More importantly it reflects a lag phase in the response of the erythropoietic system to counterbalance this heavy loss of red cells. During this lag phase then erythhropoietic system is mobilising to produce red cells in sufficient quantities to replace those being lost. This time lag may be very important under conditions of heavy infections since they may produce peracute infections with sudden deaths due to fatal blood loss before the erythropoietic system has expanded sufficiently to cope. The second phase of anemia is associated with the early post-patent phase of the infection. Strongyle-type eggs can now be detected in feces indicating a mature worm population.
Blood losses are at a maximum as shown by loss of labelled red cells into the g.i tract.
However, this maximum loss is associated with a stable PCV on a plateau indicating that erythropoieses is sufficient to manufacture red cells at the rate they are being lost. However, the situation is far from rosy. Normal physiological turnover. Sheep infected with 2-3,000 H. contortus Additional 1 billion cells being lost. 15gm Hb and 50mg Fe.