Human trypanosomiasis in Ethiopia: the Gilo River area

Population studies of Glossina pallidipes in Ethiopia: emphasis on cuticular hydrocarbons and wing morphometric analysis

Tsetse flies, like many insects, use pheromones for inter- and intra-specific communication. Several of their pheromones are cuticular hydrocarbons (CHCs) that are perceived by contact at close range. We hypothesized that for a successful implementation of the Sterile Insect Technique (SIT), along with proper identification of target area and target species, the target tsetse populations and the sterile flies must chemically communicate with each other. To study the population structuring of Glossina pallidipes in Ethiopia, CHCs were extracted and analyzed from three tsetse belts. As a comparative approach, wing morphometric analysis was performed. The analysis of the relative abundance of CHCs revealed that populations of G. pallidipes from the Rift Valley tsetse belt showed a distinct clustering compared to populations from the other two belts. The spatial pattern of CHC differences was complemented by the wing morphometric analysis. Our data suggest that CHCs of known biological and ecological role, when combined with wing morphometric data, will provide an alternative means for the study of population structuring of Glossina populations. This could aid the planning of area wide control strategies using SIT, which is dependent on sexual competence.

Human African trypanosomiasis in South Sudan: how can we prevent a new epidemic?

Human African trypanosomiasis (HAT) has been a major public health problem in South Sudan for the last century. Recurrent outbreaks with a repetitive pattern of responding-scaling down activities have been observed. Control measures for outbreak response were reduced when the prevalence decreased and/or socio-political crisis erupted, leading to a new increase in the number of cases. This paper aims to raise international awareness of the threat of another outbreak of sleeping sickness in South Sudan. It is a review of the available data, interventions over time, and current reports on the status of HAT in South Sudan. Since 2006, control interventions and treatments providing services for sleeping sickness have been reduced. Access to HAT diagnosis and treatment has been considerably diminished. The current status of control activities for HAT in South Sudan could lead to a new outbreak of the disease unless 1) the remaining competent personnel are used to train younger staff to resume surveillance and treatment in the centers where HAT activities have stopped, and 2) control of HAT continues to be given priority even when the number of cases has been substantially reduced. Failure to implement an effective and sustainable system for HAT control and surveillance will increase the risk of a new epidemic. That would cause considerable suffering for the affected population and would be an impediment to the socioeconomic development of South Sudan.

The value of a direct agglutination test in the diagnosis of cutaneous and visceral leishmaniasis in Ethiopia

The usefulness and sensitivity of a direct agglutination test (DAT) in the diagnosis of cutaneous leishmaniasis due to Leishmania aethiopica infection has been investigated. Formalin-fixed, trypsin-treated and Coomassie blue-stained Leishmania promastigotes of various origins were used as antigens. L. major, L. donovani, L. aethiopica but not L. tropica antigen preparations were able to distinguish sera from individuals infected with Leishmania from sera of uninfected controls, although the titres of sera from patients with localized cutaneous leishmaniasis were low. Comparable results were obtained when the same sera were tested using freshly prepared antigen or antigen stored for 10 months at 4 degrees C. The assay was also used to monitor improvement of disease status following treatment of diffuse cutaneous leishmaniasis patients, and it was found to correlate well with the changing clinical status of the patients.

A comparison of skin-test responses using antigen from Leishmania donovani and a lizard trypanosome

261 individuals were skin tested with leishmanin from Leishmania donovani and with an antigen from a lizard trypanosome isolated in an area endemic for kala-azar in Ethiopia. 83 of the 261 responded positively, with indurations of 5 mm or greater, to one antigen but negatively to the other, and 42 reacted positively to both. Among the Afar people of the Awash valley in north-eastern Ethiopia and the Nyangatom people of south-western Ethiopia, positive response to both antigens was high, though many individuals responded to one antigen but not the other. Both these groups live as cattle pasturalists, a predominantly male occupation, in areas where known vectors of kala-azar as well as lizard-feeding sandflies exist. Among the Anuak and Suri people, who live in areas of south-western Ethiopia infested with tsetse flies, the lizard trypanosome antigen gave a markedly higher skin test positivity than did the leishmanin antigen. This suggests that the lizard trypanosome may give artificially high results in other immunological tests of exposure to trypanosomiasis in areas where lizard trypanosomes and man-biting sandflies co-exist with mammalian trypanosomes transmitted by Glossina.