Volume 17 #4 October/December 2010
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Histoty of Medicine The rise and decline of human hydatid disease in Portugal: historical and epidemiological analysis J. A. David de Morais Abstract The author analyses here the official statistics and his own 30- rences being sporadic cases that are, more often than not, the year casuistry about human hydatid disease, for the purpose of result of old infections. As far as the Alentejo is concerned – in the clarifying the fallacious statement that Portugal, in general, and past the largest endemic region of Portugal – there are counties the Alentejo, in particular, is hyper endemic in this parasitical in the districts of Portalegre and Beja that are sine endemic, and zoonosis. Thus, the occurrence of hydatid disease is analyzed some hypo-endemic; only the district of Evora has a few counties at several levels: Country, Great Regions, Alentejo, Evora district, that are meso-endemic and only one that is hyperendemic. and the counties of this district. Key-words: hydatid disease, epidemiology, hydatid disease The final conclusion is that the majority of the Country is, in incidence, Portugal, Alentejo. general, sine endemic in human hydatid disease, the only occur- INTRODUCTION It turns out that for reasons that are not entirely In the past, echinococcosis/hydatidosis began to in- plausible, Portugal is seen as a hyperendemic region crease in clinical and epidemiological importance in of human infection by Echinococcus granulosus,10,11 south Europe. However, good control programs have and hydatidosis is still of great epidemic and clinical managed to significantly control or even eradicate this significance in the Alentejo. Seeking to correct this parasitic zoonosis in the main countries affected. In situation, using the official statistics and our own case Portugal, there is an almost total lack of information studies in the most endemic area of the country, we with regard to echinococcosis, i.e. on the definitive present a detailed analysis of the various parameters infection of the host, the dog (the only global study) that will enable an updated assessment of the evolu- is clearly outdated as it was conducted around forty tion of hydatidosis at national and regional levels. years ago1. With regard to animal hydatidosis, there When we began our investigations on hydatidosis was, until 1968, a large amount of official information in the district of Evora, we started with the obvious, on inspections in slaughterhouses,2 but nowadays, if field studies, i.e. cross-sectional studies.2,8,9 However, such statistics exist, they are incomplete or inaccessi- these cross-sectional studies only give an indicative ble. In relation to human hydatidosis, the official data value of the epidemiological situation, and should are clearly unsatisfactory; however, in conjunction subsequently be complemented by indispensable lon- with the case studies from Evora, the district with the gitudinal studies. The prospective field investigations highest incidence rates in the country, it is possible comprise a simple sampling (in some national studies, to build up a fairly accurate concept of the evolution it was not proved whether the study was statistically of this parasitosis in Portugal, both temporally and significant or representative). In fact, it was only in the 2-9 spatially. study on hospital morbidity that the entire sample of interest was available for consideration. Methodo- logically, it is imperative to move from prospective to retrospective field studies, from epidemiological indicators of prevalence to indicators of incidence – the latter is, in fact, the only indicator of the epidemio- logical situation of a region or country that can be Hydatidology Clinic at the Hospital do Espírito Santo de Evora compared with international indicators. Clearly, for Received for publication on 11/10/09 the analysis of incidence, there are medical records of Received for publication on 04/09/10 patients attended in the national hospitals. Therefore, 246 Medicina Interna REVISTA DA SOCIEDADE PORTUGUESA DE MEDICINA INTERNA HISTORY OF MEDICINE Medicina Interna continuing previous studies,2,9 this paper consists of a outside their place of origin where, in the majority of longitudinal analysis of our own case studies. cases, they acquired the disease many years before. Given that a significant number of National Health This epidemiological error is therefore reflected in Service users undergo echography and other imaging the official statistics. Thus, when putting together exams, it can be said that nowadays, the professionals the epidemiological history of each of our patients, who tend to carry out the ‘screening’ for hydatidosis we inquired, specifically, about theplace of infection: are Family Doctors – gone are the days when General the precise place where the patient was infected, if Practitioners had no additional resources for diag- he/she had always lived in the place where they was nosis - therefore the cases diagnosed and referred to born, or the probable place of infection, if the patient hospitals consist, in the majority of cases, of simple had lived in other places. We then identified, on the imaging findings, since the majority of hydatid cysts above mentioned “Military Map of Portugal” (the are asymptomatic, with only about 10% of patients most detailed map available in the country), the place actually being symptomatic.12 (hamlet, village or settlement) where the patient had acquired the infection, in order to assign the patient MATERIAL AND METHODS to the respective district or county. This study will analyze the statistical material from Another point deserves mention: the number of two different, but complementary sources: cases registered in our consultation is higher than the a) Case studies attended by our Hydatidosis number we have declared. Often we find patients with Consultancy, at Hospital do Espírito Santo de Evora hydatidosis who, for instance, underwent surgery ten, (HESE): these comprise the medical records of 648 fifteen or twenty years previously (often in Lisbon, patients with hydatidosis, which we studied over a to where the patients from the Alentejo used to be period of thirty years (1979-2008), including hyda- referred for surgery, or to where they had migrated for tidosis patients from the entire country. work), and who were now coming to see us due to a b) official statistics: consisting of data available recurrence of the disease, or for clinical reassessment. in the record of “Notifiable Diseases” and cover a Now, these cases have already been (or should have period of twenty-one years (1987-2007) – 1987 being been) declared by the doctors who carried out the the year when notification of hydatidosis was made initial diagnosis, and therefore – a relevant fact – they mandatory - and includes 467 hydatid patients.13,14 do not represent new cases of hydatidosis. Thus, if In the analysis of the various parameters that we we were to notify these cases now, after such a long submitted to statistical analysis, we used, where ap- period of time (usually decades) has elapsed since propriate, the χ2 test and calculations of confidence their diagnosis, this would surely contribute to an intervals (CI) at 95% – in order to avoid committing epidemiological error in the current statistics. Con- “(…) une erreur grossière: le résultat sous forme de sequently, our “notifiable” cases of hydatidosis relate pourcentage n’est pas accompagné de son intervalle de only to newly diagnosed cases. confiance. (…)”15 To determine the incidence of hyda- tidosis per 100,000 inhabitants per year, we used the RESULTS official statistics for the period under study.16 When Country identifying the sites of infection, which is necessary, Our case studies. We shall analyze the most im- verbi gratia, to correctly determine the incidence per portant parameters, from an epidemiological point county, we used the “Military Map of Portugal”, with of view: a scale of 1/25,000. a) The evolutionary pattern in the number of cases. We wish to make our position clear with regard Our cases studied over a 30-year period (1979-2008) to the statistical analysis of our epidemiological case include 648 cases of hydatidosis, of which 646 are studies. In the official statistics – the “Notifiable national citizens and two are foreign citizens (from Diseases” – doctors are required to declare, in the Turkey and South Africa). Since we are interested in notification form, the patients’ place of residence. characterizing the national epidemic-clinical scena- However, with the increasing migration of rural re- rio, we excluded from our analysis the two cases of sidents to urban and suburban areas (as in the case hydatidosis acquired abroad, and will only statistically of the “Alentejo Diaspora”), many patients now live analyze the 646 clinical cases related to our coun- PUBLICAÇÃO TRIMESTRAL 247 VOL.17 | Nº 4 | OUT/DEZ 2010 HISTORY OF MEDICINE Medicina Interna TABLE I 50 Hydatidology Clinic (HESE): Hydatidosis cases per year 45 and per five-year period 40 35 30 Year Hydatidosis cases 25 20 Per Year Per five-year period 15 n n % CI* 10 5 1979 24 0 1980 23 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 1981 18 1982 15 Hydatidology Clinic (HESE): Hydatidosis cases throughout the years. 1983 18 FIG. 1 98 15,2 12,5-18,2 FIG. 1 1984 26 1985 33 1986 34 and 1993. This fact was the result of the decision, 1987 34 1988 42 by a director of our hospital, to refer patients with 169 26,2 22,8-29,7 hydatidosis to our internists, whereas previously they were referred to our infirmary. This meant that 1989 44 many patients with hydatidosis were transferred to 1990 26 1991 18 the Central Hospitals in Lisbon, or were not officially 1992 17 reported. However, in 1994, when we implemented 1993 30 the Consultation for Hydatidosis Cases, the situation 135 20,9 17,8-24,2 returned to normal.