[Human onchocerciasis and "sowda" in the Republic of Yemen]. / Onchocercoses humaines et "sowda" en République du Yémen.

The geophysics of the north Yemen, associating a north-south directed mountainous fish bone (rising in more of 2,000 meters), to numerous rivers or "wadis" is convenient to the development of simulium shelters, main vectors for cutaneous filariasis to Onchocerca sp. Following several missions of bio-clinical and epidemiological evaluations in neighbouring villages of wadis, it has been possible to study different clinical aspects: one reminding the classical african onchocerciasis with generalized and diffused dermatitis, and, on an other hand, a hyperreactive dermatitis on one side of the body and associated with a collateral lymphatic ganglion. This disease is well known for local populations as "aswad" meaning "black" or "sowda". Clinically whatever the studied focus, coexists the two types of onchodermatitis (uni or bilateral). Yhe sowda patients are proportionally less numerous than those touched by the generalized type. Frequent eye lesions of the West African onchocerciasis are not found in sowda cases. In classical optical microscopy, microfilaria is morphologically indifferenciable between sowda and onchocerciasis clinical aspects. Skin snips were carried out on patients of both groups. Identification of microfilaria by molecular biology through the study of the DNA genome was done out of 5 skin snips. Microfilaria was kept dry between laminas and the DNA extracted from rehydrated microfilaria. DNA was intensified with specific primers of Onchocerca type (O150PCR). This phase was followed by hybridisation of amplification products by PCR to specific stains: OVS-2 for Onchocerca volvulus species, OCH for Onchocerca ochengi, PFS1 and PSS1-BT respectively for the forest strain and the savannah strain of Onchocerca volvulus as described previously. We can distinguish 2 kinds of answers based on the clinical origin of the snip-tests: the first one concern 3 patients with numerous dermal microfilariae but without any clinical sowda and corresponding to microfilaria O. volvulus type but different from the forest or savannah strains found in sub-Saharan Africa. The second one corresponds to 2 patients with less than 5 microfilaria in their snip-test. They show the typical clinical picture of sowda. They are identified as microfilaria type Onchocerca but they do not belong to species volvulus, or to species ochengi. It seems quite probable that the clinical picture of sowda be the result of developing onchocerciasis of animal origin and not identified as to day. The ivermectin, therapeutic of choice for African onchocerciasis in annual unique cure seems less effective in the coverage of sowda. In that case rehearsal of cures every 3 months would be necessary for mass campaigns to limit the transmission of this filariasis.

Short- and long-term action of multiple doses of ivermectin on loiasis microfilaremia.

One hundred nine Gabonese patients infected with Loa loa microfilariae were treated with ivermectin (200 microg/kg of body weight) at the Parasitology, Mycology and Tropical Medicine Department (Faculte de Medecine et des Sciences de la Sante, Libreville, Gabon). Each was given one dose per month for six consecutive months. The peripheral blood microfilaria (mf) count before and after each dose showed an average decrease in the microfilaremia of 87.3% (short-term-single dose). An annual single-dose mass treatment with 200 microg/kg of ivermectin was sufficient to control the parasite in populations with low (< 400/ml) L. loa mf counts. One month after the sixth dose (short-term-multiple doses), the average microfilaremia rate had decreased by 99.2% compared with the initial infection (35 patients). Samples were taken from 28 patients one month after the first dose and one month after the sixth dose. The average mf count decreased by 96.4% after the first dose and by 99.6% after the sixth dose (average residual mf counts = 13.7 and 1.5 mf/ml, respectively). The mf count after the sixth dose was only 11.2% of the count after the first dose. The low mf count persisted for more than six months after the sixth treatment (long-term-multiple doses). Thus, mass treatment with multiple doses is more appropriate for areas where the blood mf count is very high. These results show that the number of the annual treatments used in mass chemotherapy with ivermectin can be adapted to each population to provide efficient protection.

Reduced Loa loa microfilaria count ten to twelve months after a single dose of ivermectin.

The action of a single dose of ivermectin (200 micrograms/kg) on 71 Gabonese patients with Loa loa microfilariae in the peripheral blood, and living in areas highly endemic for loiasis, has been evaluated. Ten to 12 months after treatment, 43 patients (63%) had no circulating microfilaria and the geometric mean peripheral blood microfilaria count had decreased by 88.6% (P < 0.02). Thus, a single annual dose of ivermectin can markedly reduce loiasis transmission.

[Onchodermatitis (sowda) in patients in Yémen. Clinical and histologic course after treatment with ivermectin]. / Onchodermatite (Sowda) chez des patients du Yémen. Evolution clinique et histologique après traitement par ivermectine.

Sowda skin lesions are of medical and social importance in Yemen. Ivermectin (Mectizan) chose as a control strategy plan in onchocerciasis is active during 3 months for the less on clinical and histological data. After a short increase of itching and oedematous skin aspects clinical signs decrease. Some patients notice an itching rebound after 90 days. Histologically, localized ingratiates, presence of mononuclear cells and melenin loaded histiocytes and eosinophils decreased. The rythm cure has to be studied on a longer period but 3 to 6 months repetition between oral treatment with 200 micrograms/kg dose during two years could be effective.

Ivermectin treatment of mansonellosis in Blanchisseuse, Trinidad, West Indies - abstract

The first double-blind-placebo field trial, using the drug ivermectin to control M. ozzardi microfilariae, was conducted in Blanchisseuse, North Trinidad. A preliminary trial indicated that there were no major constraints in administering the drug ivermectin within the community. In 16 patients before treatment, the microfilariae density ranged from 1 to 5,679 mf/ml, and the geometric mean was 697 mf/ml compared to 4 to 2,042 mf/ml and 362 mf/ml in the 14 patients given the placebo. Following treatment 87.5 percent (14/16) experienced side effects including fever and arthralgia (12 cases), myalgia (3 cases), headaches (11 cases) and chills (8 cases). All symptoms disappeared after 24 hours. Twenty-four hours after the ivermectin treatment the M. ozzardi microfilariae densities significantly (p < 0.001) declined to zero in 11 out of 16 cases (68.8 percent) while in 5 cases densities declined by > 95 percent. One week post-treatment there were no microfilariae observed in 93.8 percent (15/16) of cases, with one patient not attending the clinic. Blood samples collected 1 and 5 months after ivermectin treatment revealed M. ozzardi microfilariae in 3 patients. These 3 patients were re-treated with 6 mg of ivermectin, but two patients demonstrated persistent parasitaemias in subsequent blood samples. Within the placebo group, fluctuating levels of microfilariae were observed (AU)

Combination ivermectin plus diethylcarbamazine, a new effective tool for control of lymphatic filariasis.

In 1993, a three arm double-blind controlled trial was implemented in French Polynesia, to compare the tolerance and efficacy of single doses of the combination ivermectin (IVR) 400 micrograms.kg-1 plus diethylcarbamazine (DEC) 6mg.kg-1 vs IVR 400 micrograms.kg-1 or DEC 6 mg.kg-1 alone, for treatment of Wuchereria bancrofti carriers. Of the 57 treated male patients in whom microfilaremia (mf) densities ranged from 22 to 4,709 mf/ml, three groups of 19 were randomly selected, and allocated to one of the three treatments. Twelve months after treatment 37%, 16% and 16% of patients were mf negative in groups DEC, IVR and IVR plus DEC respectively. Mf percent return to pretreatment level was significantly lower in the group IVR + DEC (1.9%) than for DEC 6 (14.7%) or IVR 400 (11.6%). Antigenemia percent return to pretreatment level was lower in the groups IVR + DEC or DEC 6 than for IVR 400. The combination IVR + DEC proved to be the most effective on macrofilariae and microfilariae (antigenemia and mf negative patients). The combination will be a very powerful tool for control of lymphatic filariasis. An annual filariasis day could be the most cost-effective strategy for administration of the drugs.

Treatment of Strongyloides stercoralis infection with ivermectin compared with albendazole: results of an open study of 60 cases.

Ivermectin is highly effective against animal intestinal nematodes and is used in the treatment of onchocerciasis in humans. A study was undertaken to compare the efficacy of the drug with that of albendazole in the treatment of uncomplicated strongyloidiasis. Sixty patients with confirmed Strongyloides stercoralis infection were enrolled in an open randomized study and given either albendazole, 400 mg/d for 3 d or ivermectin, 150-200 micrograms/kg in a single dose. Efficacy and tolerance were evaluated on days 7, 30 and 90. Each visit included a parasitological examination of 3 stool specimens, using saline and Kato smears and formalin-ether and Baermann concentrations. Fifty-three patients were eligible for evaluation. Parasitological cure was obtained in 24 of the 29 patients treated with ivermectin (83%) and in 9 of the 24 patients who were given albendazole (38%); ivermectin was significantly more effective than albendazole (P < 0.01). Clinical and biological adverse reactions were negligible in both treatment groups. The 20 patients who failed therapy were given a second treatment course with 150-200 micrograms/kg of ivermectin in a single dose or on 2 consecutive days. Sixteen patients were cured and the other 4 had only incomplete follow-up. Ivermectin therefore constitutes an acceptable therapeutic alternative for uncomplicated strongyloidiasis.

A randomized trial of ivermectin versus albendazole for the treatment of cutaneous larva migrans.

In an open study, we compared the efficacy of single doses of oral ivermectin (12 mg) and oral albendazole (400 mg) for the treatment of cutaneous larva migrans. Twenty-one patients were randomly assigned to receive ivermectin (n = 10) or albendazole (n = 11). All patients who received ivermectin responded and none relapsed (cure rate = 100%). All but one patient in the group receiving albendazole responded, but five relapsed after a mean of 11 days (cure rate = 46%; P = 0.017). No major adverse effects were observed. We conclude that a single 12-mg dose of ivermectin is more effective than a single 400-mg dose of albendazole for the treatment of cutaneous larva migrans.

[The efficacy and tolerance of ivermectin (Mectizan) prescribed for the patient with multiple filarial infections (Loa loa/Onchocerca and/or M. perstans)]. / Efficacité et tolérance de l'ivermectine (Mectizan) prescrit chez le sujet multifilarien (Loa loa/onchocercose et/ou M. perstans).

Administration of ivermectin (Mectizan) in Loa loa filariasis induces a significant decrease of microfilaria load within 3 to 15 days. The excellent tolerability of the drug in patients infested simultaneously by O. volvulus and Loa loa allows to use ivermectin in mass treatments in geographical areas where the same patients can be affected by several filariasis. There is almost no efficacy against Mansonella perstans. A second administration one month after the first one in Loa loa affected patients has not led to a complete disappearance of microfilaria; the tolerability has still been good. Efficacy on Ascaris lumbricoides appears to be excellent; further studies are necessary in the cases of trichuriasis, ancylostomiasis and strongyloidiasis.

Ivermectin in loiasis and concomitant O. volvulus and M. perstans infections.

Two clinical studies were carried out in Gabon, Africa to evaluate the efficacy, safety, and tolerability of ivermectin in the treatment of patients with Loa loa infection. In the first study, 35 patients received single oral doses of ivermectin, 5-200 mcg/kg body weight. Blood microfilariae levels did not decrease after a single oral 5, 10, 30, or 50 mcg/kg dose of ivermectin, but levels did decrease after doses of 100, 150, and 200 mcg/kg. The most efficacious dose was 200 mcg/kg; mean blood microfilariae levels decreased to 12% of mean pretreatment values by day 15 and remained decreased for 28 days. A second study evaluated the safety and efficacy of ivermectin in patients with multifilarial infections. All 17 patients had concomitant Loa loa and O. volvulus infection. M. perstans affected 5 of the patients. Sixteen patients also had infections due to intestinal nematodes. The patients each received single oral doses of 200 mcg/kg ivermectin. Ten days later, the mean Loa loa blood microfilariae level had decreased to 20% of the mean pretreatment level. O. volvulus dermal microfilariae densities were reduced to 2% of the pretreatment levels. A minimal increase in blood microfilaria levels was observed on day 28. In contrast, dermal microfilariae levels remained near zero for the duration of the study. Intestinal infection due to Ascaris was eradicated in all of the affected patients by day 23; efficacy against Trichuris and hookworm infections, however, was poor. All patients tolerated ivermectin well including those with multiple infections.

Infection with hepatitis A and B viruses in French volunteers working in tropical Africa.

The risks of developing hepatitis A and B virus infections were studied in 233 French volunteers working for 18 to 35 months in the field in West and Central Africa. During their stay in Africa, the seroconversion rates to antibody to hepatitis A virus of the immunoglobulin G (IgG) class and hepatitis B marker(s) were 48.1% and 10.5%, respectively; 21.5% of the volunteers developed jaundice, and 78.0% of the jaundice cases were associated with hepatitis A seroconversion, 14.0% with hepatitis B seroconversion, 4.0% with seroconversion to both, and 4.0% without seroconversion. Male health workers were at lower risk than other male occupations for hepatitis A infection. Female health workers were at higher risk than other female occupations for hepatitis A infection. Health workers were at a lower risk of hepatitis B infection, but the significance was borderline. Populations such as these volunteers should receive immunoprophylaxis against hepatitis A and B infections.