There may be a reduction in red cells to one million per c.mm. within a few days. Normoblasts are abundant and megaloblasts may be observed in the more severe cases. The anaemia is intense and 20% to 40% of cases die within two or three weeks. A severe anaemia in which the blood picture is that of pernicious anaemia may accompany infections with the Balantidium coli.
Blackwater fever may produce a fall in red cells almost as marked as in Oroya fever.
Sprue shows a slowly progressive anaemia which in the later stages of the disease may become extreme, going down to one million, with a fairly high color index.
Ancylostomiasis is along with malaria the disease to be first thought of in connection with anaemia. The splenic enlargement of malaria should be thought of, although the view has recently been advanced that the spleen may be enlarged in hookworm disease.
In advanced cases of hookworm disease, showing a picture of profound anaemia, there may be so few worms present that the method of making diagnosis by finding ova may be unsuccessful. I have seen a case of typical aplastic pernicious anaemia, confirmed by autopsy, undoubtedly following a vicious cycle set up by the hookworm infection, in which scarcely a worm was to be found in searching the intestines.
Kala-azar gives a marked anaemia with an earthy color of the skin. The leucopenia and splenic enlargement are characteristic and the finding of parasites confirmatory.
Malta fever is usually followed by a moderate anaemia.
The helminthic infections, besides hookworm disease, are always to be thought of in the presence of anaemia. Very important among these are rectal and vesical schistosomiasis as well as that from the Japanese schistosome, together with liver and lung fluke disease. Even the ordinary round-worm, Ascaris lumbricoides, is to be thought of in a tropical anaemia.
Cases of anaemia, in which no other demonstrable cause has been noted, have been thought to be due to trichocephaliasis.