No abstract

Histomonosis is a parasitic disease of poultry with worldwide prevalence. The disease can cause morbidity and mortality in chicken and turkey flocks entailing severe economic losses. In the first half of the last century, there was a high demand to control histomonosis as the turkey industry was severely affected by the disease. Consequently, numerous chemical compounds were tested for their efficacy against Histomonas meleagridis with varying outcomes, that are summarized and specified in this review. At the same time, preliminary attempts to protect birds with cultured histomonads indicated the possibility of vaccination. Several years ago antihistomonal drugs were banned in countries with tight regulations on pharmaceuticals in order to comply with the demand of consumer protection. As a consequence, outbreaks of histomonosis in poultry flocks increased and the disease became endemic again. New approaches to prevent and treat histomonosis are, therefore, needed and recently performed studies focused on various areas to combat the disease, from alternative chemotherapeutic substances to plant-derived compounds until vaccination, altogether reviewed here. Considering existing regulations and the overall outcome of experimental studies, it can be concluded that vaccination is very promising, despite the fact that various challenges need to be addressed until the first ever developed vaccine based upon live flagellates in human or bird medicine can be marketed.

No abstract

In recent years, Trichomonas gallinae emerged as the causative agent of an infectious disease of passerine birds in Europe leading to epidemic mortality of especially greenfinches Chloris chloris and chaffinches Fringilla coelebs. After the appearance of finch trichomonosis in the UK and Fennoscandia, the disease spread to Central Europe. Finch trichomonosis first reached Austria and Slovenia in 2012. In the present study the genetic heterogeneity of T. gallinae isolates from incidents in Austria and Slovenia were investigated and compared with British isolates. For this purpose comparative sequence analyses of the four genomic loci ITS1-5.8S-ITS2, 18S rRNA, rpb1 and Fe-hydrogenase were performed. The results corroborate that one clonal T. gallinae strain caused the emerging infectious disease within passerine birds and that the disease is continuing to spread in Europe. The same clonal strain was also found in a columbid bird from Austria. Additionally, the present study demonstrates clearly the importance of multi-locus sequence typing for discrimination of circulating T. gallinae strains.

New enzymes of nicotine catabolism instrumental in the detoxification of the tobacco alkaloid by Arthrobacter nicotinovorans pAO1 have been identified and characterized. Nicotine breakdown leads to the formation of nicotine blue from the hydroxylated pyridine ring and of γ‐N‐methylaminobutyrate (CH3‐4‐aminobutyrate) from the pyrrolidine ring of the molecule. Surprisingly, two alternative pathways for the final steps in the catabolism of CH3‐4‐aminobutyrate could be identified. CH3‐4‐aminobutyrate may be demethylated to γ‐N‐aminobutyrate by the recently identified γ‐N‐methylaminobutyrate oxidase [Chiribau et al. (2004) Eur J Biochem271, 4677–4684]. In an alternative pathway, an amine oxidase with noncovalently bound FAD and of novel substrate specificity removed methylamine from CH3‐4‐aminobutyrate with the formation of succinic semialdehyde. Succinic semialdehyde was converted to succinate by a NADP+‐dependent succinic semialdehyde dehydrogenase. Succinate may enter the citric acid cycle completing the catabolism of the pyrrolidine moiety of nicotine. Expression of the genes of these enzymes was dependent on the presence of nicotine in the growth medium. Thus, two enzymes of the nicotine regulon, γ‐N‐methylaminobutyrate oxidase and amine oxidase share the same substrate. The Km of 2.5 mm and kcat of 1230 s−1 for amine oxidase vs. Km of 140 µm and kcat of 800 s−1 for γ‐N‐methylaminobutyrate oxidase, determined in vitro with the purified recombinant enzymes, may suggest that demethylation predominates over deamination of CH3‐4‐aminobutyrate. However, bacteria grown on [14C]nicotine secreted [14C]methylamine into the medium, indicating that the pathway to succinate is active in vivo.