Ascaridia galli in laying hens: Adaptation of a targeted treatment strategy with attention to anthelmintic resistance

Behdad Tarbiat

Ascaridia galli in laying hens: Adaptation of a targeted treatment strategy with attention to anthelmintic resistance

Behdad Tarbiat

Publikation: Avhandling › Doktorsavhandling

Sammanfattning

Populärvetenskaplig sammanfattning. Ascaridia galli (Nematoda: Ascaridiidae) är en rundmask som infekterar hönsfåglar. Parasiten har en direkt livscykel som inkluderar parasitägg i miljön (fjäderfästallar och inhägnader utomhus), samt larver och vuxna maskar i tunntarmen hos dess värddjur. Hos värphöns är kraftig maskinfektion förknippad med nedsatt djurhälsa och produktionsbortfall. Sedan de konventionella oinredda burarna för värphöns förbjöds inom EU 2012 har förekomsten av A. galli ökat i flera europeiska länder. Anthelmintikabehandling i kombination med rengöring och desinfektion av stallarna mellan olika produktionsomgångar är centralt för att bibehålla låg parasitbörda i infekterade flockar. Behandlingen (avmaskningen) påbörjas tidigast när parasitägg detekteras i träckprov eller när producenterna upptäcker maskar i avföring eller om hönsens hälsa är nedsatt. I de två senare fallen har hönsen oftast redan en hög parasitbörda vilket innebär att miljösmittan med parasitägg också är hög. Avhandlingens mål var att öka kunskapen om behandlingsstrategier mot A. galli genom att; A) ta fram kunskap om infektionsdynamiken hos A. galli i relation till avmaskning i kommersiella värphönsbesättningar, B) validera en avmaskningsstrategi baserad på riktad behandling och C) utvärdera olika testmetoder för detektion och övervakning av anthelmintikaresistens. Vår studie om effektiviteten hos avmaskningsmedlet flubendazol (FLBZ) som användes vid behandling av A. galli under pågående äggproduktion i två flockar på olika gårdar visade att FLBZ var effektivt mot samtliga parasitära utvecklingsstadier. Däremot återinfekterades hönorna inom en vecka efter avmaskningen vilket visar att effekten var kortvarig. Vår slutsats är att dagens användning av anthelmintika behöver förbättras. Hos en svensk äggproducent jämfördes under 38 veckor effekterna av tidigarelagd riktad anthelmintikabehandling med de i en konventionell avmaskningsstrategi senare under produktionscykeln liksom i en obehandlad kontrollgrupp. Hönsen i stallet med riktad avmaskning hade ett signifikant lägre antal maskar och utskiljde färre ägg än de två övriga grupperna. Däremot noterades inga skillnader avseende parasitförekomst eller äggutskiljning hos hönorna i den konventionella behandlingsgruppen och hos de i den obehandlade kontrollgruppen. Vår slutsats är att en enda behandling relativt sent under produktionscykeln är suboptimalt eftersom den inte förebygger uppbyggnaden av miljösmitta med parasitägg. Riktad tidigarelagd behandling är följaktligen att föredra framför en enstaka behandling senare under produktionscykeln. En nackdel är dock att det krävs flera behandlingar för att uppnå långsiktig parasitkontroll. Resultaten av äggräkning och parasitlarvsutveckling visade inga tecken på förekomst av anthelmintikaresistens på den undersökta gården. Även undersökning av sambandet mellan olika mutationer på β-tubulin isotyp 1 vid kodonen 167, 189 och 200 gav stöd för att anthelmintikaresistens inte förelåg.

Originalspråk	Engelska
Kvalifikation	Doktor i filosofi
Förlag	Swedish University of Agricultural Sciences
Tryckta ISBN	978-91-7760-244-6
Elektroniska ISBN	978-91-7760-245-3
Status	Publicerad - 2018

Nyckelord

B-tubulin
ascaridiosis
benzimidazole
chicken
control strategy
parasite egg
poultry

SLU-serie

Acta Universitatis Agriculturae Sueciae

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title = "Ascaridia galli in laying hens: Adaptation of a targeted treatment strategy with attention to anthelmintic resistance",

abstract = "Ascaridia galli is a round-worm of wild and domesticated fowl in the Ascaridiidae family within phylum Nematoda. The direct life cycle includes free-living parasite eggs in the environment and larvae and adults worms in the small intestine of the host. Infection is associated with reduced health and production losses in laying hens. Since the EU ban on conventional battery cages in 2012, the occurrence of A. galli has increased markedly in many European countries. Treatment with anthelmintic drugs along with biosecurity measures and cleaning and disinfection of barns between flocks are central to control programmes. Treatment usually starts when parasite eggs are detected in faecal samples or when farmers observe worm expulsion or health impairment. At this late stage, the infection level and barn contamination with parasite eggs are often already high. This thesis therefore set out with the aim to gain more knowledge on optimal anthelmintic treatment strategies against A. galli by A) providing knowledge on the infection dynamics of A. galli in relation to deworming, B) validating a deworming strategy based on targeted treatment and C) apply tests for the detection and monitoring of AR . We showed that FLBZ was highly effective against all A. galli stages under field condition on two farms. However, the hens became re-infected within a week post treatment. We concluded that the way anthelmintics are used on farms needs to be refined. Comparison of the TT strategy and single treatment strategy (CT) with untreated control groups (UT) showed that barn contamination with parasite eggs, individual faecal egg counts (FEC) and worm burdens were lower in flocks where the TT strategy was applied. No significant difference was observed between the CT and UT flocks with regard to worm burden and FEC. We concluded that a single treatment late during the production cycle is suboptimal and cannot prevent the build-up of infection and barn contamination. We recommended that the TT strategy should be considered a better alternative to a single treatment late during production. Investigation into mutations of the β-tubulin isotype 1 gene at codon 167, 189 and 200 showed no evidence of AR. Moreover, the results of the faecal egg count reduction test and the larval development test did not point at existence of AR on the investigated farm.",

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AB - Ascaridia galli is a round-worm of wild and domesticated fowl in the Ascaridiidae family within phylum Nematoda. The direct life cycle includes free-living parasite eggs in the environment and larvae and adults worms in the small intestine of the host. Infection is associated with reduced health and production losses in laying hens. Since the EU ban on conventional battery cages in 2012, the occurrence of A. galli has increased markedly in many European countries. Treatment with anthelmintic drugs along with biosecurity measures and cleaning and disinfection of barns between flocks are central to control programmes. Treatment usually starts when parasite eggs are detected in faecal samples or when farmers observe worm expulsion or health impairment. At this late stage, the infection level and barn contamination with parasite eggs are often already high. This thesis therefore set out with the aim to gain more knowledge on optimal anthelmintic treatment strategies against A. galli by A) providing knowledge on the infection dynamics of A. galli in relation to deworming, B) validating a deworming strategy based on targeted treatment and C) apply tests for the detection and monitoring of AR . We showed that FLBZ was highly effective against all A. galli stages under field condition on two farms. However, the hens became re-infected within a week post treatment. We concluded that the way anthelmintics are used on farms needs to be refined. Comparison of the TT strategy and single treatment strategy (CT) with untreated control groups (UT) showed that barn contamination with parasite eggs, individual faecal egg counts (FEC) and worm burdens were lower in flocks where the TT strategy was applied. No significant difference was observed between the CT and UT flocks with regard to worm burden and FEC. We concluded that a single treatment late during the production cycle is suboptimal and cannot prevent the build-up of infection and barn contamination. We recommended that the TT strategy should be considered a better alternative to a single treatment late during production. Investigation into mutations of the β-tubulin isotype 1 gene at codon 167, 189 and 200 showed no evidence of AR. Moreover, the results of the faecal egg count reduction test and the larval development test did not point at existence of AR on the investigated farm.

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