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Euro Surveill. Tick-borne encephalitis transmitted by unpasteurised cow milk in western Hungary, September to October 2011

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  • Euro Surveill. Tick-borne encephalitis transmitted by unpasteurised cow milk in western Hungary, September to October 2011

    [Source: Eurosurveillance, full text: (LINK). Abstract, edited.]
    Eurosurveillance, Volume 17, Issue 12, 22 March 2012

    Rapid communications


    Tick-borne encephalitis transmitted by unpasteurised cow milk in western Hungary, September to October 2011


    S Caini<SUP>1</SUP><SUP>,2</SUP>, K Szomor<SUP>3</SUP>, E Ferenczi<SUP>3</SUP>, ? Sz?kelyn? G?sp?r<SUP>4</SUP>, ? Csoh?n<SUP>2</SUP>, K Krisztalovics<SUP>2</SUP>, Z Moln?r<SUP>2</SUP>, J K Horv?th ()<SUP>2</SUP>
    1. European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
    2. Department of Infectious Disease Epidemiology, National Center for Epidemiology, Budapest, Hungary
    3. National Reference Laboratory for Viral Zoonoses, National Center for Epidemiology, Budapest, Hungary
    4. K?rmendi, Őriszentp?teri, Szentgotth?rdi, Vasv?ri Public Health Institute Service; Policy administration service of public health, Vas County Government Office, K?rmend, Hungary
    <HR>
    Citation style for this article: Caini S, Szomor K, Ferenczi E, Sz?kelyn? G?sp?r ?, Csoh?n ?, Krisztalovics K, Moln?r Z, Horv?th JK. Tick-borne encephalitis transmitted by unpasteurised cow milk in western Hungary, September to October 2011. Euro Surveill. 2012;17(12):pii=20128. Available online: http://www.eurosurveillance.org/View...rticleId=20128
    Date of submission: 02 March 2012
    <HR>In October 2011, a cluster of four tick-borne encephalitis (TBE) cases was identified in Hungary. Initial investigations revealed a possible link with consumption of unpasteurised cow milk sold by a farmer without authorisation. We performed a cohort study including all regular customers of the farmer. Overall, eleven cases (seven confirmed and four suspected) were identified. Customers who had consumed the farmer?s unpasteurised cow milk had more than a two-fold increased risk for being a TBE case, although not at statistically significant level.
    - ------

  • #2
    Re: Euro Surveill. Tick-borne encephalitis transmitted by unpasteurised cow milk in western Hungary, September to October 2011

    Published Date: 2012-03-23 18:46:14
    Subject: PRO/AH/EDR> Tick-borne encephalitis - Hungary
    Archive Number: 20120323.1079163

    TICK-BORNE ENCEPHALITIS - HUNGARY
    *********************************
    A ProMED-mail post
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    ProMED-mail is a program of the
    International Society for Infectious Diseases
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    Date: Thu 22 Mar 2012
    Source: Eurosurveillance 2012, Volume 17, Issue 12 [summ., edited]
    In October 2011, a cluster of four tick-borne encephalitis (TBE) cases was identified in Hungary. Initial investigations revealed a possible link with consumption of unpasteurised cow milk sold by a farmer without authorisation. We performed a cohort study including all regular customers of the farmer. Overall, eleven cases (seven confirmed and four suspected) were identified. Customers who had consumed the farmer&apos;s unpasteurised cow milk had more than a two-fold increased risk for being a TBE case, although not at statistically significant level.



    Reference: Caini S, Szomor K, Ferenczi E, Szekelyne Gaspar, A Csohan, Krisztalovics K, Molnar Z, Horvath JK. Tick-borne encephalitis transmitted by unpasteurised cow milk in western Hungary, September to October 2011.

    Abstract
    In October 2011, a cluster of 4 tick-borne encephalitis (TBE) cases was identified in Hungary. Initial investigations revealed a possible link with consumption of unpasteurised cow milk sold by a farmer without authorisation. We performed a cohort study including all regular customers of the farmer. Overall, 11 cases (7 confirmed and 4 suspected) were identified. Customers who had consumed the farmer's unpasteurised cow milk had more than a 2-fold increased risk for being a TBE case, although not at statistically significant level.

    Introduction
    On 14 Oct 2011, the Department of Infectious Disease Epidemiology at the National Center of Epidemiology (NCE) in Budapest was alerted about a cluster of 4 hospitalised tick-borne encephalitis (TBE) cases that had occurred between 19 Sep - 1 Oct 2011, in the area surrounding K, a small town in western Hungary close to the Austrian border. All 4 patients had already been interviewed by local public health authorities when NCE was alerted: none of them could remember having recently been bitten by a tick, but all of them referred to having consumed unpasteurised cow milk during the incubation period, which had been purchased from a farmer who has 10 dairy cows producing about 70 litres milk per day. The milk of this farmer was sold without being pasteurised and without authorisation, to regular customers from approximately 40 families residing in 4 villages in the countryside surrounding K. The farmer was forbidden to sell milk on 14 Oct 2011. On 18 Oct [2011], 2 epidemiologists from NCE went to K to help local public health staff with the epidemiological investigation.

    The tick-borne encephalitis virus (TBEV) is an RNA virus belonging to the genus Flavivirus, family Flaviviridae. 3 subtypes are described: European (the most common subtype in Europe), Siberian and Far Eastern. TBEV is transmitted by ticks, _Ixodes ricinus_ being the most common vector in central Europe. The virus can be transmitted by bites of infective ticks or, less frequently (but more successfully and with a shorter incubation period), by consumption of unpasteurised milk from infected animals. Approximately 2/3 of human TBE virus infections are asymptomatic. In clinical cases, TBE often has a biphasic course: after an incubation period of 7 - 14 days, infected people develop aspecific symptoms lasting approximately one week (1st phase), followed, after a few days, by neurological symptoms (2nd phase) in approximately 1/3 of those who experience 1st-phase symptoms. The case fatality ratio is around 1 - 3 per cent for the European and Siberian subtypes and 20 per cent for the Far Eastern subtype. Vaccine for the prevention of TBE is available. In Hungary, groups at risk such as forest workers, geologists and laboratory workers are advised to get vaccinated.

    Results
    Overall, 11 cases (7 females, median age 44 years, range 1 - 85) of TBE were reported (7 confirmed, including the 4 cases initially reported, and 4 suspected). One of the suspected cases, who was included in the cohort, had been hospitalised with clinical symptoms on TBE prior to NCE being alerted of the TBE cluster. This person had eventually died without having been tested for TBE virus. Of all cases (n=11), only the 4 initially reported cases suffered from encephalitis. The 7 confirmed (altogether 11) TBE cases clustered in 6 (altogether 7) of the 36 families in the cohort.

    Discussion
    To our knowledge, this is the 1st report of a TBE outbreak supposedly transmitted by unpasteurised cow milk in the European Union (EU). Other reports were published about TBE outbreaks in the EU transmitted by goat and sheep milk. A TBE outbreak transmitted by cow milk was previously described in eastern Russia (close to the border with North Korea) where the Siberian and Far Eastern subtypes of TBE virus are more common than the European subtype.

    Milk samples taken from the cows tested negative for TBEV. This is not fully surprising considering that the milk samples were taken on 2 Nov [2011]; i.e., 15 days after the last (suspected) case was observed. Balogh et al showed that experimentally infected goats can shed TBEV in milk for more than 20 days after infection, but no data exist about persistence of TBEV in milk of infected cows.

    The potential for the spreading of infectious diseases by drinking unpasteurised cow milk is well known. Concerning TBE, the proportion of cases infected via unpasteurised milk has been estimated to be 0.9 per cent in Czech Republic from 1997 to 2008 [9] and 9 per cent in Slovakia. Cisak et al found that more than 20 per cent of goat and sheep milk samples and 11 per cent of cow milk samples tested positive for TBEV in a survey in eastern Poland, an area with high incidence of TBE. Considering that cow milk is far more frequently consumed than goat and sheep milk, and that the habit of buying milk from small farmers (that may not fulfil all requirements for milk safety) is not rare, especially in the countryside, implication of consuming unpasteurised cow milk as cause of TBE outbreaks should not be overlooked.

    TBE transmitted by unpasteurised milk could be effectively prevented by vaccinating people and/or dairy animals; although it is not clear yet how long the immunity against TBEV persists in animals. However, many other infective agents (Mycobacterium bovis, Brucella spp., Campylobacter spp., Streptococcus spp., etc) may be transmitted by milk for which a vaccine is not available. Therefore, public health services should primarily focus their efforts towards prohibiting the sale of milk by farmers without authorisation and informing the public about the risks associated with consumption of unpasteurised milk and the beneficial effects of boiling such milk before drinking or processing it.

    --
    Communicated by:
    ProMED-mail from HealthMap Alerts
    <promed@promedmail.org>

    [Unfortunately, there is a lingering belief amongst some consumers that raw (unpasteurized) milk is more healthful or nutritious than pasteurized milk, despite lack of scientific evidence to support that belief. The above report is yet another example of the risks that consumption of raw milk may may bring in the areas where TBE virus is endemic. Last year (2011), there were cases of TBE virus infection in Russia from the consumption of raw goat milk, where raw goat milk is an established source of TBE infection during the epidemic season. Goat milk is preferentially given to children since it is less allergenic (see ProMED-mail archive no. 20110520.1531).

    The highest rates of TBE virus infection occur in Slovenia and the Czech Republic, although prior to the institution of mass vaccination in 1981, Austria reported the highest rates of tick-borne encephalitis in Western Europe. Recently, Germany also had high rates of TBE virus infection (see ProMED-mail archive nos. 20110711.2092 and 20110520.1531].

    A HealthMap/ProMED-mail interactive map of Hungary can be accessed at http://healthmap.org/r/20O6. - Mod.TY]

    See Also


    2011
    ----
    Tick-borne encephalitis - Austria (02): correction 20110712.2102
    Tick-borne encephalitis - Austria (02): background 20110711.2092
    Tick borne encephalitis - Russia: (KG), goat milk 20110520.1531]
    .................................................t y/ejp/lm

    Twitter: @RonanKelly13
    The views expressed are mine alone and do not represent the views of my employer or any other person or organization.

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