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Season Update on Pig Diseases

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Pig Diseases - Selected Highlights from the GB Emerging Threats Quarterly Report. Vol 21: Q3, July to September 2017

The following material is taken from the GB Emerging Threats Quarterly Report. Vol 21: Q3, July to September 2017. The full report can be found on the Animal & Plant Health Agency (APHA) web pages: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/664134/pub-survrep-p0317.pdf

For information about pig disease diagnosis and to access diagnostic support, please see:

http://ahvla.defra.gov.uk/vet-gateway/surveillance/diagnostic/index.htm

Antimicrobial resistance in pig scanning surveillance findings

In November 2017, the UK Veterinary Antibiotic Resistance and Sales Surveillance report for 2016 was released by VMD (VMD, 2017). This report contains antimicrobial resistance data derived from testing pathogens, including those from pigs, isolated during diagnostic investigations submitted to APHA's scanning surveillance network The report makes it clear that the resistance levels found in isolates from scanning surveillance are not indicative of actual prevalences of resistance as diagnostic submissions are often biased towards disease outbreaks which are severe, unresponsive and unusual. However, for pathogens isolated with reasonable frequency the report show interesting patterns and trends and it is useful for veterinary practitioners prescribing antibiotics for use in pigs to be aware of these. Encouragingly, colistin resistance was not detected in Escherichia coli or Salmonella isolates from diagnostic submissions from pigs in 2016.

Analysis of Diagnosis Not Reached (DNR) by syndrome and presenting sign

  • The DNR rate for submissions with a presenting sign of "Other" with reasonable testing in SAC CVS submissions was significantly increased to 33.3% in this quarter compared to 9.3% for the same quarter in prior years. Basic information from VIDA about all 10 undiagnosed cases with this presenting sign to Q3, 2017 was reviewed. The ages varied widely (one day to one year) and the disease syndromes were diverse (reproductive, digestive, musculoskeletal) and overall, these undiagnosed cases did not raise concern with respect to new and emerging disease.
  • The significant increase in DNR in Q2 2017 compared to prior years for musculoskeletal syndrome submissions which was described in the last quarterly report did not continue in Q3, 2017.
  • No other individual syndrome or presenting sign showed a significant increase in overall DNR in the first nine months of 2017 in GB submissions compared to the same period in prior years.

CHANGES IN DISEASE PATTERNS AND RISK FACTORS

Porcine circovirus 2-associated disease remains a threat to unvaccinated pigs

Porcine circovirus 2-associated disease (PCVD) was diagnosed on a nursery-finisher unit which suffered an outbreak of coughing and respiratory distress affecting approximately 50% of the pigs in the group. Fifty affected pigs died in a week. A submitted pig had pneumonia with generalised lymph node enlargement, marked splenomegaly and a necrotising colitis. Histopathology identified PCVD-like lesions in lung and lymph nodes and immunohistochemistry (IHC) for PCV2 confirmed the diagnosis. A review of procedures on the unit was undertaken and revealed that the affected group had inadvertently missed their PCV2 vaccination at weaning. A significant PCV2 challenge to unvaccinated pigs persists on units like the one involved here and emphasises the need to maintain vaccination for this virus.

Figure 1 shows the decline in the annual diagnostic rate of PCVD which largely reflects widespread vaccine use in the past decade.

PQU 18-01 F1

Figure 1: GB incidents of PCVD in pigs as % diagnosable submissions (2017 data incomplete, confidence intervals indicated by vertical lines)

A case report from Norway (Oropeza-Moe and others, 2017) also serves as a reminder of the potential for PCV2 to cause stillbirths, mummified piglets and weak neonatal piglets in certain epidemiological situations if sows undergo primary PCV2 infection while pregnant. Unusually in the reported incident, dead piglets were expelled three to four weeks after the expected farrowing date or were found in utero in the abattoir when gilts were culled. Histopathology and immunohistochemistry revealed myocarditis along with the presence of PCV2 in stillborn piglets confirming the diagnosis and a similar approach is taken at APHA for diagnosis of reproductive PCVD which has been confirmed on a few occasions. PCVD outbreaks have been highlighted in Veterinary Record monthly and GB Pig Quarterly disease surveillance reports to maintain awareness.

Features of porcine reproductive and respiratory syndrome diagnoses

This summer saw a more typical reduction in the diagnostic rate of PRRS unlike in 2016 as shown in the seasonality trend in the diagnostic rate of PRRS in Figure 2.

PQU 18-01 F2

Figure 2: Seasonality of PRRS GB diagnoses 2005-2017

The APHA submissions in which PRRS was diagnosed during 2016 and to September 2017 were reviewed and where age category was given, not surprisingly, 76% of diagnoses were in postweaned pigs.

Figure 3 shows the age distribution in weeks at the time of submission for pigs in which PRRS was diagnosed.

 

PQU 18-01 F3

Figure 3: Age of pigs in postweaned GB PRRS diagnoses 2016-17 (Age reported in weeks at time of submission; age was not stated for seven postweaned submissions

The main clinical sign reported is most commonly respiratory, with wasting and found dead also frequently reported. This is the same as reported in past years.

Whole carcase submissions generally allow fuller diagnostic investigation than non-carcase submissions and this is confirmed in the review of these 2016-2017 cases. In 60 carcase submissions with PRRS diagnosed, 11 yielded a diagnosis of PRRS only, while there was a total of 112 other diagnoses in the 49 other carcase submissions. In contrast, in 48 non-carcase submissions with PRRS diagnosed, 39 yielded a diagnosis of PRRS only, while just 10 other diagnoses were made in the nine other non-carcase submissions. The most frequent diagnoses concurrent with PRRS were streptococcal disease (mainly Streptococcus suis), Pasteurella multocida, swine influenza and salmonellosis. The immunosuppressive nature of PRRS is known and veterinarians recognise the role of PRRS underlying other endemic diseases.

Links to NADIS pages on PRRS in Weaners and PRRS in Breeding Herd

Mycoplasma hyorhinis involvement in PRRS disease outbreaks

Outbreaks of polyarthritis, with pneumonia and polyserositis due to Mycoplasma hyorhinis were confirmed affecting 5-10% of seven-week-old pigs on two indoor nursery-finisher units. Diarrhoea, weight loss, lameness and respiratory signs were described in pigs from weaning, with a poor response to antibiotic treatment. In both cases, the submitted pigs were found to also have interstitial pneumonias associated with PRRSV infection which was confirmed by both lung immunohistochemistry (IHC) and PCR detection. The pigs had been vaccinated for PRRS at weaning and IHC is a useful diagnostic tool in such cases to help determine whether the PRRS detected is clinically significant as it was in both these incidents. There are reports in the literature of Mycoplasma hyorhinis causing polyserositis including arthritis (Rovira, 2009) and also of the potential for exacerbation of respiratory disease where Mycoplasma hyorhinis is present with PRRSV (Lee and others, 2016). Whilst Haemophilus parasuis and Streptococcus suis remain the main causes of polyarthritis and polyserositis in this age of pig, additional specific testing for Mycoplasma species (DGGE-PCR) is merited as part of diagnostic investigations. Most outbreaks of disease in which Mycoplasma hyorhinis involvement has been demonstrated at APHA have also involved primary pathogens such as PRRS and prevention of concomitant infections is likely to help in reducing systemic spread of M. hyorhinis. There is a report in the literature that there is greater susceptibility to polyserositis in seven-week-old pigs experimentally infected with M. hyorhinis, which, interestingly, was the age of the pigs in both these incidents (Martinson and others, 2017).

Leptosipriosis outbreaks in jaundiced pigs

During September, Bury St Edmunds and Shrewsbury Veterinary Investigation Centres made diagnoses of leptospirosis in pre-weaned and post-weaned pigs showing jaundice. In one of these incidents, after being weaned, pigs developed jaundice and lethargy and started to lose condition. Six-week-old pigs submitted to Shrewsbury showed marked generalised jaundice (Figure 4) with perirenal oedema, some with cortical renal haemorrhages (Figure 5) and reddening/haemorrhage at the cortico-medullary junction. Kidney tissue tested positive for pathogenic leptospires by PCR. Testing sera from the cohorts of pigs for all 19 Leptospira serovars is recommended to identify the Leptospira serovar involved. Serology results pointed to involvement of L. Copenhageni, a rodent associated pathogenic leptospire, with one serum having a titre of 1/3200 indicating very recent infection. The other main differentials for jaundice in pigs include septicaemia, porcine circovirus 2-associated hepatitis, Mycoplasma suis and hepatotoxic agents (e.g. coal tar, ragwort) and awareness of the causes of jaundice in pigs was raised during a Clinical Club presentation at the November 2017 Pig Veterinary Society meeting. Although leptospirosis diagnoses are not numerous, the autumn occurrence of leptospirosis has been noted in previous years and may relate to rodent feed sources becoming scarcer and rodents (and possibly other wildlife) coming into greater contact with pigs when seeking food. Advice was provided on control of leptospire infection and measures to reduce risk of zoonotic infection from both infected pigs and rodents. As a routine, people working with pigs should wear outer clothing and boots dedicated to the pig unit and practise good personal hygiene. Gloves should be used to handle afterbirths, aborted and stillborn piglets, and when assisting at farrowings; they are also recommended for artificial inseminations and assisted matings. The particular concerns relevant to leptospire infection relate to contamination of people's mouths, noses, eyes or open wounds by pig urine, afterbirth, and aborted or stillborn piglets where there is reproductive disease. Effective rodent control is important as urine from infected rodents also represents a transmission risk to humans. These cases were also highlighted in the November Veterinary Record monthly surveillance report.

PQY 18-01 F4

Figure 4: Leptospirosis yellow-tinged sclera

PQU 18-01 F5

Figure 5: Leptospirosis: swollen kidney with haemorrhages

HORIZON SCANNING

Westward spread of African Swine Fever in Eastern Europe

The risk of introduction of African Swine Fever to the UK from the Continent has increased in 2017. This reinforces messages to pig keepers, veterinarians, food businesses and the public relating to preventing any pork or pork products being illegally (deliberately or accidentally) fed to pigs. It is more important than ever that pig keepers follow the rules and source their animal feed responsibly. Routinely providing dedicated clothing and boots for workers and visitors, limiting visitors to a minimum, and preventing outside vehicles which may be contaminated from coming on to pig premises, are valuable procedures for keeping out African swine fever as well as other diseases. Another phase of the APHA communication campaign to deter illegal waste feeding of pigs is underway. NADIS also recently issued an ASF disease information bulletin (White, 2017).

First report of resistance to toltrazail in piglet coccidiosis

Toltrazuril resistance has been confirmed experimentally in the Netherlands in Cystoisospora suis, the cause of piglet coccidiosis (Shrestha and others, 2017). The resistant parasite was from a case of piglet diarrhoea due to coccidiosis which persisted in spite of appropriate toltrazuril treatment on a farm in the Netherlands in 2014. C. suis is a relatively common endemic pathogen on pig farms globally. Coccidiosis due to C. suis and is mainly seen from 7-21 days of age, causing diarrhoea, poor growth and stunting in a number of piglets in litters, usually with low mortality unless complicated by other disease. Resistance would be of concern if found to be present in UK pig herds and would be a potential threat to pig health, welfare and production. There is no other effective and economically sustainable alternative treatment currently available and some of the disinfectants currently used routinely on pig farms do not kill coccidial oocysts. There are no simple tests for measuring resistance in coccidia and if reduced efficacy was suspected following investigation of treatment failure, an in vivo controlled treatment trial would be required to confirm resistance. This is technically demanding and expensive, would require specific funding and could only be performed under a suitable Home Office licence. VMD confirm that they have not to date received any reports of suspected lack of expected efficacy to toltrazuril in pigs through the Suspected Adverse Reaction Reporting System. Apparent treatment failure does not necessarily equate with the presence of resistance and investigation may reveal other causes, for example, treating at the wrong time, underdosing, or disease being caused by something other than coccidiosis. Where toltrazuril is used to prevent diarrhoea and wasting due to coccidiosis in young piglets, the aim is to apply treatment at an early stage of the parasite's cycle before clinical disease occurs, to arrest the developing stages while still 'exposing' the piglets to allow them to mount an effective immune response to the parasite. Correct timing of treatment according to veterinary advice is particularly important for successful control of piglet coccidiosis.

Porcine circovirus 3 reported in pigs

A novel porcine circovirus, porcine circovirus type 3 (PCV3) has been detected in samples from pigs with a variety of disease presentations from several countries including the US, China and Italy. Publications in 2016-17 have reported detection of PCV3 in cases of PDNS (Palinksi and others, 2017), reproductive failure (Faccini and others, 2017), respiratory disease, cardiac and multisystemic inflammation, sometimes with other pig pathogens. No experimental infections with PCV3 have been reported and no zoonotic concern is reported. There are also no reports published of systematic evaluation of PCV3 in healthy compared with diseased pigs and the significance of its detection requires further investigation. A report from Poland (Stadejek and others, 2017) showed that PCV3 was frequently detected in sera from Polish pigs but did not identify any association with unexplained disease. PCV3 detection has just been reported in archived samples in Northern Ireland (Collins and others, 2017) adding to information from an increasing number of countries which suggest it is widespread in pigs globally. This virus is distinct from PCV2 which is present in the UK pig herd and, as described above, disease associated with PCV2 has been largely controlled by widespread vaccination.

 

NADIS Update

Pig Diseases - Selected Highlights from the GB Emerging Threats Quarterly Report. Vol 21: Q3, July to September 2017

The following material is taken from the GB Emerging Threats Quarterly Report. Vol 21: Q3, July to September 2017. The full report can be found on the Animal & Plant Health Agency (APHA) web pages: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/664134/pub-survrep-p0317.pdf

For information about pig disease diagnosis and to access diagnostic support, please see:

http://ahvla.defra.gov.uk/vet-gateway/surveillance/diagnostic/index.htm

Antimicrobial resistance pig scanning surveillance findings

In November 2017, the UK Veterinary Antibiotic Resistance and Sales Surveillance report for 2016 was released by VMD (VMD, 2017). This report contains antimicrobial resistance data derived from testing pathogens, including those from pigs, isolated during diagnostic investigations submitted to APHA's scanning surveillance network The report makes it clear that the resistance levels found in isolates from scanning surveillance are not indicative of actual prevalences of resistance as diagnostic submissions are often biased towards disease outbreaks which are severe, unresponsive and unusual. However, for pathogens isolated with reasonable frequency the report show interesting patterns and trends and it is useful for veterinary practitioners prescribing antibiotics for use in pigs to be aware of these. Encouragingly, colistin resistance was not detected in Escherichia coli or Salmonella isolates from diagnostic submissions from pigs in 2016.

Analysis of Diagnosis Not Reached (DNR) by syndrome and presenting sign

· The DNR rate for submissions with a presenting sign of "Other" with reasonable testing in SAC CVS submissions was significantly increased to 33.3% in this quarter compared to 9.3% for the same quarter in prior years. Basic information from VIDA about all 10 undiagnosed cases with this presenting sign to Q3, 2017 was reviewed. The ages varied widely (one day to one year) and the disease syndromes were diverse (reproductive, digestive, musculoskeletal) and overall, these undiagnosed cases did not raise concern with respect to new and emerging disease.

· The significant increase in DNR in Q2 2017 compared to prior years for musculoskeletal syndrome submissions which was described in the last quarterly report did not continue in Q3, 2017.

· No other individual syndrome or presenting sign showed a significant increase in overall DNR in the first nine months of 2017 in GB submissions compared to the same period in prior years.


CHANGES IN DISEASE PATTERNS AND RISK FACTORS

Porcine circovirus 2-associated disease remains a threat to unvaccinated pigs

Porcine circovirus 2-associated disease (PCVD) was diagnosed on a nursery-finisher unit which suffered an outbreak of coughing and respiratory distress affecting approximately 50% of the pigs in the group. Fifty affected pigs died in a week. A submitted pig had pneumonia with generalised lymph node enlargement, marked splenomegaly and a necrotising colitis. Histopathology identified PCVD-like lesions in lung and lymph nodes and immunohistochemistry (IHC) for PCV2 confirmed the diagnosis. A review of procedures on the unit was undertaken and revealed that the affected group had inadvertently missed their PCV2 vaccination at weaning. A significant PCV2 challenge to unvaccinated pigs persists on units like the one involved here and emphasises the need to maintain vaccination for this virus.

Figure 1 shows the decline in the annual diagnostic rate of PCVD which largely reflects widespread vaccine use in the past decade.

Figure 1: GB incidents of PCVD in pigs as % diagnosable submissions (2017 data incomplete, confidence intervals indicated by vertical lines)

A case report from Norway (Oropeza-Moe and others, 2017) also serves as a reminder of the potential for PCV2 to cause stillbirths, mummified piglets and weak neonatal piglets in certain epidemiological situations if sows undergo primary PCV2 infection while pregnant. Unusually in the reported incident, dead piglets were expelled three to four weeks after the expected farrowing date or were found in utero in the abattoir when gilts were culled. Histopathology and immunohistochemistry revealed myocarditis along with the presence of PCV2 in stillborn piglets confirming the diagnosis and a similar approach is taken at APHA for diagnosis of reproductive PCVD which has been confirmed on a few occasions. PCVD outbreaks have been highlighted in Veterinary Record monthly and GB Pig Quarterly disease surveillance reports to maintain awareness.

Features of porcine reproductive and respiratory syndrome diagnoses

This summer saw a more typical reduction in the diagnostic rate of PRRS unlike in 2016 as shown in the seasonality trend in the diagnostic rate of PRRS in Figure 2.

Figure 2: Seasonality of PRRS GB diagnoses 2005-2017

The APHA submissions in which PRRS was diagnosed during 2016 and to September 2017 were reviewed and where age category was given, not surprisingly, 76% of diagnoses were in postweaned pigs. Figure 3 shows the age distribution in weeks at the time of submission for pigs in which PRRS was diagnosed.

Text Box: Figure 3: Age of pigs in postweaned GB PRRS diagnoses 2016-17 (Age reported in weeks at time of submission; age was not stated for seven postweaned submissions)

The main clinical sign reported is most commonly respiratory, with wasting and found dead also frequently reported. This is the same as reported in past years.

Whole carcase submissions generally allow fuller diagnostic investigation than non-carcase submissions and this is confirmed in the review of these 2016-2017 cases. In 60 carcase submissions with PRRS diagnosed, 11 yielded a diagnosis of PRRS only, while there was a total of 112 other diagnoses in the 49 other carcase submissions. In contrast, in 48 non-carcase submissions with PRRS diagnosed, 39 yielded a diagnosis of PRRS only, while just 10 other diagnoses were made in the nine other non-carcase submissions. The most frequent diagnoses concurrent with PRRS were streptococcal disease (mainly Streptococcus suis), Pasteurella multocida, swine influenza and salmonellosis. The immunosuppressive nature of PRRS is known and veterinarians recognise the role of PRRS underlying other endemic diseases.

Links to NADIS pages on PRRS in Weaners and PRRS in Breeding Herd

Mycoplasma hyorhinis involvement in PRRS disease outbreaks

Outbreaks of polyarthritis, with pneumonia and polyserositis due to Mycoplasma hyorhinis were confirmed affecting 5-10% of seven-week-old pigs on two indoor nursery-finisher units. Diarrhoea, weight loss, lameness and respiratory signs were described in pigs from weaning, with a poor response to antibiotic treatment. In both cases, the submitted pigs were found to also have interstitial pneumonias associated with PRRSV infection which was confirmed by both lung immunohistochemistry (IHC) and PCR detection. The pigs had been vaccinated for PRRS at weaning and IHC is a useful diagnostic tool in such cases to help determine whether the PRRS detected is clinically significant as it was in both these incidents. There are reports in the literature of Mycoplasma hyorhinis causing polyserositis including arthritis (Rovira, 2009) and also of the potential for exacerbation of respiratory disease where Mycoplasma hyorhinis is present with PRRSV (Lee and others, 2016). Whilst Haemophilus parasuis and Streptococcus suis remain the main causes of polyarthritis and polyserositis in this age of pig, additional specific testing for Mycoplasma species (DGGE-PCR) is merited as part of diagnostic investigations. Most outbreaks of disease in which Mycoplasma hyorhinis involvement has been demonstrated at APHA have also involved primary pathogens such as PRRS and prevention of concomitant infections is likely to help in reducing systemic spread of M. hyorhinis. There is a report in the literature that there is greater susceptibility to polyserositis in seven-week-old pigs experimentally infected with M. hyorhinis, which, interestingly, was the age of the pigs in both these incidents (Martinson and others, 2017).

Leptospirosis outbreaks in jaundiced pigs

During September, Bury St Edmunds and Shrewsbury Veterinary Investigation Centres made diagnoses of leptospirosis in pre-weaned and post-weaned pigs showing jaundice. In one of these incidents, after being weaned, pigs developed jaundice and lethargy and started to lose condition. Six-week-old pigs submitted to Shrewsbury showed marked generalised jaundice (Figure 4) with perirenal oedema, some with cortical renal haemorrhages (Figure 5) and reddening/haemorrhage at the cortico-medullary junction. Kidney tissue tested positive for pathogenic leptospires by PCR. Testing sera from the cohorts of pigs for all 19 Leptospira serovars is recommended to identify the Leptospira serovar involved. Serology results pointed to involvement of L. Copenhageni, a rodent associated pathogenic leptospire, with one serum having a titre of 1/3200 indicating very recent infection. The other main differentials for jaundice in pigs include septicaemia, porcine circovirus 2-associated hepatitis, Mycoplasma suis and hepatotoxic agents (e.g. coal tar, ragwort) and awareness of the causes of jaundice in pigs was raised during a Clinical Club presentation at the November 2017 Pig Veterinary Society meeting. Although leptospirosis diagnoses are not numerous, the autumn occurrence of leptospirosis has been noted in previous years and may relate to rodent feed sources becoming scarcer and rodents (and possibly other wildlife) coming into greater contact with pigs when seeking food. Advice was provided on control of leptospire infection and measures to reduce risk of zoonotic infection from both infected pigs and rodents. As a routine, people working with pigs should wear outer clothing and boots dedicated to the pig unit and practise good personal hygiene. Gloves should be used to handle afterbirths, aborted and stillborn piglets, and when assisting at farrowings; they are also recommended for artificial inseminations and assisted matings. The particular concerns relevant to leptospire infection relate to contamination of people's mouths, noses, eyes or open wounds by pig urine, afterbirth, and aborted or stillborn piglets where there is reproductive disease. Effective rodent control is important as urine from infected rodents also represents a transmission risk to humans. These cases were also highlighted in the November Veterinary Record monthly surveillance report.

Figure 4: Leptospirosis: yellow-tinged sclera

Figure 5: Leptospirosis: swollen kidney with haemorrhages

 

 


HORIZON SCANNING

Westward spread of African Swine Fever in Eastern Europe

The risk of introduction of African Swine Fever to the UK from the Continent has increased in 2017. This reinforces messages to pig keepers, veterinarians, food businesses and the public relating to preventing any pork or pork products being illegally (deliberately or accidentally) fed to pigs. It is more important than ever that pig keepers follow the rules and source their animal feed responsibly. Routinely providing dedicated clothing and boots for workers and visitors, limiting visitors to a minimum, and preventing outside vehicles which may be contaminated from coming on to pig premises, are valuable procedures for keeping out African swine fever as well as other diseases. Another phase of the APHA communication campaign to deter illegal waste feeding of pigs is underway. NADIS also recently issued an ASF disease information bulletin (White, 2017).

First report of resistance to toltrazil in piglet coccidiosis

Toltrazuril resistance has been confirmed experimentally in the Netherlands in Cystoisospora suis, the cause of piglet coccidiosis (Shrestha and others, 2017). The resistant parasite was from a case of piglet diarrhoea due to coccidiosis which persisted in spite of appropriate toltrazuril treatment on a farm in the Netherlands in 2014. C. suis is a relatively common endemic pathogen on pig farms globally. Coccidiosis due to C. suis and is mainly seen from 7-21 days of age, causing diarrhoea, poor growth and stunting in a number of piglets in litters, usually with low mortality unless complicated by other disease. Resistance would be of concern if found to be present in UK pig herds and would be a potential threat to pig health, welfare and production. There is no other effective and economically sustainable alternative treatment currently available and some of the disinfectants currently used routinely on pig farms do not kill coccidial oocysts. There are no simple tests for measuring resistance in coccidia and if reduced efficacy was suspected following investigation of treatment failure, an in vivo controlled treatment trial would be required to confirm resistance. This is technically demanding and expensive, would require specific funding and could only be performed under a suitable Home Office licence. VMD confirm that they have not to date received any reports of suspected lack of expected efficacy to toltrazuril in pigs through the Suspected Adverse Reaction Reporting System. Apparent treatment failure does not necessarily equate with the presence of resistance and investigation may reveal other causes, for example, treating at the wrong time, underdosing, or disease being caused by something other than coccidiosis. Where toltrazuril is used to prevent diarrhoea and wasting due to coccidiosis in young piglets, the aim is to apply treatment at an early stage of the parasite's cycle before clinical disease occurs, to arrest the developing stages while still 'exposing' the piglets to allow them to mount an effective immune response to the parasite. Correct timing of treatment according to veterinary advice is particularly important for successful control of piglet coccidiosis.

Porcine circovirus 3 reported in pigs

A novel porcine circovirus, porcine circovirus type 3 (PCV3) has been detected in samples from pigs with a variety of disease presentations from several countries including the US, China and Italy. Publications in 2016-17 have reported detection of PCV3 in cases of PDNS (Palinksi and others, 2017), reproductive failure (Faccini and others, 2017), respiratory disease, cardiac and multisystemic inflammation, sometimes with other pig pathogens. No experimental infections with PCV3 have been reported and no zoonotic concern is reported. There are also no reports published of systematic evaluation of PCV3 in healthy compared with diseased pigs and the significance of its detection requires further investigation. A report from Poland (Stadejek and others, 2017) showed that PCV3 was frequently detected in sera from Polish pigs but did not identify any association with unexplained disease. PCV3 detection has just been reported in archived samples in Northern Ireland (Collins and others, 2017) adding to information from an increasing number of countries which suggest it is widespread in pigs globally. This virus is distinct from PCV2 which is present in the UK pig herd and, as described above, disease associated with PCV2 has been largely controlled by widespread vaccination.