The development and survival of Trichuris suis ova on pasture plots in the south of England.

Pasture plots in the south of England were contaminated each month throughout 1975 with pig faeces containing Trichuris suis ova. At regular intervals thereafter, soil samples were taken, the T suis ova extracted and their state of development noted. Depending on the time of year that the plots were contaminated, ova required between 62 and 90 weeks to complete their development to the infective stage. Little or no development occurred during winter. Once the infective stage was reached, the ova survived for at least two years. Samples taken from the plots at various depths demonstrated that T suis ova did not rapidly leach through the soil but were still available to grazing pigs up to two and a half years later. The early developmental stages of ova appeared to be more susceptible to desiccation than those that had developed to the blastula stage or beyond.