The application of molecular biology techniques to analyse diversity in Theileria parva populations in Zambia

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Theileria parva is a complex protozoan parasite causing East Coast fever in Eastern and Central Africa. Vaccination using live parasites is an effective control measure and has been used in Zambia based on locally isolated and introduced T. parva stocks. Diversity among T. parva populations was investigated in parasites from two Zambian provinces with different disease epidemiologies and control histories. Isolates from the pre-vaccination era, local and exotic stocks used for vaccination, and one recent field isolate were cloned and passaged in vitro to study genomic stability over time. The results of the data from three genome-wide probes indicate a marked homogeneity and stability among the Zambian isolates in contrast to East African isolates. Results from Southern blot profiles and the polymorphic immunodominant molecule (PIM) sequence analysis suggest a common origin for the Zambian isolates from the pre-vaccination era, except for one isolate (Zam5) from Southern Province. This isolate showed characteristics suggesting a buffalo origin. Assays for genotype characterisation were developed using five allelic markers. Multilocus characterisation revealed identical profiles in a recent Zambian isolate from Southern Province and two components of an exotic cocktail vaccine, indicating the escape of one of the vaccine stocks in the field. Characterisation of T. parva field populations by RFLP-PCR assays after immunisation revealed the presence of dominant genotypes from those that had been used for vaccination. Circumstantial evidence for the involvement of one of the exotic vaccine parasites in epidemics in Southern Province is presented and a hypothesis formulated for the rapid spread of this genotype. Analysis of the characterisation data suggested the existence of two groups of T. parva parasites of different origin. The classic T. parva group, characterised by a dimorphism of the p150, p104 and p32 loci and the absence of a p67 insert and a buffalo-derived group which showed a polymorphism of p150, p104 and p32 and the presence of a p67 insert. There is evidence that recombination occurs, resulting in parasites that have characteristics of both groups. The relevance of these recombinant parasites in the epidemiology of the disease seems low. Characterisation of larger samples from areas of regular buffalo-cattle contact is necessary to clarify this. Sequence analysis of the most discriminative locus (PIM) was undertaken and gene conversion could be the main mechanism generating diversity. A more appropriate nomenclature for T. parva is proposed based on the growing evidence of molecular differences among isolates and stocks.Belgian Administration for Development Cooperatio

Whole-genome sequencing of Theileria parva strains provides insight into parasite migration and diversification in the african continent

The disease caused by the apicomplexan protozoan parasite Theileria parva, known as East Coast fever or Corridor disease, is one of the most serious cattle diseases in Eastern, Central, and Southern Africa. We performed whole-genome sequencing of nine T. parva strains, including one of the vaccine strains (Kiambu 5), field isolates from Zambia, Uganda, Tanzania, or Rwanda, and two buffalo-derived strains. Comparison with the reference Muguga genome sequence revealed 34 814–121 545 single nucleotide polymorphisms (SNPs) that were more abundant in buffalo-derived strains. High-resolution phylogenetic trees were constructed with selected informative SNPs that allowed the investigation of possible complex recombination events among ancestors of the extant strains. We further analysed the dN/dS ratio (non-synonymous substitutions per non-synonymous site divided by synonymous substitutions per synonymous site) for 4011 coding genes to estimate potential selective pressure. Genes under possible positive selection were identified that may, in turn, assist in the identification of immunogenic proteins or vaccine candidates. This study elucidated the phylogeny of T. parva strains based on genome-wide SNPs analysis with prediction of possible past recombination events, providing insight into the migration, diversification, and evolution of this parasite species in the African continent

Plagas y enfermedades presentes en cultivo hidropónico de dos variedades de tomate (Lycopersicon esculentum, Mill), bajo condiciones semi controladas en Chachapoyas – Perú

El tomate es una de las hortalizas más importantes en el mundo, la presente investigación tuvo como objetivo identificar las principales plagas y enfermedades presentes en el cultivo hidropónico de tomate (Lycopersicom esculentum, Mill), producidos en dos tipos de sustrato, diferentes dosis y bajo condiciones semi controladas de invernadero en la Estación Experimental Chachapoyas, Amazonas, Perú. Se utilizó un Diseño Factorial en Bloques Completamente al Azar con cuatro bloques, tres tratamientos y dos variedades de tomate (Abigail y Rio Grande). Los tratamientos evaluados fueron: T1: 100% de cascarilla de arroz, T2: 75% cascarilla de arroz + 25% arena y T3: 50% cascarilla de arroz + 50% arena. Para el procesamiento estadístico de los datos se usó la versión de prueba del Software SPSS y los resultados obtenidos se analizaron en un diseño en bloques completamente al azar, se sometieron a la prueba no paramétrica de Kolmogorov Smirnov, se aplicó el análisis de varianza, se realizó la prueba de comparación múltiple de Tukey al 5% de significación y la correlación de Pearson. La principal plaga identificada fue la mosca blanca (Trialeurodes vaporariorum) con una incidencia mayor en la variedad Abigail y la enfermedad el Oidiosis (Oidium sp) con incidencias no significativas en las dos variedades. El tratamiento T3 presentó mayor incidencia tanto para la plaga y la enfermedad, lo que indica que la este tipo de sustrato no es adecuado para el cultivo. La variedad Abigail presentó mayores valores en altura de planta (1.67 m), rendimiento promedio (1.8 kg/planta), número promedio de frutos/planta (21)

Lack of evidence for safe vaccination with the Muguga cocktail in Sudan

How to cite this article: Geysen, D. & Berkvens, D., 2013, ‘Lack of evidence for safe vaccination with the Muguga cocktail in Sudan’, Onderstepoort Journal of Veterinary Research 80(1), Art. #571, 1 page. http:// dx.doi.org/10.4102/ojvr. v80i1.57

Risk-based inspection as a cost-effective strategy to reduce human exposure to cysticerci of Taenia saginata in low-prevalence settings

Taenia saginata cysticercus is the larval stage of the zoonotic parasite Taenia saginata, with a life-cycle involving both cattle and humans. The public health impact is considered low. The current surveillance system, based on post-mortem inspection of carcasses has low sensitivity and leads to considerable economic burden. Therefore, in the interests of public health and food production efficiency, this study aims to explore the potential of risk-based and cost-effective meat inspection activities for the detection and control of T. saginata cysticercus in low prevalence settings