Emerging Spotted Fever Rickettsioses in the United States

Area of Science:

• Veterinary Infectious Diseases
• Emerging Infectious Diseases
• Rickettsial Diseases

Background:

• Spotted fever rickettsioses are significant emerging infectious diseases globally.
• Rocky Mountain Spotted Fever (RMSF), caused by Rickettsia rickettsii, presents as acute febrile illness in dogs.
• Early-stage canine infection may yield false-negative PCR and serology due to low pathogen load.

Purpose of the Study:

• To emphasize the importance of prompt doxycycline therapy in suspected RMSF cases in dogs.
• To highlight diagnostic challenges and strategies for Rickettsia rickettsii infections in canines.
• To underscore the role of dogs as sentinels for human exposure to spotted fever group rickettsiae.

Main Methods:

• Clinical suspicion-guided empirical doxycycline treatment initiation.
• Utilizing a combination of PCR and serologic testing for diagnosis.
• Serial testing, including repeat PCR on pre-antimicrobial samples and convalescent serology for seroconversion.

Main Results:

• Timely antimicrobial therapy significantly improves prognosis in dogs with RMSF.
• Diagnostic confirmation can be challenging in the acute phase of illness.
• Dogs serve as important sentinels, indicating potential human exposure risks.

Conclusions:

• Veterinarians must initiate doxycycline treatment based on clinical suspicion, even with negative initial tests.
• Integrated diagnostic approaches, including repeat and convalescent testing, aid in confirming Rickettsia rickettsii infections.
• Awareness of emerging spotted fever group rickettsiae is vital for veterinary professionals to protect both animal and human health.