Morphological differences between Venezuelan and African microfilariae of Onchocerca volvulus

High Prevalence of Glaucoma among Patients in an Onchocerciasis Endemic Area (Mahenge, Tanzania)

Onchocerciasis is known to cause skin lesions and blindness, but there is also epidemiological evidence that onchocerciasis is associated with epilepsy, including nodding syndrome. We carried out ocular exams in persons with epilepsy in Mahenge, an onchocerciasis endemic area with a high prevalence of epilepsy in Tanzania. We recruited 278 consecutive persons with epilepsy attending the epilepsy clinic at Mahenge hospital and satellite clinics in rural villages. They underwent a general physical and a detailed ocular examination and were tested for onchocerciasis Ov16 IgG4 antibodies. Glaucoma was defined by a raised intraocular pressure above 21 mmHg with evidence of typical glaucomatous disc changes in one or both eyes. Among the 278 participants, median age 27 (IQR 21-38) years, 55.4% were female; 151/210 (71.9%) (95% CI: 65.3-77.9) were Ov16 positive. The most frequent ophthalmic lesions were glaucoma (33.1%), vitreous opacities (6.5%) and cataracts (2.9%). In multivariate analysis, glaucoma (adjusted IRR = 1.46; 95% CI: 1.24-1.70) and age (adjusted IRR = 1.01; 95% CI: 1.01-1.02) were significantly associated with onchocerciasis. In conclusion, a high prevalence of glaucoma was observed among Ov16 positive persons with epilepsy. Persons with epilepsy with O. volvulus infection should undergo screening for glaucoma to prevent one of the causes of preventable blindness.

Genomic diversity in Onchocerca volvulus and its Wolbachia endosymbiont

Ongoing elimination efforts have altered the global distribution of Onchocerca volvulus, the agent of river blindness, and further population restructuring is expected as efforts continue. Therefore, a better understanding of population genetic processes and their effect on biogeography is needed to support elimination goals. We describe O. volvulus genome variation in 27 isolates from the early 1990s (before widespread mass treatment) from four distinct locales: Ecuador, Uganda, the West African forest and the West African savanna. We observed genetic substructuring between Ecuador and West Africa and between the West African forest and savanna bioclimes, with evidence of unidirectional gene flow from savanna to forest strains. We identified forest:savanna-discriminatory genomic regions and report a set of ancestry informative loci that can be used to differentiate between forest, savanna and admixed isolates, which has not previously been possible. We observed mito-nuclear discordance possibly stemming from incomplete lineage sorting. The catalogue of the nuclear, mitochondrial and endosymbiont DNA variants generated in this study will support future basic and translational onchocerciasis research, with particular relevance for ongoing control programmes, and boost efforts to characterize drug, vaccine and diagnostic targets.

Similar cases retrieval from the database of laboratory test results

We proposed a suitable method to search similar cases from the laboratory test results database, whose data are basically numerical and ordinal data. We transformed raw data into ordinal ranks and into new scores lying between 0 and 1, then calculated the Mahalanobis distances as a similarity measure. We used 3000 cases of blood count data. In 100 sample cases, 95% of the most similar 20 cases obtained by our method were included in those by the criterion (Mahalanobis distances calculated from raw data). Next, we applied our method to the data relevant to thyroid diseases. In 96 sample cases, the most similar 10 cases were retrieved from 1655 cases. The diagnoses were consistent with that of the sample cases in 32.4%. When we used Euclidean distance, the result worsened to 27.7%. Our method proved to be suitable in our attempt to identify similar cases in complicated laboratory test data.

Strain differentiation of Onchocerca volvulus from Uganda using DNA probes

Polymerase chain reaction (PCR) combined with non-radioactive DNA hybridization was applied for the detection and characterization of a 150 bp tandem repeat of Onchocerca volvulus. DNA of worms from western Uganda was amplified and then probed with a digoxygenin-labelled oligonucleotide, specific for the forest form of O. volvulus and compared to samples from various African countries. Hybridization was only observed with PCR products from the forest in Liberia, south-eastern Ghana, Benin and southern Cameroon, but not with worms from Uganda or the savannah in Burkina Faso and northern Ghana. A nested PCR using primers derived form the forest form-specific DNA sequence confirmed these results. Morphometric studies revealed length differences between the microfilariae of Ugandan O. volvulus to those of West Africa, especially to those of the savannah in Burkina Faso. It is concluded that the forest/savannah classification of O. volvulus from West Africa is not suitable for Simulium neavei-transmitted O. volvulus from Uganda.

Molecular variation in Onchocerca spp

Over the past two decades there has been an upsurge of interest in defining morphological, immunological, biochemical, biological and genetic differences between species of Onchocerca to provide solutions to practical problems associated with finding models and epidemiological tools to assist with control of human onchocerciasis. The information gathered has confirmed the close relationship between species of Onchocerca and provided highly sensitive and specific probes to distinguish species and even strains of the same species. It has also identified pathways, especially using sequences from common DNA repeat units, that may lead to a better understanding of the progression of divergence of species of this genus than has previously been possible.