The poultry red mite Dermanyssus gallinae (De Geer) is a blood feeding ectoparasite that infests many bird species. Economically it is the most important parasite affecting egg-laying hens. The aim of this study was to identify vaccine candidate proteins from D. gallinae using a number of approaches. An immunisation trial was conducted using four protein fractions derived from D. gallinae. The fractions were injected into hens and immunoglobulin Y was purified from the yolk of eggs laid by the hens. An in vitro feeding assay in which mites were fed these antibodies showed a significant increase (p = 0.013) in mortality of mites fed with antibodies against a PBS-soluble fraction of D. gallinae. The PBS-soluble proteins were then fractionated by anion exchange chromatography into three fractions, which were then used to immunise hens. One fraction produced antibodies that caused the greatest percentage mortality of mites, based on the results from a single feeding assay. To identify further potential vaccine antigens, three expressed sequence tag (EST) databases were produced. A complementary DNA (cDNA) library was prepared from a mixed gender and life stage population and 46 contigs were identified with significant homology to proteins from other organisms. A second database was generated using a suppression subtractive hybridisation approach and 133 “fed mite enriched” contigs identified with significant homology to proteins in either the NCBI non-redundant (nr) protein, KEGG databases or had a domain predicted by InterProScan. The most abundant proteins in this database were vitellogenin and GP80, a precursor molecule of vitellogenin. Roche 454 sequencing technology was used to generate an EST database of 13,363 contigs, of which 26 % had significant homology to a protein in the NCBI nr protein database. The majority of contigs (45 %) were classified as Cellular Processes and Signalling proteins. Illumina Solexa sequencing technology was also used to analyse the expression levels of genes in fed and starved mites. A total of 66 contigs were obtained with a significant and greater than three-fold change in expression level between the two groups. The contig with the largest fold change was homologous to vitellogenin (fold change 110). Paramyosin and tropomyosin have been used successfully to immunise hosts against other parasitic species. Tropomyosin had previously been characterised in D. gallinae. In this study paramyosin was characterised and recombinant versions of both proteins were used in an immunisation trial. Anti-tropomyosin (p < 0.001) and anti-paramyosin (p = 0.004) antibodies fed to mites in the in vitro feeding assay caused a significant increase in the mortality of the mites when compared to controls. An in vivo challenge was performed injecting three groups of hens with the PBS-soluble native protein fraction, a recombinant protein cocktail, consisting of paramyosin, tropomyosin, cathepsin L, cathepsin D and histamine release factor, and an adjuvant only control, which were subjected to a challenge of D. gallinae. Each group consisted of three replicates based on weight. Western blot analysis of hen serum showed a significant increase (p < 0.05) in the titre of antibody from the hens immunised with the recombinant cocktail compared with controls. One of the replicates immunised with the PBS-soluble protein fraction showed a strong response but this was lacking in the other two replicates and no significant difference in IgY titre was found. No significant differences were found between the number of mites collected from the test or control groups following a large mite challenge. In conclusion the PBS-soluble protein fraction, paramyosin and tropomyosin have been shown to have potential as vaccine candidates based on in vitro studies. The bioinformatic analysis of D. gallinae has provided a large EST database and a list of 66 proteins that had a significant difference in expression levels in fed and starved mites, which can be further mined for potential vaccine candidates.

Trichomonas gallinae é um protozoário flagelado que parasita o trato digestivo superior de várias aves, incluindo pombos domésticos, frangos e perus. O estudo dos mecanismos de patogenicidade deste parasito é de fundamental importância, uma vez que a infecção causada pelo mesmo tem envolvido grandes perdas econômicas. Sabe-se que além da função energética, o ATP desempenha inúmeras funções fisiológicas, como sinalização extracelular e mecanismos citolíticos. As concentrações dos nucleotídeos, tais como ATP e ADP, no meio extracelular são controladas por um grupo de enzimas denominadas ectonuncleotidases. Fazem parte deste grupo as NTPDases (nucleosídeo trifosfato difosfoidrolases) e a ecto-5´- nucleotidase, as quais participam do controle dos níveis extracelulares dos nucleotídeos e nucleosídeos. A presença dessas atividades enzimáticas pode estar associada com a virulência e evasão dos parasitos, servindo como um mecanismo de escape dos efeitos citolíticos do ATP. Portanto, este estudo teve como objetivo caracterizar as atividades da NTPDase e 5´-nucleotidase, envolvidas na degradação dos nucleotídeos extracelulares em T. gallinae. A hidrólise de ATP, ADP e AMP foi ativada na presença de cátions divalentes e a adição de quelantes de cátions no meio de incubação reduziu significativamente a atividade específica da NTPDase e 5´-nucleotidase. As enzimas apresentaram ampla especificidade de substrato, observada através da hidrólise de outros nucleotídeos trifosfatados, difosfatados e monofosfatados, quando adicionados ao meio como substrato. O KM para o ATP foi de 65,62 ± 15,55 μM e para o ADP foi de 122,66 ± 3,51 μM. A Vmax para o ATP e o ADP foi de 0,20 ± 0,03 e 0,70 ± 0,09 nmolPi/min/106 trofozoítos, respectivamente. Para o AMP, o KM foi 466 ± 57 μM, com uma Vmax de 3,70 ± 0,59 nmolPi/min/106 trofozoítos. A influência de outras enzimas que hidrolisam nucleotídeos extracelulares foi descartada através do uso de inibidores específicos. A hidrólise do ATP, ADP e AMP indicou a presença de uma cadeia enzimática na superfície do parasito, composta por uma NTPDase e uma ecto-5’-nucleotidase. A presença de atividades enzimáticas capazes de hidrolisar nucleotídeos extracelulares pode representar um mecanismo de sobrevivência dos parasitos nos seus ambientes naturais. A compreensão dos processos bioquímicos extracelulares destes parasitos pode ampliar o conhecimento a respeito dos mecanismos envolvidos no parasitismo. / Trichomonas gallinae is a flagellated protozoan which parasitizes a variety of birds all over the world, including domestic pigeons, chickens and turkeys. The study of patogenicity mechanisms is relevant, since the infection caused by this parasite involves significant economic loss. Besides the energetic function, extracellular ATP plays several physiological functions, such as extracellular signaling and cytolysis. Extracellular nucleotide levels are controlled by group of enzymes named ectonucleotidases. This group of enzymes includes the NTPDases (nucleoside triphosphate diphosphohydrolases) and an ecto-5´-nucleotidase, which participates in the control of extracellular nucleotide and nucleoside levels. The presence of these enzyme activities could be associated with the virulence and evasion of the parasites, escaping from the cytolytic effects of ATP. Therefore, the aim of this study was to characterize the NTPDase and 5´-nucleotidase activities, involved in extracellular nucleotide degradation in T. gallinae. ATP, ADP and AMP hydrolysis were activated in the presence of divalent cations and the addition of cation chelating agents in the incubation medium significantly decreased the specific activity of NTPDase and 5´-nucleotidase. The enzymes presented broad substrate specificity because others triphosphate, diphosphate and monophosphate nucleotides were also hydrolysed when they were added to the mixture as substrates. The KM value for ATP was 65.62 ± 15.55 μM and for ADP was 122.66 ± 3.51 μM. The Vmax values for ATP and ADP were 0.20 ± 0.03 and 0.70 ± 0.09 nmolPi/min/106 trichomonads, respectively. For AMP, KM was 466 ± 57 μM, with the Vmax value of 3.70 ± 0.59 nmolPi/min/106 trichomonads. The influence of other enzymes able to hydrolyze extracellular nucleotides was tested through the use of specific inhibitors. ATP, ADP and AMP hydrolysis indicated the presence of an enzyme chain in the surface of the parasite, composed by an NTPDase and an ecto-5´-nucleotidase. The presence of enzyme activities able to hydrolyze extracellular nucleotides can represent a survival mechanism of the parasites in their natural environments. The study of extracellular biochemical processes of these parasites can improve the knowledge related to the mechanisms involved in the parasitism.

Trichomonas gallinae é um protozoário flagelado que parasita o trato digestivo superior de várias aves, incluindo pombos domésticos, frangos e perus. O estudo dos mecanismos de patogenicidade deste parasito é de fundamental importância, uma vez que a infecção causada pelo mesmo tem envolvido grandes perdas econômicas. Sabe-se que além da função energética, o ATP desempenha inúmeras funções fisiológicas, como sinalização extracelular e mecanismos citolíticos. As concentrações dos nucleotídeos, tais como ATP e ADP, no meio extracelular são controladas por um grupo de enzimas denominadas ectonuncleotidases. Fazem parte deste grupo as NTPDases (nucleosídeo trifosfato difosfoidrolases) e a ecto-5´- nucleotidase, as quais participam do controle dos níveis extracelulares dos nucleotídeos e nucleosídeos. A presença dessas atividades enzimáticas pode estar associada com a virulência e evasão dos parasitos, servindo como um mecanismo de escape dos efeitos citolíticos do ATP. Portanto, este estudo teve como objetivo caracterizar as atividades da NTPDase e 5´-nucleotidase, envolvidas na degradação dos nucleotídeos extracelulares em T. gallinae. A hidrólise de ATP, ADP e AMP foi ativada na presença de cátions divalentes e a adição de quelantes de cátions no meio de incubação reduziu significativamente a atividade específica da NTPDase e 5´-nucleotidase. As enzimas apresentaram ampla especificidade de substrato, observada através da hidrólise de outros nucleotídeos trifosfatados, difosfatados e monofosfatados, quando adicionados ao meio como substrato. O KM para o ATP foi de 65,62 ± 15,55 μM e para o ADP foi de 122,66 ± 3,51 μM. A Vmax para o ATP e o ADP foi de 0,20 ± 0,03 e 0,70 ± 0,09 nmolPi/min/106 trofozoítos, respectivamente. Para o AMP, o KM foi 466 ± 57 μM, com uma Vmax de 3,70 ± 0,59 nmolPi/min/106 trofozoítos. A influência de outras enzimas que hidrolisam nucleotídeos extracelulares foi descartada através do uso de inibidores específicos. A hidrólise do ATP, ADP e AMP indicou a presença de uma cadeia enzimática na superfície do parasito, composta por uma NTPDase e uma ecto-5’-nucleotidase. A presença de atividades enzimáticas capazes de hidrolisar nucleotídeos extracelulares pode representar um mecanismo de sobrevivência dos parasitos nos seus ambientes naturais. A compreensão dos processos bioquímicos extracelulares destes parasitos pode ampliar o conhecimento a respeito dos mecanismos envolvidos no parasitismo. / Trichomonas gallinae is a flagellated protozoan which parasitizes a variety of birds all over the world, including domestic pigeons, chickens and turkeys. The study of patogenicity mechanisms is relevant, since the infection caused by this parasite involves significant economic loss. Besides the energetic function, extracellular ATP plays several physiological functions, such as extracellular signaling and cytolysis. Extracellular nucleotide levels are controlled by group of enzymes named ectonucleotidases. This group of enzymes includes the NTPDases (nucleoside triphosphate diphosphohydrolases) and an ecto-5´-nucleotidase, which participates in the control of extracellular nucleotide and nucleoside levels. The presence of these enzyme activities could be associated with the virulence and evasion of the parasites, escaping from the cytolytic effects of ATP. Therefore, the aim of this study was to characterize the NTPDase and 5´-nucleotidase activities, involved in extracellular nucleotide degradation in T. gallinae. ATP, ADP and AMP hydrolysis were activated in the presence of divalent cations and the addition of cation chelating agents in the incubation medium significantly decreased the specific activity of NTPDase and 5´-nucleotidase. The enzymes presented broad substrate specificity because others triphosphate, diphosphate and monophosphate nucleotides were also hydrolysed when they were added to the mixture as substrates. The KM value for ATP was 65.62 ± 15.55 μM and for ADP was 122.66 ± 3.51 μM. The Vmax values for ATP and ADP were 0.20 ± 0.03 and 0.70 ± 0.09 nmolPi/min/106 trichomonads, respectively. For AMP, KM was 466 ± 57 μM, with the Vmax value of 3.70 ± 0.59 nmolPi/min/106 trichomonads. The influence of other enzymes able to hydrolyze extracellular nucleotides was tested through the use of specific inhibitors. ATP, ADP and AMP hydrolysis indicated the presence of an enzyme chain in the surface of the parasite, composed by an NTPDase and an ecto-5´-nucleotidase. The presence of enzyme activities able to hydrolyze extracellular nucleotides can represent a survival mechanism of the parasites in their natural environments. The study of extracellular biochemical processes of these parasites can improve the knowledge related to the mechanisms involved in the parasitism.

Trichomonas gallinae é um protozoário flagelado que parasita o trato digestivo superior de várias aves, incluindo pombos domésticos, frangos e perus. O estudo dos mecanismos de patogenicidade deste parasito é de fundamental importância, uma vez que a infecção causada pelo mesmo tem envolvido grandes perdas econômicas. Sabe-se que além da função energética, o ATP desempenha inúmeras funções fisiológicas, como sinalização extracelular e mecanismos citolíticos. As concentrações dos nucleotídeos, tais como ATP e ADP, no meio extracelular são controladas por um grupo de enzimas denominadas ectonuncleotidases. Fazem parte deste grupo as NTPDases (nucleosídeo trifosfato difosfoidrolases) e a ecto-5´- nucleotidase, as quais participam do controle dos níveis extracelulares dos nucleotídeos e nucleosídeos. A presença dessas atividades enzimáticas pode estar associada com a virulência e evasão dos parasitos, servindo como um mecanismo de escape dos efeitos citolíticos do ATP. Portanto, este estudo teve como objetivo caracterizar as atividades da NTPDase e 5´-nucleotidase, envolvidas na degradação dos nucleotídeos extracelulares em T. gallinae. A hidrólise de ATP, ADP e AMP foi ativada na presença de cátions divalentes e a adição de quelantes de cátions no meio de incubação reduziu significativamente a atividade específica da NTPDase e 5´-nucleotidase. As enzimas apresentaram ampla especificidade de substrato, observada através da hidrólise de outros nucleotídeos trifosfatados, difosfatados e monofosfatados, quando adicionados ao meio como substrato. O KM para o ATP foi de 65,62 ± 15,55 μM e para o ADP foi de 122,66 ± 3,51 μM. A Vmax para o ATP e o ADP foi de 0,20 ± 0,03 e 0,70 ± 0,09 nmolPi/min/106 trofozoítos, respectivamente. Para o AMP, o KM foi 466 ± 57 μM, com uma Vmax de 3,70 ± 0,59 nmolPi/min/106 trofozoítos. A influência de outras enzimas que hidrolisam nucleotídeos extracelulares foi descartada através do uso de inibidores específicos. A hidrólise do ATP, ADP e AMP indicou a presença de uma cadeia enzimática na superfície do parasito, composta por uma NTPDase e uma ecto-5’-nucleotidase. A presença de atividades enzimáticas capazes de hidrolisar nucleotídeos extracelulares pode representar um mecanismo de sobrevivência dos parasitos nos seus ambientes naturais. A compreensão dos processos bioquímicos extracelulares destes parasitos pode ampliar o conhecimento a respeito dos mecanismos envolvidos no parasitismo. / Trichomonas gallinae is a flagellated protozoan which parasitizes a variety of birds all over the world, including domestic pigeons, chickens and turkeys. The study of patogenicity mechanisms is relevant, since the infection caused by this parasite involves significant economic loss. Besides the energetic function, extracellular ATP plays several physiological functions, such as extracellular signaling and cytolysis. Extracellular nucleotide levels are controlled by group of enzymes named ectonucleotidases. This group of enzymes includes the NTPDases (nucleoside triphosphate diphosphohydrolases) and an ecto-5´-nucleotidase, which participates in the control of extracellular nucleotide and nucleoside levels. The presence of these enzyme activities could be associated with the virulence and evasion of the parasites, escaping from the cytolytic effects of ATP. Therefore, the aim of this study was to characterize the NTPDase and 5´-nucleotidase activities, involved in extracellular nucleotide degradation in T. gallinae. ATP, ADP and AMP hydrolysis were activated in the presence of divalent cations and the addition of cation chelating agents in the incubation medium significantly decreased the specific activity of NTPDase and 5´-nucleotidase. The enzymes presented broad substrate specificity because others triphosphate, diphosphate and monophosphate nucleotides were also hydrolysed when they were added to the mixture as substrates. The KM value for ATP was 65.62 ± 15.55 μM and for ADP was 122.66 ± 3.51 μM. The Vmax values for ATP and ADP were 0.20 ± 0.03 and 0.70 ± 0.09 nmolPi/min/106 trichomonads, respectively. For AMP, KM was 466 ± 57 μM, with the Vmax value of 3.70 ± 0.59 nmolPi/min/106 trichomonads. The influence of other enzymes able to hydrolyze extracellular nucleotides was tested through the use of specific inhibitors. ATP, ADP and AMP hydrolysis indicated the presence of an enzyme chain in the surface of the parasite, composed by an NTPDase and an ecto-5´-nucleotidase. The presence of enzyme activities able to hydrolyze extracellular nucleotides can represent a survival mechanism of the parasites in their natural environments. The study of extracellular biochemical processes of these parasites can improve the knowledge related to the mechanisms involved in the parasitism.

In a practical part of my thesis I monitored mortality of poultry red mite (Dermanyssus gallinae), caused by selected essential oils. There were used six essential oils: clove bud, lavender, cinnamon, rosemary, skin of Brazilian oranges, peppermint. The acaricidal activity of six plant essential oils against poultry house-collected red mites was examined using direct contact method by glass vial bioassay, at six different concentrations: 0.5; 0.25; 0.12; 0.06; 0.03; 0.015 microlitre/cm2. Always eleven glass vials per each concentration and oil and controls (without essential oils) were used. Oils were dissolved in metanol or distilled water or Tween 85 with water. Twenty movable poultry red mites all their stages of development were placed on the filter paper impregnated by essential oil at the bottom of the glass vials. The mortality of the poultry red mites in the glass vials was measured after 24 h. All used essential oils caused mortality of poultry red mite. The average mortality in the controls were 2 %. The highest mortality was observed with clove buds essential oil and cinnamon essential oil at concentrations of 0.5 and 0.25 microlitre/cm2.

Le pou rouge Dermanyssus gallinae est un acarien d’importance sanitaire et économique majeure en élevage de poules pondeuses partout dans le monde mais paradoxalement le fonctionnement de son écosystème a été relativement peu étudié. Hématophage strict, D. gallinae n’est pas un parasite typique, il entretient une relation lâche mais obligatoire avec son hôte. Confiné dans l’environnement proche de son hôte (nids, fientes sèches, litière, fumier, . . .) D. gallinae est fortement soumis aux interactions avec les autres organismes qui peuplent ces microhabitats. Ce travail a pour objectif d’apporter des éléments pertinents de caractérisation de cet écosystème singulier mal connu pour, au delà de la production de connaissance, alimenter une réflexion sur le développement de stratégies de gestion intégrée innovantes afin de s’affranchir de la stricte lutte chimique qui reste à l’heure actuelle le moyen de luttele plus largement utilisé. L’étude des interactions chimiques entre le pou rouge et son hôte a permis de mieux identifier les sources de stimulus et mieux comprendre les réponses de D. gallinae aux odeurs de poule ainsi que de déterminer dans quelle mesure il était possible d’interférer entre l’hôte et son microprédateur au moment de l’étape de repérage. La caractérisation de la structure des communautés d’arthropodes partageant les mêmes microhabitats que le pou rouge a montré que D. gallinae côtoyait plusieurs espèces d’acariens et insectes prédateurs d’arthropodes qui sont potentiellement ses ennemis naturels. Il a également été mis en évidence que le bâtiment d’élevage constituait une unité propre en termes de composition et de structure des communautés d’arthropodes. Les différences significatives de fréquence et d’occurrencedes différentes espèces prédatrices entre bâtiments, ainsi que leur capacitéde propagation depuis l’environnement extérieur constituent des indicateurs prometteurs pour le développement de la lutte biologique par conservation contre le pou rouge. Des questions transversales quant aux effets croisés, synergiques ou antagonistes, entre la manipulation des odeurs de l’hôte et la mise à contribution des processus écologiques impliquant les arthropodes non hématophages sont posées en vue d’une démarche intégrant ces outils ainsi que les autres moyens de contrôle disponibles dans un contexte de protection biologique intégrée du pou rouge. / The Poultry Red Mite (PRM) Dermanyssus gallinae is a mite of major sanitary andeconomic importance for the egg production industry worldwide but paradoxicallythe functioning of its ecosystem has been little studied. The objective of this work was to provide relevant elements for the characterization of this singular ecosystem that is poorly known, in order to, beyond the production of knowledge, contribute to the development of innovative strategies of integrated management. This is expected to allow going further than the strict chemical control which is still to date the most widely used means of control. The study of the chemical interactions between the PRM and its host allowed to better identify sources of stimulus and to better understand D. gallinae’s responses to chicken odors as well as to determine to what extent it was possible to interfere between the host and its micropredator during the first phase of the host location. The characterization of the structure of arthropod communities sharing the same microhabitats as does PRM showed that D. gallinae was associated with several species of mites and predatory insects of arthropods which could potentially be its natural enemies. It was also demonstrated that the livestock building was a specific unit in terms of the composition and structure ofthe arthropod communities. Significant differences in the frequency and occurrence of predatory species between buildings and their propagation capacity from the external environment are promising indicators for the development of conservation biological control (CBC) against PRM. A reflection on the possible synergistic and antagonistic cross-effects between the manipulation of host odors and the stimulation of ecological processes involving non-haematophagous arthropods is carried out. This is expected to participate in the development of an approach integrating these tools as well as other available means of control in a context of integrated biological protection of PRM.

Einleitung Dermanyssus gallinae ist ein weit verbreiteter Ektoparasit bei Hühnern in Europa. Vor allem in den Sommermonaten entwickeln sich in Hühnerställen sehr große Milbenpopulationen. Die Milbenstiche und der damit einhergehende Blutverlust gehen zulasten des Tierwohls und verursachen hohe wirtschaftliche Einbußen. Die Milben befinden sich nur nachts für den Saugakt auf den Tieren und verstecken sich tagsüber in trockener Einstreu oder in dunklen Ritzen und Spalten. Dies macht die Bekämpfung schwierig und aufwendig. Seit September 2017 ist ein Arzneimittel mit dem Wirkstoff Fluralaner auf dem deutschen Markt verfügbar. Dieses soll die Bekämpfung der Roten Vogelmilbe einfacher machen. Ziel der Untersuchungen Ziel dieser Dissertation ist die Bewertung der Milbenreduktion bei Behandlung mit Fluralaner in der Dosierung 0,5 mg/kg Körpergewicht bei zweimaliger Applikation im Abstand von sieben Tagen in natürlich infizierten Geflügelställen. Verglichen wurde jeweils ein behandelter Versuchsstall mit einem unbehandelten Kontrollstall unter Beachtung der Good Clinical Practice (GCP). Tiere, Material und Methoden In der vorliegenden Arbeit wurden die Ergebnisse von zwei Junghennenbetrieben, drei Legehennenbetrieben und einem Elterntierbetrieb betrachtet. Auf jedem Betrieb waren zwei möglichst ähnliche Ställe mit vergleichbaren Tieren vorhanden. Die Ställe durften vor der Studie länger als drei Monate nicht mit Antiparasitika oder Silikatstaub behandelt worden sein. Die Höhe des Milbenbefalls in den Ställen wurde mit Fallen der Firma AviVet B.V. (Niederlande) ermittelt. Diese wurden in regelmäßigen Abständen vor und nach der Behandlung an gleichmäßig im Stall verteilten, festen Plätzen für 24 Stunden im Stall ausgebracht. Anschließend wurden sie tiefgefroren und bei Avivet B.V. in Lunteren, Niederlande ausgezählt. Die Hühner im Behandlungsstall wurden zwei Mal im Abstand von sieben Tagen mit einer Fluralaner-Lösung (10 mg/ml) behandelt. Die Dosierung betrug 0,5 mg/kg Körpergewicht. Die Studie galt nach einer Versuchsdauer von sechs Monaten nach der ersten Applikation, nach Beendigung eines Produktionszyklus, nach einem starken Absinken der Milbenreduktion oder wenn der Kontrollstall aufgrund des Tierwohls gegen D. gallinae behandelt werden musste, als beendet. Außerdem wurden Mortalität, klinische Auffälligkeiten und bei Legehennen die Legeleistung beobachtet. Die Milbenreduktion der Fluralaner-Lösung wurde mit der Henderson-Tilton Formel berechnet. Tests auf signifikante Unterschiede zwischen der behandelten und unbehandelten Gruppe wurden mit dem U-Test nach Mann-Whitney durchgeführt. Ergebnisse Durch die Behandlung mit Fluralaner konnte bei allen Betrieben eine signifikante (P < 0,05) Milbenreduktion erreicht werden. Bei drei Betrieben wurde eine Milbenreduktion von über 99 % erreicht, in den anderen drei Betrieben lag die Milbenreduktion zwischenzeitlich bei 100 %. Die Dauer der Milbenreduktion unterschied sich jedoch von Betrieb zu Betrieb zum Teil stark. In den Aufzuchtbetrieben wurde am Ende des Produktionszyklus (42 Tage nach erster Fluralaner Applikation) noch eine Wirksamkeit von 96 % beziehungsweise 99,6 % und damit ein signifikanter Unterschied (P < 0,05) festgestellt. In zwei Legehennenbetrieben sank die Milbenreduktion 70 Tage nach der ersten Fluralaner Applikation unter 90 % (P > 0,05). In einem Legehennenstall lag die Wirksamkeit 119 Tage nach der ersten Fluralaner Applikation (Produktionsende) noch bei 98,95 % (P < 0,05). Bei den Elterntieren sank die Milbenreduktion 126 Tage nach der ersten Fluralaner Applikation unter 90 % (P > 0,05). Bei der Mortalität konnten keine signifikanten (P > 0,05) Unterschiede zwischen Versuchs- und Behandlungsstall festgestellt werden. Auch klinisch gab es keine Auffälligkeiten. Bei zwei von drei Betrieben war die Legeleistung im Behandlungsstall gegenüber dem Kontrollstall erhöht. In einem dieser Betriebe könnte diese Differenz aber durch ein unterschiedliches Tieralter verursacht worden sein. Schlussfolgerungen Auf allen untersuchten Betrieben konnte eine Milbenreduktion von über 90 % erreicht werden. Eine zweimalige Applikation im Abstand von sieben Tagen mit Fluralaner in der Dosierung 0,5 mg/kg Körpergewicht ist als wirksam gegen D. gallinae einzustufen. Aufgrund der einfachen Applikation über das Trinkwasser bietet die Behandlung mit Fluralaner viele Vorteile gegenüber im Stall auszubringenden Akariziden und Silikatstäuben.