Astrovirus: a cause of an enteric disease in turkey poults

Virus particles of 30 nm diameter and star-shaped morphology were detected in intestinal contents of turkey poults and were identified as astroviruses. Seventy-six intestinal samples from 65 commercial turkey flocks between 6 and 35 days of age were evaluated for the presence of astroviruses by immune electron microscopy. Astroviruses were frequently detected in intestinal samples from poults that had enteritis and diarrhea of undetermined etiology. Astroviruses were geographically widespread and were present in poults from all six operations evaluated. Astroviruses were inoculated into specific-pathogen-free poults. Changes observed in the gastrointestinal tract were: dilatated ceca containing yellowish frothy contents, gaseous fluid in the intestinal tract, and loss of tone of the intestinal tract (gut thinness). Poults experimentally inoculated with astrovirus gained significantly less body weight and absorbed significantly less D-xylose than uninoculated controls.     

Experimentally induced infections in turkeys with Cryptosporidium baileyi isolated from chickens

Oocysts of Cryptosporidium baileyi isolated from chickens were inoculated by different routes into 3 groups of turkey poults. Intratracheal inoculation of oocysts produced clinical signs of respiratory tract disease, deaths, and gross lesions of airsacculitis. Parasites developed in the microvillous border of the nasopharynx, larynx, trachea, bronchi, and air sacs. Oral and intracloacal inoculations of oocysts caused no deaths or clinical signs of disease, but did produce patent infections. Respiratory tract infections limited to the nasopharynx, larynx, and trachea occurred in 3 orally inoculated poults. Respiratory tract infections were not observed in intracloacally inoculated poults. The mode of inoculation did not influence the distribution of C baileyi in the digestive tract. The cloaca was parasitized in 100% of the birds with intestinal infections, and the bursa of Fabricius was parasitized in 72.7%.     

Pathogenicity of turkey coronavirus in turkeys and chickens

We designed this study to compare the replication potential of turkey coronavirus (TCV) and its effect in chickens and turkeys and to study the effect of singleand combined infection of turkey poults with TCV and astrovirus. We studied the pathogenicity of TCV in experimentally inoculated turkey poults and chickens by observing the dinical signs and gross lesions. Two trials were conducted with 1-day-old and 4-wk-old specific-pathogen-free turkey poults and chickens. One-day-old turkey poults developed diarrhea at 48 hr postinoculation. Poults euthanatized at 3, 5, and 7 days postinoculation had flaccid, pale, and thin-walled intestines with watery contents. The 4-wk-old turkeys had no clinical signs or gross lesions. One-day-old and 4-wk-old chicks developed no clinical signs or gross lesions although the TCV was detected in gut contents of the birds throughout the experimental period (14 days). In another experiment, mean plasma D-xylose concentrations in 3-day-old turkey poults inoculated with TCV, turkey astrovirus, or a combination of both viruses were significantly lower than in the uninoculated controls.     

Isolation and characterization of avian rotaviruses

Rotaviruses were isolated from intestinal contents obtained from flocks of turkey poults and pheasant poults with diarrhea and from different age groups of chickens showing various signs of intestinal disorders. The incorporation of 5 micrograms trypsin/ml in the inoculum and medium was essential for virus isolation in chicken kidney cells. All isolates were identified as rotaviruses by fluorescent-antibody technique using a National Institutes of Health reference rotavirus antiserum against human rotavirus strain "D," Type 2. Negative-staining and transmission electron microscopy showed the presence of rotavirus particles. Furthermore, polyacrylamide gel electrophoresis pattern of viral RNA segments of our isolates confirmed that they are rotaviruses. Seven-day-old turkey poults could be infected with turkey and chicken rotavirus isolates; in contrast, chicks of the same age were refractory.     

Reciprocal competitive exclusion of salmonella and Escherichia coli by native intestinal microflora of the chicken and turkey

Both the native intestinal microflora of chickens that protected chicks against salmonellae and Escherichia coli and native turkey intestinal microflora were evaluated for their reciprocal protective capacity in both species against Salmonella typhimurium and a pathogenic strain of E. coli. Nalidixic-acid-resistant forms of the S. typhimurium and E. coli strains were used in seeder-bird and individual-bird challenge tests. Reciprocal protection was provided by native chicken and turkey intestinal microflora in chicks and poults against S. typhimurium and the pathogenic strain of E. coli. The chicken and turkey microflora appeared to be equally effective in protecting the two species from S. typhimurium, but protection against E. coli was somewhat greater in the chicken than in the turkey.     

Pathogenicity of embryo-adapted serotype 2 OH strain of infectious bursal disease virus in chickens and turkeys

The pathogenicity of serotype 2 OH strain of infectious bursal disease virus (IBDV) to specific-pathogen-free (SPF) chicken embryos and 2-wk-old SPF chickens and turkey poults was investigated. The virus was pathogenic for chicken embryos after five passages as evidenced by pathologic changes in inoculated embryos. The embryo-adapted virus was not pathogenic for 2-wk-old SPF chickens and turkey poults as indicated by lack of clinical signs, gross or microscopic lesions in the bursa of Fabricius of inoculated birds. Bursa-to-body-weight ratios of the inoculated chickens and turkey poults were not significantly different from those of uninoculated controls. Virus-neutralizing antibodies to serotype 2 IBDV were detected in inoculated chickens and turkeys. Results of this study indicated that the embryo-adapted serotype 2 OH IBDV isolate that is pathogenic for chicken embryos is infectious but not pathogenic in chickens and turkeys.     

Mechanical transmission of turkey coronavirus by domestic houseflies (Musca domestica Linnaeaus)

Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised of turkey embryo-propagated virus (NC95 strain). TCV was detected in dissected crops from exposed flies for up to 9 hr postexposure; no virus was detected in crops of sham-exposed flies. TCV was not detected in dissected intestinal tissues collected from exposed or sham-exposed flies at any time postexposure. The potential of the housefly to directly transmit TCV to live turkey poults was examined by placing 7-day-old turkey poults in contact with TCV-exposed houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected in turkeys placed in contact with TCV-exposed flies at densities as low as one fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12 turkeys); however, increased rates of infection were observed with higher fly densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird). This study demonstrates the potential of the housefly to serve as a mechanical vector of TCV.     

Efficacy of different microbial preparations for controlling Salmonella colonisation in chicks and turkey poults by competitive exclusion.

1. Control by competitive exclusion of intestinal colonisation by Salmonella infantis was studied in domestic chicks and turkey poults given a commercial product developed for use with chickens, compared with two similar preparations containing intestinal microorganisms from turkeys. 2. Each type of material protected both avian species when given orally before challenge; the degree of protection depended at least as much on the type of preparation as its host origin.     

Marek's disease in turkeys: lack of protection by vaccination

Herpesvirus of turkeys, a highly effective vaccine against Marek's disease (MD) in chickens, was ineffective in protecting turkeys against MD. Another tissue-culture attenuated vaccine virus also protected chickens, but not turkeys, from MD. Intact and immunosuppressed turkey poults inoculated with herpesvirus of turkey developed a persistent viremia, but did not have detectable gross or microscopic lesions.     

Field studies with convalescent serum and infectious bursal disease vaccine to control turkey coryza

Convalescent serum given to 1-day-old poults delayed clinical signs of turkey coryza by several days and reduced mortality on infected farms. Turkey breeders immunized with cell-culture-adapted infectious bursal disease virus (IBDV) or turkey infectious bursal disease virus (TIBDV) had a marked increase in virus-neutralization (VN) antibody titers. The VN antibody titer was significantly higher in progeny poults than in poults from unimmunized breeders. Clinical turkey coryza and mortality was considerably less in poults from IBD- or TIBD-vaccinated breeders than in control poults. They also responded more favorably to hemorrhagic enteritis and fowl cholera vaccination.     

Identifying agent(s) associated with poult enteritis mortality syndrome: importance of the thymus

Poult enteritis mortality syndrome (PEMS), a highly infectious disease of young turkeys, causes serious financial losses to the turkey industry. Clinically, PEMS is defined by mortality profiles, diarrhea, growth depression, and immunosuppression. Although many viruses, bacteria, and parasites are found in PEMS-infected birds, the inciting agent remains unknown. Experimentally, PEMS can be reproduced by exposing na?ve poults to the intestinal contents from infected birds. Previous reports suggest that extraintestinal tissues fail to reproduce the disease. Histopathologic examination of tissues from PEMS-infected poults suggested that the thymus exhibited the earliest signs of pathology. On the basis of these observations, we hypothesized that the thymus harbors an agent(s) involved in PEMS. In these studies, na?ve turkey poults were orally inoculated with a bacteria-free filtrate composed of either the intestines and feces or the thymus from PEMS-infected birds and were monitored for clinical signs of PEMS. Poults exposed to a filtrate composed solely of the thymus from PEMS-infected birds exhibited diarrhea, growth depression, mortality, pathology, and, most importantly, immunosuppression similar to poults exposed to the intestinal filtrate. The results of this study suggest that the thymus of infected birds harbors the agent(s) that can reproduce a PEMS-like disease in turkey poults.     

Characterization of turkey coronavirus from turkey poults with acute enteritis.

The present study was to characterize turkey coronavirus associated with turkey poult enteritis and mortality. Intestinal contents or intestines from affected turkey poults and inoculated turkey embryos contained coronaviruses as revealed by electron microscopy or were positive for turkey coronavirus by immunofluorescent antibody assay. Sucrose density gradient ultracentrifugation of the virus-containing intestinal homogenate yielded two opalescent bands corresponding to the buoyant densities of 1.14-1.15 and 1.18-1.20 g/ml, respectively. Coronaviral particles from intestinal contents or the sucrose density gradient preparation were mainly spherical in shape and had envelope and central depression. They were surrounded by a fringe of regularly spaced petal-shaped projections attached to the particles by a short stalk. Purified viruses hemagglutinated rabbit erythrocytes with a titer of 16. Major protein bands of purified viruses analyzed by SDS-PAGE were located at 200, 100-110, 50-60, and 30-35 kDa. The patterns of protein bands were consistent with those of Minnesota or Quebec turkey coronavirus isolates. A 568 bp nucleotide fragment of turkey coronavirus spike protein gene was amplified from RNA of inoculated turkey embryo intestine or purified virus. Sequence analysis of the 568 bp PCR product revealed high degree of identity with the corresponding spike protein gene sequence of human and bovine coronaviruses. The results indicated that turkey coronavirus was associated with turkey poults with acute enteritis.     

Pathogenicity for chickens of a reovirus isolated from turkeys

A viral agent that was isolated from livers of commercial turkey poults that died at approximately two weeks of age was characterized as a reovirus. Experimental infection of day-old chickens with this reovirus isolate resulted in the development of tenosynovitis, hepatitis, and myocarditis. In vitro neutralization of the turkey reovirus isolate by antiserum against chicken reovirus correlated with in vivo protection of maternally immune chickens from day-old oral challenge with the turkey reovirus isolate.     

Pathogenesis of rotavirus infection in various age groups of chickens and turkeys: clinical signs and virology

Age-related susceptibility patterns of turkeys, broilers, and specific pathogen-free (SPF) White Leghorn chickens to experimentally induced infection with turkey or chicken rotavirus isolates were compared. The following determinants were evaluated: clinical signs, onset and duration of virus production, viral titers, involvement of intestinal villi in the replication of the virus, and the development of antibodies against the virus. Older turkeys and chickens were more susceptible than were their younger counterparts, turkeys were more susceptible than were broiler and White Leghorn chickens (regardless of age), and broiler chickens were slightly more susceptible than were age-matched White Leghorn chickens. Turkeys developed diarrhea, accompanied by high viral titers within 1 day after inoculation with virus. Viral antigen was found in the epithelial cells of the intestinal villi throughout the intestinal tract and some cells of the cecal tonsils. Antibodies could be detected as early as 4 to 5 days after inoculation. These findings were more pronounced in turkeys inoculated at 112 days of age than in birds inoculated at a younger age. Age-related susceptibility patterns were similar in White Leghorn and broiler chickens. Infection was subclinical in birds less than 56 days old, whereas older birds developed soft feces. Egg production in the White Leghorn chickens decreased after being inoculated with virus at 350 days of age.     

Intestinal cryptosporidiosis in turkeys in Iran

Naturally occurring cryptosporidiosis is reported in turkey poults suffering from diarrhoea and unthriftness in Iran. Histological and ultrastructural studies revealed high number of Cryptosporidium developmental stages mainly located in the mid and terminal portions of small intestine of the poults. Other portions of the intestinal tract were less frequently infected. Oocyst shedding was detected only in 29% of the histologically positive birds. Based on host species, clinical signs, pathology and tissue location of the parasites, Cryptosporidium meleagridis was most likely responsible for these infections. This parasite was also reported recently in a child with diarrhoea in Iran.     

Enteric disease in specific-pathogen-free turkey poults inoculated with a small round turkey-origin enteric virus

Four- and 5-day-old specific-pathogen-free turkey poults were inoculated orally or by contact exposure to a small round turkey-origin enteric virus. At days 4 and 8 postinoculation (PI), the orally inoculated poults had significantly lower body weight gains than control poults. Poults at day 4 (orally inoculated) and 5 (contact-exposed) PI had watery droppings, dilated thin-walled ceca filled with yellow foamy fluid, catarrhal small intestinal secretions, pale intestinal serosa, and mild lymphocytic enteritis. In addition, at day 4 PI, poults were lymphopenic, had intracytoplasmic crystalline arrays of 17.1 +/- 1.1 nm viral particles in the jejunal villar enterocytes, and had an 18-to-24-nm virus in intestinal contents. Analysis of morphometric data revealed mild shortening of villi in the duodenum and elongation of crypts in the duodenum and ileum during the late stage of the syndrome (day 8 PI). These findings suggest that the 18-to-24-nm virus can produce an enteric disease syndrome and that the acute clinical manifestation of this syndrome is not the result of morphologic change such as intestinal villus atrophy. The definitive identity of this 18-to-24-nm virus is not known; however, based on size and intracytoplasmic arrays of virus, it is most probably an enterovirus.     

Gastrointestinal transit times in normal and reovirus-inoculated turkeys

Brilliant pigment powder was used to measure minimum gastrointestinal transit times (GTT) in control and cloned-reovirus-inoculated turkey poults. Compared with controls, inoculated poults had longer GTT at 120 hr (P less than 0.05) but not at 24 and 72 hr after receiving a single oral dose of cloned reovirus. Reovirus inoculation was associated with failure to eat following a fasting period. Feces passed by reovirus-inoculated turkeys were more fluid and less well formed than normal.     

Pathogenesis of rotavirus infection in various age groups of chickens and turkeys: pathology

Various age groups of turkeys, White Leghorn chickens, and broiler chickens were inoculated with turkey rotavirus strain Tu-2 or with chicken rotavirus Ch-2, and the development of rotavirus-induced lesions were evaluated macroscopically and microscopically (light microscopy and scanning electron microscopy). Morphometric evaluations were conducted to determine morphologic changes in the villi of infected turkeys. Macroscopic lesions that were found in turkeys, but not in chickens, consisted of pallor of the intestinal tract and distension of the cecum with frothy or nonfrothy fluid contents. Histologic lesions in turkeys consisted of basal vacuolation of enterocytes, separation of enterocytes from the lamina propria (with subsequent desquamation), villus atrophy accompanied by widening of the lamina propria, scalloping of the villus surface, fusion of the villi, and leukocytic infiltration of the lamina propria. Scanning electron microscopy indicated roughened villus surfaces, distortion of the normal morphologic features of the villi, and loss of microvilli in cells located on the tips of the villi. Most of the lesions disappeared by 8 days after inoculation. Results of the morphometric evaluations indicated that the crypt length had increased and the villus-to-crypt ratio had significantly decreased, compared with that of noninoculated control turkeys. Broilers greater than or equal to 21 days old and White Leghorn chickens greater than or equal to 35 days old had minimal leukocytic infiltration of the lamina propria and minimal loss of microvilli in cells located on the tips of the villi. The loss of microvilli was more extensive in chickens greater than or equal to 119 days old than in younger birds. Generally, turkeys 1 to 112 days old developed more severe lesions than did chickens, and lesions were more pronounced in turkeys at 112 days of age.     

Efficacy and safety of a cell-culture live virus vaccine for hemorrhagic enteritis of turkeys: laboratory studies

Poults free from hemorrhagic enteritis (HE) antibody were vaccinated by gavage at 1 day or 2 weeks of age with a live HE vaccine virus that had been propagated in a Marek's disease (MD)-induced B-lymphoblastoid cell line of turkey origin. Vaccinated and unvaccinated poults were challenged with a virulent HE virus at various times postvaccination. One hundred tissue-culture-infectious doses of the vaccine virus per poult were sufficient to induce a serological response as well as to protect poults against HE lesions and mortality. Vaccinated poults were protected against the disease as early as 1 week and as late as 8 weeks PV. The vaccine was efficacious by several routes of application. The vaccine virus spread horizontally from vaccinated to contact-exposed poults, as indicated by seroconversion and resistance of contact-exposed poults to challenge. The vaccine had no detectable harmful effects on the humoral immune response to particulate antigens or on weight gain of vaccinated poults. The vaccine proved to be free from MD virus, as indicated by the absence of MD lesions and antibody in 8-week-old chickens inoculated intra-abdominally with the vaccine at hatching. These findings indicate that the cell-culture-propagated HE vaccine is efficacious and safe.     

Viral agents associated with outbreaks of diarrhea in turkey flocks in Quebec.

The relative importance of various enteric viruses associated with diarrhea of turkey poults was investigated by an evaluation of specimens received since 1982. Specimens originated from one to eight week old turkey poults, with mild to severe diarrhea, from 114 flocks in 42 commercial operations located in southern Quebec. The acute phase of enteritis occurred usually in poults between two and four weeks of age. Clarified intestinal contents were examined by direct electron microscopy and enzyme immunoassays. Enzyme-linked immunosorbent assays were performed with antisera to bovine rotavirus group antigen, avian reovirus types 1 to 5, and the prototype strain of the turkey enteric coronavirus. The presence of viruses could be demonstrated by electron microscopy in 55.3% of the specimens, and at least five different viruses were incriminated either alone or in combination. The coronavirus was by far the most common enteric virus with a prevalence of 47.5%. By enzyme-linked immunosorbent assay, rotavirus, reovirus and turkey coronavirus were detected in 14.5%, 18.1% and 61.4% of the specimens, respectively. By electron microscopy, 56.6% of these cases were positive for at least one virus.