INTRODUCTION The tick Ixodes ricinus is widely recognized as the most important ectoparasite in Europe. Widespread across the entire continent, I. ricinus is a vector of many pathogens, including bacteria, viruses and protozoa. I. ricinus hosts a symbiotic bacterium, Midichloria mitochondrii ascribed to the Midichloriaceae family (Rickettsiales) (Montagna et al., 2013, Appl. Environ. Microbiol. 79:3241-48).This bacterium is present in all stages of I. ricinus development, with a prevalence of 100% and it is transmitted to the tick host through the blood meal. Indeed, humans and animals parasitized by I. ricinus develop antibodies against this bacterium (Mariconti et al., 2012, Pathog. Glob. Health. 106:391-96; Bazzocchi et al., 2013, Parasit Vectors. 6:3503) and the DNA of M. mitochondrii has been amplified in the blood of parasitized vertebrates. No studies have been conducted on the fate of M. mitochondrii in the host and no information are available on the symbiosis between the bacterium and the tick. The aim of the project is to investigate the effect of the antibiotic tetracycline on the amount of M. mitochondrii after microinjection of adult females of I. ricinus and after a blood meal of larvae on treated and control gerbils. MATERIAL AND METHODS Samples have been collected by colleagues in Nantes (France) and sent us for subsequent analysis. Two fully engorged females collected on roe-dear in France have been microinjected with a single dose of tetracycline (15ng/mg). Three fully engorged females have been used as controls. After oviposition, larvae have been fed on control gerbils (one for each tick) or on gerbils treated with tetracycline (one for each tick). The gerbil treatment consisted of 10mg/kg of antibiotic injected two times for force feeding; subsequently tetracycline 1.2% (w/v) has been administered to gerbils in drinking water for 6 days. Larvae before and after the blood meal have been stored at -80°C until use. DNA from larvae after oviposition (ten sample for each tick for a total of 50 larvae) and larvae after the blood meal on each gerbil (for a total of 100 larvae) was extracted by using a commercial kit. Burdens of M. mitochondrii in each samples were estimated by quantitative PCR. Target genes for the absolute quantification were: gyrB gene for M. mitochondrii and calreticulin for I. ricinus. Statistical analysis have been performed. RESULTS Burden of M. mitochondrii is expressed as the ratio gyrB/cal x1000. The obtained results show a large variability in the amount of bacteria presents in unengorged larvae derived from different I. ricinus tick probably due to the variability of the number of M. mitochondrii in each adult female. Furthermore, microinjection of tetracycline doesn’t seem to reduce the amount of bacteria in larvae; despite this, the number of produced eggs is decreased. Encouraging results have been obtained testing the presence of M. mitochondrii after the blood meal on control gerbils and gerbils treated with tetracycline. The ratio gyrB/cal x1000 indeed shows a decreasing of bacteria in engorged larvae derived from treated animals. CONCLUSIONS The role of M. mitochondrii in the tick I. ricinus is still unknown. The reduction of bacteria in larvae after the blood meal on treated gerbils open the way to the study of the possible role of M. mitochondrii in the tick development stages.
|Titolo:||Antibiotic treatment of the tick vector Ixodes ricinus: effects on Midichloria mitochondrii|
|Parole Chiave:||midichloria; mitochondrii; tick; ixodes; ricinus; antibiotic; treatment; tetracycline; larvae; gerbil|
|Settore Scientifico Disciplinare:||Settore VET/06 - Parassitologia e Malattie Parassitarie degli Animali|
|Data di pubblicazione:||giu-2014|
|Enti collegati al convegno:||Società Italiana di Parassitologia|
|Tipologia:||Book Part (author)|
|Appare nelle tipologie:||03 - Contributo in volume|