Experimental infection of broiler breeder hens with the intestinal spirochaete Brachyspira ( Serpulina ) pilosicoli causes reduced egg production

The pathogenic potential of the anaerobic intestinal spirochaetes Brachyspira ( Serpulina ) pilosicoli and Brachyspira innocens was evaluated in adult chickens. Thirty 17-week-old Cobb broiler breeder hens were individually caged in three groups of 10 birds. Control birds (group A) were sham inoculated with sterile broth medium. Birds in the other two groups (groups B and C) were inoculated, respectively, with an isolate of B. innocens or of B. pilosicoli . Birds were monitored daily, and killed at 41 weeks of age. Infection had no consistent effect on body weight gain, but inoculation with B. pilosicoli resulted in a transient increase in faecal water content. B. innocens infection had no effect on egg production, but B. pilosicoli infection caused a delayed onset of laying, and a highly significant reduction in egg production over the first 11 weeks of lay. This study confirms that B. pilosicoli can cause serious egg production losses in adult chickens, while B. innocens is not obviously pathogenic.     

Observations on the influence of intestinal spirochaetosis in broiler breeders on the performance of their progeny and on egg production.

Observations were made on the effect of avian intestinal spirochaetosis (AIS) in eight broiler breeder flocks on the performance of their commercial broiler progeny flocks, and also on the production of eggs and the selection of hatching eggs. The effect of treatment on egg production was analysed. The broiler breeder flocks were examined for the presence or absence of antibodies, spirochaetes and clinical signs of AIS, and correlated with the performance data from 136 commercial broiler flocks produced by them. Broiler flocks from affected breeders with clinical signs of AIS had a poorer feed conversion of approximately 90 g per kg growth, an increased number of weak chicks, slower growth and poorer feed digestion than the offspring of unaffected flocks including those previously infected with AIS but without clinical signs. Breeder flocks with clinical signs produced 7.5% less eggs than unaffected flocks. A larger number of eggs (+ 3%) was considered to have insufficient weight for successful hatching. Treatment of hens before the onset of lay prevented the negative effects on egg production but later treatment was less effective. These findings indicate that AIS in broiler breeder flocks is associated with significant production losses through decreased broiler flock performance and decreased egg production and quality.     

Prevalence,disease associations and risk factors for colonization with intestinal spirochaetes (Brachyspira spp.) in flocks of laying hens in north-eastern Italy

The present study investigated the occurrence of anaerobic intestinal spirochaetes of the genus Brachyspira in laying hen flocks in Treviso province, north-eastern Italy, with respect to prevalence, spirochaete species present, disease associations and risk factors for colonization. A total of 450 faecal samples from 45 sheds on 29 laying hen farms were cultured for intestinal spirochaetes. Nineteen sheds on 12 farms contained chickens with symptoms consistent with avian intestinal spirochaetosis, including reduced egg production, wet litter and/or pasty vents. Spirochaetes were isolated from 157 (34.8%) samples from 21 (72.4%) farms, and from 32 (71.1%) sheds. From these positive samples, 189 spirochaetal isolates were speciated using three polymerase chain reaction assays and a restriction fragment polymorphism analysis of 16S rDNA polymerase chain reaction products. Overall, 52 (27.5%) isolates were identified as pathogenic Brachyspira intermedia, 26 (13.8%) as pathogenic Brachyspira pilosicoli, 93 (49.7%) as non-pathogenic (Brachyspira innocens/Brachyspira murdochii), and 18 (9.6%) were unidentified. Faeces from 14 sheds (31%) on 10 farms (34.5%) contained B. intermedia and/or B. pilosicoli, and disease consistent with avian intestinal spirochaetosis was observed in nine of these sheds on seven farms. There was a significant association (P=0.042) between the presence of spirochaetes and using deep pits rather than conveyor belts for manure disposal. Sheds housing chickens >40 weeks of age were significantly more likely to contain spirochaetes (P=0.048) and pathogenic species (P=007) than sheds housing younger chickens. A significant association (P=0.02) was found between infection with pathogenic spirochaetes and reduced egg production.     

Antimicrobial susceptibility testing of Brachyspira intermedia and Brachyspira pilosicoli isolates from Australian chickens.

Susceptibilities of predominantly Australian isolates of the pathogenic intestinal spirochaetes Brachyspira intermedia (n = 25) and Brachyspira pilosicoli (n = 17) from chickens were tested in agar dilution against four concentrations each of the antimicrobials tiamulin, lincomycin, tylosin, metronidazole, tetracycline and ampicillin. Based on available minimum inhibitory concentration (MIC) breakpoint values for Brachyspira hyodysenteriae or other Gram-negative enteric veterinary pathogens, isolates of both species generally were susceptible to tiamulin, lincomycin, metronidazole and tetracycline. Although not classed as resistant, four isolates of B. intermedia had an elevated MIC range for tiamulin (1 to 4 mg/l), 11 isolates of B. intermedia and five of B. pilosicoli had an elevated MIC range for lincomycin (10 to 50 mg/l), one isolate of B. pilosicoli had an elevated MIC range for tetracycline (10 to 20 mg/l), and one isolate of B. intermedia and five of B. pilosicoli had an elevated MIC range for ampicillin (10 to 50 mg/l). A clear lack of susceptibility to tylosin (MIC > 4 mg/l) was seen in 11 isolates each of B. intermedia and B. pilosicoli, and to ampicillin (MIC > 32 mg/l) in two isolates of B. pilosicoli. These data suggest that some resistance to common antimicrobials exists among intestinal spirochetes obtained from laying hens and supports the need of MIC data for clinical isolates before any treatment is considered.     

Fatty liver haemorrhagic syndrome occurrence in laying hens: impact of production system

Surveys were conducted with cage and alternative layer production systems to assess the prevalence of fatty liver haemorrhagic syndrome (FLHS). Commercial caged laying hens of different ages from three farms in Queensland were monitored for three months. The mortality rate of flocks ranged from 0.8% (the youngest flock) to 11.6% (the oldest flock). Six hundred and fifty-one birds were necropsied, and approximately 40% of hens died due to FLHS. Hens kept in cages in a controlled environment shed, were at a similar risk of developing FLHS to hens kept in naturally controlled sheds, however, the heavier birds in a flock were more likely to have the condition than lighter birds. In another study, layer flocks kept in cage, barn and free-range housing systems at the University of Queensland facility, were monitored for 50 weeks. Data from necropsies and performance records showed no significant differences in mortality rates between the housing systems (6.1%, 6.4% and 5.8%, for cages, barns and free-range, respectively), but the cause of mortality was different. In cages, 74% of necropsied hens died due to FLHS. In the other systems, only 0–5% of dead hens were diagnosed with the condition. These results are in agreement with previous Australian and overseas findings which have shown that FLHS is one of the main causes of hen death in caged flocks. Factors associated with husbandry practices in different production systems, such as restricted movement, increased production and temperature variations, influence hepatic lipid metabolism and predispose hens to FLHS.     

A survey of mortality in 51 caged laying flocks

A survey of mortality was carried out in 51 caged laying flocks between point of lay and slaughter and lasted from March 1971 to June 1973. Flocks were composed of 26 white egg strains and 25 brown egg strains. Total flock population sampled was 281,000 laying fowl. Types of holding that were sampled or sub-sampled were representative of units on which 80% of the laying fowl are maintained in England and Wales. Sampling was performed at four Veterinary Investigation Centres of the Ministry of Agriculture, Fisheries and Food (M.A.F.F.) by obtaining a single day's mortality per fortnight and at a fifth Centre by collecting a specified day's mortality at weekly intervals. In 42 of the 49 flocks for which overall mortality figures were available, mortality did not exceed 16% (mean +/- SEM = 9.12 +/- 0.53) and the monthly mortality rate did not rise above 2.5%. The total number of specimens examined was 2,615. Primary and secondary diagnoses were recorded and of the former, kidney lesions (20%), disorders of the reproductive tract (15.1%), cannibalism and other injury (11.0%), Marek's disease (10.6%), staphylococcal infection (7.1%) and obesity, fatty liver and ruptured liver (7.7%) were the principal conditions encountered. Excluding those specimens for which the cause of death was unestablished, this group of conditions comprised 78.9% of all primary diagnoses. Significant variation in mortality during successive periods of lay was recorded in reproductive disorders, cannibalism, Marek's disease, staphylococcal infection and associated diagnoses of ruptured liver and obesity. No relation was found between flock size and mortality.     

Evaluation of tiamulin and lincomycin for the treatment of broiler breeders experimentally infected with the intestinal spirochaete Brachyspira pilosicoli

Brachyspira pilosicoli strain CPSp1 isolated from a chicken in a broiler breeder flock in Queensland was used to experimentally infect 30 individually caged 22-week-old Cobb 500 broiler breeder hens. Another 10 birds were sham-inoculated with sterile broth. All birds failed to become colonized. At 29 weeks of age, all birds were transferred to a diet containing 50 parts/10 6 zinc bacitracin (ZnB) and were re-challenged with the same B. pilosicoli strain at 32 weeks of age, weekly for 5 weeks. The majority of the inoculated birds then became colonized, confirming previous findings that ZnB can increase susceptibility to colonization with B. pilosicoli. The control group remained uninfected. Infected groups tended to have an increased faecal water content and faecal staining of eggshells. Ten birds were then treated by crop tube with 25 mg/kg body weight tiamulin for 5 days, and 10 birds with 20 mg/kg body weight lincomycin for 5 days. Both treatments removed the infection, while untreated birds remained infected. The results support previous observations that ZnB at 50 parts/10 6 in the diet increases the susceptibility of birds to B. pilosicoli infection, and demonstrated the usefulness of both tiamulin and lincomycin for treatment of infection with B. pilosicoli in adult birds.     

Zinc bacitracin enhances colonization by the intestinal spirochaete Brachyspira pilosicoli in experimentally infected layer hens

Brachyspira pilosicoli strain CPSp1 isolated from a chicken in a broiler breeder flock in Queensland was used to experimentally infect 40 individually caged 22-week-old laying hens. Another 10 birds were sham-inoculated with sterile broth. All chickens received a commercial layer diet, but 10 infected birds had 50 parts/10 6 zinc bacitracin (ZnB) incorporated in their food. Birds were kept for 7 weeks, and faecal moisture, egg numbers, egg weights and body weights were recorded weekly. B. pilosicoli was isolated from the faeces of only three of the 30 inoculated birds receiving the diet without ZnB, whereas seven of the 10 inoculated birds receiving ZnB in their diet were colonized. This difference in colonization rate was highly significant ( P = < 0.001). Dietary ZnB at 50 parts/10 6 therefore predisposed to colonization by B. pilosicoli. Despite colonization, no significant production differences were found between the birds in the three groups.     

Prevalence and disease association of intestinal spirochaetes in chickens in eastern Australia

Faecal samples (n = 1786) from chickens in broiler breeder (n = 28), layer (n = 22) or broiler (n = 19) flocks in the eastern states of Australia were cultured for intestinal spirochaetes. Overall, birds in 42.9% of broiler breeder and 68.2% of layer flocks were colonized with spirochaetes, but no birds in broiler flocks were infected. Colonization rates in infected flocks ranged from 10 to 100% of birds sampled. Faeces from colonized flocks were on average 14% wetter than those from non-colonized flocks. There was a highly significant association between colonization with spirochaetes and the occurrence of wet litter and/or reduced production. A subset of 57 spirochaete isolates from birds in 16 flocks were identified to the species level using a panel of polymerase chain reaction tests. Isolates from nine (56%) of these flocks were spirochaetes that are known to be pathogens of poultry: Serpulina pilosicoli was isolated from birds from five flocks, birds from two flocks were infected with Serpulina intermedia, and in two other flocks both species were identified. Isolates from the other seven flocks belonged to other Serpulina species, which are currently of unknown pathogenicity. This study indicates that infections with intestinal spirochaetes are a common but currently under-diagnosed cause of wet litter and/or reduced egg production in broiler breeder and layer flocks in Australia.     

Newly isolated serotypes of infectious bronchitis virus: their role in disease

The pathogenicity of isolates of infectious bronchitis virus (IBV) made from broiler or breeder flocks in Britain between 1981 and 1983, together with three made from flocks of commercial laying hens during 1984, has been investigated. When 11-day-old IBV-free chicks were challenged with these IBV isolates, together with a pool of pathogenic strains of E. coli, some mortality was recorded, together with a high incidence of morbidity. Three IBV isolates, when given to groups of IBV-free brown-egg laying hens, caused only a minimal effect on egg production but markedly affected egg shell colour.     

Observations on an outbreak of fowl typhoid in commercial laying birds in Udi, South Eastern Nigeria

Observations made in an outbreak of fowl typhoid in 11,000 laying birds in Udi, South Eastern Nigeria are reported. The commercial laying flock had daily mortality of 1.8% with total mortality of 25%. Major clinical signs observed were greenish/yellowish diarrhoea and marked reduction in egg production. At necropsy, enlarged dark greenish liver and enlarged spleen were observed. Pericarditis and egg peritonitis were also evident. Pure cultures of Salmonella gallinarum were obtained from all the internal organs cultured. Histological section of the liver showed hepatitis, necrosis of the Kupffer cells, and infiltration of the mononuclear cells. Intestinal section showed enteritis elongated crypts, and total loss of villi. About 8,250 layers recovered from the Salmonella infection after treatment with flumequine. Egg production was gradually restored to 70%. Improved biosecurity measures and vaccine administration are suggested ways of preventing salmonellosis in poultry farms.     

Infection of broiler parent hens with avian intestinal spirochaetes: Effects on egg production and chick quality

Broiler parent hens were inoculated with avian intestinal spirochaetes several weeks before the onset of egg production. The infection persisted, wet droppings developed, and egg production, mean egg weight and carotenoid contents of the eggs were decreased. Hatching eggs were collected and incubated. In broilers which hatched from these eggs, reduced gain in body weight at 2 and 3 weeks of age, wet droppings, low plasma carotenoid concentration and elevated alkaline phosphatase activity in the blood plasma were observed. Spirochaetes were not detected in these broilers. These findings demonstrated the deleterious effects on chick quality of parental infection with avian intestinal spirochaetes. Avian intestinal spirochaetosis was diagnosed in about 2.5% of all submissions from reproductive flocks in 1991.     

The epizootiology of Marek's disease: I. Incidence of antibody, viraemia and Marek's disease in six flocks

Six flocks consisting of the female grandparent line of a well known broiler strain were studied in an effort to determine the important aetiological factors in Marek's disease. Each flock was hatched in the same hatchery but at intervals of six weeks. Chicks of each flock were reared to between 8 and 9 weeks of age on a rearing site after which they were moved to a production site. Mortality was recorded to house and pen in all flocks. In addition six pens of about 300 chickens on each of the production sites were selected for special examination. Blood samples were collected at intervals from birds in these pens for determination of the incidence of precipitating antibody and viraemia, and a high proportion of birds dying in these pens were examined post mortem. All six flocks were infected with Marek's disease virus. Although the levels of mortality from Marek's disease varied greatly from flock to flock (0.6 to 23.4%) and as greatly between houses used by a single flock, and between pens within a house, there was little relationship between the pathogenicity of the viruses present in a flock or group of chickens and the subsequent mortality from Marek's disease. Maternal antibody was present in 90.0% of day old chicks, 66.7% of chicks at 7 days of age, 23.9% of chicks at 14 days of age and 2.1 % of chicks at 21 days of age. Active antibodies were present in all flocks but the time at which they were detected varied from flock to flock and from pen to pen within a flock. Virus was not isolated from chicks between three and five weeks of age but was isolated from the blood of 174 of 179 chickens from 10.5 weeks of age and older. The data of this study are not adequate to determine with certainty the effect supply flock, rearing site and house, and production site and house had on mortality from Marek's disease, however they strongly suggest that 'the rearing site had the greatest influence. Because in most cases the chickens were primarily infected with Marek's disease virus at the rearing site, it is suggested that the virus with they are first infected is important in respect of subsequent mortality from Marek's disease.     

Naturally occurring clinical reticuloendotheliosis in turkeys and chickens

Outbreaks of clinical reticuloendotheliosis (RE) were observed in a turkey flock and two pullet flocks. Clinical signs in turkeys included sleepiness, weakness, anorexia, diarrhoea and reduced egg production. The pullets showed severe emaciation, loss of back feathers, anorexia and diarrhoea. Fifteen out of 54 turkeys died before the flock was killed. One pullet flock suffered 20% mortality while the other had an average daily mortality of four to six out of 2000 birds for 9 weeks with a total mortality of 16.4%. Necropsy of the dead turkeys and pullets showed neoplastic nodules or grey foci in the internal organs especially the liver, intestines and spleen. Histopathological sections of the organs had proliferation of reticular cells with necrosis of the parenchyma and focal lymphocytic infiltration. RE virus antigens and precipitating antibodies were detected in the serum samples collected from the birds. It was suspected that natural RE could be a more serious problem than earlier reported in some countries.     

Significance of interactions between Escherichia coli and respiratory pathogens in layer hen flocks suffering from colibacillosis-associated mortality.

This study aimed to examine the significance of interactions between Escherichia coli and various respiratory pathogens during outbreaks of colibacillosis-associated mortality in layer hen flocks under field conditions. For this purpose, a case-control study involving 20 control flocks with baseline mortality and 20 flocks with increased mortality due to E. coli septicaemia and polyserositis, was conducted. In each colibacillosis flock, blood samples were taken from 20 hens at the onset of clinical disease and three times thereafter at 2-week intervals. Control flocks of comparable ages were sampled in the same way. Pooled sera, taken at the first and last sampling, were examined for antibody titres against infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), and the individual sera from all four samplings were examined for the presence and/or titres of antibodies against avian pneumovirus (APV), Mycoplasma gallisepticum, Mycoplasma synoviae and Ornithobacterium rhinotracheale. Titre increases were seen for IBV D274 (one control flock) and O. rhinotracheale (one control and one colibacillosis flock). An increase in per cent reactors was seen for APV (one control flock), and for M. synoviae (one control and two colibacillosis flocks). The study failed to detect any consistent interactions between E. coli and the aforementioned pathogens. These results indicate that, at least as observed in this study, outbreaks of increased mortality resulting from colibacillosis are not necessarily associated with IBV, NDV, APV, M. gallisepticum, M. synoviae or O. rhinotracheale infections.     

Evaluation of an egg yolk enzyme-linked immunosorbent assay antibody test and its use to assess the prevalence of Mycoplasma synoviae in UK laying hens

The frequency of Mycoplasma synoviae exposure in a convenience sample of commercial layers was established by the presence of antibody in eggs. Chloroform-extracted egg yolks were found to be more suitable than saline-extracted yolks, and were used with a commercial enzyme-linked immunosorbent assay kit, having first established the sensitivity and specificity of the kit with eggs from known M. synoviae-positive and M. synoviae-negative flocks. For the prevalence study, pooled yolks from 12 eggs were obtained from each of 56 randomly selected laying farms in possession of a packing station number in the east of England. This number allowed 95% confidence of detection of antibody in one egg if present in 50% of the flock. Eggs were taken from the oldest flock on each site and were returned with a completed questionnaire. The prevalence of egg antibody to M. synoviae was 78.6% (95% confidence interval, 65.6, 88.4). This study has confirmed that chloroform extraction of yolk antibody is a suitable approach for assessing the flock prevalence of M. synoviae infection in layer hens.     

Colibacillosis in caged layer hens: characteristics of the disease and the aetiological agent.

In Europe, outbreaks of acute mortality in layer flocks due to colisepticaemia have frequently been observed since the mid-1990s. The aims of this study were to describe the disease, to identify the serotypes of the avian pathogenic Escherichia coli (APEC) present in these outbreaks, and to detect the presence of F11 fimbriae and flagella in the isolates. For this purpose, 20 flocks with APEC-associated increased mortality and 20 control flocks matched for age were examined. Weekly mortality rates in the colibacillosis-affected flocks reached 1.71%, versus 0.30% in the control flocks. The maximum cumulative mortality over an entire colibacillosis outbreak reached 9.19%. The disease was often flock and hen house associated, with recurrent outbreaks within one round and in successive rounds in the same house. Disease was usually acute without clinical symptoms. Peritonitis with yolk material deposited in the peritoneal cavity and polyserositis were the main lesions at necropsy. O78 strains were isolated in 15 of the 20 colibacillosis flocks, and in only one of the control flocks. The majority of strains from the control flocks could not be serotyped by the 28 O-antisera used. In general, F11 fimbriae and flagella were present in the majority of the strains. F11 fimbriae were significantly more often found in O78 isolates than in the other serotypes, and are thus more often present in isolates from colibacillosis flocks. Strains positive for F11, and for F11 and flagella, were more frequently present in heart and liver of the colibacillosis-affected flocks.     

Economic effects of subclinical infectious bursal disease on broiler production

A survey of the infectious bursal disease (IBD) status of 85 clinically normal broiler flocks was carried out. Flocks were grouped into three categories: flocks without IBD lesions (category A), flocks with typical acute IBD lesions (B) and flocks with typical chronic IBD lesions (C). Category A flocks achieved a net income per 1,000 birds which was 11% better (P<0.05) than category B flocks and 14% better (P<0.01) than category C flocks. The 85 broiler houses used by the surveyed flocks during production were similarly grouped into the three categories. Analysis of production data from 991 flocks comprising 14 million birds demonstrated that flocks reared in category A houses achieved a similar superiority in net income per 1,000 birds over those flocks reared in both category B and category C houses. Food conversion ratio and average weight per bird were also superior in flocks reared in category A houses. These findings suggest that IBD virus persisted from flock to flock in category B and category C houses. The differences in performance were greatly accentuated during the winter months. The results indicate that the presence of IBD virus infection accounts for about two-thirds of the reduced profitability achieved by broiler flocks in Northern Ireland during the winter.     

Intestinal spirochaetes (Brachyspira spp.) colonizing flocks of layer and breeder chickens in Malaysia

Avian intestinal spirochaetosis causes problems including delayed onset of lay and wet litter in adult chickens, and results from colonization of the caecae/rectum with pathogenic intestinal spirochaetes (genus Brachyspira). Because avian intestinal spirochaetosis has not previously been studied in South East Asia, this investigation was undertaken in Malaysia. Faecal samples were collected from 25 farms and a questionnaire was administered. Brachyspira species were detected by polymerase chain reaction in 198 of 500 (39%) faecal samples from 20 (80%) farms, including 16 (94%) layer and four (50%) breeder farms. Pathogenic Brachyspira pilosicoli was identified in five (29%) layer and two (25%) breeder farms whilst pathogenic Brachyspira intermedia was detected in nine (53%) layer and one (12.5%) of the breeder farms. Twelve (80%) layer farms had egg production problems and 11 (92%) were positive for Brachyspira: three (25%) for B. pilosicoli and six (50%) for B. intermedia. Of three breeder farms with egg production problems, one was colonized with B. pilosicoli. Three of ten layer farms with wet litter were positive for B. pilosicoli and six for B. intermedia. Of four breeder farms with wet litter, one was colonized with B. pilosicoli and one with B. intermedia. No significant associations were found between colonization and reduced egg production or wet litter, perhaps because so many flocks were colonized. A significant association (P = 0.041) occurred between a high prevalence of colonization and faecal staining of eggs. There were significant positive associations between open-sided housing (P = 0.006), and flocks aged >40 weeks (P < 0.001) and colonization by pathogenic species.     

Characterization of Erysipelothrix rhusiopathiae isolates from laying hens and poultry red mites (Dermanyssus gallinae) from an outbreak of erysipelas

Infection with the zoonotic bacterium Erysipelothrix rhusiopathiae causes severe disease outbreaks (erysipelas) in poultry flocks. As this bacterium has been isolated from the poultry red mite (Dermanyssus gallinae), this parasite has been suggested as a possible means of transmission of E. rhusiopathiae on and between poultry farms. To further elucidate the capacity of the mite as a reservoir, we analysed and compared 56 bacterial isolates from laying hens and nine isolates from mites by pulsed-field gel electrophoresis (PFGE), using the restriction enzyme SmaI. The isolates originated from one outbreak in a laying hen flock housed in an indoor litter-based aviary system. Except for two isolates, a homogeneous banding pattern was obtained from all isolates analysed, suggesting that a single strain was the cause of the outbreak. Another finding was that isolates from individual hens could exhibit slightly different PFGE patterns. Mites collected from the same house at the end of the production period of the following flock were negative for the presence of E. rhusiopathiae. An increasing number of erysipelas outbreaks as well as escalating problems with D. gallinae are expected in other European countries related to the forthcoming changes in housing systems for laying hens. Consequently, further studies are needed to investigate the importance of erysipelas in poultry and the importance of D. gallinae in the transmission of E. rhusiopathiae.