SUMMARY: Members of the family Trichomonadidae, mainlyTrichomonas gallinaeandTetratrichomonas gallinarum, represent important parasites in birds with worldwide presence, since being reported in the 19th century. Especially Columbiformes, Falconiformes and Strigiformes can be severely affected by trichomonads, whereas the majority of infections in Galliformes and Anatiformes are subclinical although severe infections are occasionally reported. With the recent appearance of deadly infections in wild Passeriformes the protozoan parasiteT. gallinaeobtained greater attention which will be addressed in this review. Although light microscopy remains the method of choice to confirm the presence of trichomonads molecular studies were introduced in recent years, in order to characterize the parasites and to establish relationships between isolates. Isolation of trichomonads is a prerequisite for detailedin vitroandin vivostudies and different media are reported to obtain suitable material. The limited information about virulence factors will be reviewed in context with the pathogenicity of trichomonads which varies greatly, indicating certain strain heterogeneity of the parasites. Options for treatment characterized by the leading role of imidazoles whose activity is sometimes hampered by resistant parasites remains a challenge for the future. Introducing more standardized genetic studies and investigations concentrating on the host-pathogen interaction should be helpful to elucidate virulence factors which might lead to new concepts of treatment.

Asymptomatic carriage of Campylobacter jejuni is highly prevalent in chicken flocks. Thus, we investigated whether chronic Campylobacter carriage affects chicken intestinal functions despite the absence of clinical symptoms. An experiment was carried out in which commercial chickens were orally infected with C. jejuni (1 × 10⁸ CFU/bird) at 14 days of life. Changes in ion transport and barrier function were assessed by short-circuit current ( I_sc) and transepithelial ion conductance ( G_t) in Ussing chambers. G_t increased in cecum and colon of Campylobacter-infected chicken 7 d post-infection (DPI), whereas G_t initially decreased in the jejunum at 7 DPI and increased thereafter at 14 DPI. The net charge transfer across the epithelium was reduced or tended to be reduced in all segments, as evidenced by a decreased I_sc. Furthermore, the infection induced intestinal histomorphological changes, most prominently including a decrease in villus height, crypt depth and villus surface area in the jejunum at 7 DPI. Furthermore, body mass gain was decreased by Campylobacter carriage. This study demonstrates, for the first time, changes in the intestinal barrier function in Campylobacter-infected chickens and these changes were associated with a decrease in growth performance in otherwise healthy-appearing birds.

Histomonosis is a parasitic disease of poultry with worldwide prevalence. The disease can cause morbidity and mortality in chicken and turkey flocks entailing severe economic losses. In the first half of the last century, there was a high demand to control histomonosis as the turkey industry was severely affected by the disease. Consequently, numerous chemical compounds were tested for their efficacy against Histomonas meleagridis with varying outcomes, that are summarized and specified in this review. At the same time, preliminary attempts to protect birds with cultured histomonads indicated the possibility of vaccination. Several years ago antihistomonal drugs were banned in countries with tight regulations on pharmaceuticals in order to comply with the demand of consumer protection. As a consequence, outbreaks of histomonosis in poultry flocks increased and the disease became endemic again. New approaches to prevent and treat histomonosis are, therefore, needed and recently performed studies focused on various areas to combat the disease, from alternative chemotherapeutic substances to plant-derived compounds until vaccination, altogether reviewed here. Considering existing regulations and the overall outcome of experimental studies, it can be concluded that vaccination is very promising, despite the fact that various challenges need to be addressed until the first ever developed vaccine based upon live flagellates in human or bird medicine can be marketed.

The present report documents an outbreak of adenoviral gizzard erosion in 22 broiler flocks in Germany. The clinical picture was characterized by uneven growth of affected broilers that resulted in considerably lower than average weight at slaughtering. Fowl adenovirus serotype 1 (FAdV-1) was isolated from gizzard lesions and histological examinations demonstrated FAdV-1-positive intranuclear inclusion bodies in gizzard epithelial cells of affected broilers by in-situ hybridization. Birds from all affected flocks originated from one broiler breeder farm. During production of affected birds, broiler breeders were between 27 and 32 weeks old. Enzyme-linked immunosorbent assay and specific virus neutralization assay of sera from parent birds demonstrated an acute FAdV-1 infection within the first 5 weeks of the production cycle. Clinically, broiler breeders exhibited a moderate fall in the hatchability of their chicks, while egg production remained normal. No further clinical signs could be observed. Genetically identical FAdV-1 strains were isolated from gizzards of embryos at the lowest point of hatchability and from affected broiler flocks raised on independent farms. For the first time, direct detection of viable FAdV-1 from gizzards of embryos and progenies of one FAdV-1-seropositive broiler breeder farm in the course of an outbreak of adenoviral gizzard erosion could be demonstrated, highlighting the importance of vertical transmission of this disease. Additionally, growth retardation and subsequent reduced average weight at the time of slaughter of broiler chickens underline the economic impact of adenoviral gizzard erosion for poultry production.

In the present investigation, the pathogenicity and transmission of a mono-eukaryotic culture of Histomonas meleagridis for commercial turkeys and specific pathogen free (SPF) chickens is described for the first time. Two separate trials with the same kind of experimental design were performed, one with commercial turkeys and one with SPF chickens. In each experiment, two different groups were included, which were housed in separate rooms. The first group contained four control birds, whereas the second group consisted of 10 infected and four in-contact birds. The birds were infected via the cloaca at 14 days of age with 380 000 cells of a mono-eukaryotic culture of H. meleagridis consisting of a cloned isolate (Turkey/Austria/2922-66/04). Reisolation of the parasite from turkeys and chickens under experimental conditions was performed for the first time. The infected birds started to excrete the parasite as soon as 2 days post infection. Rapid spread of the parasite to in-contact turkeys and chickens was noticed, based on reisolation of live parasites. Reisolation of the pathogen was impossible from two of the four in-contact SPF chickens at any time, whereas all of the infected turkeys were found positive. Intermittent shedding of the parasite was noticed in infected turkeys and SPF chickens, but the phenomenon was much more severe in the SPF chickens as these birds survived the infection. All of the infected and in-contact turkeys died between days 11 and 14 post infection, whereas no death was recorded in the SPF chickens, which were killed 6 weeks after the infection. Typical lesions were recorded in the caeca and livers of the infected turkeys. In addition, a heavy destruction of the bursa of Fabricius was seen in all of the infected and one of the in-contact turkeys. Altogether, the present investigations are of importance for an understanding of the pathogenicity and transmission of H. meleagridis in poultry. Transmission rapide du parasite protozoaire Histomonas meleagridis chez des dindes et des poulets SPF après une infection par voie cloacale avec une culture mono eucaryote Dans cette étude, la pathogénicité et la transmission d'une culture mono eucryote d' Histomonas meleagridis pour des dindes du commerce et des poulets exempts de microorganismes pathogènes spécifiés (SPF) sont décrites pour la première fois. Deux essais différents avec le même type de protocole expériemental, l'un avec des dindes du commerce et l'autre avec des poulets SPF, ont été réalisés. Chaque essai, comprenait deux groupes différents qui étaient hébergés dans des animaleries séparées. Le premier groupe comportait 4 animaux témoins, alors que le second groupe comportait 10 sujets infectés et 4 sujets contacts. Les animaux ont été infectés par voie cloacale à l'âge de 14 jours avec 380 000 cellules d'une culture mono eucryote d' Histomonas meleagridis qui correspondait à un isolat cloné (Turkey/Austria/2922/04). Le réisolement du parasite à partir des dindes et des poulets dans des conditions expérimentales a été réalisé pour la première fois. Les animaux infectés ont commencé à excréter le parasite dès le 2^ème jour après l'infection. Une rapide diffusion du parasite aux dindes et poulets contacts a été observée, basée sur le réisolement des parasites vivants. L'agent pathogène n'a pas pu être réisolé à partir de 2 des 4 poulets SPF contacts lors d'aucun prélèvement, alors que toutes les dindes infectées ont été positives. Une excrétion intermittente du parasite a été notée chez les dindes et les poulets SPF infectés, mais le phénomène a été beaucoup plus important chez les poulets SPF puisque ces animaux ont survécu à l'infection. Toutes les dindes infectées et contacts sont mortes entre le 11^ème et le 14^ème jour après l'infection, alors qu'aucune mortalité n'a été enregistrée chez les poulets SPF qui ont été sacrifiés 6 semaines après l'infection. Des lésions typiques ont été notées au niveau des cæca et du foie chez les dindes infectées. De plus, une destruction importante de la bourse de Fabricius a été observée chez toutes les dindes infectées et chez une dinde contact. Dans l'ensemble ces recherches sont importantes pour la compréhension de la pathogénicité et de la transmission d' Histomonas meleagridis chez les volailles. Schnelle Übertragung des Protozoenparasiten Histomonas meleagridis in Puten und spezifiziert pathogen freien Hühnern nach kloakaler Infektion mit einer mono-eukaryotischen Kultur Dies ist die Erstbeschreibung einer Untersuchung der Pathogenität und Übertragung einer mono-eukaryotischen Kultur von Histomonas meleagridis für kommerzielle Puten und spezifiziert pathogen freie (SPF) Hühner. Es wurden zwei getrennte Versuche, einer mit kommerziellen Puten und einer mit SPF-Hühnern, mit dem gleichen Versuchsplan durchgeführt. In jedem Versuch gab es zwei Gruppen, die in separaten Räumen untergebracht waren. Die erste Gruppe bestand aus 4 Kontrolltieren, während in der zweiten Gruppe zehn infizierte und vier Kontakttiere waren. Die Tiere wurden am 14. Lebenstag via Kloake mit 380 000 Zellen einer mono-eukaryotischen Histomonas meleagridis-Kultur eines geklonten Isolats (Turkey/Austria/2922/04) infiziert. Die Reisolierung des Parasiten aus Puten und Hühnern unter experimentellen Bedingungen wurde erstmalig durchgeführt. Bereits zwei Tage nach der Infektion begannen die infizierten Tiere den Parasiten auszuscheiden. Aufgrund der Reisolierung lebender Parasiten konnte die schnelle Ausbreitung der Parasiten auf die Kontakttiere nachgewiesen werden. Während bei zwei der vier Kontakt-SPF-Hühner eine Reisolierung des Pathogens nicht gelang, waren alle infizierten Puten positiv. Bei den infizierten Puten und Hühnern wurde eine intermittierende Ausscheidung des Parasiten festgestellt, aber dieses Phänomen war bei den Hühnern, die auch die Infektion überlebten, wesentlich deutlicher ausgeprägt. Alle infizierten und Kontakt-Puten starben zwischen dem 11. und 14. Tag nach der Infektion. Die SPF-Hühner überlebten alle und wurden 6 Wochen nach der Infektion getötet. In den Blinddärmen und Lebern der infizierten Puten wurden typische Läsionen diagnostiziert. Außerdem wurde bei allen infizierten und einem Kontakttier eine schwere Zerstörung der Bursa Fabricii nachgewiesen. Die vorliegenden Untersuchungsergebnisse sind für das Verständnis der Pathogenität und der Übertragung von Histomonas meleagridis beim Geflügel wichtig. Transmisión rápida del parásito protozoario Histomonas meleagridis en pollos libres de patógenos específicos y pavos tras la infección cloacal con cultivo mono-eucariota En el presente estudio se describe por primera vez la patogenicidad y transmisión del cultivo mono-eucariota de Histomonas meleagridis en pavos comerciales y pollos libres de patógenos específicos (SPF). Se llevaron a cabo dos pruebas separadas con el mismo diseño experimental, una con pavos comerciales y la otra con pollos SPF. En cada prueba se incluyeron dos grupos diferentes alojados en corrales separados. El primer grupo contenía 4 aves control mientras que el segundo grupo incluía 10 aves infectadas y 4 aves centinelas. Las aves se infectaron vía cloacal a los 14 días de vida con 380 000 células de un cultivo mono-eucariota de Histomonas meleagridis procedente de la clonación de un aislamiento (Turkey/Austria/2922/04). Por primera vez se llevó a cabo en condiciones experimentales el reaislamiento del parásito de pavos y pollos. Las aves infectadas empezaron a excretar el parásito tan pronto como 2 días post infección. Se observó una diseminación rápida del parásito a los pavos y pollos centinelas, en base al reaislamiento del parásito vivo. No se pudo reaislar el patógeno de dos de los 4 pollos SPF centinelas en ningún momento, mientras que todos los pavos infectados fueron positivos. Se determinó la excreción intermitente del parásito en pavos y pollos SPF infectados, pero el fenómeno fue mucho más intenso en los pollos SPF, dado que estas aves sobrevivieron a la infección. Todos los pavos infectados y centinelas murieron entre los 11 y 14 días post infección, mientras que ningún pollo SPF murió, de modo que se sacrificaron a las 6 semanas post infección. Se observaron lesiones características en los ciegos e hígados de los pavos infectados. Además, se observó una destrucción intensa de la bolsa de Fabricio en todos los pavos infectados y en uno de los centinelas. En conjunto, estos estudios son importantes para entender la patogenicidad y transmisión de Histomonas meleagridis en aves.