Ascaris suum infection in calves. II. Circulating and marrow eosinophil responses.

An increment in the number of circulating eosinophils occurred between the 11th and 14th days after infection with Ascaris suum and this increase was generally greater after a challenge infection. Continual infection with small numbers of A. suum eggs over prolonged periods resulted in circulating eosinophil levels which fluctuated and were dose-dependent. The per cent marrow eosinophils always increased after a primary infection and a greater increase usually followed a challenge infection. The maximum increment of marrow eosinophils occurred between the tenth and 12th days and preceded the rise in circulating eosinophils by 36 hours. Antihistamine therapy did not alter eosinophil responses to A. suum. Circulating eosinophilia was not usually reflected by drastic changes in differential white cell counts. However, an increase in total white cell count often followed infection with A. suum and frequently parallelled changes in eosinophil counts. Hemoglobin and P.C.V. values remained within normal limits in A. summ infected calves.