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Femoral head separation (FHS) is a degenerative skeletal problem in fast-growing poultry wherein the growth plate of the proximal femur separates from its articular cartilage. At its early phase, FHS may remain asymptomatic but lead to epiphyseal breakage, infection, and femoral head necrosis (FHN). Healthy femoral head is viewed as a positive trait for genetic selection. However, the etiology of FHS is poorly understood for use in noninvasive diagnosis and genetic selection. Focal cell death and atrophic changes are likely associated with separation of tissues and necrotic changes. Fibrotic thickening of the articular surface can also impair free movement of the proximal epiphysis in the acetabulum, leading to FHS, under strain. The major limitation to understanding the pathophysiology of FHN is the lack of suitable experimental models and biomarkers to diagnose the problem. In this review, we discuss the possible etiologic factors, anatomic features of the chicken femoral head, biomarkers, and molecular mechanisms relevant to FHN.

The regulatory response to an outbreak of highly pathogenic avian influenza (HPAI) in the United States may involve quarantine and stop movement orders that have the potential to disrupt continuity of operations in the U.S. turkey industry—particularly in the event that an uninfected breeder flock is located within an HPAI Control Area. A group of government-academic-industry leaders developed an approach to minimize the unintended consequences associated with outbreak response, which incorporates HPAI control measures to be implemented prior to moving hatching eggs off of the farm. Quantitative simulation models were used to evaluate the movement of potentially contaminated hatching eggs from a breeder henhouse located in an HPAI Control Area, given that active surveillance testing, elevated biosecurity, and a 2-day on-farm holding period were employed. The risk analysis included scenarios of HPAI viruses differing in characteristics as well as scenarios in which infection resulted from artificial insemination. The mean model-predicted number of internally contaminated hatching eggs released per movement from an HPAI-infected turkey breeder henhouse ranged from 0 to 0.008 under the four scenarios evaluated. The results indicate a 95% chance of no internally contaminated eggs being present per movement from an infected house before detection. Sensitivity analysis indicates that these results are robust to variation in key transmission model parameters within the range of their estimates from available literature. Infectious birds at the time of egg collection are a potential pathway of external contamination for eggs stored and then moved off of the farm; the predicted number of such infectious birds was estimated to be low. To date, there has been no evidence of vertical transmission of HPAI virus or low pathogenic avian influenza virus to day-old poults from hatching eggs originating from infected breeders. The application of risk analysis methods was beneficial for evaluating outbreak measures developed through emergency response planning initiatives that consider the managed movement of hatching eggs from monitored premises in an HPAI Control Area.

In this study, we examined the association among clinical signs, ciliostasis, virus detection, and histopathology for evaluating protection of vaccinated chickens against homologous and heterologous infectious bronchitis virus (IBV) challenge. At 5 days following challenge with IBV, we found a good correlation among clinical signs, ciliostasis in the trachea, challenge virus detection, and microscopic lesions in the trachea, with all four criteria being negative in fully protected birds and positive in fully susceptible birds. In partially protected birds we observed clinical signs and detected challenge virus; however, the ciliated epithelium was intact. In a second experiment, we challenged fully protected, partially protected, and fully susceptible birds with IBV, and then at 5 days postchallenge we gave the birds an opportunistic bacterium intranasally. Twenty Bordetella avium colonies were recovered from one of five fully protected birds, and only five colonies were isolated from two of five partially protected birds without ciliostasis, whereas in birds with ciliostasis, numerous colonies were isolated. Obviously, decreasing IBV infection and replication in the upper respiratory tract will decrease transmission and mutations, leading to variant viruses, and herein we demonstrate that protection of the cilia will decrease secondary bacterial infections, which have been shown to lead to condemnations and increased mortality. Thus, it appears that examining both criteria would be important when evaluating IBV vaccine efficacy.

Administration of Marek’s disease (MD) vaccines in ovo has become a common practice for the poultry industry. Efficacy of MD vaccines is very high, even though they are administered to chicken embryos that are immunologically immature. We have recently demonstrated that in ovo vaccination with turkey herpesvirus (HVT) results in increased activation of T cells at hatch. Our previous results suggested that in ovo vaccination with HVT might have a positive impact not only on MD protection but also on the overall maturity of the developing immune system of the chicken (Gallus gallus domesticus). The objective of this study was to evaluate the effect of administration of HVT at 18 days of embryonation (ED) on the maturation of the embryo immune system. Four experiments were conducted in Specific-Pathogen-Free Avian Supplies (SPAFAS) chickens to evaluate the effect of administration of HVT at 18 ED on the splenic cell phenotypes at day of age (experiment 1) and on the ability of 1-day-old chickens to respond to various antigens compared with older birds (experiments 2 and 3). In addition, a fourth experiment was conducted to elucidate whether administration of other serotype’s MD vaccines (CVI988 and SB-1) at 18 ED had the same effect as HVT on the spleen cell phenotypes at day of age. Our results demonstrated that 1-day-old chickens that had received HVT in ovo (1-day HVT) had higher percentages of CD45 , MHC-I , CD45 MHC-I , CD3 , MHC-II , CD3 MHC-II , CD4 , CD8 , and CD4 CD8 cells in the spleen than 1-day-old sham-inoculated chickens (1-day sham). Moreover, spleens of 1-day HVT chickens had greater percentages of CD45 MHC-I cells and equal or greater numbers of CD4 CD8− and CD4−CD8 cells than older unvaccinated chickens. In addition, administration of HVT at 18 ED rendered chicks at hatch more responsive to unrelated antigens such as concavalin A, phytohemagglutinin-L, and keyhole limpet hemocyanin. Administration of MD vaccines of other serotypes had an effect, although less remarkable than HVT, on the spleen cell phenotypes at hatch. Vaccines of all three serotypes resulted in an increased percentage of MHC-I , CD45−MHC-I , CD4−CD8 , and CD8 cells, but only HVT resulted in a higher percentage of CD45 , CD45 MHC-I , CD3 MHC-II , and CD4 CD8− cells. Results of this study show that it is possible to hasten maturation of the chicken embryo immune system by administering HVT in ovo and open new avenues to optimize the procedure to improve and strengthen the immunocompetency of commercial chickens at hatch.

This report describes an outbreak of transmissible viral proventriculitis (TVP) associated with runting stunting syndrome (RSS) in 25- and 28-day-old broiler chickens, in which chicken proventricular necrosis virus (CNPV) was detected. Clinical signs included poor uniformity, very small birds for their age, increased mortality, and culling of smaller birds. Almost all birds necropsied exhibited moderate to severely enlarged proventriculi with diffusely pale serosa and thickened walls. Microscopically the proventriculi had lesions of degeneration and necrosis of the epithelium of the proventricular glands, accompanied by lymphocytic inflammation and glandular hyperplasia, with occasional formation of lymphoid nodules within the glandular parenchyma. Immunohistochemistry staining for CPNV was positive. Positive staining was generally found in the cytoplasm of glandular epithelial cells in the form of finely granular brown pigment. CPNV RNA was detected in the proventriculi by reverse transcriptase–PCR (RT-PCR). Other findings included mild enteritis in a few birds and small bursa of Fabricius. Direct electron microscopy performed on the intestinal samples was negative for viral particles. RT-PCR analysis of bursae was positive for infectious bursal disease virus (IBDV). In conclusion, this report associates TVP with RSS by describing an outbreak in which TVP attributable to CPNV was the most commonly found lesion in chickens with a clinical history compatible with RSS. Therefore, TVP should be considered as a possible differential diagnosis in cases compatible with RSS.

Between 2012 and 2014, 141 chickens from 10 organic layer flocks with a history of severe drop in egg production (up to 40%) and slight increased mortality (up to 1% per week) were submitted to the Avian Health and Food Safety Laboratory (Puyallup, WA). At necropsy, the most common finding was pinpoint white foci on the liver and regressed ova without any other remarkable lesions. Histologically, there was multifocal mild-to-severe acute necrotizing hepatitis present. No significant bacteria were recovered from liver samples, and tests for mycotoxins were negative. Twenty-six serum samples from four affected flocks tested were positive for avian hepatitis E virus (HEV) immunoglobulin Y antibodies. Avian HEV RNA was detected in 10 livers of chickens from two different affected flocks. The avian HEV was characterized by sequencing and determined to belong to genotype 2. The diagnosis of a clinical manifest HEV was based solely on the demonstration of specific viral RNA and the absence of other causative agents in samples from flocks, as the clinical sings and pathologic lesions were atypical.

Infectious laryngotracheitis (ILT) is a highly contagious disease of chickens and is responsible for significant economic losses in the poultry industry worldwide; it is caused by Gallid herpesvirus-1 (GaHV-1), commonly known as infectious laryngotracheitis virus (ILTV). Experimental evaluation of ILTV strains is fundamental to identify changes in virulence that can contribute to the severity and spread of outbreaks and consequently influence the efficacy of vaccination. Several criteria had been utilized to determine the degree of virulence associated with ILTV strains. The objectives of this study were to compare the levels of virulence of the standard United States Department of Agriculture (USDA) challenge strain with a contemporary outbreak-related strain (63140) and to evaluate the efficacy of individual criteria to identify changes in virulence. Broilers were inoculated with increasing infectious doses of each strain. The criteria utilized to evaluate virulence were clinical signs of the disease, mortality, microscopic tracheal lesions, trachea genome viral loads, and antibody titers. Clinical signs scores were a useful parameter to define the peak of clinical disease but did not reveal differences in virulence between strains. Similarly, trachea microscopic lesion scores or levels of serum antibody titers were parameters that did not reveal obvious differences in virulence between strains. However, mortalities and increased viral genome loads in trachea of chickens inoculated with lower (log ₁₀ 1 to 2) infectious doses clearly differentiated 63140 as a more-virulent ILTV strain. This study provides the framework to compare the virulence level of emerging ILTV isolates to the now-characterized USDA and 63140 strains.

Marek’s disease (MD) strain CVI988 is the most-protective commercially available vaccine against very virulent plus (vv ) Marek’s disease virus (MDV). However, its use in meat-type chickens has been controversial. While several countries have been using CVI988 for more than 40 yr, others do not authorize its use or it is restricted mainly to layers. The use of CVI988 in meat-type chickens will be necessary in the future in areas where other vaccine protocols fail. The objective of this study was to evaluate factors (vaccine dose, vaccine origin, chicken genetics, age and route of vaccination, and combination with other MD vaccines) influencing the efficacy of CVI988 against MD in meat-type chickens. Three animal experiments were conducted in which various vaccine protocols using CVI988 were tested for their protection against challenge with vv strain 648A by contact at day of age. Experiments 1 and 2 were to compare the efficacy of CVI988 vaccines from three different origins (CVI988-A, CVI988-B, and CVI988-C) and evaluate the effect of vaccine dose and chicken genetics. Experiment 3 was to evaluate the effect of adding CVI988 vaccine to various vaccine protocols using other MD vaccines of serotypes 2 (SB-1) and 3 (rHVT). Our results show that, regardless of the origin of the vaccine, protection against early challenge with 648A was good when vaccines were administered at a high dose (>3000 plaque-forming units [PFU]). Differences among vaccines, however, were detected even when using a high dose in experiment 2 (vaccine CVI988-B conferred higher protection than did CVI988-C) but not in Experiment 1 (CVI988-B was compared to CVI988-A). The use of a fixed low dose (2000 PFU) of vaccine resulted in reduction in protection, and such reduction was more remarkable when using CVI988-A. No statistically significant differences were found when we compared the efficacy of CVI988 in two different genetic lines of broiler chickens (G1 and G2). Vaccination protocols that included CVI988 had better protection than protocols that only included MD vaccines of serotypes 2 and 3. This was true regardless of the vaccine protocol used (CVI988/rHVT SB-1; CVI988 rHVT SB-1/None; rHVT SB-1/CVI988; wherein the vaccine before the slash (/) was administered in ovo at embryonation day 18 and the vaccine after the slash was administered at day of age, subcutaneously). When only vaccines of serotypes 2 and 3 were used, protection against early challenge with vv MDV was higher when vaccines were administered in ovo (rHVT SB-1/None) than if vaccines were administered at hatch (None/rHVT SB-1). Monitoring vaccine DNA load in feather pulp (FP) samples at 1 wk was used to monitor vaccination, and results showed that differences in vaccine replication exist among vaccines but such differences were not necessarily related to protection (r  =  0.41, P  > 0.05). Monitoring load of challenge MDV DNA in FP at 21 days was conducted, and results correlated (r  =  0.85, P  < 0.05) with the percentage of chickens with MD lesions at the termination of the study, confirming that early diagnosis is a very powerful tool with which to evaluate protection.

The wooden breast condition is a myopathy affecting the pectoralis major (p. major) muscle in fast-growing commercial broiler lines. Currently, wooden breast–affected birds are phenotypically detected by palpation of the breast area, with affected birds having a very hard p. major muscle that is of lower value. The objective of this study was to compare the wooden breast myopathy in two fast-growing broiler lines (Lines A and B) with incidence of wooden breast to a slower growing broiler Line C with no phenotypically observable wooden breast. One of the characteristics of the wooden breast condition is fibrosis of the p. major muscle. Morphologic assessment of Lines A and B showed significant fibrosis in both lines, but the collagen distribution and arrangement of the collagen fibrils was different. In Line A, the collagen fibrils were tightly packed, whereas in Line B the collagen fibrils were diffuse. This difference in collagen organization may be due to the expression of the extracellular matrix proteoglycan decorin. Decorin is a regulator of collagen crosslinking and is expressed at significantly higher levels in Line A wooden breast–affected p. major muscle, which would lead to tightly packed collagen fibers due to high levels of collagen crosslinking. Furthermore, expression of the muscle-specific transcriptional regulatory factors for proliferation and differentiation of muscle cells leading to the regeneration of muscle in response to muscle damage was significantly elevated in Line A, and only the factor for differentiation, myogenin, was increased in Line B. The results from this study provide initial evidence that the etiology of the wooden breast myopathy may vary between fast-growing commercial broiler lines.

In high-challenge areas, 1-day-old chicks are often vaccinated with fowlpox vaccine to provide early protection against the disease. However, we were unable to find any information in the published literature on the safety and efficacy of live fowlpox virus vaccine in 1-day-old turkeys. In this study, we evaluated a freeze-dried chicken-embryo–origin live fowlpox virus vaccine for its safety and efficacy in 1-day-old turkey poults by administering the vaccine subcutaneously in the upper back of the neck. Following vaccination, the turkeys were observed for 3 wk for vaccine-associated mortality and adverse reactions. Efficacy was evaluated by challenging the turkeys against a standard challenge strain of fowlpox virus. The results of this study indicated that the vaccine was safe and efficacious for subcutaneous administration in 1-day-old turkeys. None of the vaccinated turkeys revealed any adverse reactions or mortality associated with the vaccine. The vaccine protected more than 98% of the turkeys against fowlpox virus challenge.

On March 2013, the Libyan poultry industry faced severe outbreaks due to mixed infections of APMV-1 (Newcastle disease) and low pathogenic avian influenza (AI) of the H9N2 subtype which were causing high mortality and great economic losses. APMV-1 and H9N2 were isolated and characterized. Genetic sequencing of the APMV-1/chicken/Libya/13VIR/7225-1/2013 isolate revealed the presence of a velogenic APMV-1 belonging to lineage 5 (GRRRQKR*F Lin.5) or genotype VII in class II, according to the nomenclature in use. Three AI viruses of the H9N2 subtype, namely A/avian/Libya/13VIR7225-2/2013, A/avian/Libya/13VIR7225-3/2013, and A/avian/Libya/13VIR7225-5/2013, were isolated and found to belong to the G1 lineage. Analysis of amino acid sequences showed that the analyzed H9N2 viruses contained the amino acid Leu at position 226 (H3 numbering) at the receptor binding site of the HA, responsible for human virus-like receptor specificity. On March 2014, an outbreak of highly pathogenic avian influenza (HPAI) virus of the H5N1 subtype was diagnosed in a backyard poultry farm in an eastern region of Libya. The H5N1 isolate (A/chicken/Libya/14VIR2749-16/2014) was detected by real time RT-PCR (rRT-PCR). Genetic characterization of the HA gene revealed that the identified subtype was highly pathogenic, belonged to the 2.2.1 lineage, and clustered with recent Egyptian viruses. This study revealed the presence of a velogenic APMV-1 genotype and of two influenza subtypes, namely HPAI H5N1 and H9N2, which are of major interest for public and animal health. Considering these findings, more investigations must be undertaken to establish and implement adequate influenza surveillance programs; this would allow better study of the epidemiology of APMV-1 genotype VII in Libya and evaluation of the current vaccination strategies.

Infectious bronchitis virus (IBV) in vaccinated chicken flocks continues to cause enormous economic losses to the poultry industry in Iran. A molecular surveillance of IBV genotypes involved in outbreaks of disease was performed. Specimens of trachea, kidney, and cecal tonsil were collected from 250 suspected flocks (more than 2500 samples) and identified between 2010 and 2014. Partial spike glycoprotein gene sequences revealed seven distinct genotypes, including Mass, 793/B, IS720, Variant 2, QX, IR-I, and IR-II, to be circulating in the chicken farms. The majority of flocks (67.6%) experienced infection with an IBV variant unrelated to the vaccine strains. These variants displayed homologies ranging from 54.1% to 78.5% and from 53% to 86% with H120 and 4/91, respectively. These findings reveal the existence of IBV variants genetically different from the vaccine strains currently in use and explain the outbreaks of disease observed in the field. The current work constitutes the first comprehensive survey of IBV in Iran and emphasizes the need for continuous monitoring and rethinking of current preventative measures.

Erysipelothrix rhusiopathiae causes erysipelas in many vertebrate species. Severe disease outbreaks have been noted in many poultry species—chickens, ducks, emus, pheasants, pigeons, and geese. This article describes the biochemical and genetic analyses of six E. rhusiopathiae strains isolated from geese for meat production. The isolates came from birds kept in different poultry houses on one farm, and were collected during two erysipelas outbreaks. We analyzed and compared the isolates by random amplified polymorphic DNA with the use of NK6 primer and pulsed-field gel electrophoresis, with the restriction enzyme SmaI. Biochemical examination was performed with API Coryne test. Analyses showed that the three strains isolated during the first outbreak differed, whereas the three isolates from the second outbreak were identical to one another, but distinct from the isolates from the first outbreak. The results of biochemical and genetic analyses of E. rhusiopathiae strains isolated from geese suggest different sources of infection for the erysipelas outbreaks.

Respiratory infections are a common cause for increased mortality rates in poultry worldwide. To improve intervention strategies, circulating pathogens have to be identified and further characterized. Because of the lack of diagnostic tools, it was not known what pathogens contribute to the high mortality rates in association with respiratory disease in Algeria. Our objective was to determine if primary pathogens including Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), avian influenza virus (AIV), infectious bronchitis virus (IBV), and avian metapneumovirus (aMPV), known to be present in neighboring countries, can also be detected in Algerian chicken and turkey flocks. Results demonstrate the circulation of the investigated pathogens in Algerian poultry flocks as multi-infections. Phylogenetic characterization of the Algerian IBV strains confirmed the circulation of nephropathogenic viruses that are different from the strains isolated in neighboring countries. This could suggest the existence of a new IBV genotype in North Africa. Additionally, we detected for the first time an aMPV subtype B field strain and avian influenza virus. Interestingly, all viral pathogens were present in co-infections with MG, which could exacerbate clinical disease. Additional pathogens may be present and should be investigated in the future. Our results suggest that multiple respiratory infections may be responsible for high mortality in Algerian poultry flocks and very probably also in other regions of the world, which demonstrates the need for the establishment of more comprehensive control strategies.

Three outbreaks of necrotic enteritis–like disease associated with Clostridium sordellii were diagnosed in commercial broiler chicken flocks with 18,000 to 31,000 birds between 18 and 26 days old. Clinical signs in the affected flocks included high mortality up to 2% a day, depression, and diarrhea. The main gross changes included segmental dilation of the small intestine with watery contents, gas, mucoid exudate, and roughened and uneven mucosa, occasionally covered with a pseudomembrane. Microscopic lesions in the small intestine were characterized by extensive areas of coagulative necrosis of the villi, fibrinous exudate in the lumen, and high numbers of large, Gram-positive rods, occasionally containing subterminal spores, seen in the necrotic tissue and lumen. These rods were identified as C. sordellii by immunohistochemistry. Clostridium sordellii was isolated in an almost pure culture from the intestine of affected birds. A retrospective study of commercial broiler chicken and turkey submissions to the California Animal Health and Food Safety Laboratory System revealed that C. sordellii had been isolated from intestinal lesions in outbreaks of necrotic enteritis–like disease in 8 of 39 cases, 5 times together with Clostridium perfringens and 3 times alone. The latter three cases are reported here.

The present case report describes a remarkable feature of Histomonas meleagridis characterized by aberrant clinical appearance and pathomorphologic lesions, which were mainly confined to the ceca, noticed during a field outbreak of histomonosis. In a flock of meat turkey toms, sudden death was noticed at the end of week 5 in the absence of specific clinical signs. Instead of the well-known sulfur-colored feces, some caseous cores were found in the litter. Mortality up to 17% per week was noticed in the first 2 wk of observation, after which it declined to approximately 1% per week. In the 10th week of life roughly 31% of the birds had died before the remaining birds were killed to preclude further economic losses due to insufficient growth or continuing mortality. Necropsy of affected birds on the farm and during a more detailed investigation of 15 birds prior to the killing of the flock revealed severe lesions in the ceca characterized by thickened cecal walls filled with necrotic and caseous material. Additionally, some ruptured and necrotic ceca were noticed together with localized peritonitis. Despite such severe typhlitis, only one of the sectioned birds showed pathomorphologic changes in the liver. Test tube flotation from collected fecal samples revealed only sporadic occurrence of coccidial oocysts and no nematodes. However, the presence of H. meleagridis was confirmed by PCR and/or immunohistochemistry, with specific antibodies against the parasite in a majority of the investigated ceca and in four liver samples. Remarkably, genetic characterization revealed H. meleagridis genotype 2, about which no detailed investigations have been reported so far. Although PCR detected a concurrent presence of Tetratrichomonas gallinarum, an involvement in the lesions could be excluded based upon histologic investigations. Finally, infection with Escherichia coli and Gallibacterium anatis was demonstrated by bacteriologic smears of internal organs, most likely a secondary infection. Altogether, the results demonstrate an aberrant clinical appearance and pathomorphology in turkeys suffering from histomonosis. Pathomorphologic changes were characterized by severe inflammation of the ceca with minimal liver involvement, indicating a different pathogenesis of H. meleagridis genotype 2.

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