Replication of Marek's disease vaccines in turkey embryos and their effect on TLR-3 and IFN-γ transcripts.

Understanding the pathogenesis of herpesvirus of turkeys (HVT) in its natural host is necessary before recombinant HVT (rHVT) can be used efficiently in turkey flocks. The objectives of this study were to evaluate when commercial turkey flocks get infected with wild type HVT, to study replication of HVT (conventional and recombinant rHVT-Newcastle disease, rHVT-ND) and other Marek's disease (MD) vaccines (SB-1 and CVI988) in turkey embryonic tissues, and to evaluate the expression of TLR-3 and IFN-γ in the lung and spleen of one-day-old turkeys after in ovo vaccination with MD vaccines. Our results demonstrated that commercial turkeys got exposed to wild type HVT within the first days of life; therefore, there is a potential of interaction between wild type HVT and rHVT when administered at day of age. On the other hand, all evaluated vaccines (especially HVT and rHVT-ND) replicated very well in turkey embryonic tissues. In ovo vaccination with HVT and CVI988 increased transcription of TLR-3 in the spleen of one-day-old turkeys. However, no effect on the transcription of TLR-3 or IFN-γ in the lungs and IFN-γ in the spleen in newly hatched turkeys was detected in the present study. Because of the limitations of evaluated genes, timepoints, and studied tissues, future studies are warranted to better understand the effect of MD vaccines on the turkey embryo immune responses.RESEARCH HIGHLIGHTS Commercial turkey flocks get infected with wild type HVT within the first days of life.HVT and rHVT replicates readily in turkey embryonic tissues.SB-1 and CVI988 also replicate in turkey embryonic tissues, but at lower rates than HVT and rHVT.HVT and CVI988 increase transcription of TLR-3 in the spleen.

The effect of pressure on turkey breast skin.

In an attempt to experimentally reproduce focal ulcerative dermatitis (FUD) in turkeys, pressures of 94, 136, and 240 mmHg were applied for 2, 4, or 6 hr daily for 4 consecutive days to unfeathered breast skin of six 9-week-old toms. No gross lesions occurred either immediately after treatment or during a 10-day post-treatment period, and no microscopic changes were present in the skin at the conclusion of the trial. These findings suggest that avian skin is resistant to pressure-induced decubital ulceration and that pressure is unlikely to be either the cause of or a significant contributor to FUD.

A combination chemical/physical method for repeated restraint of turkeys.

A method for the repeated long-term restraint of young turkey toms was developed. Fifteen mg xylazine/kg body weight was administered intramuscularly (IM) to each of 60 toms whose heads and bodies were then covered with surgical stockinette secured with adhesive tape during a total of 229 restraint events (RE). Toms then were restrained in dorsal recumbency for 2, 4, or 6 hr daily for 4 days. Those restrained for 6 hr received an additional IM injection of 10 mg xylazine/kg body weight after 3 hr of restraints. Three toms with airsacculitis or pneumonia died during restraint, and one with pneumonia died during the night between RE. The mean body temperature of restrained toms declined during the first 150 min of RE and then stabilized. Toms restrained 6 hr daily lost weight during the 4 treatment days. Toms restrained 2 hr and 4 hr gained weight, but the latter group did not gain weight as quickly as the former.

An outbreak of influenza (H1N1) in turkey breeder hens.

Outbreaks of influenza were diagnosed in two turkey breeder flocks on the same premises in eastern North Carolina during the "dark-out" period of recycling for a second lay. Clinical history included increased mortality from acute death with no apparent predisposing illness. Mortality attributed to the disease was 4.5% in one flock and 3.3% in the other. Necropsy findings included severe diffuse congestion and edema of both lungs, with little or no pleural exudate. Spleens were moderately to markedly enlarged and mottled, and kidneys were swollen and congested. Microscopic lesions included moderate to severe serofibrinous pneumonia with severe pulmonary congestion. Splenic changes included fibrin deposition and severe congestion, and severe congestion was noted in kidneys. Influenza virus (H1N1) was isolated from pools of tissues including lung, spleen, liver, and kidney, and both flocks seroconverted to influenza (H1N1) virus.

Monensin toxicity in turkey breeder hens.

High mortality in two flocks of 1900 turkey breeder hens accidentally fed 280 g monensin/ton of complete feed is described. Mortality attributed to the poisoning was 76% in flock 1 and 18% in flock 2. Clinically, turkeys were found dead, exhibited respiratory distress with wings extended laterally, had fine tremors, or showed posterior paresis and inability to rise. The most striking finding at necropsy was the almost complete absence of gross lesions. Some turkeys had severely congested lungs; however, many did not. A few birds had pale streaks within the adductor muscles of the legs. Microscopic lesions included myofiber degeneration and necrosis of skeletal and myocardial muscle. Serum phosphorus, lactate dehydrogenase, and creatine phosphokinase were markedly elevated, whereas potassium, chloride, and calcium values were lowered.

Focal ulcerative dermatitis ("breast buttons") in marketed turkeys.

Features of focal ulcerative dermatitis ("breast buttons"), a skin disease occurring most commonly in male turkeys, are described. Single or, less commonly, multiple ulcers 16 to greater than 900 mm2 in size were located in the unfeathered breast skin over the anterior keel. Ulcer margins were raised, and the center was filled with a firmly adherent, hard scab. Microscopically, there was a sharp demarcation between the ulcer and adjacent hyperplastic epithelium. Vasculitis, necrosis of dermal vessels, mild to moderate heterophil infiltration, and fibrosis were found in the dermis. The characteristic granulomatous response to exudate seen in avian species was absent. Although bacterial colonies, foreign debris, and (rarely) fungi were found on the lesion surface, they were absent deep in the ulcer, suggesting they are not its cause. The lesion had no clinical effect on the turkey but was frequently trimmed at processing, resulting in downgrading and economic loss. There is no correlation between the size of "breast buttons" and occurrence of "breast blisters," an inflammation of the sternal bursa.

Indirect immunofluorescence, serum neutralization, and viremia responses of rhesus monkeys (Macaca mulatta) to Machupo virus.

Although indirect immunofluorescent antibody tests (IFAT) have been developed for several arenaviruses, none has been applied to the rhesus monkey model for Bolivian hemorrhagic fever (caused by the arenavirus Machupo). We infected eight rhesus monkeys with Machupo virus and bled them weekly for determination of viremia and for serum antibody detection by IFAT and serum neutralization (SN) testing. Viremia peaked day 14 post-inoculation (PI), when two of eight animals had low IFAT titers. At day 21 PI, the six surviving monkeys had elevated IFAT titers and diminished viremias. SN titers were not observed until 28 days PI, when three of four survivors had low titers. Results of the IFAT were available more rapidly than the SN, and detected increased serum antibody titers earlier than the SN. Acetone fixation did not completely inactivate BHF antigen spot slides.

Detection of turkey coronaviral enteritis (bluecomb) in field epiornithics, using the direct and indirect fluorescent antibody tests.

In Minnesota, efforts have been made over the past 10 years to eliminate turkey coronaviral enteritis (TCE, bluecomb) by controlled depopulation and decontamination with a rest period before restocking. In 1973, clinical observations indicated that bluecomb was restricted to one limited area in Minnesota. Five epiornithics occurred during late 1973 and 1974, involving 5 different farms in this limited geographic area. During 1975, 3 epiornithics of TCE were investigated, involving 185,000 turkeys in 17 flocks, of which approximately 17,000 died. Naturally infected turkeys representing 7 operations between 1973 and 1976 were examined by both the direct fluorescent antibody test and indirect fluorescent antibody test (IFAT). The direct fluorescent antibody test detected coronaviral antigen in intestinal tissues during the acute phase of the disease, and the IFAT was highly useful in detecting TCE serum antibodies of turkey flocks that had recovered and were potential carriers. Therefore, an IFAT surveillance program was instituted for replacement flocks on farms where clinical epiornithics of TCE had occurred in 1974 through 1976. Operation 5 involved TCE epiornithics over a 2-year period and illustrate the importance of complete depopulation with an intensive decontamination program.

Scanning electron, light, and immunofluorescent microscopy of coronaviral enteritis of turkeys (Bluecomb).

Intestinal sections from both experimental and field cases of turkey coronaviral enteritis (TCE) were examined by scanning electron microscopy and light microscopy through 10 days after inoculation and by a direct fluorescent antibody test for TCE through 12 days. Serums were collected for an indirect fluorescent antibody test for TCE through 160 days after inoculation. Lesions observed with the scanning electron microscopy were catarrhal enteritis with hemorrhage per diapedesis, epithelial desquamation, and villous atrophy which developed and regressed within 6 days after inoculation. Light microscopy demonstrated similar lesions, except that villus-to-crypt ratios remained depressed 10 days. The direct fluorescent antibody test demonstrated the presence of coronaviral antigen throughout the sampling period, and serum antibodies to TCE were present until at least 160 days, when the experiment was terminated.

Indirect fluorescent antibody test for the diagnosis of coronaviral enteritis of turkeys (bluecomb).

Frozen sections of intestine obtained from experimentally infected embryos were satisfactory as a suitable antigen in the indirect fluorescent antibody (IFA) test for detection of antibodies to turkey coronaviral enteritis (TCE). Antibodies were detected in infected turkeys at 14 days after infection and persisted for at least 107 days when the 1st experiment was concluded. Antibodies were also detected in infected turkeys at 9 days after infection and persisted for at least 160 days when the 2nd experiment was terminated. The IFA test may be of value as a rapid and economical screening method for TCE antibodies.

An outbreak of trematodiasis in domestic geese.

Losses greater than 3% were incurred in a large flock of domestic geese on summer pasture. Necropsy of the sick birds revealed no significant bacterial or viral isolates. The trematodes Echinostoma revolutum and Notocotylus attenuatus were present in considerable numbers, respectively in the small and large intestines.