Choroby zakaźne Koty

Zakażenie wirusem białaczki kotów. Wytyczne Europejskiej Rady Ekspertów ds. Chorób Kotów. Cz. II

22/11/2018

Kolejne szczepienia

Według najnowszych danych coroczne szczepienie przypominające (po przeprowadzeniu wyżej wymienionych trzech szczepień) może nie być konieczne. W jednym z badań wykazano, że podanie szczepionki z adiuwantem zawierającej inaktywowany wirus FeLV zapewniło odporność na co najmniej dwa lata (Jirjis i wsp., 2010, II stopień EBM). Niedawno na rynek wprowadzona została szczepionka, której producent zapewnia, że wywołuje odporność na trzy lata. Zawiera ona inaktywowany wirus z adiuwantem. Badanie jej skuteczności poprzez zakażenie kontrolne po ośmiu, 20 i 36 miesiącach do szczepienia zostało utrudnione przez wzrastającą z wiekiem oporność kotów na tę infekcję. W efekcie u nieszczepionych kotów z grupy kontrolnej nie doszło w wystarczającym stopniu do rozwoju trwałej wiremii (Wilson i wsp., 2012). Niemniej jednak takie trwałe zakażenie wykazano tylko u jednego z 44 zaszczepionych kotów. Biorąc pod uwagę mniejszą wrażliwość na zakażenie FeLV kotów dorosłych, ABCD zaleca, aby szczepienie przypominające u zwierząt w wieku powyżej trzeciego roku życia wykonywać co dwa do trzech lat.

Zapobieganie białaczce kotów w wybranych sytuacjach

Domy, w których przebywa wiele kotów

Jeżeli u jednego z kotów rozpoznano trwałą wiremię FeLV, to wszystkie koty powinny zostać przebadane. Jeżeli okaże się, że więcej osobników jest zakażonych, wówczas należy wprowadzić program eliminacji FeLV. Polega on na okresowym badaniu wszystkich kotów w tym domu na obecność antygenu p27 we krwi i usuwaniu osobników z trwałą wiremią, aż do czasu, gdy pozostaną tylko koty ujemne. Najlepsza metoda zapobiegania rozprzestrzenianiu się zakażenia polega na izolacji osobników z wiremią FeLV (także przejściową) od niezakażonych kotów. Pomimo że skuteczność szczepionek przeciwko FeLV w większości sytuacji jest dobra, ABCD nie zaleca polegania jedynie na szczepieniu w kwestii ochrony przed FeLV kotów niezakażonych bytujących razem z osobnikami wiremicznymi.

Schroniska

Istnieją duże różnice w rozpowszechnieniu FeLV u kotów w schroniskach w poszczególnych rejonach Europy, co może mieć wpływ na politykę badań i szczepień w tych obiektach. W niektórych krajach, na przykład w Wielkiej Brytanii i w Holandii, prewalencja jest niska, podczas gdy w innych znacząco wyższa, dodatkowo z różnicami pomiędzy poszczególnymi obszarami w obrębie tych krajów.

Gdy tylko jest to możliwe, z uwagi na ryzyko zakażenia FeLV i(lub) FIV wszystkie koty wprowadzane do schroniska powinny być poddawane co najmniej sześciotygodniowej kwarantannie, o ile nie uda się wcześniej oddać ich do adopcji. Wszystkie nowe koty (przynajmniej w sytuacji gdy istnieje ryzyko zakażenia FeLV oraz gdy po kwarantannie możliwy jest kontakt pomiędzy kotami) powinny zostać przebadane na obecność antygenu FeLV oraz przeciwciał przeciw FIV, a najlepiej również metodą PCR na obecność prowirusa FeLV. Brak antygenu p27 we krwi przy jednoczesnej obecności prowirusa FeLV sugeruje, że kot jest zakażony latentnie. Jeśli bada się tylko na obecność antygenu FeLV, ideałem byłoby odizolować też koty ujemne (Möstl i wsp., 2013) i ponownie przebadać je sześć tygodni później, ponieważ od zakażenia do czasu, gdy we krwi zaczyna być wykrywalny antygen, może upłynąć 4-6 tygodni. Po tej kwarantannie osobniki ujemne mogą być wprowadzane do niewielkich grup niezakażonych kotów.

Koty z trwałą wiremią FeLV powinny być izolowane, najlepiej indywidualnie, ale mogą być też trzymane razem z innymi trwale wiremicznymi. Jeśli są klinicznie zdrowe, powinny zostać jak najszybciej oddane do docelowych domów. Należy upewnić się, że nie będą źródłem zakażenia dla innych kotów. Najlepiej więc, jeśli nie będą wychodziły na zewnątrz i trafią do domu, w którym będzie tylko jeden kot albo wszystkie z trwałą wiremią. Idealnie byłoby, gdyby również koty latentnie zakażone FeLV (ujemne w teście na obecność antygenu, ale dodatnie w PCR na obecność prowirusa) były trzymane oddzielnie od niezakażonych FeLV, ponieważ podczas stresu może dojść u nich do reaktywacji zakażenia, wiremii i siewstwa wirusa.

ABCD nie zaleca eutanazji klinicznie zdrowych kotów z trwałą wiremią FeLV. Niemniej jednak jeżeli nie można znaleźć dla nich odpowiedniego domu, izolacja od pozostałych kotów jest niemożliwa lub kot jest chory, wówczas powinno się rozważyć eutanazję.

Hodowle kotów

W większości krajów europejskich FeLV występuje obecnie bardzo rzadko w hodowlach kotów, przede wszystkim wskutek okresowych badań i usuwania z nich osobników z wiremią. Zaleca się, aby rutynowe badania były wykonywane w hodowlach raz lub dwa razy do roku. Kontakty kotów hodowlanych powinny być ograniczone do osobników pochodzących z hodowli, które stosują podobne zasady. Jeżeli kot ma wychodzić na zewnątrz i mieć kontakt ze zwierzętami o nieznanym statusie zakażenia FeLV (co odradza się w przypadku osobników hodowlanych), powinien zostać zaszczepiony.

Zalecenia na temat postępowania w przypadku zakażenia wirusem białaczki kotów zostały po raz pierwszy opublikowane w „Journal of Feline Medicine and Surgery” (nr 11, 2009, str. 565-574), a ich zaktualizowana wersja ukazała się w numerze 15, 2013 (str. 534-535) oraz w numerze 17, 2015 (str. 570-58) tego czasopisma. Niniejszy artykuł został uzupełniony i przygotowany przez Hansa Lutza i wsp. w grudniu 2017.

Odwiedź również stronę: www.abcdcatsvets.org

Redakcja dziękuje prof. dr. hab. Tadeuszowi Frymusowi za pomoc w merytorycznym opracowaniu artykułu

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LITERATURA UZUPEŁNIAJĄCA

• Lutz H, Addie D, Bélak S, Boucraut-Baralon C, Egberink H, Frymus T, et al (2009): Feline leukaemia. ABCD guidelines on prevention and management. J Feline Med Surg 11, 565-574.