Control of cystic echinococcosis/hydatidosis: 1863-2002.

Echinococcosis/hydatidosis, caused by Echinococcus granulosus, is a chronic and debilitating zoonotic larval cestode infection in humans, which is principally transmitted between dogs and domestic livestock, particularly sheep. Human hydatid disease occurs in almost all pastoral communities and rangeland areas of the underdeveloped and developed world. Control programmes against hydatidosis have been implemented in several endemic countries, states, provinces, districts or regions to reduce or eliminate cystic echinococcosis (CE) as a public health problem. This review assesses the impact of 13 of the hydatid control programmes implemented, since the first was introduced in Iceland in 1863. Five island-based control programmes (Iceland, New Zealand, Tasmania, Falklands and Cyprus) resulted, over various intervention periods (from <15 to >50 years), in successful control of transmission as evidenced by major reduction in incidence rates of human CE, and prevalence levels in sheep and dogs. By 2002, two countries, Iceland and New Zealand, and one island-state, Tasmania, had already declared that hydatid disease had been eliminated from their territories. Other hydatid programmes implemented in South America (Argentina, Chile, Uruguay), in Europe (mid-Wales, Sardinia) and in East Africa (northwest Kenya), showed varying degrees of success, but some were considered as having failed. Reasons for the eventual success of certain hydatid control programmes and the problems encountered in others are analysed and discussed, and recommendations for likely optimal approaches considered. The application of new control tools, including use of a hydatid vaccine, are also considered.

Vigilancia epidemiológica de enfermedades transmitidas por alimentos en la Provincia de Río Negro, Argentina, 1993-2001 / Surveillance of foodborne diseases in the province of Rio Negro, Argentina, 1993-2001

A total of 39 outbreaks of foodborne diseases affecting 958 people in the province of Rio Negro, Argentina between 1993 and 2001 are described and evaluated. The main causal agents were identified involving food, sites of occurrence, risk factors and notification system used. Salmonella spp (38%), Trichinella spiralis (15%), Escherichia coli (13%) and Staphylococcus aureus (15%) were the most frequent agents present in outbreaks. Salmonella spp produced the largest number of cases (52%). Food involved were cooked meat (36%), cheese (10%), sandwiches (10%), deserts (10%) and ice cream (8%). Indeed, ice creams were involved in the largest number of cases and of people affected. In relation to the source of food, 41% of outbreaks were caused by homemade meals, 23% by catering or ice cream parlor, 13% in family parties, 8% in county fairs and 8% in hotel restaurants. In 28% of the outbreaks the etiological agent was identified exclusively by epidemiological analysis, in 64% isolation of the agent was carried out, and in 8% of the cases, a final diagnosis could not be obtained. Validity of epidemiological studies in foodborne disease, the necessity of strengthening the notification system of outbreaks, and the importance of good practices in food handling are analyzed.

Se describen 39 brotes de enfermedades transmitidas por alimentos que afectaron a 958 personasen la provincia de Río Negro, Argentina, en el período 1993- 2001. Se identifican los agentes causales, los alimentos involucrados, los sitios de ocurrencia, los factores de riesgo involucrados y los mecanismosde notificación empleados. Salmonella spp (38%), Trichinella spiralis (15%), Escherichia coli (13%) y Staphylococcus aureus (15%) resultaron los agentes más frecuentes en los brotes. Salmonella spp. tambiénprodujo el mayor número de casos (52%). Los principales alimentos involucrados resultaron cárneos (36%),quesos (10%), fiambres y sándwiches (10%), postres (10%) y helados (8%). El mayor número de casos, por suparte, fue causado por la ingestión de helados (37%). Con relación al origen de los alimentos, 41% de los brotesfueron causados por comidas elaboradas en los domicilios, 23% en establecimientos comerciales, 13% enfiestas familiares, 8% en fiestas comunitarias y 8% en restaurantes de hoteles. En el 28% de los brotes fueidentificado el agente etiológico por análisis epidemiológico exclusivamente, en el 64% se logró el aislamientodel agente, mientras que en el 8% de los casos no se logró el diagnóstico definitivo. Se analiza el valor de laencuesta epidemiológica en los estudios de enfermedades transmitidas por alimentos, la necesidad de fortalecerel sistema de notificación médica de casos y brotes y la importancia de las buenas prácticas en la manipulaciónde alimentos.

A case-control study of the risk factors for cystic echinococcosis among the children of Rio Negro province, Argentina.

In 1984 the prevalence of cystic echinococcosis (CE) in Rio Negro province in central Argentina reached alarming levels, with almost 6% of children aged 7-13 years infected with the causative agent, Echinococcus granulosus. Although the control activities developed between 1980-2000 have now lowered the prevalence of infection in this age-group to 1.1%, transmission of E. granulosus has clearly not ceased. The aim of the present study was to identify possible flaws in the control programme and the risk factors associated with CE. The 24 cases and 66 controls used were identified during a survey of the 1,070 schoolchildren attending 12 schools in Ingeniero Jacobacci, Rio Negro province. In interviews based around a standardized questionnaire, the adult female with responsibility for each subject (usually the mother but sometimes a grandmother or guardian) was asked 70 questions about the child and his or her immediate family, their contact with dogs and relevant environmentmental factors, and their level of contact with the control programme. Univariate and multivariate analyses were used to determine odds ratios (OR) and their 95% confidence intervals (CI). The main risk factors found to be significantly associated with CE were having a family member with the disease (OR = 3.11; CI = 0.92-10.47), spending the first years of life surrounded by a large number of dogs (OR = 2.11; CI = 1.2-3.5), and having a father who slaughtered sheep at his workplace (OR = 1.14; CI = 1.04-1.24). Obtaining drinking water from a tap (OR = 0.28; CI = 0.08-1.01) also remained in the final model, as a protective factor.

Ovine Echinococcus granulosus transmission dynamics in the province of Rio Negro, Argentina, 1980-1999.

In this work, the impact of a hydatidosis control programme for dogs on the intermediate ovine host was specifically analysed to determine the levels of prevalence achieved and the dynamics of parasite transmission, as well as to evaluate the quality of diagnostic systems in slaughterhouses. A field study was conducted in four slaughterhouses (Valcheta, Los Menucos, Jacobacci, Bariloche) that process animals coming from all the departments within the work area. The control programme for dogs entailed treating dogs with 5 mg/kg praziquantel at 2-month intervals for 20 years. Sample size was determined with a 10% error margin and a 95% significance level. Harvested viscera (liver, lungs, kidneys) were preserved in 5% formaldehyde and sent to the laboratory for diagnostic confirmation of both positive and negative specimens. The 61% initial prevalence dropped to 18.3% at the end of the 10-year period, observed differences proving significant (Chi-square=15.454, P=0.00). There were statistically significant increases in infection prevalence with age (Pearson's Chi-square=133.61, P=0.00). Overall, 37.2% of hydatidosis cases diagnosed in slaughterhouses were considered non-hydatid by histological study. On the other hand, 1.1% of those diagnosed as healthy were found to be infected with hydatidosis. The number of hydatid cysts per animal increased with age: 0.04 in lambs and 1.22 in adults (linear regression equation, -0.0539+0.0127 x age), whereas the average for the whole period was 3.7% in lambs and 20.5% in adults. Viability studies indicated that 63.8% of parasitised animals had viable cysts, out of which 53.3% were fertile. Diagnosis of infection in sheep made by means of an adjusted statistical design and with histological confirmation of the presumptive diagnosis made in slaughterhouses demonstrated the flaws of the official systems for epidemic surveillance of hydatidosis. However, there was no overall significant difference in slaughterhouse and laboratory data.Ro was 0.53 and could imply a decrease in reproductive capacity of the parasite and steady state extinction.

Epidemiological surveillance of human hydatidosis by means of ultrasonography: its contribution to the evaluation of control programs.

Epidemiological surveillance for hydatidosis is based on initial determination and follow-up of the infestation rate in man, sheep and dogs. The use of ultrasonography (US) as a screening method has demonstrated its usefulness in detecting asymptomatic human carriers of abdominal hydatidosis. To evaluate the contribution of US to epidemiological surveillance within the framework of disease control programs, we performed 719 US studies in school children from 7 to 13 years of age, in rural areas of Río Negro, Argentina, subjected to canine deparasitization during 1984/1986 and 1997/1998. In the first period, 15/268 (5.6%), while in the second, 5/451 (1.1%) carriers were detected (P < 0.0004). The average diameter of the cysts was 4.71 cm in 1984/1986 and 2.14 in 1997/1998. US as a mass screening method allows evaluation of early changes in human prevalence rates, closely related to infestation rates in sheeps and dogs, thus providing a sensitive indicator of the evaluation of control programs.

Human cystic echinococcosis: contributions to the natural history of the disease.

In areas where human cystic echinococcosis (CE) is endemic, the results of ultrasonographic or X-ray examinations have revealed a surprisingly high prevalence of abdominal cysts in asymptomatic individuals. The results of preliminary studies indicate that the ratio of liver infection:lung infection (LI:LU) is much higher in the asymptomatic individuals (9:1 or 7:1) than is usual among symptomatic cases of liver CE (2:1). This difference may indicate that, compared with lung cysts, liver cysts rarely cause morbidity, perhaps because they grow at a slower rate than those in the lungs. In an attempt to explore this possibility, the published results of ultrasonographic and radiological surveys on general populations and the records of autopsies and hospital-based investigations of symptomatic cases of liver CE were reviewed. In general populations, the overall prevalence of cysts in the liver (2.5%) was found to be much higher than that of cysts in the lungs (0.3%), giving a LI:LU ratio of 8.3:1. In the symptomatic cases, however, LI:LU ratios were only 2.5:1 (based on hospital records) or 4.1:1 (based on autopsy records). In addition, the estimated mean growth rate of the cysts in 53 surgical cases of CE from the province of Río Negro in Argentina was found to be significantly higher than that of the cysts in 89 asymptomatic cases detected during ultrasonographic surveys in the same area.

Rate of infection and of reinfection by Echinococcus granulosus in rural dogs of the province of Rio Negro, Argentina.

Hydatidosis (cystic echinococcosis) constitutes a serious public health problem in the Province of Rio Negro, Argentina. In the present work it was intended to evaluate the prevalence of the canine echinococcosis in rural areas of the Province of Rio Negro and studied the reinfection rate in dogs after treatment with Praziquantel during the period 1980-1997. A total of 496 dogs were studied in 18 canine concentrations in order to establish the initial prevalence rate which was 42.3%. From 1980 onward dogs should have been systematically treated with anthelmintic every 2 months in rural areas and every 6 months in urban areas. We estimated that approximately 65% of dogs were treated. To determine the reinfection rate, 476 dogs (1984) and 598 dogs (1996) were studied after anthelmintic treatment during two sequential time periods (0-45; 46-90 days). In both cases treated animals were compared with untreated dogs. Prevalences were 3.5%, 6.7% and 21.3% in 1984 and 0.8%, 4.0% and 10.0% in 1996. For the purpose of surveillance a total number of 21,444 dogs were studied during 18 years. Prevalence of Echinococcus granulosus decreased significantly in the first year from 42.3% to 6.1%.

Diagnosis of human hydatidosis. Predictive value of a rural ultrasonographic survey in an apparently healthy population.

The usefulness of ultrasonography (US) in the early diagnosis of hydatidosis, applied in large-scale surveys to populations lacking clinical symptoms of the disease, has been amply documented. However, the rate of false positive and negative results is poorly described. Due to this, the present paper is aimed to evaluate the sensitivity, specificity and predictive value of a conventional rural ultrasonographic survey in comparison with higher imaging complexity. Accordingly, during 1997 and 1998 a total of 1054 children from 7 to 14 years of age were evaluated by means of US, in the town of Ingeniero Jacobacci, Province of Rio Negro, Argentina, employing a portable device for population studies. All detected cases were referred to a high complexity center specialized in imaging diagnosis for their re-evaluation with US, CT scanning and X-rays. A control group comprising 3 children negative by US for each positive case in the mass screening survey was selected and reexamined by US and X-rays and CT scanning in doubtful situations. Twenty-seven asymptomatic carriers were referred with images compatible with hydatid cysts, while 66 were classified as disease free. At reexamination, 24 of those diagnosed as carriers and the totality of those classified as healthy were confirmed. On the basis of our results, a sensitivity of 100%, a specificity of 95.6% and a global test value of 96.7% were estimated.

[Asymptomatic carriers of hydatidosis: epidemiology, diagnosis, and treatment]. / Portadores asintomáticos de hidatidosis: epidemiología, diagnóstico y tratamiento.

Until a short time ago, hydatidosis was considered a pathology that could only be resolved surgically. However, in recent years progress has been made with the epidemiology, diagnosis, and treatment of the disease, and new information on the natural history of hydatidosis has helped define new criteria for its treatment. It is now known that as many as 67% of the carriers of liver cysts who are asymptomatic remain so throughout their lives. This situation produces special results in immunologic testing. Enzyme-linked immunosorbent assay (ELISA) has a sensitivity of 63% and a specificity of 97% with asymptomatic carriers, while the double diffusion arc 5 test (DD5) achieves a sensitivity of only 31% with the same population. On the other hand, imaging studies based on ultrasonography have become the method of choice to detect asymptomatic carriers. Ultrasonography studies are 49% to 73% more sensitive than serological tests, and they can even be used as a part of epidemiological surveillance systems and to monitor control programs. Treatment schemes have also been modernized. Treating asymptomatic carriers chemotherapeutically with albendazole produces favorable results in as many as 69% of cases, while such minimally invasive surgical treatments as puncture-aspiration-injection-reaspiration (PAIR) reduce average cyst volume by as much as 66%. These factors have made it possible for hospital services in the province of Río Negro, Argentina, to establish a treatment scheme for asymptomatic carriers. It is based on the monitoring of small cysts (type Ia on the modified Gharbi scale); initial treatment with albendazole, followed by PAIR if there is no response, in larger or more complex cysts (types Ib, II, and III); and follow-up of inviable or dead cysts (types IV and V).

Long-term outcome of asymptomatic liver hydatidosis.

BACKGROUND/AIMS: The aim of this study was to determine the outcome of asymptomatic liver hydatid cysts in a cohort of 33 out of 59 carriers by evaluating clinical and ultrasonographic (US) changes 10-12 years after initial diagnosis. METHODS: We compared US features and cyst size with the original descriptions from 1984-1986. Patients were questioned about hydatid-related symptoms and signs. RESULTS: Thirty-three of the 59 carriers could be reevaluated, five (15.2%) of whom had undergone surgery without presenting symptoms, while of 28 unoperated cases, 21 (75%) remained asymptomatic. Of the unoperated cases evaluated by US, in 8/14 (57.1%) there were no modifications in cyst size during the 10-12-year period, in five (35.7%) growth was slight (<3 cm) and in one (7.1%) the cyst grew 4 cm. Mean cyst growth in all 14 cases was 0.7 cm. CONCLUSIONS: Despite the limited number of cases, our results show that most asymptomatic liver hydatid cases (75%) remain symptom-free for more than 10 years, regardless of cyst size or type. We believe that such carriers are at low risk of developing complications, so that it is difficult to establish specific rules for their therapy, if any. Longitudinal follow-up of larger series of asymptomatic hepatic hydatidosis cases is essential to gain a deeper insight into the natural history of such patients, and to draw up comprehensive guidelines for treatment.

[Treatment of hepatic hydatid cysts by percutaneous aspiration and hypertonic saline injection: results of a cooperative work]. / Tratamiento de quistes hidatídicos hepáticos por aspiración percutánea e inyección de solución salina hipertónica: resultados de un trabajo cooperativo.

Percutaneous puncture-aspiration-injection-reaspiration (PAIR) of hydatid liver cysts, was performed in 38 patients 14-80 years old, with a total of 60 liver hydatid cysts. After aspiration under computed tomography guidance, hypertonic saline was injected into the cystic cavities of patients as a scolecidal agent. No major complications were associated with the procedures. In the follow-up period of 18 months, control CT scans of 35 cysts revealed a gradual decrease in cyst size with a mean volume reduction of 66%. Complications included two cases of urticaria, one case of anaphylaxis and one subcapsular hematoma. No mortality occurred. It is concluded that percutaneous aspiration and hypertonic saline injection for liver hydatid cysts appears to be an effective form of treatment and may eventually prove to be an alternative to surgical intervention.

Hydatidosis in the province of La Pampa, Argentina, 1998.

Echinococcus granulosus is the agent that causes the classical hydatidosis or cystic echinococcosis. The most spread cycle in South America is the sheep-dog cycle, and offers favorable conditions for the development of the parasite. As the province of La Pampa shows an endemic presence with notification of cases and infected dogs, the present work has the aim of contributing to the study of the distribution and prevalence of the disease in the district of Maracó, La Pampa, Argentina. Dogs of 36 farms that had ovines, were dosed with arecoline hydrobromide at a dose of 3.5 mg/kg. Dogs from 27 (75%) farms resulted positive to Tenia sp. and 3 (8.3%) to E. granulosus. Blood samples were taken to all the people living in all the inquired farm and were processed by the ELISA test for hydatidosis. A retrospective survey on cases of human hydatidosis attended in the Hospital of General Pico, head if the sanitary region, and in two private clinics was performed. Analysis of clinical records indicated 11 cases operated during the period 1996/1997 (annual incidence rate of 6.8 per 100,000 inhabitants). It is of public health interest to fulfill epidemiologic investigations in other districts of the Province of La Pampa with the aim of delimitating the endemic distribution within the province and also organizing surveillance systems on human hydatidosis.

[Hydatidosis/echinococcosis in General Acha, La Pampa Province, Argentina]. / Hidatidosis/equinococosis en el área de General Acha, Provincia de la Pampa, Argentina.

Hydatidosis situation in the General Acha area (La Pampa Province) is described herein. The work comprises a retrospective compilacion of new hydatidosis human cases, the findings in seroepidemiological surveys with enzyme immuno assay (EIA) for hydatidosis in human population, and investigation on dog Echinococcus granulosus infection prevalence carried out on the basis of arecoline bromhydrate application. Sixteen human cases were detected during 1994 (incidence rate: 26.7/100,000), founding a serological prevalence of 1.3%. Studies on dog echinococosis have shown a prevalence rate of 2.3%. The epidemiological situation of hydatidosis is analyzed by comparison with values from other endemic areas. These results suggest the necessity of completing surveys in the whole provincial territory, and the implementation of educational and sanitary measures aimed to controlling this zoonosis.

[Evaluation of ELISA and double diffusion (DD5) test in the diagnosis of human hydatidosis in asymptomatic population]. / Evaluación de ELISA y DD5 en el diagnóstico de la hidatidosis humana en población asintomática.

BACKGROUND: The early diagnosis of Human Hydatidosis through immunologic methods has been one of the most important activities displayed by the Programme of Struggle (fight) in endemic areas of Argentina, to improve the prediction of the Hydatid patient. It is of great interest to define exactly the advantages and limitations of the DD5 and Elisa techniques in the diagnosis of hydatidosis in inhabited areas with no clinic symptoms of the disease. METHODS: For this, the sensibility, the specification and predictive value of both methods has been evaluated, studying serologically 499 inhabitants from a rural community in the Province of Río Negro. The inhabitants with reactive serology to EIE and/or DD5 are studied by means of images using US, RX and TC. A controlled group is selected according to its un-reactive serology. The cases compatible with Hydatidosis are directed to surgery. RESULTS: The DD5 technique is shown as 100% specific but with a sensibility of only 31%; on the other hand, EIE at a cutting level of 8 DE presents a specification of 97% with a sensibility of 63%. CONCLUSIONS: It is important to underline the value of the US as the first image prognosis, while the TC, in the present experience, did not show a great number of positive images, allowing only to confirm the US findings.

[Hydatidosis control in the province of Río Negro, Argentina: evaluation of the veterinary health care activities. 1]. / Control de la hidatidosis en la provincia de Río Negro, Argentina: evaluación actividades de atención veterinaria (1).

BACKGROUND: Hydatidosis constitutes a serious Public Health problem in the Province of Rio Negro, Argentine. This situation has promoted the implementation of a Control Programme, carried out in 1979. The accumulated experience of 13 years works is presented in this study. METHODS: The strategy used is that of the Primary Health Care; and community participation is a fundamental component of the programme as well as local planning and the approach of risk in the allocation of resources. The activities included the systematic dogs deparasitation with Praziquantel, carried out by health agents from the system rural hospitals (health promoters not professional staff); the surveillance of dogs rate of infection by means of diagnostic deparasitations made with hydrobromide or arecoline, educational talks at schools, the use of mass media, an the determination of ovine parasitism in studies carried out in the area abattoirs. RESULTS: The information registered indicates that 1,86,156 dog deparasitations with Praziquantel were carried out with a consumption of 443,533 tablets and 11,178 deparasitations with hydrobromide and Arecoline. A continuous decrease of rates appears during the Period 1979-1992. So, dog Echinococcosis was reduced from 41.5% to 4.24% and ovine Hydatidosis from 61% to 12.7%. Consequently, Human Hydatidosis has decreased from an incidence rate of 64.11 x 100,000 in the age group of 0 to 10 years to and incidence rate of 4.46 x 100,000. CONCLUSIONS: Finally, the results of the Programme are analyzed in the light of other global experiences of control; and the strategies that should be put into practice in the future with a view to a final limitation of the rate of transmission to man are analyzed.

[Community participation and appropriate technology in the early diagnosis of human hydatidosis]. / Participación comunitaria y tecnología apropiada en el diagnóstico precoz de la hidatidosis humana.

The basic strategy for development of hydatid struggle programs is in the actuality: Primary Attention of Health. In the present work and in this instance, it's arm a precocious detection system of hydatid disease, fixed in immunologic diagnostic by means of ELISA technical beginning with blood capillary samples, taken in filter paper by teachers and sanitary agents from official services of Rio Negro Province. 177 teachers and 45 sanitary agents were trained, correspondent to 25 schools, 3 lodging schools and 9 Hospitals all of them from rural area. 890 blood samples during the training were obtained. Lastly, the trained personal armed the system and they obtained 728 samples in the beginning of the Program. It hadn't statistical differences in the reactivity of both samples. The serological prevalence found was 1.32%. The activity displayed by teachers and sanitary agents permitted to detect 21 new cases it was the 20% of new cases diagnosed in this area in the period of work. The viability and the importance of the incorporation of non traditional effectors into the Hydatid Control Programs is discussed.

[Hydatidosis control in the province of Río Negro, Argentina: development of primary care programs]. / Control de la hidatidosis en la provincia de Río Negro, Argentina: evaluación actividades de atención médica.

Hydatidosis is a serious Public Health problem in the Province of Río Negro, Argentina. This situation has promoted the implementation of a control programme based on the canine systematic deparasitation with Praziquantel, health education, work control and care of persons. The accumulated experience of 15 years works, carried out to develop the last work--line mentioned above, is presented in this study. The activities includes the registry of human cases, the early identification of asymptomatic carries, the infected persons derivation to the hospital system in order to allow their appropriate treatment, the longitudinal follow up of the operated cases and the epidemiologic surveillance of the human hydatidosis situation. A network of laboratories was organized, as a support to satisfy the hospital demand, under the coordination of a central laboratory of reference and serologic surveys, among the groups at risk, were also carried out. The information registered indicates that a total of 60,078 serologic tests were carried out in the whole Province: out of them, 22,899 corresponded to hospital demand (DD5) and 37,179 to serologic surveys (originally latex, then DD5, and now Elisa). 65% of the cases, diagnosed by official register, is derived from rural areas to complexity hospitals, to be put under surgical treatment, and, out of these operated persons, only 3.9% is derived from the appearance of clinical symptomatology. A sustained reduction in the average days of stay, in lethality and in the rate of serologic prevalence in school children from 7 to 13 years of age, are achieved.(ABSTRACT TRUNCATED AT 250 WORDS)

[Indicators for the evaluation of the impact of hydatidosis control programs on the health status of a human population]. / Indicadores para la evaluación del impacto de los programas de lucha contra la Hidatidosis en el estado de salud de la población humana.

The importance of measuring the impact of the hydatidosis control program activities on the health of human populations has been emphasized. The different rates used, as well as their limitations defining new hydatidosis cases, are described. The specific incidence rates for the age group of 0-10 years should be considered, together with the standardization of serologic and echographic screening in young groups, in order to achieve the epidemiological evaluation of the control programs impact on a human population in the short term.