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.

Seroepidemiology of human hydatidosis: use of dried blood samples on filter paper.

Programmes for the control of hydatidosis caused by Echinococcus granulosus in Argentina use an enzyme immunoassay (EIA) as a screening test for population surveys aimed at detecting asymptomatic patients. Persons thus selected are referred to health centres for the arc 5 double diffusion test and imaging techniques. One of the most costly procedures of these surveys is the collection of blood samples under field conditions; the possibility of collecting dry blood samples on filter paper was therefore investigated. In a survey of 497 rural inhabitants of an endemic area, the same number of hydatidosis cases (22) were identified by EIA using (i) serum samples and (ii) capillary blood samples obtained by finger prick and collected on filter paper. The latter system was both simpler and cheaper.

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.

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%.

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.

[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.

[Human hydatidosis: field echography for the determination of groups at high risk in the evaluation of a control program]. / Hidatidosis humana: ecografía de campo para la determinación de grupos de alto riesgo en la evaluación de un programa de control.

The development of small ultrasonographic equipment has permitted to incorporate this technique to the methods of early detection of Human Hydatidosis. 689 echographies were carried out in this experience, and 5.51% of compatible images in the whole population, and 12.24% in groups of risk (those living together with the operated ones) were found. It was observed a significant decrease in the infection percentages in man in the whole population of areas under Control Program, using the echographic screening. In conclusion, echography might be incorporated to the epidemiologic surveillance system of human Hydatidosis.

Hantavirus pulmonary syndrome in the Province of Rio Negro, Argentina, 1993-1996.

Early in 1995 the first case of Hantavirus Pulmonary Syndrome was serologically confirmed in El Bolsón (Province of Río Negro, Argentina), corresponding to the third outbreak reported in Argentina. A total of 26 cases of HPS related to the Andean region of Rio Negro Province, were reported from 1993 to 1996, 17 in El Bolsón, 4 in San Carlos de Bariloche, and 5 in Buenos Aires. The incidence rate was 5.03 x 100,000 with a mortality rate of 51.85 x 100. The occurrence of cases was mainly seasonal, with a significantly greater number in the spring, and the persons affected mainly lived in urban or periurban areas. In four cases, the affected individuals were members of a couple, spouses or live-in contacts. Seven cases were Health workers (physicians, nurses or administrative staff). Twelve cases were related among them, due to an outbreak of 80 days. Two of them did not visit the Andean region. A total of 139 rodents were captured and seven of them, Olygoryzomys longicaudatus, were found to be serologically positive. The possibility of infection by contact with rodents or fecal matter is being analyzed and also hypothesis related with interhuman transmission.

[Discontinuation of treatment in epileptic seizures in adolescence]. / Arrêt du traitement dans les crises épileptiques de l'adolescence.

A retrospective survey on the frequency of seizure-recurrence after drug withdrawal in all forms of adolescent seizures has been undertaken to detect possible prognostic criteria. Patients were selected according to 3 criteria: first seizure between 11 and 19 years of age; out-patients seen by one of us between 1955 and 1979 within the year of onset of epilepsy; all patients followed for at least 5 years after the first seizure. Two-hundred and seventy two patients entered the study. One-hundred and four patients (49 per cent) relapsed, most of them (83 per cent) within the first year after drug withdrawal. In univariate analysis, partial seizures, a normal initial EEG, an isolated seizure, a short length of illness, a long seizure-free period, one seizure only during the first year were significantly linked to a low relapse rate. The probability of being seizure-free after drug withdrawal was about 73 per cent in partial epilepsy, 20 per cent in idiopathic generalized epilepsy, and 36 per cent in undetermined generalized epilepsy. In patients having had a single seizure a dramatic difference was noted according to the seizure type: 12 per cent of relapses after a partial seizure, 69 per cent after a generalized seizure. Neither the age of onset of epilepsy nor the presence of an etiological factor were significant variables in predicting the outcome. When all factors were analysed simultaneously with Cox's hazard function, the type of seizure and the initial EEG appeared to be the only two independent factors significant for a risk of relapse.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

[Echographic specificity in the early diagnosis of human hydatidosis]. / Especificidad de la ecografía en el diagnóstico precoz de la hidatidosis humana.

Ultrasonography (US) were used for screening of hydatid disease in 1321 asymptomatic individuals fron Río Negro Province, Argentina. A total of 76 positive subjects were identified with possible hydatid disease. Surgery was performed in 30 patients, conforming in 28 of them sonographic diagnosis (93.34%).

[An echographic, serologic and radiologic register of human hydatidosis. Contributions to a control program]. / Catastro ecográfico, serológico y radiológico en hidatidosis humana. Aporte a un programa de control.

Between June and November 1984, 904 asymptomatic people from endemic areas of hydatidosis in Rio Negro, Argentina, were studied by means of ultrasonography (U.S.) and double diffusion for arc five (dd5). The population included 272 inhabitants from Pilcaniyeu, 55 patients from the Zonal Bariloche Hospital admitted for diseases other than hydatidosis and 577 recruits from different departments of the Rio Negro Province. A chest X-ray was performed in every recruits. 47 (5.20%) cases of hepatic hydatidosis were detected by U.S.; 11 (1.22%) were detected by dd5 (p 0.01); 2 (0.34%) were detected by chest X-ray. Due to the low sensitivity of dd5 a presumptive diagnosis of hydatidosis should be made in every patient proceeding from an endemic area with a liver cyst diagnosed by ultrasound, even if dd5 is negative. U.S. must be incorporated as an elective method associated with chest X-ray and dd5 in epidemiological yielding and monitoring of control programs for hydatidosis.

Hirayama disease: three cases.

Hirayama disease is a rare, lower cervical myelopathy affecting young adults. It is responsible for pure distal motor impairment of the upper limbs, with slow progressive development in the metameric territories of C7 to T1. It is thought to be caused by movements involved in flexing the neck. Neutral position magnetic resonance imaging (MRI) looks for abnormal cervical curvature, atrophy with flattening of the cervical spine, anterior cord hyperintensity and especially a lack of posterior apposition of the dural sac. If the condition is suspected, an MRI in flexion should be performed to show anterior displacement of the cord and dural sac, enlargement of the posterior epidural space, an increase in flattening of the cord and congestion of the epidural veins. These dynamic abnormalities tend to disappear after evolving for 10 years. We report two confirmed cases and a probable case of Hirayama disease and discuss its physiopathology.

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.

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.

[Epidemiologic surveillance of hydatidosis in the Patagonian region, Argentina: 1983-1988]. / Vigilancia epidemiológica de la hidatidosis en la Región Patagónica, Argentina: 1983-1988.

The results of a control program of hydatid disease in five jurisdictions of the Patagonian Region in Argentina are presented. The information is glossed in rates of infection in man (95 x 100,000 in 1988 and 15 x 100,000 in 1983), dogs (21.6% in 1983 and 3.1% in 1988) and sheep (16.6% in 1983 and 2.6% in 1988). Factors that condition the endemic situation of hydatidosis in the region are discussed.

[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.

[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.