Cutaneous leishmaniasis (CL) is endemic in Al Hasa region, Eastern Province, Saudi Arabia, where about 2.8% of the population have been affected. Control of rodents (Psammomys obesus) and sandflies (Phlebotomus papatasi) began in 1989. We evaluated environmental factors and the effect of control measures on CL rates from 1989 to 1996.
Methodology
An ecological study was conducted using CL cases reported to leishmania control department (LCD) of Al Hasa health directorate from 1989 through 1996. We calculated CL incidence rates for each catchment area and yearly percent changes in incidence rates as outcome variables. We compared these rates and changes in rates to possible explanatory variables reflecting land use. Intensity of control measures (maximal, minimal, light, no control) applied to the districts were recorded as phase 1 (1989 to 1990), phase 2 (1990 to 1995), phase 3 (1995 to 1996).
Results
We found a clustering of CL cases in eight districts that was repeated every year. CL incidence rates decreased by 35% from 1989 to 1990 after control measures were first applied. Yearly decreases in CL rates averaged 10% from 1990 to 1995 then the CL cases increased in 1996 by 25% after control measures were relaxed in 1995. High CL rates had a strong association with farms (1989, 1990, 1994, 1995) but no association with empty land and desert areas where reservoir hosts and their plant food were found. Decrease in CL incidence rates for districts in phase 1 was 45% for districts with minimal insecticide application, 35% for districts without insecticide control, in phase 2: 7.5% decrease in CL rates with maximal insecticide and 0.9% decrease in CL rates in districts without insecticide control. For mechanical control, phase 1, the decrease in CL incidence rate was 4% for districts without control. In phase 2, there was a decrease in CL incidence rates with minimal (8.7%), light (4.5%) and without control (2.2%).
Conclusion
We suspect that each district has a mix of highly localized environmental characteristics that determine the CL incidence rates. Although CL surveillance data showed some impressive decreases in CL disease in the entire Al Hasa region, close inspection of the data showed no consistent effect. Improving the surveillance system is required to better identify CL transmission foci and to better assess the effect of control measures.