Publications

3996

Abstract Background: Candidatus Phytoplasma ulmi is the causative agent of elm yellows and has been categorised in the European Union as a quarantine pathogen in the past. For central and northern European countries, information on the occurrence and distribution of the pathogen and its impact on elms is scarce, so a survey of native elm trees has been conducted in Germany. Results: About 6,500 samples in total, from Ulmus minor , Ulmus laevis and Ulmus glabra , were collected nationwide. Phytoplasma detection was performed by applying a universal 16Sr DNA-based real-time PCR assay and a novel Ca . P. ulmi species-specific real-time PCR assay targeting the 16S-23S spacer region. Both assays revealed that 28% of the samples were infected by Ca . P. ulmi, but infection rates of the elm species and regional incidences differed. The infection of trees is not correlated to disease-specific symptoms. The survey identified a regional disparity of infection which was high in east, south and central Germany, whereas only a few infected sites were found in the western and northern parts of the country. No correlation was apparent between altitude level and the prevalence of infection. First insights into the monitoring of the seasonal titre of Ca . P. ulmi in an infected tree by real-time PCR revealed high colonisation in all parts of the tree throughout the year. Conclusions: Ca . P. ulmi-infection is widely present in elms in Germany. The rare occurrence of symptoms indicates either a high degree of tolerance in elm populations or a low virulence of pathogen strains enabling high infection rates in a long-living host.

Background and Aim: Wildlife animals are reservoirs of a large number of microorganisms pathogenic to humans, and ticks could be responsible for the transmission of these pathogens. Rickettsia spp. are the most prevalent pathogens found in ticks. This study was conducted to detect Rickettsia spp. in ticks collected from free-living and illegally trafficked reptiles from the Department of Córdoba, Colombia. Materials and Methods: During the period from October 2011 to July 2014, ticks belonging to the family Ixodidae were collected, preserved in 96% ethanol, identified using taxonomic keys, and pooled (between 1 and 14 ticks) according to sex, stage, host, and collected place for subsequent DNA extraction. Rickettsia detection was performed using real-time polymerase chain reaction (RT-PCR), followed by conventional PCR to amplify a larger fragment of the gltA and 16S rRNA genes. The amplicons were sequenced using the Sanger method, and the nucleotide sequences were subjected to BLAST analysis to identify homologous sequences in GenBank, after which phylogenetic analysis was performed using the MEGA X software. Results: In total, 21 specimens of nine species of reptiles were sampled, from which 805 Amblyomma dissimile ticks were collected, but only 180 ticks were selected to create 34 groups. The DNA of Rickettsia spp. was detected in 30/34 (88%) groups. The sequences of the gene gltA and 16S rRNA revealed a 100% identity with Candidatus Rickettsia colombianensi (GenBank: KF905456 and GenBank: KF691750). Conclusion: A. dissimile was the only tick found in all the sampled reptiles. The presence of Candidatus Rickettsia colombianensi in reptile ticks could represent a public health problem due to the risk of transmission to humans and the introduction of microorganisms to other geographical areas.

Huanglongbing (HLB) or citrus greening disease is the most devastating disease of citrus worldwide. This disease, caused by the bacterium ‘Candidatus Liberibacter asiaticus’ (CLas), leads to low fruit quality and unproductive trees. In 2008, HLB was found in a residential citrus tree in Savannah, Georgia, and, as a result, the state has been quarantined for this disease since 2009. Nonetheless, little is known about the distribution of CLas within Georgia, even though the commercial planting of citrus in Georgia has increased exponentially in recent years. In 2019, 94 samples from commercial and residential citrus trees within 11 counties in coastal and southern Georgia were collected and tested for the presence of CLas. Molecular testing results revealed the presence of CLas in three counties where HLB had not been previously reported and in 9% of samples overall. This is the first definitive report confirming HLB in southern Georgia counties besides those along the coast.