Actinobacillus pleuropneunomiae (App) is a bacterium that is known to cause pleuropneumonia (inflammation of the pleura and lungs). App can be acute, peracute or chronic, and can also persist subclinically under the correct conditions. Young pigs in particular (including finishers) are more susceptible to clinical infection with App. There are at least 19 known different serogroups of App, with varying combinations of virulence factors that are one determinant of whether clinical symptoms occur. That App is known to be a causative agent can also seen in various monitoring tools, starting with the Online Monitor. In 2023, 70 per cent of App reports were about finisher pigs and 26 per cent about weaned piglets (see figure below).
finisher pigs
Weaned piglets
Sows
Suckling piglets
Over a quarter of all respiratory complaints in the Online Monitor in 2023 were thought to be caused by App. If we look at the total number of health problems reported, App is stated in 8 per cent. No clear increase or decrease has been visible over the past few years. However, more reports of App are made in spring and fewer in autumn. Symptoms such as coughing, nasal discharge and other respiratory complaints, are often attributed to an App infection. App is a regular topic of conversation on the Veekijker phone line. In the second half of 2023, App ranked third among disease-specific topics in terms of the number of questions. Over 2023 as a whole, an average of 8 per cent of disease-specific questions were about App, which is the same as the eight-year average (2016-2023). The questions are mostly about serotyping, treatment of clinical symptoms caused by App, vaccination strategy and the role of App as a primary or secondary pathogen.
Pathological examinations have shown us that App plays a role in the cause of death in over 7 per cent of necropsies. In the majority of these necropsies, App was responsible for causing pleuropneumonia, mainly by finishers and to a lesser extent in weaned piglets. In the second half of 2023, infection with App was the fifth most common diagnosis upon pathological examination.
Figure: Number of reports of App in the Online Monitor, by age category (for 2023)
Breeder and
Specific findings
Evidence of PCV3 infections in aborted foetuses: two case reports The relationship between PCV3 and the causes of reproductive problems in sows is disputed. In 2023, PCV3 was found as the only likely cause in two cases in which aborted foetuses and amniotic membranes had been presented for examination. These two cases describe the clinical and diagnostic investigations, aiming to add to the scientific debate on the relevance and impact of PCV3 in pigs.
Case 1
A farm with 1,300 sows where gilt pigs were reared in-house reported an increase in premature farrowing with higher numbers of mummified foetuses and stillborn piglets during an eight-week period. Moreover, sows and in particular gilts showed anorexia around 5 weeks after insemination, followed by weight loss and occasionally death. In addition, an increase in abortions was observed.
Case 2
A farm with 450 animals reported occasional abortions in the third trimester of gestation as well as premature birth (D108 after insemination) in about 10 gilts over a 3-week period.
No evidence was found at either farm of respiratory or gastrointestinal diseases, or of systemic diseases in the sows or gilts (except for anorexia). Both farms kept the rearing and housing of gilts strictly separate from sows, and the gilt adaptation period was limited in time.
In both cases, two foetuses (plus foetal membranes in case 2) were submitted for pathological and microbiological examination. No macroscopic abnormalities were found. Bacterial cultures of the gastric contents were negative. The initial PCR tests on the foetal tissues for parvovirus, PCV2 and PRRSV were also negative. In Case 1, histopathology showed lymphocytic and neutrophilic perivascular inflammation in the myocardium. Myocarditis was not observed in Case 2. Subsequently, myocardial tissue was submitted for PCV3 testing by PCR; in both cases, PCV3-PCR yielded positive results with low Ct values (approx. 14 and 21 respectively). Tissue samples were then examined for PCV3 using in situ hybridization (ISH). In both cases, ISH showed evidence of a multifocal presence of PCV3 DNA in the nuclei of cardiac muscle cells and in the walls of vessels in the cardiac muscle.
In summary, PCV3 was present in the foetal tissues in both cases and was deemed to be the sole likely cause of the premature births and abortions. Case 2 demonstrates that PCV3 DNA can be detected in large amounts in cardiac muscle tissue, even in the absence of inflammation. Moreover, the absence of PCV3 in one of the foetuses examined shows that in cases of abortion, multiple foetuses may well need to be tested to diagnose PCV3 infection.
These cases add weight to the discussion about the relationship between PCV3 infections and reproductive problems in sows.
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Animal health barometer, fourth quarter, 2023
Disease/disorder/health characteristic Situation in the Netherlands/Europe
Article 15 diseases (notifiable and controlled)
Foot-and-mouth disease (FMD) The Netherlands has been disease-free since 2001. No outbreaks in Europe in the fourth quarter of 2023.
Classical swine fever (CSF) The Netherlands has been disease-free since 1997. No outbreaks have been reported in Europe since 2015.
African swine fever (ASF) The Netherlands has been disease-free since 1986. Brucellosis The Netherlands has been disease-free since 1973.
Aujeszky’s disease (ADV ) The Netherlands has been disease-free since 2007. Detected in France and Poland.
Article 100 diseases (notifiable)
Salmonella Detected 3x in pathological examinations. Detected 3x in samples submitted.
Monitoring: Veekijker
Glässer disease
Increase in the number of queries in the fourth quarter of 2023.
Streptococci Increase in the number of queries in the fourth quarter of 2023.
Monitoring: pathological examinations
Streptococcus suis
Meningitis caused by Streptococcus suis was the most frequent diagnosis in the fourth quarter of 2023.
Numbers Over 2023 as a whole, there were more submissions for necropsy than in previous years.
Online Monitoring
Respiratory complaints
Respiratory complaints are the most frequent reports in the Online Monitor.
Sows Sows are least likely to be diagnosed with health problems, with 91% of visits showing no health issues.
Animal health monitoring
Since 2002, Royal GD has been responsible for animal health monitoring in the Netherlands, in close collaboration with the veterinary sectors, the business community, the Ministry of Agriculture, Nature and Food Quality, vets and farmers. The information used for the surveillance programme is gathered in various ways, whereby the initiative comes in part from vets and farmers, and partly from GD Animal Health. This information is fully interpreted to achieve the objectives of the surveillance programme – rapid identification of health issues on the one hand and monitoring trends and developments on the other. Together, we team up for animal health, in the interests of animals, their owners and society at large.
