Infected Hens Research Articles

Examination of Mycobacterium avium subsp. avium distribution in naturally infected hens by culture and triplex quantitative real time PCR

Mycobacterium avium subsp. avium (MAA) is the etiologic agent of avian tuberculosis, a chronic contagious disease described in a wide variety of domestic and wild bird species. The aims of this study were to assess the advantages of triplex quantitative real time PCR (qPCR) in comparison with culture testing for distribution of MAA in the organs of hens displaying varying degrees of clinical symptoms of the disease. From one small flock of ten hens and one cock with a history of weight loss, 98 tissue samples were examined in total. Pathological lesions were observed in six hens from which two were clinically ill. A total of 12 samples were positive by culture and 16 were positive by IS901 and IS1245 qPCR, confirming MAA infection. In conclusion, qPCR was a faster and more reliable alternative method in comparison with conventional culture analysis. Due to the detection of MAA in the muscle tissue of one hen, consumption of under cooked meat originating from infected fowl could pose a threat to immunosuppressed individuals.

Study the effect of Ivermectin on infected hens with lice

In the present study conducted on effect of Ivermectin drug on infected hens with lice. the data showed that, this drug have a poisonous effected on lice parasite during the first three days of treatment. At the same time have no toxisicity on treated hens.. Also the ivermectin is not negative effect on the eggs production of the infected and treated hens. There are only 8 eggs for 25 hens injected the drug ,but the rate increased to 19 eggs, and the size of the hens become larger after one week from injection the drug.The study was show a positive effect for drug in parasite and its eggs , and the blood parameters were returned to normal values in infected hensafter treatment with drug. Additionally , were found the each of hemoglobin values for infected hens befor treatment were 10-14 mg/dl ,sugar 200-250 mg/100ml and alkaline phosphates enzyme 1.5-3.5 K.A.S/100ml ,but after treatment the values above were different where the hemoglobin values 10-12 mg/dl , sugar 185-240 mg/100ml and levels of alkaline phosphates enzyme was 1.3-4.5 K.A.S/100ml.

Colonization of Avian Reproductive-Tract Tissues by Variant Subpopulations of Salmonella Enteritidis

Leghorn hens were infected with Salmonella Enteritidis cultures of known genomic content and subpopulation characteristics to determine comparative abilities to colonize the avian reproductive tract. Group 1 received phage-type (PT)4 22079, which is a dimorphic subpopulation that can both contaminate eggs and form biofilm. Group 2 received a 90:10 mixture of monomorphic PT13a strains 21027 and 21046, which produce biofilm or contaminate eggs, respectively. Group 3 received a 10:90 mixture of the same two PT13a strains, respectively. Trials were repeated three times and a total of 30 hens per treatment group were infected. Dosage was by oral gavage and was calculated as 8.6 +/- 2.01 X 10(7) colony-forming units per hen. Liver, spleen, and three different sections of oviduct (ovary, upper oviduct, and lower oviduct) were cultured per bird. Results were that all three groups had livers and spleens that were mostly positive (90.0% and 94.4% of 270 hens cultured, respectively). Reproductive-tract organs yielded 75 positives from 270 hens (27.8%), and treatment groups ranged from a low of 6.7% to a high of 76.7% positive cultures in any one trial. There was no significant difference between the numbers of positive reproductive-tract samples between treatment groups due to variance. These results suggest that the status of the reproductive tract at the time of infection may impact recovery of culture-positive tissue and contribute to variance. It is suggested that Salmonella Enteritidis cultures that vary in subpopulation composition have subtle differences in colonization of reproductive tissue that contribute to variance in egg contamination. Culture of non-reproductive-tract organs such as the liver and spleen was overall more reliable for detection of infected hens. The spleen was especially useful for detection because of its small size. Further research is needed to determine how sex hormones influence the infection pathway that results in egg contamination.

Evaluation of the Use of Different Solvents to Extract the Four Main Components of Yinqiaosan and Their In Vitro Inhibitory Effects on Influenza-A Virus

High-performance liquid chromatography coupled with an ultraviolet detector was used to quantitatively determine the amount of caffeoylquinic acid, arctium lappa glycoside, aurantiamarin and forsythin present in five solvent extracts (water, 30% ethanol, 50% ethanol, 70% ethanol and 95% ethanol) of Yinqiaosan (YQS). The calibration curves of the four components were linear (r(2) > 0.998) over the concentration range of 0.9-151.5 microg/mL. This method showed good repeatability with relative standard deviations of less than 2.9% and mean recoveries of 91.3-100.5%. We established the relative amounts of each of the four main ingredients in YQS for all five solvent extracts. The direct inhibitory effects of the five YQS extracts on influenza-A virus in vitro and the therapeutic effects on infected embryonated hen eggs were evaluated. YQS extracted in 50% ethanol and used at concentrations of 500 mg/mL and 250 mg/mL exerted the greatest therapeutic effect in infected embryonated hen eggs and was significantly superior to ribavirin (p < 0.05). Therefore, the 50% ethanol extract of YQS seems to be the most effective for the inhibition of influenza-A virus. Based on these results, further studies are warranted to evaluate the use of YQS extracts as a possible therapy for influenza.

Alfalfa as a nutritive modulator in maintaining the innate immune response during the molting process

Forced molting of laying hens increases enteric foodborne pathogens in the reproductive tract, leading to contaminated eggs and progeny of infected hens. Currently, we lack a complete understanding of how conditions such as molting affect the immune system. Previous reports have shown that alfalfa is effective in inducing a molt as well as in producing protection against Salmonella Enteritidis organ invasion. Our laboratory has also shown that immune functions are significantly reduced during molting. The present investigation evaluates a specific parameter of immune function, heterophil function, during an induced molt in hens fed alfalfa. Three replicate experiments used hens older than 65 wk of age that were divided into 6 groups of 12 hens each and placed in individual laying cages. Two weeks before dietary changes, hens were placed on an 8L:16D photoperiod that continued for the 12-d experiment. Peripheral blood samples were taken from hens on d 0, 2, 6, and 12 of molt. Hens were randomly placed into 3 treatment groups: nonfed hens, fully fed hens, and alfalfa-fed hens. To evaluate heterophil functions, the production of an oxidative burst as well as cellular degranulation assays were performed. In addition, total and differential peripheral blood leukocyte counts were performed. When compared with the nonfed control, alfalfa-fed birds showed significantly (P < 0.05) higher oxidative burst and degranulation activities. The data confirm previous observations that heterophil functions are significantly decreased in nonfed birds and the data show that birds fed alfalfa had numerically increased heterophil functions over a 12-d molting period when compared with heterophils of nonfed controls. Commercial integrators should consider using alfalfa when developing new molting programs.

Comparison of the conventional culture, the manual fluorescent MGIT system and the automated fluorescent MGIT 960 culture system for the detection of Mycobacterium avium ssp. avium in tissues of naturally infected hens

Different methods for the detection of Mycobacterium avium ssp. avium (MAA) in naturally infected hens were compared. They included the conventional culture method (solid Herrold's and Stonebrink media and liquid Sula medium) and newly developed liquid culture systems, the manual mycobacteria growth indicator tube (M-MGIT) and the fully automated BACTEC MGIT 960 system (A-MGIT). 152 tissues originating from 15 naturally infected hens have been processed. The overall detection rates (percentage of positive cultures from the number of positive cultures determined by all the methods together) were 60, 70 and 76 % for the conventional media, M-MGIT and A-MGIT systems, respectively, the mean time of mycobacteria detection being 32.6, 17.6 and 14.6 d, respectively. The lowest contamination rate (2.0 %) was found in A-MGIT compared with M-MGIT (4.6 %) and conventional media (10.4 %).

Effect of Prior Passage Through Laying Hens on Invasion of Reproductive Organs by Salmonella enteritidis

The colonization of reproductive tissues in infected laying hens is a pivotal stage in the production of contaminated eggs that can transmit Salmonella enteritidis infections to humans. In an earlier study, a series of passages through infected laying hens increased the frequency at which an S. enteritidis isolate was deposited inside eggs. The present study evaluated the effect of in vivo passage of an S. enteritidis isolate on its ability to invade to internal tissues, including three different regions of the reproductive tract. In each of three trials, a group of laying hens was infected orally with a PT13a strain of S. enteritidis (prepared from a separate stock culture each time). After internal organ samples were removed from this first passage group for culturing at 7 days post-inoculation, an S. enteritidis isolate from the upper oviduct of an extensively infected hen was used to infect another (second passage) group of hens in each trial. The overall frequency of S. enteritidis isolation from internal organs increased between passages in only one of the three trials and no increases were observed between passages in the frequency of S. enteritidis recovery from any of the three reproductive tissue sites. Therefore, passage of S. enteritidis through infected chickens did not always select for either higher overall invasiveness or for a higher ability to colonize reproductive organs in the present study.

Antibody and inflammatory responses in laying hens with experimental primary infections of Ascaridia galli

Ascaridia galli, an intestinal nematode that affects hens and other domestic and wild birds, causes economic losses in avian exploitations. The present work shows that A. galli stimulates a strong antibody response as well as an intense inflammatory reaction, in the intestinal mucous of experimentally infected Lohmann Brown laying hens. IgG antibodies against soluble extracts of A. galli embrionated eggs and adult worms, were detected in both blood and yolks eggs from infected hens during a period of 105 days after the infection. This indicates that hens transfer to their offspring a part of the IgG antibodies produced when they become infected. The antigens responsible for the stimulation of specific IgG were molecules of 30–34, 44–54 and 58–90 kDa, while in the yolk eggs of infected hens a reactivity directed against antigens of molecular weight ( M w) lower than 50 kDa was detected. Histology revealed traumatic lesions with leukocyte infiltration, and inflammation of the intestinal wall of the infected hens after 105 days of initial infection. The possible influence of the immune and inflammatory response on the population dynamics of the parasite is discussed.

Rat-to-Elephant-to-Human Transmission of Cowpox Virus

Rat-to-Elephant-to-Human Transmission of Cowpox Virus

Diagnostic testing of different stages of avian tuberculosis in naturally infected hens (Gallus domesticus) by the tuberculin skin and rapid agglutination tests, faecal and egg examinations

Avian tuberculosis (ATBC) is a significant cause of morbidity and mortality in birds in zoos and breeding establishments. The primary sources of &lt;I&gt;Mycobacterium avium&lt;/I&gt; subsp. &lt;I&gt;avium (MAA)&lt;/I&gt; of serotypes 1, 2 and 3 are infected animals (esp. birds), who shed &lt;I&gt;MAA&lt;/I&gt; in different ways and thus contaminate the environment. The first aim of this work was to compare the efficiency of the diagnostic methods that are routinely used for the diagnosis of ATBC (skin test, serology and culture of faeces and eggs) in naturally infected hens with different levels of infection. The second aim was to determine the excretion rate of &lt;I&gt;MAA&lt;/I&gt; in faeces and eggs. The tuberculin skin test gave a positive result in nine (42.9%) infected hens of which four (57.1%) and one (14.3%) were heavily and slightly infected hens, respectively. A positive serological response to &lt;I&gt;MAA&lt;/I&gt;-b antigen (water bird isolate of serotype 1) was observed in five (23.8%) and to &lt;I&gt;MAA&lt;/I&gt;-p antigen (pig isolate serotype 2) in seven (33.3%) hens. No correlation between serological and skin-test data was found. The results show that both techniques, serological and skin-test data are inadequate for the diagnosis of ATBC. In consecutively euthanized hens, with heavy infection and tuberculous lesions, serological positivity was significant (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) in comparison with slightly infected hens lacking tuberculous lesions. Faecal culture detected &lt;I&gt;MAA&lt;/I&gt; in 50 (29.8%) of 168 samples collected for eight days before euthanasia. &lt;I&gt;MAA&lt;/I&gt; excretion in faeces was intermittent, but significantly (&lt;I&gt;P&lt;/I&gt; &lt; 0.01) higher in heavily infected hens. No mycobacteria were detected in any of the 43 examined eggs, which implies that the shedding of &lt;I&gt;MAA&lt;/I&gt;and/or transmission of ATBC through eggs may not be frequent events.

Interspecies and intraspecies transmission of triple reassortant H3N2 influenza A viruses

The triple reassortant H3N2 viruses were isolated for the first time from pigs in 1998 and are known to be endemic in swine and turkey populations in the United States. In 2004, we isolated two H3N2 triple reassortant viruses from two turkey breeder flocks in Ohio and Illinois. Infected hens showed no clinical signs, but experienced a complete cessation of egg production. In this study, we evaluated three triple reassortant H3N2 isolates of turkey origin and one isolate of swine origin for their transmission between swine and turkeys. Although all 4 viruses tested share high genetic similarity in all 8 genes, only the Ohio strain (A/turkey/Ohio/313053/04) was shown to transmit efficiently both ways between swine and turkeys. One isolate, A/turkey/North Carolina/03, was able to transmit from pigs to turkeys but not vice versa. Neither of the other two viruses transmitted either way. Sequence analysis of the HA1 gene of the Ohio strain showed one amino acid change (D to A) at residue 190 of the receptor binding domain upon transmission from turkeys to pigs. The Ohio virus was then tested for intraspecies transmission in three different avian species. The virus was shown to replicate and transmit among turkeys, replicate but does not transmit among chickens, and did not replicate in ducks. Identifying viruses with varying inter- and intra-species transmission potential should be useful for further studies on the molecular basis of interspecies transmission.

Mycobacterium avium subsp. avium distribution studied in a naturally infected hen flock and in the environment by culture, serotyping and IS 901 RFLP methods

Mycobacterium avium subsp. avium ( MAA) of serotype 2 and genotype IS 901+ and IS 1245+ was cultured from 21 naturally infected hens ( Gallus domesticus) from one smallholder aviary. From a total of 330 samples taken from hens, 124 mycobacteria were detected. Out of which MAA was detected in 103 (35.7%) of 288 tissues, in 4 (19.0%) of 21 swabs of cloacae and in 9 (42.9%) of 21 faeces samples, 8 other conditionally pathogenic mycobacterial species were also isolated. Tuberculous (TB) lesions were found in the liver, spleen and intestinal organs of seven hens. The isolates of MAA ( n = 58) from 16 infected hens (7 with TB lesions and 9 without TB lesions) were found to be of 3 IS 901 RFLP types AE ( n = 48), AD ( n = 4) and E ( n = 6), where these MAA isolates are highly virulent to hens. Mixed infections with IS 901 RFLP types (AE and AD) and (AE and E) were also evident in seven hens. From a total of 35 examined environmental samples, 23 mycobacterial isolates were detected. Out of which four (17.4%) MAA isolates of IS 901 RFLP type AE and 19 (82.6%) other isolates of conditionally pathogenic mycobacteria were detected. The finding of identical IS 901 RFLP types from both tissues and faecal isolates confirms that infected domestic hens are the principal source of infection for other susceptible hosts and lead to the contamination of the surrounding environment. The presence of different IS 901 RFLP types in tissue isolates may indicate the repeated incidence of MAA infection and the occurrence of polyclonal infection.

Egg whites from eggs of chickens infected experimentally with avian hepatitis E virus contain infectious virus, but evidence of complete vertical transmission is lacking

Avian hepatitis E virus (HEV) is genetically and antigenically related to human HEV. Vertical transmission of HEV has been reported in humans, but not in other animals. In this study, we showed that avian HEV could be detected in chicken egg-white samples. Subsequently, avian HEV in egg white was found to be infectious, as evidenced by the appearance of viraemia, faecal virus shedding and seroconversion in chickens inoculated with avian HEV-positive egg white, but not in chickens inoculated with HEV-negative egg white. To further assess the possibility of vertical transmission of avian HEV, batches of embryonated eggs from infected hens were hatched, and hatched chicks were monitored for evidence of avian HEV infection. However, no virus was detected in samples collected from the hatched chicks throughout this study, suggesting that avian HEV could not complete the vertical transmission cycle. The possible implications of our findings are also discussed.

Influence of Ascaridia galli infections and anthelmintic treatments on the behaviour and social ranks of laying hens ( Gallus gallus domesticus)

In the present study, the effects of an experimental Ascaridia galli infection and anthelmintic treatment on the behaviour and social status of laying hens of two different lines were studied. Sixty white (Lohmann LSL; LSL) and 60 brown (Lohmann Brown; LB) hens were reared under helminth-free conditions. The hens of each line were divided into four groups. The birds in two of the groups were artificially infected with 250 embryonated A. galli eggs at an age of 27 weeks. The other two groups were kept as uninfected controls. One infection and control group was dewormed at 38 weeks of age and slaughtered 4 weeks later, contemporary with the other animals. Individual faecal Ascaridia egg counts (FEC) were performed 11 weeks post-infection (p.i.). Body weights, laying performance and egg weights were recorded regularly. Blood was taken to measure testosterone levels. The worm burdens established in the intestines were counted in the infected not treated group after slaughtering. In addition, 15 behavioural parameters were recorded by focal animal observation ( n = 10 per group) of one infection (plus anthelmintic treatment) and one control group, according to the time-sampling method throughout the experiment. All agonistic interactions within the groups were recorded simultaneously on an ongoing basis, thereby allowing the calculation of an individual social rank index. The following results were obtained: • Mean FEC and worm burden were higher ( p < 0.01) in the LSL hens than in the LB hens, but their performances were not different ( p > 0.05) from the controls. • Infections with A. galli resulted in significant behavioural changes in both lines as the infected birds showed a higher food intake and lower locomotion activity during the prepatent and patent periods. After anthelmintic treatment, food intake decreased and locomotion increased. • Behavioural changes were more pervasive in the infected LSL hens, as these hens also showed changes in ground pecking and nesting activity not only during the prepatent and patent periods, but also after anthelmintic treatment. • Social rank did not significantly change as a consequence of A. galli infection, but the infection groups of both lines had a tendency to display more agonistic activity than the non-infected controls. • Serum testosterone values only increased significantly in the LSL hens during the patent period compared to the controls. • No significant correlations were apparent between serum testosterone level, parasitic parameters, social status and/or aggressiveness in any of the groups. This study showed that even sub-clinical A. galli infections and their anthelmintic treatment can have an impact on animal behaviour.

Influenza virus-like particles elicit broader immune responses than whole virion inactivated influenza virus or recombinant hemagglutinin

Influenza virus is a highly infectious respiratory pathogen that results in severe morbidity and mortality. The current licensed trivalent vaccine formulations in the U.S. are made from virus grown in allantoic fluid from infected hen eggs that is then chemically inactivated and split into subunit components. These vaccines elicit antibodies, primarily to the viral hemagglutinin (HA), which are efficacious in healthy adults, but are limited in protecting high risk individuals, such as the elderly and immunocompromised. To address the need for improved influenza vaccines and the limitations of egg-based manufacturing, we have engineered an influenza virus-like particle (VLP) as a new generation of non-egg or non-mammalian cell culture-based candidate vaccine against influenza infection. VLPs, based on the A/Fujian/411/2002 (H3N2) isolate, were purified from the supernatants of Spodoptera frugiperda Sf9 insect cells following infection of baculovirus vectors encoding an expression cassette comprised of only three influenza virus structural proteins, hemagglutinin (HA), neuraminidase (NA), and matrix (M1). Mice or ferrets were vaccinated intramuscularly with VLPs in a dose sparing experiment, based on HA concentration (3 μg–24 ng), and the immune responses were compared to responses elicited in animals vaccinated with recombinant HA (rHA) or inactivated whole influenza virions (WIV). All vaccinated animals had high titer anti-HA antibodies regardless of the vaccine immunogen and animals vaccinated with the highest doses of VLPs (3 μg and 600 ng) also had antibodies against NA. Purified rHA elicited primarily IgG1 antibodies, which is indicative of a T helper (Th) type 2 response, whereas mice vaccinated with the VLPs or WIV were associated with a dominant Th1 immune response (IgG2a and IgG2b). Interestingly, VLPs elicited antibodies that recognized a broader panel of antigenically distinct H3N2 viral isolates compared to rHA or WIV in a hemagglutination-inhibition (HAI) assay.

Ultrastructural study of infectious bronchitis virus infection in infundibulum and magnum of commercial laying hens

The infundibulum and magnum of the oviduct were examined in hens in full lay which were infected with two Australian strains of infectious bronchitis virus (IBV). The ultramicroscopic changes in the infundibulum and magnum were compared with control hens which had eggs at different positions in the oviduct. The ciliated and granular cells of the surface epithelia and secretory epithelial cells of the tubular glands were the target cells of IBV. No pathological changes were recorded during 2–8 days post-infection (p.i.). Patchy loss of cilia occurred at 10–14 days p.i. Between 16 and 24 days p.i., there was no cilia loss and lymphoid nodules were observed in the muscularis layer of the infundibulum and magnum of some hens from both infected groups. Virus particles were detected mostly in the rough endoplasmic reticulum (RER) and Golgi complex between 10 and 12 days p.i. Cytopathology was noticed in various cell organelles between the 10th and 14th days p.i. There was an increase in RER deposits in infected cells, irrespective of egg position in the oviduct. The magnum was more affected than the infundibulum. Cellular changes were more severe in the infundibulum and magnum of T-infected hens as compared to N1/88-infected hens. Eggs with watery whites which were laid by infected hens could be attributed to cytopathological changes in the granular epithelial cells and tubular gland epithelial cells of the magnum resulting in reduced synthesis of albumen proteins. IBV can cause pathology in parts of the fully functional oviduct which may persist up to the 30th day p.i. However, both the challenge strains of IBV can cause a small number of hens to cease production. Loss of cilia in both the infundibulum and magnum pose a potential threat of secondary bacterial infection and also may affect fertility in breeder hens.

Campylobacter sp in organs and meconium of day-old broiler chicks derived from naturally infected breeder hens

Campylobacter sp is an important agent that causes foodborne infection, particularly in food of poultry origin. Therefore, the efficient control of the transmission routes in chicken farms is of outmost importance to prevent it from spreading. In chicken farms, the main transmission route of this microorganism is horizontal, as the vertical route continues to be the object of inconclusive researches. The objective of this study was to verify the presence of Campylobacter sp in breeder hens, meconium, and other organs of day-old chicks derived from these breeders in order to obtain information on vertical transmission. Microbiological analyses were performed, using cloacal swabs from 279 breeder hens. Positive breeders were segregated, and the presence of Campylobacter sp. was verified in their progeny by analyzing 117 meconium samples; 36 heart, liver and spleen samples (pool of 3 day- old chicks per sample), and 34 intestine samples (pool of 3 chickens in each sample). The analysis of the 279 breeder hens showed that 39 (13.97%) were positive for Campylobacter sp, using the cloacal swab method. The meconium and the organs of day-old chicks were not positive. The physiological characteristics of breeder hens, of eggs, and of Campylobacter sp favor the entrance of bacteria and their survival inside the eggs, and therefore, this probably is the contamination route of day-old chicks. However, chick meconium and organs were negative in the present experiment, indicating that the vertical way of transmission is a rare event.

Comparison of Salmonella enterica Serovar Enteritidis Levels in Crops of Fed or Fasted Infected Hens

Long-term feed withdrawal has been shown to increase ileocecal intestinal colonization and fecal shedding of Salmonella enterica serovar Enteritidis in challenged hens. Less information is available regarding effects of fasting on crop colonization. Two trials were conducted to compare effects of 14-day feed withdrawal vs. full feed on crop colonization in hens challenged with Salmonella Enteritidis. The levels of Salmonella Enteritidis in the crops of fasted hens were significantly higher than in nonfasted hens on days 3 and 10 and days 3, 9, and 16 postinfection (PI) in trials 1 and 2, respectively. Fecal shedding of Salmonella Enteritidis was significantly increased in the fasted hens on day 10 PI in trial 1. Analysis of crop IgA anti-Salmonella Enteritidis lipopolysaccharide levels in crop lavage samples of hens in trial 1 revealed a humoral response PI in both treatment groups with no significant differences, although peak response for fasted hens occurred 1 wk later. Histologic evaluation of hematoxylin and eosin-stained crop sections from trial 1 birds revealed mild to moderate heterophilic infiltration within the crop lamina propria (LP) or LP and epithelium of nonfasted infected hens at 24 and 96 hr PI. In comparison, heterophils in crops of fasted hens infected at this time point were sparse, indicating a possible diminished heterophil response in the fasted birds. Multifocal areas of tissue inflammation, as indicated by marked heterophil infiltration, with necrosis and sloughing of epithelium, were observed in crops from fasted hens at day 11 PI (14th day of feed withdrawal) but not in the fed groups. This severe heterophilic inflammation was observed in both challenged and nonchallenged fasted hens, suggesting that some factor other than Salmonella Enteritidis was responsible. These results indicate that feed withdrawal can have a dramatic effect on the integrity of the crop and its ultimate response to infection.

Detection of Antibodies in Serum and Egg Yolk following Infection of Chickens with an H6N2 Avian Influenza Virus

Active serologic surveillance programs to detect avian influenza viruses (AIVs) in table egg-laying chickens have been initiated by several states as a response to the economic threat posed by these viruses. Most outbreaks of avian influenza in domestic poultry are caused by mildly pathogenic AIVs. In the study reported here, infection by an H6N2 AIV was used as a model of mildly pathogenic AIV infections in egg-type chickens. The total number of eggs laid by 5 control hens was 619 or 0.904 eggs/day/hen, whereas the total number laid by 10 infected hens was 1,018 or 0.743 eggs/day/hen. The difference in egg production between the 2 groups was not statistically significant (P = 0.38). Anti-influenza antibodies were monitored by use of an agar gel immunodiffusion test and an ELISA for a period of 20 weeks after inoculation. Antibodies in serum developed sooner, peaked at higher levels, and remained at higher levels than did antibodies found in egg yolk, as indicated by ELISA results. For infected chickens, the correlation between serum and egg yolk ratios was 0.66. Serum samples would appear to be preferable to egg yolk samples for surveillance programs intended to identify chicken flocks that may have been infected by an AIV weeks or months before samples are collected.

Persistence of Mycoplasma synoviae in hens after two enrofloxacin treatments and detection of mutations in the parC gene

The ability of Mycoplasma synoviae, an avian pathogen, to persist despite fluoroquinolone treatments was investigated in hens. Groups of Mycoplasma-free hens were experimentally infected with the M. synoviae 317 strain and treated twice with enrofloxacin at the therapeutic dose. The results show that the two treatments did not have any influence on this strain of M. synoviae recovery from tracheal swabs. Mycoplasmas were isolated from tracheal swab cultures, but not from inner organs such as the liver or spleen, suggesting that this strain of M. synoviae was not able to cross the mucosal barrier to disseminate throughout the host. A significant increase of the resistance level to enrofloxacin of five re-isolated mycoplasma clones, was observed after the second treatment. This increase was associated in two clones to a Ser81-->Pro substitution, found in the ParC quinolone-resistance determining region (QRDR) of DNA topoisomerase IV. This is the first time that a mutation in a gene coding for topoisomerase IV is described in M. synoviae after in vivo enrofloxacin treatments in experimentally infected hens.