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Molecular epidemiological updates on spotted fever rickettsioses in animal species and their hard ticks settling Egyptian desert


Nesreen A.T. Allam , Faragallah M. El Moghazy , Sayed M.M. Abdel-Baky

Abstract

Hard ticks are ectoparasites that infest animals prompting severe transmittable infections. It is aimed to identify then characterize spotted fever group (SFG) rickettsioses in ticks and their hosts from smallholdings and Bedouin communities in Egypt desert including; North West Coast, Western Desert Oasis, South East Coast, Suez Canal region and Sinai. The 5223 adult ixodid ticks were collected from 270 ruminants; 110 camels, 120 sheep, and 40 cattle, and examined seasonally (4 times/year) from June 2014 to July 2016. The statistical analysis of the infestation density of all species on each host was highly significant, but was not significant between different localities. The infestation density on cattle was higher (59 %) than camels (33.6%) and sheep (7.4%) regarding all 14 species of ticks identified. The adult stages (♀ & ♂) of Boophilus annulatus, Hylomma dromedarii, and Rhipicephalus sanguineus were the highest in density on cattle, camels, and sheep recording 56%, 24.7% and 5.9%, respectively. Nucleotides similarities of ticks’ 18S rDNA and 16S rDNA genome markers were 99-100% against GenBank records, which confirmed species’ identification by morphological keys. Molecular screening for rickettsiosis was carried out by multi-genes sequencing technology; where 16S rDNA was the primary target. Positive PCRs were then typed into Rickettsiae species level by the ompA and gltA genes alignments. Hylomma dromedarii ticks were the most susceptible to Rickettsia (35.7%) than other tick species. The prevalent localities for ticks’ rickettsiosis were Shalateen, Dakhla Oasis, Siwa Oasis, El Salloum, and Marsa Matrouh recording 17.8%, 11.8%, 11.2%, 9.6% and 9.2%, respectively. Regarding the animal hosts, the SFG incidence was higher in camels than sheep recorded 64.7% and 29.4%, respectively. The hosts’ rickettsiosis incidence recording 14.7%, 13.7%, 12.8%, 11.8% and 10.8% was in Bir El abed, Shalateen, Wadi Gharandal, Al hasna, Marsa Matruh and El Salloum, respectively. Additionally, Rh. sanguineus (dogs’ ticks) had high incidence for rickettsioses; collected from all the infested animal species investigated during the study. Hence, the Rh. sanguineus PCR-positive rickettsia collected from cattle (5.9%) is an incidence never recorded; therefore, it needs experimental studies before being accepted. Rickettsia sibirica mongolitimonae-like was detected for the first time within Egyptian livestock’s population. Rickettsia aeschlimannii-like, R. africa-likee, in addition to, unclassified Rickettsia-like were additionally detected within the investigated specimens. Still, the pathological impacts of freely moving rodents and migratory birds are underestimated in epidemiology of such exotic zoonosis. Moreover, the role of additional vector (rodents’ soft ticks) and/or reservoirs (desert reptiles) has not been clearly identified yet; it can be considered as a hypothesis that needs more comprehensive and profound studies to improve the physicians’, as well as, veterinarians’ differential diagnosis of tick-borne fever due to rickettsioses in Egypt.



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