Comparative strategies and success of sympatric and allopatric Fasciola hepatica infecting Galba truncatula of different susceptibilities.

Allopatric infections of French Galba truncatula with an Argentinean isolate of Fasciola hepatica were carried out to determine the infectivity of foreign miracidia in three snail populations differing by their susceptibility to French miracidia (two highly and one poorly susceptible populations). Sympatric infections of G. truncatula with French miracidia were used as controls. Compared to sympatric infections of G. truncatula, snail survival at day 30 post-infection in allopatric groups was significantly lower in a highly susceptible population and significantly greater in the other two. Prevalence in snails infected with the allopatric isolate was significantly lower (16.4-34.5 % instead of 58.6-72.1 %), whereas their patent period was significantly longer (a mean of 69.9-85.9 days instead of 6.4-20.7 days). The mean number of metacercariae was also higher in allopatric groups (236.5-897.3 per cercariae-shedding snail instead of 70.7-222.1). Owing to longer patent periods, the Argentinean isolate of F. hepatica was less pathogenic for these snails. The lower prevalence of infection, the longer patent period and the higher number of metacercariae noted in allopatric groups might be the consequence of an adaptive mechanism used by this digenean introduced to the New World to infect new populations of unusual intermediate hosts.

Variations in local adaptation of allopatric Fasciola hepatica to French Galba truncatula in relation to parasite origin.

Two French populations of Galba truncatula were subjected to experimental infections with Egyptian and French isolates of Fasciola sp. miracidia, originating from cattle and sheep, to compare characteristics of snail infections in allopatric and sympatric groups. All sampled Egyptian isolates were identified as Fasciola hepatica using microsatellite markers. Compared to snails infected with French miracidia, snail survival at day 30 post-exposure was significantly greater in the Egyptian groups, while prevalence of infection was significantly lower (in an Egyptian group infected with cattle-derived miracidia) or did not show any significant differences in the other three cases. The total number of metacercariae was significantly higher in the four Egyptian groups. However, snail population and the mammalian origin of F. hepatica had also a significant effect on this parameter. The dissection of snail cadavers showed a significantly higher number of free rediae in the Egyptian groups, even if snail population also had a significant effect on the redial burden. Both Egyptian isolates of F. hepatica could easily develop in French snails, causing a low mortality in snails and inducing a metacercarial production higher than that noted in sympatric infections. However, the mammalian origin of F. hepatica eggs and the quality of snail populations as intermediate hosts had to be taken into account for studying local adaptation in reason of their effects on this process.

Lymnaea neotropica and Lymnaea viatrix, potential intermediate hosts for Fascioloides magna.

Experimental infections of two South American lymnaeid populations with Fascioloides magna were carried out to determine whether these snails may sustain larval development of this digenean and, if so, to quantify their potential for cercarial production. The reference group was a French population of Galba truncatula infected and raised according to the same protocol. According to the internal transcribed sequence (ITS)-1 segment of their genomic rDNA, these South American populations were identified as Lymnaea neotropica (origin, Argentina) and Lymnaea viatrix var. ventricosa (origin, Uruguay). In the snail groups followed for cercarial shedding, longer prepatent periods and lower numbers of shed cercariae were noted in South American lymnaeids. In other snails dissected at day 65 post-exposure, the redial and cercarial burdens of F. magna found in the bodies of L. neotropica and L. v. ventricosa were significantly lower than those noted in G. truncatula. Compared to the total cercarial production noted in the dissected snails, the percentage of cercariae that exited from snails was 51.3% for G. truncatula, 32.2% for L. neotropica and 46.8% for L. v. ventricosa. The two South American species of snails can thus be considered as potential intermediate hosts of F. magna.

Intermediate snail hosts of French Fasciola hepatica: Lymnaea neotropica and Lymnaea viatrix are better hosts than local Galba truncatula.

Allopatric and sympatric infections of Lymnaea neotropica and Lymnaea viatrix var. ventricosa with Argentinean and French isolates of Fasciola hepatica were carried out to determine the capacity of these snails to produce metacercariae and to verify if this capacity changed with snail generation. The same process was also made with a French population of Galba truncatula known to be highly susceptible to French isolates of the parasite. In each lymnaeid species separately considered, the survival rate at day 30 post-exposure and prevalence of F. hepatica infection in the group infected with Argentinean miracidia were significantly greater than those recorded in the corresponding French one. Compared to infected G. truncatula, both South American lymnaeids had longer patent periods and produced a higher number of metacercariae. The highest infections were noted with L. v. ventricosa. In the three snail species, metacercarial production was more important with the Argentinean isolate of miracidia than with the French one. If three successive generations of L. v. ventricosa are exposed to the same French isolate of miracidia, cercarial production significantly increased from parents to the F2 generation, while the other characteristics of infection only showed insignificant variations. L. neotropica and L. v. ventricosa are better intermediate hosts for French F. hepatica than local G. truncatula. The numerical increase of shed cercariae in the F1 and F2 generations of L. v. ventricosa demonstrates a rapid adaptation of this species to the French isolate of the parasite.

[Sleeping sickness: end of the epidemic outbreak?]. / La maladie du sommeil, fin d'une épidémie ?

Sleeping sickness or human African trypanosomiasis is a parasitic disease transmitted by tsetse flies and therefore confined to its habitat, the central part of the African continent. Two disease forms are linked to two different parasites: T. b. gambiense and T. b. rhodesiense. Actual epidemiological data and precise and dynamic mapping of foci are in favor of a real decrease of the disease. Not all areas are under control and resurgence can still not be avoided from the remote areas where the disease is endemic. However, recent advances in knowledge in parasite genetics are giving hope of control. In 2009, for the first time since 50 years, less than 10,000 cases were declared to the World Health Organization. Clinical trials allowed revising some clinical concepts and linking them with parasite genetics: both disease forms can show variations from asymptomatic, chronic to acute and are linked to genetic differences in the host or the parasite. Parasitological diagnosis may be facilitated by the introduction of individual rapid tests and PCR-based field tests. Knowledge in mechanisms of brain invasion and screenings of inflammatory molecules allow new marker combinations for staging but they do not avoid lumbar puncture. Therapeutic options remain limited but there is hope to develop a new drug orally available in a near future.

Molecular identification of Fasciola spp. (Digenea: Fasciolidae) in Egypt.

A total of 134 Egyptian liver flukes were collected from different definitive hosts (cattle, sheep, and buffaloes) to identify them via the use of PCR-RFLP and sequence analysis of the first nuclear ribosomal internal transcribed spacer (ITS1). Specimens of F. hepatica from France, as well as F. gigantica from Cameroon were included in the study for comparison. PCR products of ITS1 were subjected for digestion by RsaI restriction enzyme and visualized on agarose gel. According to RFLP pattern, Egyptian flukes were allocated into two categories. The first was identical to that of French hepatica flukes to have a pattern of 360, 100, and 60 (bp) band size, whereas the second resembled to that of Cameroonian gigantica worms to have a profile of 360, 170, and 60 bp in size. Results of RFLP analysis were confirmed by sequence analysis of representative ITS1 amplicons. No hybrid forms were detected in the present study. Taken together, this study concluded that both species of Fasciola are present in Egypt, whereas the hybrid form may be not very common.

[Sleeping Sickness: A Cause of False Positive HIV Rapid Diagnostic Tests]. / Maladie du Sommeil: Une Cause de Faux Positifs des Tests de Diagnostic Rapide du VIH.

Approaching the mechanisms related to false positives HIV rapid diagnostic tests (RDT) in patients with sleeping sickness may help to improve the accuracy of screening for HIV infection in areas endemic for Human African trypanosomiasis (HAT).We report on a patient from Congo who was managed like an AIDS-associated meningoencephalitis, based on a false positive HIV RDT at admission, and eventually received a diagnosis of sleeping sickness. A further retrospective cohort study performed in patients with HAT shows that most of positive HIV RDT obtained prior to treatment for sleeping sickness are false positives. We found that half of them were cleared at the end of treatment course, suggesting an early clearance of some antibodies involved in cross-reactivity.A substantial clearance of HIV RDT false positives occurs during therapy for HAT. In areas where Elisa HIV tests are not readily available, repeating the HIV RDT at the end of therapy may help to identify roughly half of false positives.

[Criteria for diagnosis of the neurological stage of human African trypanosomiasis: update and perspectives]. / Marqueurs du stade neurologique de la trypanosomose humaine africaine: actualités et perspectives.

Sleeping sickness or human African trypanosomiasis (HAT) is due to parasite infection by a sanguicolous flagellate protozoan of the Trypanosoma brucei genus. The disease is classically divided into two stages, i.e., the hemolymphatic stage and the CNS stage. Disease staging is currently a major challenge for therapeutic decision-making. In the field, diagnosis is based solely on white blood cell (WBC) count and detection of the parasite in the patient's cerebrospinal fluid (CSF). This technique is unreliable and invasive. Numerous studies are now under way to adapt staging to field conditions and to develop a reliable, low-cost, non-invasive test. This article describes the mechanisms underlying CNS involvement during HAT and reviews the different techniques now being studied to simplify and improve diagnosis of the CNS stage.