[Experimental studies on the effects in helminthic infection, with special reference to the gonadectomy of the host].

INTRODUCTION

Concerning the influences of the host's hormone in helminthic infection, Solomon(1963) reported that castrated hamsters were less susceptible to Nippostrongylus brasiliensis infection than the sham-operated or normal control groups, and Addis(1946) demonstrated that testosterone in the male host was necessary for normal growth of Hymenolepis diminuta and the egg productive ability was also effected by the hormone. Beck(1950, 1952) noted a significant reduction in egg production in castrated rats infected by a single worm. Egg production of a single worm in gonadectomized or thyroidectomized hamsters was found to be lower than the control group (Landt 1954, 1955). Dobson(1964) reported that male lambs were more susceptible to Oesophagostomum columbianum infection, harbouring more and larger worms and producing fewer nodules than females, but gonadectomy removed these differences by increasing the susceptibility and worm growth in the female lambs. Thyroidectomy did not affect host resistance, as measured by nodule numbers, but did increase adult worm survial, partcularly in female host. Solomon(1964) found that the mean recovery of adult worms from gonadectomized or normal hamsters given 20 mg testosterone propionate intramuscularly at 8 and 16 hour prior to infection and necropsied on the 9th day of infection, was nearly 50% that from sham or normal animals was apporximately 10%; and that from gonadectomized animals was only 3%. Campbell and Melcher(1940), Haam and Rosenfeld(1942), Sadun(1948, 1951), Haley (1958 a, b), Mathies(1959 a, b) and Dobson(1961 a, b), noted that estrogen increased the resistnace of the host against helminthic infection, while testosterone had a little or no effect. There were many studies on the effects of parasite infection in cases of host sex hormone imbalance but there are many unknown points as yet. In the present study, the author studied the infectiousness of helminths in castrated or in sex hormone-administrated hosts. MATERIALS AND METHODS: 1) 51 mature rats and 30 immature rats were divided into 10 groups for the former and 6 groups for the latter. 51,000 of hookworm(Ancylostoma caninum) filariform larvae were given to 51 gonadectomized rats by subcutaneous injection. The rats were sacrifeced 7 days after the infection and the larvae which had migrated to muscle, liver and lung were collected by Baermann's method. Thirty rats, given sex hormone, were infected with 100 filariform larvae of Ancylostoma caninum for each rat orally and the larvae were collected from the liver, muscle, lung and small intestine 72 hours after the infection. After calculation of the number of larvae a statistical method was applied for the singnificance of the difference. 2) Gonadectomized rats and control rats inoculated with Capillaria hepatica were sacrificed 5 weeks after infection. The adult worms were collected from the liver and were calculated. Four dogs, including one with oophorectomy, one castrated and two controls, were sacrificed 7 days after infection with 100 filariform larvae of Ancylostoma caninum to each and calculation of the number of larvae from the small intestines was carried out. 3) A castrated adult dog and one control dog(sham-operation) were infected orally with 500 A.caninum larvae each and the other two dogs were given 1,000 larvae each orally. The egg productivity was checked every five days by Stoll's egg counting method from three weeks after the infection was initated. A certain number of the hormones influenced adult worm from the castrated host were placed in vitro for the extensive examination fo egg productivity. RESULT: 1)No significant difference was noted in canine hookworm infection due to hormone influence between the control group and the gonadectomized rats which were sacrificed 17 days after gonadectomy and 7 days after the infection. However in the rats which were infected 20 days after oophorectomy a significant difference was thought to be present in this group(176 +/- 12.9 larvae/rat) compared with the control group (138 +/- 21.2 larvae/rat). On /rat). On the other hand, in the castrated group the number of larvae (138 ± 37.1 larvae/rat) was less than that in the control group (208 ± 43.4 larvae/rat). In the estrogen-injected male and female groups, there were no difference compared to the control, but the testosterone-injected groups of males and females showed more susceptibility to infection by A. caninum than in the control group. 2)The Capillaria hepatica infection to the castracted host showed no significant difference between the gonadectomized and the control group. (oophorectomy; 214 ± 28.0), castration; 250 ± 36.5 and control; 191 ± 58.2 and 270 ± 30.1 adults/rat). 3)Concerning the influence of the host's sex hormone on egg production of canine hookworm, there was a significantly decreased egg production in castrated dogs(6,578 ± 664.0 egg per gram) compared to the control dogs(9,711 ± 1,322.3 egg per gram). The same results were observed in vitro test. CONCLUSION: 1)In the host, the susceptibility to hookworm infection was reduced in castrated rats, while oophorectomy group had a little or no effect. 2)In the favorable or unfavorable hosts, testosterone gave the tendency of increasing susceptibility of the host to infection, while estrogen did a little or no effect.