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Dirofilaria immitis: the moulting of the infective larva in vitro
Abstract:
A number of in vitro culture systems were tested for their ability to support the development of Dirofilaria immitis infective larvae to the fourth larval stage. In cultures of medium ML-15 containing a feeder layer of Dog Sarcoma (DS) cells larvae successfully moulted and showed a small but significant increase in length. Ultrastructural observations demonstrated that the fourth-stage cuticle was synthesized in vitro and in some larvae was fully formed by 60 hours of culture. The hypodermis of moulting larvae contained numerous multi-vesicular bodies. It is concluded that the moult in vitro is a true moult and not an atypical response of the larvae to the conditions of culture.
Insights
Researchers developed an in vitro culture system to study Dirofilaria immitis (heartworm) larvae. This system successfully supported larval development to the fourth stage, confirming a true moult occurred.
Area of Science:
- Veterinary Parasitology
- Invertebrate Zoology
- Cell Biology
Background:
- Dirofilaria immitis, the canine heartworm, poses a significant threat to animal health.
- Understanding larval development is crucial for developing effective control strategies.
- Previous in vitro culture systems have shown limitations in supporting complete larval moulting.
Purpose of the Study:
- To evaluate the efficacy of different in vitro culture systems for Dirofilaria immitis infective larvae.
- To determine if larvae can successfully moult to the fourth stage in a controlled laboratory setting.
- To characterize the ultrastructural changes associated with in vitro moulting.
Main Methods:
- Testing multiple in vitro culture media and feeder cell layers.
- Utilizing Dog Sarcoma (DS) cells in ML-15 medium for larval culture.
- Employing light and electron microscopy to observe larval morphology and cuticle development.
Main Results:
- Larvae cultured in ML-15 medium with DS cells successfully moulted to the fourth stage.
- A significant, albeit small, increase in larval length was observed.
- Ultrastructural analysis confirmed the synthesis and formation of the fourth-stage cuticle within 60 hours.
- Multi-vesicular bodies were identified in the hypodermis of moulting larvae.
Conclusions:
- The developed in vitro system effectively supports the moult of Dirofilaria immitis larvae to the fourth stage.
- The observed moult is a genuine biological process, not an artifact of the culture conditions.
- This system provides a valuable tool for studying Dirofilaria immitis development and potentially for drug screening.
