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      Direct evidence of Rickettsia typhi infection in Rhipicephalus sanguineus ticks and their canine hosts

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          Murine typhus is a rickettsiosis caused by Rickettsia typhi, whose transmission is carried out by rat fleas in urban settlements as classically known, but it also has been related to cat fleas in a sub-urban alternative cycle that has been suggested by recent reports. These studies remarks that in addition to rats, other animals like cats, opossums and dogs could be implied in the transmission of Rickettsia typhi as infected fleas obtained from serologically positive animals have been detected in samples from endemic areas. In Mexico, the higher number of murine typhus cases have been detected in the Yucatan peninsula, which includes a great southeastern region of Mexico that shows ecologic characteristics similar to the sub-urban alternative cycle recently described in Texas and California at the United States. To find out which are the particular ecologic characteristics of murine typhus transmission in this region, we analyzed blood and Rhipicephalus sanguineus ticks obtained from domestic dogs by molecular approaches, demonstrating that both samples were infected by Rickettsia typhi. Following this, we obtained isolates that were analyzed by genetic sequencing to corroborate this infection in 100% of the analyzed samples. This evidence suggests for the first time that ticks and dogs could be actively participating in the transmission of murine typhus, in a role that requires further studies for its precise description.

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          Genotypic identification of rickettsiae and estimation of intraspecies sequence divergence for portions of two rickettsial genes.

          DNA sequences from specific genes, amplified by the polymerase chain reaction technique, were used as substrata for nonisotopic restriction endonuclease fragment length polymorphism differentiation of rickettsial species and genotypes. The products amplified using a single pair of oligonucleotide primers (derived from a rickettsial citrate synthase gene sequence) and cleaved with restriction endonucleases were used to differentiate almost all recognized species of rickettsiae. A second set of primers was used for differentiation of all recognized species of closely related spotted fever group rickettsiae. The procedure circumvents many technical obstacles previously associated with identification of rickettsial species. Multiple amplified DNA digest patterns were used to estimate the intraspecies nucleotide sequence divergence for the genes coding for rickettsial citrate synthase and a large antigen-coding gene of the spotted fever group rickettsiae. The estimated relationships deduced from these genotypic data correlate reasonably well with established rickettsial taxonomic schemes.
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            Murine typhus: an unrecognized suburban vectorborne disease.

             Van Ngo,  Rachel Civen (2008)
            Murine typhus, an acute febrile illness caused by Rickettsia typhi, is distributed worldwide. Mainly transmitted by the fleas of rodents, it is associated with cities and ports where urban rats (Rattus rattus and Rattus norvegicus) are abundant. In the United States, cases are concentrated in suburban areas of Texas and California. Contrary to the classic rat-flea-rat cycle, the most important reservoirs of infection in these areas are opossums and cats. The cat flea, Ctenocephalides felis, has been identified as the principal vector. In Texas, murine typhus cases occur in spring and summer, whereas, in California, cases have been documented in summer and fall. Most patients present with fever, and many have rash and headache. Serologic testing with the indirect immunofluorescence assay is the preferred diagnostic method. Doxycycline is the antibiotic of choice and has been shown to shorten the course of illness.
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                Author and article information

                Open Vet J
                Open Vet J
                Open Veterinary Journal
                Faculty of Veterinary Medicine, University of Tripoli and Libyan Authority for Research, Science and Technology (Tripoli, Libya )
                11 June 2017
                : 7
                : 2
                : 165-169
                Center of Research and Regional Studies Dr Hideyo Noguchi, Autonomous University of Yucatan. Av. Itzáes and 59th street, number490, Mérida, Yucatán. Postal code 97000, Mexico
                Author notes
                [* ] Corresponding Author: Karla Dzul-Rosado. Center of Research and Regional Studies Dr Hideyo Noguchi, Autonomous University of Yucatan, Mérida, Yucatán, Mexico. Tel: +52 (999) 9245809, 9245755. Email: karla.dzul@
                Copyright: © Open Veterinary Journal

                Open Veterinary Journal is licensed under a Creative Commons Attribution 4.0 International License.

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