Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection

In a previous study, turkey coronavirus (TCV) and enteropathogenic Escherichia coli (EPEC) were shown to synergistically interact in young turkeys coinfected with these agents. In that study, inapparent or mild disease was observed in turkeys inoculated with only TCV or EPEC, whereas severe growth depression and high mortality were observed in dually inoculated turkeys. The purpose of the present study was to further evaluate the pathogenesis of combined TCV/EPEC infection in young turkeys and determine the role of these agents in the observed synergistic interaction. Experiments were conducted to determine 1) effect of EPEC dose, with and without concurrent TCV infection, and 2) effect of TCV exposure, before and after EPEC exposure, on development of clinical disease. Additionally, the effect of combined infection on TCV and EPEC shedding was determined. No clinical sign of disease and no attaching and effacing (AE) lesions characteristic of EPEC were observed in turkeys inoculated with only EPEC isolate R98/5, even when turkeys were inoculated with 10(10) colony forming units (CFU) EPEC (high dose exposure). Only mild growth depression was observed in turkeys inoculated with only TCV; however, turkeys inoculated with both TCV and 10(4) CFU EPEC (low dose exposure) developed severe disease characterized by high mortality, marked growth depression, and AE lesions. Inoculation of turkeys with TCV 7 days prior to EPEC inoculation produced more severe disease (numerically greater mortality, significantly lower survival probability [P < 0.05], increased frequency of AE lesions) than that observed in turkeys inoculated with EPEC prior to TCV or simultaneously inoculated with these agents. Coinfection of turkeys with TCV and EPEC resulted in significantly increased (P < 0.05) shedding of EPEC, but not TCV, in intestinal contents of turkeys. These findings indicate that TCV infection predisposes young turkeys to secondary EPEC infection and potentiates the expression of EPEC pathogenicity in young turkeys.     

The relationship between the anticoccidial effects of clindamycin and the development of immunity in the Eimeria pragensis/mouse model of large intestinal coccidiosis

The therapeutic effect of clindamycin on Eimeria pragensis (E. pragensis) infection in C57BL/6 mice was demonstrated by suppression of oocyst production and the appearance of degenerated endogenous stages of parasite in the intestine. Short-term clindamycin treatment, from 1 to 4 days or 4 to 8 days post infection (pi) at a dose of 800 mg/kg/day was effective to reduce clinical symptoms, oocyst production and schizogonic development. Interestingly, the short-term treatment schedules allowed the development of a measurable degree of protective immunity to challenge infection in the treated mice. In contrast, clindamycin treatment for the full 12 days period, which almost completely inhibited clinical symptoms and oocyst output, prevented the full development of protective immunity in the treated mice. All these data indicate that clindamycin is efficacious as an anti-eimerian agent and that both early and late endogenous developmental stages of E. pragensis exert a deep influence on the development of effective immunity to challenge infection.     

Efficacy of diclazuril against turkey coccidiosis in dose-titration studies

Diclazuril, a new anticoccidial drug, was tested for its efficacy in turkeys against single Eimeria infections. Dose-titration studies indicated that diclazuril at dosages of 0.1, 0.5, 1, and 2 ppm was highly effective against the major pathogenic species-E. adenoeides, E. gallopavonis, and E. meleagrimitis-in terms of weight gain and suppression of lesions, abnormal droppings, and oocyst shedding.     

Efficacy of diclazuril against turkey coccidiosis in a floor-pen experiment

Diclazuril, a new anticoccidial drug, was tested for its efficacy in turkeys against mixed Eimeria infections. A floor-pen trial indicated that diclazuril at dosages of 0.5 ppm and 1 ppm in the feed was highly effective against the major pathogenic species E. adenoeides, E. gallopavonis, and E. meleagrimitis in suppressing intestinal and cecal lesions and oocyst shedding. Weight gain and feed conversion improved, particularly at 1 ppm.     

Investigation of Neospora sp. and Toxoplasma gondii antibodies in mares and in precolostral foals from Parana State, Southern Brazil

Infections with Eimeria parasites can lead to severe diarrhoea with considerable clinical and economic consequences in first-year grazing stock. To identify and characterise the cause of diarrhoea observed during previous years, 164 animals on 14 dairy farms in northwestern Germany were included in this study. The calves were physically and parasitologically examined prior to turnout and until 21 days post turnout (d.p.t.). Mean animal weights decreased from 194.9 kg at the start to 189.3 kg bodyweight at the end of the study. In all herds, oocyst counts were very low prior to turnout and increased after the calves had been kept on pasture for at least 7 days. On Day 9 post turnout, 90% and at the end of the study (21 d.p.t.) 70% of all animals showed Eimeria-positive faecal samples. During the course of the study, 79 (48.2%) animals passed faecal samples with more than 100,000 oocysts per gram. The predominant species identified was Eimeria alabamensis, which accounted for more than 83% of the oocysts counted. These parasitological findings matched the clinical observations. Diarrhoea was found in 130 (79.3%) of the study animals. At 5d.p.t. and thus prior to the rise of faecal oocyst counts, a significant increase in diarrhoea was recorded. Calves showing diarrhoea excreted statistically significantly more often over 100,000 E. alabamensis oocysts per gram faeces (0.28; p = 0.0002) than calves without diarrhoea. Diarrhoea was also found during significantly more study days in animals with high oocyst counts (0.39; p = 0.0001). These data indicate that in endemic areas first-year grazing calves must be considered at risk to develop clinical coccidiosis due to E. alabamensis infection during the first 2-3 weeks post turnout.     

Tissue sulfonamide concentration and correlation in turkeys

Nineteen hen turkeys (10 to 12 kg each) were used in a feeding study to determine sulfadimethoxine and sulfaquinoxaline concentrations in blood serum, liver, and skeletal muscle, as well as the respective ratios at selected withdrawal intervals. Two feeds were prepared by use of premixes to achieve 60 mg of sulfadimethoxine/kg and 100 mg of sulfaquinoxaline/kg, respectively. Each of the medicated feeds was given to 9 turkeys for 7 days. The turkeys were then fed nonmedicated feed at intervals from 24 to 56 hours and were slaughtered. One turkey was used as control. The serum/liver and serum/muscle ratios for sulfaquinoxaline were 60 to 70% higher than for sulfadimethoxine. However, the liver/muscle ratio for both sulfonamides was equivalent, approximately 3. Disposition of both sulfonamides approximated first-order pharmacokinetics. The calculated half-life of sulfadimethoxine was half that of sulfaquinoxaline, approximately 16 vs 30 hours. The coefficients of variation in the serum/tissue ratios for both sulfonamides were between 13% and 25% for serum/liver and less than 15% for serum/muscle, indicating excellent potential for using serum as a predictor of actionable concentrations of sulfonamide residues.     

Immunity and effect of clopidol/methyl benzoquate and robenidine before and after weaning on rabbit coccidiosis in the field

For 15 months the anticoccidial effect of 200 ppm clopidol/methyl benzoquate and of 50 ppm robenidine, and the development of immunity against five different species of Eimeria were followed in a closed rabbit population. In unmedicated rabbits, oocyst output decreased progressively with increasing age to a very low level in animals older than four months, but none of the species present disappeared completely in adult animals. No clinical symptoms nor mortality from coccidiosis was noted in reproduction stock. In field conditions E magna and E perforans seemed to induce the weakest resistance, whereas a more marked resistance has been found for E intestinalis and E irresidua. E media appeared to have an intermediate position. Robenidine reduced oocyst output of E magna, E intestinalis, E irresidua, E media and E perforans significantly, whereas clopidol/methyl benzoquate reduced oocyst output of the latter four species only and was least active against E magna. Both drugs also reduced coccidiosis-induced mortality significantly. Medication only before weaning had no distinct influence on coccidial infection, or on mortality by coccidiosis after weaning; nor did those parameters differ significantly between continuously medicated rabbits and rabbits medicated after weaning only. As reproductive stock is protected by immunity, this makes the necessity of medicating does and bucks with anticoccidials questionable in intensive or semi-intensive reproduction systems.     

Outbreak of cutaneous form of poxvirus on a commercial turkey farm caused by the species fowlpox

The present report documents the occurrence of a poxvirus infection in commercial meat turkeys. The affected farm had six flocks, with a total of 11,680 birds at different ages; birds from two of these flocks were affected. The clinical picture was characterized by severe epithelial lesions and proliferations on the head and neck regions as reported for the cutaneous form of poxvirus infection. Except for these lesions, no adverse clinical signs or gross pathologic lesions were observed. Only a low number of birds was affected (n = 20) and no increase of mortality could be seen. Bacteriologic investigations from the lesions revealed multiresistant Staphylococcus aureus. Eosinophilic inclusions (Bollinger bodies) in histologic examinations in the cytoplasm of keratinocytes were noticeable. Typical pox virions were demonstrated by electron microscopy, and poxvirus was isolated on the chorioallantoic membrane of specific-pathogen-free chicken eggs. Further identification of the poxvirus species was carried out by PCR and sequencing, revealing an infection with the species fowlpox. Layers in vicinity of the turkey farm that also were affected by fowlpox were considered as potential source of infection. Although it is assumed that avian poxviruses are strongly species specific, the present case report reinforces the changing picture of poxvirus infections in turkeys. Furthermore, it supports the assumption of previous data that fowlpox virus has to be seen as recently emerging pathogen in turkeys.     

Exacerbation of Chlamydophila psittaci pathogenicity in turkeys superinfected by Escherichia coli

Both Chlamydophila psittaci and Escherichia coli infections are highly prevalent in Belgian turkeys and therefore they both might contribute to the respiratory disease complex observed in turkeys. C. psittaci can infect turkeys within the first week of age, even in the presence of maternal antibodies. However, the first C. psittaci outbreaks occur mostly at the age of 3 to 6 weeks, the period when also E. coli infections appear on the farms. Therefore, we examined in this study the pathogenicity of an E. coli superinfection on C. psittaci predisposed turkeys. Turkeys were infected with C. psittaci, E. coli or with C. psittaci followed by E. coli. Simulating the impact of an E. coli infection during the acute phase or the latent phase of a C. psittaci infection, turkeys received E. coli at 1 or 5 weeks post C. psittaci infection, respectively. E. coli superinfection during the acute phase of C. psittaci infection increased C. psittaci excretion and stimulated chlamydial replication in the respiratory tract resulting in exacerbated clinical disease. Interestingly, E. coli superinfection during the latent phase of C. psittaci infection induced chlamydial replication, leading to increased C. psittaci-specific antibody titres. In addition, chlamydial predisposition gave higher E. coli excretion compared with turkeys that had only been infected with E. coli. Overall, the present study clearly demonstrates the pathogenic interplay between C. psittaci and E. coli resulting in more severe respiratory disease.     

Experimental and field sulfaquinoxaline toxicosis in Leghorn chickens

Mortality of 47% occurred in a commercial flock of 20-week-old leghorn pullets treated with 0.05% sulfaquinoxaline in the feed. The drug was given for 2-3 days, removed for 2 days, and fed again for 2-3 days. Gross lesions consisted of disseminated hemorrhages, bone marrow pallor, a variety of changes suggesting septicemia, and overwhelming bacterial infection. Experimental feeding of sulfaquinoxaline at 0.05% in the feed at a schedule of 3 days on, 3 days off, and 2 days on successfully reproduced the essential features and gross lesions of the field toxicosis. Mortalities of 32.5% and 43.5% were observed in sulfaquinoxaline-treated groups. A high incidence of gangrenous dermatitis occurred in chickens with the experimental toxicosis, but it was not observed in the field case.     

Pathogenic interactions between Chlamydophila psittaci and avian pneumovirus infections in turkeys

Both Chlamydophila psittaci and avian pneumovirus (APV) are highly prevalent in Belgian turkeys and might contribute to the respiratory disease complex observed in turkeys. Initial outbreaks of chlamydiosis occur mostly at the age of 4-8 weeks, often accompanied by an APV infection in APV non-vaccinated farms. Regardless APV vaccination, breakthroughs of APV infection from 8 weeks on do occur, a period when also a second C. psittaci infection appears. Therefore, this study examined the pathogenicity of an APV superinfection in C. psittaci predisposed turkeys. Turkeys were infected with C. psittaci, APV or with C. psittaci followed by APV. Simulating the impact of an APV infection during the acute phase or latent phase of a C. psittaci infection, turkeys have been infected with APV at 1 and 5 weeks post C. psittaci infection, respectively. APV infection during the acute phase of a C. psittaci infection aggravates the severity of clinical signs, macroscopic lesions, pharyngeal APV excretion and histological tracheae lesions. In contrast, no clear interaction could be established after APV infection in latently C. psittaci infected specific pathogen-free (SPF) turkeys. This study clearly demonstrates the exacerbating role of APV during acute C. psittaci infection, which can play an important role in the respiratory disease complex of turkeys.     

Effect of infection of turkeys with haemorrhagic enteritis adenovirus isolate on the selected parameters of cellular immunity and the course of colibacillosis

The aim of the study was to determine the effect of a Polish low-virulence isolate of haemorrhagic enteritis adenovirus (HEV) on the immune system in turkeys and on the course of colibacillosis in birds infected under laboratory conditions. Turkeys were infected per os with HEV at the dose of 10(4.3)EID50/mL and with E. coli (APEC) (serotypes 078:K80:H9) at the dose of 4x10(9)CFU/mL by injection to the thoracic air sac. The birds infected with the HEV were infected with the APEC either simultaneously or after 5 days. Five days after HEV infection, the percentages of subpopulations of the CD3+CD4+ and CD3+CD8alpha+ T cells and the IgM+ B cells were determined in blood and spleens of the HEV-infected turkeys and in the control (uninfected) birds. The course of colibacillosis was more severe in turkeys infected with the APEC 5 days after infection with the HEV than in those infected with the HEV and APEC simultaneously and than in those infected only with APEC. Five turkeys out of the 18 infected with the APEC 5 days after infection with HEV, died. Their body weights were statistically significantly lower with higher FCR values 41 days after the infection in comparison to turkeys in the other groups. A considerable decrease in the percentage of the T and B cells subpopulations in the blood were found in turkeys infected with the HEV and while the percentage of CD3+CD4+ T cells subpopulation in the spleen increased significantly, the contribution of the CD3+CD8alpha+ T cells and IgM+ B cells subpopulations were decreased. These changes in the immune system of turkeys, occurring 5 days after infection with the HEV, made them more susceptible to infection with the APEC.     

The clinical, pathological and microbiological outcome of an Escherichia coli O2:K1 infection in avian pneumovirus infected turkeys

The purpose of this study was to evaluate the effect of an Escherichia coli infection in avian pneumovirus (APV)-infected turkeys. One group of 2-week-old specific pathogen-free (SPF) and two groups of 3-week-old conventional (CON) turkeys were inoculated oculonasally with virulent APV subtype A alone, with E. coli O2:K1 alone or with both agents at varying intervals (1, 3, 5 or 7 days) between the two inoculations. The birds were followed clinically and examined for macroscopic lesions at necropsy. Titres of APV were determined in the turbinates, trachea, lungs and air sacs. The number of E. coli O2:K1were assessed in the turbinates, trachea, lungs, air sacs, liver and heart. In both SPF and CON turkeys, dual infection resulted in an increased morbidity and a higher incidence of gross lesions compared to the groups given single infections, especially with a time interval between APV and E. coli inoculations of 3 and 5 days. APV was isolated from the respiratory tract of all APV-infected groups between 3 and 7 days post inoculation. E. coli O2:K1 was isolated only from turkeys that received a dual infection. It was recovered from the turbinates, trachea, lungs, heart and liver. These results show that APV may act as a primary agent predisposing to E. coli colonization and invasion.     

Experimental inoculation of wild turkeys (Meleagris gallopavo) with Mycobacterium bovis

Although avian species are known to be susceptible to infection with Mycobacterium spp. organisms, much remains unknown about the susceptibility of birds to infection with M. bovis. The objective of this current study was to determine if wild turkeys (Meleagris gallopavo) can be infected with M. bovis when inoculated by the oral or intratracheal route. Six turkeys were orally inoculated and another six were inoculated via the trachea with a high dose of M. bovis, 1 x 10(5) CFU/ml. Six turkeys were sham-inoculated controls. Two turkeys from each treatment group were sacrificed on days 30, 60, and 90 postinoculation. There were no gross or microscopic lesions consistent with mycobacteriosis in the 23 inoculated turkeys over the 90-day duration of this study. Fecal cultures were also consistently negative for M. bovis when sampled before inoculation and on days 1, 30, and 60 postinoculation. Two intratracheally inoculated turkeys were positive for M. bovis in visceral tissues at 30 days postinoculation. However, this finding was only indicative of passive persistence of mycobacteria in the tissues and not of infection, as there were no attendant lesions or clinical compromise to support infection. Thus, it can be concluded that young wild turkeys are resistant to infection with M. bovis and, therefore, pose minimal threat as reservoir or spillover hosts for this organism.     

Effects of clopidol on sporulation and infectivity of Eimeria tenella oocysts

Feed additive anticoccidials currently used in Japan were examined for possible effects on oocyst sporulation of Eimeria tenella. Monensin, salinomycin, lasalocid, amprolium plus ethpabate, amporolium plus ethopabate plus sulfaquinoxaline, clopidol, or nicarbazin were given to chickens continuously via the feed at the recommended use level or one-half of that level. Oocysts discharged in feces 7-8 days post inoculation (PI) were collected and aerated for sporulation. Low sporulation rate was noted, when clopidol at 62.5 mg kg-1 was given from 4 to 7 days PI. These oocysts were as infective as oocysts from controls, based on weight gain, feed efficiency, gross lesion score of cecae, and oocyst count 7 days PI. The results of the study indicated that the second schizogony and gametogony are vulnerable to clopidol, as evidenced by oocyst sporulation, but infectivity of these sporulated oocysts was not affected.     

Experimental and serologic observations on avian pneumovirus (APV/turkey/Colorado/97) infection in turkeys

An avian pneumovirus (APV) was isolated from commercial turkeys in Colorado (APV/Colorado) showing clinical signs of a respiratory disease. The results of virus neutralization and indirect fluorescent antibody tests showed that the APV/Colorado was partially related to APV subgroup A but was unrelated to APV subgroup B. Turkeys experimentally inoculated with the APV/Colorado were observed for signs, lesions, seroconversion, and virus shedding. Thirty-six 7-wk-old turkeys were distributed into three groups. Eighteen turkeys were inoculated oculonasally with APV/Colorado, six were placed in contact at 1 day postinoculation (DPI), and 12 served as noninoculated controls. Tracheal swabs and blood samples were collected at 3, 5, 7, 10, 14, and 21 DPI. Tissues were collected from three inoculated and two control turkeys on aforementioned days for pathologic examination and APV isolation. Inoculated turkeys developed respiratory disease, yielded APV at 3, 5, and 7 DPI, and seroconverted at 10 DPI. Contact turkeys yielded APV at 7 and 10 DPI. No gross lesions were observed in the turbinates, infraorbital sinuses, and trachea. However, microscopic examination revealed acute rhinitis, sinusitis, and tracheitis manifested by congestion, edema, lymphocytic and heterophilic infiltration, and loss of ciliated epithelia. The inflammatory lesions were seen at 3 DPI and became extensive at 5 and 7 DPI. Active regenerative changes in the epithelia were seen at 10 and 14 DPI. Serologic survey for the presence of antibodies in commercial turkeys (24,504 sera from 18 states) and chickens (3,517 sera from 12 states) to APV/Colorado showed seropositive turkeys in Minnesota, North Dakota, and South Dakota and no seropositive chickens. This report is the first on the isolation of an APV and APV infection in the United States.     

Effects of Bordetella avium infection on the pulmonary clearance of Escherichia coli in turkeys

Thirty-six 1-day-old turkeys were inoculated intranasally with Bordetella avium (BA) strain 838. Noninoculated hatchmates (n = 36) were housed separately. At 2 and 4 weeks of age, 15 inoculated (BA+) and 15 noninoculated (BA-) turkeys were exposed to an aerosol of virulent Escherichia coli. The remaining six BA+ turkeys and six BA- turkeys were used as controls (ie, not exposed to E coli). Turkeys were necropsied on postaerosolization days 0 (immediately after aerosolization), 1, 3, 5, and 7. Lung and tracheal specimens were collected from each turkey for bacterial quantitation and histologic examination. A 1-ml blood sample was collected for detection of bacteremia. Numbers of E coli in lung specimens from 2- and 4-week-old turkeys were not significantly different between BA+ and BA- groups (pooled data over time); however, numbers of E coli isolated from tracheal specimens were significantly greater in BA+ turkeys than those in BA- turkeys. Although the incidence of pulmonary abcesses and E coli bacteremia was greater in 2-week-old turkeys than in 4-week-old turkeys, the incidence was not different between BA+ and BA- turkeys. At both ages, air sacculitis developed more often and was more severe in BA+ turkeys than in BA- turkeys. Hyperplastic bronchus-associated lymphoid tissue was found more often in BA+ turkeys than in BA- turkeys and appeared to be the first site of heterophil infiltration after E coli aerosolization.     

Sudden death in turkeys with perirenal hemorrhage: pathological observations and possible pathogenesis of the disease.

A pathological study was conducted on 32 turkeys that died of sudden death with perirenal hemorrhage syndrome. Turkeys were selected from routine necropsy cases in a diagnostic laboratory. A higher incidence was observed in heavy tom turkeys. In addition to the characteristic gross lesions of perirenal hemorrhage, splenomegaly, and pulmonary congestion, turkeys in most cases had a hypertrophic cardiopathy. Microscopic lesions included moderate-to-marked acute passive congestion of all tissues examined (32/32), severe perirenal hemorrhage (32/32), and splenic lymphoid depletion (25/32). Changes in the thyroid follicular epithelium of most birds suggested an increased glandular activity. No lesions suggestive of arterial hypertension were observed. Adenoviral infection was detected in only four of 32 birds. Bacteriological cultures revealed no significant pathogen. Results suggest that sudden death in turkeys with perirenal hemorrhage is caused by an acute congestive heart failure consecutive to a hypertrophic cardiopathy. The perirenal hemorrhage would be a consequence of a severe passive congestion in kidneys.     

Characterization of a strain of Eimeria meleagridis from the turkey

An isolate of Eimeria meleagridis Tyzzer, 1927 was obtained by harvesting oocysts from the ceca of a turkey from northwest Arkansas and a pure line was established by infecting birds with a single oocyst. Oocysts were first produced in the ceca of infected birds from 102 to 108 hr after inoculation and were of similar size (mean length X width, 24.9 X 17.0 microm) to those of Eimeria adenoeides Moore and Brown, 1951 and Eimeria gallopavonis Hawkins, 1952. The line was identified as E. meleagridis based upon the development of large schizonts in the midintestine, and small schizonts in the ceca. Two generations of large schizonts were found 48 and 72 hr after infection, and at least two generations of small schizonts were found from 60 to 108 hr after infection. An inoculum of 2 X 10(5) oocysts was found to cause a significant reduction in weight gain from days 0-3 and 0-6 after infection, suggesting that the significance of this species of Eimeria as a pathogen of turkeys should be reassessed.     

Effects of exogenous iron on Escherichia coli septicemia of turkeys

The effect of inoculation with Escherichia coli on serum iron concentrations of turkeys and the effect of exogenous iron, as ferric ammonium citrate, on E coli septicemia in turkeys were determined. Inoculation of air sacs with E coli produced hypoferremia in 18-day-old turkeys. Administration of iron with E coli significantly (P less than 0.01) increased mortality, frequency and degree of bacteremia, and severity of lesions in inoculated turkeys, compared with those in turkeys given E coli but not given iron. Similar results were seen whether iron was inoculated at the same location as E coli or at a different location.