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COMMUNICABLE DISEASE SURVEILLANCE IN CROATIA

n    Communicable disease case notification in August

S a l m o n e l l o s i s. Incidence raised in August (609:557) but this was less than in August last year (609:651). Clusters are seen in Slavonski Brod (20), Vinkovci (24), Sibenik (53), Dubrovnik (33), Ivanec (20), Zagreb Pescenica (22) and Novi  Zagreb (31).

T o x i i n f e c t i o  a l i m e n t a r i s (food poisoning). It should be noted that this entity (characterized by vomiting, enteral symptoms and fever), may contain also cases of gastroenteritis which are clinically equal but not necessarily foodborn as there is no "gastroenteritis" in the list of notifiable diseases. In August, intensity of this syndrome  is increased comparing to July (428:375) which is also higher than in august last year (324). Clusters are seen in  Zadar (27), Brac (41), Omis (33) and Trogir (34).

H e p a t i t i s  A. (epidemic jaundice). Only one cases recorded in August.

T e t a n u s.  In August 1 case was reported from Bjelovar (elderly unvaccinated female).

M o r b i l l i  (measles). No cases in August due to systematic vaccination

R u b e l l a. No cases in August due to systematic vaccination.

V a r i c e l l a (chicken pox). Seasonal decrease continued  (451:1665). The intensity similar to August last year (475).

P a r o t i t i s   e p i d e m i c a (mumps). Favorable effect of mass immunization is seen also in this disease occurring only in 4 cases in August.

M e n i n g i t i s   v i r o s a  (aseptic). Continuation of seasonal increase. (158:99). Intensity higher than last year (52, see ENEWS 7/2006).

M a l a r i a. One case reported from Rijeka, imported from Nigeria.

n      No reports in August from: Grubisno Polje, Djurdjevac and Lastovo. Total: 3 out of 113 epidemiological districts.

n      Epidemic outbreaks

        Following outbreaks were reported in August:

Note: in all outbreaks mentioned here, epidemiological investigation and necessary measures were undertaken, preventing thus other potential cases.

Zabok – family outbreak of salmonellosis (S . typhimurium) on 23.6.2006. There were 7 diseased out of 7 exposed after a meal of panned chicken .

Vinkovci – salmonella food poisoning (S. enteritidis) in a family. There were 5 diseased out of 26 participants of a family celebration. Vehicle epidemiologically and microbiologically: cherry cake. Salmonella found in cake samples.

Opatija – salmonella food poisoning (S. enteritidis) on a wedding party. Between 27.6. and  29.6. 2006. There were 8 diseased among 20 persons eating home made cake. Cake was not microbiologically examined.

Zagreb Centar – salmonella food poisoning (S. enteritidis) on 29.6. 2006 in a restaurant. There were 30 diseased out of 200 exposed. Vehicle not found with certainty among several dished offered. Microbiological examination of various dishes turned negative.

Novska – food poisoning in a group of people eating home made cakes.  There were 3 diseased out of 9 exposed persons.

Brac – salmonella foods poisoning (S. enteritidis) in a hotel. There were 5 diseased out of 180 guests between 30.6. and 1.7. 2006. Vehicle epidemiologically: sweet made from eggs called "paradizot" (Schneenockerln in German). salmonella was find in eggs used for preparation.

Slavonski Brod – salmonellosis (S. enteritidis). Between 22.7. and 27.7 2006. there were 14 cases out of 22 persons exposed to a fruit cake called "Japanese wind", purchased in a pastry shop in another county. Salmonella carriership found among pastry shop staff.

Pula - salmonella food poisoning (S. derby)  in a group of workers on 3.8. 2006. There were 6 cases out of 50 exposed. Source not found. Vehicle epidemiologically: stew with noodles.

Porec – acute gastroenteritis of unknown etiology (laboratory examinations negative, possible viral etiology) among members of a camp staff.  Between 7.8. and 9.8. 2006 there were 11 diseased. Mode of spread: contact. No cases among guests.

Sisak – gastroenteritis of  unknown etiology (laboratory tests negative). In a hospital. Between 10.8. and 17.8. 20065. there were 10 cases.  Source not found. Mode of spread probably indirect contact.

Sisak – salmonella food poisoning (S. enteritidis) in a factory canteen on 12.8.2006. There were 30 diseased out of 101 exposed persons. Vehicle epidemiologically and microbiologically: paned fish. Salmonella found in frozen fish filet  samples.

Varazdin – febrile gastroenteritis of unknown etiology, starting 23.8. 2006. in a group of workers. Vehicle: deer stew with pasta. There were 5 out of 65 exposed. Causative agent not found, laboratory tests negative.

NEWS AND COMMENTS

n      Legionellosis, sampling and interpretation of test results

Legionnaires disease and its prevention and control has been one of important topics in our epidemiology practice for decades, i.e. since the early eighties, when the first article on preventing legionnaires disease had been published in the Epidemiological news (ENEWS 9/1983). Laboratory techniques and experience have improved since then, giving now more insight into microbiology and ecology of legionellae. Here we are giving an updated information on current possibilities for legionella detection in our country along with some guidelines for sampling and for the interpretation of results of legionella detection in water samples.

The isolation of legionella from biological material or water samples is usually performed in two steps:

a) cultivation on selective media, after thermic or chemical inactivation of other bacterial flora, and in a case of positive growth:

b) identification of cultivated legionellae by a direct imunofluorescence testing (DFA) using standard antibodies for different legionella serogroups.

Legionella presence can be directly demonstrated too, by antigen detection using DFA or PCR technique. But, in environmental samples, like potable water etc, one should consider that positive finding i.e. microbes demonstrated could be inactive (dead) through previous chemical disinfection, pasteurization etc.

Detecting legionella antigen in patients' urine can be useful for clinical practice, as this test can be positive before demonstrable antibodies appear in patients' sera. However, only Legionella pneumophila of serogroup 1 can be detected.

Serum antibodies are usually assessed by indirect imunofluorescence tests (IFA) with possibility of identification different legionella strains using standard pools of antigens (polyvalent).

Few basic guidelines for taking and sending samples:

      Water

Improved laboratory techniques and experience allows taking water samples that should not  necessary be of several liters (5 or even 10). A sample of 1 liter is usually enough. Bottles should be sterile as in all microbiological examinations, however. One liter sample approach applies particularly for outbreak situations when high concentrations of legionella are expected. Still, in cases of some special investigations or preventive legionella risk assessment samples may be larger.

     Serum

Samples are taken in a standard way, which means optimally as two (paired) samples, taken two weeks to one month apart, in order to demonstrate significant antibody titer dynamics (raise). But they should be sent consecutively because sometimes already the first sample contains significantly high titers, so second sample may not be necessary, depending on the purpose of testing.

    Other biological samples (sputum, bronchial lavate, post mortem tissue etc.)

Should be stored and sent in plastic sterile embalage, at refrigerator temperatures  (cca +4^oC; transport cooling bag etc.) in cases when less than 24 h are needed to reach a laboratory. If this time is longer, samples should be stored and sent at -70^oC temperature.

As a consequence of improved laboratory routines, positive findings are observed more often in human as well as in environmental samples tested. This was expected however, as legionellae are ubiquitous and widely present in wet soil, surface waters etc, with constant potential possibility of their entrance into various water systems, either at the moment of  construction, or later, after some technical damages and repairs, or through inevitably present minor damages on every water supply network in circumstances of water loses and consecutive underpressure conditions in a system. This all should remind us of the necessity of constant monitoring of all public water supply networks, as well as of a need for constant presence of residual disinfection in systems regardless to original quality of water at a point of uptake, in addition, also, continuous use of water is important, in order to avoid stagnant situations and unwanted legionella growth in water.  As  is well-known, small numbers of legionellae in water are harmless to people, while huge numbers which can be generated in an improperly maintained water system, can cause, in immunocompromised persons, illness and even death.     

So, in interpretation of positive findings in water samples, a quantification i.e. legionella count in defined volume unit  of the sample examined (1 ml, 1 l etc.) is often useful. However one should take into account laboratory procedure that preceded certain numerical result, as that number is obtained by calculation after counting bacterial units only in a small portion of the entire sample, which itself was obtained from the original sample by concentration, so numbers can easily be distorted. Because of that, they can only be used as a very rough orientation and certain help in decision making regarding necessary measures, while epidemiological field investigation and information of real outbreak situation are still of primary importance. The table bellow, with rough orientation criteria for legionella count assessment, takes into consideration similar tables and criteria of the EWGLY and various other bodies and institutions in the world, dealing with legionella laboratory detection, water supply systems,  pools, cooling towers etc., but also the own experience of our microbiological laboratories and epidemiology services. In some of the published criteria assessment differs with respect of the  type of water sample i.e. potable water, cooling tower water, humidifier etc. However generally there is not much practical difference in potentials of causing disease in cases of exposition to shower in a bathroom, or in pool with bubbles, or from cooling tower (in these cases more persons could be exposed). So we created a single universal table (still only as a rough orientation) applicable to various types of samples, leaving always a possibility for specific individual assessment and decision.

The legionella count (number) can be obtained either by cultivation and counting colonies (CFU, colony forming units) or by counting fluorescent, morphologically intact bacteria in a DFA testing.

Table 1

At the bottom of the table above, parameters for total bacteria count are also given, as this test is also often performed in water analyses. Any bacteria, pseudomonas etc. when present in huge quantities in water, can cause some disease in humans exposed, and additionally this can mask (by mutual competition) legionella presence in cultivation attempts.

COMMUNICABLE DISEASES IN CROATIA                         August 2006