Evaluation of antigen detection and antibody detection tests for Trypanosoma evansi infections of buffaloes in Indonesia.

Two Ag-ELISAs, an IgG-specific antibody detection ELISA (IgG ELISA) and a card agglutination test (CATT) for the detection of Trypanasoma evansi infections in buffaloes in Indonesia, were compared. Diagnostic sensitivity estimates were obtained by testing sera from 139 Indonesian buffaloes which had been found to be infected by parasitological tests. Diagnostic specificity was estimated by testing sera from 263 buffaloes living in Australia. Response-operating characteristic curves were constructed, and optimal ELISA cut-off values, which minimized the number of false-negative and false-positive results, were chosen. The IgG ELISA had the highest sensitivity (89%) and the CATT had the highest specificity (100%). There was a significant difference between the sensitivities (71 and 81%), but not between the specificities (75 and 78%), of the two Ag-ELISAs. The four tests were further compared by calculation of post-test probabilities of infection for positive and negative test results using a range of prevalence values, and likelihood ratios. The results suggested that the CATT was the best test to 'rule-in' infection (i.e. the highest probability of infection in test-positive animals) and the IgG ELISA was the best test to 'rule-out' infection (i.e. the lowest probability of infection in test-negative animals).     

Tenth international meeting on Trypanosoma evansi: report of the working group. Paris, 24 May 1989

Some epidemiological surveys have provided information on the incidence of Trypanosoma evansi infection among dromedaries in Mali, and among buffaloes in Java and Indonesia. The disease among camels has been reported again from Kazakhstan in the USSR, with the coexistence of T. evansi and Cephalopina titillator in animals which developed acute infection. The disease has been studied among horses in Venezuela and among buffaloes in Vietnam and Indonesia, and suspected among horses in Brazil. Diagnostic kits for rapid and reliable detection of T. evansi are being made available free of charge, upon request, by the institutes which have developed these new techniques, namely: detecting the parasite by agglutination-lysis; detecting antibody (by a modification of CATT); detecting antigen (by using monoclonal antibodies). Once these various diagnostic procedures developed by competent institutes have been evaluated and used widely, the next step will be to standardise the techniques and the antigens. Differential diagnosis of T. evansi and T. equiperdum is still difficult in the case of akinetoplastic strains. For improved evaluation of T. evansi isolates, a proposal has been made to form collections of complementary DNA (cDNA) with a view to exchanging these copies and the original strains. The advice of the International Commission on Zoological Nomenclature has been requested for definitive adoption of a binomial designation for the species T. evansi. With more extensive data on the pharmacology and pharmacokinetics of Cymelarsan and laboratory testing of a new trypanocide called "IMOL 881", research on trypanocides continues.     

Anti-HEV seroprevalence in the area of Lecce

Hepatitis E virus (HEV) is the causative agent of an enterically transmitted viral hepatitis associated with inadequate hygienic conditions. Hepatitis E is endemic in developing countries where it occurs both in sporadic and epidemic form. Outbreaks have been reported in different areas of the world. The aim of the present work was to assess the seroprevalence of HEV infection in the general population and in different risk groups in the area of Lecce. The presence of anti-HEV antibodies was ascertained by qualitative ELISA (Abbott HEV EIA) and Western Blot (Recomblot HEV IgG/IgM, Mikrogen). The prevalence of anti-HEV in the general population was 2.9% while in intravenous drug users, hemodialized patients and immigrants the seroprevalence rates were 0.7%, 4.3% and 15.3% respectively. Our data show a circulation of HEV at low level in the area of Lecce which is endemic for hepatitis A. Higher seroprevalence rates were found in hemodialized patients and remarkably in immigrants coming from endemic areas like Turkey.     

Seroprevalence of Toxoplasma gondii in beef cattle and dairy cattle in northeast China

The seroprevalence of Toxoplasma gondii in beef cattle and dairy cattle in Heilongjiang Province, northeast China, was surveyed between April 2009 and May 2011. A total of 1803 (693 beef cattle and 1110 dairy cattle) serum samples were collected from 10 administrative regions rearing beef cattle and dairy cattle, and antibodies to T. gondii were examined by indirect hemagglutination (IHA) test. The overall seroprevalence of T. gondii in beef cattle and dairy cattle was 2.6% (46/1803), and the prevalence in beef cattle (3.0%) was slightly higher than that in dairy cattle (2.3%). The prevalence of antibodies in adult animals was higher than that in calves, but the differences among the age groups were not significant (p>0.05). The seroprevalence in female (3.4%) and male (2.5%) beef cattle was not statistically significant (p>0.05). Though the prevalence in intensively reared beef cattle and dairy cattle was lower than that in semi-intensively reared animals, the difference was not statistically significant (p>0.05). The results of this survey indicated the presence of T. gondii infection in beef cattle and dairy cattle in Heilongjiang Province, the coldest province in China, which may cause economic losses to the local livestock industry, and may be a source of T. gondii infection for humans in this region.     

Eleventh international meeting on Trypanosoma evansi: report of the Working Group. Paris, 17 May 1990.

Three objectives have been achieved by the Working Group since its creation in 1983: more detailed information (and consequently better awareness) of zones infected by T. evansi; refinement of diagnostic techniques and the development of test kits suitable for field use; development of a new synthetic trypanocide. Exchange of strains between specialist laboratories should be encouraged in order to compare isolates from Africa, Asia and South America by using current techniques of biotechnology, and to open the way to better knowledge of the pathogenicity of T. evansi and to the discovery of effective prophylactic measures. Research reported to the meeting was concerned with the taxonomy and genetics of T. evansi, the cloning and sequencing of nuclear and kinetoplastic DNA (kDNA), chromosomal polymorphism in relation to antigenic variation, the detection of lymphocytic interleukin 2 and its receptors in infected ponies, the use of monoclonal group antibodies to detect T. evansi, and the importance of natural receptivity of the host. A text concerning the diagnosis of surra (T. evansi infection) was drafted and forwarded to the Office International des Epizooties (OIE) for incorporation in the OIE Manual of recommended diagnostic techniques and requirements for biological products. A concise dossier was presented on the pharmacology and pharmacodynamics of the new trypanocide, melarsomine (proprietary name Cymelarsan). The recommended active dosage was 0.25 mg/kg body weight, given as a single intramuscular or subcutaneous injection. Laboratory tests were also reported with ronidazole, demonstrating its trypanocidal activity in rats.     

The occurrence of Trypanosoma evansi in buffaloes in Indonesia, estimated using various diagnostic tests

The prevalence and incidence of Trypanosoma evansi infections in village buffaloes in Central Java were estimated using parasitological tests, two antigen-detection ELISAs (2G6 Ag-ELISA and Tr7 Ag-ELISA), an antibody-detection ELISA (IgG ELISA) and a card agglutination test (CATT). Of 2387 village buffaloes tested in five districts, 4 % (95 % confidence interval [CI]: 3 %, 5 %) were positive with the microhaematocrit test (MHCT), 58 % (95 % CI: 56 %, 60 %) were positive with the 2G6 Ag-ELISA and 70 % (95 % CI: 68 %, 72 %) were positive with the Tr7 Ag-ELISA. An increasing prevalence with age was found and the proportion of positive buffaloes was highest in the over 84 months-old age-group (68 %) with the 2G6 Ag-ELISA and in the 37-60 months-old age-group (78 %) with the Tr7 Ag-ELISA. Parasitaemic buffaloes were found in more than half of the villages visited. Corrected village-specific prevalence values obtained with the two Ag-ELISAs ranged from 0% to over 100%, and prevalence differed significantly (P < or = 0.0001) between villages in four of the five districts. Overall, 10% of buffaloes tested in markets were found to be parasitaemic and 39, 56 and 47 % were found positive with the 2G6 Ag-ELISA, IgG ELISA and CATT, respectively. Incidence rates varied according to the test used and ranged from 0.22 (95 % CI: 0.09, 0.44) to 0.44 (95 % CI: 0.24, 0.76), per animal-year at risk, in two villages. The results highlight the importance of using validated diagnostic tests to obtain accurate estimates of prevalence and incidence. These parameters are needed, for example in mathematical models, for the development and evaluation of different control strategies for T. evansi infections in buffaloes.     

Serological screening and toxoplasmosis exposure factors among pregnant women in the Democratic Republic of Sao Tome and Principe

The seroprevalence of Toxoplasma gondii infection among pregnant women in the Democratic Republic of Sao Tome and Principe (DRSTP) from November 2003 to March 2004 was determined by detection of serum anti-T. gondii antibodies. A short questionnaire interview for pregnant women was performed to investigate risk factors associated with T. gondii infection, including consumption of raw meat or unwashed vegetables, drinking unboiled water and keeping pets (cats and dogs). The overall seroprevalence of T. gondii infection was high (75.2%; 375/499). The older age group of > or =35 years had a significantly higher seroprevalence (85.7%; 54/63) than that of the younger age group of 15-25 years (70.4%; 178/253) (odds ratio 2.5, 95% CI 1.2-5.4; P=0.01). No significant difference in the seroprevalence of T. gondii infection was found between the pregnant women with and without exposure to the risk factors studied. However, among pregnant women with high antibody titers of > or =1:1024, it seemed likely that continual contact with pets and consumption of oocyst-contaminated water or raw unwashed vegetables rather than tissue cysts in meat was the primary route of infection. The incidence of congenital toxoplasmosis in unborn babies should be intensively monitored in the DRSTP.     

Decrease in the prevalence of hepatitis B and a low prevalence of hepatitis C virus infections in the general population of the Seychelles

A serological survey of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections was carried out on a random sex- and age-stratified sample of 1006 individuals aged 25-64 years in the Seychelles islands. Anti-HBc and anti-HCV antibodies were detected using commercially available enzyme-linked immunosorbent assays (ELISA), followed by a Western blot assay in the case of a positive result for anti-HCV. The age-adjusted seroprevalence of anti-HBc antibodies was 8.0% (95% CI: 6.5-9.9%) and the percentage prevalence among males/females increased from 7.0/3.1 to 19.1/13.4 in the age groups 25-34 to 55-64 years, respectively. Two men and three women were positive for anti-HCV antibodies, with an age-adjusted seroprevalence of 0.34% (95% CI: 0.1-0.8%). Two out of these five subjects who were positive for anti-HCV also had anti-HBc antibodies. The seroprevalence of anti-HBc was significantly higher in unskilled workers, persons with low education, and heavy drinkers. The age-specific seroprevalence of anti-HBc in this population-based survey, which was conducted in 1994, was approximately three times lower than in a previous patient-based survey carried out in 1979. Although there are methodological differences between the two surveys, it is likely that the substantial decrease in anti-HBc prevalence during the last 15 years may be due to significant socioeconomic development and the systematic screening of blood donors since 1981. Because hepatitis C virus infections are serious and the cost of treatment is high, the fact that the prevalence of anti-HCV antibodies is at present low should not be an argument for not screening blood donors for anti-HCV and eliminating those who are positive.     

上海市不同人群弓形虫感染现状调查

[目的]了解上海市不同人群弓形虫感染现状及其影响因素。[方法]对健康人群、社区居民、肉品及动物密切接触者和恶性肿瘤患者4 169人用ELISA方法检测弓形虫IgG抗体,同时进行问卷调查。[结果]4组人群弓形虫感染率依次为3.30%、3.88%、5.40%和7.43%,组间差异有显著性(2χ=13.48,P<0.01)。不同性别、年龄、职业之间感染率差异无显著性(2χ=2.37~17.77,P>0.05),但感染率有随文化程度增高而下降的趋势(2χ=15.64,P<0.001)。家庭养猫同时养犬的居民弓形虫感染率(8.63%)显著高于不养宠物的家庭(3.74%)(2χ=11.44,P<0.001)。个人卫生习惯和行为良好者与不良者之间弓形虫感染率差异有显著性(2χ=4.23~12.71,P<0.05~0.001)。[结论]上海市不同人群组弓形虫的感染率均接近本市以往调查的平均水平,感染与家庭饲养宠物及不良卫生习惯有关。     

Seroprevalence of Toxoplasma gondii infection among pre-schoolchildren aged 1-5 years in the Democratic Republic of Sao Tome and Principe, Western Africa

The prevalence status of Toxoplasma gondii infection in children of the Democratic Republic of Sao Tome and Principe (DRSTP), Western Africa, is unknown to date. A serologic survey of T. gondii infection among pre-schoolchildren aged <5 years in the DRSTP was assessed by the latex agglutination (LA) test from November 2003 to March 2004. The overall seroprevalence of T. gondii infection was not low, reaching 21.49% (26/121). No significant gender difference in seroprevalence was found between boys (19.30%; 11/57) and girls (23.44%; 15/64) (chi2 = 0.31, P = 0.58). The older age group of 4-5 years had significantly higher seroprevalence (36.67%; 11/30) than the younger age group of <2 years (10.34%; 3/29) (chi2 = 5.64, P = 0.02). It was noteworthy that the majority of seropositive boys (90.91%; 10/11) or older children aged > or = 2 years (82.61%; 19/23) had high LA titres of > or = 1:1024, indirectly indicating acute Toxoplasma infection. This study is the first report indicating that T. gondii infection is not low in pre-schoolchildren aged <5 years in the DRSTP. Whether the DRSTP pre-schoolchildren acquire T. gondii infection through constant exposure to the parasite from their daily activities owing to poor environmental hygiene should be further evaluated.     

Genetic characterization of Trypanosoma evansi isolated from a patient in India.

The first human case of trypanosomiasis caused by Trypanosoma evansi was recently discovered in India. We have focused on the parasite to investigate whether this atypical infection was due to a particular genotype of T. evansi. The SRA gene was not detected by PCR in the Indian human T. evansi (TEVH) DNA sample. TEVH appears to be closely related to Vietnam WH, with identical alleles for TRBPA and MT30-33 AC/TC microsatellites. Furthermore, T. evansi has homogeneous kDNA minicircles and the minicircles of isolate TEVH were shown to be of Type A. Thus, the T. evansi isolated from an Indian patient appears to be a typical T. evansi as far as we can judge, suggesting that the explanation for this unusual infection may lie with the patient.     

Role of hepatitis E and other hepatotropic virus in aetiology of sporadic acute viral hepatitis: A hospital based study from urban Delhi

Major hepatotropic virus continues to be an important cause of acute viral hepatitis (AVH) in developing countries like India. While epidemics of AVH have been well studied few serious sporadic cases from developing countries have been reviewed. We studied prospectively 75 cases of sporadic AVH who reported to our hospital and were evaluated for the presence of various hepatotropic viruses. The seroprevalence of IgG anti-HEV antibodies was studied in the general population as a control. We found 53.3% (40/75) of sporadic AVH cases were due to hepatitis E virus while 11% (8/75) were due to hepatitis B virus. Hepatitis C virus was responsible for 8% (6/75) of the sporadic AVH cases and hepatitis A was found in 5% (4/75) of the cases. No causative agent was found in 23% (17/75) of the sporadic AVH cases. The sporadic AVH cases due to HEV were not clinically or biochemically not different from AVH due to other viruses. We found a high prevalence of IgG anti-HEV in 35.6% (178/500) among the general population of urban Delhi. The study suggested that hepatitis E was the most common cause of sporadic AVH in urban Delhi. High seroprevalence of IgG anti-HEV antibodies in the general population and amongst the sporadic AVH cases suggests that it is unlikely to be protective antibody. IgM anti-HEV positive serology is considered diagnostic of acute hepatitis E infection in India, where hepatitis E is endemic.     

Longitudinal study of Toxoplasma seroprevalence in South Yorkshire.

Serum samples collected from individuals of a wide range of ages in South Yorkshire between 1969 and 1990 provided the basis for a longitudinal seroprevalence survey of Toxoplasma gondii antibodies. Sera numbering 3868 were screened for T. gondii specific antibodies using a commercial latex agglutination test. The resultant temporal series of serological profiles revealed a rise, with age, in seroprevalence, the rate of which showed a decrease through time. A plateau of around 40-50% prevalence was attained by the 41- to 45-year age-class in 1969 which was not approached until the 66- to 70-year class in the 1988-90 data set. This trend for decline in seroprevalence was confirmed by statistical analysis for the age range 21-60 years. These results may be indicative of a decrease in the rate of toxoplasma exposure in this study community over the 20-year period. The survey of 1988-90 provides a base-line profile of present-day seroprevalence in which 11% of individuals in the age range 16-45 years (roughly corresponding to the childbearing age-range) show evidence of past infection. The representative nature of the serum collection and public-health implications of these results are discussed.     

Trypanosomiasis in domestic animals: the problems of diagnosis

Animal trypanosomiasis presents special problems with regard to diagnosis. The clinical signs are not pathognomonic and the standard techniques for the detection of trypanosomes are not sufficiently sensitive. Although significant improvements have been made in diagnosis, a high proportion of infections still remain undetected as the chronic, more common form of the disease, is often aparasitaemic. In the face of these constraints, alternative methods of diagnosis have been developed, most of which are for the detection of antibody responses to the antigens of the infecting trypanosomes. The most useful of these tests, in view of their sensitivity and specificity, are the indirect immunofluorescent antibody test, enzyme immunoassay (ELISA) and the card agglutination test for trypanosomiasis (CATT) which is used for the diagnosis of Trypanosoma evansi infections. However, there are several shortcomings in antibody detection tests: the antigens used are ill-defined, thus making standardisation of the tests rather difficult with regard to sensitivity and specificity. Furthermore, some of the tests are not applicable to the field. Moreover, the presence of antibody in the serum does not necessarily reflect an existing infection, as antibodies may persist for several months following recovery. Recently, development of assays for the detection of circulating trypanosomal antigens in the blood of infected animals has circumvented this problem since antigen-positivity indicates existing infection. These new assays have not yet been fully evaluated in the field, but the data generated so far do indicate that the diagnostic strategy for the future is likely to be a combination of one of the more sensitive standard trypanosome detection techniques with antigen-trapping ELISA.     

Evaluation of the micro-CATT,CATT/Trypanosoma brucei gambiense,and LATEX/T b gambiense methods for serodiagnosis and surveillance of human African trypanosomiasis in West and Central Africa

OBJECTIVE: To evaluate the performance of serological tests using dried blood on filter-papers (micro-card agglutination test for trypanosomiasis (micro-CATT)) performed under field and laboratory conditions and using whole blood ((CATT/T.b. gambiense) (wb-CATT) and latex agglutination (LATEX/T.b. gambiense) (wb-LATEX)) for the serodiagnosis and surveillance of human African trypanosomiasis in West and Central Africa. METHODS: We evaluated the micro-CATT, wb-CATT and wb-LATEX methods in Côte d''Ivoire and the Central African Republic by screening 940 people. Sensitivity and specificity were calculated for each serological test; only patients with the confirmed presence of trypanosomes in the blood or lymph aspirate were considered true positives. Positive and negative predictive values were also calculated. FINDINGS: Each of the tests showed a lower sensitivity in the Central African Republic than in Côte d''Ivoire. CONCLUSION: The results confirmed the efficiency of the classic wb-CATT to detect sleeping sickness patients. The micro-CATT method can be used for human African trypanosomiasis surveillance if the test is performed on the same day as the blood collection, or if samples are stored at 4 degrees C. Otherwise, micro-CATT can be used when absolute sensitivity is not required. wb-LATEX should only be used for high-specificity screening.     

Validation of an indirect immunoenzyme assay for the detection of antibodies against Trypanosoma evansi in horses in Argentina

An indirect enzyme-linked immunosorbent assay (ELISA) to detect antibodies against Trypanosoma evansi was evaluated using 90 different sera, obtained from naturally-infected horses. As negative controls, 218 sera from the T. evansi-free zone of Argentina, and 90 uninfected sera from the enzootic zone were used. The results of the ELISA were expressed in terms of percent positivity (PP) when compared with a positive primary reference serum, obtained from a horse experimentally-infected with T. evansi. The inter-assay coefficient of variation (CV), expressed as PP, was 44.7% for the negative control serum, 8.8% for the mildly positive reference serum, and 9.2% for the secondary positive control serum, while the intra-assay CV for each of the above sera was 6%, 2.8% and 5%, respectively. Positive and negative serological results were differentiated using a histogram of the distribution of the results obtained using sera from infected and uninfected animals from the enzootic zone (expressed in PP). A PP of 50 indicated a sensitivity of 95.5% for a confidence interval (CI) of 91.3% to 99.7%, and a specificity of 98% for a CI between 95% and 100%. Positive and negative predictive values were established for each rate of prevalence between 0.01% and 25%. The use of reference control sera in each assay enabled reproducible results to be obtained. The author recommends that this methodology be used whenever certification of the T. evansi status of horses is required, and particularly when animals are to be moved from an infected to a disease-free area.     

Seroprevalence of antibodies to hepatitis C virus in high-risk hospital personnel.

OBJECTIVE: To estimate seroprevalence of antibodies to hepatitis C virus in healthcare workers at high risk for blood exposure. DESIGN: A prospective anonymous seroprevalence survey of 243 healthcare workers. SETTING: A large referral hospital and 2 community hospitals in Connecticut. PARTICIPANTS: Healthcare workers, including surgical personnel, dentists, hemodialysis workers, laboratory workers, and emergency room staff. RESULTS: Antibody to hepatitis C virus was found in 1.6% (95% confidence interval [CI95] = 0-3.2%) of healthcare workers. None of the prevalent seropositives had a past history of clinical hepatitis or blood transfusion. CONCLUSIONS: We conclude that the seroprevalence of hepatitis C virus in healthcare workers with a high degree of blood exposure is low and is similar to seroprevalence rates reported for volunteer blood donors. However, first-generation hepatitis C serologic tests may underestimate the true prevalence of infection. Further studies, including prospective cohort studies, will be required to determine if the low seroprevalence is from low risk of acquisition of disease or from loss of measurable humoral antibody response to the virus.     

Toxoplasma gondii infection in the United States: seroprevalence and risk factors

Infection with Toxoplasma gondii can cause severe illness when the organism is contracted congenitally or when it is reactivated in immune-suppressed persons. To determine the prevalence of T. gondii infection in a representative sample of the US population, the authors tested sera from participants in the Third National Health and Nutrition Examination Survey (1988-1994) for immunoglobulin G antibodies to T. gondii. Of 27,145 persons aged > or =12 years, 17,658 (65%) had sera tested. The overall age-adjusted seroprevalence was 22.5% (95% confidence interval (CI): 21.1, 23.9); among women aged 15-44 years, seroprevalence was 15.0% (95% CI: 13.2, 17.0). Age-adjusted seroprevalence was higher in the Northeast (29.2%) than in the South (22.8%), Midwest (20.5%), or West (17.5%) (p < 0.05). In multivariate analysis, risk for T. gondii infection increased with age and was higher among persons who were foreign-born, persons with a lower educational level, those who lived in crowded conditions, and those who worked in soil-related occupations, although in subset analyses risk categories varied by race/ethnicity. Nearly one quarter of adults and adolescents in the United States have been infected with T. gondii. Most women of childbearing age in the United States are susceptible to acute infection and should be educated about ways to minimize exposure to T. gondii.     

Seroprevalence of toxoplasmosis in HIV(+)/AIDS patients in Iran

Toxoplasma gondii has arisen as an important opportunistic agent especially in the central nervous system and in advanced HIV disease can cause significant morbidity and mortality. This study was carried out to determine the seroprevalence of toxoplasmosis among HIV-positive patients in Iran. Blood samples were collected from 201 HIV-positive patients and anti-toxoplasma antibodies were detected by using conventional ELISA. An antibody titer of >3 IU/ml was considered positive. The majority of studied patients were male (male to female ratio: 5 to 1) with the mean age of 36 ± 1 yrs. The seroprevalence of toxoplasmosis in HIV-positive patients was 49.75%. The mean CD4 count in HIV patients with positive toxoplasma serology was 332.5 ± 22.4 cells/μl. Only 1% of the patients had IgM anti-toxoplasma antibodies and 10% of the patients had clinical toxoplasma encephalitis. The mean CD4 count in this group was 66.4 ± 15.5 cells/μl and there was a significant association between CD4 count and rate of toxoplasma encephalitis (P<0.001). Previous reports suggested that toxoplasma encephalitis could be prevented by appropriate chemoprophylaxis. In view of the relatively high prevalence of toxoplasma infection found among the HIV-infected patients in our study, we suggest that routine screening for toxoplasma should be undertaken for all HIV-infected patients in Iran.     

Seroprevalence of Toxoplasma gondii infection among inhabitants in the Democratic Republic of Sao Tome and Principe

The level of Toxoplasma gondii infection among the general population of the Democratic Republic of Sao Tome and Principe is unclear. The T. gondii infection status of inhabitants who visited National Central Hospital on Sao Tome Island was assessed by a latex agglutination test. The overall seroprevalence was 74.5% (120/161). No significant gender difference in seroprevalence was found between males and females. The older age group (> or =45 years) had significantly higher seroprevalence (80.0%, 28/35) than the younger age group (<15 years) (20.0%, 3/15) (chi(2)=16.04, P<0.001).