Identification of economically important parasites

Restriction site detection in repetitive nuclear DNA sequences of Trypanosoma evansi for strain differentiation among different isolates

The differences or similarities among different isolates of Trypanosoma evansi through endonuclease profile was identified in the present study. The repetitive nuclear DNA of T. evansi isolated from infected cattle, buffalo and equine blood was initially amplified by PCR using specific primers. A panel of restriction enzymes, EcoRI, Eco91l, HindIII and PstI were for complete digestion of PCR products. Agarose gel electrophoresis of digested product did not show cleavage fragments and only single DNA band of the original size was visible in the ethidium bromide stained agarose gel. This indicated that the 227 bp PCR product from repetitive sequence had no site-specific cleavage sites for the REs used in this study. No heterogeneity in the repetitive nuclear DNA restriction endonuclease profile among the different isolates was recorded.

Association between Papio hamadryas populations and human gastrointestinal infectious diseases in southwestern Saudi Arabia

BACKGROUND AND OBJECTIVES

Papio hamadryas baboons, known reservoirs of several infectious diseases, roam and deposit their excreta indiscriminately on footpaths, parks, and streets of the city peripheries of Taif, Baha, and Abha in southwestern Saudi Arabia. Nonetheless, city centers of these places are free of baboons. This study aims to determine the impact of baboons on human gastrointestinal health.

DESIGN AND SETTINGS

This is a descriptive cross-sectional analytical ecological study conducted in 3 cities located in southwestern Saudi Arabia between July 2011 and July 2012.

MATERIALS AND METHODS

We investigated the impact of these baboons on the human health through a coprological survey of infectious agents of baboons and humans in these 3 cities using macroscopic and micro.scopic analyses, before and after parasite concentration, and culturing of bacteria on selective and differential media, which were then identified by 16S rDNA gene sequencing. Baboon fecal samples (n=823) were collected from city peripheries. Two groups of human fecal samples, each consisting of 795 samples were collected, one from city centers and the second from city peripheries where baboons intermingle with the human population.

RESULTS

Baboon fecal samples were the most contaminated with infectious agents, except for Staphylococcus aureus, which was more commonly present in human fecal samples collected from city peripheries. Human fecal samples collected form city peripheries showed higher rates of most infective agents than those collected from city centers.

CONCLUSION

This indicates that baboons are medically important reservoirs of infectious agents associated with higher human coproprevalence of gastrointestinal infectious agents.

Molecular epidemiology of African sleeping sickness

Human sleeping sickness in Africa, caused by Trypanosoma brucei spp. raises a number of questions. Despite the widespread distribution of the tsetse vectors and animal trypanosomiasis, human disease is only found in discrete foci which periodically give rise to epidemics followed by periods of endemicity A key to unravelling this puzzle is a detailed knowledge of the aetiological agents responsible for different patterns of disease – knowledge that is difficult to achieve using traditional microscopy. The science of molecular epidemiology has developed a range of tools which have enabled us to accurately identify taxonomic groups at all levels (species, subspecies, populations, strains and isolates). Using these tools, we can now investigate the genetic interactions within and between populations of Trypanosoma brucei and gain an understanding of the distinction between human- and nonhuman-infective subspecies. In this review, we discuss the development of these tools, their advantages and disadvantages and describe how they have been used to understand parasite genetic diversity, the origin of epidemics, the role of reservoir hosts and the population structure. Using the specific case of T.b. rhodesiense in Uganda, we illustrate how molecular epidemiology has enabled us to construct a more detailed understanding of the origins, generation and dynamics of sleeping sickness epidemics.

Inhibition of experimental asthma by indoleamine 2,3-dioxygenase

Epidemiological evidence points to the inverse relationship between microbial exposure and the prevalence of allergic asthma and autoimmune diseases in Westernized countries. The molecular basis for this observation has not yet been completely delineated. Here we report that the administration of certain toll-like receptor (TLR) ligands, via the activation of innate immunity, induces high levels of indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme of tryptophan catabolism in various organs. TLR9 ligand-induced pulmonary IDO activity inhibits Th2-driven experimental asthma. IDO activity expressed by resident lung cells rather than by pulmonary DCs suppressed lung inflammation and airway hyperreactivity. Our results provide a mechanistic insight into the various formulations of the hygiene hypothesis and underscore the notion that activation of innate immunity can inhibit adaptive Th cell responses.

Detection and characterization of Leishmania species and strains from mammals and vectors by hybridization and restriction endonuclease digestion of kinetoplast DNA

Leishmania parasites from animals, man or insect vectors were characterized by the gel electrophoresis of restriction endonuclease enzyme-produced mitochondrial (kinetoplast) DNA (kDNA) fragments and/or by DNA-DNA hybridization with 32P-labelled cloned, or uncloned, kDNA fragment probes from type isolates. The electrophoretic separation of kDNA fragments is a sensitive method for detecting genetic similarities and differences among Leishmania. Parasites with similar kDNA restriction fragment patterns belong to the same schizodeme and schizodeme analysis is useful for studying Leishmania populations. Cloned, species-specific kDNA probes detected Leishmania in sandflies and in liver, spleen or blood preparations from infected animals. Cloned DNA probes also hybridized to immobilized kDNA from in vitro cultivated promastigotes and detected as few as 100 parasites in a species-specific manner. Sensitive DNA hybridization probes should be useful in research on the immunology, chemotherapy or epidemiology of animal and human leishmaniasis.

Enzyme polymorphism and the distribution of Trypanosoma congolense isolates

Conditions were established for demonstrating, by electrophoresis, polymorphism in 12 soluble enzymes from Trypanosoma congolense. Three enzymes had identical mobilities in every stock, variation occurring among the remaining nine. Enzyme profiles were determined in 78 stocks collected from various hosts in a number of African countries, and were used by the computer to establish relationships within the collection. The major groupings formed solely from the isoenzymes corresponded remarkably closely to the origins of the stocks. Two distinct enzymic divisions formed, related only at the 20% level; Division A consisted entirely of stocks isolated in the humid coastal areas of West Africa, while Division B consisted mostly of stocks from drier zones throughout Africa. Some large groupings within these two main divisions also correlated with particular areas of origin within the major ecologic zones. The dry zone Division B included one group almost exclusively from East Africa, and two quite distinct enzymic groups from The Gambia; isolates from Liberia and Ivory Coast tended to fall into separate groups within the humid zone Division A. It is suggested that the differences between the major divisions may be associated with infraspecific adaptation to the different vector species occupying the separate habitats.

Delimitation of Trypanosoma cruzi zymodemes by numerical taxonomy

Based on the absence or presence of 24 isoenzyme characters, Brazilian Trypanosoma cruzi stocks can be separated by methods of numerical taxonomy into three principal, distinct groups; these groups correspond to the three T. cruzi zymodemes previously reported from north Brazil. A distinction is drawn between taxonomy, which may be of zoological interest only, and identification of medically important groups according to one or a few distinguishing characters.