[Memisa: from medical missionary action into a medical relief organization]. / Memisa: van medische missieactie naar medische ontwikkelingssamenwerking.

In the past seventy years Memisa Medicus Mundi has grown into an organization accounting for about half the annual number of Dutch health care workers in third world countries. On top of this, it gives financial and material support to many development programmes in Africa, Asia and Latin America. Of all aid, 82% is given to so-called structural programmes and 18% to disaster relief. Physicians who return to the Dutch health care system as general practitioners after a period abroad are capable of efficient practice management.

PIP: The medical mission organization Memisa Medicus Mundi was established in 1925 with the aim of sending missions to tropical countries. One of the main concerns was the high mortality rate of missionaries and, therefore, a 10-week medical-hygienic course was taught in Rotterdam to missionaries before their departure for tropical countries. Since its founding, Memisa accounts for about half of the health care workers who work in developing countries. Most of those who are sent on such missions via Memisa work in rural church hospitals that have 3-4 doctors, 200 beds, and are responsible for the health care of 200,000 inhabitants. With a typical birth rate of 4%, the annual number of deliveries is around 8000, which also means that around 8000 children are vaccinated per year. Only one-third of the women give birth in the hospitals and 5% require a cesarean section. Primary health care (PHC) has been the symbol of health care in developing countries since the Alma-Ata conference of 1978, but PHC has led to substantial improvement of health care only in a few countries because of the national top-down approach in contrast to the requirement of participation of people for success. In 1996 Memisa received 1820 requests for assistance. 82% of the funds supported structural programs and 18% went to disaster relief. In 1996 a total of 135 doctors, nurses, physiotherapists, paramedics, and other health personnel worked in such countries. Most of them return and it is estimated that 6-10% of physicians practicing in the Netherlands have had experience in developing countries and the country benefits from their rich experience in providing care in areas of scarce resources, the social skills acquired, and their knowledge of tropical diseases.

Biomarkers of exposure to low concentrations of benzene: a field assessment.

OBJECTIVE: To carry out a comprehensive field investigation to evaluate various conventional and recently developed biomarkers for exposure to low concentrations of benzene. METHODS: Analyses were carried out on environmental air, unmetabolised benzene in blood and urine, urinary trans, transmuconic acid, and three major phenolic metabolites of benzene: phenol, catechol, and hydroquinone. Validations of these biomarkers were performed on 131 never smokers occupationally exposed to the time weighed average benzene concentration of 0.25 ppm (range, 0.01 to 3.5 ppm). RESULTS: Among the six biomarkers studied, unmetabolised benzene in urine correlated best with environmental benzene concentration (correlation coefficient, r = 0.76), followed by benzene in blood (r = 0.64). When urinary metabolites were compared with environmental benzene, trans, trans-muconic acid showed a close correlation (r = 0.53) followed by hydroquinone (r = 0.44), and to a lesser extent with urinary phenol (r = 0.38). No correlation was found between catechol and environmental benzene concentrations. Although unmetabolised benzene in urine correlates best with benzene exposure, owing to serious technical drawbacks, its use is limited. Among the metabolites, trans, trans-muconic acid seems to be more reliable than other phenolic compounds. Nevertheless, detailed analyses failed to show that it is specific for monitoring benzene exposures below 0.25 ppm. CONCLUSION: The overall results suggest that most of the currently available biomarkers are unable to provide sufficient specificity for monitoring of low concentrations of benzene exposure. If a lower occupational exposure limit for benzene is to be considered, the reliability of the biomarker and the technical limitations of measurements have to be carefully validated.

Evaluation of biomarkers for occupational exposure to benzene.

OBJECTIVE: To evaluate the relations between environmental benzene concentrations and various biomarkers of exposure to benzene. METHODS: Analyses were carried out on environmental air, unmetabolised benzene in urine, trans, trans-muconic acid (ttMA), and three major phenolic metabolites of benzene; catechol, hydroquinone, and phenol, in two field studies on 64 workers exposed to benzene concentrations from 0.12 to 68 ppm, the time weighted average (TWA). Forty nonexposed subjects were also investigated. RESULTS: Among the five urinary biomarkers studied, ttMA correlated best with environmental benzene concentration (correlation coefficient, r = 0.87). When urinary phenolic metabolites were compared with environmental benzene, hydroquinone correlated best with benzene in air. No correlation was found between unmetabolised benzene in urine and environmental benzene concentrations. The correlation coefficients for environmental benzene and end of shift catechol, hydroquinone, and phenol were 0.30, 0.70, and 0.66, respectively. Detailed analysis, however, suggests that urinary phenol was not a specific biomarker for exposure below 5 ppm. In contrast, ttMA and hydroquinone seemed to be specific and sensitive even at concentrations of below 1 ppm. Although unmetabolised benzene in urine showed good correlation with atmospheric benzene (r = 0.50, P < 0.05), data were insufficient to suggest that it is a useful biomarker for exposure to low concentrations of benzene. The results from the present study also showed that both ttMA and hydroquinone were able to differentiate the background level found in subjects not occupationally exposed and those exposed to less than 1 ppm of benzene. This suggests that these two biomarkers are useful indices for monitoring low concentrations of benzene. Furthermore, these two metabolites are known to be involved in bone marrow leukaemogenesis, their applications in biological monitoring could thus be important in risk assessment. CONCLUSION: The good correlations between ttMA, hydroquinone, and atmospheric benzene, even at concentrations of less than 1 ppm, suggest that they are sensitive and specific biomarkers for benzene exposure.

Blood and urinary benzene determined by headspace gas chromatography with photoionization detection: application in biological monitoring of low-level nonoccupational exposure.

A simple and sensitive gas chromatography (GC) headspace method was developed for the determination of benzene in blood and urine. 1.0 ml of venous blood or urine sample in a headspace vial containing chlorobenzene as an internal standard was incubated at 60 degrees C for 30 min and 0.5 ml headspace gas was used for GC analysis. Unmetabolized benzene in blood or urine was detected at 2.5 min using a silicone gum capillary column and a photoionization detector. The proposed method appears to be more sensitive and reliable than other existing methods, with recovery and reproducibility generally over 90% and a detection limit of 0.64 and 0.51 nmol/l for blood and urinary benzene, respectively. The proposed method was validated with blood and urine samples collected from 25 nonsmokers and 50 smokers. The blood and urine concentrations of benzene in nonsmokers were significantly lower (P < 0.001) than those in smokers: the mean concentrations for blood and urinary benzene, respectively, were 1.42 and 4.21 nmol/l for nonsmokers and 1.49 and 5.19 nmol/l for smokers. A significant correlation (r = 0.61, P < 0.001) was also found between benzene in blood and benzene in urine. These findings suggest that benzene in urine as well as benzene in blood can be used for the biological monitoring of low levels of benzene exposure. Although there was a close correlation between benzene in blood and benzene in urine, no correlation was found between benzene in blood or benzene in urine and the number of cigarettes smoked.

Urinary trans,trans-muconic acid determined by liquid chromatography: application in biological monitoring of benzene exposure.

We describe a sensitive and specific high-performance liquid-chromatographic method for determining the benzene metabolite, trans,trans-muconic acid (ttMA) in urine by measuring ultraviolet absorbance at 265 nm. We mix 1 mL of urine sample with 2 mL of Tris buffer containing vanillic acid as internal standard (IS) and percolate this through a preconditioned ion-exchange column. After rinsing the column with phosphoric acid solution, acetate buffer, and deionized water, we elute the analytes with 2 mL of an equivolume solution of 1.5 mol/L sodium chloride and methanol. Of this, 5 microL is injected into the HPLC column. The mobile phase used consists of, per liter, 10 mL of acetic acid, 100 mL of methanol, and the rest 5 mmol/L sodium acetate. The flow rate was started at 1 mL/min and increased to 1.5 mL/min after 6 min. ttMA and IS were detected at 5.2 and 10.2 min, respectively. The lowest detection limit is 125 pg. Analytical recovery and reproducibility generally exceeded 90%. We validated the method with urine samples collected from normal persons and from refinery workers exposed to benzene concentrations < 1 microL/L. The results show that urinary ttMA is a promising biological marker for risk assessment of low-concentration benzene exposure.

Serological and virological assessment of oral and inactivated poliovirus vaccines in a rural population in Kenya.

A study was carried out in a rural community in Kenya to compare the humoral and intestinal immunity provided by three doses of oral poliovirus vaccine (OPV) and two or three doses of enhanced-potency inactivated poliovirus vaccine (IPV). The immunization series was started at 8-12 weeks of age and the interval between doses was 2 months. In children with low levels of maternal antibodies (i.e., those most at risk), the first dose of either vaccine stimulated antibody response. Children with high levels of maternal antibodies responded to the first dose of OPV, but not to that of IPV. Subsequent doses led to increases in the mean antibody titres with both vaccines. After three doses of OPV, the proportion of children with antibody titres of greater than or equal to 1:8 was 92% for type 1 virus, 98% for type 2, and 90% for type 3. After two doses of IPV the proportion of children with antibody titres of greater than or equal to 1:8 was 94%, 88%, and 97% for type 1, type 2, and type 3, respectively; after three doses of IPV, 100% of children had antibodies greater than or equal to 1:8 for types 1 and 3, and 98% for type 2. Intestinal immunity was tested with a challenge dose of type 1 OPV, but the dose used was too small to detect a significant difference between the vaccines.

Monitoring of exposure to cyclohexanone through the analysis of breath and urine.

Occupational exposure to cyclohexanone was studied for 59 workers through the analysis of environmental air, alveolar air, and urinary cyclohexanol. Environmental cyclohexanone exposure was measured by personal sampling with a carbon-felt passive dosimeter. Cyclohexanone in alveolar air and cyclohexanol in urine were determined with gas chromatography with a flame ionization detector. The end-of-shift urinary cyclohexanol levels correlated well with the time-weighted average environmental cyclohexanone values (r = 0.66). Urinary cyclohexanol corrected for creatinine correlated best with cyclohexanone in air (r = 0.77); when corrected for specific gravity, it gave a similar correlation coefficient (r = 0.73). When the time-weighted average of the exposure was 25 ppm, the corresponding calculated concentration for urinary cyclohexanol was 54.5 mg/1, 23.3 mg/g of creatinine, or 43.5 mg/l at a specific gravity of 1.018. The relationship between cyclohexanone exposure and its concentration in exhaled breath was found to be poorer than that for cyclohexanone exposure and the urinary metabolite (r = 0.51).

Cluster sampling for immunization coverage.

The WHO/EPI cluster sampling method for immunization coverage surveys is part of the course for management training in EPI programmes. The application of this method, based on a framework of villages, is impractical in dispersed populations common in many countries in Africa. To make the method work under those circumstances leads to unacceptable bias, which tends to overestimate the real coverage rate. A modified random cluster sampling method for dispersed populations is presented.

The epidemiology of trachoma blindness in southern Africa.

Twenty five years ago medical scientists working in Southern Africa clarified the natural history of trachoma and how it affected vision impairment and eventual blindness in rural communities. After this, doctors attempted to take appropriate actions against the disease. Initial surveys indicated a blindness prevalence rate of 760/100,000 among rural Africans compared to 100/100,000 among the white population. Trachoma was found to be the main cause of blindness. It was found mostly among children under 15 years to a very high degree and seemed to start soon after birth. Vaccine development failed and mass treatment was started. Control measures which did not reach the community, the population at risk, and which did not affect ways of living were found to be ineffective. Community health programmes were thus started but only in a few areas. Further, it was found that non-medical control strategies would be more effective and efficient. Improvement of living standards is one such strategy.

Measles immunization with further attenuated heat-stable measles vaccine using five different methods of administration.

Further attenuated heat-stable measles vaccine Attenuvax was administered randomly to 109 children using five different methods and a control group (24). Vaccine administration by syringe and needle (0.5 ml) and by jet-injector (0.1 ml) resulted in a high percentage of significant HAI measles antibody titres (greater than or equal to 1:24). Vaccine administration by nose drops (0.5 ml), bifurcated needle or needle planted cylinder did not yield satisfactory levels of serum antibody. Morbidity measured over a period of four weeks after administration showed a moderate increase of respiratory symptoms over the controls. Children who showed a positive tuberculin PPD reaction after BCG immunization did not differ from children with a negative tuberculin reaction in regard to their ability to produce a Kenya. The aim was to find a simpler method of administration of this improved vaccine, suitable for community health workers. The vaccine was shown to be less stable under field conditions than suggested by previous reports.