then compared with the immunofluorescent-antibody test (IFAT). Western blot (WB) protein analysis was used to confirm the specificity of the immune response to rMSA-2c. The sensitivity and specificity for ELISA(rMSA-2c) were 92 and 96% after the Babesia spp. priming and 88 and 73% after the boostering immunization, respectively. The sensitivity and specificity for IFAT were 99 and 90% after priming and 92 and 98% after boostering, respectively. Unlike IFAT, ELISA(rMSA-2c) detected a remarkable delayed booster response and a significant drop in specificity between 35 and 84 days after the booster immunization. Simultaneously, 87.5% of cattle boostered with B. bigemina showed cross-reactions in the ELISA(rMSA-2c), particularly between 63 and 77 days after the inoculation. A reaction against E. coli was observed, since bands of approximately 40 and/or 42kDa were detected using sera from cattle before and after Babesia spp. inoculations. ELISA(rMSA-2c) showed to be useful between 42 and 98 days after priming with Babesia spp. live vaccine to evaluate the success of infecting cattle. However, after boostering the test showed low specificity.

Epidemiología de la brucelosis caprina y ovina en la provincia de Formosa, Argentina / Epidemiology of caprine and ovine brucellosis in Formosa province, Argentina

Se realizó un estudio epidemiológico de brucelosis en 516 majadas caprinas o mixtas (caprinos/ovinos) de las 3 regiones agroecológicas de la provincia de Formosa, Argentina. Mediante las pruebas de aglutinación en placa con antígeno tamponado y de fijación del complemento en suero se estudiaron un total de 25.401 caprinos y 2.453 ovinos. Además, se realizaron cultivos bacteriológicos y PCR en muestras de leche de cabras de 3 majadas con brucelosis y abortos recientes. Se detectó brucelosis en 4 de los 9 departamentos de la provincia, la prevalencia global fue del 2 % y la intrapredial varió entre el 1 y el 40%. La proporción de majadas positivas fue del 3,6, el 12 y el 36 % para las regiones este, centro y oeste, respectivamente. Se aisló Brucella melitensis bv. 1 de cabras por primera vez en la provincia. La PCR amplificó fragmentos esperados de 827 pb correspondiente al gen omp2ab (Brucella spp.) y de 731 pb correspondiente al inserto IS711 (B. melitensis). La detección de anticuerpos en ovinos que cohabitan con caprinos sugiere que las infecciones habrían sido causadas por B. melitensis, lo que constituye un riesgo adicional para la salud pública. Los programas de control y erradicación de la brucelosis deberían considerar las majadas mixtas como una sola unidad epidemiológica. Los resultados indican que la brucelosis por B. melitensis bv. 1 es altamente endémica en las regiones centro y oeste de la provincia de Formosa.

An epidemiological study of brucellosis was carried out in 516 goats and mixed flocks (goat/sheep) from the three agro-ecological regions of Formosa province, Argentina. Serum samples from a total of 25401 goats and 2453 sheeps were analyzed using buffered plate agglutination test (BPAT) and complement fixation test (CFT). Bacteriological and PCR analyses on milk samples from goats in three flocks with a history of brucellosis and recent abortions were also performed. Brucellosis was detected in four of the nine departments of the province with an overall prevalence of 2 % and an intra-flock prevalence ranging between 1 % and 40 %. The proportion of infected flocks was 3.6 %, 12 % and 36 % for the eastern, central and western regions, respectively. Brucella melitensis bv. 1 was isolated efrom goats for the first time in the province. The expected fragments of 827 bp from the omp2ab gene (Brucella spp.) and 731 bp from the insert IS711 (B. melitensis) were amplified by PCR. Detection of antibodies by BPAT and FCT in sheep cohabiting with goats suggests that infections could have been caused by B. melitensis, posing an additional risk to public health. Control and eradication programs for brucellosis should consider mixed flocks as a single epidemiological unit. The results indicate that brucellosis by B. melitensis bv1 is highly endemic in the central and western regions of Formosa province.