Veterinary Autogenous Vaccines for Poultry in Europe-Many Ways to Crack an Egg.

In the past decade, European animal farming has increasingly used autogenous vaccines for the prevention of nonnotifiable diseases. In Europe, these vaccines are exclusively inactivated bacterial and viral vaccines, with a set of specific regulations that differentiate them from conventional vaccines. The highest number of applications most likely occurs in poultry, as these animal species are farmed in the highest numbers compared with other types of food-producing animals. In 2019, autogenous vaccines came within the scope of harmonized European regulation for the first time, although many important aspects are still missing and need to be further developed. Consequently, several important legal provisions remain in national legislations and can vary tremendously between different member states of the European Union. The inclusion of autogenous vaccines in the management of certain diseases of poultry is justified by the nonavailability of licensed vaccines and the evolution and diversity of antigens in the field that are not covered by licensed vaccines. In addition, these vaccines aid in reducing the use of antibiotics. The methods for isolating and typing pathogenic isolates to obtain relevant antigens are pathogen specific and require a careful approach based on clinical evidence. Manufacturing processes are optimized according to regulatory standards, and they represent the most critical factor influencing the quality of autogenous vaccines and their placement on the market. This review presents the important requirements for manufacturing autogenous vaccines for poultry in addition to the relevant regulatory considerations. The results from a survey of several European Union member states regarding specific provisions within their national legislations are also presented.

Vacunas veterinarias autógenas para la avicultura en Europa: "Varias formas de romper un huevo". En la última década, la ganadería europea ha utilizado cada vez más vacunas autógenas para la prevención de enfermedades no declarables. En Europa, estas vacunas son exclusivamente vacunas inactivadas bacterianas y virales, con un conjunto de regulaciones específicas que las diferencian de las vacunas convencionales. El mayor número de aplicaciones probablemente se produce en la avicultura, ya que estas especies animales se crían en mayor número en comparación con otros tipos de animales productores de alimentos. En el año 2019, las vacunas autógenas entraron por primera vez en el ámbito de aplicación de una regulación europea armonizada, aunque todavía faltan muchos aspectos importantes y es necesario desarrollarlos más. En consecuencia, varias disposiciones legales importantes permanecen en las legislaciones nacionales y pueden variar enormemente entre los diferentes estados miembros de la Unión Europea. La inclusión de vacunas autógenas en el manejo de determinadas enfermedades avícolas se justifica por la falta de disponibilidad de vacunas autorizadas y la evolución y diversidad de antígenos en el campo que no están cubiertos por vacunas con licencia. Además, estas vacunas ayudan a reducir el uso de antibióticos. Los métodos para aislar y tipificar aislados patógenos para obtener antígenos relevantes son específicos de cada patógeno y requieren un enfoque cuidadoso basado en evidencia clínica. Los procesos de fabricación se optimizan de acuerdo con las normas reglamentarias y representan el factor más crítico que influye en la calidad de las vacunas autógenas y su comercialización. Esta revisión presenta los requisitos importantes para la fabricación de vacunas autógenas en la avicultura, además de las consideraciones regulatorias relevantes. También se presentan los resultados de una encuesta realizada en varios estados miembros de la Unión Europea sobre disposiciones específicas dentro de sus legislaciones nacionales.

Risks and disease aetiologies of compromised performance in commercial broilers kept at lower stocking density and limited antimicrobial use.

The health status of broilers raised at lower stocking density and limited antimicrobial use (but routine anticoccidials) was assessed in order to identify prevalent causes of disease, mortality and reduced performance. "Dead-on-farm"(DOF) broilers from 145 commercial flocks were investigated at two different time points (TP1:7-14 and TP2:28-35 days of age); per sampling, 6-10 DOF broilers were selected for post-mortem investigation and gross pathomorphological changes were assessed from 2717 birds in total. Post-mortem findings were substantiated by bacteriological, virological and parasitological investigations. Furthermore, production data of all flocks were collected and used to perform comprehensive statistical analysis. Overall, colibacillosis was found most important with a significant negative impact on flock health, productivity and profitability through all ages of broiler production. At TP1, primary reasons for mortality comprised yolk sac infections, generally found together with fibrinous polyserositis due to E. coli. Furthermore, femoral lesions, which correlated with increased flock mortality, were associated with detection of E. coli. At TP2, ascites was detected frequently in DOF broilers, correlating with increased production losses in the fourth and fifth weeks of life. No aetiological link between the presence of ascites and the detection of the investigated pathogens was observed, instead a positive correlation was noticed with altitude above sea level of the farm, and with the sex of the birds. Disease conditions could not be linked with the housing system. Presence of infectious bronchitis virus, avian reovirus and fowl adenovirus did not correlate with macroscopic lesions or a specific disease. RESEARCH HIGHLIGHTS In young broilers lesions of visceral organs due to bacterial infections dominated. Colibacillosis impacts broiler health, productivity and profitability independent of the age of birds. Disorders of the locomotor system were frequently observed throughout production. Older broilers frequently showed pathologic changes due to metabolic disorders. Overall, a shift from infectious towards metabolic disease conditions was noticed.

PCR and serology confirm the infection of turkey hens and their resilience to histomonosis in mixed flocks following high mortalities in toms.

BACKGROUND: Histomonosis, caused by the protozoan parasite Histomonas meleagridis, is a severe disease especially in turkeys where it can cause high mortalities. Recently, outbreaks were described in which turkey hens showed no clinical signs despite high mortalities in toms, from which they were separated only by a wire fence. The present study investigated three similar outbreaks of histomonosis whereby in two of them only a few hens were being affected and none in the third. Hens from all flocks were kept until end of production and slaughtered as scheduled. However, in all three cases, the disease progressed in toms reaching nearly 100% within two weeks. METHODS: Following diagnosis of the disease, tissue samples were obtained from toms and hens at necropsy. Environmental dust, cloacal swabs and blood were taken on three successive farm visits within compartments of hens and toms and tested by real-time PCR or ELISA. The DNA from a total of 18 samples positive for H. meleagridis was further subjected to conventional PCR utilizing the 18S rRNA primers and sequenced for phylogenetic analysis. RESULTS: All tissue samples and some cloacal swabs were tested positive. Dust samples confirmed the presence of H. meleagridis DNA that spread within entire houses up to 6 weeks after the first clinical signs of histomonosis. Sequence analysis of the 18S rRNA locus demonstrated the presence of the same strain in birds of both sexes within each of the turkey houses. Investigation of serum samples two weeks post-initial diagnosis and prior to euthanasia resulted in antibody detection in 73% of toms and 70% of hens. Until the end of the investigation the number of positive hens per farm increased up to 100% with mean OD-values approaching those noticed in toms prior to euthanasia. CONCLUSIONS: For the first time it could be demonstrated that turkey hens kept in the same house as toms became infected during fatal outbreaks in toms. This highlights the value of different diagnostics methods in order to trace the parasite in connection with the host response. The strange phenomenon that only single hens succumb to the diseases despite being infected requires further investigations.

Detection of Histomonas meleagridis DNA in dust samples obtained from apparently healthy meat turkey flocks without effect on performance.

Environmental dust samples obtained from 65 turkey flocks in France, of which six suffered from histomonosis whereas the rest remained apparent healthy until the end of production, were tested for the presence of Histomonas meleagridis DNA by recently developed real-time PCR based on the 18S rRNA locus. In order to determine the genotype of detected histomonads, positive samples were further subjected to conventional 18S PCR and sequencing. Additionally, production data of all tested flocks, such as average daily gain, feed conversion ratio and production index, were statistically evaluated and compared to see the effect of positive dust samples in apparently healthy flocks. Histomonad DNA was detected in the dust obtained from all six clinically affected and, surprisingly, in nine apparent healthy flocks. Sequencing of the 18S rRNA gene resulted in only one DNA sample homologous to H. meleagridis whereas 11 others revealed the presence of several other flagellates. Average daily gain and production index were negatively affected in flocks with clinical histomonosis, resulting in significant difference in comparison with the data obtained from clinically healthy flocks independent of the presence of histomonad DNA in the dust. Overall, there was no significant difference following statistical analysis of production parameters between the two last mentioned groups of tested flocks. Altogether, this is the first investigation demonstrating the presence of H. meleagridis DNA in environmental dust samples obtained from clinically unaffected turkey flocks. However, this finding could not be correlated with impact on production based on analysis and comparison of selected production data. RESEARCH HIGHLIGHTS Environmental dust obtained from clinically healthy turkey flocks, in addition to dust from flocks affected by histomonosis, was found positive for the presence of Histomonas meleagridis DNA. Histomonas-positive dust samples in clinically unaffected flocks did not have a negative effect on production parameters. The results demonstrate a wider spread of H. meleagridis DNA in flocks of commercial meat turkeys than previously thought.

In vitro attenuated Histomonas meleagridis does not revert to virulence, following serial in vivo passages in turkeys or chickens.

The efficacy of vaccinating poultry against histomonosis was demonstrated recently. In the present study, the reversion to virulence and the residual pathogenicity of an in vitro attenuated, clonal strain of Histomonas meleagridis were tested in two consecutive experiments. The European Pharmcopoeia (Ph. Eur.) monograph for testing such features for coccidiosis live vaccines in chickens has served as a guideline. In the first experiment, attenuated histomonads were used in successive infection cycles in five groups of either five chickens or turkeys, respectively. All birds were killed at 14 days post infection (d.p.i.) to record lesion scores (LS) from livers and caeca. In the second experiment, the 5 times in vivo passaged histomonads were used to infect groups of 30 chickens and turkeys each, together with birds infected with virulent H. meleagridis. At three different time points 10 birds/group were killed and tissues of caeca, livers and lungs were used for PCR and immunohistochemistry (IHC) to confirm the presence of parasites. In the first experiment, various lesion scores were recordable in the livers and caeca of turkeys, with the highest LS 4 noticed once in the liver. In comparison, no lesions were seen in organs from chickens. In the second experiment, only mild lesions in the caeca of both turkeys and chickens were found. Liver lesions recorded as score 1 were noticed in just one individual of each species. PCR and IHC revealed that the attenuated and backpassaged histomonads were not present in liver samples but confined to the caeca, different to virulent H. meleagridis. Overall, no clinical signs or death occurred in turkeys or chickens inoculated orally and cloacally with 10(4) backpassaged histomonads in comparison with virulent parasites. Consequently, for the first time, the stable attenuation and safety of histomonads has been demonstrated, thus providing major implications for vaccine development.