Table 1.

Number of subjects in each category and the prevalence (%) of the four species of helminths by age, sex, region, and year

		No. subjects	Hookworms	T. trichiura	A. lumbricoides	H. nana	Combined
Age class age (years)
1	0–1	783	0	0	0	0	0
2	1.1–1.9	1334	0	0	0.15	0	0.15
3	2.0–4.9	2253	0.04	0.09	0.13	0.22	0.49
4	5.0–9.9	1818	0	0.22	0.17	0.22	0.50
5	10.0–14.9	837	0.12	0	0	0.60	0.72
6	15.0–19.9	546	1.5	0.37	0.18	0.37	1.8
7	20.0–29.9	2600	6.3*	1.3	0.69	0.35	7.5
8	30.0–39.9	2566	3.7	0.74	0.39	0.08	4.5
9	40.0–49.9	2288	1.3	0.52	0.44	0	2.1
10	50.0–59.9	1615	0.43	0.5	0.06	0.06	1.1
11	60.0–69.9	1024	0.29	0.29	0	0	0.49
12	70.0–79.9	639	0.16	0	0	0	0.16
13	> 79.9	260	0	0	0	0	0
χ2			279.1	39.0	21.9	37.5	**
P			< 0.001	< 0.001	0.038	< 0.001
Sex
	Males	10791	2.8	0.65	0.37	0.18	3.6
	Females	7772	0.17	0.17	0.10	0.12	0.49
χ2			**	–	–	–	**
P				NS	NS	NS
Region
	Arabian Pen.	974	0	0	0	0.21	0.21
	Eastern Med.	1676	0	0	0	0	0
	Africa	2998	0.20	0.1	0.07	0.27	0.60
	Asia	6502	4.7	1.23	0.71	0.28	6.2
	Qatar	6413	0.05	0	0	0	0.05
χ2			**	112.3	67.5	33.2	**
P				< 0.001	< 0.001	< 0.001
Year
	2005	2559	0.98	0.27	0.23	0.04	1.3
	2006	2120	1.3	0.24	0.33	0.05	1.7
	2007	2220	3.1	0.68	0.45	0	3.7
	2008	2309	3.0	0.78	0.35	0.30	4.0
	2009	3314	1.6	0.48	0.30	0.27	2.5
	2010	2990	1.7	0.50	0.10	0.17	2.2
	2011	3051	0.66	0.23	0.13	0.16	1.1
χ2			67.5	12.9	–	15.6	72.9
P			< 0.001	0.045	NS	0.016	<0.001

^*The highest prevalence in each category is in bold italics for emphasis.

^**In these cases see text for significant interactions between some of the variables in the model.

The statistical outputs were derived from minimum sufficient models, after first fitting for each species in turn, all variables into a single full factorial model, and then stepwise backward deletion of non-significant terms. The degrees of freedom can be calculated from the number of levels within each factor minus 1. The χ² values are not shown for non-significant terms because these had been removed from the model during backward elimination in the derivation of the minimum sufficient model. The χ² values for goodness of fit of the minimum sufficient models for hookworms, T. trichiura, A. lumbricoides, H. nana, and all helminths combined was as follows: 805.7 (dof = 1560, P = 1), 785.9 (dof = 1565, P = 1), 782.3 (dof = 1571, P = 1), 774.8 (dof = 1565, P = 1), and 902.7 (dof = 1548, P = 1), respectively. Additional terms in the final models, that did not incorporate the presence/absence of parasites are not shown, however can be made available on request from the authors.