Pestiviral infections in sheep and pigs in Northern Ireland

Serological surveys were carried out to determine the prevalence of pestiviral infections in sheep and pigs in Northern Ireland. Sera from 918 ewes in 92 flocks from 10 regions were tested by ELISA for antibodies to border disease virus and positive results were obtained from 49 ewes (5.3 per cent) in 28 flocks (30.4 per cent). There were highly significant geographical variations in its flock prevalence ranging from 0 per cent in the Enniskillen region to 70 per cent in the Coleraine region. There was no significant association between the proportion of seropositive flocks and the presence of cattle on the farm (P = 0.583). In the positive flocks, the average rate of seroprevalence was 17.5 per cent, and the highest was 40 per cent. Comparative neutralisation studies on 14 positive sera with bovine viral diarrhoea virus type I (BVDV I) and border disease virus revealed higher titres (> or = four-fold) to BVDV I in all cases. Only one positive result was obtained when fluids from 186 aborted ovine fetuses were tested for border disease virus by ELISA. Serum samples from 680 pigs in 46 herds were tested for virus neutralising antibodies to border disease virus. Twenty sera (2.9 per cent) were cytotoxic, and only one of the remaining 660 sera gave a positive result. This sample tested negative for classical swine fever by ELISA, and comparative neutralisation studies showed that it had a four-fold higher titre to BVDV I than to border disease virus.     

High seroprevalence of Histomonas meleagridis in Dutch layer chickens

Histomona meleagridis is a protozoan parasite that may cause outbreaks of histomonosis with high mortality, especially in turkey flocks. Chickens are less susceptible to the disease than are turkeys, but are considered to act as an important reservoir. To determine the seroprevalence of H. meleagridis in Dutch layer chicken flocks, a large scale seroepidemiologic study (3376 samples) was performed by sampling 12 organic flocks, 24 free-ranging flocks, 40 flocks with floor housing, and 40 flocks with cage housing. At the end of the laying period, approximately 30 blood samples per flock were collected for serology. The seroprevalence found was high. In every flock, at least one of the samples tested positive while in 87% of the flocks, at least one of the samples was strongly positive. There were no significant statistical differences in seropositivity between the housing types. To confirm the enzyme-linked immunosorbent assay (ELISA) results, a small-scale seroepidemiologic study (576 samples) was performed in 29 additional layer chicken flocks kept in different housing systems. Subsequently, a subset of five seropositive flocks was selected. Five birds were obtained from each of these flocks in order to detect the parasite using culture and PCR. In all five flocks, H. meleagridis was either isolated from (culture), detected in (PCR), or both, the birds sampled. Together with the previously performed validation studies, the latter results confirm that the positive ELISA serology found is genuine. We conclude that the seroprevalence of H. meleagridis in layers is, as anticipated, high.     

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.     

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.     

Development of a blocking enzyme-linked immunosorbent assay for detection of turkey antibodies to Mycoplasma meleagridis

A blocking enzyme-linked immunosorbent assay (B-ELISA) was developed to detect antibodies to Mycoplasma meleagridis (MM) in turkey sera. This assay was based on two mouse monoclonal antibodies recognising all MM strains tested but none of seven avian mycoplasmal species tested. Furthermore, their binding to the Tween 20 antigen was inhibited by serum from MM-infected birds. The B-ELISA test format was optimized. The cut-off was determined using a set of sera from MM-free turkeys. This B-ELISA was then compared with a commercial indirect ELISA (I-ELISA). Specificities of the two ELISA tests were not significantly different (100 or 99%, respectively). The sensitivity of B-ELISA was significantly higher than the I-ELISA when I-ELISA suspicious results were considered as negative. Testing sera from experimentally MM-infected animals showed that serum plate agglutination (SPA) test detected positive birds before both ELISA methods. Samples were collected in MM-infected commercial flocks and analyzed by SPA, ELISAs, MM-PCR or culture. Results showed that the sensitivity of the B-ELISA appeared superior to the I-ELISA. Moreover, the ability to detect maternal antibodies makes it a useful tool for eradication or control of MM infections.     

Socio-economic drivers for UK organic pullet rearers and the implications for poultry health

1. Certified organic pullet producers were surveyed to gain a better understanding of the production environment, to identify the key constraints to organic pullet rearing and to identify factors that affected bird health. 2. Pullet rearers had been involved in organic production for between 1 and 12 years. 3. The number of pullets reared per annum ranged from 6 to 12 000 and the number of birds housed per unit from <50 to >1000. 4. The primary reason for being involved in organic production was given as 'commercial' with 'environmental' and 'welfare' being the next most popular categories. 5. Fewer than 50% of the respondents vaccinated their flocks and, for those that were protected, the diseases vaccinated against frequently were Newcastle disease, infectious bronchitis and Marek's disease. Annual mortality ranged from <2 to >7% with smothering accounting for 25% of all mortality. 6. Approximately 40% of respondents saw no constraints to rearing organic pullets while others identified a range of factors including capital, availability of land and inadequate margins as being the primary constraint.     

Prevalence of mycoplasma antibodies in lesser prairie-chicken sera

Serologic testing by the serum plate agglutination (SPA) procedure was performed to detect the presence of cross-reacting antibodies to Mycoplasma meleagridis, Mycoplasma synoviae, and Mycoplasma gallisepticum in lesser prairie-chickens (Tympanuchus pallidicinctus) trapped over a 2-yr period in Finney and Kearny counties of southwestern Kansas. Sera examined from birds (n = 50) obtained in March-April 2000 tested positive for M meleagridis, M. synoviae, and M. gallisepticum at levels of 6%, 10%, and 10%, respectively, for the population examined. Mycoplasma meleagridis antibodies were detected in 3 samples (2.7%), M. synoviae antibodies in 2 samples (1.7%), and M. gallisepticum antibodies in 3 samples (2.7%) from birds (n = 112) collected in March-April 2001. Data obtained by SPA can result in false positives and should be verified by additional procedures such as the hemagglutination-inhibition test. Low amounts of sera prohibited this additional testing. Thus, the positive SPA results should be considered presumptive for the presence of Mycoplasma antibodies. Although Mycoplasma antibodies have been detected in wild turkeys (Meleagris gallopavo) from Kingman and Butler counties in Kansas, this report is the first of possible mycoplasmosis in Finney and Kearny counties, Kansas. All birds testing positive by this procedure should be considered as potential carriers of Mycoplasma and should not be used in relocation efforts.     

Salmonella gallinarum field isolates of the biovars pullorum and gallinarum

In 40 cases salmonellae of the serovar Salmonella (S.) gallinarum were culturally isolated from domesticated gallinaceous birds submitted for diagnostic purposes in the period of 1979-1989. On the basis of the cultural and biochemical features found 35 of them could be assigned to the biovar Pullorum and 5 to the biovar Gallinarum. Of 35 isolates of the biovar Pullorum, 29 were isolated from pure bred chickens of small fancy-exhibition type flocks, 4 from floor-housed adult brown hybrid laying hens and one each from broiler chicks and pheasant chicks (Phasianus colchicus). Acute to subacute courses of the pullorum disease were observed in the 4 flocks of brown hybrid hens. Of 5 isolates of the biovar Gallinarum, 4 were isolated from adult brown hybrid laying hens kept in battery cages and one from floor-housed brown hybrid pullets of the laying type. First cases of fowl typhoid occurred early in the summer of 1988. The disease was characterized by a peracute course in the 4 flocks of brown laying hens and by a more acute course in the pullet flock. The primary source of the fowl typhoid producing organisms was not elucidated.     

Development of a capture ELISA for the detection of antibodies to enteropathogenic Escherichia coli (EPEC) in rabbit flocks using intimin-specific monoclonal antibodies

A capture enzyme-linked immunosorbent assay (cELISA) was developed using intimin-specific monoclonal antibodies to detect specific antibody in rabbits that have been in contact with enteropathogenic Escherichia coli (EPEC). Sera from 121 EPEC-negative, minimum-disease-level (MDL) rabbits were used for negative controls, and sera from 25 MDL rabbits, experimentally infected with EPEC of bio-/serotype 3-/O15, for positive controls. These were used to determine a cut-off value for a positive cELISA result. The value selected gave the test a sensitivity of 80.0% and a specificity of 98.4% on an individual level. At this value, a flock level sensitivity and specificity of 79.2 and 85.2%, respectively were calculated for a flock with a prevalence of seven per cent, if 40 animals were tested, and a minimum of two reactors were obtained. The test characteristics improve with increasing prevalence. To evaluate the diagnostic potential of the cELISA, sera from 40 to 50 slaughter rabbits per flock from 25 rabbit flocks with bacteriologically determined EPEC status were tested. The results demonstrated that this test can be a useful tool to determine the EPEC status of a rabbitry, provided that it is used at regular intervals.     

The effects of early and late maturity on the protein requirements of pullets

Growing pullets were exposed to two light patterns which caused a difference in sexual maturity of 5 weeks. From 28 to 38 weeks of age they were fed diets containing crude protein levels of 7.0, 8.5, 10.0, 11.5, 13.0 and 14.5 per cent. Yellow maize provided 45 per cent and soyabean meal 55 per cent of the protein in all six diets.

Rate of lay, egg weight and body weight were greater in the late maturing flock than in the early flock at the start of the assay and throughout the assay period. The late maturing pullets required more protein to reach and maintain their maximum potential than the early birds, presumably because their potential output was greater. The late birds showed a diminishing but continued response to protein up to the highest level fed (14.5 per cent corresponding to 23 g. protein per bird day). The early maturing pullets showed no response to dietary protein levels beyond 11.5 per cent and their estimated protein requirement was about 16 g. per bird day.

When limiting amounts of protein were fed (7.0–10.0 per cent of the diet) the two flocks achieved similar levels of egg output. In both flocks and throughout the assay, body weight and egg weight fell at the two lowest levels and increased at the three highest levels of protein.

It is concluded that the protein requirements of early maturing and late maturing flocks of pullets may differ, but only in a way which corresponds directly with their different potential outputs. In the late flock, which had the higher protein requirement, excellent production was obtained with a diet containing 14½ per cent crude protein all of which came from vegetable sources.     

Retarded growth rate and delayed onset of egg production associated with spirochaete infection in pullets

Retarded growth rates and delayed onset of egg production were recorded in 22-week-old pullets reared on deep litter and with indirect contact with pigs. Birds reared in cages or transferred to cages were unaffected. Spirochaetes were isolated and identified from the intestines of the pullets reared on deep litter but not from those reared in cages. Birds kept solely on deep litter were more severely affected, with 24 per cent immature birds and 10 per cent mortality compared with those transferred from deep litter to cages where no mortality was recorded but 15 to 22 per cent were found to be immature. The histopathological changes are described and the significance of the findings is discussed.     

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.     

Measurements of footpad dermatitis in broiler chickens at processing plants

A four-point photographic scale was developed to score the severity of lesions of footpad dermatitis (FPD) in broiler chickens. There was a linear relationship between the square root of the relative area of the lesions and their scores, and good agreement between different assessors using the scale. The scale was used to assess samples of 100 birds from each of 190 flocks slaughtered at two uk processing plants in 2002 and 2003; 12 of the flocks (6.3 per cent) had no lesions, but the others had lesions of different prevalences and severity. The maximum proportion of affected birds in a flock was 92 per cent. In the 178 affected flocks, 84.0 per cent of the birds had no lesions and 16.0 per cent had some evidence of FPD. The overall unweighted prevalence of birds with FPD in all 190 flocks sampled was 18.1 per cent; 10.2 per cent had only small lesions, on average equivalent in area to 2.1 per cent of the total area of the foot, 6.2 per cent had lesions on average equivalent to 6.6 per cent of the area of the foot, and 1.7 per cent had lesions on average equivalent to 21.5 per cent of the area of the foot. There were differences between the two plants in the overall prevalence and severity of FPD, but this may have been due to the fact that the plants were sampled at different times of the year.     

Eimeria infections in litter-based, high stocking density systems for loose-housed laying hens in Sweden

1. Coccidiosis, caused by different Eimeria species, is believed to be a more prominent problem in loose-housed layers kept on litter than in battery cages. In this study, the impact and development of Eimeria infections were investigated in layers kept in litter-based, high stocking density systems for loose-housed hens. 2. Layers from 57 flocks on 26 farms were followed by necropsy of a representative sample of birds that died or had to be culled. Coccidiosis was diagnosed in 11 flocks (19.3%) from 9 (31%) of the farms. The outbreaks occurred when the birds were 19 to 32 weeks old. E. maxima was identified in 6 and E. tenella in 3 of the outbreaks. 3. Sixteen of the flocks were also monitored with faecal and litter samples collected at regular intervals. Oocysts were detected in samples from all these flocks. The pattern of oocyst excretion was similar in most of the flocks, with maximum counts at 4 to 8 weeks after introduction to the laying house. There was no significant correlation between the levels of oocysts in faeces and clinical coccidiosis. 4. Raising pullets without any coccidiostat, to increase their chance to develop immunity against coccidia, was not found to decrease the risk of coccidiosis during the production period when compared to the practice of giving amprolium and ethopabate during the rearing period.     

Serologic evidence of chicken infectious anemia in commercial chicken flocks in southwest Nigeria

Sera samples from seven poultry farms in southwest Nigeria consisting of 7 broiler, 10 pullet, 1 layer, 1 cockerel, and 1 broiler breeder flocks were tested for the presence of chicken infectious anemia virus (CIAV) antibodies using a commercial enzyme-linked immunosorbent assay kit. Eleven of the 20 flocks (55%) and six out of seven (86%) farms were positive for CIAV antibodies. The seroprevalence largely depended on the age of the flocks. Seroprevalence was higher within the older pullet and layer flocks (83%-100%) than in the younger broiler flocks (0%-83%). In essence, all flocks older than 6 to 8 wk became infected. This is the first report of serologic evidence of CIAV in Subsaharan Africa. Since Southwest Nigeria is the main port of entry of imported chicken and the hub of major poultry breeders, the disease can probably be found throughout the country and beyond. Further studies are necessary to assess economic losses due to CIAV and the cost benefit of countermeasures.     

Serological investigations on reticuloendotheliosis in turkey flocks

Four meat turkey and one turkey breeding flocks were surveyed for antibodies against reticuloendotheliosis virus (REV) at different intervals using commercial enzyme-linked immunosorbent assays. In addition, serum samples collected from 18 flocks at different ages were also tested for antibodies against REV. No antibodies were detected in any of the four meat turkey flocks that were surveyed. In the breeder flock, 20%) of tested samples from 1-day-old poults were positive. Between the fourth and 12th weeks all samples that were tested yielded negative results. At 16 weeks of age 15% of samples yielded a positive reaction, but antibodies could not be detected 4 weeks later. Examination of serum samples from 18 different flocks at various ages revealed that antibodies could be detected in five flocks. The percentage of positive sera per flock ranged between 10 and 40%.     

Survey of prevalence and control of ectoparasites in caged poultry in China

To investigate the prevalence and control of ectoparasites in China, 1200 questionnaires were delivered to caged commercial layer or parent hen keepers. Of the 860 respondents, 785 (91.3 per cent) claimed they found suspected ectoparasites in their birds and 833 samples were received. Ectoparasites of the species Dermanyssus gallinae, Ornithonyssus sylviarum or Menacanthuss stramineus were found in 736 (88.4 per cent) samples. For caged commercial layers, D gallinae was the most common ectoparasite (64.1 per cent). For caged parent hens, O sylviarum was the most common ectoparasite (46.9 per cent). Most bird keepers (95.0 per cent of commercial layer keepers and 74.9 per cent of parent hen keepers) used pyrethroids, organophosphates or other insecticides or acaricides to control ectoparasites. However, 34.6 per cent of layer keepers and 25.7 per cent of parent hen keepers did not re-treat their birds with insecticides or acaricides within two weeks after the first treatment. Sanitation procedures, including cleaning, washing and disinfection, were conducted in empty houses between flocks and on most commercial layer farms and parent hen farms. However, insecticides or acaricides were used in empty houses between flocks only in 24.8 per cent of commercial layer farms and in 36.1 per cent of parent hen farms.     

Seroprevalence of Ornithobacterium rhinotracheale infection in commercial laying hens in the north central region of the United States.

This study was the first to examine the seroprevalence of Ornithobacterium rhinotracheale (ORT) within a commercial egg layer population. Serum samples collected from egg production companies were examined by serum plate agglutination test (SPAT) and outer membrane protein-based enzyme-linked immunosorbent assay (ELISA). Results show that 90% of layer flocks were positive by SPAT and 100% by ELISA. Of the pullet flocks examined, 43% and 52% were positive by SPAT and ELISA, respectively. Our study indicates that the prevalence of ORT antibody is high in the commercial layer population, suggesting that this respiratory pathogen can easily spread through multiple-age layer farms from older flocks to newly housed pullet flocks.     

Serum antibodies to bovine coronavirus in Swedish sheep.

Altogether 218 sheep sera from 40 flocks in different parts of Sweden were screened for antibodies to bovine coronavirus (BCV). Nineteen per cent of the sera were positive and there was a significantly higher frequency (p < 0.05) of at least one positive sample in flocks with more than 100 adult sheep than in smaller flocks. There was also a significantly higher frequency (p < 0.001) of positive samples from sheep older than 4 years than from younger ones. Only a weak relationship between BCV positivity (2 or more positive samples, p < 0.05) and cattle contact was demonstrated in this study. Possible transmission routes and other factors that could have affected the result are discussed. In light of our finding that all 5 sheep experimentally exposed to BCV through contact with infectious cow faeces seroconverted, we conclude that the antibodies found in Swedish sheep are probably the result of BCV infections directly or indirectly transmitted from cattle.     

Diagnostic performance of PCR and ELISA on blood and milk samples and serological survey for small ruminant lentiviruses in central Spain

The diagnostic performance of an ELISA for the detection of antibodies to the small ruminant lentiviruses (SRLVs) maedi-visna virus and caprine arthritis-encephalitis virus in milk and corresponding blood samples was evaluated in 50 sheep. The agreement between ELISA results in blood and milk was 90 per cent, and the κ value was 0.79. In addition, a serological survey in the central zone of Spain was performed using milk samples from 413 animals (250 sheep and 163 goats) from 12 flocks/herds. All flocks/herds had some animals that were positive for SRLV. Among the animals, 60.0 per cent of the sheep and 8.0 per cent of the goats tested were seropositive. Each sample was also tested using a PCR technique, which increased the percentage of positive animals detected. Using a combination of ELISA and PCR gave a total of 72.2 per cent of sheep and 28.8 per cent of goats positive for SRLV.