Intestinal parasitoses among Wayampi Indians from French Guiana.

Intestinal parasitism and its epidemiological characteristics were studied in an isolated Amerindian population from Upper Oyapock (French Guiana) that has retained its traditional social and cultural specificities. This population consisted of 138 Wayampi Indians, 68 adults and 70 children (below the age of 15 years), with a sex ratio (M/F) of 0.86, spread over the four villages of the community of Trois Sauts, corresponding to more than two thirds of the population recorded as inhabiting the sector in the last census (375 inhabitants). Fecal examination combined the direct examination of fresh feces with the quantitative techniques of Kato-Katz method, Baermann and MIF staining. Overall, 92% of the subjects were found to have intestinal parasites, 85% if only direct examination of fresh stools was taken into account. Fourteen species of human parasite were identified: seven protozoa and seven helminths. We observed in particular 1) a high frequency of hookworm infection due to Necator americanus. Over 50% of subjects were affected, with a range of 25% to 75% according to the village, but with only moderate parasite loads; 2) a high level of parasitism by E. histolytica/E. dispar (17%), Stongyloides stercoralis (16%) and Hymenolepis nana (18%); 3) a lower level of parasitism by Ascaris lumbricoides and very low levels (almost absent) of Trichiuris trichiura; 4) the absence of Schistosoma and fluke eggs. With the exception of H. nana, which was more frequent in children than in adults, there was no significant difference in the level of parasitism according to sex and age. Although the Wayampi of French Guiana are French citizens and consequently have quite high incomes and ready access to clinics and medicines, intestinal parasites are far from under control in this population. A lack of fecal hygiene and the habit of walking barefoot are widespread in the unchanging Amazonian environment and contribute to this phenomenon.

Serologic survey of Toxoplasma gondii in noncarnivorous free-ranging neotropical mammals in French Guiana.

The aim of this study was to determine the frequency of Toxoplasma infection in wild mammals, particularly noncarnivorous species, and to identify possible sources of infection for humans. A serological study was conducted that included 310 animals representing 10 species of terrestrial mammals from the same region (primary tropical rain forest inhabited by humans). Toxoplasmosis was diagnosed using a direct agglutination test using formalin-treated Toxoplasma gondii. The prevalence of antibodies for toxoplasmosis differed greatly between species and ranged from 0% to 62%. The seroprevalence of toxoplasmosis was zero or very low for tree-dwelling animals, which included sloth, porcupine, and howler monkey. Conversely, the prevalence of infection was 46-62% among granivores, insectivores, and burrowing animals, such as peccary, paca, and armadillo. We conclude that wild mammals in French Guiana constitute a reservoir of T. gondii parasites. Given the absence of domestic cats from the forest, noncarnivorous species may be infected by the ingestion of oocysts that are eliminated into the soil or water in the stools of wild cats and then dispersed.

Periodic infectivity of Plasmodium gametocytes to the vector. A review.

Frank Hawking, in 1966 postulated that in synchronous malaria infections, the brief period of infectivity of gametocytes was timed to occur when the vector bites. Since this early work, numerous studies had contributed to confirm and explain this phenomenon with bird, rodent and primate Plasmodium. Data on the periodic production of gametocytes, the duration of their maturation, the effect of the schizogony on the infectivity and the circadian bioavailability of gametocytes provide some more informations on the periodic Plasmodium gametocyte infectivity to the vector. This paper is intended to be a review of contributions on the "Hawking phenomenon" and to summarize the principal causal hypotheses. The conclusion stresses the practical consequences for experimental studies and epidemiological surveys.

Linear and multiple antigen peptides containing defined T and B epitopes of the Plasmodium yoelii circumsporozoite protein: antibody-mediated protection and boosting by sporozoite infection.

We previously reported the identification of a T cell epitope in the N-terminal part of the circumsporozoite protein (CSP) of Plasmodium yoelii yoelii (Pyy). CD4+ T cell clones derived from mice immunized with a 21-mer peptide (amino acids 59-79, referred to as Py1) containing this epitope confer complete protection after passive transfer in mice. These clones proliferate in vitro in the presence of a 13-mer peptide (amino acids 59-71, referred to as Py1T). This shorter peptide was found to behave as a Th epitope in vivo, allowing overcoming of the genetic restriction for production of anti-repeat antibodies in BALB/c mice, when cross-linked to three (QGPGAP) repeats of the Pyy CSP. In this study, we report protection in BALB/c mice, against a challenge with Pyy sporozoites after immunization with linear and multiple antigen peptides containing Py1T as T epitope and three repeats QGPGAP (Py3) as B epitope. Multiple antigen peptide (MAP4-Py1T-Py3)-induced immunity was shown to be more effective than immunity induced by the linear form of the conjugate (Py1T-Py3), protecting against challenges with higher numbers of sporozoites. In both cases, levels of anti-repeat antibodies were strongly correlated with anti-parasite antibodies and protection. When tested in vitro, sera from mice immunized with the protective constructs strongly inhibited Pyy liver stages, while lymph node T cells displayed no cytotoxicity. In vivo, depletion of CD4+ or CD8+ T cells did not affect protection. Furthermore, MAP4-Py1T-Py3-immunized mice were not protected against a challenge with P. yoelii nigeriensis sporozoites, a parasite which has the same Py1T sequence but differs from Pyy in its repeated sequence. These results demonstrate that anti-repeat antibodies raised by immunization with the linear or the MAP form are exclusively responsible for the protection. Furthermore, this antibody response is boosted by a sporozoite challenge, allowing protection against a second challenge.

Immunization with the malaria heat shock like protein hsp70-1 enhances transmission to the mosquito.

Mosquitoes fed on mice infected with Plasmodium yoelii after an immunization with the i72 recombinant form of the heat shock protein hsp70-1 developed significantly more oocysts than mosquitoes fed on controls. This effect was due to a marked increase in the relative numbers of gametocytes during the early stages of infection. A comparison of blood-induced and sporozoite-initiated infection showed that these gametocytes were derived from merozoites released from the liver. The stimulus for increased gametocyte production is unknown but is likely to be linked with antibody-dependent cellular cytotoxicity and associated cytokine responses.

The role of reactive nitrogen intermediates in modulation of gametocyte infectivity of rodent malaria parasites.

Direct feeding of Anopheles stephensi mosquitoes on mice infected with Plasmodium vinckei petteri showed that, during the periods of schizogony in the blood, the infectivity of gametocytes was markedly reduced. This could be prevented by prior injection of the L-arginine analogue, Nw-nitro-L-arginine (NwNLA) showing that the altered infectivity was due to reactive nitrogen intermediates (RNI). Similar effects on transmission of P. yoelii nigeriensis were demonstrated in vitro by membrane feeding of the mosquitoes. The in vitro reduction in infectivity could be reversed by injecting the L-arginine analogue either into the infected mouse donor of serum, or into the membrane feeding chamber. Elevated levels of TNF and IL-6 were demonstrated during the course of infection but did not correlate well with nitrogen radical activity. Similarly, direct measurements of NO2- and NO3- did not reflect the nitrogen radical activity revealed by addition of the specific L-arginine analogue.