First isolation of Rickettsia amblyommatis from Amblyomma mixtum in Colombia

BACKGROUND

Rickettsiae are obligate intracellular Gram-negative bacteria that are the causative agent of rickettsioses and are spread to vertebrate hosts by arthropods. There are no previous reports of isolation of Rickettsia amblyommatis for Colombia.

METHODS

A convenience sampling was executed in three departments in Colombia for direct collection of adult ticks on domestic animals or over vegetation. Ticks were screened for the presence of Rickettsia spp. by real-time polymerase chain reaction (qPCR) amplifying the citrate synthase gene (gltA), and the positive sample was processed for isolation and further molecular characterization by conventional PCR. The absolute and relative frequencies were calculated for several tick species variables. All products from conventional PCR were further purified and sequenced by the Sanger technique. Representative sequences of 18 Rickettsia species were downloaded from GenBank. Consensus phylogenetic trees were constructed for the gltA, ompB, ompA, and htrA genes with 1000 replicates, calculating bootstrap values through the maximum likelihood method and the generalized time reversible substitution model in the MEGA 7.0 software program.

RESULTS

One female Amblyomma mixtum collected on vegetation was amplified by qPCR (gltA), indicating a frequency of 1.6% (1/61) for Rickettsia spp.

INFECTION

Sequence analysis of a rickettsial isolate from this tick in BLASTn showed 100% identity with gltA (340 base pairs [bp]), 99.87% for ompB (782 bp), 98.99% for htrA (497 bp), and 100% for ompA (488 bp) to R. amblyommatis. Concatenated phylogenetic analysis confirmed these findings indicating that the isolate is grouped with other sequences of Amblyomma cajennense complex from Panama and Brazil within the R. amblyommatis clade.

CONCLUSIONS

This paper describes the isolation and early molecular identification of a R. amblyommatis strain from A. mixtum in Colombia.

Presence of two species of the Amblyomma cajennense complex (Acari: Ixodidae) and probable zones of sympatry in northwestern Colombia

The A. cajennense tick complex has been thought to be the main vector of Rickettsia rickettsii in Central and South America. Studies in Colombia have determined the presence of species A. patinoi and A. mixtum of the A. cajennense complex, but it is unknown which species of this complex exist in northwestern Colombia. Our aim was to identify the species of the A. cajennense complex that are present in northwestern Colombia. We sampled ticks of A. cajennense sensu lato infesting equids. Females identified according to the morphology of their genital pore were selected for genetic confirmation. Specimens from each locality were selected to perform molecular and genetic analysis. Specimens were analyzed from five departments (Antioquia, Bolívar, Córdoba, Magdalena, and Sucre). Morphologically 65 specimens were identified as A. patinoi and 5 as A. mixtum. Molecular analysis allowed to confirm the morphological identification of 27 specimens. In this study A. patinoi was widely distributed in the departments of Antioquia, Bolívar, and Córdoba with allopatric and sympatric distribution in some places. These two species in the region could have unexpected effects on the epidemiology of rickettsiosis.

Human Rickettsiosis Caused by Rickettsia parkeri Strain Atlantic Rainforest, Urabá, Colombia

We describe the clinical, serologic, and molecular findings of a new human rickettsiosis in Colombia. Antibodies against Rickettsia spp. were detected. PCR showed amplification of genes for R. parkeri strain Atlantic Rainforest. This new rickettsiosis of minor virulence could explain some of the undifferentiated acute febrile diseases in Colombia.

A Cluster of Cases of Rocky Mountain Spotted Fever in an Area Of Colombia Not Known to be Endemic for This Disease

Rocky Mountain spotted fever (RMSF) has been reported in Colombia since 1937. Most recent outbreaks were in 2006-2008, followed by the absence of recognized cases. This report describes new clinical cases of RMSF and epidemiologic investigations. Medical records were reviewed, and fieldwork, serological and molecular diagnostic testing, and bacterial isolation were performed. Fever, hypotension, abdominal discomfort, and rash accompanied by thrombocytopenia and leukopenia were the most characteristic manifestations. Two convalescent sera from the index case and sera from two dogs revealed high anti-spotted fever group Rickettsia antibody titers. Rickettsia rickettsii was isolated from case 4. Cases 2 and 3 were identified by epidemiological connection with the index case. Thus, a new cluster of cases of RMSF was identified in Antioquia, Colombia, with the occurrence of fatal cases, which indicates the active circulation of the bacteria and a potential risk for the population.

Infection by Rickettsia felis in Ctenocephalides felis felis Fleas from North of Colombia

Background: Rickettsia felis is an emergent Rickettsial agent whose main vector is Ctenocephalides felis, but ticks, mites and lice are also infected. We aimed to search for molecular evidence of Rickettsia spp. in fleas collected from dogs and wild rodents (Heteromys anomalous) from three villages of Córdoba and Antioquia provinces (Northern of Colombia), where outbreaks of rickettsioses have occurred, and discuss the possible role of fleas on endem­ic/enzootic regions for rickettsia. Methods: During 2010 and 2012, 649 Ctenocephalides felis felis and 24 Pulex irritans fleas were removed from dogs and wild rodents (Heteromys anomalous), respectively, in 3 locations from Córdoba and Antioquia provinces (Colombia). These fleas were tested into pools for Rickettsial infection by PCR, targeting gltA, ompB, and ompA Rickettsial genes. Results: Almost 20% (30/153) of C. felis felis pools contained Rickettsial DNA. The fragments of ompB gene showed high identity values between sequences from Necocli and Los Cordobas with R. felis strain from Senegal (100% and 99.7% respectively) and all were highly related by phylogenetic analyses. Rickettsial DNA in pools of P. irritans was not detected. Conclusion: Our findings highlighted the endemicity of the infection by R. felis in fleas from northern of Colombia and showed the likely importance of dogs as hosts of C. felis felis fleas and their potential role as reservoirs of R. felis.

Infection by Rickettsia felis in Ctenocephalides felis felis Fleas from North of Colombia

BACKGROUND

Rickettsia felis is an emergent Rickettsial agent whose main vector is Ctenocephalides felis, but ticks, mites and lice are also infected. We aimed to search for molecular evidence of Rickettsia spp. in fleas collected from dogs and wild rodents (Heteromys anomalous) from three villages of Córdoba and Antioquia provinces (Northern of Colombia), where outbreaks of rickettsioses have occurred, and discuss the possible role of fleas on endemic/enzootic regions for rickettsia.

METHODS

During 2010 and 2012, 649 Ctenocephalides felis felis and 24 Pulex irritans fleas were removed from dogs and wild rodents (Heteromys anomalous), respectively, in 3 locations from Córdoba and Antioquia provinces (Colombia). These fleas were tested into pools for Rickettsial infection by PCR, targeting gltA, ompB, and ompA Rickettsial genes.

RESULTS

Almost 20% (30/153) of C. felis felis pools contained Rickettsial DNA. The fragments of ompB gene showed high identity values between sequences from Necocli and Los Cordobas with R. felis strain from Senegal (100% and 99.7% respectively) and all were highly related by phylogenetic analyses. Rickettsial DNA in pools of P. irritans was not detected.

CONCLUSION

Our findings highlighted the endemicity of the infection by R. felis in fleas from northern of Colombia and showed the likely importance of dogs as hosts of C. felis felis fleas and their potential role as reservoirs of R. felis.

Wild and domestic animals likely involved in rickettsial endemic zones of Northwestern Colombia

Between 2006 and 2008, three outbreaks of human rickettsiosis occurred in Northwestern Colombia (municipalities of Necoclí, Los Córdobas and Turbo), with case fatality rates between 27% and 54%. The aim of this study was to determine previous exposure of wild and domestic animals to spotted fever group (SFG) rickettsiae through serological tests, to detect rickettsial evidence in their ectoparasites, and to analyze their possible role in the epidemiology of rickettsial diseases in this zone of the country. A cross-sectional association study was performed from 2010 to 2011. Blood and ectoparasite samples were collected from domestic animals and small mammals. A statistically significant association (p<0.05) between seropositive animals and the study zones was observed. A total of 2937 ticks, 672 fleas and 74 lice were collected and tested in pools by PCR. The minimum infection rate (MIR) of the positive pools was 5% in ticks, 4% in fleas, and 0% in lice. Phylogenetic analyses showed circulation of three 4.Rickettsia species: R. felis in fleas, and R. bellii and Rickettsia sp. strain Atlantic rainforest, both in Amblyomma ovale ticks. In conclusion, this study demonstrated the occurrence of SFG rickettsiae in domestic, synanthropic and wild animals, and suggests the use of equines and canines as good sentinels of infection, in the study zone. We speculate that a transmission cycle exist involving rodents in the areas where these outbreaks have occurred. Tomes' spiny rats (Proechimys semispinosus) and common opossums (Didelphis marsupialis) could be good candidates as amplifier hosts for SFG rickettsiae in enzootic/endemic zones.

Human prevalence of the spotted fever group (SFG) rickettsiae in endemic zones of Northwestern Colombia

In February 2006, an outbreak of human rickettsiosis occurred in the municipality of Necoclí Colombia, with 35% of lethality. This episode was, followed by two more, one in the municipality of Los Cordobas in 2007 with a 54% of lethality and the other one in the municipality of Turbo in 2008 with 27% of lethality. The aim of this study was to perform serological tests in healthy persons to determine the seroprevalence of antibodies against spotted fever group (SFG) rickettsiae and develop a survey to study some infection risk-related factors. A cross-sectional study was performed in 2011 and 2012. A blood sample and survey of associated factors was performed in healthy persons. A prevalence of 32%-41% was found in healthy people. From the multivariate analysis, we found that people living more than 16 years in these sites had a 79% higher risk of being seropositive and a 46% higher risk when they reported having birds in their houses if the variable of having a horse was included in the model. In conclusion, this study shows endemicity of at least one spotted fever group Rickettsia in the study zone.