During the bloodstream stage of the Trypanosoma brucei lifecycle, the parasite exists in two different states: the proliferative slender form and the non-proliferative, transmissible, stumpy form. The transition from the slender to stumpy form is stimulated by a density-dependent mechanism and is important in infection dynamics, ordered antigenic variation and disease transmissibility. The slender to stumpy transition and the contribution of stumpy formation to within-host dynamics have been difficult to analyse, however, because cell-type specific markers have been restricted to imprecise morphological criteria. PAD1 is a recently identified stumpy-specific protein which acts as a molecular marker for stumpy formation and a functional marker for transmission. Here, the control of stumpy-specific gene expression via the 3’UTR has been analysed, identifying that there are repressive elements in the 3’UTR preventing inappropriate expression during the slender life stage. Further, both pleomorphic and monomorphic transgenic reporter cell lines utilising the PAD1 3’UTR have been created that report on stumpy formation in vitro and these have been used for the analysis of stumpyinducing chemical compounds. Finally, a sensitive and accurate qRT-PCR assay has been developed and optimised that faithfully reports both parasitaemia and stumpy formation throughout host infection. Using a chronic infection rodent model, stumpy levels have been monitored on the basis of conventional morphological and cell cycle assays, as well as by qRT-PCR for PAD1 expression. The results define the temporal order of events that result in the generation of stumpy forms early in a parasite infection and thereafter describe the dynamics of slender and stumpy forms in chronic infections extending over several weeks. This quantitative data has allowed the mathematical modelling of transmission competence in trypanosome infections, suggesting dominance of transmission stages throughout infection.

Avian contact zones were suggested to act as barriers to parasite expansions. I studied haemosporidian parasites (genera Plasmodium, Haemoproteus, and Leucocytozoon) of two Nightingale species which meet in a contact zone in Europe. In total 20 lineages of parasites were detected. Surprisingly, all common lineages were shared by the two host species. The parasite prevalence vary between species (Trush Nightingales were more often parasitized than Common Nightingales.) but did not vary to a large extent within zones inside species Parasitemia of the most frequent Haemoproteus LULU1 lineage assessed by Real-Time PCR method did not differ significantly between the two host species. Six out of nine hybrids of the nightingale species were parasitized. Haemosporidian lineages found in hybrids were also frequent in the parental species. In conclusion, the nightingale contact zone seems to have only little (if any) effect on the distribution of haemosporidian parasites.

Le paludisme tue un enfant toutes les 30 secondes en Afrique et 1 à 3 millions de personnes par an. Deux milliards d'individus sont exposés et on estime à 500 millions le nombre de cas cliniques survenant chaque année. Le paludisme étant une maladie multifactorielle, son évolution est soumise à l'influence d'effets environnementaux, à des variables telles que l'âge de l'individu, ainsi qu'à une combinaison de facteurs génétiques. De nombreux arguments sont en faveur d’un contrôle génétique de la résistance au paludisme, mais les gènes impliqués restent encore mal connus. Afin d’identifier de nouveaux gènes de résistance ou de susceptibilité au paludisme à Plasmodium falciparum, nous avons réalisé différentes études génétiques dans deux populations vivant en zone d’endémie palustre au Burkina Faso. Ainsi, des polymorphismes du gène IL12B situé dans une région chromosomique liée au paludisme (5q31-q33) ont été génotypés puis analysés. Nous n’avons pas décelé d’association allélique, mais ce travail a permis de confirmer l’existence d’une liaison génétique dans ce locus. Les données issues du génotypage du gène IL12B ainsi que celles d’études antérieures ont été utilisées pour évaluer les interactions génétiques entre la mutation provoquant l’hémoglobine C et 11 autres polymorphismes situés dans 5 gènes précédemment associés à la résistance au paludisme. En utilisant 3 phénotypes liés à l’infection palustre, nous avons ainsi pu observer 43 combinaisons multilocus significatives incluant des polymorphismes des gènes IL12B, IL4, TNF, NCR3 et LTA. Ces résultats d’interactions démontrent l’intérêt de développer ce type d’approches pour élucider le contrôle génétique de la résistance humaine au paludisme.Une approche par clonage positionnel, suivie d’une approche « gène candidat » nous a permis de mettre en évidence une liaison génétique entre la région 17p11-p13 et la parasitémie, puis une association allélique entre les gènes candidats HS3ST3A1 et HS3ST3B1 et la parasitémie. Ces gènes codent pour des isoenzymes transférant un groupement sulfate à des protéoglycanes afin de former des molécules d’héparane sulfates. L’implication potentielle de ces récepteurs, dans le contrôle génétique du paludisme suggère le rôle déterminant qu’ils pourraient jouer dans le déclenchement de l’infection, et fournit un nouveau terrain d’investigation pour l’identification de gènes contrôlant l’évolution de l’infection palustre. A notre connaissance, il s’agit de la première étude d’association entre un phénotype lié à l’infection palustre et des gènes impliqués dans la synthèse des héparane sulfates. / Malaria kills a child every 30 seconds in Africa and 1 to 3 million people per year. Two billion people are exposed and an estimated 500 million of clinical cases occur each year. Malaria being a multifactorial disease, its evolution is subject to the influence of environmental effects, variables such as age of the individual, and a combination of genetic factors. Many arguments are in favor of a genetic control of resistance to malaria, but the genes involved are still poorly understood. In order to identify new genes for resistance or susceptibility to Plasmodium falciparum, we performed genetic studies in two different populations living in malaria endemic area in Burkina Faso. Thus, polymorphisms of the IL12B gene located in a chromosomal region associated with malaria (5q31-q33) were genotyped and analyzed. We did not detect allelic association, but this work has confirmed the existence of a genetic linkage at this locus. Genotype data from IL12B gene and those of previous studies were used to evaluate interactions between the genetic mutation causing hemoglobin C and 11 other polymorphisms located in five genes previously associated with resistance to malaria. Using 3 phenotypes related to malaria infection, we were able to observe 43 significant multilocus combinations including IL12B gene polymorphisms, IL4, TNF, LTA and NCR3. These results demonstrate the interest to develop such approaches for elucidating the genetic control of human resistance to malaria. A positional cloning approach followed by a "candidate gene" approach allowed us to identify a genetic link between the region 17p11-p13 and parasitemia, and allelic association between candidate genes HS3ST3A1 and HS3ST3B1 and parasitemia. These genes encode isoenzymes transferring a sulfate group to proteoglycans to form molecules of heparan sulfates. The potential involvement of these receptors in the genetic control of malaria suggests the crucial role they might play in the onset of infection, and provides a new field of investigation for the identification of genes controlling the development of malaria infection. To our knowledge this is the first study of association between a phenotype associated with malaria infection and genes involved in the synthesis of heparan sulfates.

Bovine trypanosomosis is a serious constraint to livestock development in large parts of Mozambique. In most areas where tsetse flies are present, the disease in livestock is controlled using curative and prophylactic trypanocidal drugs. Those drugs have been used for many years and new drugs are unlikely to become available in the near future. As a result, trypanosomes have developed resistance against the currently available trypanocidal compounds. Drug resistance has been detected in various African countries and is a serious impediment to the control of livestock trypanosomosis. A study was initiated to determine whether drug resistant trypanosome strains are present in Zambézia Province of Mozambique. The aim of this study was to determine the sensitivity of Trypanosoma congolense isolates from Chinde, Nicoadala and Maganja da Costa Districts to diminazene aceturate, isometamidium chloride and homidium chloride. To assess the effect of the farming system and the intensity of drug regimens on the development of drug resistance, trypanosome isolates were collected from cattle from subsistence, semisubsistence and commercial livestock production systems. Drug-use practices in each of the production systems were determined using a questionnaire. The methodology used to assess the level of drugs resistance in the trypanosome isolates was the standardized method described by Eisler et al. (2001). Seven isolates were selected for resistance testing. For each of the seven isolates, five different doses varying between 0.01-20 mg/kg body weight for isometamidium chloride, 0.01-10 mg/kg body weight for homidium chloride and 1-30 mg/kg body weight for diminazene aceturate were used. For each dose rate six mice were treated intraperitoneally with the appropriate quantity of the drug dissolved in 0.2 ml of sterile distilled water 24 hours after the inoculation of the blood containing the trypanosomes. The control mice (six mice per trypanocidal drug) received the same amount of water without the drug. In four of the seven isolates high levels of multiple drug resistance (diminazene aceturate and isometamidium chloride) were detected. One isolate had a low level of multiple (diminazene aceturate and isometamidium chloride) drug resistance. Two isolates were susceptible to both diminazene aceturate and isometamidium chloride. One of those was highly susceptible to isometamidium chloride even at the lowest dose rate. The observed levels of drug resistance could in most cases be correlated to the drug-use practices in the particular livestock production system. The results obtained from homidium chloride treatment are not conclusive, because most the mice cured after receiving 10 mg/kg body weight of the drug. Hence more research is required to establish the homidium threshold in mice. The results of this study should be useful to define the strategy of disease control in places where resistance of trypanocide were been reported. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2005. / Veterinary Tropical Diseases / unrestricted

Moçambic registra una alta prevalença de malària amb un elevat índex de parasitèmia assintomàtica, però no hi ha estudis coneguts sobre la seva relació amb els diferents components del desenvolupament humà. L’objectiu va ser estudiar les característiques de creixement i desenvolupament dels nens, nenes i adolescents amb malària assintomàtica de les zones rurals de Calanga. L’estudi, de caràcter retrospectiu, es va portar a terme en una mostra de 351 subjectes d’ambdós, dividits en grups de 5-11 anys i 12-20 anys. Es varen obtenir mesures Antropomètriques (alçada, pes, perímetre bicipital, plecs cutanis), estat de maduració (escala de Tanner per caràcters sexuals secundaris), Aptitud física (flexibilitat, resistència muscular, agilitat, força i resistència cardiorespiratòria) i Activitat física realitzada (qüestionari i accelerometria). Per a la determinació del nivell de parasitèmia i altres indicadors hematològics, es varen obtenir mostres sanguínies. L’estat nutricional va ser estimat en funció dels criteris antropomètrics de la OMS/CDC. Per l’ anàlisis dels resultats, la mostra va ser dividida en dos grups d’ edat (G1 fins els 11 anys; G2 >11 anys) per a cada sexe. Els subjectes varen ser sotmesos a una exploració clínica minuciosa. Tots els subjectes sense síntomes clínics de malària participaren en l’estudi, sent-hi dividits en dos grups: Amb presència de Plasmodiun (CP) i Sense presència del paràsit (SP). L’Anàlisi estadístic es va centrar en la comparació dels diferents fenotips entre els grups CP i SP en funció del gènere i dels grups utilitzant un ANOVA factorial amb una significança del 5%. Els resultats indicaren una prevalença de malària assintomàtica del 53,9% amb una major incidència en G1. Foren observades diferències significatives en G2 en els nens, en l’alçada (p=0.01) i perímetre bicipital (p=0.001). No es va trobar cap diferència en l’estat nutricional. En l’Aptitud física es varen trobar diferències significatives en els grups de Handgrip p=0.001) i Flex Arm Hang (p=0.04). Respecte a l’activitat física no es varen registrar diferències significatives. Aquest estudi va mostrar que l’índex de malària assintomàtica reflexa l’alt nivell de parasistèmia en la població de Calanga, però l’alta supervivència condueix a un estat adaptatiu que pot causar la no observança d’efectes generalitzats en el creixement i desenvolupament motor com expressen els alts nivells d’activitat física en ambdós grups, ì que poden significar una adaptació d’aquests individus a les exigències del medi ambient. / Mozambique registra una alta prevalencia de malaria con alto índice de parasitemia asintomática, pero no hay estudios conocidos sobre su relación con los distintos componentes del desarrollo humano. El objetivo fue estudiar las características de crecimiento y desarrollo de los niños y jóvenes con malaria asintomática de las zonas rurales de Calanga. El estudio, de carácter retrospectivo, se llevó a cabo en una muestra de 351 sujetos de ambos sexos, divididos en grupos de 5-11 años y 12-20 años. Se obtuvieron medidas Antropométricas (altura, peso, perímetro bicipital, pliegues cutáneos), estado de maduración (escala de Tanner para caracteres sexuales secundarios), Aptitud física (flexibilidad, resistencia muscular, agilidad, fuerza y resistencia cardiorespiratoria) y Actividad física realizada (cuestionario y acelerometría). Para la determinación del nivel de parasitemia y otros indicadores hematológicos, se obtuvieron muestras sanguíneas. El estado nutricional fue estimado en función de los criterios antropométricos de la OMS/CDC. Para el análisis de los resultados, la muestra fue dividida en dos grupos de edad (G1 hasta los 11 años; G2 >11 años) para cada sexo. Los sujetos fueron sometidos a una exploración clínica minuciosa. Todos los sujetos sin síntomas clínicos de malaria participaron en el estudio, siendo divididos en dos grupos: con presencia de Plasmodiun (CP) y sin presencia del parásito (SP). El análisis estadístico se centró en la comparación de los diferentes fenotipos entre los grupos CP y SP en función del género y de los grupos utilizando un ANOVA factorial con una significancia del 5%. Los resultados indicaron una prevalencia de malaria asintomática del 53,9% con una mayor incidencia en G!. Fueron observadas diferencias significativas en G” en los niños, en la altura (p=0.01) y perímetro bicipital (p=0.001). No se encontró ninguna diferencia en el estado nutricional. En la Aptitud física se encontraron diferencias significativas en los grupos de Handgrip p=0.001) y Flex Arm Hang (p=0.04). Con respecto a la actividad física no se registraron diferencias significativas. Este estudio mostró que el índice de malaria asintomática refleja el alto nivel de parasistema en la población de Calanga, pero la alta sobrevivencia conduce a un estado adaptativo que puede causar la no observancia de efectos generalizados en el crecimiento y desarrollo motor como expresan los altos niveles de actividad física en ambos grupos, y que pueden significar una adaptación de estos individuos a las exigencias del medio ambiente. / While in Mozambique there is a high prevalence of malaria with high rate of asymptomatic parasitaemia, there are not known studies on the implications of this last condition, particularly on growth and development of school-age population. The purpose of this study was to understand the impact of the presence of asymptomatic malaria in growth and motor development in children and adolescents in rural areas. The study was conducted on a sample of 351 subjects of both sexes aged between 5 and 20 years living in a rural area of Mozambique. All participants underwent a protocol that included measures of Anthropometry (height, weight, biceps circumference, skinfolds of adiposity), Maturatioal Status (Tanner scale for secondary sexual characteristics), Physical Fitness (flexibility, muscular endurance, agility, strength and cardio-respiratory endurance.) and Physical Activity (Survey and Accelerometry). To determine the parasite and other hematologic indicators blood samples were extracted. Nutritional status was estimated on the basis of anthropometric criteria established by WHO / CDC. For data analysis the sample was divided into two age groups (G1 < 11 years, G2 > 11 years) for each sex. The subjects underwent a detailed clinical observation. All subjects without clinical symptoms of malaria remained in the study and were divided into two groups: with the presence of Plasmodium (CP) and without the presence of this parasite (SP). The statistical analysis focused on comparison of the different phenotypes between the groups CP and SP on gender and age using the ANOVA Factorial maintaining a significance level of 5%. The results indicated a prevalence of asymptomatic malaria by 53.9% with higher incidence in G1. Significant differences were observed in G2, in boys, height (p = 0.01) and biceps circumference (p = 0.001). No difference was found in relation to nutritional status. Indicators assessed blood were no different significantly except in hematocrit in boys G2. In Physical Fitness significant differences were found in the same group in the Flexed Arm Hang tests (0.04) and hand grip (p = 0.001). With regard to physical activity were not recorded significant differences. Given the small differences between the groups according to the parasite, it was concluded that the prevalence of asymptomatic malaria reflects the high level of parasitaemia among the population of Calanga but that, eventually, a high pressure of survival leads to an adaptive state that can cause non-compliance with widespread effects on growth and motor development, as expressed in high levels of physical activity in both groups and that can mean the adaptation to environmental demands. / Embora em Moçambique se observe uma elevada prevalência de malária com elevada taxa de parasitémia assintomática não são conhecidos estudos sobre as implicações desta ultima condição, em particular no crescimento e desenvolvimento da população em idade escolar. O objectivo deste estudo foi o de conhecer o impacto da presença de malária assintomática no crescimento e desenvolvimento motor em crianças e jovens residentes em zonas rurais. O estudo realizou-se numa amostra de 351 sujeitos de ambos os sexos de idades compreendidas entre os 5 e 20 anos residentes numa região rural de Moçambique. Todos os participantes foram submetidos a um protocolo de medidas que incluiu Antropometria (Altura, Peso, Perímetro Bicipital, Pregas de Adiposidade), Estado Maturacional (escala de Tanner para caracteres sexuais secundários), Aptidão Fisica (flexibilidade, resistência muscular, agilidade, força e resistência cardiorespiratória.) e Actividade Fisica (Questionário e Acelorometria). Para a determinação da parasitémia e outros indicadores hematológicos foram extraídas amostras de sangue. O estado nutricional foi estimado em função dos critérios antropmétricos estabelecidos pela OMS/CDC. Para análise dos resultados a amostra foi dividida em dois grupos etários (G1 até 11 anos; G2>11 anos) para cada sexo. Os sujeitos foram submetidos a uma observação clínica minuciosa. Todos os sujeitos sem sintomas clínicos de malária permaneceram no estudo, tendo sido divididos em dois grupos, nomeadamente: Com a presença do Plasmodium (CP) e sem a presença deste parasita (SP). A análise estatística centrou-se na comparação dos diferentes fenótipos entre os grupos CP e SP em função do género e grupo etário, utilizando a ANOVA Factorial mantendo um nível de significância de 5%. Os resultados indicaram uma prevalência de malária assintomática de 53,9 % com maior incidência no G1. Foram observadas diferenças significativas no G2, nos rapazes, na altura (p=0,01) e perímetro bicipital (p=0,001). Nenhuma diferença foi encontrada no que respeita ao estado nutricional. Dos indicadores hematológicos avaliados foram observadas diferenças significativas no hematócrito nos rapazes do G2. Na Aptidão Física foram encontradas diferenças significativas no mesmo grupo nos testes de Flexed Arm Hang (0.04) e Hand grip (p=0,001). Relativamente à Actividade Física não foram registadas diferenças significativas. Face às reduzidas diferenças entre os grupos em função da parasitémia, foi concluído que a prevalência da malária assintomática reflecte a elevada taxa de parasitémia no seio da população da Calanga mas que, eventualmente, uma elevada pressão de sobrevivência conduz a um estado adaptativo que pode causar a não observância de efeitos generalizados no crescimento e desenvolvimento motor como expressam os níveis elevados de actividade física em ambos os grupos e que podem significar uma adaptação destes indivíduos às exigências do ambiente.