Respiratory Infections In Pigs Research Articles

Disposition kinetics of tildipirosin in alpacas after parenteral administrations

Tildipirosin is a macrolide antibiotic marketed in veterinary medicine to treat respiratory infections in pigs and calves. There are no pharmacokinetics studies of tildipirosin after parenteral administration in alpacas which is an extremely decisive step for determining dosage regimen. Thus, the aim of the present study was to establish the disposition fate of tildipirosin following intravenous (IV), intramuscular (IM) and subcutaneous (SC) administrations in alpacas. A crossover study was used, and each alpaca received a single dose of tildipirosin by IV and IM or SC. All the routes of administration were adequately tolerated, and no adverse reactions was observed in any alpaca. Tildipirosin in alpacas reached peak concentrations (Cmax = 0.68 µg/mL vs. 0.79 µg/mL) at 0.22 and 0.50 h (tmax) after IM and SC administration, respectively, with an absolute bioavailability of >100 % for both routes of administration. Steady-state volume of distribution and clearance were 6.02 ± 1.34 L/kg and 2.76 ± 0.28 L/h/kg, respectively. Tildipirosin presents a particular pharmacokinetic behaviour in alpacas, distinctive from other ruminant species, confirming the need to perform studies in the target species in order to promote rational dose regimens of this antimicrobial to maximize its efficacy, minimize its toxicity and avoid the emergence of resistant bacteria.

ДИАГНОСТИКА БАКТЕРИАЛЬНЫХ РЕСПИРАТОРНЫХ ИНФЕКЦИЙ У СВИНЕЙ С ПОМОЩЬЮ ПОЛИМЕРАЗНОЙ ЦЕПНОЙ РЕАКЦИЕЙ С ГИБРИДИЗАЦИОННО-ФЛУОРЕСЦЕНТНОЙ ДЕТЕКЦИЕЙ В РЕЖИМЕ РЕАЛЬНОГО ВРЕМЕНИ

Indications for laboratory testing for the purpose of etiological diagnosis of bacterial respiratory infections were the presence in pigs of an acute disease with local symptoms of respiratory tract damage. The aim of the study was to use PCR with hybridization-fluorescence detection in real time to detect bacterial pathogens of respiratory infections of pigs Mycoplasma hyopneumoniae, Streptococcus pneumoniae, Pasterella multocida, Staphylococcus aureus. We used PCR kits "Vet-factor" (Russia) and LLC NPF "Litech" (Russia). The materials for laboratory studies were: blood, flushes from the nasal mucosa, pieces of parenchymal organs, lymph nodes, trachea and tonsils from sows and corpses of piglets aged from one to four months. The following equipment was used to set up the reactions: The Real-time CFX Connect amplifier (Bio-Rad Laboratories, USA). The results of the PCR analysis were taken into account by the presence or absence of the intersection of the fluorescence curve with the threshold line set at the appropriate level (which corresponds to the presence or absence of the threshold cycle value "Ct" for the sample under study). The results obtained during laboratory diagnostic studies of the material from pigs received by the Kropotkin regional Laboratory over the past 4 years (from 2019 to 2022) indicate a high frequency of detection of bacterial pathogens of respiratory infections in pigs (from 10 to 72%). PCR diagnostics with real-time hybridization-fluorescence detection is optimal for rapid detection of Mycoplasma hyopneumoniae, Streptococcus pneumoniae, Pasterella multocida, Staphylococcus aureus in pigs.

EFFECIENCY AND SAFETY OF THE VETERINARY MEDICINAL PRODUCT VETASEPTOL IN THE TREATMENT OF PIGS SUFFERING FROM ACUTE RESPIRATORY DISEASE OF BACTERIAL ETIOLOGY

The article presents the results of clinical trials on pigs of the veterinary medicinal product Vetaseptol (powder for oral use), manufactured by “Ukrvetrompostach LLC”. The drug was used orally with feed for the treatment of acute respiratory infection in 2-month-old piglets in the dosage recommended by the manufacturer. Before the experiment, microbiological studies were conducted on selection and identification of microorganisms, pathogens of respiratory infection in pigs, and establishing of their sensitivity to the active substances of the drug (oxytetracycline and erythromycin). During the experiment, constant observation of the clinical condition and physiological parameters of the body of the experimental animals were performed. Evaluation of hematological and biochemical indicators was carried out according to recognized methods. The therapeutic efficiency was compared with the data obtained before the treatment and after using the comparator drug. On the basis of obtained data and their statistical analysis, conclusions about the effeciency of Vetaseptol in the treatment of pigs, suffering from streptococcosis, and its effect on their organism were made.
 According to the evaluation of the animal’s clinical condition and the results of laboratory tests obtained, it was established that the tolerability of the studied drug for the treatment of respiratory infection of young pigs was good. During the experimental period and two weeks after the use of the drugs, no side effects were detected and no changes in the behavior of the piglets were observed. The therapeutic effectiveness of the test drug was 100%, and the recovery time was almost 5 days. A comparative analysis of piglet’s hematological indicators showed a reliable decrease of monocytes number in the animal’s leukogram after antibiotic therapy. The normalization of the piglet’s leukogram indicated the termination of inflammatory processes and the improvement of the physiological state of animals. The serum biochemical profile of experimental animals hasn’t changed significantly. Laboratory studies did not reveal hemo- and hepatotoxic effects of the antimicrobial drug.

Detection and molecular characterisation of Mycoplasma spp. from respiratory tract infections in pigs

Achieving food security involves the maintenance of intensive production systems and large animal populations where infectious diseases are the most important challenge that need to be addressed. Respiratory infections in pigs are a formidable threat to swine farmers worldwide. It is multifactorial and is caused by the interplay between bacterial pathogens, viral agents and environmental factors. The present study aimed to identify mycoplasmal agents causing respiratory infections in pigs. A total of 43 samples, comprising of nasal swabs, and necropsy samples with pneumonic lesions were collected. The DNA extracted from the samples were subjected to Mycoplasma genus-specific, followed by species-specific PCR. Twenty five samples were positive for Mycoplasma spp., but further molecular detection performed through species-specific primers, revealed that 12 samples were positive for M. hyorhinis. None of the samples were positive for M. hyopneumoniae. The identity of the amplicons were confirmed by nucleic acid sequencing and BLAST analysis. The evolutionary relationship between the detected organisms was also studied by phylogenetic analysis. This study hints at the significance of M. hyorhinis in causing respiratory infections in swine and also suggests that M. hyopneumoniae may not be a significant health hazard for swine populations of north Kerala.

Widespread Prevalence of Antibodies Against Swine Influenza A (pdm H1N1 09) Virus in Pigs of Eastern Uttar Pradesh, India.

Swine influenza virus (SIV) belongs to family Orthomyxoviridae and can cause acute respiratory infection in pigs. Several pandemic H1N1 human fatal influenza cases were reported in India. Though pigs are predisposed to both avian and human influenza virus infections with the potential to generate novel reassortants, there are only a few reports of SIV in Indian pigs. We conducted a serological survey to assess the status of H1N1 infection in pigs of various states in India, between 2009 and 2016. Based on Haemagglutination inhibition (HI) assay, seroprevalence rate of H1N1 virus ranged between 5.2% (2009) and 36.3% (2011). Widespread prevalence of antibody was observed in eastern Uttar Pradesh from 6.2 to 37.5% during the study period. Co-circulation of seasonal H1N1 virus along with pandemic H1N1 virus was indicated by the presence of specific antibodies against seasonal H1N1 virus in eastern part of Uttar Pradesh. Seroprevalence rate in pigs and influenza infection trend in human shows the possible spill over transmission of influenza to pigs from human. Hence, besides serological surveillance, continuous and systematic molecular surveillance should be implemented in pig population to reduce/quantify the risk and emergence of pandemic influenza.

Assessment of exposure to influenza A viruses in pigs between weaning and market age

Influenza A viruses (IAVs) are common causes of respiratory infection in pigs. The objective of this study was to characterize the circulation of IAVs between weaning and market age on the basis of development of antibody response and molecular epidemiology of detected viruses. Two batches of weaned pigs were followed in the nursery and finisher barns with a sample of 81 and 75 pigs. Nasal swabs and blood samples were collected from individual pigs for virological and serological analyses. A H3N2 subtype virus, of cluster IV, was detected in Study 1, with a maximum of 97.9% identity to HA gene of viruses previously isolated in Ontario. In Study 2, a H1N1 subtype virus, of 2009 H1N1 pandemic lineage, was detected, with a maximum of 97.8% identity to HA gene of viruses previously isolated in Ontario. On the basis of HA gene, it was observed that pigs were being detected with the same virus over time. The existence of antibody titers for IAV other than the isolated one confirmed that more than one subtype can circulate in the same population. In Study 1, pigs with higher numbers of IAV detection had lower serological titers for the same virus that was confirmed to circulate in the nursery (P < 0.01). Thorough knowledge of all endemic viral strains is fundamental for development of infection and disease control, particularly in complex production systems. This may include consideration of sampling and testing strategies which could detect circulation of all IAV variants, even if they have low prevalence.

Indications for the use of highest priority critically important antimicrobials in the veterinary sector.

Among the measures taken to preserve the clinical efficacy of highest priority critically important antimicrobials (HP-CIAs), the WHO has recommended avoiding their use in food-producing animals. Little is known regarding the indications for which different antimicrobial classes are used in animals, even in countries where data on antimicrobial use are available. To outline, in a narrative review, the diseases for which HP-CIAs are used in veterinary medicine, highlighting incongruences with international guidelines and disease conditions where effective alternatives to HP-CIAs are missing. Scientific literature, national reports and expert opinion were used to describe the indications for the use of HP-CIAs in the main food-producing (pigs, cattle and poultry) and companion (horses, dogs and cats) animal species. The most common indications for use of HP-CIAs are enteric and respiratory infections in pigs, cattle and poultry, urogenital infections in dogs and cats and respiratory infections in horses. In some instances, no valid and convenient alternatives to colistin and macrolides are available against certain porcine enteric and bovine respiratory pathogens. Effective, legal and convenient alternatives to HP-CIAs are also lacking for managing common infections in cats, for which oral administration is difficult, Rhodococcus equi infections in horses, some enteric and respiratory infections in poultry and MDR infections in all companion animal species. Future research and stewardship programmes should focus on the disease conditions identified by this review to reduce the use of HP-CIAs in the veterinary sector.

Antimicrobial activity of danofloxacin regarding to bacteria, pathogens of respiratory infections in pigs

The objective of the research was to study the antimicrobial activity of danofloxacin, the third-generation fluoroquinolone antibiotic, against bacteria, pathogens of acute respiratory infection in pigs. Samples of nasal excretions were selected from clinically sick weaned piglets with acute respiratory infection for microbiological investigation. The sensitivity test, carried out by the disc-diffusion method, showed a high level of the microflora sensitivity of the inflammatory exudate to danofloxacin. Bacteria Streptococcus suis and Bordetella bronchiseptica have been isolated and identified from biomaterial by generally accepted microbiological methods. The degree of antimicrobial activity of danofloxacin against isolated strains of microorganisms was established by determination the minimum inhibitory concentration (MIC) of danofloxacin for isolated bacteria by consecutive dilutions in a liquid nutrient medium. The MIC average of danofloxacin for Streptococcus suis isolates (n = 20) was 0.33 ± 0.082 μg/ml and for Bordetella bronchiseptica isolates (n = 8) – 0.21 ± 0.044 μg/ml. The obtained results showed a high level of bacteriostatic activity of danofloxacin regarding bacterial isolates, pathogens of acute respiratory infection in pigs. Danofloxacin, like other fluoroquinolones, is a critical antimicrobial substance for veterinary medicine. Therefore, chemotherapeutic agents based on this antibiotic can serve as a drug of choice for empirical treatment of pigs with acute respiratory infections of bacterial etiology. To right choose an effective agent for etiotropic therapy and minimize the selection of resistant strains of microorganisms, the antimicrobial susceptibility of isolated bacteria should be pre-established.

Detection of Mycoplasma hyopneumoniae in naturally infected gilts over time

Mycoplasma hyopneumoniae causes a chronic respiratory infection in pigs and its transmission occurs mainly by direct contact and by vertical transmission (sow-to-piglet). The objective of this study was to assess the detection dynamics and persistence of M. hyopneumoniae natural infection in replacement gilts. Forty-four twenty-day-old gilts were selected from a M. hyopneumoniae positive farm and followed up to one day prior to their first weaning. Laryngeal swabs were collected every 30days, starting at day 20, for M. hyopneumoniae detection by real-time PCR, resulting in 12 samplings. Piglets born to selected females were sampled via laryngeal swabs one day prior to weaning to evaluate sow-to-piglet transmission. The M. hyopneumoniae prevalence was estimated at each one of the 12 samplings in gilts and a multiple comparison test and Bonferroni correction were performed. Bacterial detection in gilts started at 110days of age (doa) and a significant increase (p<0.05) occurred at 140 doa. The M. hyopneumoniae prevalence remained above 20% from 140 to 230 doa, decreasing thereafter. However, it did not reach 0% at any sampling after 110 doa. In this study, M. hyopneumoniae was not detected in piglets sampled prior to weaning. The M. hyopneumoniae detection pattern showed that in natural infections, gilts were positive for M. hyopneumoniae for one to three months, but occasionally long-term detection may occur. Moreover, the lack of M. hyopneumoniae detection throughout the study in 18.2% of gilts indicated the existence of negative subpopulations in positive herds.

Coronavirus HKU15 in respiratory tract of pigs and first discovery of coronavirus quasispecies in 5′-untranslated region

Coronavirus HKU15 is a deltacoronavirus that was discovered in fecal samples of pigs in Hong Kong in 2012. Over the past three years, Coronavirus HKU15 has been widely detected in pigs in East/Southeast Asia and North America and has been associated with fatal outbreaks. In all such epidemiological studies, the virus was generally only detected in fecal/intestinal samples. In this molecular epidemiology study, we detected Coronavirus HKU15 in 9.6% of the nasopharyngeal samples obtained from 249 pigs in Hong Kong. Samples that tested positive were mostly collected during winter. Complete genome sequencing of the Coronavirus HKU15 in two nasopharyngeal samples revealed quasispecies in one of the samples. Two of the polymorphic sites involved indels, but the other two involved transition substitutions. Phylogenetic analysis showed that the two nasopharyngeal strains in the present study were most closely related to the strains PDCoV/CHJXNI2/2015 from Jiangxi, China, and CH/Sichuan/S27/2012 from Sichuan, China. The outbreak strains in the United States possessed highly similar genome sequences and were clustered monophyletically, whereas the Asian strains were more diverse and paraphyletic. The detection of Coronavirus HKU15 in respiratory tracts of pigs implies that in addition to enteric infections, Coronavirus HKU15 may be able to cause respiratory infections in pigs and that in addition to fecal-oral transmission, the virus could possibly spread through the respiratory route. The presence of the virus in respiratory samples provides an alternative clinical sample to confirm the diagnosis of Coronavirus HKU15 infection. Quasispecies were unprecedentedly observed in the 5′-untranslated region of coronavirus genomes.Emerging Microbes & Infections (2017) 6, e53; doi:10.1038/emi.2017.37; published online 21 June 2017

Correlation Between Serum Acute Phase Proteins, Lung Pathology, and Disease Severity in Pigs Experimentally Co-Infected with H3N2 Swine Influenza Virus and Bordetella Bronchiseptica

Abstract The kinetics of C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA), and pig major acute protein (Pig-MAP) response in pigs co-infected with H3N2 swine influenza virus (SwH3N2) and Bordetella bronchiseptica (Bbr) was studied, with assessment of potential correlations between the concentration of acute phase proteins (APPs) in serum samples, lung lesions, and the clinical course of the disease in co-infected pigs. The standard bacteriological methods for detection of Bbr and PCR technique for identification of Bbr and SwH3N2 were used. The serum concentrations of APPs were measured using ELISA. The concentration of CRP, SAA, and Pig-MAP was significantly higher from 2 to 4 or 5 dpi. The concentration of Hp was elevated until the end of the study. Significant correlations were found between the serum concentration of SAA and Pig-MAP and clinical score, and between the concentration of SAA and lung score. Apart from their potential as biological markers for co-infections, SAA and Pig-MAP levels have additive value since they are related to the severity of infection. The results indicate that measurement of APP (i.e SAA) may prove valuable in assessing the severity of respiratory infection in pigs, and may be of supportive value in the clinical evaluation of animals and in the selection of more appropriate treatment.

Porcine Respiratory Disease Complex and Biofilms

The Porcine respiratory disease complex (PRDC) is a term used to describe polymicrobial respiratory infections in pigs. Respiratory diseases in pigs are common in modern pork production worldwide and are the responsible for major economic losses in the swine industry. Pathogens involved in respiratory disease in pigs vary significantly among farms, production sites, regions and countries, making generalizations about the PRDC treatment and difficult to control it. The interactions that occur on the cellular and molecular levels during concurrent infection of pigs with two or more respiratory pathogens are multi-faceted and convoluted. There are a variety of bacterial and viral pathogens commonly associated with the PRDC. The main associated bacteria include: Actinobacillus pleuropneumoniae, Streptococcus suis, Pasteurella multocida, Bordetella bronchiseptica, Haemophilus pasaruis, and Mycoplasma hyopneumoniae. Currently, it is known among microbiologists that biofilm formation is an universal attribute of microorganisms and the main way of life in nature that are causing problems such as developing diseases in animals and humans. Here, is reviewed the current knowledge of the major bacteria involved in this disease, their ability to form biofilms, as well as their importance on the infection process.

Distribution of enrofloxacin and its active metabolite, using anin vivoultrafiltration sampling technique after the injection of enrofloxacin to pigs

The objective of this study was to determine the pharmacokinetics (PK) of enrofloxacin in pigs and compare to the tissue interstitial fluid (ISF). Six healthy, young pigs were administered 7.5 mg/kg enrofloxacin subcutaneously (SC). Blood and ISF samples were collected from preplaced intravenous catheters and ultrafiltration sampling probes placed in three different tissue sites (intramuscular, subcutaneous, and intrapleural). Enrofloxacin concentrations were measured using high-pressure liquid chromatography with fluorescence detection, PK parameters were analyzed using a one-compartment model, and protein binding was determined using a microcentrifugation system. Concentrations of the active metabolite ciprofloxacin were negligible. The mean ± SD enrofloxacin plasma half-life, volume of distribution, clearance, and peak concentration were 26.6 ± 6.2 h (harmonic mean), 6.4 ± 1.2 L/kg, 0.18 ± 0.08 L/kg/h, and 1.1 ± 0.3 μg/mL, respectively. The half-life of enrofloxacin from the tissues was 23.6 h, and the maximum concentration was 1.26 μg/mL. Tissue penetration, as measured by a ratio of area-under-the-curve (AUC), was 139% (± 69%). Plasma protein binding was 31.1% and 37.13% for high and low concentrations, respectively. This study demonstrated that the concentration of biologically active enrofloxacin in tissues exceeds the concentration predicted by the unbound fraction of enrofloxacin in pig plasma. At a dose of 7.5 mg/kg SC, the high tissue concentrations and long half-life produce an AUC/MIC ratio sufficient for the pathogens that cause respiratory infections in pigs.

Draft Genome Sequences of Actinobacillus pleuropneumoniae Serotypes 2 and 6

Actinobacillus pleuropneumoniae is a bacterial pathogen that causes highly contagious respiratory infection in pigs and has a serious impact on the production economy and animal welfare. As clear differences in virulence between serotypes have been observed, the genetic basis should be investigated at the genomic level. Here, we present the draft genome sequences of the A. pleuropneumoniae serotypes 2 (strain 4226) and 6 (strain Femo).

Immunoproteomic analysis of outer membrane proteins and extracellular proteins of Actinobacillus pleuropneumoniae JL03 serotype 3

BackgroundActinobacillus pleuropneumoniae is the causative agent of porcine contagious pleuropneumonia, a highly contagious respiratory infection in pigs, and all the 15 serotypes are able to cause disease. Current vaccines including subunit vaccines could not provide satisfactory protection against A. pleuropneumoniae. In this study, the immunoproteomic approach was applied to the analysis of extracellular and outer membrane proteins of A. pleuropneumoniae JL03 serotype 3 for the identification of novel immunogenic proteins for A. pleuropneumoniae.ResultsA total of 30 immunogenic proteins were identified from outer membrane and extracellular proteins of JL03 serotype 3, of which 6 were known antigens and 24 were novel immunogenic proteins for A. pleuropneumoniae.ConclusionThese data provide information about novel immunogenic proteins for A. pleuropneumoniae serotype 3, and are expected to aid in development of novel vaccines against A. pleuropneumoniae.

Functional Characterization of AasP, a Maturation Protease Autotransporter Protein ofActinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, a highly contagious respiratory infection in pigs. AasP, a putative subtilisin-like serine protease autotransporter, has recently been identified in A. pleuropneumoniae. We hypothesized that, similarly to other autotransporters of this type, AasP may undergo autocatalytic cleavage resulting in release of the passenger domain of the protein. Furthermore, AasP may be responsible for cleavage of other A. pleuropneumoniae outer membrane proteins. To address these hypotheses, the aasP gene was cloned and the expressed recombinant AasP protein used to raise monospecific rabbit antiserum. Immunoblot analysis of whole-cell lysates and secreted proteins demonstrated that AasP does not undergo proteolytic cleavage. Immunoblot analysis also confirmed that AasP is universally expressed by A. pleuropneumoniae. Confirmation of the maturation protease function of AasP was obtained through phenotypic analysis of an A. pleuropneumoniae aasP deletion mutant and by functional complementation. Comparison of the secreted proteins of the wild type, an aasP mutant derivative, and an aasP mutant complemented in trans led to the identification of OmlA protein fragments that were present only in the secreted-protein preparations of the wild-type and complemented strains, indicating that AasP is involved in modification of OmlA. This is the first demonstration of a function for any autotransporter protein in Actinobacillus pleuropneumoniae.

Cough sound analysis to identify respiratory infection in pigs

Cough sound detection is a central element to diagnose common respiratory diseases like pneumonia in intensive pig farming. The aim of this work is the description of acoustic features of cough sounds originating from a lung infection and the comparison between these kind of cough sounds with those provoked by inhalation of citric acid. Coughs have been recorded from infected animals in field conditions (pneumonia) and from healthy animals in laboratory (induced). After having completed the classification, the investigation on infectious and non-infectious cough sounds has involved the main differences among acoustic parameters, like the Root Mean Square (RMS), the peak frequency (Hz), the duration and the time occurring between successive coughs in a cough attack. The results show a significant difference among the RMS, peak frequency and duration in cough sounds from healthy and infected animals. RMS was 0.215 for healthy animals and 0.124 for infected ones ( P = 0). Non-infectious coughs have an average peak frequency of 1600 Hz, while infectious coughs stand around 600 Hz. Also the length of sounds is significantly lower ( P < 0.001) for non-infectious coughs (average 0.43 s) than for infectious ones (average 0.67 s). The space of time between each sick cough in a cough sequence seems shorter than the interval occurring between healthy coughs (0.37 s versus 0.52 s). The above mentioned findings could be surely helpful to develop a real-time cough classification algorithm, based on sound feature analysis, in order to acquire a monitoring system for automatic and continuous infection in pig houses.

Respiratory and fecal shedding of Porcine respiratory coronavirus (PRCV) in sentinel weaned pigs and sequence of the partial S-gene of the PRCV isolates

Summary.Porcine respiratory coronavirus (PRCV), a spike (S) gene deletion mutant of Transmissible gastroenteritis virus (TGEV), causes mild or subclinical respiratory infections in pigs. The shedding of PRCV/TGEV was studied at different days post-arrival in fecal and nasal swabs from PRCV/TGEV seronegative sentinel pigs introduced into a PRCV seropositive herd with questionable TGEV serology and diarrhea. Nasal shedding of PRCV was detected in 57% and 63% of samples by nested-RT-PCR and cell culture immunofluorescence (CCIF), respectively. However fecal shedding of PRCV was detected in 37% of the samples by nested-RT-PCR and 19% by CCIF. Four respiratory and 5 fecal PRCV strains were isolated in swine testicle cells including nasal/fecal PRCV pairs (isolated at the same time) from 3 pigs. Comparison of nasal/fecal PRCV pairs from individual pigs revealed different deletions in the spike (S) gene (648 or 681 nt) in 2 pairs and a consistent change in nt 790/791 (aa T to V) for all pairs. In preliminary studies, inoculation of gnotobiotic pigs with each plaque-purified pair of the nasal and fecal PRCV isolates, revealed no clinical disease but different tropisms. The nasal isolate was shed both nasally and in feces, but the fecal isolate was shed only marginally in feces, and not nasally. Our results show that nested-RT-PCR was as sensitive as CCIF for PRCV detection in nasal swabs, but was more sensitive than CCIF for PRCV detection in fecal samples; alternatively PRCV shed in feces was more labile with loss of infectivity. The S-gene sequence differences found between the fecal and respiratory PRCV isolates may influence their tissue tropism. These new PRCV isolates should be useful to understand the molecular basis of coronavirus tropism and evolution in infected swine.

In vitro evaluation of various quinolone antibacterial agents against veterinary mycoplasmas and porcine respiratory bacterial pathogens

The in vitro activities of 12 quinolones and four antibiotics were determined against 15 veterinary mycoplasmal species and four species of bacteria commonly involved in respiratory infections in pigs. The newer quinolones were markedly more active in vitro against a wide range of mycoplasmas than nalidixic acid and the earlier quinolones. Against Mycoplasma hyopneumoniae ciprofloxacin was the most active quinolone with a geometric mean minimal inhibitory concentration (MIC) against 16 strains of 0.01 microgram ml-1 compared with 0.04 microgram ml-1 for tiamulin, 0.06 microgram ml-1 for tylosin, 0.17 microgram ml-1 for oxytetracycline and 0.23 microgram ml-1 for gentamicin. M hyosynoviae was less sensitive to the quinolones with mean MICs of 0.6 microgram ml-1 for ofloxacin and 0.7 microgram ml-1 for ciprofloxacin compared with 0.034 microgram ml-1, or less, for tiamulin. Norfloxacin and its 6-chloro analogue were both mycoplasmacidal in vitro at five or 10 times their MICs against M hyopneumoniae UCD4. Tiamulin was mycoplasmastatic. The quinolones were also active against porcine Bordetella bronchiseptica and Pasteurella multocida strains and Haemophilus species. Ciprofloxacin was the most active quinolone with mean MICs of 0.58 microgram ml-1 against B bronchiseptica (nine strains), 0.026 microgram ml-1 against P multocida (five strains) and 0.01 microgram ml-1, or less, against Haemophilus pleuropneumoniae (nine strains) and H parasuis (two strains) compared with mean MICs of from 0.5 microgram ml-1 to 64 micrograms ml-1, or more, for the antibiotics. This combination of excellent mycoplasmacidal activity against M hyopneumoniae and good antibacterial activity, suggests that the quinolones have great potential for treating respiratory infections in pigs, including enzootic pneumonia.

A study of air quality and respiratory infections in pigs raised in confinement

Air quality, respiratory disease, and growth rate were followed in four different farrowing and nursery systems. Ammonia levels varied with ambient air temperature, but were within normally accepted levels (25 ppm). These levels of ammonia did not appear to affect the health or performance of the pigs raised in these units. Hydrogen sulfide levels were consistently low. Counts of bacterial colony forming particles (BCFP) varied and the organisms identified were predominantly micrococci. Bordetella bronchiseptica was isolated from nasal cavities of pigs from 3 out of 4 farms. Three of the farms did not have evidence of atrophic rhinitis; pigs farrowed in the last quarter of the test year on one farm from which B. bronchiseptica was isolated developed lesions of atrophic rhinitis. The B. bronchiseptica isolates from the 3 farms were virulent for gnotobiotic piglets. Groups of pigs for slaughter inspection from one farm had lungs with 11–28% pneumonic lesions; these lesions were not typical of mycoplasmal pneumonia.