Soil Nutrient Deficiencies in an Area of Endemic Osteoarthritis (Mseleni Joint Disease) and Dwarfism in Maputoland, South Africa

Unusually high incidences of dwarfism and an endemic osteoarthritis, called Mseleni Joint Disease (MJD), occur on the flat, sandy coastal plain of Maputaland. This rare disease begins with stiffness and pain in the joints and progresses to varying degrees of disability, with some of the afflicted requiring aid in walking and others completely immobile. Almost 3% of local adults are dwarfs, while 38% of women and 11% of men have MJD (Fellingham 1973, Lockitch 1974). Medical studies since the 1970s have examined hematological, radiological, mycotoxicological, and genetic factors, and made comparisons with other diseases (Ballo 1996, Burger 1973, Lockitch 1973, Marasas 1986), yet have been fruitless in determining the etiology of MJD or the dwarfism. Dwarfism has been linked to Zn deficiencies in other areas and several bone-related disorders have been associated with P, Ca, and Mg deficiencies (Hidiroglou 1980). Calcium, Mg, Mn, and F deficiencies have all been speculated as possible causative factors of MJD (Fincham 1981, 1986), and the possibility of soil-derived nutrient deficiencies within this landscape is addressed. Maputaland is located on the northeast corner of South Africa, occupying an area about 50 by 100 km. It has a warm, subtropical climate, with summer rainfall occurring as cyclonic events, and varying from 1000 mm at the coast to 600 mm near Mseleni. Summer temperatures are high, averaging 29° C, and winters mild at 17° C. The region has high floral and faunal diversity and endemism (van Wyk 1996), and contains 15 major vegetation zones. Geologically, Maputaland is covered with recent Quaternary sands, with several north-south paleodune cordons parallel to the coast. There is little relief and, besides the coastal dunes reaching almost 200 m above mean sea level, the average elevation is 100 m. No rivers cross the plain, but groundwater is frequently exposed at the surface, as evidenced by Lake Sibayi and the numerous pans in the region. Soils are mostly the Waterton family of the Fernwood form (thermic, coated Typic Quartzipsamments) (SCWG 1991, USDA 1999). These sands are inherently infertile, vary in pH from neutral to acidic, have a low cation exchange capacity, low organic matter content, and are dominated in the clay fraction by kaolinite.