Table 1.

Age-specific worm burden thresholds for heavy infections (a proxy for morbidity) (Chan et al., 1994, Bundy et al., 2004).

Age class (years)	Number of worms — lower threshold	Number of worms — higher threshold
0–4	90	250
5–9	130	375
10 +	180	500

The lower thresholds are based on empirical observations of worm numbers associated with developmental deficits (Chan et al., 1994). The higher thresholds are more conservative values intended to reflect more serious clinical consequences and to provide a lower boundary to the estimate of morbidity (Chan et al., 1994, Bundy et al., 2004).