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Seventeen male and 39 female Liberian patients, one third of them children, were diagnosed as having hyperreactive onchodermatitis (sowda). They presented with itching (98%), asymmetric (98%), chronic onchodermatitis (median 5 years), and swelling of femoral lymph nodes (89%). The geometric means of the microfilaria (mf) densities were 1.0 mf/mg in children and 0.7 mf/mg in adults. These patients not only suffered from their skin lesions, and severe itching resulting in disturbance of sleep but also from social stigmata. They urgently needed treatment. Ivermectin was administered as a single oral dose of 150 micrograms/kg body weight. The following adverse effects were observed in 30 patients within the first 72 hours after ivermectin treatment: increase of pruritus (93%), aggravation of dermatitis (73%), fever (25%), headache (20%), myalgia (20%), painful swelling of lymph nodes (13%) and severe swelling of arm or leg (10%). Symptomatic therapy was sufficient. No dangerous or life-threatening side effects were observed. At follow-up examinations 1-2 months after ivermectin treatment, the prevalence of mf carriers had decreased from 100% to 19%. Seventeen out of 18 patients felt their dermatitis had improved. Evaluation of the dermatitis by a physician using a score from 0 (no dermatitis) to 9 (severe dermatitis) revealed a reduction of the score from 4.3 before treatment to 0.7 (84%) after ivermectin. In contrary, at the follow-up examination of 16 patients 6-12 months after ivermectin some recrudescences were observed. In this group the prevalence of mf carriers was 47%, 13 out of the 16 patients felt their skin lesions had improved and the score had decreased from 2.2 to 0.5 (77%). Consequently, it is recommended to administer ivermectin to patients with hyperreactive onchodermatitis every 3-4 months.

Ivermectin is a potent microfilaricide that also blocks microfilarial release while albendazole is toxic to all intrauterine stages. We investigated whether their combination would permanently sterilize the adult worms. In the first open phase, all 69 patients received 150 micrograms/kg of ivermectin. In the second double-blind phase one week later, 35 patients were randomized to receive 800 mg of albendazole with a fatty breakfast for three consecutive days while 34 patients received matching placebo tablets. Detailed clinical and laboratory examinations were done before treatment and were repeated at intervals over one year. Nodules were excised at three and six months. There was a rapid reduction in skin microfilariae, maximal at four weeks (99.9%). Counts increased subsequently and were between 11 and 18% of initial values at one year. Nodule histology showed no macrofilaricidal activity of the combination. A high proportion of the stretched intrauterine microfilariae were degenerate in both groups. Anterior chamber microfilarial counts were unchanged until day 18 and then fell successively. Low levels persisted in several patients at one year. Dead corneal microfilariae and corneal punctate opacities increased initially, fell with time and then disappeared in most patients. Systemic and ocular reactions were mild to moderate and biochemical abnormalities were minor. A pronounced posttreatment eosinophilia subsided by day 30. There was no significant difference between the two groups in clinical and laboratory tolerance or in alterations in skin and ocular parasites and no important differences in the effect on the adult worms. The combination of ivermectin with albendazole given one week apart is well tolerated but produces no additional effect against Onchocerca volvulus when compared to ivermectin given alone.

Ivermectin is the drug of choice for the treatment of onchocerciasis. However at the recommended dose of 150 micrograms/kg, it neither kills nor permanently sterilises the adult worms. We investigated whether high doses given with and without a preceding 150 micrograms/kg 'clearing' dose would be tolerable as well as effective against the adult worms. Seventy-five healthy males with moderate to heavy infections with Onchocerca volvulus were enrolled in a double-blind trial to receive one of the following treatment regimens: 150 micrograms/kg followed by placebo (9 patients); 400 micrograms/kg with (9 patients) or without (16 patients) a clearing dose; 600 micrograms/kg with (8 patients) or without (16 patients) a clearing dose and 800 micrograms/kg with (8 patients) or without (9 patients) a clearing dose. Detailed examinations were conducted before and at various times after treatment. A preliminary report on the clinical and laboratory safety as at 30 days is presented. All the regimens were well tolerated. No clinical or laboratory drug related effects were observed. The overall severity of the Mazzotti reaction was similar in all groups. Ocular reactions were minimal and there were no changes in ocular function or in fluorescein angiograms. The groups were similar in the extent of microfilaricidal activity; there was however a suggestion that microfilariae were killed more rapidly at 400 micrograms/kg and 600 micrograms/kg but not at 800 micrograms/kg. This needs further study. Single doses of ivermectin up to 800 micrograms/kg are well tolerated; no special precautions for treatment monitoring are required and a 'clearing' dose is not necessary.

A survey for the prevalence, geographical distribution and clinical manifestations of onchocerciasis was conducted on the Island of Bioko (formerly Fernando Póo), Equatorial Guinea, between 1987-89. The whole population (1799 inhabitants) of thirteen villages distributed around the island was surveyed. Identification data, physical examination and Snellen "E" test for visual acuity were performed. Skin snips were taken from both iliac crests and right scapula and calf. Differential diagnosis between Onchocerca volvulus and Mansonella streptocerca was carried out in both fresh and Giemsa stained preparations. The overall prevalence (+ skin snips) and mean microfilarial density were 75.2% (range 51.9% to 87.1%) and 32.2 mf/snip respectively. Skin snips showed a higher microfilarial density from iliac crests. The following clinical manifestations were found: 560 (31.2%) with nodules; 518 (28.8%) with dermatitis, pigmentation changes and cutaneous atrophy; 753 (41.9%) with lymphoadenopathy and lymphoedema. Blindness due to different causes was registered in 13 cases (0.8%). The results showed that onchocerciasis is hyperendemic and widespread over the island. It is estimated that almost the whole population (62,000) is at risk of infection.

We report the clinical and parasitological effects of a modified treatment regimen for suramin. Twenty adult males received up to 5 g (72.5 to 84.7 mg/kg) of suramin over 36 days. Detailed clinical and laboratory examinations were done before treatment and then at intervals over 2 years. Nodules were removed at 6, 13, 26 and 52 weeks for histology. Systemic tolerance was good. Anterior segment inflammation was however common and 2 patients required intervention to prevent posterior synechiae. No new posterior segment lesions developed; a rare improvement occurred in one patient with papillitis. Proteinuria, mostly mild, occurred in nearly all patients. Previously unreported renal glycosuria was documented in one patient. Microfilariae in the skin and anterior chamber did not change significantly for 5 or more weeks after which rapid reductions occurred. Ocular parasites were absent at 2 years and skin microfilariae were near zero. Peripheral blood eosinophil counts fell in parallel with those of microfilariae in the skin and anterior chamber and were normal at one and two years. These findings at 2 years may provide indirect evidence of a macrofilaricidal or a permanent chemosterilant effect on the adult worms. Nodule examination revealed an embryotoxic effect from week 6, a lethal effect on the male worms from month 3 and on the female worms from month 6 after treatment started. At one year 34% of the female worms examined were alive. Thus total doses of suramin in the range 72.5 to 84.7 mg/kg have only a modest lethal effect on the female worms. Suramin remains a restricted drug and a suitable replacement is urgently needed.

Larvae of Simulium damnosum complex collected from rivers draining Tukuyu onchocerciasis focus were chromosomally examined. Of the 970 larvae analysed, 910 were identified as Kiwira form, a newly described cytotype found in all S. damnosum larval habitats in the Tukuyu area, while 51 were classified as a new subpopulation, tentatively named as Kasyabone form. The F1 larval progeny obtained from wild caught human biting S. damnosum and reared in the laboratory were chromosomally examined. 509 F1 larvae from 70 females blood fed on human volunteers were identified as Kiwira form. As the main human-biting member of the complex in the Tukuyu area, and because some of the wild caught females had developing filarial larvae indistinguishable from those of Onchocerca volvulus, Kiwira form is thus incriminated as the local vector of onchocerciasis. These observations are discussed with respect to previous literature.

We studied the prevalence of human onchocerciasis in four geographically different regions of the southern part of Benin in West Africa. In a total of thirteen villages 1596 individuals were examined for clinical and parasitological signs of onchocerciasis. Prevalence of microfilariae of Onchocerca volvulus in skin snips was 29% in region I (lower Oueme river), 64% in region II (Mono river), 56% in region III (upper Oueme river) and 70% in region IV (Okpara river). Based on endemicity criteria of the WHO regions II and IV were found to be hyperendemic, region III mesoendemic and region I hypoendemic for onchocerciasis. The community microfilarial load ranged from 4 mf/mg skin in the hypoendemic region to 10.5 mf/mg skin in the hyperendemic regions. The prevalence of nodules was 21% in region I, 30% in region II, 17% in region III and 41% in region IV. The overall prevalence of chronic onchocercal dermatitis was 12%. Of 689 individuals infected with O. volvulus 388 were treated with a single dose of ivermectin.