Epidemiological and clinical investigations into big liver and spleen disease of broiler breeder hens

SUMMARY The epidemiological and clinical features of big liver and spleen disease (BLS) in flocks on two broiler breeder farms were investigated by serology and gross pathology. The most common necropsy findings on farm 1 were splenomegaly and hepatomegaly, with kidney enlargement in some birds. In one flock (farm 1), a decline in egg production began at 40 weeks of age and lasted for 9 weeks. Seroconversion to BLS antigen was first detected at 45 weeks (3.1% of birds) and increased to 72% at 50 weeks, which coincided with clinical recovery in the flock. Antigen was detected before antibody at 44 weeks and persisted at low incidence (<15%). Farm egg production statistics and serology indicated that the disease affected all flocks on the farm. In three of eight flocks, seroconversion was detected in birds before peak production. The birds in the remaining sheds did not seroconvert or become sick until after peak production. On the second farm, sampling began within a flock already experiencing BLS. Clinical signs and pathology were similar to those seen in flocks on farm 1. However, the lesions that were seen in the pancreas in 15% of birds have not been reported previously. BLS antibody was detected in 78%, and circulating antigen in 14%, of sick birds.     

A study of the epidemiology of infectious bursal disease in poultry in Queensland, 1976–1979

The epidemiology of infectious bursal disease (IBD) was studied by serology and sometimes by visual examination of the bursa of Fabricius in poultry flocks in Queensland during 1976–1979.
Ten flocks, each of approximately 30,000 meat breeding chickens, were surveyed. All chickens had maternally-derived antibody against IBD virus (IBDV) at hatching and active antibody was not detected while the chickens were brooded on rearing farms. When distributed to breeding farms, 7 of the flocks developed antibody when 11 to 25 weeks of age. The remaining 3 flocks were vaccinated by infection of 10% of the birds and within 4 weeks more than 80% of the chickens had developed precipitating antibody to IBDV.
Blood samples of 20 to 30 broiler chickens were collected at slaughter (7 to 9 weeks of age) from each of 312 broiler flocks raised on 37 contract farms. While the samples from 21 flocks were without detectable antibody to IBDV, all serum samples for 263 flocks contained antibody. The ratio of bursal weight to bodyweight was significantly lower in birds from 144 flocks having antibody to IBDV than in birds from 10 flocks that were without detectable antibody. In sequential studies, IBDV antibody became demonstrable in 27 of 30 flocks when the chickens were one to 6 weeks of age and was accompanied by bursal atrophy.
Serological investigation of 4 flocks of layer breeding chickens on a multi-age farm at approximately monthly intervals resulted in antibody to IBDV being detected at every examination.
Serological tests and bursal examinations were carried out weekly in 2 flocks each of 4000 layer chickens between one and 20 weeks of age. Serum antibody developed in one flock at 4 weeks of age and in the other at 17 weeks of age. In both flocks, bursal atrophy occurred concurrently with the development of antibody.     

Campylobacter spp. in conventional broiler flocks in Northern Ireland: epidemiology and risk factors

Risk factors for Campylobacter infection in conventional broiler flocks in the time period up to the first removal of birds to slaughter were investigated over a maximum of five consecutive production cycles in a cohort of 88 broiler farms in Northern Ireland. Samples for Campylobacter culture, which consisted of 14 cloacal swabs per flock, were collected from one house on each farm prior to the first depopulation of birds. In total 388 flocks were sampled, of which 163 tested positive for Campylobacter spp. (42.0%; 95% CI 35.1–48.9%).

Data on farm and flock variables were obtained from questionnaires and random-effects logistic regression modelling used to investigate the association between these and the Campylobacter status of flocks. Six variables, all of which were significant at p < 0.05, were included in the final multivariable model. These included a combined variable on the presence of rodents on farms, which showed an increased odds of infection in flocks where the farmer reported having observed rodents during the production cycle (OR = 2.1) and/or where rodent droppings were observed at the sampling visit (OR = 2.9). Other variables that were significantly associated with an increased odds of infection included the age of the birds at sampling (odds ratio for its linear effect = 1.16 for each day of increase in age), season (summer versus other seasons OR = 2.0), farms with three or more broiler houses (OR = 2.9 compared to those with one house), the frequency of footbath disinfectant changes (OR = 2.5 for once weekly and OR = 4.0 for less than once weekly compared to twice weekly changes) and a categorical variable on the standard of tidiness and cleanliness of the broiler house ante-room (OR = 2.0 and OR = 4.9 for flocks from houses with poorer standards). There was no significant evidence of direct carry-over of infection from one production cycle to the next, neither was there evidence of other farm species acting as a source of infection.     

Infectious stunting and pancreatic fibrosis in broiler chickens in Saskatchewan

Two broiler flocks contained 0.5 and 3% small chickens. The small chickens were approximately one-third the size of their penmates, were very active, and retained much of their chick down. They had distended abdomens with full intestinal tracts, often containing undigested feed. In many, the pancreases were thin, white, and firm because of loss of exocrine tissue and replacement by fibrous tissue. Many had skeletal changes suggestive of rickets. In a survey of 48 broiler flocks for small birds and pancreatic lesions, five flocks had a noticeable incidence of small chickens, varying from less than 1% to a maximum of 2%. In 33 of the flocks surveyed, a low incidence of pancreatic lesions was found in birds at the processing plant. No correlation was found between a noticeable number of small birds at the farm and pancreatic lesions found at processing.     

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.     

Experimental reproduction of enterococcal spondylitis in male broiler breeder chickens

There has been a recent emergence of epidemic spinal infections with necrosis causing lameness and mortality in male broilers and broiler breeders. Mortality in affected flocks may be as high as 15%. The disease has been called enterococcal spondylitis (ES), based on the frequent isolation of Enterococcus cecorum from the lesions and necrosis and inflammation observed in the free thoracic vertebrae (FTV) of affected birds. Male broiler breeders in an experimental setting were challenged with pure E. cecorum isolates obtained from ES-affected commercial flocks. Challenge routes included oral gavage (10(8)), intravenous (i.v.; 10(3)), and air sac (AS; 10(3)). Half the study birds in each group were chemically immunosuppressed with dexamethasone. Spinal lesions were observed grossly in birds challenged intravenously (2.9%) and birds challenged orally (6.1%). Microscopic spinal lesions consistent with ES were more frequently identified compared with gross lesions in the orally challenged group (30.3%). Chemical immunosuppression with dexamethasone was not associated with a greater incidence of ES in this study. By recreating the disease experimentally, the study design reported here may help in the further development of an experimental challenge model for future studies on risk factors, prevention, and therapeutic intervention of ES.     

Swollen head syndrome: clinical observations and serological examinations in West Germany

Swollen Head Syndrome (SHS) affects both broiler and broiler breeders and has become a problem in many countries. Clinical signs similar to those described in SHS conditions have been observed in northern Germany with the disease observed mostly in chicken broilers between 4 and 5 weeks of age and in broiler breeders between 24 and 36 weeks of age. The mortality rate in broilers has been variable from negligible to 5%. In broiler breeders, the symptoms were accompanied with a drop in egg production reaching 2-3% after 1 to 2 weeks. 422 Serum samples from 21 broiler flocks were examined for the presence of antibodies to TRT-virus using indirect ELISA tests. Antibodies were detected in 2 flocks which suffered from SHS, but not in 2 flocks showing respiratory manifestations nor in 17 apparently healthy flocks. The results obtained from testing 178 serum samples from 10 breeder flocks revealed that antibodies to TRT-virus were present in one flock with SHS signs as well as in 6 apparently healthy flocks. In addition, no antibodies were found in sera collected from 3 flocks--one with SHS and respiratory disease history; one recovered from respiratory infection and one without disease history. Examination of paired serum samples from 3 breeder flocks that suffered from typical SHS-signs collected at the onset of the disease and during the convalescent stage, as well as sera from one broiler and one breeder flocks that showed respiratory manifestations, showed that there are significant increases in the number of positive sera in the flocks with SHS symptoms. The other flocks remained free from TRT antibodies.     

Association of Enterococcus cecorum with vertebral osteomyelitis and spondylolisthesis in broiler parent chicks

Enterococcus cecorum is the most frequently occurring enterococcal species in the intestine of chickens of over 12 weeks of age, and there are few reports on its isolation from the skeleton of broiler parent chicks. In the present study, observations on vertebral osteomyelitis and spondylolisthesis ('kinky back syndrome') showing high incidence in 8 broiler parent flocks in different parts of Hungary are summarised. Clinical signs were seen only in roosters between 5 and 13 weeks of age. Diseased birds were alert and remained sitting on their hocks with their feet slightly raised off the ground. Incidence of the disease among male birds ranged from 8% to 30% depending on flocks. Enlargement and distortion of the body of the 6th vertebra were seen as the main pathological lesions. The cavity of the spinal canal was constricted by the distorted vertebral bodies. Resorption of bone tissue and sequestrum formation, signs of increased osteoclast activity, proliferation of fibrotic tissues, infiltration with heterophils and formation of sclerotic layers were detected in the vertebral bodies. From all 24 samples collected from the vertebral lesions, Enterococcus cecorum was isolated and identified using metabolic fingerprinting as well as 16S rRNA gene sequencing. Demonstration of E. cecorum from the vertebral lesions in all examined broiler breeder roosters showing the same clinical and pathological findings in different flocks suggested the pathogenic role of this microorganism for the first time in Hungary.     

肉仔鸡腿病病因研究报告

1498只出壳A.A.肉仔鸡在同一房宿内分五区网上养育,分别为301,301,297,298和301只。10日龄雏鸡出现腿异常,46日龄腿病死淘鸡总数为248只,占入舍鸡数的16.6％。一经发现病鸡就拣出隔网分开饲养,腿病鸡群称为病鸡组,正常鸡群称为健康组。对不同日龄鸡做病毒性关节炎、滑液囊霉形体、葡萄球菌和大肠杆菌的血清学检查或细菌培养,结果都判定为阴性。从49日龄病鸡组和健康组分别随机抽取15只鸡,分离血清,检测血清总蛋白、碱性磷酸酶、钙、磷和血脂三项,并测定羽毛锰和锌等矿物元素,这些指标在两组之间都呈差异不显著水平(P>0.05)。结合临床剖检结果,认为病鸡没有发生骨质明显病理过程。应用剩余法分析阐明,垫网是这次肉仔鸡腿病的直接病因。连续不间断地光照亦可能与腿病相关。     

Sources of Salmonellae in broiler chickens in Ontario.

Sources of Salmonellae infecting broiler chicken flocks in Ontario were investigated from July, 1975 to April, 1976. Three broiler flocks were investigated on each of four farms which received chicks from a common hatchery. Samples of feed and new litter were preenriched in nonselective broth subcultured to Salmonella-selective enrichment broth and plated on Salmonella-selective differential agar.Samples of used litter, water, culled chicks, insects, mice, wild birds and environmental swabs were not cultured initially in the nonselective broth. Fecal samples from principal and occasional flock attendants were examined for Samonellae. Salmonella infection, as judged by contaminated flock litter was detected in six flocks on two of the farms while the flocks on the other farms remained negative. Salmonellae were isolated from 23 of 412 feed samples (nine serotypes), six of 35 new wood shaving samples (four serotypes), one of 29 pools of culled chick viscera (one serotype) and 44 of 267 used litter samples (14 serotypes). These results indicate that broiler chicken flocks were infected with diverse Salmonellae introduced in day old chicks, pelleted feeds, wood shavings and residual contamination from the preceding flock.     

Fowl cholera in broilers

Pasteurella multocida, the etiologic agent of fowl cholera, was isolated from six broiler flocks in Georgia during summer 1988. The flocks ranged in age from 20 to 46 days, represented four companies, and spanned a distance of 50 miles. Increased mortality and lameness were the clinical signs present in all affected flocks. Bacterial isolation and agar gel precipitation for somatic antigen serotyping revealed that three of the cases were caused by serotype 1,3, two by serotype 3,4, and one by serotype 3. To prove the virulence of these organisms, two isolates were selected to challenge 5-week-old broilers. Mortality and lameness resulted from this challenge, and P. multocida was reisolated.     

Campylobacter spp. in broiler flocks at farm level and the potential for cross-contamination during slaughter

Screening of broiler flocks for their Campylobacter carriage on farm level and consequently the spread of Campylobacter spp. during slaughtering can help to identify hygiene control points. Therefore, between December 2001 and August 2002 in total 51 broiler flocks from three farms of different geographical regions in Germany were analysed for thermophilic Campylobacter. Campylobacter spp. were isolated from 45% of the broiler flocks examined. Subsequently, 1101 samples were taken from 22 flocks during different stages of processing. Samples were collected from: transport crates before and after cleaning/disinfection, evisceration, post-scalded and post-chilled carcasses and endproducts. Additionally, 45 selected Campylobacter isolates of droppings were genotyped by pulsed-field gel electrophoresis (PFGE). Campylobacter carriage of flocks showed seasonal variation, with the highest contamination rate during the period of June to August. No evidence was found for a horizontal transmission from one broiler flock to the next via a persistent house-contamination. In each positive flock, one to three different genotypes were found. One or two clones dominated isolations obtained from the farm level. The fact that in different flocks indistinguishable isolates of clonal origin were detected during the same rearing period suggested a transmission between the broiler flocks or an intermittent common external source. In one case, isolates of clonal origin were detected in various farms during different rearing periods. Sampling during processing confirmed that the entrance of a positive flock resulted in contamination of the abattoir environment. Campylobacter spp. were isolated from all sampling stages along the processing line, with a percentage of 91.1-100 of isolates at different stages of slaughtering.     

Risk Factors Associated with Salmonella Status of Broiler Flocks Delivered to Grow‐Out Farms

In a prospective field observational study in the southeastern USA, we sampled gastrointestinal (GI) tracts from chicks of 65 broiler flocks delivered to conventional grow‐out farms for rearing. The flocks were hatched at seven broiler hatcheries. The mean within‐flock prevalence of Salmonella‐positive samples was 6.5% and ranged from 0% to 86.7%. Of the 65 flocks studied, 25 (38.5%) had at least one Salmonella‐positive sample. Accounting for confounding variability among the hatcheries and broiler companies, we tested whether the probability of detecting Salmonella in GI tracts of the chicks delivered was associated with certain characteristics of parent breeder flocks; hatchery production volume; hatchery ventilation system; hatchery egg‐room conditions; egg incubation, candling, hatching, eggshell and bird separation, and bird‐processing procedures; management of hatchery‐to‐farm transportation; day of week of hatch; weather conditions during transportation; or season of the hatch. Two risk factor models were adopted. The first model indicated that a greater number of parent flocks, manual separation of eggshell and bird, and a greater amount of fluff and feces on tray liners used during hatchery‐to‐farm transportation at delivery were associated with increased probability of detecting Salmonella in chick GI tracts, whereas a greater number of birds in the delivery vehicle was associated with decreased probability. The second model indicated that broiler flocks hatched on Tuesdays versus either Mondays or Thursdays (with no hatches on Wednesdays, Fridays or week‐ends), increased average hatchability of the eggs from the parent flocks, and greater amounts of fluff and feces on the transport tray liners at delivery were all associated with increased probability of detecting Salmonella in chick GI tracts. The results of this study suggest potential management decisions to lessen Salmonella contamination of broilers supplied by commercial hatcheries and areas for further research.     

Dynamics of populations of Campylobacter jejuni in two grandparent broiler breeder farms: persistent vs. transient strains

The objectives of the study were to characterize and investigate the populations of Campylobacter jejuni in two grandparent broiler breeder farms over four years. Caecal as well as farm environmental samples were obtained. Campylobacter isolates were characterized by macrorestriction profile (SmaI and KpnI-PFGE) and PCR-RFLP of the flaA gene. Susceptibility tests against seven antimicrobials were also performed. Birds were negative for Campylobacter spp. when they came to these two production farms (20 weeks), and most of the flocks remained uncolonized until they were 23 weeks old. Eighteen genotypes were characterized, with one of them (genotype 2) appearing and persisting over the study period in the two farms. In general, the strains exhibited high genetic stability, and most of them could be seen as transient in the farms, being substituted by other strains when their flock was substituted. Only one environmental sampling was positive for C. jejuni. Two different genotypes were characterized; one of them was isolated from the birds of that farm two years before. The susceptibility data point to the idea of an environmental source or reservoir of this genotype. Regarding the susceptibility of the populations, as other studies have shown, quinolone resistance (alone or combined with other resistances) was the most frequent: 68.5%. Quinolone- and multidrug-resistant strains are a matter of concern in public health. In conclusion, this survey shows the complexity of the study of the colonization of farms by C. jejuni.     

Subclinical coccidiosis in broilers and pullets

In the period from 1985 to 1987, 24 broiler crops (12 houses; one integration and 3 farms) and 9 pullet flocks (9 houses, 4 farms) were examined for parasites. Intestinal lesion scores and the number of parasites in the intestinal lumen (semiquantitative estimation) were recorded, and the Eimeria species determined when possible (broilers crops: 3rd and 5th week, pullet flocks 4th, 8th, 12th and 18th week). Additionally, the quantity of parasites in litter or faecal samples was examined in regular intervals. Clues for economic damage were only found in broiler crops with increased numbers of coccidial oocysts per gram litter in the 5th week of the fattening period. Eimeria tenella and E. acervulina were the dominating species in broiler chickens and also pullets, E. maxima oocysts however were only casual findings. No ectoparasites, helminths or other protozoa than Eimeria were observed. With regard to the intestinal lesions and the quantities of parasites in the intestine no significant differences were seen when comparing selected broiler chicks and birds taken at random. In pullet flocks the examination of random samples was the superior method, because only freshly dead bodies, collected in insufficient numbers, were suitable for diagnostics. In 3 broiler crops and one flock of replacement pullets kept on a wired floor no Eimeria were diagnosed.     

Seroprevalence of Ornithobacterium rhinotracheale infection in broiler and broiler breeder chickens in West Azerbaijan Province, Iran

Ornithobacterium rhinotracheale is a pleomorphic Gram-negative rod shaped bacterium of the rRNA superfamily V that is associated with respiratory disease in poultry. This study was conducted to determine the seroprevalence of O. rhinotracheale infection in broiler and broiler breeder chickens in West Azerbaijan (Urmia lake region) by using a commercial enzyme-linked immunosorbent assay. In this study, 463 serum samples were obtained from 50 broiler flocks and 472 blood sera from 42 broiler breeder flocks. Results showed that 41 broiler flocks (82%) and 39 broiler breeder flocks (92.8%) were positive. Ornithobacterium rhinotracheale antibodies were detected in 205 (44.2%) of the 463 broiler serum samples. Of the 472 blood sera examined from broiler breeder, 340 (72%) were positive. The results of this study indicated that the prevalence of O. rhinotracheale antibodies is high in the broiler and broiler breeder flocks in West Azerbaijan.     

Tenosynovitis in broilers and broiler breeder flocks

Tenosynovitis in commercial broiler breeder flocks, characterised by severe lameness, resulted in malnutrition and eventual culling of these chickens. Histologically there was metaplasia of tendons, tendon sheaths, connective tissues and infiltration with heterophils. Although Staph. aureus was isolated from some specimens, it is probable that the condition is of viral origin: the virus has not yet been isolated.     

Risk factors for Salmonella enterica subsp. enterica infection in senegalese broiler-chicken flocks

Our objective was to assess the association of managerial practices, general hygiene and Salmonella infection in Senegalese broiler flocks. Seventy broilers farms were studied from January 2000 to December 2001 around Dakar. A questionnaire was submitted to the farmers and samples of fresh broiler droppings were taken. A 28.6% of the flocks were infected by Salmonella (mainly Hadar and Brancaster serovars). Salmonella infection of the previous flock (OR=6.82) and of day-old chicks (OR=3.73), frequent poultry farmers’ visits (OR=5.38) and keeping sick birds inside the farm (OR=5.32) increased the risk of Salmonella infection. But, using antibiotics on day-old chicks (OR=0.17) and a detergent for cleaning (OR=0.16) decreased the risk.     

用斑点杂交法同时检测鸡群中的CAV MDV和REV

为研究鸡传染性贫血病毒(CAV)在鸡群中的感染状况以及马立克氏病病毒(MDV)和网状内皮细胞增生病病毒(REV)在鸡群中的发病率，用斑点杂交法对山东省4个肉鸡场和2个肉种鸡场进行CAV、MDV和REV的检测，结果表明除一个肉种鸡场没有检测出REV以外，其他鸡场均同时检测出CAV、MDV和REV，并且发现直接从病科中检测CAV的阳性率(20％)远远低于将病科接种SPF鸡胚后的检出率(80％)。     

Prevalence and risk factors for Salmonella spp. and Campylobacter spp. caecal colonization in broiler chicken and turkey flocks slaughtered in Quebec, Canada

We conducted an observational study to estimate prevalence and risk factors for Salmonella spp. and Campylobacter spp. caecal colonization in poultry. Eighty-one broiler chicken and 59 turkey flocks selected among flocks slaughtered in the province of Quebec, Canada, were included in the study. Flock status was evaluated by culturing pooled caecal contents from about 30 birds per flock. Exposure to potential risk factors was evaluated with a questionnaire. Odds ratios were computed using multivariable logistic regression.

The prevalence of Salmonella-positive flocks was 50% (95% CI: 37, 64) for chickens and 54% (95% CI: 39, 70) for turkeys, respectively. Odds of Salmonella colonization were 2.6 times greater for chicken flocks which failed to lock the chicken house permanently. In turkeys, odds of Salmonella colonization were 4.8–7.7 times greater for flocks which failed to be raised by ≤2 producers with no other visitors allowed onto the premises, or origin from a hatchery.

The prevalence of Campylobacter-positive flocks was 35% (95% CI: 22, 49) for chickens and 46% (95% CI: 30, 62) for turkeys. Odds of colonization were 4.1 times higher for chicken flocks raised on farms with professional rodent control and 5.2 times higher for flocks with manure heap >200 m from the poultry house, and also increased with the number of birds raised per year on the farm and with the age at slaughter. For turkeys, odds of Campylobacter flock colonization were 3.2 times greater in flocks having a manure heap at ≤200 m from poultry house and 4.2 times greater in flocks drinking unchlorinated water.