Seasonal and altitudinal variations in fly density and their association with the occurrence of trachoma, in the Gurage zone of central Ethiopia.

In the Gurage zone of central Ethiopia, the association between fly density and the occurrence of trachoma has been investigated across varying altitudes. The seasonal pattern of fly density in the area was also explored. When, over short sampling periods (10 min/child indoors and 10 min/child outdoors), hand nets were used to collect flies from the eyes of children aged 2-8 years, only Musca sorbens and M. domestica were caught. Almost all of the 13,147 'eye-seeking' flies collected came from villages at low (<2000 m; 40.7%) or mid altitudes (2200-2500 m; 58.6%) with only 0.7% of them caught in the high-altitude villages investigated (at >3000 m). Musca sorbens predominated outdoors and M. domestica indoors. Almost all (99.3%) of the eye-seeking M. sorbens collected were caught outdoors whereas most (76.7%) of the M. domestica were caught indoors (P<0.0001 for each). The median numbers of flies caught, per child, per 10-min collection, in the low-, mid- and high-altitude villages were 9.5, six and zero, respectively, for M. sorbens, and eight, three and zero, respectively, for M. domestica. The altitudinal trends in these numbers of 'eye-seeking' flies matched those in the prevalences of active trachoma among children aged 1-10 years, which were high in the villages at low (81.6%) and mid altitude (78.7%) but much lower (1.7%) in the high-altitude villages. In conclusion, trachoma is a common disease of public-health importance only in the low- and mid-altitude villages in the Gurage zone, where there are large numbers of eye-seeking flies, and not in the villages that lie >3000 m above sea level, where there is a dearth of such flies.

Host choice by indoor-resting Anopheles arabiensis in Ethiopia.

The host preference of indoor resting Anopheles arabiensis has been determined using a direct enzyme-linked immunosorbent assay. A total of 611 specimens, 258 from human dwellings, 179 from mixed dwellings, and 174 from cattle sheds, was examined. The proportion of human blood meals identified was highest from mosquitoes caught in human dwellings (91.5%), followed by those from mixed dwellings (20.2%) and cattle sheds (3.5%) (P < 0.0001). The smaller proportion of human blood meals from mixed dwellings suggests that cattle may protect humans from A. arabiensis.

Helicobacter pylori, gastritis and non-ulcer dyspepsia in Ethiopian patients.

The aim of this study is to find out the prevalence of Helicobacter pylori infection in patients with nonulcer dyspepsia (NUD) and asymptomatic controls and to see if there is an etiological association between gastritis, NUD and Helicobacter pylori. One hundred thirty six patients with NUD and 71 controls had six endoscopic biopsies from different sites of the gastric mucosa for histological diagnosis. Helicobacter pylori was looked for in all biopsy specimens utilizing half Gram, Giemsa and Gimenez staining techniques. Type B chronic gastritis was detected in 96% of the NUD cases and in 100% of the asymptomatic controls (P > 0.05). Helicobacter pylori was found in 82 (65%) patients with NUD and in 38 (56%) asymptomatic controls (P > 0.05). Type B chronic gastritis is almost universal in both NUD cases and asymptomatic controls. There is no difference in the prevalence of Helicobacter pylori infection between the two groups. The absence of Helicobacter pylori in a significant number of patients (36%) and controls (45%) with gastritis contradicts the etiological association between Helicobacter pylori and gastritis reported by others, suggesting that in Ethiopia there may be a chronic environmental gastritis which may not be helicobacter-related. There is no correlation between NUD and Type B gastritis, and between symptoms and Helicobacter pylori infection in this population.

Decline of Glossina morsitans ugadensis in Gambella, Ethiopia.

Gambella is the only area where sleeping sickness is endemic in Ethiopia. Four species of Glossina had been reported from Gambella out of the five species found in the country in surveys made before 1985. These are Glossina morsitans ugadensis, G. pallidipes, G. fuscipes and G. tachinoides. A tsetse fly survey was carried out in parts of Gambella owing to the fact that the area is undergoing ecological changes due to massive deforestation (because of resettlement and development programmes), poaching, and introduction of domestic animals into tsetse infested parts of Gambella after 1985. Tsetse populations were sampled for one year, March 1993-April 1994, using biconical traps and hand catches. The survey has reported all Glossina spp which were previously reported except G. morsitans ugadensis. It seems that a combination of factors, such as, lack of host and increase in human population have forced G. morsitans ugadensis to decline. This study has consolidated the fact that tsetse flies of the morsitans group specially G. morsitans, are easily affected by human interference while the palpalis group is resistant to this factor. In addition, this study has also indicated, villagization and rural development could be practised where G. morsitans is the only species in a certain area to alleviate pressure on already impoverished land in parts of Africa.