Congenital trichinellosis in experimentally infected mice

The present study aimed at allocating the time during pregnancy at which transplacental transmission of Trichinella spiralis (T. spiralis) larvae took place. Swiss albino mice were infected at different durations of pregnancy; five days before mating, on gestation day zero and five days after mating. Furthermore, to study the effect of immunosuppression on transplacental transmission, half of the experimental mice were immunosuppressed using cyclophosphamide drug (Endoxan). The percentage of infected uteri, embryos and placentas and the mean larval count were calculated on day 8 post infection (PI). Moreover, the percentage of infected offspring and the mean larval count in their muscles were estimated on day 30 PI. The results of the present study revealed that, transplacental transmission of T. spiralis could occur in offspring of mice when their mothers are infected before or after pregnancy. This was documented by the presence of larvae in the muscles of offspring. However, the rate of this transmission increased when the mothers are infected at late pregnancy whether they were immunosuppressed or not. The administration of the immunosuppressive drug whether before or after pregnancy increased the rate of infection and the mean larval count in both uteri of mothers and muscles of their offspring. A higher percentage of abortion was demonstrated in females infected before mating in different studied groups.

[Preliminary study on congenital transmission of Trichinella spiralis in mice]

OBJECTIVE

To study congenital transmission of Trichinella spiralis in mice and observe the protection of anti-Trichinella antibodies from the infected dams to challenge infection.

METHODS

According to the gestation (fertilization), the Kunming mice were divided into two groups: the infected group after gestation and the gestated group after infection. New-born mice were cut into small pieces to separate the larvae within 1 day after birth. One-day-old offspring born to normal dams were nursed by the infected dams, slaughtered after 21 days and examined for the larvae. Serum anti-Trichinella antibody level in offspring born to the infected dams was assayed by ELISA at different time after birth, and its immune protection against challenge infection was studied.

RESULTS

Out of 6 offspring born to the dams infected at 7 days after fertilization, two were found to be infected. Among other female mice which were first infected with T. spiralis and then gestated, only the offspring born to the dams fertilized at 8 and 22 days after infection were found to be infected, the infection rate of offspring was 20% (2/10) and 25%(2/8) respectively. All larvae recovered from the young were non-encapsulated. The cross-fostering experiment showed that none of 30 offspring born to normal dams were found to be infected. The serum antibody positive rate in 27 offspring born to the infected dams at 1,7,24, and 40 days after birth was 100%, 100%, 77.8% and 14.8%, respectively. The worm reduction rate in the offspring 40 days after birth was 62.0% after challenge infection. The worm reduction rate in mice in which sera from the offspring born to the infected dams were passively transferred was 55.7%, there was a significant difference (P<0.01) compared to the control group.

CONCLUSION

A transplacental transmission of T. spiralis is revealed in mice. Anti-Trichinella antibodies from the infected dams may partially protect the young from challenge infection.

Congenital trichinellosis in the rat

57 female rats were divided into four groups according to age and gestation. Trichinella spiralis infection was induced by feeding the rats with rat muscle containing about 10000 larvae per gram. The mating and sacrificing of females were done differently for each group. New-born rats were examined by direct trichinoscopy and by peptic digestion of muscle. We found that larvae of T. spiralis which entered the uterus of the pregnant females can pass to the foetus. It was impossible to specify the time when larvae crossed the placenta, but this crossing is made only by those larvae which did not settle and encyst in the striated muscles. The mobilisation of the encysted larvae from skeletal muscles was not demonstrated.