Thesis (Ph.D.) - Cairo University - Faculty of Veterinary Medicine - Department of Internal Medicine and Infectious Diseases

Rickettsioses have an epidemiological importance that includes pathogens, vectors, and hosts and have zoonotic importance. A total number of 461 blood samples of animals (200 dogs, 200 horses and 61 camels) were collected from three Egyptian provinces (Cairo, Giza and Sinai). In addition, 705 adult ticks were collected (601 ticks from dogs and 104 ticks from camels) including 9 nymphs, during a period extending from 2011 to 2014. The most important clinical signs were observed fever, anorexia, lethargy, anemia, enlargement of lymph node, ocular signs and emaciation. Meanwhile, the rest of animals were apparently healthy. Morphological identification of both male and female tick specimens by light microscope and scanning electron microscope revealed that 100% of tick-infested dogs were Rhipicephalus sanguineus while 91.9% of tick-infested camels were Hyalomma dromedarii. The blood film staining with Gimenez stain revealed that 3 (2 dogs and 1 horse) were positive for rickettsioses by finding of rickettsiae stained red inside granulocytes. While, hemolymph staining of tick specimens by gimenez stain showed that the prevalence rate was 11.89 % in Rh. sanguineus and 10.1 % in Hyalomma spp. OmpA and gltA genes amplification were performed to estimate the prevalence rate of Rickettsiae in animal hosts and their ticks which revealed that the infection rate was 18 % in dogs, 72 % in horses, 41 % in camels and 6.17 % in ticks. Moreover, the phylogenetic analyses of two genes (OmpA and gltA) and three intergenic spacers (mppA, dksA and rpmE) of Rickettsia species sequences were constructed based on clustal W multiple alignments using two methods UPGMA and NJ, and revealed a novel strain of Rickettsia africae in H. marginatum on camel from Sinai province

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