Experimental infection of Salmonella Enteritidis by the poultry red mite, Dermanyssus gallinae

Dermanyssus gallinae is an important ectoparasite of laying hens in Europe and it is suspected of being a vector of pathogens. We carried out an in vitro study to evaluate the role of D. gallinae as a vector of Salmonella enterica subsp. enterica serotype Enteritidis. Two means of infecting the mite were tested: through the blood meal and after cuticular contact. Mites became carriers of Salmonella immediately after the infection with 29% and 53%, respectively, for oral route and cuticular contact. This percentage increased over time until it reached 95% (D7) and 80% (D14). The numerical identification of bacteria on the selective medium SM ID demonstrated the multiplication of Salmonella inside previously infected mites. In addition, transovarial passage as well as transstadial passage (from N1 to N2 stages) were demonstrated. Moreover, the observation of a negative effect of Salmonella on Dermanyssus oviposition was also observed. Finally, previously infected mites were able to contaminate the blood during the blood meal. Therefore, it appears that D. gallinae may act as a biological vector of S. Enteritidis under experimental conditions. It may represent a suitable environment for the development of Salmonella and could be an additional factor for the persistence of salmonellosis infection between successive flocks.