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Changes in blood serum constituents and hematologic values in Macaca mulatta with Rocky Mountain spotted fever
Abstract:
Forty-seven male Macaca mulatta, 3 to 4 kg weight, were inoculated intravenously or subcutaneously with various doses of yolk sac-grown Rickettsia rickettsii. Thirty-four macaques became febrile and exhibited signs of infection ranging from transient illness with a few days of fever to severe illness with subsequent death. The rash appeared more frequently in the macaques inoculated subcutaneously. Febrile macaques that survived had leukocytosis, with concomitant neutrophilia. Febrile macaques that died had, in addition, marked terminal leukopenia and thrombocytopenia. Packed cell volume of all febrile macaques decreased. In almost all of the febrile macaques, there were increased serum urea nitrogen, glutamic-oxaloacetic transaminase, and lactate dehydrogenase and decreased total serum protein and amylase concentrations. A few febrile macaques had increased bilirubin values and decreased sodium, chloride, phosphorus, and alkaline phosphatase concentrations. Changes did not occur in serum glucose, potassium, calcium, and glutamic-pyruvic transaminase values. The experimental form of Rocky Mountain spotted fever in the macaque provides a subhuman primate model for studying the pathophysiology of this disease.
Insights
Rickettsia rickettsii infection in macaques causes fever and varied illness severity. This study details the physiological changes observed in this Rocky Mountain spotted fever model.
Area of Science:
- Veterinary Medicine
- Infectious Diseases
- Primate Models
Background:
- Rocky Mountain spotted fever (RMSF) is a severe tick-borne illness caused by Rickettsia rickettsii.
- Understanding the pathophysiology of RMSF is crucial for developing effective treatments.
Purpose of the Study:
- To establish and characterize a non-human primate model of Rocky Mountain spotted fever using Macaca mulatta.
- To investigate the clinical and physiological manifestations of Rickettsia rickettsii infection in macaques.
Main Methods:
- Forty-seven male macaques were inoculated with Rickettsia rickettsii via intravenous or subcutaneous routes.
- Clinical signs, including fever and rash, were monitored.
- Hematological and serum biochemical parameters were analyzed in febrile macaques.
Main Results:
- Thirty-four macaques developed fever and signs of infection, with varying severity.
- Subcutaneous inoculation led to more frequent rash development.
- Febrile macaques showed leukocytosis, leukopenia, thrombocytopenia, decreased packed cell volume, and altered serum chemistry (e.g., elevated BUN, AST, LDH; decreased total protein, amylase).
Conclusions:
- The experimental infection in macaques successfully mimics key aspects of human Rocky Mountain spotted fever.
- This macaque model is valuable for studying RMSF pathophysiology and evaluating potential therapies.