Evaluation of lung function in pigs either experimentally or naturally infected with Chlamydiaceae

Large Farm Animals Used for Research Purposes: A Survey on Purchase, Housing and Hygiene Management

Simple Summary

The use of farm animals, especially in biomedical research, has increased in recent years. As clear recommendations for the purchase, housing and health monitoring of these animals (sheep, goat, cattle and pigs) are still missing, many institutes have developed their own strategies and protocols to face the challenges associated with the use of farm animals. This may influence the comparability of research results and increase data variances, thus increasing animal use that contradicts the obligation to apply the 3Rs principle required in Directive 2010/63 EU and our national animal welfare law. Therefore, this survey aimed to define the current state of the art in research institutes working with farm animals in order to develop recommendations for the purchase, housing and hygiene management of farm animals used for research purposes; to refine the work with farm animals; and to reduce variability and, therefore, the number of animals required.

Abstract

Background: Farm animals (FAs) are frequently used in biomedical research. Recommendations for the purchase, housing and health monitoring of these animals (sheep, goats, cattle and pigs) are still missing, and many institutes have developed their own strategies and protocols to face the challenges associated with the use of farm animals. This may influence the comparability of research results and increase data variances, thus increasing animal use that contradicts the obligation to apply the 3Rs principle of reduction, refinement and replacement required in Directive 2010/63 EU and the German animal protection law. Methods: A survey was conducted to define the current state of the art in research institutes working with pigs, and large and small ruminants. Results: The results of the survey clearly show that there are no uniform procedures regarding the purchase, housing and hygiene management of farm animals contrary to small laboratory animals. The facilities make purpose-bound decisions according to their own needs and individual work instructions and implement their own useful protocols to improve and maintain the health of the animals. Conclusion: This survey was the first step to filling the gaps and identifying the status quo and practical applied measures regarding the purchase and hygiene monitoring of FAs in order to improve animal welfare and scientific validity.

Analysis of fluoroquinolones in dusts from intensive livestock farming and the co-occurrence of fluoroquinolone-resistant Escherichia coli

Fluoroquinolones are important therapeutics in human and veterinary medicine. This study aimed to retrospectively analyse sedimentation dusts from intensive-livestock-farming barns for fluoroquinolones and investigate the association between resistant Escherichia coli and the detected drugs. Sedimentation-dust samples (n = 125) collected (1980–2009) at 14 barns of unknown-treatment status were analysed by HPLC and tandem-mass spectroscopy to detect enrofloxacin, ciprofloxacin, marbofloxacin, and difloxacin. Recent microbiological data were included to investigate the relationship between fluoroquinolone presence and fluoroquinolone-resistant E. coli. Fifty-nine dust samples (47%) from seven barns contained fluoroquinolone residues. Up to three different fluoroquinolones were detected in pig and broiler barns. Fluoroquinolone concentrations ranged from 10-pg/mg to 46-ng/mg dust. Fluoroquinolone-resistant E. coli were isolated from four barns. Of all the dust samples, 22% contained non-susceptible isolates. Non-susceptible isolate presence in the dust was significantly associated (p = 0.0283) with detecting the drugs, while drug detection increased the odds (4-fold) of finding non-susceptible E. coli (odds ratio = 3.9877, 95% CI: 1.2854–12.3712). This retrospective study shows that fluoroquinolone usage leads to dust contamination. We conclude that farmers and animals inhale/swallow fluoroquinolones and fluoroquinolone-resistant bacteria due to drug application. Furthermore, uncontrolled drug emissions via air exhausted from the barns can be assumed.

Seventy Years of Chlamydia Vaccine Research - Limitations of the Past and Directions for the Future

Chlamydia is a major bacterial pathogen that infects humans, as well as a wide range of animals, including marsupials, birds, cats, pigs, cattle, and sheep. Antibiotics are the only treatment currently available, however, with high rates of re-infection, there is mounting pressure to develop Chlamydia vaccines. In this review, we analyzed how Chlamydia vaccine trials have developed over the past 70 years and identified where future trials need to be focused. There has been a strong bias toward studies targeting C. muridarum and C. trachomatis within mice and a lack of studies matching chlamydial species to their end target host. Even though a large number of specific antigenic targets have been studied, the results from whole-cell vaccine targets show slightly more promising results overall. There has also been a strong bias toward systemic vaccine delivery systems, despite the finding that mucosal delivery systems have shown more promising outcomes. However, the only successful vaccines with matched chlamydial species/infecting host are based on systemic vaccine delivery methods. We highlight the extensive work done with mouse model trials and indicate that whole cell antigenic targets are capable of inducing an effective response, protecting from disease and reducing shedding rates. However, replication of these results using antigen preparations more conducive to commercial vaccine production has proven difficult. To date, the Major Outer Membrane Protein (MOMP) has emerged as the most suitable substitute for whole cell targets and its delivery as a combined systemic and mucosal vaccine is most effective. Finally, although mouse model trials are useful, differences between hosts and infecting chlamydial strains are preventing vaccine formulations from mouse models to be translated into larger animals or intended hosts.

Prevalence of Chlamydial Infections in Fattening Pigs and Their Influencing Factors

Chlamydial infections in pigs are associated with respiratory disease, diarrhea, conjunctivitis and other pathologies. The aim of this study was to define the prevalence of Chlamydiaceae in Swiss fattening pigs by applying sensitive and specific detection methods and to correlate prior antibiotic treatment and farm related factors with differences in prevalence. Conjunctival and fecal swabs were collected from 636 pigs in 29 Swiss fattening pig farms with and without antibiotic treatment, at the beginning and the end of the fattening period. The swabs were screened by real-time PCR for Chlamydiaceae. For the chlamydial detection and species-identification, a DNA-microarray analysis was performed. All farms were positive for Chlamydiaceae with 94.3 and 92.0% prevalence in fecal swabs as well as 45.9 and 32.6% in conjunctival swabs at the first and second time points, respectively. Antibiotic treatment could not clear the infection on herd level. Potential contact with wild boars was a significant risk factor, while hygiene criteria did not influence chlamydial prevalence. A correlation of chlamydial positivity to diarrhea, but not to conjunctivitis was evident. Chlamydia suis was the predominant species. Mixed infections with C. suis and C. pecorum were common, with a substantial increase in C. pecorum positivity at the end of the fattening period, and this finding was associated with ruminant contact. C. abortus was detected in one conjunctival swab. In this study, C. suis inhabited the intestinal tract of nearly all examined pigs, implying a long-term infection. C. pecorum was also common and might be transmitted to pigs by ruminants.

Intratracheal infection as an efficient route for testing vaccines against Chlamydia abortus in sheep

Pregnant ewes have been widely used to test vaccines against Chlamydia abortus. However, this model entails many disadvantages such as high economic costs and long periods of pregnancy. The murine model is very useful for specific studies but cannot replace the natural host for the later stages of vaccine evaluation. Therefore, a non-pregnant model of the natural host might be useful for a vaccine trial to select the best vaccine candidates prior to use of the pregnant model. With this aim, two routes of infection were assessed in young non-pregnant sheep, namely, intranasal (IN) and intratracheal (IT). In addition, groups of non-vaccinated sheep and sheep immunised with an inactivated vaccine were established to investigate the suitability of the model for testing vaccines. After the experimental infection, isolation of the microorganism in several organs, with pathological and immunohistochemical analyses, antibody production assessment and investigation by PCR of the presence of chlamydia in the vagina or rectum were carried out. Experimental IT inoculation of C. abortus induced pneumonia in sheep during the first few days post-infection, confirming the suitability of the IT route for testing vaccines in the natural host. The course of infection and the resulting pathological signs were less severe in vaccinated sheep compared with non-vaccinated animals, demonstrating the success of vaccination. IN infection did not produce evident lesions or demonstrate the presence of chlamydial antigen in the lungs and cannot be considered an appropriate model for testing vaccines.

Relationship between clinical signs and results of impulse oscillometry in pigs originating from the field

The aim of the present study was to assess the contribution of clinical data to the variability of impulse oscillometric test results observed previously by Püllen et al. (2014). Fifty-eight German hybrid pigs from 29 different herds with unknown respiratory status were examined in the context of routine diagnostics as part of herd health service. Routine clinical examination was extended to a total set of 29 parameters, representing detailed clinical signs of the respiratory system, and to lung function testing applying the impulse oscillometry system (IOS). The resulting linear relationship between clinical data and variables of pulmonary mechanics had a mean r(2) of 0.52. Clinical parameters predominantly representing the lower respiratory tract closely correlated with established impulse oscillometric indices reflecting peripheral airways. Because of a restricted relationship between pulmonary functional disorders and clinical data, additional diagnostic methods are required to reveal the proportion of variance undefined by clinical examination.

Evaluation of impulse oscillometry in pigs of unknown disease status originating from the field

The aim of this study was to assess impulse oscillometry as a method to characterise lung function in 58 German hybrid pigs from 29 different herds of unknown respiratory status. The variability of repeated lung function measurements increased significantly after the sixth run and therefore the average of the first six runs was used for analysis. The presence of peripheral respiratory alterations in some pigs was indicated by the negative frequency dependence of the 95th percentile of respiratory resistance (Rrs), with highest values at 3 Hz and the sharp drop of respiratory reactance (Xrs) across the whole frequency range (3-15 Hz). Respiratory resistance and reactance were negatively correlated. Reactance area was correlated with (1) Rrs at 3, 5 and 10 Hz; (2) Xrs at 3, 5, 10 and 15 Hz; (3) the frequency dependence of resistance compared between 3 and 5 Hz (R3-R5), 5 and 10 Hz (R5-R10), and 5 and 15 Hz (R5-R15); and (4) tidal volume. High repeatability and low intra-individual variability of impulse oscillometry indicate that this method is a promising tool for advanced characterisation of the pulmonary system of pigs and has potential for use for herd health monitoring.

Respiratory function and pulmonary lesions in pigs infected with porcine reproductive and respiratory syndrome virus

Pulmonary dysfunction was evaluated in pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV, isolate VR-2332) and compared to clinical and pathological findings. Infected pigs developed fever, reduced appetite, respiratory distress and dullness at 9 days post-inoculation (dpi). Non-invasive pulmonary function tests using impulse oscillometry and rebreathing of test gases (He, CO) revealed peripheral airway obstruction, reduced lung compliance and reduced lung CO-transfer factor. PRRSV-induced pulmonary dysfunction was most marked at 9-18 dpi and was accompanied by a significantly increased respiratory rate and decreased tidal volume. Expiration was affected more than inspiration. On histopathological examination, multifocal areas of interstitial pneumonia (more severe and extensive at 10 dpi than 21 dpi) were identified as a possible structural basis for reduced lung compliance and gas exchange disturbances.

Chlamydiaceae in cattle: commensals, trigger organisms, or pathogens?

Epidemiological data indicate that infection of cattle with chlamydiae such as Chlamydophila (C.) pecorum, C. abortus, C. psittaci and Chlamydia suis, is ubiquitous with mixed infections occurring frequently. The apparent lack of association between infection and clinical disease has resulted in debate as to the pathogenic significance of these organisms, and their tendency to sub-clinical and/or persistent infection presents a challenge to the study of their potential effects. However, recent evidence indicates that chlamydial infections have a substantial and quantifiable impact on livestock productivity with chronic, recurrent infections associated with pulmonary disease in calves and with infertility and sub-clinical mastitis in dairy cows. Data also suggest these infections manifest clinically when they coincide with a number of epidemiological risk factors. Future research should: (1) use relevant animal models to clarify the pathogenesis of bovine chlamydioses; (2) quantify the impact of chlamydial infection at a herd level and identify strategies for its control, including sub-unit vaccine development; and (3) evaluate the zoonotic risk of bovine chlamydial infections which will require the development of species-specific serodiagnostics.

Recurrence of Chlamydiasuis infection in pigs after short-term antimicrobial treatment

The effect of short-term antimicrobial treatment on natural excretion of Chlamydia suis in rectal swabs and C. suis and Chlamydophila psittaci in nasal swabs was investigated in 47 clinically normal piglets by quantitative real-time PCR. Pigs were treated IM with 4 mg/kg enrofloxacin for 5 days (n = 22) or 2.5mg/kg enrofloxacin for 3 days followed by 100mg/mL tiamulin (n = 25). Antimicrobial treatment reduced the number of pigs positive for chlamydiae and the quantity of chlamydial DNA in positive swabs for a few days, but chlamydial excretion recurred in both groups. Short-term antimicrobial treatment at dosages recommended for treatment of other bacterial infections in pig herds was not effective in eliminating naturally occurring subclinical chlamydial infection in pigs.

Characterisation of acid-base abnormalities in pigs experimentally infected with Chlamydia suis

This study characterises the acid-base abnormalities in pigs experimentally infected with Chlamydia suis (Henderson-Hasselbalch equation and Constable's simplified strong ion equation). Eight pigs were challenged with the respiratory pathogen C. suis and four pigs served as non-infected controls. Pigs were monitored from 7 days before challenge to 8 days post-inoculation. Clinical examination was performed twice daily and venous blood samples were collected every two days. Blood-gas analysis, haemoxymetry, serum biochemical analysis and electrophoresis were performed in order to characterise the acid-base derangement. Aerosol challenge with C. suis resulted in severe acid-base disturbance characterised by acute respiratory acidosis and strong ion (metabolic) acidosis secondary to anaerobic metabolism and hyper L-lactataemia. Maximal changes were seen at day 3 post-inoculation when severe clinical signs of respiratory dysfunction were evident. The results of the study provide new information regarding the pathophysiology of respiratory infection caused by C. suis and the applicability and diagnostic utility of different approaches for assessing acid-base status in pigs.

The porcine lung as a potential model for cystic fibrosis

Airway disease currently causes most of the morbidity and mortality in patients with cystic fibrosis (CF). However, understanding the pathogenesis of CF lung disease and developing novel therapeutic strategies have been hampered by the limitations of current models. Although the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) has been targeted in mice, CF mice fail to develop lung or pancreatic disease like that in humans. In many respects, the anatomy, biochemistry, physiology, size, and genetics of pigs resemble those of humans. Thus pigs with a targeted CFTR gene might provide a good model for CF. Here, we review aspects of porcine airways and lung that are relevant to CF.

A clinically silent respiratory infection withChlamydophilaspp. in calves is associated with airway obstruction and pulmonary inflammation

This study was aimed at evaluating functional and inflammatory consequences of persistent chlamydial infections on the respiratory system in clinically inconspicuous calves aged 2-7 months. Thirteen calves persistently infected with Chlamydophila (C.) abortus and/or C. pecorum (Chl+) were compared to 12 calves without chlamydial infections (Chl-). In order to evaluate lung function, 36 non-invasive impulse oscillometry tests were performed per animal within 6 months. The group of chronically infected animals was distinguished by significantly higher peripheral airway resistance (indicating peripheral airway obstruction), significantly higher respiratory rates, and significantly higher minute volumes of ventilation. At the age of seven months, all calves were necropsied, broncho-alveolar lavage fluid (BALF) was obtained ex vivo, and lungs were examined histologically. Significantly higher concentrations of total protein and 8-iso-prostane (8-IP), as well as higher activities of matrix metalloprotease 2 were measured in BALF samples of Chl+ calves. Histologically, markedly activated bronchus-associated lymphoid tissue (BALT) causing partial obstruction of bronchiolar lumina was found in the apical pulmonary lobes of Chl+ calves. Chlamydial DNA was detected in the lung tissue of 7 out of 13 Chl+ calves by real-time PCR. In conclusion, respiratory chlamydial infection appeared to be associated with chronic inflammation of the lungs and airways. Despite the lack of clinical symptoms, pulmonary dysfunctions persisted in calves until the age of seven months. Data obtained in this study provide new insight illustrating the impact of nearly ubiquitous subclinical infections on the respiratory system.

Impact of latent infections with Chlamydophila species in young cattle

To assess long-term effects of naturally occurring infection with Chlamydophila spp. on animal health, 25 calves were grouped according to their chlamydial carrier status and checked for health parameters from 2 to 7 months of age. Monthly PCR testing revealed persistent or frequently recurring infections with Chlamydophila pecorum and Chlamydophila abortus in Group 2 (Chl+, n=13), but not in Group 1 (Chl-, n=12). Despite the absence of any clinical illness, calves in Group 2 showed significantly higher body temperatures (subfebrile), lower bodyweights, reduced serum iron concentrations, lower total haemoglobin and haematocrit values. Counting and flow cytometric differentiation of peripheral white blood cells revealed a general decrease in leukocytes in Group 2. At necropsy, follicular bronchiolitis was found in 10/13 calves in Group 2 but in none of Group 1, and the weight of pharyngeal tonsils was significantly higher in Group 2. In conclusion, naturally occurring infections with Chlamydophila species in calves were found to be associated with chronic effects on animal health at a subclinical level.