Streptococci – and Streptococcus suis in particular – are well-known pathogens in the pigfarming sector. It is the most frequently reported likely diagnosis in the Online Monitor, a common topic of discussion on the Veekijker hotline and often stated as the main diagnosis in necropsies. It is striking that streptococci claim almost equal shares in the Online Monitor and in pathological examinations. In 22 percent of the reports of health problems in the Online Monitor, streptococci are thought to be involved. In 21 percent of necropsies, infection with streptococci is given as the primary diagnosis, underlining the reports in the Online Monitor (see figure).
Figure: The percentage of reports in the Online Monitor for which streptococci are given as the most probable diagnosis, the percentage of questions about streptococci and (in the last column) the percentage of necropsies in which streptococcal infection is given as the primary diagnosis (first half of 2024).
In the case of pathological examinations, Streptococcus suis appears in 18 percent of all main diagnoses during the first six months of 2024. Streptococcus suis is most frequently demonstrated here to be the cause of sepsis and meningitis, which are mostly observed in weaned piglets. Weaned piglets are also the category of animals in which streptococci have the greatest impact: 68 percent of streptococcus-related diagnoses are for weaned piglets.
Finally, it should be noted that various serogroups of Streptococcus suis are known. A recent inventory of the strains that have been typed shows that serotype 9 is found most frequently (41%), followed by a third of all isolates that cannot be recognised as types 1, 2, 4, 7, 8 or 9. Serotyping can help reach the correct diagnosis and, combined with an antibiogram, can help create a suitable treatment plan.
Streptococci given as the most probable diagnosis in the Online Monitor
Questions on the Veekijker hotline about streptococci
Streptococcal infection as the primary diagnosis in necropsies
Specific findings
App: serotype 13 or serotype 7
Late last year, sows in the farrowing pen at a specific pathogen-free (SPF) company became ill. The sows had a fever, were not eating and a few of them died. The sows were sent to GD for pathological examination. Macroscopically, the pathologist described fibrinous pleuropneumonia, typical of infection with Actinobacillus pleuropneumoniae (App). This is a rare finding in this animal group, specifically when no respiratory symptoms were listed in the case history. The veterinarian was contacted directly for more background information about this case. Because it was a farm that should actually be free of App, it was decided to store the strain for possible future investigations and to have it serotyped. Serotyping App isolates is usually done using monoclonal antibodies against reference strains of the serogroups. GD outsources these studies. The regular bacteriological investigations showed that it was App biotype 1, which depends on nicotinamide adenine dinucleotide (NAD) for growth. Serotyping using antibodies showed a positive reaction for App serotype 13, which normally belongs to biotype 2 (NAD-independent growth). There have never previously been reports in Europe of this variant of App serotype 13.
To confirm the suspected classification as App serotype 13 biotype 1, the isolate was sent away for another type determination, this time using PCR. Strikingly enough, this follow-up diagnostic testing came back negative for App serotype 13 but positive for serotype 7. After feedback of this result to the first lab, the serotyping was repeated there and the result was unchanged. A discrepancy therefore remains between the results of the two external laboratories. This discrepancy is highly regrettable, but cannot be solved directly at the present time. For the Netherlands, it should be noted that both App variants occur relatively infrequently and the impact of this poorer diagnostic process will therefore be relatively limited. The veterinarian, working with another expert, has produced a clearer picture of the health situation at the farm and how App was spread. The App bacterium had spread throughout the farm, which meant there was no possibility of regaining the App-free status any more. Vaccinations are being given in the meantime to reduce the clinical impact on both the breeding animals and the weaned piglets and porkers. This case is an example of how animal health monitoring works towards two objectives: retaining a clear picture of known complaints and looking at the potential introduction of known complaints that are not yet present in the Netherlands.
Toltrazuril-resistant coccidia
The Veekijker was contacted in June 2024 because of coccidiosis problems in pigs despite treatment with toltrazuril. It was decided to take a very close look at how the treatment was done and at the dosage. After this, contact was made again and – given that the method of treatment and the dosage were in order at this farm, but issues with coccidiosis remained despite the treatment – the possible causes were examined further. A veterinary parasitologist with a great deal of experience with coccidia was contacted who determined that the coccidia present at the farm were resistant to toltrazuril.
Toltrazuril is the only active substance we have available for treating coccidiosis in pigs. Toltrazuril is used at a large proportion of Dutch pig breeding farms. At the farm in question, a disinfectant containing cresols is being used to keep the number of infectious oocysts as low as possible. The MEB has been notified by the veterinarian of this case of resistance, as per protocol. One case has previously been described in the Netherlands in 2017 (Shrestha A, Freudenschuss B, Jansen R, Hinney B, Ruttkowski B, Joachim A. Experimentally confirmed toltrazuril resistance in a field isolate of Cystoisospora suis. Parasite Vectors. 2017 Jun 29;10(1):317.). Given the lack of effective alternatives to toltrazuril, a repeat finding of resistance suggests increased alertness is needed, along with possible further studies.
Pig health in the Netherlands, second quarter of 2024
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 second quarter of 2024.
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 twice in pathological examinations. Detected 3 times in submitted manure samples.
Monitoring: Veekijker
Circovirus
Increase in the number of questions in the first six months of 2024.
Animal category Quarter of the questions are about sows.
Monitoring: pathological examinations
Streptococcus suis Sepsis (septicaemia) caused by Streptococcus suis is the commonest diagnosis in pathological examinations.
Weaned piglets Weaned piglets are submitted most often: 36 percent of all submissions.
Online Monitoring
Respiratory symptoms
Health complaints
Respiratory complaints are the most frequent reports in the Online Monitor.
A health complaint is involved in 78 percent of the reports in the Online Monitor.
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.
