Listeriosis is a disease that is induced by infection with the Gram-positive bacterium Listeria monocytogenes. Much is still unknown about the pathogenesis of encephalitic listeriosis. We aimed to identify the contribution of glial fibrillary acidic protein (GFAP), epithelial cadherin (E-cadherin), S100, and acute-phase proteins (APPs) in pathogenesis, clinical and preclinical diagnosis of natural cases of encephalitic listeriosis. Of 1,325 Ossimi sheep, 64 were suspected of having listeriosis from 2018 to 2020. Prospective cohort evaluation of clinical and postmortem findings was performed, in addition to bacterial isolation, the measurement of APPs in serum and cerebrospinal fluid (CSF), and the histopathological and immunohistochemical evaluation of GFAP, S100, and E-cadherin. Infected sheep showed nervous symptoms ranging from neck stretching to complete paralysis. APPs were significantly increased in the CSF of both clinically and preclinically diseased animals; however, serum APPs were only significantly increased in clinically diseased animals. Histopathological evaluation revealed microabscesses, meningoencephalitis, and perivascular cuffing of the brainstem of infected sheep. Immunohistochemical investigations revealed strong expression of GFAP and S100 in necrotic areas and negative expression of E-cadherin. The measurement of CSF APPs could be useful in the preclinical diagnosis of sheep listeriosis. GFAP and S100 proteins could be involved in the pathogenesis of listeriosis; however, E-cadherin does not appear to be involved.

Subacute ruminal acidosis (SARA) is a prevalent metabolic disorder in dairy cows known to elicit local and systemic immune responses. We recently showed that cows experiencing SARA and challenged intramammarily with lipopolysaccharide (LPS) experienced stronger metabolic disturbances compared with cows without SARA. Therefore, we hypothesized that cows experiencing SARA have a modulated innate immune response and impaired plasma metabolome compared with healthy cows when experiencing an acute mastitis challenge. A total of 18 Simmental cows were subjected either to a Control (CON, n=6) or SARA (n=12) feeding regimen, receiving either 40% or 60% concentrates for 30 days. Thereafter, six SARA (SARA-LPS) and the CON (CON-LPS) cows were intramammarily challenged with 50 µg LPS from Escherichia coli (O26 : B6), while the remaining six SARA cows (SARA-PLA) received a placebo. Blood and milk samples were analyzed for acute phase proteins and a targeted ESI-LC-MS/MS-based metabolomics approach was performed in blood samples 24 h after the LPS challenge. The LPS infusion caused a strong increase in immune response variables, with a higher concentration of milk amyloid A 48 h after the LPS challenge in SARA-LPS compared with CON-LPS cows. Cows receiving the LPS infusion had a lower plasma concentration of several amino acids and lysophosphatidylcholines but without differences in SARA cows and healthy cows. In conclusion, our results revealed that an intramammary LPS infusion increased acute phase proteins and modulated the blood metabolome. While no systemic differences between SARA and healthy cows were observed, cows experiencing SARA showed a higher concentration of an acute phase protein at the local level of the mammary gland. Further research is required to elucidate the underlying mechanisms and to evaluate its clinical significance for udder health.

Acute phase response (APR) in developing embryos/larvae remains poorly studied in fish, and information regarding the expression and role of acute phase proteins (APPs) in developing embryos/larvae is rather limited in teleosts. In this study we investigated the APR in zebrafish (Danio rerio) embryos/larvae challenged with LPS by examining the expression of APP genes encoding CRP, SAA, LECT2, HAMP and HP and APP inducer genes encoding IL-1β and TNF-α. Expression of all the seven genes was up-regulated in embryos/larvae after challenge with LPS as revealed by q-RT-PCR. Whole-mount in situ hybridization (WISH) showed that all the genes displayed strong maternal expression in the cleavage and blastula stages, and ubiquitous expression in the gastrula and segmentation stage embryos, and then they were expressed differently in specific tissues in later developmental stages. Interestingly, challenge with LPS resulted in de novo expression of the SAA gene in the yolk sac and intestine, the LECT2 gene in the yolk sac, and the IL-1β gene in the yolk sac and the dispersed neutrophils of caudal vein, and visible enhanced expression of the LECT2 gene in the yolk sac. These are the first such data reported in teleosts, showing that LPS challenge is able to modify the expression patterns of APP and APP inducer genes. Altogether, these data suggest that zebrafish embryos/larvae are able to respond to acute infection though their immune system remains in a developing and immature state.

Genetic studies have demonstrated profound differences between the ‘porcine’ genotype of Cryptosporidium parvum, versus ‘human’ and ‘bovine’ genotypes. The study analysed infectivity and pathogenicity of the ‘porcine’ genotype (CPP-13 isolate) of C. parvum, and compared the results with published data on the ‘bovine’ genotype (CPB-0 isolate). This was investigated in calves and piglets from commercial herds. Piglets were mildly affected by the CPP-13 isolate, contrary to piglets infected with the CPB-0 isolate, which caused diarrhoea of a mean duration of 3·5 days. CPP-13 produced no or very mild clinical signs in piglets despite the excretion of high numbers of oocysts. Concomitant infection with rotavirus, however, caused a dramatic aggravation of the clinical signs, and 5 of 6 experimentally infected piglets died. CPP-13 appeared to be adapted to porcine hosts as illustrated by the lack of infectivity to 1 experimentally inoculated calf, and the absence of clinical signs, the long pre-patent period (15 days), and the excretion of very low numbers of oocysts following experimental infection of another calf. Thus, in accordance with other molecular studies, our results support the genetic evidence for the existence of a new species of Cryptosporidium adapted to pigs.