Immunity to avian pneumovirus infection in turkeys following in ovo vaccination with an attenuated vaccine.

Fertile turkey eggs after 24 days of incubation were vaccinated in ovo with a commercial live attenuated subtype A avian pneumovirus (APV) vaccine. Hatchability was not adversely affected. When a high dose (10 times maximum commercial dose) of vaccine was tested in maternal antibody negative (MA-) eggs, mild clinical signs developed in a small proportion of the poults for 1-4 days only. Post-vaccination antibody titres at 3 weeks of age were significantly higher than those seen when the same dose was administered by eyedrop or spray at day-old. A low dose (end of shelf-life titre) of vaccine given to MA- eggs did not cause disease and vaccinated poults were 100% protected against virulent APV challenge at 3 or 5 weeks of age. Post-vaccination antibody titres reached significant levels at 3 weeks of age, whereas those from MA- poults vaccinated by spray at day-old with a similar low dose did not. In a 'worst-case' scenario, maternal antibody positive (MA+) poults vaccinated in ovo with the low dose were still 77% protected against clinical disease, despite lack of seroconversion. The recommended commercial dose of vaccine given to MA- eggs in ovo induced 100% protection against virulent APV challenge for up to 14 weeks of age, even though post-vaccination antibody titres had dropped to insignificant levels at this age. In ovo vaccination with a mixture of the recommended commercial doses of live APV and Newcastle disease (ND) vaccines had no detrimental affect on the efficacy of the APV vaccine. This is the first report of the successful use of an APV vaccine being given in ovo. The results indicate that for turkeys, in ovo vaccination with a live attenuated APV vaccine is safe and effective against virulent challenge and comparable with vaccination by conventional methods.

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.

Vertical temperature profiles at bird level in broiler houses.

1. The temperature in the close vicinity of commercial broilers was studied in relation to the setpoint temperature throughout the rearing period. 2. Mean temperature in the immediate environment of the chicks was 2.0 degrees C lower than the setpoint of 1 d of age. During the first week this initial temperature difference gradually rose to l.7 degrees C above setpoint. At 18 d of age a further rise to a mean difference of 4.0 degrees C above setpoint was measured. The difference then remained constant from 32 d of age until the end of the fattening period. 3. It was concluded that the chickens were actually brooded at 30 degrees C. During the rearing period the ambient temperature in the close vicinity of the broilers gradually declined to 26 degrees C. 4. During the finishing period, ambient temperature around the broilers was far above the value recommended for optimal food intake and growth. 5. These results are discussed in relation to heat generation and heat fluxes in the broiler houses.

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.

Infection of broiler chicks (Gallus domesticus) with human intestinal spirochaetes.

One-day-old broiler chicks were infected orally with spirochaetes isolated from cases of intestinal disorder in humans. Three different isolates were studied in an experiment of 22 days duration. No signs of clinical disease were observed; the infection did not cause changes in the concentration of carotenoids or in the activity of alkaline phosphatase in the serum. Spirochaetes were shed in the caecal faeces. At autopsy, no lesions were seen in the intestinal tracts of the birds. Large numbers of spirochaetes were present in the caecum of 30 to 100% of the infected birds; in a few birds small numbers of spirochaetes were observed in scrapings from the mucosa of the small intestine. On histological examination massive colonisation of the caecal mucosa was observed. Spirochaetes of two isolates had invaded the caecal mucosa and for one of these, they were found between enterocytes, but not below the basement membrane. The other isolate had produced gap-like lesions, subepithelial accumulations of spirochaetes and focal erosion. No signs of an inflammatory reaction were observed.

Ascorbic acid and infectious bronchitis infections in broilers.

The effect of supplementing the feed of broiler chicks with different levels of ascorbic acid on the resistance against infectious bronchitis virus was investigated. Resistance was measured by the severity of tracheal lesions and the development of airsacculitis after challenge. The effect of ascorbic acid was dose dependent. Addition of 300 to 330 ppm ascorbic acid to the feed gave the best results. High concentrations (>600 ppm) had a less beneficial effect.

Comparison of the enzyme linked immunosorbent assay, the haemagglutination inhibition test and the agar gel precipitation test for the detection of antibodies against infectious bronchitis and Newcastle disease in commercial broilers.

Serological results as obtained by the agar gel precipitation (AGP) test, haemagglutination inhibition (HI) test (M41, D274, D1466) and an enzyme linked immunosorbent assay (ELISA) from commercial broiler flocks, which had suffered from a clinical infectious bronchitis (IB) infection in the fattening period, were compared with serological findings of control broiler flocks. In addition the Hi-test and ELISA for Newcastle disease (ND) were compared. The AGP results differ significantly between groups. The test had a low sensitivity. The results of the HI-IBV tests were similar for both groups and no difference was seen between flocks with or without clinical IB problems. The IBV ELISA showed a highly significant difference between the two groups. In contrast to the low and not significant correlation coefficients (r) between the IBV HI tests and the ELISA, the value of r between the NDV HI and ELISA was high. The results indicate an ELISA as the preferred test for the diagnosis of IB in broilers.

Influence of infection with avian intestinal spirochaetes on the faeces of laying hens.

Laying hens of 20 weeks of age were infected with avian intestinal spirochaetes (isolate 1380). After 20 weeks it was found that most infected birds shed 10(7) or more spirochaetes/ml caecal faeces. Faecal dry matter content was not significantly influenced by the infection, but the amount of crude fat in the faecal dry matter increased by more than 25%.

Spirochaetosis in broilers.

One-day-old broilers were inoculated with spirochaetes (isolate 1380); the inocula consisting either of spirochaetes derived from plate culture or from intestinal homogenates of previously infected birds. After 13 to 15, and 21 days after inoculation growth was depressed, serum concentrations of protein lipid, carotenoids and bilirubin were decreased and the fat content of the faeces was increased. The activity of alkaline phosphatase in the serum was increased but the activities of tau-glutamyl transferase, sorbitol dehydrogenase, aspartate aminotransferase and alanine aminotransferase of the infected groups were not affected. These findings indicate impaired resorption in the smaller intestine which cannot be explained from a direct effect of the spirochaetes on the smaller intestinal wall nor from pathological changes in the liver.

Observations on avian intestinal spirochaetosis.

Three SPF-laying hens were inoculated into the crop with avian intestinal spirochaetes which previously had been passaged in broiler chicks by oral inoculation (isolate 1380). Mild persisting gastrointestinal disorder developed; at nine months post inoculation spirochaetes were readily demonstrated in caecal faeces. Histologic examination of the caecal mucosa revealed many spirochaetes covering the mucosal surface and filling up the crypts lumina. Spirochaetes were found in intra- and subepithelial locations and in gaps running through the epithelium. These gaps often opened into subepithelial cavities crowded with spirochaetes ('gaplike lesions'). These lesions were seen mostly on the tips of the villi and in the deeper parts of the crypts. Massive erosion or desquamation of epithelium heavily infested by spirochaetes occurred. These findings indicate colonisation of the mucosal surface and of the crypts, penetration of the mucosa and colonisation of subepithelial compartments with spirochasetes in poultry suffering from intestinal spirochaetosis.

Incidence of spirochaetal infections in cases of intestinal disorder in chickens.

The incidence of intestinal spirochaetes was determined using direct fluorescent antibody microscopy on faecal and mucosal samples from chickens. Of 134 flocks with intestinal disorders 27.6% were found to be positive, but only 4.4% (of 45 flocks) were positive where signs of enteritis were absent. Flocks housed in cages or with access to litter were equally affected. No evidence was found for pigs as an aetiological factor.

Molecular epidemiology of infectious bronchitis virus in The Netherlands.

Twelve Dutch isolates and the M41 strain of infectious bronchitis virus (IBV), a coronavirus of chickens, were characterized by cross-neutralization and T1 finger-printing to elucidate their evolutionary relationship. The T1 fingerprinting showed that the Dutch isolates formed two clusters. The first cluster contained strains H52, H120, D387, V1259, V1385 and V1397; the estimated sequence homology is 99%. Cluster two comprised strains D207, D274, D212, D1466, D3128 and D3896, which have about 95% sequence homology. The M41 virus did not belong to either cluster. The four different serotypes which arose in the late 1970s belonged to cluster two and appeared to be different from the vaccine strains (H52 and H120) used at that time. This indicates that the strains were newly introduced and could have arisen from a common virus. On the other hand, three recently isolated field strains were genetically closely related to the vaccine strains H120 and H52 (cluster one), suggesting that these live vaccine strains themselves could have given rise to these serologically altered field isolates. The data are relevant to the development of new vaccine strategies.

Comparison of the effect of live Newcastle disease vaccine Clone 30 in broilers administered at day 1 or at day 7 and the effect of H120 vaccination at 17 days of age: a field experiment.

To analyse the results of a vaccination on the first day of age against Newcastle disease (ND) and on the 17th day of age against Infectious Bronchitis (IB) resp. with spray vaccines with Clone 30 and H120 vaccine. These vaccinations are compared in field circumstances with other vaccination methods. A serological examination and challenge test were used to be informed about the response and protection. From the present study the following conclusions can be drawn: Clear indications are obtained that following a spray vaccination against ND with Clone 30 vaccine of one-day-old broilers which possessed maternal antibodies, birds received a moderately good protection against ND, in spite of very low levels of HI antibodies. A spray vaccination against IB with H120 vaccine of broilers at 17 days of age gave some protection from two weeks after vaccination, however making a good conclusion about the protection is impossible and further investigation is required.

Infectious typhlitis in chickens caused by spirochetes.

A weakly haemolytic spirochete was detected with an unabsorbed fluorescent antiserum to Treponema hyodysenteriae in smears and cultures of scrapings of caecal mucosa of laying hens with diarrhoea. Two groups of experimental chickens were fed a pure culture of this spirochete or homogenated intestinal contents of affected birds. Both groups showed clinical signs of disease such as increased water content of faecal material and slight retardation of growth. A non-specific typhlitis which histologically resembled milder forms of swine dysentery was seen in the birds from which spirochetes were isolated. The isolate obtained differed in cultural, biochemical, anti-genic and morphological characteristics from T. hyodysenteriae. The pathological significance of intestinal spirochetes and their possible epidemiological relation to swine dysentery are discussed.

Occurrence and significance of infectious bronchitis virus variant strains in egg and broiler production in the Netherlands.

Despite vaccination against Infectious bronchitis virus (IBV) with the Massachusetts type vaccine viruses H120 and H52 in the Netherlands, an increasing number of properly vaccinated flocks have suffered from the disease since 1978. In the years 1978-1982, the virus was isolated from 162 IBV suspected flocks. Cross-virus-neutralization tests showed that the majority (67 per cent) of these isolates belonged to serotypes other than the Massachusetts type, the Connecticut-, Florida-, Iowa 97-, Iowa 609- and JMK serotype. The majority of these Dutch isolates could be divided into 4 serogroups, called D207, D212, D3128 and D3896. Only a few isolates were not related to these serotypes. A survey of 328 flocks for antibody against these serotypes demonstrated that antibody against one or more of these novel serotypes were present in most of the flocks. Experiments demonstrated that vaccination with the H120 vaccine virus was not able to protect chickens against the adverse effects of a challenge with the novel serotypes.

A case of Aujeszky's disease virus infection in young chicks.

On a rearing farm with 96,000 birds, 10,000 three and four days old chicks died with nervous symptoms. A virus was isolated from the brains and identified as an Aujeszky's disease virus. The isolate was very pathogenic for chickens up to about 7 days of age, causing mortality after parenteral injection (intracerebral, intraperitoneal, intramuscular) but not after oral, eye drop or spray application. An Aujeszky vaccine virus, made apathogenic by passages in chicken cells for use in swine, had the same pathogenic properties for chicks. The isolated Aujeszky's disease virus is regarded as the agent responsible for the death of the 10,000 chicks on the farm. This virus most likely had been injected in just hatched chicks instead of or together with the Marek vaccine virus. In addition to meningitis, edema, neuronophagia and cuffing of blood vessels with mononuclear cells, haemorrhages were observed in thin sections of brain and spinal cord. After injection of isolate and vaccine virus in the leg muscle intranuclear inclusion bodies were observed in the ganglion cells in the spinal cord. Inclusion bodies have not been described before in pathological conditions of the nervous tissue of chickens.

A study on the synthesis and secretion of immunoglobulins by the Jarderian gland of the fowl after eyedrop vaccination against infectious bronchitis at 1-day-old.

One-day-old chickens with maternally derived antibodies to infectious bronchitis virus (IBV) were vaccinated against IB by eye-drop. At 2 and 3 weeks of age the synthesis of immunoglobulins of the IgA isotype in the Harderian gland was demonstrated by immunofluorescence. With an anti IgG conjugate diffuse fluorescence of IgG was observed in the gland at 2, 3 and 4 weeks of age. Involvement of the Harderian gland in the synthesis or the secretion of IgM after IB vaccination could not be demonstrated by immunofluorescence. A quantitative estimation of immunoglobulins was carried out by laser nephelometry. At 2 weeks of age the concentration of antibodies against IBV of the IgA isotype (IgA-IBV) was higher in the tears than in the serum. This and the positive fluorescence indicate a local synthesis of IgA-IBV in the Harderian gland. The highest concentration of IgG antibodies against IBV (IgG-IBV) in the serum was measured at 2 weeks of age, when IgG antibodies could not be detected in the tears. In the tears the IgG-IBV concentration increased from 2 weeks up to and including 5 weeks of age, when the concentration in the tears was higher than in the serum. These findings and the diffuse IgG fluorescence in the Harderian gland suggest a mainly systemic production of IgG-IBV and an active and selective transport of IgG-IBV from the serum to the tears by the Harderian gland. Challenge at 6 weeks of age of the vaccinated chicks caused a sharp increase of IgG-IBV in the serum and a decrease of IgA-IBV in the tears 1 week later. Challenge of the unvaccinated control chicks resulted in a distinct rise of IgA-IBV in the tears and in a low IgG-IBV concentration in the serum after 1 week. These findings and the neutralisation indices measured for sera collected at 5 and 7 weeks are discussed.

Study on the local effect of eye-drop vaccination against infectious bronchitis in 1-day-old chicks with maternal antibodies.

One-day-old chicks with maternal antibodies to infectious bronchitis virus (IBV) were vaccinated by eye-drop with H120 vaccine strain of IBV. Four weeks later the chicks were challenged by eye-drop or intratracheally with virulent IBV (Massachusetts-type field strain). The chicks were resistant to ocular challenge, but highly susceptible to an intratracheal challenge. After intratracheal challenge the birds showed clinical signs of infectious bronchitis (IB). The immunofluorescence test on IBV was positive. Macroscopical and microscopical lesions were present in the trachea. From these observations it was concluded that the protection against virulent IBV after eye-drop vaccination is localised mainly in the conjunctival and nasal tissues. Thus in vaccination studies with IBV the result of challenge depended highly on the route of application of the challenge virus. Ten days after challenge the neutralisation index of serum for IBV was significantly higher in the intratracheally-challenged chicks as compared with their eye-drop challenged or/and unchallenged mates.

Effect of the removal of the Harderian gland in 1-day-old chicks on immunity following IB vaccination.

After removal of the Harderian gland in 1-day-old chicks (Hx birds), protective immunity to infectious bronchitis virus (IBV) was decreased 3 weeks after vaccination with the H120 strain of IBV. Protective immunity was measured by challenge. The decreased protection was not reflected in the neutralisation indices of the Hx birds. In contrast, the mean neutralisation index was higher in the Hx birds than in the vaccinated controls. The role of the lachrymal gland in the development of immunity to IBV is discussed.