Development of an immunosensor assay for detection of haptoglobin in mastitic milk.

BACKGROUND: Detection of subclinical mastitis in dairy cows is important, as it represents a major economic challenge for the dairy industry worldwide owing to propagation of mastitis-causing pathogens and to long-term reduction in milk yield and quality. Haptoglobin (Hp) is one of the most sensitive acute phase proteins in milk during udder inflammation and as an indicator of mastitis. OBJECTIVES: The aim of this study was to develop a rapid and sensitive immunosensor assay for measuring Hp concentration in mastitic milk. METHODS: The immunosensor was constructed by immobilizing anti-bovine Hp antibody on a gold electrode through gold nanoparticles fabricated on self-assembled L-cysteine layers. The immunosensor assay was used to measure Hp concentration in 20 milk samples positive for bacteria with a somatic cell count > 5 × 10(5) cells/mL from cows without clinical signs of mastitis. Results were compared with those obtained using a commercial ELISA kit. RESULTS: Reproducibility of Hp measurement and stability after storage for 20 days were good for the immunosensor assay. Measurement of Hp was linear over a range of 15-100 mg/L, with a limit of detection of 0.63 mg/L. Agreement between results obtained with the immunosensor and ELISA methods was satisfactory as analyzed using the Wilcoxon signed-rank test (Z = -1.739, P = .073). CONCLUSION: An immunosensor assay for measuring Hp in milk provided rapid results and was easy to perform, facilitating its potential use in the field for the diagnosis of subclinical mastitis once a cutoff value for Hp concentration is established.

Pathological observations of an experimental infection of geese with goose circovirus.

There is so far no report describing the pathogenicity of goose circovirus (GoCV) following experimental infection. We report here an experimental inoculation of 21-day-old geese with a GoCV polymerase chain reaction (PCR)-positive sample of bursa of Fabricius (BF) homogenate, and the results of clinicopathological changes. Forty geese were randomly assigned to two groups: the inoculated group (n=30) receiving tissue homogenate and the uninoculated group (n=10) receiving a placebo (physiological saline). Tissue samples were collected for histopathological examination and GoCV detection. The main clinical signs in the GoCV-inoculated geese included diarrhoea at 17 to 30 days post inoculation, marked differences of growth rate and feather disorders in three of the geese. Viraemia was detected by PCR only at 14 days post inoculation. The BF, thymus, spleen, duodenum and liver of some inoculated geese were also PCR-positive. Real-time PCR showed that there was relatively more viral load in the BF. Histological examination revealed lymphocytic depletion and histiocytosis in the BF and inflammation characterized by lymphatic infiltration in the lung, liver and kidney. Immunohistochemistry applied to PCR-positive samples showed that in only three BF samples was GoCV antigen detected in lymphocytes in both the cortex and medulla. In situ apoptosis detection of all BF samples indicated that GoCV inoculation was associated with an increase in bursal lymphocytic apoptotic events.