Fatal Rocky Mountain Spotted Fever along the United States–Mexico Border, 2013–2016

Drexler, Naomi A.; Yaglom, Hayley; Casal, Mariana; Fierro, Maria; Kriner, Paula; Murphy, Brian P.; Kjemtrup, Anne; Paddock, Christopher D.

doi:10.3201/eid2310.170309

Cited by 35 publications

(41 citation statements)

References 17 publications

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“…Rocky Mountain spotted fever (RMSF) is an emerging public health concern in the United States and near the US–Mexico border, a site that recently saw several fatal cases of RMSF. In all cases, infection was caused by R. rickettsii [45] . Nevertheless, there have been suspected cases of RMSF where the causative agent, R. rickettsii, was not identified in the local tick population.…”

Section: Discussionmentioning

confidence: 99%

Isolation of Rickettsia amblyommatis in HUVEC line

Santibáñez

Portillo

Palomar

et al. 2018

New Microbes and New Infections

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Rickettsia amblyommatis, formerly named Rickettsia amblyommii and ‘Candidatus Rickettsia amblyommii’ is an intracellular bacterium belonging to the spotted fever group Rickettsia. It is highly prevalent in Amblyomma americanum and in other Amblyomma spp. throughout the Western Hemisphere. R. amblyommatis has been cultivated in chicken fibroblast, primary embryonated chicken eggs, Vero cells and arthropod-derived cells. Because of the affinity of rickettsiae to invade vascular endothelial cells, we tried to isolate R. amblyommatis from a nymph of Amblyomma cajennense s.l. collected in Saltillo (Coahulia, Mexico) using human umbilical vein endothelial cells (HUVEC). One tick half was analysed by ompA PCR and was found to be positive for R. amblyommatis. The other half was selected for in vitro culture of Rickettsia spp. It was triturated in 1 mL of endothelial cell growth medium with 1% antibiotic–antimycotic solution, and the homogenate was inoculated into a HUVEC line. Culture was maintained at 33°C in endothelial cell growth medium plus 2 mM l-glutamine and 2% fetal calf serum, with 5% CO2. The medium was changed weekly. Culture was checked by Gimenez stain for Rickettsia-like intracellular organisms. After 48 days of incubation, Rickettsia-like organisms were observed in HUVEC. PCR assays and sequencing of ompA gene in the culture suspension showed 100% identity with R. amblyommatis. This isolate was successfully established in HUVEC, and it has been deposited in the collection of the Center of Rickettsioses and Arthropod-Borne Diseases, Infectious Diseases Department, Hospital San Pedro–Center of Biomedical Research from La Rioja, Logroño, Spain. The HUVEC line is a useful tool for the isolation of R. amblyommatis.

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Section: Discussionmentioning

confidence: 99%

Isolation of Rickettsia amblyommatis in HUVEC line

Santibáñez

Portillo

Palomar

et al. 2018

New Microbes and New Infections

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“…The disease has been nationally notifiable in the United States since 1920, with most cases reported from south Atlantic (North Carolina) and south-central states (Arkansas, Missouri, Oklahoma and Tennessee) ( ). RMSF is a notifiable disease in Mexico as well, with epidemics in the past decade concentrated along the United States-Mexico border region [ 75 ].…”

Section: Tick-borne Rickettsiae (In Alphabetical Order)mentioning

confidence: 99%

Suspected and Confirmed Vector-Borne Rickettsioses of North America Associated with Human Diseases

Yoshimizu

Billeter

2018

TropicalMed

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The identification of pathogenic rickettsial agents has expanded over the last two decades. In North America, the majority of human cases are caused by tick-borne rickettsioses but rickettsiae transmitted by lice, fleas, mites and other arthropods are also responsible for clinical disease. Symptoms are generally nonspecific or mimic other infectious diseases; therefore, diagnosis and treatment may be delayed. While infection with most rickettsioses is relatively mild, delayed diagnosis and treatment may lead to increased morbidity and mortality. This review will discuss the ecology, epidemiology and public health importance of suspected and confirmed vector-transmitted Rickettsia species of North America associated with human diseases.

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“…RMSF and other SFGR diseases may represent a significant health threat in border states of the United States. Fatal human cases associated with travel to Mexico have been reported, including cases in California (Drexler et al, ), and it is common for residents near the border to travel with pets to Mexico, sometimes to seek veterinary care. While RMSF is not at this time endemic in southern California, brown dog ticks are abundant: for example, approximately one‐third of shelter dogs were infested with this tick in Imperial County, in the south‐east corner of California just north of the US–Mexico border (Fritz et al, ).…”

Section: Introductionmentioning

confidence: 99%

Spotted fever group rickettsiae canine serosurveillance near the US–Mexico border in California

Estrada¹,

Balagot

Fierro³

et al. 2019

Zoonoses and Public Health

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Background: Dogs are vulnerable to pathogens transmitted by brown dog ticks. An epidemic of Rocky Mountain spotted fever (RMSF) is underway in Mexicali, aMexican city bordering California affecting people and dogs; several human cases have been reported in California residents who travelled to Mexico. To evaluate risks of RMSF, we conducted seroprevalence surveys in Imperial County in 2016 and 2017 using dogs as sentinels.Methods: Blood was collected from 752 dogs and was tested for antibodies against R. rickettsii, E. canis and A. phagocytophilum (as a proxy for A. platys). Samples were considered seropositive to spotted fever group rickettsia (SFGR) if the R. rickettsia titre was ≥1:64 and seropositive to E. canis and A. phagocytophilum if the titre was ≥1:32. Owners provided information on dog age, exposure risks, health status and tick prevention. We assessed associations between SFGR seropositivity and driving distance to the nearest US-Mexico border crossing station, whether proximity to a border crossing increased likelihood of taking dogs across the border, and whether distance to the border was associated with seropositivity. Logistic regression was performed to assess relationships between the titre classes and other predictor variables.Results: 12.2% of dogs were seropositive against SFGR. Dogs close to the border were significantly more likely to be taken across the border and to be seropositive.Risk factors that increased seropositivity included owners seeing ticks on the dog (OR = 1.9), being an adult dog, travel to Mexico (OR = 3.0) and living in a rural area (OR = 4.0). There was statistically significant co-exposure to SFGR and Anaplasma spp. Conclusion: Surveillance for brown dog tick-vectored pathogens can help identify dogs and people at risk for RMSF. Tick prevention, particularly in dogs, and surveillance of tick-borne pathogens can help prevent the spread of rickettsioses and other diseases in this dynamic border region. K E Y W O R D S border disease, canine sentinel, Rocky Mountain spotted fever | 149 ESTRADA ET Al.

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Fatal Rocky Mountain Spotted Fever along the United States–Mexico Border, 2013–2016

Abstract: Although these cases are uncommon, early recognition and prompt initiation of appropriate treatment are vital for averting severe illness and death.

Cited by 35 publications

References 17 publications

Isolation of Rickettsia amblyommatis in HUVEC line

Isolation of Rickettsia amblyommatis in HUVEC line

Suspected and Confirmed Vector-Borne Rickettsioses of North America Associated with Human Diseases

Spotted fever group rickettsiae canine serosurveillance near the US–Mexico border in California

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