ARTICLE | doi:10.20944/preprints202204.0087.v1
Subject: Life Sciences, Microbiology Keywords: Rickettsia parkeri; Rhipicephalus sanguineus; dogs; tick-borne disease; rickettsiosis
Online: 11 April 2022 (03:37:16 CEST)
Of the documented tick-borne diseases infecting humans in Mexico, Rocky Mountain spotted fever (RMSF), caused by the gram-negative bacterium Rickettsia rickettsia, is responsible for most fatalities. Given recent evidence of brown dog tick, Rhipicephalus sanguineus sensu lato, as an emerging vector of human RMSF, we aimed to evaluate dogs and their ticks for rickettsiae infections as an initial step in assessing the establishment of this pathosystem in a poorly studied region of northeastern Mexico while evaluating the use of dogs as sentinels for transmission/human disease risk. We sampled owned dogs living in six disadvantaged neighborhoods of Reynosa, Northern Mexico to collect whole blood and ticks. Of 168 dogs assessed, tick infestation prevalence was 53%, comprised of exclusively R. sanguineus s. l. (n=2,170 ticks). Using PCR and sequencing, we identified an overall rickettsiae infection prevalence of 4.1% (n=12/292) in ticks, in which eight dogs harbored at least one infected tick. Rickettsiae infections included R. amblyommatis and R. parkeri, both of which are emerging human pathogens, as well as candidatus R. andeanae. This is the first documentation of pathogenic Rickettsia in R. sanguineus s.l. collected on dogs from northeastern Mexico. Domestic dog infestation with Rickettsia-infected ticks indicates ongoing transmission, thus humans are at risk for exposure and underscores the importance of public and veterinary health surveillance for these pathogens.
Subject: Medicine & Pharmacology, Veterinary Medicine Keywords: Coxiella burnetii; Rickettsia; Q fever; rickettsiosis; tick-borne pathogens
Online: 31 March 2020 (09:54:07 CEST)
Rickettsia and Coxiella burnetii are zoonotic tick-borne pathogens that can cause febrile illnesses with or without other symptoms in humans but may cause subclinical infections in animals. There are only a few reports on the occurrence of these pathogens in cattle and water buffaloes in Southeast Asia, including the Philippines. In this study, molecular detection of Rickettsia spp. and C. burnetii in the blood and Rhipicephalus (Boophilus) microplus ticks of cattle and water buffaloes from five provinces in Luzon Island of the Philippines was done. A total of 620 blood samples of cattle and water buffaloes and 206 tick samples were collected and subjected to DNA extraction. After successful amplification of control genes, nested PCR was performed to detect gltA of Rickettsia and com1 of C. burnetii. No samples were positive for Rickettsia while 10 (cattle – 7, water buffaloes - 3) or 1.6% of blood and 5 or 1.8% of tick samples were C. burnetii-positive. Sequence analysis of the positive amplicons showed 99-100% similarity to reported C. burnetii isolates. This molecular evidence on the occurrence of C. burnetii in Philippine ruminants and cattle ticks and its zoonotic nature should prompt further investigation and surveillance to facilitate its effective control.
ARTICLE | doi:10.20944/preprints201804.0141.v1
Subject: Life Sciences, Microbiology Keywords: scrub typhus; Orientia tsutsugamushi; Rickettsia; Rickettsiales; outer membrane protein A; Anaplasma
Online: 11 April 2018 (08:13:04 CEST)
Scrub typhus threatens one billion people in the Asia-Pacific area and cases have emerged outside this region. It is caused by infection with any of the multitude of strains of the bacterium, Orientia tsutsugamushi. A vaccine that affords heterologous protection and a commercially available molecular diagnostic assay are lacking. Herein, we determined that the nucleotide and translated amino acid sequences of outer membrane protein A (OmpA) are highly conserved among 51 O. tsutsugamushi isolates. Molecular modeling revealed the predicted tertiary structure of O. tsutsugamushi OmpA to be very similar to that of the phylogenetically related pathogen, Anaplasma phagocytophilum, including the location of a helix that contains residues functionally essential for A. phagocytophilum infection. PCR primers were developed that amplified ompA DNA from all O. tsutsugamushi strains, but not from negative control bacteria. Using these primers in quantitative real-time PCR enabled sensitive detection and quantitation of O. tsutsugamushi ompA DNA from organs of mice that had been experimentally infected with the Karp or Gilliam strains. The high degree of OmpA conservation among O. tsutsugamushi strains evidences its potential to serve as a molecular diagnostic target and justifies its consideration as a candidate for developing a broadly protective scrub typhus vaccine.
ARTICLE | doi:10.20944/preprints202106.0170.v1
Subject: Life Sciences, Microbiology Keywords: dromedary camels, ticks, heartwater, zoonosis, tick-borne pathogens, Anaplasma, Coxiella, Ehrlichia, Rickettsia
Online: 7 June 2021 (12:39:26 CEST)
Ticks and tick-borne pathogens (TBPs) are major constraints to camel health and production, yet epidemiological data on their diversity and impact on dromedary camels are limited. We sur-veyed the diversity of ticks and TBPs associated with camels and co-grazing sheep at 12 sites in Marsabit County, northern Kenya. We screened blood and ticks (858 pools) collected from 296 camels and 77 sheep for bacterial and protozoan TBPs by high-resolution melting analysis and sequencing of PCR products. Hyalomma (75.7%), Amblyomma (17.6%) and Rhipicephalus (6.7%) spp. ticks were morphologically identified and confirmed by molecular analyses. We detected TBP DNA in 80.1% of blood samples from 296 healthy camels. “Candidatus Anaplasma camelii”, “Candidatus Ehrlichia regneryi” and Coxiella burnetii were detected in both camels and associ-ated ticks, and Ehrlichia chaffeensis, Rickettsia africae, Rickettsia aeschlimannii and Coxiella endo-symbionts were detected in camel ticks. We also detected Ehrlichia ruminantium, responsible for heartwater disease in ruminants, in Amblyomma ticks infesting camels and sheep and in sheep blood, indicating its endemicity in Marsabit. Our findings also suggest that camels and/or the ticks infesting them are reservoirs of zoonotic Q fever (C. burnetii), ehrlichiosis (E. chaffeensis), and rickettsiosis (R. africae), which pose a public health threat to pastoralist communities.