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Boophilus microplus: cellular responses to larval attachment and their relationship to host resistance
Abstract:
The histology of early feeding lesions of the cattle tick B. microplus has been studied using 32P labelled larvae to standardize the duration of attachment. Critical studies were made on 3-h lesions in six separate experiments on different groups of British breed animals. Each group consisted of three animals--one previously unexposed to ticks, one of high resistance and one of low resistance. The degree of mast cell disruption, eosinophil concentration and degranulation, and the extent of epidermal vesiculation were all significantly greater at the site of attachment on highly resistant hosts. In previously unexposed animals there was no mobilization of eosinophils nor mast cell breakdown and no epidermal vesiculation. Possible immune mechanisms producing mast cell disruption and the infiltration and concentration of eosinophils are suggested, and the effect of eosinophil degranulation on larval attachment and feeding is discussed.
Insights
Cattle tick feeding lesions show significant differences in mast cell disruption and eosinophil activity in resistant hosts. These immune responses are absent in unexposed animals, impacting tick attachment.
Area of Science:
- Veterinary Entomology
- Immunology
- Histopathology
Background:
- Bovine tick infestations, particularly by Rhipicephalus (Boophilus) microplus, cause significant economic losses in cattle.
- Understanding the host-parasite interactions at the lesion site is crucial for developing effective control strategies.
- Early feeding stages are critical for tick establishment and subsequent infestation.
Purpose of the Study:
- To histologically examine early feeding lesions of Rhipicephalus (Boophilus) microplus in cattle.
- To compare lesion development and host immune responses across different resistance levels.
- To investigate the role of mast cells and eosinophils in tick resistance.
Main Methods:
- Utilized 32P-labeled Rhipicephalus (Boophilus) microplus larvae to standardize attachment duration (3 hours).
- Examined lesion histology in British breed cattle with varying tick resistance (unexposed, low, high).
- Quantified mast cell disruption, eosinophil concentration and degranulation, and epidermal vesiculation.
Main Results:
- Highly resistant hosts exhibited significantly greater mast cell disruption, eosinophil infiltration/degranulation, and epidermal vesiculation at 3-hour lesions.
- Previously unexposed animals showed no eosinophil mobilization, mast cell breakdown, or epidermal vesiculation.
- Differences in immune cell activity correlated with host resistance levels.
Conclusions:
- Host resistance to Rhipicephalus (Boophilus) microplus involves specific immune responses at the early feeding site.
- Mast cell disruption and eosinophil activity appear to be key components of the host defense mechanism.
- Further research is needed to elucidate the precise immune mechanisms and their impact on tick feeding and attachment.