Further observations on Strongyloides westeri dermatitis: recovery of larvae from soil and bedding, and survival in treated sites.

This study investigates the relationship between the occurrence of Strongyloides westeri dermatitis in two horses and the larvae of S. westeri present in the environment. The research findings suggest that the larva thrives in moist warm weather and low pH soils or sawdust.

Introduction

The research was triggered by observations of horses undergoing episodes of extreme discomfort and hyperactivity, leading to physical conditions such as swelling and lesions. These conditions were suspected to be linked to the filariform larvae of the Strongyloides westeri parasite, which were found in the soil and sawdust where the horses were kept.

Methodology and Findings

• The investigation involved culturing larvae from the horses’ environment and subsequent analysis.
• It was found the larvae could be cultured from low pH soil (between 4.5-5.8) however, none were present in neutral or alkaline soils.
• Despite varying pH range, the larvae were also found in sawdust, indicating a mild resistance to acidity or alkalinity.
• Following the episodes of frenzy, clinical physical conditions such as swelling and lesions were observed on the legs of the horses. Swelling was observed within 2 days of an attack in one horse, while skin lesions erupted 3-4 days after an attack in the second horse. The swelling persisted for 2-3 weeks.

Conclusions

• The researchers concluded that S. westeri dermatitis in the horses was likely caused by a percutaneous invasion (through the skin) of filariform larvae of S. westeri.
• Furthermore, the environmental conditions necessary for the survival and resistance of desiccation (drying out) of the larvae were identified as being moist warm weather and low pH soils or sawdust.

The research provides useful insights into the life cycle and environmental requirements of S. westeri larvae, providing potential for future prevention of related dermatitis via targeted environmental management.