Marc Verdonck

Enzootic pneumonia in pigs

This article reviews current knowledge concerning enzootic pneumonia. Enzootic pneumonia, caused by Mycoplasma hyopneumoniae and exacerbated by secondary invaders, occurs worldwide and has been known for many years. The organism, with its typical characteristics, invades the respiratory tract in several successive steps. Clinical symptoms and lesion development are the result of the pathogenic capacity of Mycoplasma hyopneumoniae and the defence reactions in the lung. The economic relevance of pneumonia is influenced to a large extent by common secondary infections which follow an initial M. hyopneumoniae infection. Different tests for the diagnosis of pneumonia in individual pigs and in groups are available. Treatment and control is not simple since enzootic pneumonia is a multi-factorial disease. Some epidemiological aspects and the most important measures for prevention of the disease are described.

Effect of vaccination against Mycoplasma hyopneumoniae in pig herds with an all-in/all-out production system

A multi-site field study was conducted to evaluate an inactivated Mycoplasma hyopneumoniae (Mh) vaccine in 14 pig herds infected by Mh and practising an all-in/all-out production system. In each herd, a vaccinated and control group of 250 pigs each were compared during the growing/finishing period with respect to performance parameters (major variables) and by means of clinical, serological and pathological parameters (ancillary variables). Mh vaccination significantly (P < 0.05) improved daily weight gain (+22 g), feed conversion ratio (-0.07), medication costs (-0.476 ECU/pig) (1 ECU = US

Non-infectious factors associated with macroscopic and microscopic lung lesions in slaughter pigs from farrow-to-finish herds

1.0269542), prevalence of pneumonia lesions (-14%) and severity of pneumonia lesions (-3%). Mortality rate, severity of coughing and carcass quality were not significantly influenced by Mh vaccination. Serological results of Mh and other respiratory pathogens are presented and discussed. A cost-benefit analysis based on significantly improved performance parameters demonstrated that Mh vaccination was economically attractive as it resulted in an increase of the net return to labour with 1.300 ECU per finishing pig sold. The sensitivity of the economic benefit was illustrated towards fluctuations in pig finishing prices.

Bacterial endometritis and vaginal discharge in the sow : prevalence of different bacterial species and experimental reproduction of the syndrome

A cross-sectional epidemiological study was conducted in 150 randomly selected farrow-to-finish herds to investigate which non-infectious factors might act as risk indicators for the prevalence and severity of macroscopic and microscopic lung lesions in slaughter pigs. Data were collected during herd visits through inspections of the pigs and through interviews with the farmers. Macroscopic lung lesions of pneumonia and pleuritis were recorded at slaughter from 25 pigs per herd, and microscopic lung lesions of lymphohistiocytic infiltration were recorded from 10 pigs per herd. The median herd level prevalences were 24 per cent for pneumonia, 16 per cent for pleuritis and 60 per cent for lymphohistiocytic infiltration. Pneumonia lesions were negatively associated with pleuritis lesions and positively associated with lymphohistiocytic infiltration. Pleuritis lesions were negatively associated with lymphohistiocytic infiltration. The prevalence and the severity of pneumonia lesions were increased by a high frequency of purchasing gilts and by a slaughter date in January to February. The presence of a growing unit also increased the severity of pneumonia. The prevalence and the severity of pleuritis lesions were higher when there were more pig herds in the municipality, and when there were poor biosecurity measures, and their prevalence was increased by a slaughter date in January to February, and their severity by a slaughter date in March to April. An increase in the airspace stocking density in the finishing unit also increased the prevalence of pleuritis. The prevalence and the severity of lymphohistiocytic infiltration in the lung tissue were higher in herds purchasing gilts. Pigs raised in pens with slatted floors were also at higher risk of more severe lesions of lymphohistiocytic infiltration.

Endometritis and vaginal discharge in the sow

Abstract A total of 73 porcine genital tracts were macroscopically and histologically examined and bacteriologically tested for the presence of aerobic facultatively pathogenic bacteria. Nine uteri originated from sows with abnormal vaginal discharge (P-group) and 64 uteri originated from slaughtered sows (S-group). Fifty-six per cent of the uteri from the P-group were bacteriologically positive compared with only 20% of the uteri from the S-group. Uteri of sows with histological evidence of an acute or subacute endometritis were significantly more often infected than the uteri of sows with a chronic endometritis or with histologically normal uteri. The bacteria isolated were mainly Escherichia coli, Staphylococcus spp. and Streptococcus spp. These results indicate that the syndrome of endometritis and vaginal discharge is possibly caused by ascending infections with facultatively pathogenic bacteria. To evaluate the pathogenicity of the isolated bacteria, experimental infections were carried out. Ten pubertal, unmated gilts were inoculated in the uterus by laparotomy with 2 ml of a suspension containing Staphylococcus hyicus, an E. coli sp., an Actinomyces sp. or a carboxyphilic Streptococcus suis sp. An eleventh gilt was inoculated as a control with 2 ml of a phosphate-buffered saline (PBS) solution. The gilts were daily observed for clinical symptoms. Ten to 19 days after inoculation a second laparotomy was carried out to take samples for histological and bacteriological examination. Vaginal discharge was observed in all gilts inoculated with E. coli 109 cfu ml−1 or S. hyicus. Clinical signs were not observed in the gilts that were inoculated with the Actinomyces sp., the carboxyphilic Streptococcus suis sp. or 107 cfu E. coli. It was possible to reproduce the syndrome of vaginal discharge as it occurs on problem herds, by means of an experimental infection with an E. coli or Staphylococcus hyicus strain. According to Kochs postulates, both inoculated bacteria can be considered as an aetiologic agent of the disease.

The relationship between the blood progesterone concentration at early metoestrus and uterine infection in the sow

Abstract A clinical study concerning the epidemiology of the syndrome endometritis associated with vaginal discharge and reproductive failure is described. In all affected herds the return rates after service were increased above 30% and the number of weaners per sow per year was decreased by at least two. In an experimental infection model the pathogenicity of Escherichia coli on the sows endometrium was investigated and the influence of the oestrus cycle on the uterine defence mechanism was studied. Ten pubertal, unmated gilts of the Belgian Negative Landrace were infected in the uterus with suspensions of an E. coli strain isolated from the uterus of a discharging sow. The results indicated that it is possible to induce an acute purulent endometritis by inoculation of E. coli . The stage of the oestrus cycle appeared to be an important factor in the development of endometritis. None of the five gilts inoculated at the day of oestrus with 50 ml of a suspension containing 10 7 cfu ml −1 developed clinical symptoms. Three of the five gilts inoculated just after the end of standing heat also developed clinical signs. The difference between both groups was significant.

Benefit to cost of vaccination against mycoplasma hyopneumoniae in pig herds under Belgian market conditions from 1996 to 2000

Abstract In a previous study it was shown that gilts inoculated in the uterus during standing oestrus had a better resistance to Escherichia coli infections than gilts that were similarly inoculated within 12 h after the end of the standing reflex (De Winter et al., 1992). In the present study, the changes of blood progesterone concentrations during early metoestrus were investigated. It was also investigated to what extent the onset of endometritis after intrauterine inoculation is correlated to the blood progesterone concentration. In a preliminary study, the plasma progesterone concentration was measured in a group of 11 gilts during early metoestrus, in order to evaluate the average progesterone levels at that stage of the oestrous cycle. A wide variation of blood progesterone concentrations was observed. A second group of 13 gilts was inoculated in the uterus with an E. coli suspension in order to investigate the presence of a correlation between blood progesterone level and susceptibility of the porcine uterus to bacterial endometritis. A third group of six gilts was similarly inoculated with Staphylococcus hyicus. A clear correlation between blood progesterone concentration and susceptibility to endometritis and the development of a vaginal discharge in gilts experimentally inoculated was observed. The gilts with a low blood progesterone concentration at the time of inoculation had less vaginal discharge and a better resistance to endometritis than gilts with a higher blood progesterone concentration. In gilts inoculated with E. coli, as well as those inoculated with S. hyicus, a significant correlation (P

Effectiveness of treatment with lincomycin hydrochloride and/or vaccination against Mycoplasma hyopneumoniae for controlling chronic respiratory disease in a herd of pigs

Abstract The present study investigated the economic benefits and costs of vaccination against Mycoplasma hyopneumoniae (Mh) in pig herds under market conditions present from 1996 through 2000 in Belgium. The performance results (daily weight gain, feed conversion ratio, mortality rate, medication costs, carcass quality) used for the economic analyses were obtained from a multisite field study that was conducted in 14 Belgian pig herds with a low infection pressure of Mh and practising all-in/all-out production. In these herds, following improvements in performance were obtained through vaccination: daily weight gain +22 g/day, feed conversion ratio −0.07, mortality rate −0.23%, medication costs −0.45 euro/pig. No changes in carcass quality following vaccination were observed. Partial budgeting analysis showed that the average additional net return to labour (NRL) during the 5 years was +0.72 euro/pig, corresponding with an increase in NRL of 4.1%. The additional NRL through Mh vaccination ranged from −0.28 euro/pig in 1998 (NRL −2.2%) to +1.30 euro/pig in 2000 (NRL +3.5%). The results demonstrated that Mh vaccination was economically attractive, except in periods with extremely bad market conditions. In addition to information of production benefits resulting from Mh vaccination, data of market conditions are necessary for precisely quantifying the financial benefit of Mh vaccination in a specific herd.

Seroprevalence of Actinobacillus pleuropneumoniae serovars 2, 3 and 9 in slaughter pigs from Belgian fattening farms.

A herd of pigs infected with Mycoplasma hyopneumoniae was used in a double-blind randomised trial to assess the effectiveness of three control strategies against chronic respiratory disease in growing-finishing pigs. One group of 61 pigs received 220 ppm lincomycin hydrochloride in the feed from day 71 to day 91, a second group was vaccinated against M hyopneumoniae at four and 28 days of age, and a third group received both treatments; a fourth group was left untreated as a control. Throughout the nursery-finishing period (day 29 to slaughter) the average daily weight gain and feed conversion rate of all the treated groups were slightly better than in the controls, but there were no significant differences between them. There were no significant differences between the treated groups in terms of clinical signs, serology, pathology or mortality, which was very low throughout the trial.

Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds.

Fifty randomly selected fattening pig herds were studied to investigate the epidemiological characteristics of infections with Actinobacillus pleuropneumoniae serovars 2, 3 and 9, and to identify risk factors for their within-herd seroprevalences. Information about 13 farm characteristics was obtained by means of a questionnaire and used to assess potential risk factors for the percentage of slaughter pigs with antibodies against each of the three serovars. The presence of antibodies was measured with an indirect ELISA. The median within-herd seroprevalence for serovar 2 was 58 per cent (range 0 to 100 per cent), for serovar 3, 53 per cent (range 10 to 95 per cent), and for serovar 9, 35 per cent (range 5 to 100 per cent). All but one farm tested positive for A pleuropneumoniae serovar 2, and all the farms were positive for A pleuropneumoniae serovars 3 and 9. There was a positive association (P<0.05) between each pair of serovars. The within-herd seroprevalence of serovar 2 was significantly associated with the density of pig herds in the municipality (odds ratio [OR]=1.60; P<0-05) and with the absence of preventive medication at the start of the fattening period (OR=2.77; P<0.10). No significant risk factors were found for serovar 3. The percentage of pigs positive for serovar 9 was significantly associated with a slaughter date in June (OR=2.30; P<0.10) and with herds in which the finishing houses were not divided into separate compartments (OR=2.99; P<0.05).