Isolation and Identification of Cultivable Aerobic Pathogenic Bacteria from Ticks of Cattle in Central Ethiopia
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Date
2021
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Addis Ababa University
Abstract
Ticks are well-known vectors of a variety of intracellular tick-borne pathogens associated with tick-borne diseases worldwide (TBD). There is, however, a scarcity of precise and up-to-date comprehensive information on cultivable aerobic pathogenic bacteria from ticks of cattle from Ethiopia. A cross-sectional study was conducted from November 2020 to July 2021 with the objectives to isolate and identify cultivable aerobic pathogenic bacteria from ticks infesting cattle in central Ethiopia, namely, Ada’a, Lome and, Ezha districts. All ticks used to study pathogenic bacteria were morphologically identified to species level under a stereomicroscope using standard taxonomic keys. During the study period, a total of 205 adult live ticks belonging to eight species, namely, Hyalomma truncatum (N=50; 24.4 %), Amblyomma variegatum (N=41; 20%), Amblyomma cohaerens (N=40; 19.5%), Rhipicephalus decoloratus (N=33; 16.1%), Hyalomma rufipes (N=29; 14.1%), Rhipicephalus evertsi (N=7; 3.4%), Amblyomma gemma (N=4; 1.9%), and Rhipicephalus pulchellus (N=1; 0.5%) were identified in decreasing order and collected for bacteriological examination. Bacterial identification was performed by using multiple biochemical tests and API-20E strips. Results of the study showed that out of the total of 205 ticks studied for the presence of bacteria, 107 (52.2%) ticks were positive and 98 (47.8%) ticks were found negative for bacterial isolation and a total of 107 isolates of different bacterial pathogen were identified from all the study areas. Out of the total of 107 bacterial isolates recorded, a total of 5 species of aerobic pathogenic bacteria were identified including, (N=39; 36.5%) Citrobacter freundii, (N=34; 31.8%) Escherichia coli, (N=18; 16.2%) Staphylococcus aureus, (N=8; 7.5%) Proteus mirabilis, and (N=8; 7.5%) Morganella morganii. Statistically significant differences between study districts as well as species of ticks with the isolation rates of the pathogenic bacteria were observed. In vitro efficacy evaluation of the most commonly used antibiotics demonstrated that majority of the cultivable aerobic pathogenic bacteria detected in ticks collected from cattle were susceptible to chloramphenicol, streptomycin, and gentamicin but resistance against the action of bacitracin, penicillin, and clindamycin was recorded on the disk diffusion test method. In conclusion, the high isolation rate of pathogenic bacteria in ticks collected from cattle in the current study most likely indicates that ticks play an active role in environmental contamination and increase the likelihood of pathogenic bacteria transmission to their hosts.
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Tick species, pathogenic bacteria, Cattle, Ada’a, Lome, Ezha, Ethiopia