[Malaria morbidity and therapeutic efficacy of antimalarials. Study conducted in the Dakar region]

During November and December 1992, the authors surveyed the malaria morbidity and the drugs efficiency in an urban area of Dakar region. Malaria represented 13.68% of the fevers in Dakar district and 12.4% in Pikine. The mean parasitic density was evaluated at 5000/mm3. Good efficiency of antimalarial drugs were noted but chloroquine-resistance is present with 24% of prevalence.

[Cholera in Benin (epidemic of 1991)]

Authors report on epidemiologic, bacteriology and therapeutic data related to 1991 cholera outbreak in Benin in the general context of the 7th world pandemic. 7474 cases were notified from all over the country. Vibrio cholerae 01, El Tor biotype, was identified in many patients stools and in the surroundings. Control measures implemented in this situation are described: early parenteral and mainly oral rehydration, antibiotic treatments for patients and contacts, systematic home control around cases, wells disinfection and general hygiene promotion, mobilization of the Civil Service Authorities and population education. Authors conclude that strict epidemiologic monitoring is necessary in epidemic circumstances as well as during endemo-sporadic period.

[Malaria in the Saharan region of Senegal. 1. Entomological transmission findings]

An 18 months longitudinal survey on the entomological aspects of the transmission of malaria has been carried out in a village practising rice field irrigation and in another village with traditional rain water agriculture. Both are located in the Sahelian area of the Senegal river central valley, in Senegal. The study is based on mosquito samples caught on human baits. The vectors A. arabiensis and A. gambiae could be found all year long in the village with rice field irrigation, but only during the rainy season in the other village distant from the rice field area. The average aggressive density decreases with the remoteness from the rice field area. From 16 bites/man/night (BMN) in the rice field area, it decreases to 7 BMN at 500 m and to 1 BMN at 5 km distance. The malaria transmission rate is weak and was not perceptible in the villages located far away from the rice field area. In the village close to the irrigated rice field, only one infected A. gambiae s.l. has been caught during the period of study. Physiological age is higher in the rice field area, but the anthropophilic index is lower. The different parameters involved in malaria transmission show important seasonal and yearly variations. Irrigation has, on the whole, increased mosquito population densities and particularly that of A. gambiae s.l., but malaria transmission does not seem to be influenced by this increase.

[Malaria in the Saharan region of Senegal. 2. Parasitological indices]

The malaria parasitological indexes have been studied in three villages situated in the Senegal river central valley. Near one of them an irrigated rice field has been operational since July 1989. Each village has its own health care unit and the consumption of antimalarial drugs, especially chloroquine, is important. The parasitological indexes in children 0 to 9 years old and in patients presenting with symptoms evocative of malarial attacks are low. Irrigation of the rice field area does not seem to be an increasing factor for the malaria parasite rates in the area.

[Evaluation of the efficacy of fenitrothion (Sumithion PM40) on vector density and the prevalence of malaria in Pout (Thiès, Sénégal)]

House-spraying with fenitrothion for malaria control was evaluated in three villages of the Pout rural community (Senegal) between August 1988 and October 1990. The baseline data were collected during the first year. The malaria vector was identified as Anopheles arabiensis and the highest malaria prevalence was observed in October 1988 (38%) in the child population (2-9 years old). A simple round of fenitrothion house-spraying at 1 g/m2 was carried out in the second part of July 1989. About 90% of the houses were treated. The malaria vector was reduced to negligible density and a rapid decrease of malaria prevalence was observed. In this area of short seasonal transmission, where the stability of malaria is low, one single round of spraying led to a marked reduction of malaria transmission and prevalence. The cost of the treatment was about 50 US cents per capita.

[Fungi in the hospital environment and infectious risk]

Using petridishes at hospital in services with risk patients, we have isolated Aspergillus (41.5%), Penicillium (26.4%), Candida (12.2%), Fusarium (7.5%), Mucorales (5%), Scopulariopsis (5%), Scytalidium (0.8%), Tricothecium (0.8%), Ulocladium (0.8%). Several fungi grew at 37 degrees. These saprophytic fungi could give opportunistic mycoses in immunodeficient patients.

Determinants of vaccination in an urban population in Conakry, Guinea

A community survey was conducted in 1989 in Conakry, Guinea to determine reasons for low vaccination coverage. Some 377 children aged 12-23 months and their guardians were studied, of whom 204 (54%) had vaccination records. According to their records 19% of children were fully and correctly vaccinated. Thirty-nine incompletely vaccinated children (19% of those with records) had sufficient documented contacts with health services to be fully vaccinated, but at least one immunization opportunity was missed. Multivariate analyses were conducted to identify factors associated with receipt of first dose diphtheria/pertussis/tetanus/oral polio vaccine (DPT/OPV) and with completion of the DPT/OPV series. Factors determining initiation of the series included maternal education (assessed by ability to speak French), household possession of a television, maternal age less than 35 years, child's birth in hospital, and, for non-French speakers, the mother considering vaccination to be affordable. Factors determining completion of the DPT/OPV series, among children who began vaccination, included maternal education, employment, and past positive experience with vaccination services (short waiting times, not having been turned away from vaccination, and not knowing a child with a post-vaccine 'abscess'). Vaccination coverage can be substantially increased in Conakry by improving health services to avoid missed opportunities, following the vaccination schedule correctly, reducing waiting times and avoiding abscesses.

Obstacles to achieving immunization for all 2000: missed immunization opportunities and inappropriately timed immunization

Missed opportunities and inappropriately time immunization substantially reduced the coverage achieved in Mozambique and Guinea Conakry. During coverage surveys in Mozambique, we noted dates of attendance at a health facility for growth monitoring or vaccination, and in Conakry we also abstracted dates of curative care visits from home-based documents. In Mozambique, an average of 84 per cent of children aged 12-23 months had documents, and an average of 53 per cent of children were fully and correctly vaccinated. Among children with cards, 11 per cent had received all vaccines, but at least one dose was applied before the recommended age or with too short an interval between doses (inappropriately timed vaccinations). A further 8 per cent of children had sufficient documented contacts with preventive services to be fully vaccinated, but immunization opportunities had been missed. In Conakry, 54 per cent of 12-23 month-old children had immunization cards, and only 19 per cent were fully and correctly vaccinated. Among children with cards, 9 per cent had received all vaccines, but some were inappropriately timed, and 19 per cent had enough contacts with curative or preventative services to be fully vaccinated, but opportunities had been missed. We recommend that home-based records document all health centre visits, including those for curative care, and that missed opportunities and vaccination timing be routinely evaluated during vaccine coverage surveys.

[The emergence of chloroquine-resistant malaria in Dakar, Senegal]

In October and November 1988 we carried out in vivo Plasmodium falciparum sensitivity tests for chloroquine in the town of Dakar, where malaria is endemic with increased transmission during the rainy season (July to October). 25 mg/kg/p.c of chloroquine has been administered to 35 patients on three consecutive days, according to the WHO protocol. Clinical and parasitological controls were carried out on D1, D2, D3, D4, D7 and D14. We observed two therapeutic failures: one on D7 among the 32 patients examined during that period, and one on D14 among the 24 patients who were present at control. The important drug pressure and population movements in Dakar are sources of chloroquine resistance which should receive special attention in terms of control and surveillance of this emerging problem.

Application of multiple methods to study the immunization programme in an urban area of Guinea

During 1988-89, studies were conducted to evaluate the immunization system in Conakry, Guinea. The first, a health facility survey, found that health staff screened the vaccination status of only 30% of children who presented for curative care. A sterile syringe and needle were used for less than half of the injections. In the second survey, key informant interviews with vaccinators and health centre chiefs showed that there were minimal lines of communication between health workers and the community, but that health workers did not perceive this to be a problem. Focus group discussions in the community revealed a high level of general knowledge about vaccine-preventable diseases. However, mothers did not know how many vaccinations their children should receive or by what age they should be completed. They complained of long waiting times in health centres, the high costs of vaccination, poor rapport with health workers, and the occurrence of abscesses after vaccination. The final study, a "knowledge, attitudes, and practice" community survey, showed that missed immunization opportunities and inappropriately timed vaccinations reduced potential vaccine coverage by almost 30% among children with vaccination cards. Higher socioeconomic status, delivery in hospital, and whether mothers perceived the vaccinations to be affordable affected whether the child began the immunization series. Once a child had entered the immunization system, completion of the series was determined by the mother's education level, employment status, and experience with vaccination services.

[Malaria morbidity in the urban environment. Study of 353 fever attacks]

The authors make a study of malaria morbidity in Dakar during October and November 1988 in Dakar where malaria is endemic but with a pick in pathophoresis during the rainy season. Out of 353 surveyed cases of malaria, 110 were carriers of Plasmodium falciparum, i.e., 31%. Mean parasitic density was 7462 red cells/mm3 and more than an half of patients got an higher density. Parasitic density was higher in children (0-14 years old) than in adults, but with no significant indication. Malaria fever represents 20.4% of all types of fever observed and was the first cause to consult during the rainy season. Whatever threshold of parasitic density selected parasitologic criterion may be in order to identify a malaria fever, percentage of diagnosis misinterpretation linked up to clinical examination was always higher than 30%.

[Malaria morbidity in rural and urban areas in Senegal]

During September and November 1987, the authors surveyed the incidence of malaria fever in populations of a rural zone in Casamance and in adults as outpatients in an urban area. In these regions, the malaria is endemic with a recrudescence during the rainy season from July to October. In rural zone, 169 persons were examined. The malaria fevers represented 7.1% of the consultations and 23.3% of fevers. Differences were significantly observed between the parasitic densities of febrile and afebrile patients.

A double-blind comparison of the efficacy and safety of ivermectin and diethylcarbamazine in a placebo controlled study of Senegalese patients with onchocerciasis

Ivermectin (MK-933) has been compared with diethylcarbamazine (DEC) and placebo in a double-blind study in 30 adult male Senegalese patients with Onchocerca volvulus infection. 10 patients were randomly assigned to each treatment group. Ivermectin was administered as a single oral dose of 12 mg and DEC as 50 mg daily for two days and 100 mg twice daily for the following six days, total 1.3 g in eight days. Skin O. volvulus microfilaria densities remained near pre-study values in the placebo patients, but decreased rapidly with both active drugs to mean values about 2% of pretreatment (Day 8) and then increased slowly, reaching in 12 months about 4% of pre-treatment (ivermectin) and 18% (DEC). This difference is statistically significant. Clinical adverse reactions were recorded in four ivermectin, ten DEC and three placebo patients. One ivermectin and six DEC patients received steroid treatment for relief of these reactions. Serious adverse ocular changes were not seen in any patients, possibly because of the steroid therapy in the DEC patients. Adult O. volvulus from onchocercal nodules one and six months after treatment showed no effect of either drug on viability. Intra-uterine developing forms of the microfilariae appeared normal in all three treatment groups at the one month examination but deformed and degenerated forms were evident at six months in the ivermectin group but not in the DEC and placebo patients. Ivermectin as a single oral dose appears to be a safer and more effective microfilaricidal drug in human onchocerciasis than DEC in the standard multi-dose regimen.

[Management in Senegal of the 1st efficacy and tolerability studies of ivermectin (MK 933) in human onchocerciasis]

In 1981, 32 adult Senegalese males infected with Onchocerca volvulus but without ocular involvement were treated by groups of 8 with single oral dosages of 5, 10, 30 or 50 micrograms/kg of ivermectin . As soon as the second day after treatment, we observed a marked decrease of the dermal microfilaremic charge after a posology of 30 micrograms/kg. However the decrease is most important in the group subjected to 50 micrograms/kg and 75% of them had no more microfilariae in the dermis 28 days following treatment.

Efficacy and tolerance of ivermectin in human onchocerciasis

Initial clinical studies in 32 Senegalese subjects have demonstrated the efficacy of ivermectin in Onchocerca volvulus infection (river blindness). Although O. volvulus microfilariae in skin snips were not reduced in number after single oral doses of 5 micrograms or 10 micrograms/kg body-weight, they were greatly reduced in all subjects after single oral doses of 30 micrograms or 50 micrograms/kg and were eliminated completely in 6 of th 8 subjects who received the 50 micrograms/kg dose. All subjects tolerated the drug well. Transient pruritus which did not require treatment was observed on the day the dose was given in 2 of the 8 subjects after the 30 micrograms/kg dose and in 4 of the 8 who received the 50 micrograms/kg dose. Ivermectin produced no abnormal laboratory results.

Hepatitis-B virus in bedbugs (Cimex hemipterus) from Senegal

Bedbugs of the species Cimex hemipterus (F) were collected on four separate occasions from the bedding in the huts of village dwellers in Senegal, West Africa. Hepatitis-B surface antigen (HBSAg) was detected in unengorged nymph and adult bedbugs in each of the first three collections. 3 of 28 such specimens were HBSAg(+) in the first collection and 3 of 17 specimens were positive in the second collection. In the third, 6 of 9 were HBSAg(+) when the bed occupant was known to be HBSAg(+). 2 of these 6 positive insects did not contain human serum proteins. Bedbugs in the fourth collection were captured and kept alive without a blood meal for 30 days. 3 of 89 of these samples were HBSAg(+). These are the highest field infection-rates of hepatitis-B virus reported in any insect species. The bedbug must be considered a potential vector of hepatitis-B virus.

Leishmanin skin sensitivity in the inland delta of the Niger

Leishmanin skin tests were applied to 266 subjects in the city of Mopti which is located on several islands in the center of the inland delta of the Niger in the Republic of Mali. The antigen employed contains 6-10 million killed leptomonads per ml in a sterile suspension preserved with 1:10,000 thiomersal and unlike the phenol suspended antigens, does not give false positive tests. Of the 249 subjects who completed the study 12 (4.8%) had positive reactions, the lowest positive reaction rate yet observed in Mali. No false positive reactions occurred among 139 subjects tested with a control solution of 1:10,000 thiomersal. The absence of known cases of cutaneous leishmaniasis in Mopti's permanent population and the absence of suitable vectors within the city would indicate that positive reactors reflect previous L. tropica infections acquired in the surrounding rural areas where the disease is known to exist or else previous infection with non-pathogenic mammalian or reptilian species of Leishmania.