The distribution of Parascaris equorum eggs in the soil profile of bare paddocks in some Norwegian studs.

Fifteen bare paddocks, which consisted of soil only and were located on 12 different studs, were examined for their content of Parascaris equorum eggs in the upper 15 cm of the soil profile. The paddocks were classified into three different groups according to the type of soil: clayey soil (A), morainic soil (B) and gravel or gravel-like sand (C). Soil profiles were collected down to a depth of 15 cm and were divided into three layers: 0-5 cm (D1), 5-10 cm (D2) and 10-15 (D3). The eggs in each layer were counted and identified as infective or noninfective eggs. The paddocks in group C, which had good drainage conditions, had significantly lower numbers of eggs in the whole profile and in D1 and D2 than the paddocks in groups A or B. Furthermore, there was a significantly higher proportion of the total egg count present in D3 in the group C paddocks. This may have been due to a higher degree of passive transportation of eggs down in the profile in the gravel or gravel-like sand. Even though there was a significantly higher proportion of infective eggs in the soil from the group C paddocks, the lower total numbers of eggs resulted in a lower total number of infective eggs in those paddocks. The study showed that the soil type was an important factor in determining the content of P. equorum eggs in the upper layer of the soil profile in bare paddocks and consequently for the potential infestation of horses with P. equorum.