More accuracy estimation of the worm burden in the ascariasis of children in Kinshasa

The present study aims to give a better estimate of the worm burden (ascariasis) to address accurately the impact of intestinal parasitosis on the children growth in Africa. The study was conducted on 20 subjects aged 10 months to 10 years (Mean ± SD: 5.6 ± 2.3 years). They were treated with 10 mg/kg of Pyrantel pamoate. The next day, the stools were collected, washed and filtered to harvest all adult ascaris. In total, 141 ascaris (71 males and 70 females) were extracted for 879.9 g of stool. The geometric mean of eggs counted was 29 by 2 mg of stool. The daily eggs laying per female was estimated to 202,500 eggs/days (CI95%: 128,800 – 276,200). Statistical analysis shows that the parasitic worm burden was proportional both to the number eggs counted per unit of stool volume, and to age of infested subject. A regression model based on these two parameters, with a coefficient of determination equal to 59 %, was retained. Thus, for an old subject respectively of 1, 5 and 10 years, at which 1 egg of ascaris in approximately 2 mg of a preparation would lodge a respective parasitic mass of 1, 3 and 9 g. The results are in the form of confidence interval. For example, for a 5 years old subject with an average of 10 eggs (CI95% = 5.6 - 14.4) after reading of 2 separated preparations coming from the same specimen, the estimated parasitic load is laying between 7 and 11 g.

collected 20 stool samples containing adult worms. These specimens were brought to the 8 0 laboratory where they were weighed and sieved through a wire mesh for roundworm harvesting. The number of worms and their weight relative to the number of eggs or the age of the subjects where appropriate to certain variables, such as the weight of the worms and the number of eggs, 8 7 in order to find a better fit. The quality of the adjustment obtained was evaluated at the 8 8 probability level of 5% using the coefficient of determination R². The latter represents the amount 8 9 of information correctly translated by the mathematical model used for the adjustment of the data. The model chosen was the one that gave the largest R². The confidence interval was determined 9 1 according to Poisson's law from two measurements made on two preparations made on the same 9 2 specimen. The daily spawning estimate was based on the geometric mean number of eggs 9 3 observed in a standard stool volume examined. According to Sinniah B et al 4 , adult female 9 4 roundworms start laying when they reach a critical weight of 1.1 g.

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The analyzes were performed using SPSS software version 10.0.7 and additional calculations 9 6 using MathCad version 7 software. On average, we counted 55.5 eggs per preparation and collected 141 worms. These had a sex 1 0 0 ratio of 1.01: 1 (71 males and 70 females). Females were significantly larger than males (mean 1 0 1 weight: 3.7 1.8 g versus 1.5 0.7 g, mean size: 21.2 4.8 cm vs 15.6 3.0 cm). The extreme values 1 0 2 observed were, for the size, between 120 and 320 mm for females as against 102 and 240 mm for 1 0 3 males, and for weight, between 0.3 and 7.2 g for females, and between 0.2 and 4.3 g for males. Ten percent of females had a weight of less than 1.1 g as a critical threshold for starting  The geometric mean number of eggs per preparation was 29. The other average parameters are 1 0 7 shown in Table 1. Since the examined stool mass was 879.9 g, spawning per female was estimated at 182,300 eggs /  The best retained linear regression model, which had a coefficient of determination (R²) equal to 1 1 6 0.590 (p = 0.001), the highest of all, which predicted age and number of eggs; had the following 1 1 7 form: It should be noted that the regression found between worm weights and each of the individual 1 2 0 variables was relatively less effective. In fact, the value of R² obtained with the age of the 1 2 1 subjects and the number of eggs was respectively equal to 0.253 (p = 0.024) and 0.296 (p = 1 2 2 0.013).

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As an illustration, from the model chosen and for a standard preparation of 2 mg containing 1 egg 1 2 4 of A. lumbricoides, the parasite mass for a subject aged respectively 1, 5 or 10 years will be 1, 3 1 2 5 and 9 g. For example, for a 5-year-old child with an average of 10 eggs (95% CI = 5.617-14.383) after reading 2 1 2 8 independent preparations, the estimated parasite load will be between 7 and 11 g. The limits of this 1 2 9 confidence interval were calculated according to the parameters of the regression model used:  A smear containing two eggs, according to Vandepitte 3 , corresponds to an adult roundworm.  In the present study, the relationship we found between the number of worms or their mass age of the subjects (Figure 2). In fact, the oldest subjects presented the largest worms compared  Not only the number of eggs found, but also the number of gravid females present in the 3.7 mm. The average minimum weight of a female producing eggs is 1.1 g and would also 1 5 7 depend on the age of the female. In this study, 10% of females had a weight less than this value.

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In addition, congestion of the intestinal microenvironment due to the massive presence of 1 5 9 parasites has a negative impact on oviposition 5 . In other words, the law of diminishing returns corroborates somewhat that found in the present work which was 1.01 male against 1 female, in 1 7 0 both cases, close to parity.

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Given the importance of the hazards of spawning, for a better estimate of the parasite mass from 1 7 2 this parameter, we recommend carrying out at least two independent measurements from which 1 7 3 the mean and the confidence interval will be calculated, preference is given to the geometric In conclusion, estimating the parasite mass of A. lumbricoides is a complex undertaking that 1 7 6 needs further refinement. We believe that while estimating the parasite mass for a given 1 7 7 9 individual remains quite risky, it is very valuable for estimating average parasite mass in 1 7 8 community surveys. To improve the quality of our estimates, we must increase the size of our 1 7 9 samples, on the one hand, and integrate the possible influence of the environment, on the other 1 8 0 hand.