The association between weather, frenzied behaviour, percutaneous invasion by Stongyloides westeri larvae and Rhodococcus equi disease in foals

Abstract Episodes of frenzy lasting approximately 30 minutes were observed among horses confined to enclosures surfaced with sand or soil. The probability of sighting these episodes increased by a factor of three when within 24 hours there was 0.2mm or more of rain, a maximum air temperature between 16.7 – 26.6°and a soil temperature of 16.3 – 23.9°C at 30 cm. High egg counts of Strongyloides westeri appeared in faeces four to five days later and persisted for several days. Rhodococcus equi was recovered from all soil samples, and from the faeces of 76% of mares and 82% of foals. The youngest foal was five days old when the organism was isolated from rectal faeces. In contrast to the majority of reports, the lesions of R. equi in the foals were confined to limbs and peripheral lymph nodes. It is proposed that the percutaneous invasion of these foals by third stage larvae of S. westeri facilitated invasion of R. equi, and ubiquitous saprophytic opportunist pathogen.(2)