PREVISIONES Y OTRAS SITUACIONES CONTINGENTES

Richard O′Connor, Jessica Jenson and Eileen Devaney.

Dept. of Veterinary Parasitology, Glasgow University, Bearsden Rd, Glasgow, G61 1QH

Following i.v. infection with mf of B. pahangi splenocytes from BALB/c mice show an active suppression of the Ag-specific proliferative response in vitro. Suppression is mediated by the IFN-γ dependant induction of iNOS activity which limits both proliferation and IFN-γ production. High level NO production is associated with elevated levels of CD4+ T cell apoptosis and inhibition of iNOS activity both reverses the apoptotic phenotype and restores defective proliferation. Furthermore the absence of NO there is expansion of a subpopulation of T cells which have upregulated surface expression of CD4. These CD4hi cells are seen most markedly amongst cells from mf-infected animals and show characteristics of activated T cells and evidence of Ag-specific division by CFSE labeling. These results demonstrate that the NO mediated apoptosis of Ag-reactive T cells contributes to the proliferative defect seen in vitro in this model and suggest one way in which, under conditions of chronic restimulation, T cell apoptosis may regulate the expansion of pro-inflammatory responses.

Recent developments on the immunopathology of onchocercal corneal disease

Bancroftian filariasis: patterns of transmission in a high and a low endemicity community in East Africa

E.M. Pedersen1, R.T. Rwegoshora2, D. Mukoko3, D.W. Meyrowitsch1, M.N. Malecela- Lazaro2, E. Michael4 & P.E. Simonsen1

1

Danish Bilharziasis Laboratory, Denmark; 2

National Institute for Medical Research, Tanzania; 3

Division of Vector Borne Diseases, Kenya; 4

Imperial College School of Medicine, London, U.K.

The patterns of Wuchereria bancrofti transmission in a high and a low endemicity community in East Africa were investigated through intensive longitudinal surveillance of the vector population. Mosquitoes were sampled once a week using CDC light traps from 50 selected houses in each community, thus allowing comparisson of transmission both within and between communities. The mosquitoes were sorted and identified, and a proportion were dissected for parity and infection with W. bancrofti. During the first study year, the density of biting mosquitoes was about three times as high in the high than the low endemicity community. All the three important vector species of W. bancrofti in East Africa were present in both communities, though in different proportions and varying in numbers with the season. The anophelines, Anopheles gambiae and An. funestus dominated in the high endemicity community (above 2/3 of collected mosquitoes), whereas Culex quinquefasciatus dominated in the low endemicity community (above 1/2). The difference in transmission intensity between the two communities was more pronounced, from 10 to 16 times higher in the high than in the low endemicity community. The average number of infective bites per person per year (AIBR) was estimated to 49 in the high and 3 in the low endemicity community. Similarly the estimated number of infective larvae transferred per person per year (ATP) was 100 and 10, respectively. Biting/transmission also varied considerably between houses within each community. These figures are within the variation in transmission along the East African coast. The data will later be compared both within and between the communities and related to the pattern of bancroftian filariasis infection, disease and host response.

Evidence for geographical isolation and potential eradication of onchocerciasis vectors from the island of Bioko

RJ Post

Department of Entomology, Natural History Museum, Cromwell Road, London SW7 5BD, UK, Tel: +44 (0)20 7942 5593, Fax: +44 (0)20 7942 5229, e-mail: [email protected], http://www.nhm.ac.uk/

Cytotaxonomic analysis of the polytene chromosomes from larvae of the Simulium damnosum complex is reported from the island of Bioko in Equatorial Guinea, and a new endemic cytoform is described. Chromosomally it is close to both S. squamosum and S. yahense, but is not identical to either. However, it is morphologically and enzymatically identical to S. yahense. The Bioko form was also found to differ from other cytoforms of the S. damnosum complex in West Africa in the copy number or RFLP pattern of several different repetitive DNA sequences. It is clear that the Bioko form is genetically distinct from other populations of the S. damnosum complex, and whilst it is closest to S. yahense it still shows a high degree of geographical and genetical isolation. Such isolation is an important consideration in the assessment of the potential for onchocerciasis vector eradication on Bioko.

Ivermectin resistance: predictions from the animal health experience

Roger Prichard

Institute of Parasitology, McGill University, Montreal, Canada

Ivermectin resistance is widespread and problematic in the nematode parasite of small ruminants, Haemonchus contortus and also occurs commonly in Teladorsagia circumcincta and occasionally in Trichostrongylus colubriformis in these animals. In nematode parasites of cattle it is becoming more common, being reported in Cooperia oncophora most frequently, but also in H. placei, T. colubriformis and recently in Nematodirus spp. While ivermectin resistance in nematodes of sheep and goats has been found in most countries in which the anthelmintic has been used extensively and the problem investigated, ivermectin resistance in cattle nematodes has so far only been reported in New Zealand, England, Argentina and Brazil. The genetic basis of ivermectin resistance has been investigated in H. contortus, C.

oncophora and the free living nematode, Caenorhabditis elegans. Recently we have

compared Oncocerca volvulus from patients with a history of several ivermectin treatments, with O. volvulus from ivermectin näive patients. The filarial worms from ivermectin treated patients had altered genetic polymorphism, compared with the unselected filarial worms, in the same gene homologs that we find associated with ivermectin resistance in H. contortus, C.

oncophora and C. elegans.

ANTIBODY RESPONSES SPECIFIC FOR WOLBACHIA SURFACE PROTEIN