The Districts of Macenta and Guéckedou, situated in the West African rain forest of Guinea, provided the Institute with the unique opportunity to study onchocerciasis and Lassa fever. After nearly two years of operation, the "IMTH" (Institut de Médecine Tropicale de Hambourg) completed its programme and moved to KCCR (Kumasi Centre for Collaborative Research in Tropical Medicine), Kumasi, Ghana, with an option to return for follow-up studies on onchocerciasis and to continue its research programmes on Lassa fever. As before, the Institute was supported by both the Ministry of Health (MS) and the District Health Service (DPS) in Macenta. During 1997 the research programme of the IMTH continued to concentrate on the epidemiology, pathogenesis, clinical features and the immune response to onchocerciasis. Three different clinical forms of onchocerciasis within the communities were identified and were used as the basis for a number of research projects. This included individuals with the generalized form of the disease, those with sowda, the so-called hyperreactive type of onchocerciasis, and a third group of 34 individuals, the "putatively immune" persons who appeared to be immune to the disease, having been exposed but with no clinical manifestations.
In addition to the onchocerciasis survey performed in eight villages in 1996, four villages were studied during 1997. The prevalence of onchocerciasis in the four villages was between 40 and 86 %. 320 patients underwent nodulectomy when 1280 onchocercomata were removed. Following the studies mass treatment programmes with ivermectin were carried out in each of the villages according to the recommendation of OCP. In addition, treatment programmes with ivermectin were repeated in five hyperendemic villages which had been surveyed in 1995. During its four months of operation the research station enabled various re-search teams to carry out the following studies:

• Peripheral blood mononuclear cells were isolated from individuals with the generalized form and mechanisms of T cell responses directed against O. volvulus adult antigen were investigated.
• Delayed Type Hypersensitivity (DTH) to O. volvulus was assessed by means of a skin test including a non-endemic control population from Conakry, Guinea.
• Renal abnormalities occurring in patients with onchocerciasis were investigated. The studies were performed both, before and after treatment with ivermectin.
• The association between the various clinical forms of onchocerciasis and the presence of intestinal helminths was investigated by means of stool survey checking for the presence of adult worms.
• Adult worms and microfilarial larvae were exposed to various types of immunological stress in parallel to unexposed
• worms in order to identify parasite defense proteins.
• A study was made to investigate whether individuals considered to be putatively immune to O. volvulus are less attractive for blackflies than individuals with the generalized form of onchocerciasis.
• The prevalence of Lassa virus infections had been studied in various communities of the district of Macenta and Guéckedou and virus isolates obtained. The aim of this study was to investigate the virulence of strains of the forest region in Guinea.

The great success of an operation such as this is not only dependent upon the hard work of an ambitious enthusiastic team of scientists and support staff from both Guinea and Hamburg but also on the close collaboration between both individuals and organisations. We are deeply indebted to the people of Macenta and its environs, who were both welcoming and keen to participate in the various projects. In particular we would like to thank the Ministry of Health, the DPS, our collaborators in the General Hospital of Macenta, the Mission Hospital of Philafricain and members of the National Onchocerciasis Control Program. Again I would like to express our deep gratitude to all those individuals who supported us and whose contributions were beyond those that we might have expected.

There is evidence that, in areas endemic for onchocerciasis, some people appear to be immune to the parasite. Theoretically it is possible that these putatively immune persons did not become infected because they were insufficiently attractive for the host seeking vector flies. Therefore, comparative fly catches were carried out by 21 pairs of putatively immune persons and individuals with high counts of microfilariae near a hyperendemic village on the Makona river in Guinea from February to April 1997. A total of 1944 flies were caught by the putatively immune persons and 1850 by those with clinical onchocerciasis. The majority of the flies was identified as Simulium yahense (95.8%), the remaining ones were S. squamosum, S. soubrense and savanna species. Of the 970 parous S. yahense caught by the putatively immune vector collectors were 165 carrying infections with a total of 919 larvae of O. volvulus. The individuals with onchocerciasis caught 909 parous S. yahense of which 159 females were infected with 944 larvae. Statistically (Wilcoxon matched pairs test) there was no evidence that the putatively immune people caught fewer flies (p=0.96), fewer infected S. yahense (p=0.92) or flies with lower loads of O. volvulus larvae (p=0.92). It can be concluded that putatively immune persons and individuals with a diagnosed onchocerciasis were equally attractive for the local vectors of O. volvulus.
*) KCCR Kumasi, Ghana
 
 

Staff

Dr. Thomas F. Kruppa, Head
Dr. Zézé Albert
Dr. Ernst F. Diekmann

Support Staff (Guinea)

Lincoln Gankpala (lab technician)
Raphael Guilavogui (lab technician)
Momo Harris (lab technician)
Mohammad Sanho (administrator)
Oouo Sakovogui (nurse)
Balla Zoumanigui (nurse)
4 Watchmen
4 Drivers
2 Cleaners
2 Fieldworkers
1 Patient house manager
1 Electrician
1 Mechanic