The risk of optic atrophy following suramin treatment of ocular onchocerciasis*

BRIEF COMMUNICATIONS Buletin of the World Health Organization, 57 (3): 479-480 (1979) The risk of optic atrophy following suramin treatment of ocular onchocerciasis * B. THYLEFORS1 & A. ROLLAND2 Abstract Treatment of onchocerciasis with suramin in an area of vector control led to an increased incidence of optic atrophy in treated patients compared to an untreated group. Suramin has been used a great deal in the treat- ment of onchocerciasis. It is known to be an efficient though unsafe macrofilaricide and it also has a slow microfilaricidal action (4). Its effects on the ocular lesions of onchocerciasis have been investigated (1-3, 5), but there is still uncertainty concerning the incidence of posterior segment lesions, especially optic atrophy, during puramin treatment. Methods In 1975, treatment of onchocerciasis with suramin was undertaken in a village situated within the Onchocerciasis Control Programme area in the Vol- ta River Basin. Suramin was given as weekly injec- tions at a total dose of 5.2 g to 25 heavily infected patients. A comparable group of 23 untreated in- fected patients was also examined. Ophthalmological and parasitological examina- tions of the two groups were carried out before treatment in 1975 and similar post-treatment fol- low-up examinations were made in 1978, i.e., after a 3-year period during which the entomological results from the area indicated an almost complete inter- ruption of the transmission of Onchocerca volvulus. The ophthalmological examinations were carried out in a darkroom with a slitlamp and direct or indirect ophthalmoscopy of the fundus. Only certain oph- thalmological aspects of the results are discussed here, the complete analysis being presented else- where (7). * From the WHO Onchocerciasis Control Programme in the Volta River Basin Area, B.P. 549, Ouagadougou, Upper Volta. 1 Ophthalmologist. 2 Consultant Ophthalmologist. Results Table 1 summarizes the number and distribution of patients with irreversible ocular lesions in the two groups. There was a greater number of patients with optic atrophy, as diagnosed by means of ophthal- moscopy, in the suramin group at the follow-up in 1978. In the same group there was no change concerning anterior segment lesions, i.e., sclerosing keratitis and iridocyclitis with synechiae. In the untreated group there was a tendency for deteriora- tion in the anterior segment lesions but there was no change in the posterior segment. It should be noted that fundus examination could not be performed in two cases of anterior uveitis in that group in 1978. All five individuals with optic atrophy in 1978 had apparently normal optic discs in 1975. In two of these cases choroidoretinitis also appeared during the observation period. Table 1. The distribution of cases with irreversible ocular lesions. Optic atrophy is considered the most severe lesion and each case is listed only once accord- ing to the most damaged eye. Group Year Optic Choroido- Sclerosing Iritis +examined atrophy retinitis keratitis synechiae Suramin 1975 1 0 1 0 (Males 11; females 14) 1978 5 0 1 0 Untreated 1975 1 1 1 1 (Males 17; females 6) 1978 1 1 2 3 Discussion Suramin treatment in an area of interrupted transmission has been observed to have a favourable effect on anterior uveitis in onchocerciasis patients (5), and in a 14-15-year follow-up of patients treated with suramin (3) it was found that it had not provoked the appearance of posterior segment le- sions, and that it may even have had a protective influence. 3822 479 480 BRIEF COMMUNICATIONS The hypothesis that chemotherapy of onchocer- ciasis may induce optic atrophy has only recently been put forward (1, 2, 10). The possible presence of microfilariae in the optic nerve has been demon- strated (6), and it is probable that their death within the nervous tissue can give rise to inflammatory reactions and to subsequent optic atrophy. Suramin treatment in a case of bilateral papillitis (9) was observed to give a satisfactory result, but other treatment regimens using diethylcarbamazine (DEC) resulted in several cases of optic atrophy (10). Anderson et al. (1), in their first study of suramin in ocular onchocerciasis, found no signifi- cant difference in the incidence of optic atrophy between treated and control cases. However, their second study (2) indicated that there may be an increased risk of optic atrophy developing in patients with ocular onchocerciasis, even if the schedule currently considered the safest, i.e., an initial DEC course under steroid cover followed by suramin treatment, is used. The present study indicates that suramin treat- ment of ocular onchocerciasis may be associated with a risk of developing optic atrophy. The limited number of cases included does not allow of a reliable statistical analysis, but the findings presented here should stimulate further investigations of the sub- ject. It is possible that suramin, with its partial microfilaricidal effect, may cause slow death of the microfilariae, which would be unfavourable to the optic nerve because of a prolonged period of inflam- matory activity. However, a direct toxic effect of suramin itself cannot be ruled out, nor can the possibility .of an antigen-antibody reaction (8) be excluded. The effects of chemotherapy in patients with onchocerciasis in an area of vector control must be further evaluated. Treatment of the disease under such circumstances may become less imperative because of a decreasing intensity of onchocercal infection with time. REFERENCES 1. ANDERSON, J. ET AL. The effects of suramin on ocular onchocerciasis. Tropenmedizin und Parasitologie, 27: 279-296 (1976). 2. ANDERSON, J. & FUGLSANG, H. Further studies on the treatment of ocular onchocerciasis with -diethylcar- bamazine and suranin. B*itish Journal of ophthalmol- ogy, 62: 450-457 (1978). 3. BUDDEN, F. M. The natural history of ocular onchocer- ciasis over a period of 14-15 years and the effect on this of a single course of suramin. Transactions of the Royal Society of Tropical Medicine and Hygiene, 70: 484-491 (1976). 4. DUKE, B. 0. L. The effects of drugs on Onchocerca volvulus. Bulletin of the World Health Organization, 39: 157-167 (1968). 5. GROUNDS, J. G. The treatment of onchocerciasis with suramin (Antrypol) after vector eradication. East African medical journal, 8: 487-492 (1958). .6. RODGER, F. C. The pathogenesis and pathology of ocular onchocerciasis. IV. The pathology. American journal of ophthalmology, 49: 560-594 (1960). 7. AOuAN, A. ET AL. Bilan aprts trois ans du traite- meat par la sur4wine d'un villagc onchocerquien sous protection entomologique. Revue internationale du trachome, 56 (1979) (in press). 8. TROJAN, H. J. Deg6nerescence des vaisseaux choroi- diens dans l'onchocercose. Revue internationale du trachome, 54: 111-117 (1977). 9. VEDY, J. & SIROL, J. A. A propos d'une papillite onchocerquienne. M6decine tropicale, 31: 559-564 (1971). 10. VEDY, J. ET AL. A propos de sept observations de papillite onchocerquienne. Medecine et arm&es, 10: 851-858 (1975).