Echotextural and ultrasonic detection of sub-clinical and clinical mastitis

Worldwide mastitis can be regarded as the most serious disease afflicting dairy cattle, with a substantial influence on production and profitability. The disease can be classified into three types based on the severity of the inflammation: sub-clinical, chronic and clinical. Visual abnormalities such as red and swollen teats and fever are easily detectable in the clinical form, but subclinical mastitis does not show observable changes apart from a non-specific rise in SCC. Thus, a crucial component of treatment is timely and correct identification of the disease with other means as with relying only on SCC.

Since mastitis resistance and milk SCC have a close relationship with udder and teat conformation features, selecting cows with ideal udder and teat shape may be a proposition. Also, the use of technologies such as sonography to detect udder health should be pursued. Ultrasound is commonly used in human medicine to check the mammary glands, for example to differentiate between cystic and solid lesions using 5-13 MHz scanners. Ultrasound is a non-invasive and non-destructive diagnostic tool which could provide real time images of the healthy and mastitic organ. Furthermore, with the help of ultrasonography, it is possible to look for haematomas, abscesses, inflammation, tissue growth, congenital malformations, mucosal lesions etc. in the udder.

The studies cited are part of a programme to investigate the efficacy of these methodologies, the specific objectives being: (1) to investigate the echotextural parameters, numerical pixel values (NPVs) and pixel heterogeneity (PSDs) of the lymph node and udder parenchyma, as well as the correlation between echotextural parameters and electrical conductivity (EC), in order to develop it as an alternative to laboratory testing for mastitic diagnosis and prognosis; (2) to test whether the ultrasonographic morphometry and characteristic traits of udders and teats could be effectively used to identify clinical mastitis.

The ultrasonographic images of each quarter of 48 Holstein cows in their third lactation were processed using digital image analyses to obtain mean NPVs and mean PSDs of the mammary gland and lymph node parenchyma. Udder parenchyma as echotexture, teat width (TW), teat width at the rosette of Furstenberg, teat cistern width (TC), teat wall thickness (TWT), teat canal length (TCL), and the ratios TC/TWT, TWT/TW and TC/TW, as well as the supramammary lymph node size were evaluated, whereas the phenotypic morphometric traits: udder circumference, depth and length, and teat length, diameter and circumference, and the shortest distance from teat ends to the floor were measured.

Results showed that the mean EC increased with the progression of infection. The mean NPVs of lymph node parenchyma decreased, whereas the mean NPVs of udder parenchyma increased from healthy to subclinical to clinical cases, respectively. The mean PSDs of lymph node and udder parenchyma increased with the progression and severity of infection from healthy to subclinical and clinical cases, respectively. There was a substantial difference between morphological parameters of the teat such as teat width, teat width at the rosette, teat wall thickness, ratio of TC/TWT, ratio of TWT/TW, ratio TC/TW, teat canal length, echogenicity variables, and phenotypic morphometric traits, except for the teat cistern width. A Pearson correlation indicated a strong correlation between lymph node length and lymph node width.

It was concluded that the variation in echotextural variables (NPVs and PSDs) of mammary gland and supramammary lymph node parenchyma and electrical conductivity appeared to be good indicators for the diagnostic and prognostic evaluation of sub-clinical and clinical mastitis, and simultaneously may assist in the evaluation of udder health status. Secondly, in general, clinical mastitis is related to udder and teat morphometric traits. Thus, by incorporating these characteristics into the selection and breeding programme may aid in the selection of cows more resistant to mastitis. Thirdly, ultrasound will be an effective imaging and morphological assessment tool for the diagnosis and prognosis of clinical mastitis.