Streptococcus suis: struggling against disease

Transcription

1 Streptococcus suis: struggling against disease Marcelo Gottschalk, DVM, PhD Faculty of Veterinary Medicine University of Montreal, Canada

2 Number of publications on S. suis throughout the years

3 Streptococcus suis One of the most important bacterial pathogen during the post-weaning period (worldwide distribution) Meningitis, septicemia with sudden death, polyserositis, endocarditis, arthritis, some role in pneumonia (?) A total of 35 described serotypes Serotypes 20, 22, 26, 32, 33, 34: not Streptococcus suis Some serotypes more important than other serotypes Zoonosis: mainly serotype 2, followed by serotypes 14 and 5

4 S. suis: diagnosis Clinical signs depending on the clinical signs; septicemia: spleen hypertrophy; from sudden death to arthritis; pneumonia? Age of affected animals newly weaned pigs; less frequent: nursing piglets (difficult to diagnose; some cases (arthritis) misidentified); finisher pigs, rare: increase of resistance with age? Differential diagnosis Glasser s disease, Edema disease, salt intoxication

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6 S. suis infections

7 S. suis infections

8 S. suis infections

9 S. suis infections Glässer-like disease: possible with S. suis

10 S. suis: diagnosis Isolation Serotyping, virulence factors and sequence types Antimicrobial susceptibility test Genotyping

11 S. suis: diagnosis Isolation Serotyping, virulence factors and sequence types Antimicrobial susceptibility test Genotyping

12 S. suis: Microbiological diagnosis Samples Based on clinical signs and gross pathology Live or freshly antibiotic free pig Swabs or tissue samples at the farm NOT TONSILLAR OR NASAL SWABS Normal inhabitants before and after weaning Attention with lungs (discussed later)

13 S. suis: diagnosis Isolation, identification and serotyping (clinical disease) Attention with secondary invasion of alpha-hemolytic streptococci: diagnostic labs might misidentify them as S. suis Pure or predominant culture Identification by biochemical tests; MALDI-TOF: good results but only with clinical isolates (not tonsillar isolates) Direct PCR detection not routinely used Serotyping Past: few laboratories had all antisera for serotyping Now: at least 3 different PCR techniques for serotyping

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15 S. suis and pneumonia Lung consolidation Chronic pleuresy

16 S. suis: pneumonia? S. suis in pneumonia Not necessarily always a primary pathogen Difficult to reproduce lung lesions during experimental infections: usually as a result of septicemia Attention: 10-20% healthy lungs: S. suis isolation (discuss later with Australian data) BALF: 67% of positive isolation in healthy animals = low specificity Pure culture (or highly predominating); usually in association with other respiratory pathogens Septicemia: isolates in internal organs are sometimes different from those recovered from lungs

17 S. suis: diagnosis Isolation Serotyping, virulence factors and sequence types Antimicrobial susceptibility test Genotyping

18 Distribution of S. suis serotype 2 in different countries Country Serotype 2 from clinical cases France 59% Spain* 31% Italy 42% Netherlands* 30% UK Australia 45% No data in the last 25 years** Canada/USA <15% *These countries have recent data; serotype 9 seems to be important in these countries

19 Distribution of S. suis serotype 2 in different countries Country Serotype 2 from clinical cases France 59% Spain* 31% Italy 42% Netherlands* 30% UK Australia 45% No data in the last 25 years** Canada/USA <15% *These countries have recent data; serotype 9 seems to be important in these countries **Serotypes 1, 2, 1/2, 7 and 9 had been described

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21 serotype 2!!!

22 S. suis: Australia: more recent data* Diseased pigs (PCR for serotypes 2, 1/2, 1, 14, 7 and 9 used) Serotype 2 or 1/2 (30%) Serotype 9 (10%) Serotype 1 or 14 (9%) Serotype 7 (3%) It would be important to differentiate serotypes 2 from 1/2 and 1 from 14 *Mitchell Dean Groves thesis, The University of Queensland, data sent by Dr. Sam Abraham Murdoch University

23 Distribution of S. suis serotype 2 in different countries Country Serotype 2 from clinical cases France 59% Spain* 31% Italy 42% Netherlands* 30% UK Australia 45% 30% Canada/USA <15% *Serotype 9 seems to be important in these countries

24 S. suis: Prevalence in Canada: From January 2013 to December 2016 (2592 isolates) Serotype % Serotype % Serotype % Serotype % 1 4 % 10 <1 % 20 0 % 30 <1 % 2 10% 11 <1 % 21 <1 % 31 <1 % 1/2 7 % 12 0 % 22 1 % 32 <1 % 3 4 % 13 0 % 23 1 % 33 0 % 4 5 % 14 2 % 24 <1 % 34 1 % 5 3 % 15 <1 % 25 <1 % UT 18 %* 6 0 % 16 1,5 % 26 0 % 7 3,5 % 17 0 % 27 <1 % 8 3 % 18 <1 % 28 <1 % 9 2 % 19 <1 % 29 1 % *At least 50% of these without cps locus (impossible to serotype)

25 S. suis: serotype distribution in pigs (from 2002 to present) 2, 9 2, 1/2, 3, 4, 7 2,3 2 2 or 1/2, 9, 1 or 14?

26 Using MLST to compare S. suis serotype 2 strains S. suis serotype 2: different sequence types or ST ST25 ST1 ST28 26

27 MLST of S. suis serotype 2 strains ST1 ST7, ST1 ST1 (ST28) ST25, ST28 ST1 ST1, ST104 ST1?

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29 MLST of S. suis serotype 2 strains ST1 ST7, ST1 ST1 (ST28) ST25, ST28 ST1 ST1, ST104 ST1 ST25, ST1

30 Different ST, different virulence Virulence : ST1 (EUROPE) > ST25 (NA) > ST28 (NA)

31 Virulence factors (?): serotype 2 Capsular polysaccharide Serotype Virulent and non-virulent strains of serotype 2 do exist Hemolysin: SLY (sly) (not critical, but good correlation) Cell wall associated and extracellular proteins: MRP (mrp) and EF (epf) (not critical, but good correlation) Hundreds of papers (mostly from China) published in the last 5 years showing critical virulence factors A great confusion on virulence factors

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33 S. suis: «sequence types» of serotype 2 ST1 strains must be under surveillance MLST: longer and more expensive test PCR tests may help to identify and differentiate higher/lower virulent serotype 2 strains mrp +, epf +, sly + : ST1 strains Probably intermediate virulent NA ST25 strains mrp v, epf -, sly - Probably less virulent NA ST28 strains mrp +, epf -, sly Note: mrp+ = full length gene

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35 Strains isolated from diseased pigs ST28 ST25 ST1 Mitchell Dean Groves thesis, The University of Queensland, data sent by Dr. Sam Abraham, Murdoch University

36 S. suis: serotype distribution in pigs (from 2002 to present) 2 = 9 2, 1/2, 3, 4, 7 2, or 1/2, 9, 1 or 14? Spain, Germany, Netherlands, Italy: serotype 9 is very important

37 S. suis serotype 9: highly virulent in Australia? Strains from Spain More frequently isolated than serotype 2 ST125 and ST123 Homogeneous All sly + Strains from Canada Very few cases and mostly associated to PRRSv 10 different STs; very heterogeneous 90% of the strains: sly -

38 S. suis serotype 9: highly virulent in Australia? Strains from Spain More frequently isolated than serotype 2 ST125 and ST123 Homogeneous All sly + Strains from Canada Very few cases and mostly associated to PRRSv 10 different STs; very heterogeneous 90% of the strains: sly -

39 S. suis: primary pathogen? Yes Virulent strains; more common in Europe Usually one single serotype involved in clinical cases in a herd Insidious and important disease in many herds No Different serotypes acting within one herd Respiratory problems? Highly affected by management and environment Concomitant diseases: PRRS, Influenza, PCV2?, Mycoplasma?, others?

40 S. suis: primary pathogen? Australia??? Serotype 2 important; need to differentiate from serotype 1/2 Virulence of Australian serotype 2: a mixture of European and NA profiles Serotype 9 also seems to be important but lower virulence strains? to be confirmed If not PRRSv, which other factors contribute to the development of disease? More complete studies are needed

41 S. suis: primary pathogen? Diagnosis (again) Necropsy of 2-3 animals: ideally, euthanized Material sent to the lab Isolation: S. suis (pure culture or predominant) Serotyping Same serotype: an indication of primary pathogen 2-3 different serotypes: look for predisposing factors while treatment begins

42 S. suis + other co-infections? PRRSV PCV2: associations; experimentally not demonstrated Mycoplasma? 4-6 weeks of age: purulent pneumonia with fibrin; predominant culture of S. suis and M. hyorhinis; increased cases of meningitis by S. suis Tulathromycin (once at weaning) Coughing, sneezing and respiratory signs almost disappeared Improvement in feed conversion and average daily gain Reduction in the number of treatment days with beta-lactams in water Reduction in the frequency, severity and mortality of S. suis episodes This is just an example how difficult the diagnosis may be

43 S. suis: diagnosis Isolation Serotyping, virulence factors and sequence types Antimicrobial susceptibility test Genotyping

44 S. suis: antimicrobial susceptibility Susceptible Most beta-lactams No production of beta-lactamases Decrease of susceptibility: penicillin-binding proteins (it takes many years..) Resistant Tetracyclines, clindamycin, erythromycin Variable Trimethoprim/sulfa

45 Antimicrobial susceptibility of European strains of S. suis % of resistant strains % of susceptible strains Penicillin G 3 97 Amoxicillin 3 97 Amx-clavulanic acid 3 97 Ampicillin Ceftiofur 5 95 Enrofloxacin Erythromycin Tetracycline TMT/Sulfa Strains from tonsils (non-virulent strains) are usually highly resistant

46 S. suis: diagnosis Isolation Serotyping, virulence factors and sequence types Antimicrobial susceptibility test Genotyping

47 Different animals Different farms Same or different serotypes Different tissues Comparison purposes

48 S. suis: genotyping Usually, more than one strain belonging to the same serotype within one farm If highly virulent, only one is usually responsible for the clinical signs High heterogeneity when strains from different farms are compared A very few «virulent» strains are present in a pyramidal system (primary infection)

49 Distribution of the different patterns of isolates of S. suis serotype 5 in piglets

50 New serious cases due to S. suis Two epidemiological situations 1. A new pathogenic strain that has been incorporated to the herd 2. Clinical expression with a previoulsy present strain in the herd: something changed in the conditions of the herd Co-infections Overcrowding Mixing of litters Variation in temperature Ventilation Changes in the pig flow Other problems of management Stress related to weaning from intestine???

51 Transmission of S. suis? Fomites Humans? Flies? High percentage of animals are all carriers of S. suis Vagina: from sows to piglets Tonsils: from sows to piglets and among piglets Less frequent (high frequent if clinical signs): nasal cavities Intestine? Route of infection Respiratory route including aerosol Oral route?

52 The pathogenesis of the infection caused by S. suis S. suis GI tract????? Respiratory tract?? Tonsils: healthy carrier Bloodstream Bacteremia, septicemia Bacterial survival?? Sudden death, other infections CNS Inflammation Meningitis

53 S. suis through oral route? Experimental infection Serotypes 2 and 9 1 x bacteria (10 x of dose used for intranasal infections) No clinical signs Absence of isolation in Intestinal lymph nodes Internal organs These results suggest that S. suis would have problems to survive in pig s stomach (weaned piglets) S. suis does not seem to survive in feed More studies are needed before reaching definitive conclusions

54 S. suis through oral route? S. suis cases: 2-4 weeks after weaning Heaviest piglets? High volume of sow milk: poor adaptation to solid feed: do not consume adequate nutrients for 2-4 days after weaning Low feed intake: villous atrophy Then piglets begin to eat large amount of feed (relatively to their body weight): limited blood/oxygen supply to the gut (hypoxia) Modification of the flora, inflammation Increased permeability invasion of S. suis intestinal problems + stress = S. suis problems?

55 S. suis through oral route? Hypothesis: S. suis may colonize the intestine in younger animals? Changes in the intestine during the first days of weaning may have an impact on S. suis disease Stress (intestine inflammation, general secretions of cytokines, etc) Direct invasion from the intestine?: more studies on the presence of S. suis in the G.I. tract There are many feed additive products that have been described to be toxic for S. suis in vitro Sugar beet pulp; fatty acids, lauric acids; omega 3, etc. No conclusive results in vivo: first, invasion of S. suis from the intestine must be confirmed Frequent small meals in the first 3 to 4 days after weaning might help?

56 S. suis infections: diagnosis of subclinically infected animals? Study in Canada Nasal and tonsillar swabs and PCR (different pathogens) All but one herd positive for S. suis 48% of herds positive for serotypes 2 and/or 1/2 More than 90% of animals positive for S. suis Diagnosis of herds infected by virulent strains of S. suis In Europe (not in NA, partially useful in Australia ): PCR for virulence markers (mrp, epf, sly: typical of virulent ST1 serotype 2 strains) may be used; We do have PCR for all serotypes: Specificity? Sensitivity? Useful (more than one strain belonging to the same serotype are usually present)

57 S. suis infections: diagnosis of subclinically infected animals? There is no validated serological test (even if a few publications claim the opposite not validated) Strain-specific ELISA to follow-up antibodies in a given herd

58 Treatment of clinical cases Individual treatment Beta-lactams: one or several doses, depending on the product; florfenicol also works well Anti-inflammatory products (optional) parenterally S. suis-affected animals (even with meningitis) may respond well to good treatments Be sure animals drink: give water (orally or rectal) Diseased animals must be separated from healthy ones!!! In Canada: prophylactic treatment can be done if you cannot: identification of animals with fever and treatment as soon as possible

59 S. suis infections: Control Control of predisposing factors Antimicrobial preventive medication Vaccination

60 S. suis infections: Predisposing factors Overcrowding Poor ventilation, high humidity, inadequate sanitation Mixing pigs of different ages Important temperature variation between night and day High levels of dust and ammonia Mycotoxins? Low levels of vitamin E? Almost everything affecting good management of animals has been associated to S. suis disease

61 Control of S. suis infections: medication Antibiotic treatment of piglets (preweaning) Previous to risk period: still in Canada, not allowed in many EU countries Treatment in water Amoxicillin Less frequently: florfenicol, TM+S (if susceptible) Problems in organic and humane farms Very low level of antimicrobial resistance against beta-lactams in general

62 Control of S. suis infections: medication Antibiotic treatment of sows and/or newborn piglets with strong antibiotics Sows Reduction of transmission? Ceftiofur, enrofloxacin, other antibiotics No scientific data Newborn/suckling piglets Used often in some countries (Spain, Mexico) Almost no scientific studies Results seem to indicate two situations Improvement on mortality and clinical signs Increase of mortality and clinical signs

63 Control of S. suis infections: medication Antibiotic treatment of sows and/or newborn piglets with strong antibiotics Sows Reduction of transmission? Ceftiofur, enrofloxacin, other antibiotics No scientific data Newborn/suckling piglets Used often in some countries (Spain, Mexico) Almost no scientific studies Results seem to indicate two situations Improvement on mortality and clinical signs Increase of mortality and clinical signs

64 Vaccines Bacterins Commercial Autogenous Live vaccines Sub-unit vaccines

65 Control of S. suis infections: vaccination Serotype-specific bacterins Very few are commercial: serotype 2 ST1 strain; protection against different serotype 2 strains??? Mostly: autogenous Protection in the field is controversial depending on the country Pigs If any antibody production: interference with maternal antibodies? Sows Might be good (?) if young suckling animals affected? How to explain protection of post-weaned piglets? Reduction of bacterial transmission from sows to piglets: probably not

66 Kinetics of anti-s. suis type 1/2 antibodies (proteins) in piglets from a clinically affected herd optical density Age (weeks)

67 Prevention of the disease: vaccination ELISA S/P RATIO AGE

68 Prevention of the disease: vaccination Response amplitude S/P Ratio at 2 weeks

69 Bacterins in piglets Bacterins Interference with maternal antibodies (anti-protein antibodies: specific? Non-specific?) In young animals, whole bacteria do not induce high level of antibodies Levels of antibodies against the capsular polysaccharide (capsule: serotype) are even lower: protective antibodies?

70 Bacterins in piglets Bacterins First: be sure that most cases are caused by a single serotype: otherwise, useless. If you have 3-4 different serotypes to be included in the vaccine: it will (usually) not work I would always begin with piglet vaccination if clinical cases are after 6-7 weeks of age The lab should have good experience (bacterial concentration; adjuvant) Second dose: at least 10 days before the appearance of clinical signs Do not expect miracles Work on predisposal factors: usually, is the best way to control this disease

71 Bacterins in sows: the controversy Bacterins: may be useful for clinical signs in young piglets? Vaccinated 6-7 weeks pre-partum and boostered 4 weeks later In the next cycle sows receive only 1 booster 2-3 weeks prepartum Around 10% of sow herds in France and The Netherlands routinely use autogenous vaccines in sows for S. suis In some cases, it seems that this approach may work However, usually without control group (field studies) In many cases, different measures (+ autogenous vaccines) are applied at the same time; sometimes difficult to specifically evaluate the effect of the vaccine In some cases the disease disappear without knowing exactly why

72 Bacterins in sows: our preliminary results Herd with disease to S. suis serotype 7: suckling piglets (farrow-to-feeder operation) Bacterin (with 3 other pathogens) used in sows Owner says problems have been controlled also in grower animals Does the vaccine increase the levels of antibodies? How much time the antibodies last in piglets? Are these antibodies protective?

73 Sows Pre-vaccination Post-1 st dose Post-2 nd dose First dose Second dose

74 PIGLETS

75 S. suis S. suis S. suis S. suis Phagocytic cell (macrophage, neutrophile, etc.)

76 Opsonophagocytosis with antibodies S. suis Fc «Good» anti-s. suis antibodies Cell receptor for the antibodies Phagocytic cell (macrophage, neutrophile, etc.)

77 Opsonophagocytosis killing assay Blood leucocytes from a healthy pig Incubation S. suis (from the vaccine) Serum Control or Immunized Count number of bacteria alive

78 Bacterins in sows: are antibodies protective? Sows (post-boost) Piglets (7 days) Piglets (18 days)

79 Bacterins in sows to protect weaned piglets? Levels of antibodies in sows against S. suis (or other crossreacting antibodies) does not increase after two doses Maternal antibodies against S. suis do not last more than 3 weeks Some protection in young piglets might be achieved No explanation for a possible protection in post-weaned piglets Still more research to do Three dosis in sows significanlty increase the level of antibodies Bacterial concentration? Adjuvants? Trasmission of immune cells from sow to piglets?

80 Bacterins in sows to protect weaned piglets If disease is present in young piglets Again: only one serotype largely predominates among diseased pigs Vaccines working in the field? Controlled studies needed: clear differences between vaccinated and non vaccinated animals Try to find explanations if success is confirmed Production of bacterins (concentration, adjuvant) may differ? Cellular immunity?: Piglets from vaccinated sows: increased antibody production very faster after natural infection? (compared with piglets from non-vaccinated sows?): to be tested

81 Vaccines Bacterins Commercial Autogenous Live vaccines Sub-unit vaccines

82 Results obtained with live vaccines in pigs Strain Protection Reference Serotype 5* Yes (heterologous: 2 and 9) Jiang et al., 2016 Unencapsulated Partial Fittipaldi et al., 2007 Unencapsulated No Wisselink et al., 2002 Non-virulent encapsulated (ST28)** Yes Busque et al., 1997 Virulent Yes Schmitt et al., 2001 Virulent Yes Holt et al., 1990 *Study not scientifically sound; **Three doses needed

83 Vaccines Bacterins Commercial Autogenous Live vaccines Sub-unit vaccines

84 Sub-unit vaccines Proteins? MRP, EF, SLY: partial protection (if the strain is positive ); only serotype 2; Proteins: with the arrival of many studies from China, new 100% protective antigens are constantly described : so far more than 40 protective factors described!!! As examples DPPIV Enolase Both described as highly protective

85 Percent survival SsEno + Polygen SsEno + Montanide SsEno + QuilA SsEno + Stimune non-immunized Time (days) Percent survival DppIV + Polygen DppIV + Montanide DppIV + QuilA DppIV + Stimune non-immunized Time (days)

86 Vaccines: what do we presently have? Bacterins Commercial Autogenous:??? Live vaccines Sub-unit vaccines

87 Why is difficult to struggle against S. suis disease? Most animals are carriers of S. suis A few diagnostic tools to identify virulent strains; some for for serotype 2 (not all strains) Disease caused by virulent strains and/or by less virulent strains with the help of concomitant factors The only working option to control disease is still antibiotic metaphylaxis which is not allowed in some countries Still no good commercial vaccine available: we need to prove that autogenous vaccines are really working, since it seems the only immunogen to be used so far Good subunit universal vaccines are needed Still not possible to eradicate

88 Thank you