Ecoepidemiology of Rckettsia parkeri in the Paraná Delta, Argentina

BELDOMENICO PABLO MARTIN; COLOMBO VALERIA CAROLINA; MONJE LUCAS; ANTONIAZZI LEANDRO RAUL; NAVA SANTIAGO

Hyderabad

Congreso; XVII International Congress of Infectious Diseases; 2016

International society of infectious diseases

Type:PosterPresentationEcoepidemiologyofRickettsiaparkeriintheParanáDelta,ArgentinaP.M. Beldomenico,∗, V. Colombo, L. Monje,L. Antoniazzi, S. NavaBackground: In South America, several cases of human rickettsiosiscausedbyRickettsiaparkeriweredocumentedinUruguay,southern Brazil and the Paraná River delta of Argentina. There, themain tick vector isAmblyommatriste. Adults ofA.triste seek bloodmealsfromlargemammals(includinghumans),whereasimmaturestages feed on small rodents.Methods & Materials: With the aim of shedding light on theecologyofthisemergingdisease,weconductedfieldstudiesatsitesof the Paraná River delta, which consisted of systematic collectionofticksandbloodsamplesfromrodents(Fig.2)andcattle,andalsoquestingticksfromthevegetation.Samplingsessionswerecarriedout monthly during 2011 and 2012 at 16 points that differed intheir exposure to cattle and vegetation type (natural or implantedforest).Results: Prevalence of infection in adult questing ticks washigh (20.4%). Interestingly, the distribution of R. parkeri infectionintensity observed in A. triste ticks was distinctly bimodal, withapproximately 60% of the infected ticks presenting high rickettsialloads(Fig.3).Questingticksweremorefrequentlyfoundinnaturalgrasslands than in implanted forests, and prevalence of infectionwere greater in those from grasslands (26%) than in forestedareas(8.3%).ThedominantrodentspecieswereAkodonazaraeandOxymycterus rufus. In both, the seroprevalence to R. parkeri wasgreater in those captured in grasslands than in implanted forests.The presence of cattle had a significant positive effect on the burdensofticksonrodentsandtheabundanceofquestingticksinthevegetation. Most cattle (90%) were seropositive, and the seasonalityof the titres of antibodies againstR.parkeri matched that of thetick infestation on cattle.Conclusion: The risk of human exposure to R. parkeri infectedticks in the Paraná River delta is high. Our results suggest thatthe silvopastoral activities that are on the rise in the region affectthe dynamics of infection of R. parkeri. Cattle appear to favour theoccurrence of the pathogen, whereas forestation seems to reduce it.