Circulating hypervirulent Marek's disease viruses in vaccinated chicken flocks in Taiwan by genetic analysis of meq oncogene.

Marek's disease (MD) is an important neoplastic disease caused by serotype 1 Marek's disease virus (MDV-1), which results in severe economic losses worldwide. Despite vaccination practices that have controlled the MD epidemic, current increasing MD-suspected cases indicate the persistent viral infections circulating among vaccinated chicken farms in many countries. However, the lack of available information about phylogeny and molecular characterization of circulating MDV-1 field strains in Taiwan reveals a potential risk in MD outbreaks. This study investigated the genetic characteristics of 18 MDV-1 strains obtained from 17 vaccinated chicken flocks in Taiwan between 2018 and 2020. Based on the sequences of the meq oncogene, the phylogenetic analysis demonstrated that the circulating Taiwanese MDV-1 field strains were predominantly in a single cluster that showed high similarity with strains from countries of the East Asian region. Because the strains were obtained from CVI988/Rispens vaccinated chicken flocks and the molecular characteristics of the Meq oncoprotein showed features like vvMDV and vv+MDV strains, the circulating Taiwanese MDV-1 field strains may have higher virulence compared with vvMDV pathotype. In conclusion, the data presented demonstrates the circulation of hypervirulent MDV-1 strains in Taiwan and highlights the importance of routine surveillance and precaution strategies in response to the emergence of enhanced virulent MDV-1.

Trifolium pratense as a novel phytogenic supplement, is an anticoccidial agent in chickens.

Coccidiosis, caused by a protozoan parasite of the genus Eimeria, is one of the most severe contagious parasite diseases affecting the poultry industry worldwide. Using phytogenics to prevent chicken coccidiosis is a strategy aimed at combating the increasing issue of drug-resistant strains of Eimeria spp. This study demonstrates the anticoccidial activities of a medicinal herb, Trifolium pratense (TP) powder, and its ethanolic extract (designated TPE) against Eimeria spp. TPE exhibited significant suppressive activity against E. maxima oocyst sporulation and E. tenella sporozoite invasion and reproduction in Madin-Darby bovine kidney cells. Furthermore, administration of basal chicken diets containing TP powder or TPE to Eimeria-infected chickens significantly reduced the output of oocysts and severity of intestinal lesions. Dietary supplementation with TP significantly improved relative weight gain in E. tenella- and E. acervulina-infected chickens, while there was no significant improvement in E. maxima-infected chickens. The anticoccidial activities of TP and TPE on E. acervulina, E. tenella and E. maxima were further supported by anticoccidial index scores, which showed greater efficacy than those of amprolium, a commercial coccidiostat used in poultry. TP supplementation positively impacted the primary metabolism of chickens challenged with E. tenella or E. acervulina. The chemical fingerprints of TPE were established using liquid column chromatography; TPE contained 4 major compounds: ononin, sissotrin, formononetin, and biochanin A. In addition, various spectrometric methods were used to ensure the batch-to-batch consistency of TP/TPE. In conclusion, T. pratense is demonstrated to be a novel phytogenic supplement that can be used to control Eimeria-induced coccidiosis in chickens.