Epidemiological study Scabies and syphilis in Slovenia Epuleminwgical trends of scabies and syphilis in Slnvenia A. Kansky, M. Vegnuti and M. Potočnik ABSTRACT Background. Scabies is an infestation by the mite Sarcoptes scabiei, which usually spreads by skin-to- skin contact and is characterized by an intense pruritus. Sexual exposure is a common but not exclusive mode of transmission, it seems to occur in cycles. Syphilis is a well-known and extensively studied sexually transmitted disease. It is basically on decline in developed countries. Materials and methods. Syphilis cases must be reported in Slovenia since 1948 and scabies since 1969. An attempt is being made to find out, whether do infections with scabies and syphilis in the Slovenian population show similar epidemiological trends. The 1969 - 1999 period was investigated. Results. A major peak of scabies infections was observed in 1972 and of syphilis in 1974, a minor one far syphilis in 1979 and far scabies in 1982. Since then the course of scabies was more or less constant whereas syphilis displayed a smaller peak in the years 1993-95. The statistical evaluation according to Pearson showed similar trends in both the conditions. Conclusion. The observed similarity of the trends should be examined carefully, as the observation period far scabies is probably to short to obtain definite evidence on its cyclic course. Introduction Scahies is an infestation caused by the mite Sarcoptes scahiei, which usually spreads by skin-to-skin contacts and is characterized by rather high infectiousness and intense pruritus. The clinical findings are often typical, but in persons observing high hygienic standards the symptoms may be scarce. Overcrowding and sexual contacts are the most common, but not exclusive modes oftransmission (1). The population at risk is the under- privileged, alcoholics, drug aclclicts, homeless persons, refugees, small chilclren in clay care centers, hancli- cappecl persons as well as agecl people in nursing homes. Loss of immunity to scabies was also claimed to be a possible cause of epiclemics, such the01y being promotecl by Shrank (2) as well as by Herrmann ancl Steigleder (3). The changed immunity might be respon- sible for the cycling character of epidemics with intervals of 10 to 15 years (4). Syphilis is a clinically and immunologically well- Acta Dermatoven APA Vol 9, 2000, No 3 ---------------- --105 Scabies and syphilis in Slovenia defined venereal disease which was dreaded in the pre- antibiotic era, because non-treated or not adequately treated it led to severe cardiac and neurological mani- festations. Epidemics of syphilis are known to have occurred in Europe since the years 1494/5 when a severe epidemic erupted in Italy during the war between the kings of France and Naples (5). It is known that in the periods of World Wars I and II and also at the tirne of the great depression in 1929 the incidence of syphilis was high. There are no reliable data for the incidence of syphilis in Slovenia cluring the period of World War II, but in the early fifties about 500 cases were stili registered yearly (6). Simultaneous observations of scabies and syphilis in the same patient as well as of a certain overlapping ofboth the epidemics are facts familiar to dermatovene- reologists and epidemiologists (7). Statistically proved data on their mutual epidemiological relationship are however lacking. The principal reason for the Jack of such an information is the fact that in developed countries scabies is nota notifiable disease and therefore reliable data on the incidence are not available. The aim of the present study was to find out whether in Slovenia during the 1970-1999 period identical or similar epidemiological trends for syphilis and scabies existed. The count1y with approximately 2 million inha- bitants and a relatively strict reporting system for scabies and syphilis seemed to offer a good possibility for carrying out such a comparative stucly. The data on gonorrhea seem to be less reliable due to it responsiveness to various antibiotics ancl to a less consistent reporting, for this reason they were not inclucled into this study. Materials and methods Reliable data on syphilis had been available in Slovenia since 1950 as reporting became obligatory by a federal law (8). A system providing a Central Antive- nereal Dispensary (CAVD, Outpatient Clinic) and a number oflocal antivenereal clispensaries (AVD) inclu- ding a strict reporting were introcluced. The data are stili collected in the Regist1y Otlice at the CAVD, which is located at the Department of Dermatology of the University Medica! Centre in Ljubljana. In view of the decreased number of patients with syphilis and gono- rrhea during the last ten years or so, certain changes of this system took place, the reporting however stili remai- ned operational. The data on the inciclence of scabies had been available since 1970, although the official enforcement by law was introduced by the Slovenian Ministry of Health in 1977 (9). They are regularly collected at the Epiclemiological Unit of the Institute of Public Health in Ljubljana. Clinical records from departments of clermatology throughout Slovenia as well as personal 106 Epidemiological study observation testify that during the 1950-70 period scabies was virtually nonexistent in Slovenia. The above mentioned data collected at the Department of Dermatology (syphilis) ancl at the Institute of Public Health (scabies) were used for the present comparative study. The epiclemiological trencls of both the cliseases during a 30-year period were investigated. For the comparative evaluation the Pearson correlation method was applied assuming a linear relationship between syphilis and scabies. Aclditionally the curve estimation methocl by calculating the best fit on the obse1vecl long-term data of two pairs of variables was examinecl in orcler to fine! out whether some predictions are possible. Results After the syphilis expansion during the post World War II period, the number of patients was on decline. A new peak emerged in 1974, which was followed again by a steep decline. A tiny peak reappeared in 1979, which was again followecl by a clecline, so that in the years 1992 and 1993 only two cases of early syphilis were registered in the entire country, giving an inci- dence of 0.10 per 100.000 inhabitants. Surprisingly syphilis reappeared in 1994 when 36 cases were reported (incidence 1.82). Such a trend continued up to the year 1997 (6,10), when a new regression became evident (Figure 1). The peak-incidence of432 scabies cases per 100.000 was observed in 1972 and was followed by a slow clecline. A new however smaller peak with an incidence of 220 per 100 000 was obse1ved in 1982. After that year the slow decline continued to reach a more or less stable incidence of slightly above 50 in the year 1993 (11) and such a tendency stili persists. At a quick glance, the two curves in Figure 1 repre- senting the counts of patients with syphilis and scabies during the period uncler obse1vation look similar. There may be, however, observecl a tirne shift, the 1972 peak of scabies occurring three years earli er as that of syphilis, while the second, smaller 1979 peak of syphilis appeared three years ahead of scabies. Nonetheless a strong linear relationship is evident (Pearson r=0.82, p>0.001). The major peaks of gonorrhea and scabies disclose a tirne difference of 5 years and their linear relationship is less evident (Figure 2), but is stili stronger than between both sexually transmitted diseases. In such a way the assumption of linear relationship among syphilis and scabies is proved, although in this study we were not able to detect their causal relationship because of lack of data regarding the particularity of not just tirne but also space. We suppose that the association among syphilis and scabies is actually Acta Dermatoven APA Vol 9, 2000, No 3 Epid e mi olog i c al s t u d y generated by different socioeconomic and geographic variables and should be just a consequence of their changes. By this we can fairly explain the moving up and down of both diseases. The next question was the shape of relation bet- ween scabies and syphilis. The approach of the regre- ssion analysis with a single independent variable begins with the assumption of a straight-line model, which seems to be not reasonable for a whole period of 30 years. This estimation seems however, appropriate as both the diseases are on decline. We found that the small number of syphilis cases is followecl by the scabies cases up to 5,000 (250 per 100 000 inhabitants). Uncler this limit the syphilis cases increase quite fast until the epide- mic achieves its saturation ancl starts to clecrease w ithout respect to the possibility that further cases of scabies are adclecl or not after the number 400 per 100 000 inhabitants . The shape of relation between scabies and syphilis which is giving an impression of clependency, should be clescribed by other than linear fit according to their graphical presentation (Figure 1). As we know that the coefficient of correla tion is not a measure of the Scabies No. of cases 10000 9000 8000 6000 4000 3000 syphilis 1975 1980 1985 1990 1995 Syphilis No. of cases 250 200 150 ,oo ., 80 70 60 50 40 30 20 10 Figure 1 . Number of reported cases of scabies and syphilis during the 1971 - 1995 period in Slovenia. Scabies and syphilis in Slovenia SYPHILIS 300 -,--- ------ --------~ 200 100 • Observed o,--"-"'-~ ==--- ~ - -~~--~-----. Gubic O 2000 4000 6000 8000 10000 SCABIES Figure 2. The curve estimation between syphilis and scabies appropriateness of linear model fitting , the