For the purpose of discussing the interaction between agriculture and malaria, farming systems can be divided into two primary types: type I systems, typically smallholder-subsistence or “minifundia” cash-crop businesses, in which land-use rights are held by the farmers working the land; and larger, type II systems, in which the land is not owned by the people who farm it and frequent use is made of migrant or wage laborers. This distinction is similar to that drawn by Bruce-Chwatt (1987) between “rural areas” and “development projects.”
In type II farming, changes in land tenure often occur as land is consolidated into larger parcels. Plantations and capital-intensive agro-industry are two common type II farming arrangements. Poor sanitary conditions among farm workers in type II farming systems favor the transmission of malaria and other diseases that can decimate a work force and make it necessary to import more laborers. For example, the importation of African slaves into Mexico and the establishment of sugarcane plantations there created conditions favorable for P. falciparum, to which many Africans already had some natural immunity (Friedlander, 1969). This resulted in an increase in the already high mortality rate among the indigenous Indian workers and a corresponding increased demand for African slaves.
In the early 1900s, the Italian physician Antonio Celli observed that in southern Europe malaria tended to disproportionately affect the poor or landless, especially those who were seasonal laborers on large farms (Celli, 1900; Chapin and Wasserstrom, 1981). Celli reasoned that transmission depended on the flow of nonimmune persons into malarious zones just before the annual peak of the Anopheles population.
Packard (1984), in a study of colonial Swaziland, has shown how changes in land ownership and labor utilization can increase malaria transmission. Much of the country's best land was given to European colonial miners, farmers, and land speculators. That, combined with the thinning of cattle herds by an epidemic of rinderpest in 1886 and the decline in traditional Swazi raiding activities, turned the native population from essentially self-sufficient food producers into agricultural wage laborers.
Under this arrangement, it was more difficult to cope with drought, and years of drought became years of famine. The occurrence of major epidemics of malaria in Swaziland in 1923, 1932, 1939, 1942, and 1946 appears to be related not only to the rainfall in the year of the epidemic but also to famine conditions in the preceding year. This suggests that sound land reform and agricultural policies, as well as public health measures, can play an important role in malaria control.