Dietary potassium and available phosphorous on broiler growth performance, carcass characteristics, and wooden breast.

Broiler dietary potassium (K) and available phosphorous (AvP) have decreased in recent years but both ions are intimately involved in the elimination of hydrogen ions that are produced during rapid growth. It was hypothesized that the decrease of these dietary electrolytes was related to the development of myopathies, and thus increased dietary K and/or AvP would reduce the occurrence of breast myopathies. A total of 320 Ross male broiler chicks were placed into 16 pens and fed 2 diet series containing either decreasing AvP levels of 0.45, 0.40, and 0.35% in the starter, grower, and finisher diets, respectively (Decline), or a fixed AvP of 0.45% in all dietary phases (Fixed). To complete a 2 × 2 design either normal basal dietary K (K-) (0.86, 0.77, 0.68%) or added dietary K (K+) (1.01, 0.93, 0.88%) were also applied to starter, grower, and finisher diets, respectively. Blood physiology was measured at 29 and 42 d. Carcass data, wooden breast and white striping scores were measured at 35 and 43 d. The K+ diets improved feed conversion ratio at 35 d (1.52 vs 1.57 g: g), reduced body weight at 42 d (3524 vs 3584 g), reduced hemoglobin (6.83 vs 7.58 g/dL), and packed cell volume (20.1 vs 22.3%) at 29 d, reduced ionized blood calcium (1.42 vs 1.47 mmol/L) at 42 d, and reduced partial pressure of blood CO2 (49.1 vs 54.7 mm/Hg) at 42 d relative to broilers fed basal K- diets (P < 0.05). Fixed AvP diets improved feed conversion ratio at 28 and 42 d, increased percentage breast meat (28.85 vs 27.58%) and carcass water pickup (2.72 vs 1.42%) at 35 d, and reduced wooden breast (2.88 vs 3.69) at 43 d (P < 0.05).

White striping and wooden breast myopathies of broiler breast muscle is affected by time-limited feeding, genetic background, and egg storage.

The effects of time-limited feeding, genetic background, and egg storage on white striping (WS) and wooden breast (WB) in broilers were studied. Male chicks (240) from 2 genetic backgrounds and 2 egg storage periods were fed on either an ad libitum (AL) or time-limited (TL) program from 7 d of age. A rapid growth strain (Growth) and an enhanced yield strain (Yield) of broiler breeder males were mated to a single female line and eggs were stored for periods of either 1 to 7 d or 8 to 14 d. Body weight (BW), feed consumption, and feed conversion ratio (FCR) were determined weekly. Carcass data including WS and WB scores were collected at 42 d of age. Breast muscle scoring was conducted either visually or by hand palpation using a 1 to 4 point ordinal scale (normal to greatest severity). Data were analyzed using the Mixed procedure of SAS. The TL fed broilers presented less WS (1.64 vs. 2.87) and WB (2.14 vs. 2.89), lower BW (2.99 vs. 3.27 kg), and improved FCR (1.55 vs. 1.58 g: g), as well as reduced dressing percentage (79.5 vs. 80.1%), breast muscle yield (33.3 vs. 34.6%), and 24 h muscle pH (5.82 vs. 5.95) relative to AL broilers (P < 0.01). Yield broilers exhibited reduced BW (2.97 vs. 3.28 kg), lower WS (2.04 vs. 2.47), and greater WB (2.65 vs. 2.38) (P < 0.05) but similar dressing percentage (80.0 vs. 79.7%) and breast muscle yield (34.3 vs. 33.6%) when compared to Growth broilers. Longer egg storage generated lower BW (3.07 vs. 3.18 kg) and when fed AL, an increased WS score (2.58 vs. 3.15) compared to the shorter egg storage period (P < 0.05). It was concluded that WS and WB could be reduced by TL feeding and that genetic background and egg storage period may influence the expression of WS and WB.

Culture methods impact recovery of antibiotic-resistant Enterococci including Enterococcus cecorum from pre- and postharvest chicken.

Pathogenic strains of Enterococcus cecorum (EC) expressing multidrug resistance have emerged. In National Antimicrobial Resistance Monitoring System (NARMS) data, EC is rarely recovered from chickens. Two NARMS methodologies (FDA and USDA) were compared with standard culture (SC) techniques for recovery of EC. NARMS methods failed to detect EC in 58 caecal samples, 20 chicken breast or six whole broiler samples. EC was recovered from 1 of 38 (2·6%) and 2 of 38 (5·2%) preharvest spinal lesions (USDA and FDA method, respectively). In contrast, using the SC method, EC was recovered from 44 of 53 (83%) caecal samples, all 38 (100%) spinal lesions, 14 of 20 (70%) chicken breast samples, and all three spinal lesions identified in whole carcasses. Compared with other Enterococcus spp., EC isolates had a higher prevalence of resistance to macrolides. The NARMS methods significantly affected recovery of enterococcal species other than EC. When the postharvest FDA method was applied to preharvest caecal samples, isolates of Enterococcus faecium were preferentially recovered. All 11 E. faecium isolates were multidrug resistant, including resistance to penicillin, daptomycin and linezolid. These findings confirm that current methodologies may not accurately identify the amount and range of antimicrobial resistance of enterococci from chicken sources. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterococci are an important reservoir for antimicrobial resistance. This study demonstrates how current culture methods underreport resistance to macrolides in enterococci by selecting against strains of Enterococcus cecorum in pre- and postharvest chicken. Further, the application of postharvest surveillance methods to preharvest samples resulted in selective recovery of Enterococcus faecium over Enterococcus faecalis. Isolates of E. faecium recovered exhibited multidrug resistance including penicillin, daptomycin and linezolid resistance. These findings suggest that culture methodology significantly impacts the range and amount of antimicrobial resistance detected in enterococci isolated from chicken.

Pathogenesis of Enterococcal Spondylitis Caused by Enterococcus cecorum in Broiler Chickens.

Enterococcal spondylitis (ES) is a disease of commercial broiler chickens, with a worldwide distribution. Symmetrical hind limb paralysis typical of ES results from infection of the free thoracic vertebra (FTV) by pathogenic strains of Enterococcus cecorum . To determine the pathogenesis of ES, birds with natural and experimental ES were studied over time. In natural disease, case birds (n = 150) from an affected farm and control birds (n = 100) from an unaffected farm were evaluated at weeks 1-6. In control birds, intestinal colonization by E. cecorum began at week 3. In case birds, E. cecorum was detected in intestine and spleen at week 1, followed by infection of the FTV beginning at week 3. E. cecorum isolates recovered from intestine, spleen, and FTV of case birds had matching genotypes, confirming that intestinal colonization with pathogenic strains precedes bacteremia and infection of the FTV. Clinical intestinal disease was not required for E. cecorum bacteremia. In 1- to 3-week-old case birds, pathogenic E. cecorum was observed within osteochondrosis dissecans (OCD) lesions in the FTV. To determine whether OCD of the FTV was a risk factor for ES, 214 birds were orally infected with E. cecorum, and the FTV was evaluated histologically at weeks 1-7. Birds without cartilage clefts of OCD in the FTV did not develop ES; while birds with OCD scores ≥3 were susceptible to lesion development. These findings suggest that intestinal colonization, bacteremia, and OCD of the FTV in early life are crucial to the pathogenesis of ES.

Bilateral nocardial endophthalmitis in a prothonotary warbler (Protonotaria citrea).

A 7-year-old captive female prothonotary warbler (Protonotaria citrea) died following chronic feather and weight loss. At necropsy, the right eye had a 2 x 2 x 1 mm corneal plaque of inspissated yellow-tan material and edema of the lower eyelid. Microscopically, both eyes exhibited diffuse, severe pyogranulomatous endophthalmitis with retinal necrosis and detachment. Numerous intralesional branching, gram-positive, beaded, filamentous bacteria formed a thick mat attached to the retinal pigmented epithelium and extending into the pecten. Bacteria were strongly acid-fast positive by Fite's stain but only occasionally acid-fast positive by Ziehl-Neelsen staining, a characteristic consistent with a Nocardia spp. Infected regions demonstrated positive in situ hybridization reactivity with a probe complementary to the 16S rRNA gene of Nocardia spp. There was no evidence of primary bacterial infection in the other organs examined.

Experimental infection of chickens and turkeys with Mycoplasma gallisepticum reference strain S6 and North Carolina field isolate RAPD type B.

During an epidemic of mycoplasmosis in chicken and turkey flocks in North Carolina between 1999 and 2001, isolates of Mycoplasma gallisepticum (MG) from affected flocks were characterized by random amplification of polymorphic DNA (RAPD), and eight distinct RAPD types were identified. MG RAPD type B accounted for more than 90% of the isolates and was associated with moderate-to-severe clinical signs and mortality. The virulence of MG RAPD type B for chickens and turkeys was compared with sham-inoculated negative controls and MG S6 (a virulent strain)-inoculated positive controls. Clinical signs occurred in chickens and turkeys inoculated with either MG RAPD type B or MG S6. However, they were not as frequent or severe as those seen in naturally affected flocks, and there was no mortality in the experimental groups. Based on gross and microscopic findings, MG RAPD type B was equal to or more virulent than MG S6. All MG-inoculated birds were culture and PCR positive at 7 and 14 days postinoculation (PI). Among serological tests, the serum plate agglutination test was positive for the majority of chickens and turkeys (58%-100%) infected with either strain of MG at both 7 and 14 days PI. The hemagglutination inhibition test was negative for all birds at 7 days PI and positive for a few chickens (8%-17%) and several turkey sera (40%-60%) at 14 days PI. Only a single serum was positive by enzyme-linked immunosorbent assay (an MG S6-infected turkey) at 14 days PI.

Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection.

In a previous study, turkey coronavirus (TCV) and enteropathogenic Escherichia coli (EPEC) were shown to synergistically interact in young turkeys coinfected with these agents. In that study, inapparent or mild disease was observed in turkeys inoculated with only TCV or EPEC, whereas severe growth depression and high mortality were observed in dually inoculated turkeys. The purpose of the present study was to further evaluate the pathogenesis of combined TCV/EPEC infection in young turkeys and determine the role of these agents in the observed synergistic interaction. Experiments were conducted to determine 1) effect of EPEC dose, with and without concurrent TCV infection, and 2) effect of TCV exposure, before and after EPEC exposure, on development of clinical disease. Additionally, the effect of combined infection on TCV and EPEC shedding was determined. No clinical sign of disease and no attaching and effacing (AE) lesions characteristic of EPEC were observed in turkeys inoculated with only EPEC isolate R98/5, even when turkeys were inoculated with 10(10) colony forming units (CFU) EPEC (high dose exposure). Only mild growth depression was observed in turkeys inoculated with only TCV; however, turkeys inoculated with both TCV and 10(4) CFU EPEC (low dose exposure) developed severe disease characterized by high mortality, marked growth depression, and AE lesions. Inoculation of turkeys with TCV 7 days prior to EPEC inoculation produced more severe disease (numerically greater mortality, significantly lower survival probability [P < 0.05], increased frequency of AE lesions) than that observed in turkeys inoculated with EPEC prior to TCV or simultaneously inoculated with these agents. Coinfection of turkeys with TCV and EPEC resulted in significantly increased (P < 0.05) shedding of EPEC, but not TCV, in intestinal contents of turkeys. These findings indicate that TCV infection predisposes young turkeys to secondary EPEC infection and potentiates the expression of EPEC pathogenicity in young turkeys.

Prevalence of enteropathogenic Escherichia coli in naturally occurring cases of poult enteritis-mortality syndrome.

Enteropathogenic Escherichia coli (EPEC) previously were identified in poult enteritis-mortality syndrome (PEMS)-affected turkeys and associated as a cause of this disease. In the present study, the prevalence of EPEC in PEMS-affected turkeys was examined retrospectively with archived tissues and intestinal contents collected from 12 PEMS-affected turkey flocks in 1998. Formalin-fixed intestinal tissues were examined by light and electron microscopy for attaching and effacing (AE) lesions characteristic of EPEC, and frozen (-75 C) intestinal contents were examined for presence of EPEC. Escherichia coli isolates were characterized on the basis of epithelial cell attachment, fluorescent actin staining (FAS) test, and presence of E. coli attaching/effacing (EAE), shigalike toxin (SLT) type I, SLT II, and bundle-forming pilus (BFP) genes by polymerase chain reaction procedures. EPEC isolates were examined for pathogenicity and ability to induce AE lesions in experimentally inoculated young turkeys. AE lesions were identified by light microscopy in Giemsa-stained intestines from 7 of 12 PEMS-affected turkey flocks. Lesions consisted of bacterial microcolonies attached to epithelial surfaces with epithelial degeneration at sites of attachment and inflammatory infiltration of the lamina propria. Electron microscopy confirmed the identity of AE lesions in six of seven flocks determined to have AE lesions by light microscopy. EPEC were identified in 4 of 12 flocks on the basis of the presence of EAE genes a nd absence of SLT I and SLT II genes; all isolates lacked BFP genes. EPEC isolates produced AE lesions and variable mortality in turkeys coinfected with turkey coronavirus. In total, EPEC were associated with 10 of 12 (83%) naturally occurring PEMS cases on the basis of identification of AE lesions and/or EPEC isolates. These findings provide additional evidence suggesting a possible role for EPEC in the pathogenesis of PEMS.

Hatchery and transportation factors associated with early poult mortality in commercial turkey flocks.

A prospective ecologic study, using routinely collected data from commercial turkey companies, was done of 312 turkey flocks placed over a 1-yr period. The objective was to identify hatchery- and transportation-associated risk factors for poult mortality in the first 14 d after placement using statistical models. Logistic regression was used to determine the effects of hatchery-and transportation-related factors on odds of mortality for hen and tom flocks separately. Hatchery and transportation-related risk factors for hen flock mortality included truck, truck temperature, and number of poults dead on arrival at the farm. Hatchery and transportation-related risk factors for tom flock mortality included desnooding, truck, truck temperature, shipping time, and weather conditions at placement.

Mortality patterns associated with poult enteritis mortality syndrome (PEMS) and coronaviral enteritis in turkey flocks raised in PEMS-affected regions.

Poult enteritis mortality syndrome (PEMS) is an economically devastating disease. To date, many questions about the syndrome remain unanswered, including its cause, transmission of causative agent(s), and control methods. Turkey coronavirus (TCV) infection has been associated with some outbreaks of PEMS, with areas having a higher prevalence of TCV infection also experiencing an increased incidence of PEMS. This study was designed to establish mortality patterns for flocks experiencing excess mortality and TCV infection in PEMS-affected regions and to delineate the possible role of TCV in PEMS-affected flocks. Fifty-four commercial turkey flocks on farms in areas with and without a history of TCV infection were monitored for weekly mortality and for antibodies to TCV. Flocks were chosen on the basis of placement dates and were monitored from day of placement until processing. All flocks were tested for TCV by an indirect fluorescent antibody assay. PEMS status was determined with the use of the clinical definition of mortality greater than 2% during any 3-wk period from 2 wk of age through the end of brooding due to unknown cause. Of the 54 flocks, 24 remained healthy, 23 experienced PEMS, and 7 tested positive for TCV but did not experience PEMS. Ten flocks experienced PEMS and tested positive for TCV, whereas 13 flocks experienced PEMS and did not test positive for TCV. Four health status groups were evident: healthy, PEMS positive, TCV positive, and PEMS + TCV positive. Distinct mortality patterns were seen for each of the four health status groups. Whereas TCV was associated with PEMS in 43% of PEMS cases, 13 cases (57%) of PEMS did not involve TCV. Additionally, 7 out of 17 cases of TCV (41%) did not experience excess mortality (PEMS) at any time during brooding of the flock. The results of this study indicate that TCV can be associated with PEMS but is neither necessary nor sufficient to cause PEMS.

Comparison of virus isolation, immunohistochemistry, and reverse transcriptase-polymerase chain reaction procedures for detection of turkey coronavirus.

A reverse transcriptase-polymerase chain reaction (RT-PCR) procedure and two monoclonal antibody (MAb)-based immunohistochemical procedures were developed for detection of turkey coronavirus (TCV) in tissues and intestinal contents/dropping samples. The RT-PCR, MAb-based fluorescent antibody (FA), and MAb-based immunoperoxidase (IP) procedures were compared with virus isolation (VI) for detection of TCV in experimentally infected turkeys. TCV was detected in experimentally infected turkeys as early as day 1 postexposure (PE) by each of the four detection procedures. TCV was detected as late as day 35 PE by FA or IP and days 42 and 49 PE by VI and RT-PCR, respectively. With VI as a reference, sensitivity and specificity of RT-PCR were 93% and 92%, respectively; specificity of both FA and IP was 96%, and sensitivities were 69% and 61%, respectively. Each of the examined procedures was highly specific, but the RT-PCR procedure was also highly sensitive. These findings demonstrate the utility of both immunohistochemistry and RT-PCR for detection of TCV. In addition, the findings indicate that RT-PCR is a highly sensitive and specific alternative to conventional diagnostic procedures.

Poult enteritis complex.

Poult enteritis complex (PEC) is a general term that encompasses the infectious intestinal diseases of young turkeys. Some diseases, such as coronaviral enteritis and stunting syndrome, are relatively well characterised, while others, such as transmissible viral enteritis, poult growth depression and poult enteritis mortality syndrome, remain ill-defined. All forms of PEC are multifactorial, transmissible and infectious. Salient clinical features include stunting and poor feed utilisation that result from enteritis. In the more severe forms, runting, immune dysfunction and mortality are reported. Gross and microscopic lesions of enteritis are present in all forms but tend to be non-specific. Other lesions may be present, depending on the agents involved. The basic pathogenesis involves the following: a) alteration of the intestinal mucosa, generally by one or more viruses infecting enterocytes; b) inflammation; c) proliferation of secondary agents, usually bacteria. Non-infectious factors interplay with infectious agents to modulate the course and severity of disease. Diarrhoea is believed to be primarily osmotic because of maldigestion and malabsorption, but may also have a secretory component. Transmission is primarily faecal-oral. No public health significance is recognised or suspected. Prevention is based on eliminating the infectious agents from contaminated premises and preventing introduction into flocks. This is accomplished by an effective cleaning, disinfection and biosecurity programme. All-in/all-out production or separate brooding and finishing units are helpful. Control may require regional co-ordination among all companies producing turkeys, especially if the production is highly concentrated, and a quarantine programme for more severe forms of PEC. No vaccines or specific measures for controlling the organisms involved in PEC are available. Treatment is supportive for the viral component, while antibiotics, especially those with efficacy against Gram positive bacteria, may help to reduce the impact to bacterial infections. Evidence suggests that PEC occurs wherever turkeys are raised commercially, but this is not well documented and distribution of the various organisms that have been associated with PEC is largely unknown. The disease causes enormous economic loss, mostly from failure of the turkey to reach its genetic potential.

Identifying agent(s) associated with poult enteritis mortality syndrome: importance of the thymus.

Poult enteritis mortality syndrome (PEMS), a highly infectious disease of young turkeys, causes serious financial losses to the turkey industry. Clinically, PEMS is defined by mortality profiles, diarrhea, growth depression, and immunosuppression. Although many viruses, bacteria, and parasites are found in PEMS-infected birds, the inciting agent remains unknown. Experimentally, PEMS can be reproduced by exposing naïve poults to the intestinal contents from infected birds. Previous reports suggest that extraintestinal tissues fail to reproduce the disease. Histopathologic examination of tissues from PEMS-infected poults suggested that the thymus exhibited the earliest signs of pathology. On the basis of these observations, we hypothesized that the thymus harbors an agent(s) involved in PEMS. In these studies, naïve turkey poults were orally inoculated with a bacteria-free filtrate composed of either the intestines and feces or the thymus from PEMS-infected birds and were monitored for clinical signs of PEMS. Poults exposed to a filtrate composed solely of the thymus from PEMS-infected birds exhibited diarrhea, growth depression, mortality, pathology, and, most importantly, immunosuppression similar to poults exposed to the intestinal filtrate. The results of this study suggest that the thymus of infected birds harbors the agent(s) that can reproduce a PEMS-like disease in turkey poults.

Viral agents associated with poult enteritis and mortality syndrome: the role of a small round virus and a turkey coronavirus.

Intestinal samples from turkey poults affected with poult enteritis and mortality syndrome (PEMS) were examined for viruses by immune electron microscopy and double-stranded RNA virus genome electropherotyping. Turkey coronavirus (TCV), avian rotaviruses, reovirus, and a yet undefined small round virus (SRV) were detected. The SRV and TCV were isolated and propagated in turkey embryos. Challenge of specific-pathogen-free turkey poults with SRV, TCV, or both resulted in mortality and clinical responses similar to those of natural PEMS. Our experiments indicate that SRV and TCV are possibly important agents in the etiology of PEMS and the combination of these infections might result in outbreaks with high mortality. The severity of clinical signs and mortality of PEMS are postulated to be partly related to the virus agents involved in individual outbreaks.

Alterations in macrophage-produced cytokines and nitrite associated with poult enteritis and mortality syndrome.

Poult enteritis and mortality syndrome (PEMS) is an acute, transmissible, infectious intestinal disease associated with high mortality and morbidity in turkey poults. Earlier studies demonstrated immune dysfunction, involving both humoral and cell-mediated immunity, associated with PEMS. The current study examined cytokines and metabolites produced by macrophages from poults exposed to PEMS agent(s). Six trials were conducted with six separate hatches of poults. Poults in the PEMS group were exposed to PEMS agent(s) via contact exposure at 7 days of age whereas uninfected poults served as control poults. Abdominal macrophages were harvested from control (uninfected) and PEMS poults at various times postexposure and cultured for 18-24 hr in the presence of Escherichia coli lipopolysaccharide. Interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) bioactivities and nitrite levels in macrophage culture supernatants were quantified. Macrophage supernatants from PEMS poults had greater IL-1-mediated stimulation index compared with the macrophage supernatants from uninfected control poults in both trials. However, this increase was significant only in trial 1. IL-6 activity tested in three separate trials was significantly higher in PEMS macrophage supernatants over the controls. On the contrary, TNF-alpha production by macrophages was decreased in PEMS macrophage culture supernatants. Nitrite levels in PEMS macrophage culture supernatants were significantly higher in two out of three trials. These findings suggest that the enhanced production of proinflammatory cytokine/metabolites by activated macrophages in PEMS poults may be responsible, at least in part, for the physiological intestinal inflammation, gut motility, and anorexia that characterize this disease.

High mortality and growth depression experimentally produced in young turkeys by dual infection with enteropathogenic Escherichia coli and turkey coronavirus.

Six-day-old turkeys were inoculated with turkey coronavirus (TCV) and an enteropathogenic Escherichia coli (EPEC) (isolate R98/5) that were isolated from poult enteritis and mortality syndrome (PEMS)-affected turkeys. Turkeys inoculated with only R98/5 did not develop clinically apparent disease, and only mild disease and moderate growth depression were observed in turkeys inoculated with only TCV. Turkeys dually inoculated with TCV and R98/5 developed severe enteritis with high mortality (38/48, 79%) and marked growth depression. R98/5 infection resulted in attaching/effacing (AE) intestinal lesions characteristic of EPEC: adherence of bacterial microcolonies to intestinal epithelium with degeneration and necrosis of epithelium at sites of bacterial attachment. AE lesions were more extensive and were detected for a prolonged duration in dually inoculated turkeys compared with turkeys inoculated with only R98/5. An apparent synergistic effect in dually inoculated turkeys was indicated by increased mortality, enhanced growth depression, and enhanced AE lesion development. The results suggest that TCV promoted intestinal colonization by R98/5; however, R98/5 did not appear to alter TCV infection. The present study provides a possible etiologic explanation for PEMS.

Bordetella avium virulence measured in vivo and in vitro.

Bordetella avium causes an upper-respiratory-tract disease called bordetellosis in birds. Bordetellosis shares many of the clinical and histopathological features of disease caused in mammals by Bordetella pertussis and Bordetella bronchiseptica. In this study we determined several parameters of infection in the domestic turkey, Meleagris galapavo, and compared these in vivo findings with an in vitro measure of adherence using turkey tracheal rings. In the in vivo experiments, we determined the effects of age, group size, infection duration, and interindividual spread of B. avium. Also, the effect of host genetic background on susceptibility was tested in the five major commercial turkey lines by infecting each with the parental B. avium strain and three B. avium insertion mutants. The mutant strains lacked either motility, the ability to agglutinate guinea pig erythrocytes, or the ability to produce dermonecrotic toxin. The susceptibilities of 1-day-old and 1-week-old turkeys to B. avium were the same, and challenge group size (5, 8, or 10 birds) had no effect upon the 50% infectious dose. Two weeks between inoculation and tracheal culture was optimal, since an avirulent mutant (unable to produce dermonecrotic toxin) persisted for a shorter time. Communicability of the B. avium parental strain between confined birds was modest, but a nonmotile mutant was less able to spread between birds. There were no host-associated differences in susceptibility to the parental strain and the three B. avium mutant strains just mentioned: in all turkey lines tested, the dermonecrotic toxin- and hemagglutination-negative mutants were avirulent whereas the nonmotile mutants showed no loss of virulence. Interestingly, the ability of a strain to cause disease in vivo correlated completely with its ability to adhere to ciliated tracheal cells in vitro.

Intervention decision model to prevent spiking mortality of turkeys.

Based on the daily records on turkeys' mortalities for the series of flocks placed on different farms in a relatively compact geographical area for the period of approximately 2 yr and other relevant explanatory variables, the goal of the research was to design a decision model to determine whether or not to use the fluorquinolone antibiotic, sarafloxacin, to prevent spiking mortality of turkeys. The core of the designed decision model is the forecasting model that attempts to ex-ante predict the cumulative flock mortality for the period between 8 and 28 d of age. Forecasts were generated with the parameters of the linear regression model where continuous values of daily mortalities served as a dependent variable. The decision variable is a binary (yes/no) choice variable, where "yes" means "go ahead with treatment" and "no" means "do nothing". If the predicted cumulative mortality for the period between 8 and 28 d of age exceeds 9% of the total initial placement, the model generates a "yes" signal. If the predicted cumulative mortality for the same period is below 9% of the total initial placement, the model generates a "no" signal. The results indicate a reasonable accuracy of the prediction model where the number of correct prediction increases and the number of incorrect predictions falls very fast as the forecasting window shortens. The intervention decision model could help veterinarians in making decisions on whether or not to treat the suspect flocks.

Regulation of CCSP (PCB-BP/uteroglobin) expression in primary cultures of lung cells: involvement of C/EBP.

The Clara-cell secretory protein (CCSP) is a cell-specific differentiation marker for the bronchiolar Clara cell. Isolated rat Clara and alveolar type 2 cells kept in primary culture proliferate and dedifferentiate, providing the opportunity to study differentiation-dependent mechanisms. In freshly isolated Clara cells, high levels of CCSP and the corresponding mRNA were detected. During culture in vitro, these levels decreased. In the type 2 cell fraction, low levels of CCSP were detected, which decreased further during culture. A promoter fragment of the rat CCSP gene encompassing the sequence from -188 to +53 was able to drive high-level expression of reporter genes in transfected Clara cells. Reporter gene expression in transfected type 2 cells was markedly lower, and no expression could be detected in alveolar macrophages. Expression of transcription factors previously described to stimulate CCSP expression appeared not to parallel CCSP levels in the primary Clara cells. However, expression of the transcription factor C/EBP alpha correlated with the CCSP expression pattern. In electrophoretic mobility shift assays, we were able to demonstrate binding of C/EBP alpha from rat Clara cell nuclear extracts to an element located 85 bp upstream of the start site of transcription. Overexpression of C/EBP alpha increased expression from the CCSP -188 promoter fragment up to fivefold in NCI-H441-cells and 30-fold in A549-cells, establishing the functional importance of C/EBP alpha. Our results show that primary cultures of Clara cells constitute a useful model for investigating terminal airway differentiation and suggest a role for C/EBP-factor(s) in this process.

Axillary cystadenocarcinoma in a Moluccan cockatoo (Cacatua moluccensis).

An adult Moluccan cockatoo (Cacatua moluccensis) was diagnosed with a cystadenocarcinoma in the right axillary region that was treated symptomatically with surgical debulking and periodic drainage. The bird eventually died and a necropsy was performed. The neoplasm extended through the humerus, and small neoplastic foci were seen within the ipsilateral lung parenchyma. Rare groupings of microvilli were observed lining intercellular canalicular lumens on electron microscopy within the axillary tumor. These findings suggest a respiratory neoplasm, although the tissue of origin remained undetermined.