Epidemiology, production losses, and control measures associated with an outbreak of avian influenza subtype H7N2 in Pennsylvania (1996-98).

An outbreak of H7N2 low-pathogenicity (LP) avian influenza (AI) occurred in a two-county area in Pennsylvania from December of 1996 through April of 1998. The outbreak resulted in infection of 2,623,116 commercial birds on 25 premises encompassing 47 flocks. Twenty-one (one premise with infection twice) of the twenty-five infected premises housed egg-laying chickens and one premise each had turkeys, layer pullets, quail, and a mixed backyard dealer flock. Despite dose proximity of infected flocks to commercial broiler flocks, no infected broilers were identified. Experimentally, when market age broilers were placed on an influenza-infected premise they seroconverted and developed oviduct lesions. The outbreak was believed to have originated from two separate introductions into commercial layer flocks from premises and by individuals dealing in sales of live fowl in the metropolitan New York and New Jersey live-bird markets. Source flocks for these markets are primarily in the northeast and mid-Atlantic areas, including Pennsylvania. Mixed fowl sold include ducks, geese, guinea hens, quail, chukar partridges, and a variety of chickens grown on perhaps hundreds of small farms. Infections with the H7N2 AI virus were associated with variable morbidity and temporary decreases in egg production ranging from 1.6% to 29.1% in commercial egg-laying chickens. Egg production losses averaged 4.0 weeks duration. Mortality ranged from 1.5 to 18.3 times normal (mean of 4.3 times normal). Duration of mortality ranged from 2 to 13 weeks (average of 3.9 weeks) in flocks not depopulated. Lesions observed were primarily oviducts filled with a mucous and white gelatinous exudates and atypical egg yolk peritonitis. Quarantine of premises and complete depopulation were the early measures employed in control of this outbreak. Epidemiological studies suggested that depopulation furthered the spread of influenza to nearby flocks. Thereafter, later control measures included quarantine, strict biosecurity, and controlled marketing of products.

Management and environmental risk factors for Salmonella enteritidis contamination of eggs.

OBJECTIVE: To analyze data for 60 poultry flocks voluntarily enrolled in the Pennsylvania Salmonella enteritidis Pilot Project and determine management and environmental risk factors associated with production of S enteritidis-contaminated eggs. SAMPLE POPULATION: 60 flocks for which at least 1 environmental sample (manure or egg-handling equipment) was positive for S enteritidis. PROCEDURE: Samples of manure, egg-handling equipment, and mice were submitted for bacterial culture of S enteritidis. When S enteritidis was isolated from environmental samples, 1,000 eggs were collected from the flock every 2 weeks for 8 weeks and submitted for bacterial culture. RESULTS: 18 flocks were found to have produced contaminated eggs. Estimated overall prevalence of contaminated eggs was 2.64/10,000 eggs produced, but flock-specific prevalence ranged from 0 to 62.5/10,000 eggs. Flocks with high levels of manure contamination were 10 times as likely to produce contaminated eggs as were flocks with low levels. However, 5 flocks with low levels of manure contamination produced contaminated eggs. CONCLUSIONS: Evaluation of the level of manure contamination could be used to help identify flocks at risk of producing S enteritidis-contaminated eggs. CLINICAL RELEVANCE: Flocks with high levels of S enteritidis-contaminated manure appeared to pose the greatest public health threat, and on-farm programs to reduce the prevalence of egg contamination should be developed for farms with high levels of manure contamination. Efforts to reduce the overall number of on-farm pathogens should decrease the incidence of foodborne disease in humans.

Interpretations of antibody responses to Salmonella enterica serotype enteritidis gm flagellin in poultry flocks are enhanced by a kinetics-based enzyme-linked immunosorbent assay.

Many regulatory and diagnostic programs for the detection of Salmonella enterica serotype Enteritidis infection in commercial poultry flocks have relied on rapid Pullorum agglutination tests to screen birds because of the shared antigens of S. enterica Enteritidis and S. enterica Pullorum and Gallinarum; however, the use of the enzyme-linked immunosorbent assay (ELISA) format affords better analytical sensitivity than crude agglutination tests. In this study, we adapted our earlier conventional indirect ELISA, using gm flagellin as the antigen, to a kinetics-based, computer-controlled ELISA (KELA). The KELA was used to screen for flagellin antibody from three commercial flocks: (i) a large flock involved in a U.S. Department of Agriculture trace back from a human S. enterica Enteritidis foodborne outbreak (n = 3,209), (ii) a flock infected with the endemic S. enterica Enteritidis serotype but which also had multiple other Salmonella serotypes (n = 65), and (iii) an S. enterica Pullorum-infected flock (n = 12). The first flock (S. enterica Enteritidis prevalence of 2.45% based on culture) provided a field test of the KELA and allowed the calculation of diagnostic sensitivity (D-Sn) and diagnostic specificity (D-Sp). With a cutoff of 10 (used for screening flocks [i.e., high sensitivity]), the KELA has a D-Sn of 95.2% and a D-Sp of 18.5%; with a cutoff of 140 (used in confirmatory flock testing [i.e., high specificity]), the KELA has a D-Sn of 28.0% and a D-Sp of 99.1%. We found that with a cutoff of 60 (D-Sn = 63.1%; D-Sp = 91.6%), we could eliminate reactions in the KELA caused by other non-S. enterica Enteritidis salmonellae. The KELA was also compared to two commercial rapid Pullorum tests, the Solvay (D-Sn = 94.9%; D-Sp = 55.5%) and the Vineland (D-Sn = 62.0%; D-Sp = 75.3%).

Prevalence of Alcaligenes faecalis in North Carolina broiler flocks and its relationship to respiratory disease.

In order to assess the role of Alcaligenes faecalis in respiratory disease of broilers, a study was conducted to determine the prevalence of this bacterium in North Carolina broilers and to determine the relationship of A. faecalis infection to clinical disease. Our studies showed that A. faecalis is prevalent in North Carolina commercial broilers during the winter months. Bacteriological examination of turbinates and tracheas revealed that almost 40% of individual birds between 35 and 45 days of age yielded positive cultures; 62% of tested flocks were infected. When present, A. faecalis was usually the predominant bacterium isolated. Furthermore, because of a higher frequency of A. faecalis isolation in broiler flocks with respiratory disease (75% vs. 29% in flocks without respiratory diseases), these studies suggest a causal relationship between this bacterium and clinical respiratory disease.

Acute hemolytic anemia, methemoglobinemia, and heinz body formation associated with ingestion of red maple leaves by horses.

From June 1975 through June 1979, acute hemolytic anemia developed in 11 horses from 7 New York farms. Of the 7 horses that died, 6 had methemoglobinemia. In the 4 horses that recovered, methemoglobinemia was not observed. but Heinz body formation was seen in 3 of the 4. On 2 of the premises involved, frank methemoglobinemia was observed concurrently with Heinz body formation, suggesting a relationship between the pathogenesis of methemoglobinemia and Heinz body formation in the hemolytic process. In addition to the 11 cases described, 22 clinically similar cases were reported to us during the period of this investigation by practicing veterinarians from New York, Pennsylvania, and the New England states. All 33 cases of hemolytic anemia occurred between June and October of each year, and affected horses had access to outside paddocks or fields containing a variety of native grasses, weeds, and trees. On 2 farms, hemolytic anemia developed after the horses were observed browsing fallen branches of red maple trees (Acer rubrum). Red maple leaves and bark were obtained from 1 of these farms, and approximately 1 kg of a leaf and bark mixture was fed to each of 2 ponies. Within 48 hours, both ponies became ill. The syndrome was indistinguishable from that observed in clinical patients and was characterized by methemoglobinemia and intravascular hemolysis. The ponies died 5 and 6 days after which time the packed cell volumes were 6% and 7% respectively. It was concluded that many cases of hemolytic anemia in horses in northeastern states may be related to ingestion of leaves or bark from red maple trees. The studies did not, however, define the factors that predispose to poisoning and did not exclude the possibility that other environmental toxins may have been involved.

Use and limitations of profiles in assessing health or nutritional status of dairy herds.

A number of factors limit the usefulness of blood or metabolic profiles. These include sampling problems, low correlations with nutrient intake, inconsistent patterns in disease, and difficulties in interpretation. Despite these limitations, profiles properly used may serve as an adjunct to more conventional technology in alleviating some dairy herd problems. Their use appears justified when feed analysis, ration evaluation, disease testing, and checks on management do not alleviate herd problems. Considerable potential for misuse of profiles exists due to the complexities of interpretation.

Abortion storms--projection for the future.

Most abortions are of an endemic and sporadic nature but some problems reach epidemic (storm) proportions. In many laboratories, the etiological agent is determined in about 25% of the cases. In the future, practitioners and laboratories working together can: 1) respond to owner concern, 2) quickly determine if one of the better defined contagious diseases is present, and 3) cooperate in developing a responsive, field oriented diagnostic and investigative program designed to better define factors concerned in abortion problems. A program for meeting these needs is suggested.