ABSTRACT
Human African trypanosomiasis is a parasitic infection caused by protozoa belonging to Trypanosoma brucei subspecies. The clinical evolution of this disease is complex and might be because of the parasite itself, as genetic diversity has been observed in T. brucei ssp. We investigated the relationship between the genetic diversity of trypanosomes and the diversity of clinical patterns in Côte d'Ivoire. We studied clinical sleeping sickness cases, and genetically analysed the trypanosomes isolated from these patients. An important genetic monomorphism among stocks isolated in Côte d'Ivoire was observed by using various markers: isoenzymes electrophoresis, random amplified polymorphism DNA and PCR of microsatellite sequences. At the same time, the diversity of clinical patterns and evolutions was confirmed by clinical analysis. The existence of an individual susceptibility to disease (human trypanotolerance) should be taken into account even if our genetic conclusions might be distorted because the isolation success rates were particularly poor. In fact, we observed that the isolation success rate varied significantly depending both on the focus of origin (P=0.0002) and on the ethnic group (P=0.0317) of the patient. Further investigations are required in order to study a possible selective impact of the use of the kit for in vitro isolation of trypanosomes as an isolation technique.
Subject(s)
Trypanosoma brucei gambiense/genetics , Trypanosomiasis, African/epidemiology , Trypanosomiasis, African/parasitology , Animals , Cote d'Ivoire/epidemiology , Disease Progression , Genetics, Population , Humans , Isoenzymes/genetics , Microsatellite Repeats/genetics , Phylogeny , Polymorphism, Genetic , Trypanosoma brucei gambiense/enzymology , Trypanosoma brucei gambiense/isolation & purificationABSTRACT
During a medical survey the sleeping sickness focus in Bonon, Ivory Coast, PCR with Trypanosoma brucei specific primers (TBR 1-2 from Parasitology 99 (1989) 57) was tested on DNA derived from blood samples. DNA purification using a chelating resin was performed either on whole blood or on the buffy coat prepared in two different ways. The preparation based on whole blood performed better than those using the buffy-coat. Using this first method, the sensitivity was 100% on parasitologically confirmed patients, and the specificity was 92%. However, problems of reproducibility of the technique were pointed out, particularly on samples from serologically positive but apparently aparasitemic individuals. It is suggested that the PCR could help in the diagnosis of Human African Trypanosomosis, but the use of other primers should be investigated.
Subject(s)
DNA, Protozoan/isolation & purification , Polymerase Chain Reaction/methods , Trypanosoma brucei gambiense , Trypanosomiasis, African/diagnosis , Animals , Cote d'Ivoire , Edetic Acid , Heparin , Humans , Sensitivity and SpecificityABSTRACT
Human African Trypanosomiasis is related to behavioural risk factors but complex interactions exist between (i) environmental and behavioural risk factors, (ii) vector and (iii) human host. Our aim was to investigate the interrelationships between previously analysed risk factors and the roles of age and time of exposure according to ethnic group and migration status. However, this descriptive and retrospective study is based on cases only (no controls) and our results must therefore be regarded as hypothesis-generating. Individuals originating from areas where sleeping sickness is absent and who settle in an endemic area seem to develop the disease after a shorter time of exposure than native subjects from endemic areas. Our results emphasise the complexity of vector-transmitted disease epidemiology, involving behavioural and/or environmental risk factors on the one hand, and more individual ones such as ageing, immunity and genetic background on the other hand.
Subject(s)
Environmental Exposure/adverse effects , Trypanosoma brucei gambiense , Trypanosomiasis, African/ethnology , Adolescent , Adult , Africa South of the Sahara/ethnology , Age Factors , Aged , Animals , Child , Child, Preschool , Emigration and Immigration , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Retrospective Studies , Time FactorsABSTRACT
The aetiological diagnosis of human African trypanosomiasis (HAT) is based on the detection of the parasite, but currently available parasitological tests have low sensitivity and are hampered by fluctuating parasitaemia. The identification of seropositive individuals on whom to focus parasitological examination is based on antibody detection by means of the Card Agglutination Trypanosomiasis Test (CATT/T.b.gambiense). A complicating phenomenon is the occurrence of serologically positive but parasitologically unconfirmed results (isolated CATT positivity). This work presents a two-year longitudinal serological, parasitological and molecular follow-up of CATT-positive individuals including repeated examinations of each individual, to study the evolution over time of seropositivity at both the population and the individual levels. At the population level, the rate of seropositivity decreased during the first months of the survey, and afterwards showed remarkable stability. At the individual level, the results reveal the extreme heterogeneity of this population, with subjects showing fluctuating results, others with a short transient CATT positivity, and subjects that maintain their seropositivity over time. The stability of seropositivity and the pattern of results obtained with both immunological and parasitological examinations support the view that individual factors, such as immune response to infection, might be involved in the isolated CATT positivity phenomenon.
