Malaria and Water Resource Development - Recent Advances and Issues in Environmental Science - page 166

Table 2. Adjusted odds ratios (ORs) using a design-based logistic regression of malaria infection
for Plasmodium vivax (Pv) and Plasmodium falciparum (Pf) by age, gender, month, and village of
residence in Gilgel-Gibe dam area, south-western Ethiopia, 2005.

Variable Adjusted

OR Pv

p-value Adjusted

OR Pf

p-value Adjusted

OR Plas-
modium
postivity

p-value

Village 'at risk' 1.63 0.015 ** 2.40 0.085 * 1.97 0.013**

'control' 1.00 ¨ 1.00. ¨ 1.00 ¨

Month October 1.00 ¨ 1.00 ¨ 1.00 ¨

November 0.88 0.428 0.39 0. 199 0.68 0.200

December 0. 18 0.096 * 0.89 0.828 0.41 0.062*

Age (yrs) <I 1.00 ¨ 1.00 ¨ 1.00 ¨

1-4 1.19 0.209 1.17 0.241 1.20 0.083*

5-9 1.15 0.710 .94 0.890 1.08 0.837

Sex Male 1.00 ¨ 1.00 ¨ 1.00 ¨

Female 1.79 0.054 0.87 0.541 1.33 0. 146

* = signifi cant at 0.1 level ** = signifi cant at 0.05 level

Figure 2 shows the classifi cation tree for P. vivax reproduced by CART. The children
are fi rst split into two groups: those sampled in December (prevalence = 1.5%) and
those sampled in October-November (prevalence = 8.2%). The group of children sam-
pled in October-November was further split in children living in “at-risk” communities

Figure 2. Classification tree of the risk factors for P. vivax infection.