It is well known that the principal manifestation of hookworm infestation is anemia. A lot of reports concerning the anemia-inducing factors have been announced with the three principal theories; blood loss, dysfunction of hematopoietic organ and nutritional disturbances, mainly due to the adult worm infestation.
Miyagawa (1943) and Morishita (1951) reported that anemia appeared even 3-4 days after infection in case of massive number of larvae. Concerning anemia-inducing factor in early stage of hookworm, infestation, it has been recognized that the lance also produce toxic material which cause anemia, though few were reported on its experimental data(Kitayama: 1950, Iwata 1960).
The present study is aimed at confirmation of the anemia-inducing factors in the early stage of hookworm infestation.
1. Beginning Time of Hookworm Anemia.
Time and intensity of anemia due to hookworm infection were exanined in proper host.
In case of heavy infection (10,000 larvae/kg), the hematological blood value (red blood cell count, hemoglobin, hematocrit) began to decrease 3 days after infection and the animal hardly survived for 10 days with marked anemia at the end of the life.
On the other hand the milder infection group and the control group showed no significant change.
Serum bilirubin was tested with a result of no noticeable change before and after infection in each group. Histopathological findings showed generalized pneumonitis and hemorrhagic foci in lungs, slight inflammation in intestine, slight congestion in liver, but proliferation in bone marrow. Spleen, heart, kidney showed negative findings.
From above facts it is suggestive that hookworm anemia could start in very early stage (even 3 days after infection) and such anemia is hardly thought to be induced from hemolysis or dysfunction of the hematopoietic organ-bone marrow.
2. Blood Figure of Hookworm Anemia in improper Host.
Influence of the migrating hookworm larvae was examined with improper host.
Human hookworm, Ancylostoma duodenale was given to dogs cutaneously, orally or intravenously.
In heavy infection group (10,000 larvae/kg) the blood value began to decrease three days after infection as same as in case of proper host (Ancylostoma caninum to dog) but recovered soon without marked manifestation of anemia. Very few of the larvae became adult and produced eggs as long as three months, though the number of adult worm was too negligible to cause anemia.
The results showed that even in improper host, the bookworm larvae could decrease the blood vague hematologically, even though it was temporary.
3. Anemia Inducing Substance.
In order to examine the anemia-inducing substance which might be produced by the larvae, metabolic products of the larvae and the dead larvae were inoculated to puppies.
Dead larvae of Ancylostoma caninum were inoculated to four puppies in massive amount (0.7-0.5 million larvae) and two of them showed anemia and died within three weeks. On histopathological examination, however, the bone marrow of the dogs showed proliferation. The other two puppies survived well and showed no particular hematological change as the other groups; inoculation of the milder doses (0.2 million of larvae), inoculation of metabolic product of the larvae, injection of emulsion of Toxocara cams, and injection of simple normal saline solution.
Therefore it is hard to consider that hookworm larvae produce any anemia-inducing substance which might prohibit the hematopoiesis.
The red cell fragility test was done with rabbits infected with Ancylostoma caninum (10,000 larvae/kg) in order to examine any slight hemolysis in the early stage of hookworm infection.
In osmotic fragility test of red blood cells, no particular manifestation of hemolysis was observed after the infection to compare the control group.
It is considered that hemolysis also is not responsible for the induction of the anemia in this case at all.
4. Beginning of Blood Sucking.
Herrick (1928) announced that Ancylostoma caninum produced eggs within 15-26 days after infection. Morishita (1955) reported that a mouth capsule of the larva was formed 8 days after infection and he found epithelial cells of intestine of the host in it. However, he reported that blood sucking was started 12 days after
In case of skin infection of Ancylostoma caninum to puppies in the present experiments, the larvae were found exclusively in lungs on the 3rd day of infection and scarcely in the intestinal canal. But on the 4th day a lot of larvae were found also in intestinal canal. On the 9th day, teeth were developed in the mouth capsule of the worm, and copious bleeding was seen in the intestinal canal of the host.
In autoradiographic examination it was found that the larva taken from intestine of the host on the 6th day of infection, which did not have teeth yet, showed a manifestlungs of blood ingestion as in adult worm. However, in the 3rd-day larvae
taken from lungs or intestinal cannal no blood material was detected.
5. Changes of Circulating Red Cells at Early Stage of Hookworm Infection.
In both proper and improper host, he hematological blood value showed a decrease in the early stage of infection. Because of hyperplastic findings of the bone marrow, the decrease of the blood value was considered mainly due to the loss of circulating red cells entity, and red cell survival change was tested by way of Chromium 51.
Rabbits were infected with Ancylostoma caninum. The milder infection group (2,000 larvae/Kg) showed nearly the same tendency as that of control group. On the contrary, the heavier infection group (10,000 larvae/Kg) showed a decrease in circulating red cells on the 3rd day of infection but recovered soon to its own
normal level. X-ray findings showed generalized density in the lung field that might represent pneumonit is and hemorrhage.
The decrease of hematological blood figure in early stage of hook work infection is considered to be induced mainly due to the blood loss in the tissue damage, especially in lungs, during the larval migration. Then the blood loss is continued on account of the blood sucking of immature worm in the intestinal canal in case of the proper host.