Molecular investigation on transstadial/transovarial transmission of Hepatozoon canis in Rhipicephalus sanguineus sensu lato ticks

Abstract

ABSTRACT To investigate the possibility of transovarial and transstadial transmission of Hepatozoon canis, a total of 953 Rhipicehlalus sanguineus sensu lato ticks at different stages were collected from 231 stray dogs housed at Blue cross, and 10 dogs presented at small animal clinics. The engorged nymphs collected from the cracks and crevices of Blue cross were allowed to moult in the laboratory. The ticks collected from the host and moulted ticks were pooled according to their sex and feeding status as fed, unfed males and females. Each tick was dissected individually and examined microscopically, then pooled as H. canis positive and negative. Microscopic examination of the 953 ticks revealed H. canis oocysts in 228 (89.76%) unfed adult males and females which moulted from the nymphs collected from cracks and crevices. Positivity of 74% was observed in unfed females while all unfed males (100%) were positive. Amongst the 213 fed males, 174 (81.69%) were positive, while only 210 (43.20%) of the 486 fed females were positive. No oocyst was detected from ticks collected from dogs presented to clinics. The occurrence of H. canis DNA in the tick was confirmed by PCR assay based on the amplification of 666 bp fragment of partial 18S rRNA gene. Amplification was observed in pooled samples collected from Blue cross, whereas no amplification was observed in ticks collected from dogs presented to clinics. The DNA samples from tick larvae did not show amplification, which indicated that H. canis is not transmitted transovarially.