Robert J. Eckroade

Characteristics of H7N2 (Nonpathogenic) Avian Influenza Virus Infections in Commercial Layers, in Pennsylvania, 1997-98

Between January 1997 and March 1998, 11 cases of H7N2 avian influenza (nonpathogenic) were diagnosed at the Laboratory of Avian Medicine and Pathology, Kenneth Square, PA. These cases involved either commercial leghorn laying hens or leghorn pullets raised in Pennsylvania. Grossly and histologically, the most striking lesion associated with disease was salpingitis, usually with edema and occasionally with oviduct necrosis. Fluid, fibrinous, and egg yolk material in the peritoneum (egg yolk peritonitis) as well as pulmonary congestion and pulmonary edema were also frequently seen. Oviduct lesions have rarely been described in association with avian influenza infections in previous outbreaks. Mortality in affected houses was mild to moderate (less than 4% total mortality during the outbreak), with concurrent mild to moderate egg production declines (2%-4% at the time of disease onset).

Evaluation of the efficacy of a live fowlpox-vectored infectious laryngotracheitis/avian encephalomyelitis vaccine against ILT viral challenge.

Abstract Infectious laryngotracheitis (ILT) is caused by an alphaherpesvirus, and latency can be produced by previous exposure to vaccine virus. The main sites of latency for the ILT virus have been shown to be the trigeminal ganglion and the trachea. Reactivation of latent virus is one factor related to the production of clinical signs. The development of a genetically engineered ILT vaccine has been suggested for many years as a tool to eliminate viral latency. Several approaches have been suggested. Included among them is the development of a thymidine kinase–deficient mutant or the insertion of ILT viral glycoproteins into a viral vector such as a poxvirus. A commercially available, live, fowlpox-vectored infectious laryngotracheitis + avian encephalomyelitis (FP-LT+AE) vaccine was used in field trials in leghorn pullet flocks and evaluated by tracheal challenge in a laboratory setting with the use of the National Veterinary Services Laboratory (Ames, IA) ILT challenge virus. Interference of the pigeon pox vaccine, which is often administered concurrently with fowlpox vaccine, was also evaluated when given in conjunction with the FP-LT+AE vaccine. Overall, the results indicate that the FP-LT+AE vaccine provides adequate protection against ILT viral challenge. Proper administration is essential. In one flock, inadequate protection was most likely a result of either poor vaccine administration or previous exposure to pox virus. In addition, the simultaneous administration of pigeon pox vaccine did not appear to interfere with protection against ILT viral challenge.

Duck Viral Enteritis in Domestic Muscovy Ducks in Pennsylvania

Duck viral enteritis (DVE) outbreaks occurred at two different locations in Pennsylvania in 1991 and 1992. In the first outbreak, four ducks died out of a group of 30 domestic ducks; in the second outbreak, 65 ducks died out of a group of 114 domestic ducks, and 15 domestic geese died as well. A variety of species of ducks were present on both premises, but only muscovy ducks (Cairina moschata) died from the disease. On necropsy, gross lesions included hepatomegaly with petechial hemorrhages, petechial hemorrhages in the abdominal fat, petechial hemorrhages on the epicardial surface of the heart, and multifocal to coalescing areas of fibrinonecrotic material over the mucosal surface of the trachea, esophagus, intestine, and cloaca. Histologically, the liver had random multifocal areas of necrosis and eosinophilic intranuclear inclusion bodies in hepatocytes. DVE virus was isolated and identified using muscovy duck embryo fibroblast inoculation and virus neutralization.

Field Observations with Salmonella enteritidis Bacterins

A study involving 11 commercial layer flocks was conducted to determine the efficacy of Salmonella enteritidis bacterins (autogenous or federally licensed). The criterion for evaluation of vaccine efficacy was the presence or absence of S. enteritidis in the environment, the organs of the bird (including ovary and oviduct), and eggs. Environmental, rodent, and organ specimens from dead birds as well as eggs were cultured throughout the life of the flock. All layers were obtained from pullet sources that were negative for S. enteritidis, as determined by organ and environmental cultures. Despite the use of S. enteritidis vaccination, 63.6% of the houses had S. enteritidis-positive environmental cultures and 100% of the flocks had S. enteritidis organ-culture-positive birds. The range of positive cultures for S. enteritidis in the environment in vaccinated flocks was between 0 and 45.5%. Birds in vaccinated flocks were organ-culture positive for S. enteritidis between 10% and 40% of the time. The unvaccinated portion of flocks in the same house and the unvaccinated flock in a complex had similar results compared with the vaccinated portion of the flocks.

An enzyme-linked immunosorbent assay that measures protective antibody levels to Newcastle disease virus in chickens.

An enzyme-linked immunosorbent assay (ELISA) was developed to measure antibodies to Newcastle disease virus (NDV) in chickens. Chickens 6 to 33 weeks old, with a variety of vaccination histories, were bled before challenge with a velogenic strain of NDV. Fourteen days post-challenge, 63 of the 73 challenged birds had survived. ELISA results of pre-challenge sera corresponded directly with survival rates of birds challenged with NDV.

A review of the 1996-98 nonpathogenic H7N2 avian influenza outbreak in Pennsylvania

Abstract The nonpathogenic avian influenza (AI) outbreak in Pennsylvania began in December 1996 when there was a trace back from a New York live bird market to a dealers flock. A total of 18 commercial layer flocks, two commercial layer pullet flocks, and a commercial meat turkey flock were diagnosed with nonpathogenic AI (H7N2) viral infection with an economic loss estimated at between

Comparison of an Antigen-capture Enzyme Immunoassay with Virus Isolation for Avian Influenza from Field Samples

3 and

Monoclonal antibody-based detection system for Salmonella enteritidis.

4 million. Clinical histories of flocks infected with the disease included respiratory disease, elevated morbidity and mortality throughout the house, egg production drops, depression, and lethargy. A unique gross lesion in the commercial layers was a severe, transmural oviduct edema with white to gray flocculent purulent material in the lumen. Layer flocks on two separate premises were quarantined but permitted to remain in the facilities until cessation of virus shed was determined through virus isolation. Several months later, clinical AI appeared again in these flocks. It is not known whether the recurrence of disease in these cases is due to persistence of the organism in the birds or the environment. In addition to serologic testing and virologic testing by chicken embryo inoculation, an antigen capture enzyme immunoassay was evaluated as a diagnostic tool for AI. Research projects related to disinfection, burial pits, and geographical system technology were developed because of questions raised concerning transmission, diagnosis, and control of nonpathogenic AI (H7N2).

Evaluation of disinfectants with the addition of antifreezing compounds against nonpathogenic H7N2 avian influenza virus.

The standard tests used to detect avian influenza (AI) viral infection include virus isolation from tissues of the infected birds and the detection of AI antibody in blood or egg yolk. A new application of an existing human test to rapidly detect the presence of any influenza A virus is now possible. A commercially available antigen-capture enzyme immunoassay (AC-EIA), developed for the detection of influenza A in humans was tested for relative sensitivity and specificity and for speed of use in diagnosing nonpathogenic H7N2 AI in naturally infected poultry. During the recent nonpathogenic H7N2 AI epornitic, the AC-EIA was used for rapid diagnosis and quarantine decisions. Between February and August 1997, 1524 samples from 295 commercial layer, pullet, and broiler flocks were submitted to the Laboratory of Avian Medicine and Pathology, New Bolton Center, for AI virus isolation and testing by AC-EIA. The relative specificity of the AC-EIA was 100% and the relative sensitivity was 79%. We believe that the AC-EIA will be a useful adjunct to standard AI diagnostic tests.

Differences Among Restriction Endonuclease DNA Fingerprints of Pennsylvania Field Isolates, Vaccine Strains, and Challenge Strains of Infectious Laryngotracheitis Virus

Two monoclonal antibodies that react with Salmonella enteritidis in chicken tissue, eggs, and environmental samples were used to develop a rapid enzyme-linked immunosorbent assay (ELISA) screen and agglutination assay for the specific detection of S. enteritidis. S. enteritidis was detected in 100% of egg samples and 99.8% of various field and research samples by both ELISA and traditional microbiological isolation and identification techniques. Results of titer experiments indicate that as few as 10(4) organisms can be detected by ELISA.