Annales de parasitologie humaine et comparee最新文献

A study was made on the survival of first larval stage of Neostrongylus linearis, from November 1990 to October 1991, under natural conditions in an inland locality in Galicia (North-West Spain). The faeces were obtained from a sheep naturally infected with this nematode. Once a month, faeces were placed on a 0.5 x 0.5 m plot, in natural conditions, until we had 12 deposits. Samplings were done weekly until there was no more faecal matter in the plots. Larval survival was determined using the Baermann migration technique, and we calculated the number of larvae per gram after the transformation of the weight of the faecal sample, in order to discard weight variations owing to climatic conditions. Over the whole period of this study, the percentages of larval survival in the faeces of the 12 deposits changed from the first week onwards. In those samples that were left in the pasture more than three weeks, survival was less than 50%. After the seventh week only very small numbers of active N. linearis larvae were obtained. We observed a positive influence of relative humidity on survival during the first week's presence of the faeces in the pasture. In the same way, a statistically significant negative correlation was proved between larval survival in faeces and temperatures during the first three weeks post-deposit.

The influence of nonspecific immunomodulation with Thymomodulin (a calf thymic extract with immunomodulatory activity) and hydrocortisone on the course and location of Cryptosporidium parvum infection in neonatal BALB/c mice (infected with 10(6) or 10(5) oocysts on day 7 of life) was studied using scanning electron microscopy of the inner surface of different parts of intestine. Daily peroral treatment of suckling mice with 20 mg/kg/day of Thymomodulin for 5 days before inoculation resulted in an earlier peak and earlier termination of cryptosporidial infection when compared with control infected mice. On the other hand, peroral administration of 25 mg/kg of hydrocortisone every second day led to the persistence of cryptosporidial infection in the ileum of immunosuppressed mice until the end of observation (day 15 post infection), whereas only transient infection was observed in the intestine of control infected mice. The location of infection was also altered in hydrocortisone--treated mice--the severe infection was observed in more proximal parts of the intestine (anterior and middle jejunum), whereas no cryptosporidia were found in these parts of the intestine in nontreated infected mice.

Several procedures were employed to try to specify the schizogonic cycle of Plasmodium yoelii nigeriensis. The Percoll-glucose gradient technique for concentrating the very young stages (rings and young trophozoites), allowing a very precise follow up of the development of the parasitaemia during the first schizogonic cycles. A method for studying the prepatencies, providing an approximation of the number of merozoites inoculated. A comparison between the numbers of merozoites present in the blood, after--firstly simple dilutions in saline, revealing the total number of merozoites,--secondly dilutions in saline after a passage of a few hours in the organism of a mouse, revealing the number of latent merozoites. It was shown that the infection, during the first two cycles, varies according to the time of inoculation. In all cases the increase of the parasitaemia occurred mainly from 00:01 to 06:00. This increase of parasitaemia in mice inoculated with the Percoll concentrated parasites was significantly high during the first cycle in mice inoculated at 06:00 and 09:00 and during the second cycle in those inoculated at 12:00, 15:00 and 18:00. However, differences were rapidly compensated and parasitaemias became comparable at the 3rd or 4th cycle when they ceased to be dependent on the time of inoculation.