Herd-level based seroprevalence and associated factors for Toxoplasma gondii in cows in the state of Paraíba, Northeastern Brazil / Soroprevalência em nível de rebanho e fatores associados para Toxoplasma gondii em vacas no estado da Paraíba, Nordeste do Brasil

We aimed to determine the herd and animal levels seroprevalence and associated factors for Toxoplasma gondii infections in cattle from the state of Paraíba, Northeastern Brazil. Herds (n = 434) and cows aged ≥ 24 months (n = 1,895) were randomly selected, and serum samples were tested with the immunofluorescence antibody test (IFAT) using as cutoff of 64. Of the 434 farms investigated, 197 had at least one seropositive cow (prevalence of 49.0%; 95% CI = 44.3%-53.8%), and the prevalence at animal level was 18.0% (95% CI = 5.3%-21.1%). The antibody titers ranged from 64 to 1024, with the most frequent titers being 64 (10.8%) and 128 (3.7%). The risk factors identified were property located in Sertão region (odds ratio [OR] = 3.07), property located in Agreste/Zona da Mata regions (OR = 2.00), animal purchasing (OR = 2.68), herd size of 34-111 animals (OR = 2.91) and herd size > 111 animals (OR = 6.97). The results suggest the wide distribution of T. gondii infections in cattle throughout the state of Paraíba, and the risk factors identified are not possible to correct.(AU)

Objetivou-se determinar a soroprevalência do rebanhos e de animais e os fatores associados à infecção por Toxoplasma gondii em bovinos do estado da Paraíba, Nordeste do Brasil. Rebanhos (n = 434) e vacas com idade ≥ 24 meses (n = 1.895) foram selecionados aleatoriamente, e as amostras de soro foram testadas com o teste de imunofluorescência (RIFI), usando-se como ponto de corte 64. Das 434 fazendas investigadas, 197 tiveram pelo menos uma vaca soropositiva (prevalência de 49%; IC 95% = 44,3%-53,8%), e a prevalência em nível de animais foi de 18% (IC 95% = 5,3%-21,1%). Os títulos de anticorpos variaram de 64 a 1024, sendo os títulos mais frequentes 64 (10,8%) e 128 (3,7%). Os fatores de risco identificados foram na propriedade localizada na região do Sertão ("odds ratio" [OR] = 3,07), na propriedade localizada na região do Agreste/Zona da Mata (OR = 2,00), na compra de animais (OR = 2,68), no tamanho do rebanho de 34-111 animais (OR = 2,91) e no tamanho do rebanho > 111 animais (OR = 6,97). Os resultados sugerem a ampla distribuição de infecções por T. gondii em bovinos em todo o estado da Paraíba, e os fatores de risco identificados não são passíveis de correção.(AU)

Establishing tools for early diagnosis of congenital toxoplasmosis: Flow cytometric IgG avidity assay as a confirmatory test for neonatal screening.

The aim of this study was to evaluate the performance of conventional serology (Q-Preven™ and ELFAVIDAS™) and flow cytometry-based serologic tools for early serologic diagnosis of congenital toxoplasmosis. The study groups included prospectively confirmed cases of congenital toxoplasmosis (TOXO=88) and age-matching non-infected controls (NI=15).The results demonstrated that all samples tested positive/indeterminate for anti-T. gondii IgM screening at birth using air-dried whole blood samples. Serum samples collected at 30-45days after birth tested positive for ELFAVIDAS™ IgG in both groups. While all NI tested negative for ELFAVIDAS™ IgM and IgA, only 78% and 36% of TOXO tested positive for IgM and IgA, respectively. Flow cytometry-based anti-T. gondii IgM, IgA and IgG reactivity displayed moderate performance with low sensitivity (47.6%, 72.6% and 75.0%, respectively). Regardless the remarkable specificity of IgG1, IgG2 and IgG3 subclasses for early diagnosis, weak or moderate specificity was observed (Se=73.9%, 60.2% and 83.0%, respectively). The analysis of IgG avidity indices (AI) demonstrated the highest performance among the flow cytometry-based methods (Se=96.6%; Sp=93.3%), underscoring the low avidity index (AI<60%) within TOXO (97.0%) in contrast with the high avidity index (AI>60%) in NI (93%). Analysis of anti-T. gondii IgG and IgG3 reactivity for mother:infant paired samples may represent a relevant complementary tests for early diagnosis. In conclusion, a feasible high-standard algorithm (Accuracy=97.1%) was proposed consisting of Q-Preven™ IgM screening at birth, followed by ELFAVIDAS™ IgM and flow cytometric IgG avidity analysis at 30-45days after birth as a high performance tool for early serological diagnosis of congenital toxoplasmosis.