Hans Rosling

Cassava cyanogens and konzo, an upper motoneuron disease found in Africa

Konzo is a distinct form of tropical myelopathy characterised by abrupt onset of spastic paraparesis. Epidemics in East Africa have been attributed to dietary cyanide exposure from insufficiently processed cassava but a study done in Zaire disputed such an aetiology. We investigated a konzo-affected population in rural Zaire and measured the cyanogen content of cassava flour, determined urinary thiocyanate as an indicator of cyanide intake, and compared blood cyanide concentrations in cases and controls. The affected population consumed flour made from short-soaked (one day) cassava roots and thus had high dietary cyanide exposure (urinary thiocyanate in 31 children = 757 mumol/l) compared with the unaffected population (urinary thiocyanate in 46 children = 50 mumol/l) that ate cassava that had been soaked for three days before consumption. 3 konzo patients, but only 2 of 23 controls, had blood cyanide concentrations above 4 mumol/l (p less than 0.01), although serum thiocyanate concentrations were similar. Our findings indicate a causal role in konzo of sustained high blood cyanide concentrations maintained by a deficient sulphur intake impairing cyanide to thiocyanate conversion. The underlying causes of konzo are poverty and food shortage, but a minor improvement of food processing may, as in beri-beri, be preventive.

Socioeconomic determinants of infant mortality: A worldwide study of 152 low-, middle-, and high-income countries

Background: To reach the Millennium Development Goals for health, influential international bodies advocate for more resources to be directed to the health sector, in particular medical treatment. Yet, health has many determinants beyond the health sector that are less evident than proximate predictors. Aim: To assess the relative importance of major socioeconomic determinants of population health, measured as infant mortality rate (IMR), at country level. Methods: National-level data from 152 countries based on World Development Indicators 2003 were used for multivariate linear regression analyses of five socioeconomic predictors of IMR: public spending on health, GNI/capita, poverty rate, income equality (Gini index), and young female illiteracy rate. Analyses were performed on a global level and stratified for low-, middle-, and high-income countries. Results: In order of importance, GNI/capita, young female illiteracy, and income equality predicted 92% of the variation in national IMR whereas public spending on health and poverty rate were non-significant determinants when adjusted for confounding. In low-income countries, female illiteracy was more important than GNI/capita. Income equality (Gini index) was an independent predictor of IMR in middle-income countries only. In high-income countries none of these predictors was significant. Conclusions: The relative importance of major health determinants varies between income levels, thus extrapolating health policies from high- to low-income countries is problematic. Since the size, per se, of public health spending does not independently predict health outcomes, functioning health systems are necessary to make health investments efficient. Potential health gains from improved female education and economic growth should be considered in low- and middle-income countries

ASSOCIATION OF HIGH CYANIDE AND LOW SULPHUR INTAKE IN CASSAVA-INDUCED SPASTIC PARAPARESIS

Urinary excretion of sulphur compounds was studied in children from a population in Mozambique that had been affected, during a drought, by an epidemic of spastic paraparesis attributed to cyanide exposure from cassava. The children had increased thiocyanate and decreased inorganic sulphate excretion, indicating high cyanide and low sulphur-containing amino-acid intake. Children from a neighbouring cassava-eating area, where no cases of spastic paraparesis had occurred, had lower thiocyanate excretion but higher inorganic sulphate excretion. These results support the hypothesis that the epidemic was due to the combined effects of high dietary cyanide exposure and sulphur deficiency.

Simple sequence repeat marker diversity in cassava landraces: genetic diversity and differentiation in an asexually propagated crop

Abstract. Cassava (Manihot esculenta) is an allogamous, vegetatively propagated, Neotropical crop that is also widely grown in tropical Africa and Southeast Asia. To elucidate genetic diversity and differentiation in the crops primary and secondary centers of diversity, and the forces shaping them, SSR marker variation was assessed at 67 loci in 283 accessions of cassava landraces from Africa (Tanzania and Nigeria) and the Neotropics (Brazil, Colombia, Peru, Venezuela, Guatemala, Mexico and Argentina). Average gene diversity (i.e., genetic diversity) was high in all countries, with an average heterozygosity of 0.5358 ± 0.1184. Although the highest was found in Brazilian and Colombian accessions, genetic diversity in Neotropical and African materials is comparable. Despite the low level of differentiation [Fst(theta) = 0.091 ± 0.005] found among country samples, sufficient genetic distance (1-proportion of shared alleles) existed between individual genotypes to separate African from Neotropical accessions and to reveal a more pronounced substructure in the African landraces. Forces shaping differences in allele frequency at SSR loci and possibly counterbalancing successive founder effects involve probably spontaneous recombination, as assessed by parent-offspring relationships, and farmer-selection for adaptation.

An outbreak of acute intoxications from consumption of insufficiently processed cassava in Tanzania

Abstract An extensive outbreak of acute intoxications, with nausea and vomiting as major symptoms, occurred in a drought stricken district in southern Tanzania in 1988. Investigations revealed that these effects were due to cyanide intoxication from consumption of insufficiently processed cassava roots, the only crop to survive the drought. High plasma and urine levels of the cyanide metabolite thiocyanate support a high dietary cyanide exposure in the affected population. Due to food shortage the lengthy sun-drying normally used to remove cyanogenic glucosides from roots was replaced by repeated pounding and drying to obtain flour for consumption in one day. An experiment indicates that high residual levels of cyanohydrin, an intermediate breakdown product of the cyanogenic glucoside, was the principal source of dietary cyanide exposure. Cyanohydrins may be easily removed and toxic effects from cassava avoided by application of more effective tissue disintegration and drying techniques.

Geographical and seasonal association between linamarin and cyanide exposure from cassava and the upper motor neurone disease konzo in former Zaire

High cyanide intake from consumption of insufficiently processed cassava has been advanced as a possible aetiology of the upper motor neurone disease konzo. However, similar neurodamage has not been associated with cyanide exposure from any other source. With an ecological study design, we compared 22 cases of konzo, 57 unaffected household members and 116 members from unaffected households, a total of 195 subjects, in konzo‐affected savanna villages with 103 subjects in adjacent non‐affected forest villages in the Paykongila area in the Bandundu Region. Zaire.

Foreign field hospitals in the recent sudden-onset disasters in Iran, Haiti, Indonesia, and Pakistan.

INTRODUCTION Foreign field hospitals (FFHs) may provide care for the injured and substitute for destroyed hospitals in the aftermath of sudden-onset disasters. PROBLEM In the aftermath of sudden-onset disasters, FFHs have been focused on providing emergency trauma care for the initial 48 hours following the sudden-onset disasters, while they tend to be operational much later. In addition, many have remained operational even later. The aim of this study was to assess the timing, activities, and capacities of the FFHs deployed after four recent sudden-onset disasters, and also to assess their adherence to the essential criteria for FFH deployment of the World Health Organization (WHO). METHODS Secondary information on the sudden-onset disasters in Bam, Iran in 2003, Haiti in 2004, Aceh, Indonesia in 2004, and Kashmir, Pakistan in 2005, including the number of FFHs deployed, their date of arrival, country of origin, length of stay, activities, and costs was retrieved by searching the Internet. Additional information was collected on-site in Iran, Indonesia, and Pakistan through direct observation and key informant interviews. RESULTS Basic information was found for 43 FFHs in the four disasters. The first FFH was operational on Day 3 in Bam and Kashmir, and on Day 8 in Aceh. The first FFHs were all from the militaries of neighboring countries. The daily cost of a bed was estimated to be US

The importance of being bitter—a qualitative study on cassava cultivar preference in Malawi

2,000. The bed occupancy rate generally was < 50%. None of the 43 FFHs met the first WHO/Pan-American Health Organization (PAHO) essential requirement if the aim is to provide emergency trauma care, while 15% followed the essential requirement if follow-up trauma and medical care is the aim of deployment. DISCUSSION A striking finding was the lack of detailed information on FFH activities. None of the 43 FFHs arrived early enough to provide emergency medical trauma care. The deployment of FFHs following sudden-onset disasters should be better adapted to the main needs and the context and more oriented toward substituting for pre-existing hospitals, rather than on providing immediate trauma care.

The origin of hydrogen cyanide in breath

We conducted qualitative interviews in Nkhata‐Bay district in Malawi to elucidate why farmers preferentially grow cassava cultivars providing bitter roots. Cassava was mainly grown to produce flour for making the staple food, kondowole. Plants were identified as belonging to one of the 54 mentioned cultivars with local names. All the farmers stated that bitter taste of roots predicted toxicity and necessity for processing. Cultivars were grouped into “cool” or “bitter” based on whether the roots could be eaten fresh, or required processing before consumption as kondowole. Farmers strongly preferred cultivars grown for flour production to have bitter roots since this protected against theft, destruction by animals and deterred household members from unplanned harvest. Since processing is done by women bitterness empowers women to control the families staple crop. Bitter cultivars reportedly yielded more and roots produced an easier to mould kondowole. Bitterness and toxicity were not perceived as a problem.

Attempted suicide in Hanoi, Vietnam

The excretion of hydrogen cyanide in breath and blood concentrations of cyanide were measured in eight normal subjects. There was no correlation between breath and blood levels of cyanide. Furthermore, breath cyanide concentrations calculated from blood values were much lower than measured values, which suggested a local production of hydrogen cyanide in the oropharynx. When saliva was incubated at 37° C hydrogen cyanide was formed in the presence of air but not in a nitrogen atmosphere. No hydrogen cyanide was formed with boiled saliva and the production of hydrogen cyanide by native saliva was inhibited by catalase and by 6-n-propyl-thiouracil. Centrifugation of saliva resulted in a supernatant and a sediment, which were both required for the formation of hydrogen cyanide. Dialysis of the supernatant abolished its cyanide forming ability, which could be restored by addition of thiocyanate. We conclude that most of the hydrogen cyanide found in breath from normal human beings originates from oxidation of thiocyanate by salivary peroxidase in the oropharynx. As a consequence measurements of breath hydrogen cyanide can only be used to detect heavy exposure to cyanide.