Epidemiology and financial impact of fowl cholera in turkeys: a retrospective analysis

A retrospective study of the epidemiology and financial impact of fowl cholera (FC) in California meat turkeys during 1984 was performed. Data were collected from 64 flocks--23 FC-outbreak flocks and 41 controls (non-outbreak)--raised in the Central Valley of the state. Mean flock age at the time of the FC outbreak was 11.3 weeks. Flocks that reported a colibacillosis outbreak had increased odds (P = 0.11) of also having an FC outbreak. (This association may or may not indicate a cause-effect relationship.) There was no significant difference between FC-outbreak and control flocks in number of diseases reported, age at onset, or duration of diseases or syndromes except age at onset of roundheart disease. The relative mortality rates were 52% higher in FC-outbreak toms and 26% higher in FC-outbreak hens than in their controls. Medication costs were nearly tripled, and the relative condemnation rate was 60% higher in FC-outbreak flocks than in control flocks. The average costs of FC were nearly $0.40 per bird, or $18,750 per flock, in an outbreak flock of 50,000 birds, and $0.12 per bird, or $6000 per flock, in non-outbreak flocks vaccinated against FC.     

Epidemiologic characterization of Colorado backyard bird flocks

Backyard gallinaceous bird flocks may play an important role in the spread of infectious diseases within poultry populations as well as the transmission of zoonotic diseases to humans. An epidemiologic characterization was conducted of Colorado backyard flocks to gather information on general flock characteristics, human movement of birds, human-bird interaction, biosecurity practices, and flock health. Our results suggest that backyard poultry flocks in Colorado are small-sized flocks (68.6% of flocks had < 50 birds); consist primarily of layer chickens (85.49% of flocks), show chickens (32.18% of flocks), and waterfowl (34.07% of flocks); and are primarily owned for food (meat or egg) production for the family (86.44%) or as pet or hobby birds (42.27%). The backyard flock environment may promote bird-to-bird transmission as well as bird-to-human transmission of infectious disease. Birds are primarily housed with free access to the outside (96.85%), and many are moved from the home premises (46.06% within 1 yr). Human contact with backyard flocks is high, biosecurity practices are minimal, and bird health is negatively impacted by increased movement events. Increased knowledge of backyard bird characteristics and associated management practices can provide guidelines for the development of measures to decrease disease transmission between bird populations, decrease disease transmission from birds to humans, and increase the overall health of backyard birds.     

Isolation of Salmonella Organisms from Commercial Layer Houses Where the Flocks Were Molted with a Wheat Bran Diet

To develop an alternative method to feed withdrawal for molting layers, 2 flocks consisting of approximately 26,000 commercial laying hens each at 478 (68 wk, flock 1) and 466 (67 wk, flock 2) d of age were reared in an environmentally controlled windowless house and were fed wheat bran (WB) diet. Flock 1 hens were fed WB for 25 d, and flock 2 hens were fed WB for 21 d and then fed a mixture of WB and layer feed (1:1, wt:wt) for the last 4 d of the treatment. After that, the birds in both flocks were fed a normal layer feed. The photoperiod was reduced from 16 to 9 h in both flocks. Most of the birds in both flocks ceased egg production by 10 to 15 d of feeding the WB diets. Egg production in flock 1 gradually increased to 11.4% by 31 to 40 d and 71.4% by 41 to 50 d of the treatment, whereas the egg production in flock 2 hens lagged behind by almost 10 d. The mean egg production from 61 to 140 d exceeded 86% in both flocks. The houses in the farm were naturally contaminated with several serovars of Salmonella, not Enteriditis or Typhimurium. In both flocks with the WB treatment, no marked increase in Salmonella isolation from environmental samples was observed postmolt relative to premolt levels. The study demonstrated that feeding hens WB could be successfully used as an alternative to feed withdrawal to force-rest aging hens while not exacerbating a Salmonella problem in a commercial egg-production setting.     

Detection of antibody to Salmonella enteritidis and S typhimurium in the yolk of hens' eggs

Enzyme-linked immunosorbent assays (ELISAs) have been developed to detect IgG antibodies to Salmonella enteritidis and S typhimurium in the yolk of hens' eggs. Better discrimination and more consistent results were obtained between eggs from experimentally infected and uninfected hens by using saline-dilution of yolk rather than chloroform extraction. Threshold absorbance values were determined in three salmonella-free flocks, and on the basis of these results ELISA optical density values greater than 0.25 were considered to be positive for antibodies to salmonella. Four flocks with a history of salmonella infection were examined; three contained birds which were seropositive for S enteritidis by ELISA and from which S enteritidis was isolated, and a large proportion of eggs from these birds contained antibody to S enteritidis. Eggs from the fourth flock had no detectable antibody, although serum antibody was detected in some birds. No salmonellae were isolated from the yolks of the eggs from any of the four flocks.     

Immune responses of breeding chickens to trivalent oil emulsion vaccines: responses to infectious bronchitis

Three similar flocks of broiler breeder parent chickens that had been given live infections bronchitis (IB) vaccines during rearing were injected at 20 weeks of age with three different oil emulsion vaccines: a commercial monovalent Newcastle disease (ND) vaccine (flock A); an experimental bivalent vaccine containing ND and infectious bursal disease (IBD) components (flock B); and an experimental trivalent vaccine containing ND, IBD and IB components (flock C). One week after vaccination 40 hens from flock A and 40 from flock C were taken to the laboratory and their egg yields individually recorded. At 37 weeks of age they were challenged by aerosol exposure to virulent IB virus. The egg production dropped significantly in the hens from flock A but not in the hens from flock C. On the farm, flock C showed a higher mean IB virus antibody titre four weeks after vaccination but titres rose in all three flocks indicating the presence of active IB virus infection. No differences in egg yields were found between the three farm flocks.     

Monitoring the Immune Status of Broilers Against Reoviruses Using Challenge and Serologic Data

Reoviruses are an important cause of suboptimum performance in commercial broilers worldwide. Integrators use the enzyme-linked immunosorbent assay against the S1133 antigen for monitoring serum of breeders for indicating pullet vaccine success. However, without correlating serology to reovirus challenge, it is difficult to determine whether titers reflect protective immunity. We developed a broiler challenge test against 2 common reovirus isolates (2408 and S1133) to evaluate the efficacy of reovirus pullet vaccine programs. Two reovirus serologic and challenge studies were undertaken using chicks from broiler integrators from the southeastern United States. Breeder flocks, from which the chicks were obtained, received at least 1 live and 2 inactivated reovirus vaccines during their pullet phase. One-day-old progeny were collected from 6 breeder flocks. At 1 d of age, 20 chicks from each broiler flock were bled, and serum was analyzed for antibodies. At 3 to 4 d of age, 20 progeny per flock were challenged with the 2408 reovirus by intratracheal route. At 10 to 14 d of age, another 20 birds per flock were challenged with the S1133 reovirus by footpad. Twenty birds per flock were used as nonchallenged controls. At 3 wk of age, all birds were killed and weighed. Percentage of protection was calculated for each flock based on the absence of gross lesions. Flocks with at least 50% protection were considered well protected. Most flocks were well protected against both viruses. The percentage of protection correlated with day-old enzyme-linked immunosorbent assay titers. Chicks from younger hens had higher titers and the best protection against challenge. Producers, whose hen flocks were monitored herein, were doing a good job of immunizing pullets against reovirus. They are now using reovirus progeny challenge studies along with breeder antibody titers to determine vaccination success of their pullets.     

Cases of swollen head syndrome in broiler chickens in Greece

From 50 commercial broiler flocks included in a study concerning respiratory disease, signs of swollen head syndrome (SHS) were shown in eight. Postmortem examination was performed in eight birds showing signs of SHS from each flock. The trachea and head from each bird were collected for laboratory investigation. An enzyme-linked immunosorbent assay (ELISA) was used for the detection of viral and avian mycoplasma antigens in the trachea, and bacteriologic examinations were performed from the infraorbital sinuses of the infected birds. According to the ELISA results, the most frequently detected antigen in the trachea was Mycoplasma synoviae (six flocks, 75%), followed by infectious bronchitis virus (IBV) (five flocks, 62.5%), avian adenovirus (four flocks, 50%), avian reovirus (three flocks, 37.5%), Mycoplasma gallisepticum (one flock, 12.5%), and Newcastle disease virus (NDV) (one flock, 12.5%). Turkey rhinotracheitis (TRT), infectious laryngotracheitis, and avian influenza viral antigens were not detected. Experimental assays for characterization of NDV and IBV isolates showed that they were strains of low virulence (evidently vaccine strains). Bacteriologic examinations from the infraorbital sinuses of the affected birds resulted in the isolation of Escherichia coli (seven cases, 87.5%) and Staphylococcus spp. (one case, 12.5%). It is evident that TRT virus did not play a causal role in SHS in commercial broiler flocks in Greece, but in this condition, other viruses (IBV, NDV), mycoplasmas, or bacteria may be involved, and environmental conditions seem to be essential to the occurrence and severity of the disease.     

Persistence of immunity in commercial egg-laying hens following vaccination with a killed H6N2 avian influenza vaccine

The California poultry industry experienced an outbreak of H6N2 avian influenza beginning in February 2000. The initial infections were detected in three commercial egg-laying flocks and a single noncommercial backyard flock but later spread to new premises. The vaccination of pullet flocks with a commercially prepared, killed autogenous vaccine prior to their placements on farms with infected or previously infected flocks was used as a part of the eradication programs for some multiage, commercial egg production farms. The purpose of this study was to follow three vaccinated flocks on two commercial farms to track the immune responses to vaccination. The antibody-mediated responses of the three flocks followed in this study were markedly different. One flock achieved 100% seroconversion at 12.5 wk of age, but by 32 wk of age, all of the hens were seronegative by agar gel immunodiffusion (AGID). In contrast, at 32 wk of age, flocks from the other farm (flocks 2A and 2B) were 95% and 72% seropositive by AGID, respectively. Of the differences that were identified between the vaccination protocols on the two farms, the distinction that could explain the level of disparity between responses is the delivery of the second dose of vaccine with a bacterin on the first farm, which may have interfered with the persistence of immunity in this flock. Hens from flocks 2A and 2B were experimentally challenged at 25 wk of age with H6N2 avian influenza virus. Hens from flock 2A did not transmit virus to naive contact-exposed hens, but hens from flock 2B did. At 34 wk of age, hens from flock 2A were again challenged and naive contact-exposed hens were infected in this second trial. These challenge experiments served to demonstrate that despite detectable antibody responses in flocks 2A and 2B, the birds were protected from infection for less than 21 wk after the second vaccination.     

Economic effects of clinical chicken anemia agent infection on profitable broiler production.

An outbreak of anemia dermatitis syndrome caused by chicken anemia agent (CAA) occurred in 15 broiler flocks. An average of 29% of chickens in these flocks were derived from a common breeder flock. The breeder flock had no antibody to CAA at 20 weeks of age but had seroconverted by 31 weeks. Diseased broiler flocks were derived from eggs laid by the breeder flock between 25 and 30 weeks of age. CAA infection in the breeder flock was subclinical, with no apparent effects on mortality or performance. A strategic program of therapeutic and/or prophylactic antibiotic therapy was begun in affected broiler flocks as soon as the disease was diagnosed. Nevertheless, when the cost of therapy was taken into account, affected broiler flocks had a net income 17.3% to 19.6% lower than normal flocks. Average bird weights were 3.3% to 3.5% lower in affected flocks than in unaffected flocks, and affected flocks had a significantly greater proportion of lighter birds. Average mortality in affected flocks was 2.0% to 2.3% higher than in normal flocks, with peak mortality occurring in the third week of life. There was no apparent effect on feed-conversion ratio.     

Monensin toxicity in turkey breeder hens

High mortality in two flocks of 1900 turkey breeder hens accidentally fed 280 g monensin/ton of complete feed is described. Mortality attributed to the poisoning was 76% in flock 1 and 18% in flock 2. Clinically, turkeys were found dead, exhibited respiratory distress with wings extended laterally, had fine tremors, or showed posterior paresis and inability to rise. The most striking finding at necropsy was the almost complete absence of gross lesions. Some turkeys had severely congested lungs; however, many did not. A few birds had pale streaks within the adductor muscles of the legs. Microscopic lesions included myofiber degeneration and necrosis of skeletal and myocardial muscle. Serum phosphorus, lactate dehydrogenase, and creatine phosphokinase were markedly elevated, whereas potassium, chloride, and calcium values were lowered.     

Campylobacter detection in commercial turkeys

1. Frequency of Campylobacter detection was monitored in three flocks of turkeys. The effect of week of production was evaluated for hens in flocks 1 and 2, and the effect of week, gender and litter (fresh or used) was assessed for flock 3. 2. Gastrointestinal tracts, poult box liners, drinkers and faecal droppings were sampled. Conventional microbiological procedures were used to isolate and identify the presence of Campylobacter. Campylobacter latex agglutination tests were used for confirmation. 3. Peak colonisation occurred at approximately 3 weeks of production. Frequency of Campylobacter isolation from bird sources paralleled isolation from waterers. Frequency of detection from birds placed on used litter was lower than detection from birds placed on fresh litter (2% vs 58%). Gender did not affect frequency of detection. 4. Minimising peak colonisation at 3 weeks and managing litter are opportunities to reduce the occurrence of this organism in turkeys.     

Relationships of Body Weight,Feathering, and Footpad Condition with Reproductive and Carcass Morphology of End-of-Season Commercial Broiler Breeder Hens

Reproductive efficiency of broiler breeder hens declines with age. Whereas careful feed management can maximize BW uniformity at housing, there is variability in how rate of lay and flock behavioral dynamics will interact with subsequent growth during the breeder phase. This study characterized differences in carcass and reproductive morphology in end-of-cycle commercial broiler breeder hens based on BW, feather coverage, and footpad condition, and we discuss the potential implications of the findings. At 62 wk of age, 537 hens were studied from an original flock of 3,800. Birds were sorted into subgroups based on BW, feather score, footpad score, and whether they were in laying condition when dissected. The average flock BW was 3.56 kg, with means of 2.86, 3.56, and 4.20 kg for the low (LOW), standard (STD), and high (HIGH) BW groups, respectively. A higher proportion of birds from the STD (85%) and HIGH (81%) groups still had a fully formed reproductive tract compared with birds of the LOW (59%) group. The LOW birds in laying condition had a smaller ovary than the STD or HIGH birds. The ovary condition of birds in laying condition was not related to feather coverage. As feather coverage improved, final hen BW increased, demonstrating a potential role of feather coverage in growth efficiency or of BW in level of mating activity. Birds that received a feather score of 5 (complete back feather coverage) and had a normal reproductive tract made up 14.7% of this flock. It is likely that many of these birds were mating very infrequently or possibly not mating, which has implications for maintenance of flock fertility. Some may also have been returning from a molt. Footpad condition was not related to body size. External traits such as BW, feather score, and footpad score can provide insight into flock reproductive condition and male:female interaction.     

The clinical course of the Infectious Laryngotracheitis (ILT) field case in hens and estimation of immunoprophylaxis efficiency

The ILT case was observed in laying hen farm where birds of different age (from 40 to 107 weeks) were kept in 10 flocks. A rapid spread of the disease, the decrease in egg production (in flock No. 1 it reached 58%) and higher mortality (the highest in 76 and 77 week-old birds, accounting for 0.11% and 0.36%, respectively ) was recorded during first 2 weeks of disease. Antibodies against ILT virus were detected in serum of the examined birds during the whole observation period (50 weeks after the disease outbreak). The laying hens were vaccinated at 8 weeks of age and boosted after 5 weeks. The vaccine was applied in drinking water, in a dose twice as high as usually recommended per one bird. Immunopropylaxis efficiency was estimated on the basis of immunological response in birds (serum samples, ILT ELISA kit, Guildhay Ltd.) and general health status of hens in flocks. Postvaccinal immunity, the presence of specific antibodies against ILT, was observed in all birds during the observation period (51 weeks). During that time GMT value ranged from 8261,3 (week 10) to 5196 (week 51) after the second vaccination, and CV amounted in this period to 41.1% and 51%, respectively. Subsequently, clinical symptoms of the disease disappeared and the egg production, as well as mortality, returned to the level of technological norms for laying hens.     

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.     

Infection dynamics of Ascaridia galli in non-caged laying hens

The infection dynamics of Ascaridia galli in laying hens was investigated in six commercial non-caged flocks. Three flocks were managed in accordance with the regulations for organic production and had outdoor access, whereas three flocks were housed indoors in aviaries or traditional floor systems. Faecal egg counts and total worm burdens were determined at specified intervals during the first 50 weeks of the production period. In two conventional flocks the efficacy of flubendazole on lumenal stages was investigated. All flocks became infected following the arrival of the birds (post placement) with residual infective eggs derived from the previous flock. In four flocks (two organic and two conventional) parasite eggs were first detected in faeces 6-7 weeks post placement, whereas parasite eggs were not detected until after 17-18 weeks in two flocks. This delay was observed in two of three flocks that were housed in barns that had been thoroughly cleaned and disinfected by chlorocresol. In three flocks (two conventional and one organic) flubendazole was administered to the birds in the drinking water for approximately one week. Both conventional flocks were dewormed twice approximately 20 weeks apart, whereas the organic flock was dewormed only once about 40 weeks post placement. Parasite eggs reappeared after deworming in all flocks, often within 2-4 weeks, followed by a rapid increase in parasite egg expulsion. Our results suggested impairment of host immunity post treatment, as the egg counts exceeded pre-treatment levels after 7-8 weeks on both conventional farms. Accordingly, the way by which anthelmintics and/or disinfectants are used in non-caged chicken flocks must be refined.     

Subclinical infectious bursal disease in commercial broiler flocks in Saskatchewan.

Five commercial broiler flocks, not vaccinated for infectious bursal disease virus, derived from infectious bursal disease virus-vaccinated breeder flocks were surveyed for evidence of bursal damage and infectious bursal disease virus infection. They were compared with two groups of birds raised in isolation. Serum samples from one day old chicks contained maternal anti-infectious bursal disease virus antibodies which declined to undetectable levels by four weeks of age. Serum antibody levels remained undetectable in both control groups and one commercial flock, whereas four of the five commercial flocks had actively produced anti-infectious bursal disease virus antibodies by slaughter age. The weight of bursae from infectious bursal disease virus-positive flocks declined as compared to controls after four weeks of age. The decline in weight correlated with the appearance of histopathological lesions. Infectious bursal disease virus antigen was demonstrated in selected infected bursae and infectious bursal disease bursae and infectious bursal disease virus was isolated from some of these damaged bursae. Clinical infectious bursal disease was not observed in any of the commercial flocks. The importance of subclinical bursal damage and immunosuppression is discussed.     

EDS 76 HI antibodies in a flock of free-range layers

An investigation of poor laying performance in a flock of free-range hens revealed high levels of serum antibodies to EDS 76 in the flock initially examined and in another, older flock on the same farm. These flocks had contact with ducks on a farm dam and were supplied with untreated drinking water from the dam. Serological evidence indicated that another flock supplying the same egg packing station had been infected with EDS 76 virus. Little serological evidence of EDS infection was detected from five other flocks supplying the packing station, parent breeders or the ducks resident on the dam. Therefore, the source of the EDS 76 virus remains conjectural.     

Salmonella enteritidis and other Salmonella in laying hens and eggs from flocks with Salmonella in their environment.

Seven Canadian layer flocks with Salmonella enteritidis in their environment were investigated to determine the numbers of hens infected with S. enteritidis, the localization of S. enteritidis in organs of infected hens and the numbers of S. enteritidis-infected eggs produced by two affected flocks. By a microagglutination test (MAT) using S. pullorum antigens, these flocks had more seropositive hens (mean 51.9 +/- 16.9%) than two Salmonella-free flocks (mean 13.0 +/- 4.2%). Culture of tissues of 580 hens (433 seropositive) from the seven flocks detected 26 (4.5%) S. enteritidis-infected hens from two flocks. In one flock, 2/150 hens were infected with S. enteritidis phage type (PT) 8, which was confined to the ceca, and no Salmonella spp. were isolated from 2520 eggs (one day's lay). In the second flock, where 24/150 hens were infected with S. enteritidis PT13, extraintestinal infection was found in nine hens and involved the ovaries and/or oviduct in two hens. Salmonella enteritidis PT13 was isolated from one sample of egg contents and from one sample of cracked shells from among 14,040 eggs (one day's lay) from this flock. The overall prevalence of S. enteritidis-contaminated eggs from the two flocks with infected hens was less than 0.06%. Other Salmonella spp. isolated were S. heidelberg from 58 hens (10%), and S. hadar, S. mbandaka and S. typhimurium from one hen (0.2%) each. The MAT with antigens of S. pullorum had a sensitivity of 81% and a specificity of 24% for detecting S. enteritidis-infected hens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genotyping Campylobacter jejuni strains isolated from the gut and oviduct of laying hens

Campylobacter jejuni frequently colonizes the avian intestine. Recent evidence suggests that this organism can also colonize the oviduct of laying hens. However, the source and role of this colonization are unknown. Isolates from the ceca, cloacae, and oviducts of 11 laying hens in three intensive egg-producing flocks were genotyped by Fla typing with the restriction fragment length polymorphism of the polymerase chain reaction product of the flaA and flaB genes (fla typing) and pulsed-field gel electrophoresis (PFGE). A diversity in fla types and PFGE types was observed within and between flocks. Individual birds could be colonized by different genotypes at various intestinal and oviduct sites. However, the oviduct of individual birds appeared to be colonized by only one genotype at the time of sampling. In two birds, matching isolates investigated from the intestinal and reproductive tracts were genotypically identical but different from those oviduct isolates found in other birds in the same flock. Interestingly, not all cecal isolates appeared to be equally able to colonize the oviduct. These results suggest that oviduct colonization may result from ascending infection via the cloaca and that some strains of C. jejuni may be better adapted than others to oviduct colonization.