Layer/Pullet Regional Disease Update – Northeast US

Patricia A. Dunn, DVM, MAM, DACPV Pennsylvania State University, Animal Diagnostic Laboratory PA, USA


Pennsylvania (PA) has very diverse avian industries with respect to species, production types and end markets, and is ranked in the top 5 states in the US for egg production. This presentation concentrates on egg-type chicken disease conditions of interest in PA and other northeastern states. A general summary of diagnoses from submissions to the Pennsylvania Animal Diagnostic Laboratory System (PADLS), field observations from veterinarians and managers, and selected research projects will be addressed.

Diagnostic Laboratory Submission Diagnoses – PADLS (2014 / 2015)

Chicks: Bacterial omphalitis / yolk sac infection / septicemia was the most frequent diagnosis. The 2 bacteria most commonly cultured were E. coli and Enterococcus sp., followed by the group including Staphylococcus, Proteus, Salmonella (not Group D) spp. Other bacteria including Klebsiella, Pseudomonas, and Enterobacter spp. were isolated least frequently. Starvation/ dehydration / gout were in the moderate frequency group, and infrequently diagnosed conditions included aspergillosis, cellulitis, ascites / hydropericardium, and rickets.

Pullets: High frequency diagnoses were coccidiosis, necrotic enteritis and E. coli infections. Reactions to killed vaccines (cellulitis/ myositis, “post SE bacterin syndrome”), aspergillosis, rickets, Marek’s disease, avian encephalomyelitis (AE) (post live vaccine administration), corneal ulcers and staphylococcal infections were present in the low to moderate frequency group. Dehydration / gout, vaccinal infectious laryngotracheitis and paramyxovirus 1 (PMV-1) were of very low frequency.
Layers: Bacterial peritonitis was the most frequent diagnosis, from which E. coli was the predominant bacterium isolated. Other bacteria, including Pasteurella multocida, Enterococcus sp., Gallibacterium sp., Staphylococcus sp., Streptococcus sp., Mannheimia sp., were infrequently isolated. Enteritidis (including focal duodenal necrosis (FDN), necrotic enteritis, non-specific enteritis and coccidiosis) and calcium depletion/ inadequate bone mineralization were in the moderate group. Intestinal helminth parasitism (cestodes, nematodes), cannibalism / vent-picking, and renal conditions (gout, urolithiasis, dehydration) were noted in a low number of cases. Northern fowl mite infestations, fatty liver, staphylococcal arthritis, pox virus, bite wounds were noted in a single case or few cases. Mycoplasmosis, when noted, was usually referring to serologic positives.
In addition, virus detections in pullet and layer cases were often noted. Infectious bronchitis virus (IBV) was detected in more than 30 cases, most by PCR, of which less than one-third were confirmed by virus isolation. Serotypes were noted for 8 of these: Arkansas, DMV/1639/11 (nephropathogenic) were each listed twice, and Mass, DMV/2392/12, variant 93% similar to DMV/5642/06, “2015 field isolate” were each listed once. Reoviruses and adenoviruses type 1 were isolated in several cases (most in pullets), but the clinical significance of most of these detections is unclear.

Field observations

Some conditions of interest are as follows:
Avian influenza (AI). No detections of notifiable AIV were made in the layer industry for the past several years. PA has had a robust monitoring program for AI in all sectors since the 1982/83 HPAI H5N2 outbreaks. There has been much success in controlling AI in the northeast live bird marketing system in the past decade, which has reduced the likelihood of AIV strains persisting and evolving in the markets, and spilling back into supply flocks in the region. The general trend since 2009 has been towards significantly fewer PA investigations triggered by trace backs from the markets, and a low baseline number of investigations triggered by other in-state testing. The very recent detections of HPAI H5 AIVs in western Canada and US, and in Minnesota, are of great interest to our industry, and the need for continued surveillance and constant vigilance for these new intercontinental strains is recognized.

Salmonella enteritidis (SE). SE vaccination and the mitigation of important risk factors have been highly successful in reducing SE on our region. However, an unfortunate side effect of vaccination, “post- SE bacterin syndrome”, continues to occur sporadically in some flocks. Host genetics likely play a role, but no other specific risk factors or effective interventions have been found in the Northeast.
E.coli peritonitis. These layer infections are much less widespread and less severe than several years ago, but still present sporadic problems in some flocks. Use of the modified live vaccine has been adopted by many companies, and this has been very effective in preventing E. coli losses in several complexes. Multiple applications (2 or 3) during the chick/ pullet phase are used by some in higher risk situations. Others use the vaccine reactively in the face of an outbreak. Still others use a combination of these strategies.

Coccidiosis and necrotic enteritis (NE). Breaks of small intestinal coccidiosis and associated necrotic enteritis are common problems in some flocks, usually in early lay. Generally, more problems are seen in belt houses than high-rise. These diseases can be more of a problem in some genetic strains than others. Coccidiosis vaccines are being used to ensure exposure and immunity that should reduce the clinical disease in the lay house. There may also be more problems in winter, when very dry conditions don’t allow for good viability and cycling of the vaccine oocysts to achieve solid immunity. Coccidiosis and NE can also be problems in floor pullets according to one manager.

Focal duodenal necrosis (FDN). FDN continues to be detected in some flocks in PA as well as Connecticut if one looks for it. Decreased case weight is the major production problem noted in affected flocks. Continuous BMD in the feed is highly effective for prevention.

Infectious laryngotracheitis (ILT). There have been a few issues in Maryland, Delaware, PA and Maine in which it appears that the vectored vaccine did not hold against challenge in the lay house. In early 2014 in Maine, the ILT- associated mortality was 1- 3% in younger layers, and up to 5 – 6% in older hens in 1 operation.

Infectious bronchitis (IB). Clinical IBV has been seen in a few instances in layers in PA in which there were significant egg production drops, shell issues (“sandy shells”) and kidney damage. High ELISA serology titers were detected. Virus isolations were not done in most instances.

Intestinal helminth parasitism (nematodes, cestodes). Control of intestinal worms is considered a major problem in cage-free flocks in the region. Without effective treatments, this is likely to continue.

Acariasis (northern fowl mite infestation). This condition is often sub-clinical, but heavy infestations are known to impact health and egg production in affected flocks. The use of granular elemental sulphur in the feed is reportedly helping, but does not eradicate the problem.

Peripheral neuropathy (PN). This condition was mentioned by 1 contributor as occurring sporadically in pullet flocks of 1 breed. There is onset of leg paralysis at 7 – 8 weeks, and most pullets recover.

Hysteria, feather-picking, feather-eating. These conditions are seen occasionally in organic flocks, and can be hard to control once the behavior is set. The dietary methionine requirement is likely not being met under certain conditions, particularly when addition of synthetic methionine is not allowable. Other dietary factors may be involved in specific cases.

Infectious bursal disease, Marek’s disease, pox, Newcastle disease, mycoplasmosis, mycotoxicosis. These conditions are described as “baseline” or “quiet”.


Disease topics addressed by veterinarians and other scientists at Penn State University (PSU) include:

Salmonella enteritidis (SE). A USDA-funded study designed to examine the risk factors for and incidence of SE from multiple samples from small and medium-sized flocks in PA and Iowa is nearly completed. The data analyzed to date suggest that the 2 most important risk factors for SE contamination inside the bird area and in the eggs are the presence of SE positive rodents and the absence of vaccination for SE. A project just funded by the Pennsylvania Department of Agriculture (PDA) will focus on sampling table eggs obtained at Farmer’s markets and roadside stands in PA for SE.

FDN. The lesions of FDN were first described at our laboratory in 1996. Since then, several PA-based research studies have been conducted. Some findings of the most recent project completed in 2014 and funded by the PA Poultry Industry Research Check-off Program include:

  • In flocks fed certain direct fed microbials (DFMs) continuously starting at different times, those in which the DFM was started at least 2 weeks prior to move to the lay house had significantly fewer birds positive for FDN than flocks fed the same DFM that was started at the layer house.
  • Coccidia counts (oocysts per gram of feces) were unexpectedly high in multiple samplings of several of the test flocks.
  • No correlation of presence, absence or relative burden of cestodes with presence or absence of FDN in individual hens was evident.
  • Body weight was not affected in hens with FDN lesions compared to those without lesions.
  • By 16S rRNA PCR assays on fixed tissue lesions, the most common family of bacteria associated with FDN was Clostridiaceae. Specific DNA for Clostridium colinum was not detected by the methods employed in this study. These methods did, however, detect C. colinum in at least 1 sample of fixed tissues from quail with ulcerative enteritis lesions used in this study for comparison.

Avian intestinal spirochetosis (brachyspirosis). Previous research projects in our laboratory, based on investigations into “dirty egg” problems, were funded by the PA Poultry Industry Research Check-off Program and Spirogene Pty, Ltd. This work led to the use of PCR tests for Brachyspira spp., including B. intermedia and B. pilosicoli, in our lab. A survey using these methods showed that the presence of one or both of these bacteria was common in older layer flocks in PA. The tests continue to be used for in-state and out-of-state samples as requested.

Marek’s Disease. As part of a current NIH-funded project led by researchers at PSU and the Pirbright Institute in the United Kingdom, presence and levels of Marek’s disease virus (MDV) in PA chicken house dust are being evaluated. In this study, the vaccine strains can be differentiated from wild-type viruses by molecular methods. Results to date show that the pullet and layer house dust samples have much less wild- type MDV that certain broiler and broiler breeder operations in our state.

Reovirus. Since 2011, our lab has been engaged in multiple diagnostic and research endeavors on emerging variant reovirus infections in meat-type chickens and turkeys. Questions have arisen about the clinical significance of reoviruses isolated from layer cases. A few layer-origin isolates have been serotyped and genotyped, and shown to be different from the current broiler and turkey isolates of interest. Research proposals to further characterize these viruses by next generation molecular sequencing and by challenge experiments using the broiler pathogenic strains and layer-origin strains in leghorn chickens have recently been accepted for funding by the PA Department of Agriculture and the PA Poultry Industry Research Check-off Program.

From Proceedings of the “Midwest Poultry Federation Convention”, St. Paul, Minnesota, U.S.A.