Diagnostic tools to monitor udder health in dairy goats

Comprehensive RNA-seq profiling to evaluate the rabbit mammary gland transcriptome after mastitis

Mastitis is a relatively common disease in rabbit does. The aim of this study was to investigate a relationship between the severity of clinical signs and pathological observations and to analyze differentially expressed genes (DEGs) in the mammary gland with mastitis versus healthy mammary gland. The result showed that rectal temperatures of the rabbits with both mild mastitis and severe mastitis were higher than that of control. Cell counting results showed that the somatic cell count (SCC) only in milk of the rabbit with severe mastitis was significantly higher than that in the control group. However, the number of heterophils in the histological sections of mammary glands with mild mastitis was significantly higher than that of control. A total of 1,096 DEGs between the control and mastitis mammary glands was identified by RNA-sequencing (RNA-seq). Gene ontology (GO) showed that most of up-regulated genes were enriched in terms such as response to stimulus, signal transduction, and cell communication. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that these genes were mostly enriched in the pathways such as Rap1 signaling pathway, proteoglycans in cancer, and PI3K-Akt signaling pathway. However, the downregulated genes were mainly enriched in metabolic processes and significantly involved in metabolic pathways. The data provides useful information to further dissect the molecular genetic mechanisms underlying rabbit mastitis, which is a prerequisite for designing effective intervention strategies.

Novel Biomarkers of Mastitis in Goat Milk Revealed by MALDI-TOF-MS-Based Peptide Profiling

Mastitis is the most common infection of dairy goats impairing milk production and quality, which is usually recognized by mammary gland visual inspection and palpation. Subclinical forms of the disease are also widely represented, which lack the typical signs of the clinical ones but are still associated with reduced production and safety for human consumption of milk, generally presenting a high bacterial count. In order to obtain novel analytical tools for rapid and non-invasive diagnosis of mastitis in goats, we analyzed milk samples from healthy, subclinical and clinical mastitic animals with a MALDI-TOF-MS-based peptidomic platform, generating disease group-specific spectral profiles whose signal intensity and mass values were analyzed by statistics. Peculiar spectral signatures of mastitis with respect to the control were identified, while no significant spectral differences were observed between clinical and subclinical milk samples. Discriminant signals were assigned to specific peptides through nanoLC-ESI-Q-Orbitrap-MS/MS experiments. Some of these molecules were predicted to have an antimicrobial activity based on their strong similarity with homolog bioactive compounds from other mammals. Through the definition of a panel of peptide biomarkers, this study provides a very rapid and low-cost method to routinely detect mastitic milk samples even though no evident clinical signs in the mammary gland are observed.

Study on prevalence and bacterial etiology of mastitis, and effects of subclinical mastitis and stage of lactation on SCC in dairy goats in Egypt

In Egypt, inadequate information on prevalence and epidemiology of caprine mastitis is available. This study was designed to investigate prevalence and etiological agents of caprine mastitis and assess the efficacy of somatic cell count (SCC) as marker of subclinical mastitis (SCM) in dairy goats. This study was carried out on 249 randomly selected lactating goats in different lactation stages and examined clinically. Of these animals, 477 milk samples were aseptically collected and screened for bacterial carriage. SCC was assessed in 234 apparently normal milk samples, and SCC ≥ 10⁶ cells/ml was indicator for SCM. Prevalence of clinical mastitis (CM) was 33.73% and 16.87% at animal and udder-half levels, respectively. SCM was 52.56% in the apparently healthy halves. Culture results proved single infection in 49.69% of samples, mixed infection in 23.9% of samples, and 26.41% of samples were negative. Coagulase negative staphylococci (CNS) were the most predominant bacteria (58.75%), then Staphylococcus aureus (S. aureus) (24.375%), and Streptococci (1.875%) were the least. No significant difference was recorded between mean of SCC in bacteriologically positive and negative samples, neither in those with SCC ≤ 10⁶ nor with SCC ≥ 10⁶ cells/ml both in middle and late lactation stages. Besides, the percentage of animals harboring SCC ≥ 10⁶ cells/ml and negative for bacteriology in late lactation stage was 3 times (28.57%) more than in midlactation (9.3%). We can assume that SCC is not proper indicator for intra-mammary inflammation (IMI) in goats, and bacteriological examination remains more efficient, despites being time consuming and expensive.

Relationship of Late Lactation Milk Somatic Cell Count and Cathelicidin with Intramammary Infection in Small Ruminants

Late lactation is a critical moment for making mastitis management decisions, but in small ruminants the reliability of diagnostic tests is typically lower at this stage. We evaluated somatic cell counts (SCC) and cathelicidins (CATH) in late lactation sheep and goat milk for their relationship with intramammary infections (IMI), as diagnosed by bacteriological culture (BC). A total of 315 sheep and 223 goat half-udder milk samples collected in the last month of lactation were included in the study. IMI prevalence was 10.79% and 15.25%, respectively, and non-aureus staphylococci were the most common finding. Taking BC as a reference, the diagnostic performance of SCC and CATH was quite different in the two species. In sheep, receiver operating characteristic (ROC) analysis produced a higher area under the curve (AUC) value for CATH than SCC (0.9041 versus 0.8829, respectively). Accordingly, CATH demonstrated a higher specificity than SCC (82.92% versus 73.67%, respectively) at comparable sensitivity (91.18%). Therefore, CATH showed a markedly superior diagnostic performance than SCC in late lactation sheep milk. In goats, AUC was <0.67 for both parameters, and CATH was less specific than SCC (61.90% versus 65.08%) at comparable sensitivity (64.71%). Therefore, both CATH and SCC performed poorly in late lactation goats. In conclusion, sheep can be screened for mastitis at the end of lactation, while goats should preferably be tested at peak lactation. In late lactation sheep, CATH should be preferred over SCC for its higher specificity, but careful cost/benefit evaluations will have to be made.

Knowledge gaps and research priorities in Staphylococcus aureus mastitis control

This study assessed knowledge gaps and suggested research priorities in the field of Staphylococcus aureus mastitis. Staphylococcus aureus infecting the mammary gland remains a major problem to the dairy industry worldwide because of its pathogenicity, contagiousness, persistence in the cow environment, colonization of skin or mucosal epithelia, and the poor curing efficacy of treatments. Staphylococcus aureus also constitutes a threat to public health due to food safety and antibiotic usage issues and the potential for bidirectional transmission of strains between humans and dairy animals (cows and small ruminants). Gaps have been identified in (i) understanding the molecular basis for pathogenesis of S. aureus mastitis, (ii) identifying staphylococcal antigens inducing protection and (iii) determining the cell-mediated immune responses to infection and vaccination. The recommended priorities for research are (i) improved diagnostic methods for early detection of infection and intervention through treatment or management, (ii) development of experimental models to investigate the strategies used by S. aureus to survive within the mammary gland and resist treatment with anti-microbials, (iii) investigation of the basis for cow-to-cow variation in response to S. aureus mastitis, (iv) identification of the immune responses (adaptive and innate) induced by infection or vaccination and (v) antibacterial discovery programmes to develop new, more effective, narrow spectrum antibacterial agents for the treatment of S. aureus mastitis. With the availability and ongoing improvement of molecular research tools, these objectives may not be out of reach in the future.

Prevalence and pathogens of subclinical mastitis in dairy goats in China

Subclinical mastitis, a costly disease for the dairy industry, is usually caused by intramammary bacterial infection. The aim of this study was to investigate the prevalence of and pathogens involved in subclinical mastitis in dairy goats in China. A total of 683 dairy goats in the main breeding areas of China were selected, and milk samples were collected. Out of these, 313 (45.82 %) goats were detected distinct or strong positive for subclinical mastitis by using California mastitis test. Among these positive goats, 209 milk samples were used to identify the causing agents by a multiplex PCR assay, and results were listed as follows: coagulase-negative staphylococci (59.52 %), Staphylococcus aureus (15.24 %), Escherichia coli (11.43 %), and Streptococcus spp. (10.95 %). In conclusion, subclinical mastitis is a highly prevalent disease in dairy goats in China, and coagulase-negative staphylococci are the predominant pathogens.