الفهرس 
Human schistosomiasis,
The epidemiology of human schistosomiasisOnly 14 pages are availabe for public view
 |  | from | 171 |  |  |
| | | from | 171 | | |
Abstract
Schistosomiasis ranks second to malaria in terms of socio-economic and public health importance in tropical and sub-tropical areas. S.haematobium continues to be one of the most important public health problems in Yemen.
The current study aims at investigating (studying) the epidemiology of urinary schistosomiasis and evaluating a therapeutic intervention program in Abyan Governorate Republic of Yemen: the study comprised the following objectives:
1. To study the epidemiologic factors associated with endemicity of urinary schistosomiasis in Battis village, Abyan governorate:
2. To test the validity of the chemical reagent strips as a screening tool for the diagnosis of urinary schistosomiasis compared with quantitative parasitological methods.
3. To identify the snail infection rate in available water sources in the study area.
4. Finally to set and evaluate a therapeutic intervention program for urinary schistosomiasis.
A cross sectional approach was used for the implementation of the 1st phase of the study and an intervention approach (one group pretest-post test design) was used in the 2nd phase. All schoolchildren of the 5th and 6th primary grades and 1st and 2nd preparatory grades of the Al-Sad school were enrolled in the study. The overall total sample was 696 students (305 males and 391 females). The total primary schoolchildren of the 5th grade were 125 (77 males and 48 females) and those of the 6th grades were 364 (93 males and 271 females). The total preparatory schoolchildren of the 1st grades were125 (84 males and 41 females) and those of the 2nd grades were 82 (51 males and 31 females).
The data collection tools included:
A: Pre-designed structured epidemiological and morbidity questionnaire for schoolchildren: It included personal data, socio- demographic information, environmental data, children’s behavior in contact with water, history of recent symptoms and signs as dysuria and haematuria within 2 weeks prior to the implementation of the study as well as past history of previous infection with urinary schistosomiasis one month prior to the implementation of the study and the type of treatment given.
B: Urine examination for detecting macrohaematouria by naked eye examintation and microhaematouria as detected by chemical reagent strips as well as detection of S.heamatobium eggs in urine by microscopical examination using carbolfuchsin centrifugation sedimentation technique and estimation of the intensity of infection (no. of eggs / 10 ml urine) as the gold–standard parasitological diagnosis.
C:Therapeutic intervention program was designed after community diagnosis which depended on the prevalence of S.haematobium infection by parasitological diagnosis as well as by the prevalence of visible haematuria by the questionnaire. All infected schoolchildren were treated by PZQ (40 mg/Kg body weight as a single oral dose). Urine examination was done three and six months post treatment intervention for the evaluation of the efficacy of PZQ therapy using the following indices: egg-negative rate, egg-positive rate and reinfection rate.
D: Malacological data: Snail collection was carried out at weekly intervals for one month in each season to determine the snail species based on the morphological characteristics of their shell, abundance, seasonality and infection rate of snails by both shedding and crushing methods for identification of cercariae.
The results of the present study could be classified in to the following items:
I. The epidemiologic factors associated with endemicity of urinary schistosomiasis in Battis village, Abyan Governorate:
1. The overall prevalence of urinary schistosmoiasis infection among schoolchildren was 18.1%. About 14% had high intensity of infection.
2. The highest prevalence rate of schistosomal infection was found among the age group of 14-16 years (most of them of low intensity of infection). Males presented higher prevalence than females and the majority of them were of low intensity of infection.
3. A significant relationship was detected between fathers’ education and prevalence of S.haematobium. Children whose mothers were illiterate or could read only and write had a significantly higher rate of schistosomal infection. The intensity of infection was not statistically associated with either the father’s or mother’s education.
4. Children whose fathers were farmers had higher rates of urinary schistosomal infection (most of them of low intensity of infection) compared to those whose fathers had other occupations.
5. A significant relationship was detected between the mothers’ working status and prevalence of S.haematobium , while the intensity of infection had no statistically significant association with mother’s working status.
6. The higher prevalence rate of schistosomal infection was found among children from families with high crowding index (most of them of low intensity).
7. With regard to environmental factors, no significant difference was found between urinary schistosomal infection rate and the presence or absence of tap water. The prevalence of S.haematobium infection was significantly higher among students who used open trenches to water streams for sewage disposal draining compared to those who used septic tanks and cesspools. Regarding the proximity of houses to ponds, the prevalence of S.haematobium was significantly higher among those whose houses were relatively near to the ponds compared to those whose houses were far from ponds, (the majority of them of low intensity of infection) with no significant relationship.
8. The prevalence of S.haematobium infection was significantly higher among those who did not know that contact pond water can cause schistosomal infection compared with to those who knew (most of them of low intensity of infection) with an insignificant association.
9. The highest prevalence of S.haematobium infection was among those who swam in ponds and those who used it for domestic purposes, agricultural activities and washing clothes. Most of them low intensity of infection.
10. There were main five significant risk factors associated with urinary schistosomiasis: male gender, proximity of houses to ponds, using ponds for swimming, agricultural activities and bringing pond water for bathing in houses.
II. Assessment of the validity of the morbidity questionnaire as a tool for mass screening of population for urinary schistosomiasis in schoolchildren as compared to the presence of eggs in urine as a gold-standard for parasitological diagnosis.
1. The diagnostic performance of self reported dysuria, self reported past history of previous infection and self reported history of anti-schistosomal treatment using the morbidity questionnaire recorded a poor diagnostic performance.
2. The self reported haematuria, microhamaturia detected by chemical reagent strips and concomitant haematuria (micro and macrohaematuria) revealed a good diagnostic performance while the overall microhaematuria (microhaematuria alone or associated with macrohaematuria) showed an excellent diagnostic performance.
III. Morbidity data of the central hospital of the Abyan Governorate and health unit in Battis village:
The following data were recorded during the implementation of the study:
1. No patients with S. haematobium infection were hospitalized in the central hospital of the Abyan Governorate within the last 3 months before the implementation of the study.
2. Twenty three patients (15 males and 8 females) visited the outpatient clinics of the central hospital with symptoms and signs related to the urinary schistosomiasis within the last 3 months before the implementation of the study.
3. Thirty one individuals (20 males and 11 females) visited the outpatient clinic of health unit in Battis village within the last 3 months before the implementation of the study.
4. The antischistosmal drug (PZQ) was available in both the central and the health unit of Battis village in the last 3 months before the implementation of the study and during the implementation and evaluation of the chemotherapeutic intervention program.
IV. Chemotherapeutic intervention program:
• Community category diagnosis of Battis village was of moderate prevalence according to WHO criteria which defined the moderate prevalence to be <30% visible haematuria by questionnaire or > 10% but <50% infection by parasitological diagnosis. The current study revealed that the percentage of visible haematuria by questionnaire was 5.6% and the prevalence by parasitological diagnosis was 18.1%.
• Out of 126 infected schoolchildren, 122 received PZQ treatment with a participation rate 96.8%.
• Evaluation of the chemotherapeutic intervention program:
a. 3 months post treatment intervention:
The prevalence of S.haematobium was reduced by 51.4% (from 18.1% to 8.8% = egg positive rate).
The percentage of schoolchildren with high intensity of infection was reduced by 100% (from 14.3% to zero).
The intensity of infection associated with isolated microhaematuria was reduced by 100% (from 61.9 to zero).
The high intensity of infection associated with concomitant haematuria was reduced by 100% (from 14.3% to zero level).
The high intensity of infection associated with overall microhaematuria was reduced by 100% (from 14.3% to zero level).
The highest prevalence of infection was among the age group < 12 years (30.8%) followed by age group 13-14 years (2.2%). The overall prevalence was higher among males (13.3%) than females (3.7%).
b. 6 months post treatment intervention:
• The prevalence of S.haematobium was reduced remarkably by 84.5% (from 18.1% at baseline to 2.8%).
• The intensity of infection associated with isolated microhaematuria remained at zero level.
• The high intensity of infection associated with concomitant haematuria remained at zero level.
• The highest prevalence of infection was among age group <12 years (9.1%) followed by age group 14-16 years (4.0%) and the lowest infection rate was among age group 13-<14 years (3.8%). No infection was recorded among age group 12-<13 years.
• These findings denoted that PZQ was efficient in reducing or eliminating the morbidity of urinary schistosomiasis.
• Applying survival analysis denoted that the probability of residual infection after PZQ treatment, dropped to 0.0877 at the 3rd month and to 0.0263 at the 6th month after intervention chemotherapeutic program.
V. Malacological study:
1. B.truncatus was the only snail species found in the 3 surveyed ponds in Battis village.
2. The overall collected snails from November 2010 to June 2011 were 264 snails. The highest snail abundance was recorded in Alkeda pond (100 snails, 37.9%), followed by Almasanaa pond (97 snails 36.7%) and the lowest one was in Alnbowa pond (67,25.4%).
3. The overall snail infection rate in the 3 surveyed ponds was 9.8%. The highest infection rate (6.0%) was detected in Alkeda pond, followed by Almasanaa pond (3.1%) and the lowest one was found in Alnbowa pond (1.5%).
4. The higher abundance and infection rate was recorded in spring season (91 snails, 6.59%), followed by autumn season (73 snails, 4.11%), summer season (43 snails, 2.32%), and in winter season the snail abundance was 57 snails but no infected snails were detected.
Hence, it can be concluded that the morbidity questionnaire has highest diagnostic performance for detection of S.haematobium and that PZQ remains the drug of choice and the cornerstone for urinary schistosomiasis control programs.