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Spirochete from the rabbit tick, Haemaphysalis leporispalustris (Packard). I. Isolation and preliminary
Abstract:
An unidentified spirochete, referred to as the 277F agent, was isolated from Haemaphysalis leporispalustris ticks from two cottontail rabbits by inoculation of the tick suspension into embryonated chicken eggs. Because of its minute width (0.1 mu), the organism was difficult to see when stained by the Giemsa method, but was readily demonstrated by silver impregnation or fluorescent-antibody procedures. In dark-field microscopy, the spirochetes appeared uniformly and rather tightly coiled, and exhibited typical corkscrewlike motility. After yolk-sac inoculation, the agent was highly lethal for chick embryos and was recovered in large quantity from several embryonic tissues and fluids. It could also be maintained in nonfertile eggs and in an enriched liquid medium. This previously undescribed spirochete could pass through Berkefeld N but not Seitz EK filters. It was relatively resistant to heat and to penicillin or sulfadiazine, but was markedly inhibited by streptomycin, broad-spectrum antibiotics, and homologous neutralizing antiserum. Of several species of animals tested for susceptibility to this spirochete, only the snowshoe hare gave evidence of infection.
Insights
A novel spirochete, the 277F agent, was identified in ticks. This infectious agent proved lethal to chick embryos and infected snowshoe hares, indicating potential zoonotic implications.
Area of Science:
- Microbiology
- Parasitology
- Veterinary Science
Background:
- An unidentified spirochete, designated the 277F agent, was isolated from Haemaphysalis leporispalustris ticks.
- The spirochete's minute width (0.1 μm) made it challenging to visualize with standard staining methods.
Purpose of the Study:
- To characterize a previously undescribed spirochete isolated from ticks.
- To determine the pathogenicity and susceptibility of the agent.
Main Methods:
- Isolation via inoculation of tick suspensions into embryonated chicken eggs.
- Visualization using silver impregnation and fluorescent-antibody techniques.
- Filtration studies (Berkefeld N, Seitz EK) and antibiotic susceptibility testing.
Main Results:
- The 277F agent was highly lethal to chick embryos, with recovery from multiple embryonic tissues.
- Spirochetes exhibited characteristic corkscrew motility and were filterable through Berkefeld N filters.
- The agent showed resistance to heat, penicillin, and sulfadiazine, but was inhibited by streptomycin and specific antiserum.
- Only snowshoe hares demonstrated susceptibility among tested animal species.
Conclusions:
- The 277F agent represents a novel, pathogenic spirochete with specific host and environmental tolerances.
- Further research is warranted to understand its transmission dynamics and potential impact on animal health.