Preliminary Report on Observations on the Development of Ova of Pig and Human Ascaris under Natural Conditions, and Studies of Factors Influencing Development

Abstract

State laboratory reports of Alabama since 1924 show a very low infestation with Ascaris among the general population, it being less than 0.2 per cent in the lower coastal plain and approximating 3 per cent in the northern counties. Special surveys (Smillie and Augustine; Caldwell) tend to corroborate these findings. Surveys in Florida (Kerr, 1926) and the findings of the Rockefeller Sanitary Commission (1914) and the state laboratories of Georgia and South Carolina likewise indicate a low Ascaris infestation in those states. On the other hand, ascariasis constitutes a public health problem in Tennessee, North Carolina, Kentucky, and Virginia, being most prevalent in the mountain regions. In both south Alabama and west North Carolina, however, infestation among pigs approaches 50 per cent (Caldwell). In search for an explanation of this distribution, various observations were made in 1926 and 1927. To make these studies possible it was necessary to isolate ova from soils. Briefly, the method devised makes use of (1) antiformin solution to release the ova, (2) sugar solution of high specific gravity to float up the ova, and (3) a small vial to remove them from the surface. Differential counts of the varying stages of development-undeveloped, morula (early, moderate, and late), tadpole, motile, and disintegrated-in 200 to 500 ova give in a sense a quantitatively accurate picture of conditions.