Update on Staphylococcus aureus Mastitis John R. Middleton College of Veterinary Medicine, University of Missouri, Columbia 1
Staphylococcus aureus Gram-positive, facultatively anaerobic, non-motile, non-sporulating, catalase positive, coagulasepositive, hemolytic coccus. 2
Staphylococcus aureus Most prevalent contagious pathogen Most often subclinical Milk quality Milk yield Chronic infections Intermittent clinical flare-ups Fluctuating SCC and bacteria counts Occasional severe (Toxic) mastitis Variable response to treatment 3
1961 The increase in the importance of staphylococcal mastitis since the advent of the antibiotics and the fact that many of these organisms are resistant to penicillin have caused some anxiety to those interested in milk production. 4
1961 Quantitative analysis suggests that most infections of other sites were secondary to infection of the udder. 5
The 5-Point Plan - 1969 Mastitis has been and continues to be the most costly dairy cattle disease A true mastitis control program must be directed towards prevention 6
S. aureus Mastitis Implementation of the 5-point plan has led to a sizeable reduction in S. aureus mastitis on many farms. Individual herds can still be plagued with the disease and, depending on chronicity and transmissibility within herd, it can be difficult to eradicate. 7
Pathogenesis Mammary epithelial cell Fnbp or direct cell to cell interaction S. aureus 8
Evasion of Host Defenses SpA Low Ab PMN Capsule Fat Casein S. aureus 9
Pathogenesis Once established in gland Ulceration and erosion of tissues Tissue infiltration with inflammatory cells Damage to secretory epithelial cells leading to occlusion of ducts & alveoli, trapping S. aureus Granulomas and microabscesses Nidus of infection for other parts of gland Produces numerous toxins and enzymes Role? Superantigens Tissue damage 10
Streak Canal and lining of Keratin Contagious Canal Environmental 11
Sources of Infection Heifer Udder Skin 13% Cows @ Part. Heifer Udder Skin 67% 67% Cows @ Part. Roberson et al. 39% Lact. Pop. 71% Heifers @ Part. 18% Cows @ Part. Heifer Udder Skin 47% Heifers @ Part. Heifers @ Part. Roberson et al. 70% 12
Flies Haematobia irritans Capable of transmitting S. aureus to heifers Owens et al., 1998 Herds that practiced effective fly control Lower risk of early lactation contagious pathogen IMI in heifers Nickerson et al., 1995 Piepers et al., 2011 13
Epidemiology λ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 λ 14
Epidemiology Study of NW U.S. dairies with a prevalence of S. aureus IMI 10% 43 strains 38/43 (88.4%) Unique to one herd 5/43 (11.6%) found in >1 herd 7/8 (87.5%) herds had >1 strain 6/8 (75.0%) herds had a predominant strain type Accounted for 53-100% of isolates Milk SCC and NAGase did not differ between strains (P 0.046) within herd. 15
Influence of Strain on Milk Yield Group 1 = Novel strain infected cattle Group 2 = Other strains of S. aureus Cow 167 = ATCC 29740 Cows 233 & 543 = Strain 233 Cows 381 and 549 = Strain 381 Cow ID Mean kg Milk Mean kg Milk Control Quarter Infected Quarter Group 1: 75 1.29 0.45 97 6.58 3.49 153 3.86 2.29 164 1.56 0.00 201 1.95 0.77 209 2.11 0.00 226 5.40 4.04 353 2.47 0.00 3.15 * 1.38 * Group 2: 167 0.36 3.86 232 5.96 3.97 233 1.54 1.91 543 0.52 0.00 381 3.90 3.83 549 2.23 2.20 2.42 # 2.63 # * Overall means for group one. Infected mammary quarters produced significantly less milk than the contralateral control mammary quarters (P = 0.007). # Overal means for group two. Milk production was not significantly different between infected and control mammary quarters (P = 0.834). 16
Biosecurity Study of 15 dairy herds in the PNW The majority of strains of S. aureus that cause bovine mastitis were unique to one herd. Herds that purchased replacement heifers had a higher prevalence of S. aureus mastitis than herds that purchased lactating cattle for herd expansion. Herds that purchased replacement heifers had more strains of S. aureus than closed herds. Herds that purchased replacement heifers acquired more new strains of S. aureus than closed herds. 17
S. aureus Genotype B Term used by Swiss research group -> PCR amplification of 16S-23S rrna intergenic spacer region (RS)-PCR Identified 17 genotypes among 101 epidemiologically independent S. aureus isolates. TWO genotypes (B and C) most common 80.2% (81/101) (Fournier et al, 2008; Graber et al, 2009)
S. aureus Genotype B Genotype B - associated with sed (84%), sej (80%), sea (77%), luke (100%); highly contagious and considered pathogenic. (Fournier et al, 2008; Graber et al, 2009)
U.S. Isolates & Genotype B? 65 S. aureus isolates from 8 dairy farms in the Pacific Northwest 35 different PFGE strain-types NAGase and SCC data associated with each isolate RS-PCR (Jensen et al., 1993) Standard PCR was used to confirm the presence or absence of the leukotoxin E (luke) gene and sea, sed, seg, sei, and sej. 20
U.S. Isolates Genotype (n=65) sea sed sei sej seg luke Y (n=1) 1 (100%) 0 0 0 0 1 (100%) E (n=3) 0 0 3 (100%) 0 3 (100%) 3 (100%) H (n=1) 0 0 1 (100%) 0 0 1 (100%) I (n=43) 3 (6.9%) 0 2 (4.6%) 0 0 42 (98%) X (n=1) 0 0 0 0 0 1 (100%) Non-typable (n=16) 1 (6.3%) 0 2 (13%) 0 0 9 (56%) Total (n=65) 5 (7.7%) 0 8 (12.3%) 0 3 (4.6%) 57 (87.7%) CONCLUSIONS 35 PFGE strains versus 6 RS-PCR genotypes No Genotype B found No relationship between genotype, SCC, and NAGase activity (P 0.64) Discriminatory power of RS-PCR = 0.46 relative to PFGE (1.0). 21
Detection & Diagnosis SCC/CMT Sensitivity ranges from 0.86-0.96 Definitive diagnosis based on detection of organism Bacterial culture PCR detection Source of sample; aseptic collection Strain-typing 22
Treatment Probability of cure depends on cow, pathogen, and treatment factors (Barkema et al., 2006) Cure rates: 3-74% Major factors impacting cure rate include: Cow age Increasing SCC Chronicity Increasing bacteria count Increasing numbers of mammary quarters infected Duration of therapy 23
S. Nickerson 24
Treatment Treatment of young animals with penicillin-sensitive S. aureus infections is often justified based on bacteriological cure and economic outcome, whereas treatment of older animals, chronic infections, or penicillin-resistant isolates should be discouraged. (Barkema et al., 2006) Systematic Review of Literature (Roy & Keefe, 2012) Extended IMM therapy for 5-8 days was the best option 25
Caution! Extended therapy can be associated with clinical mastitis with secondary organisms such as yeasts and coliforms (Roy & Keefe, 2012; Middleton & Luby, 2008) May constitute Extra-label Drug Use! Overall, long term cure rates even with 8 days of therapy can be quite poor (Middleton et al., 2007) 26
Pre-partum Treatment of Heifers Caution! Extra-label drug use. Cure rates can be quite high, but overall impact on 1 st lactation performance over no treatment varies from herd-to-herd with no benefit in some herds. 27
Prevention & Control Properly functioning milking equipment Gloves* Decrease potential for transmission Milking time hygiene Milk order Post-milking teat dip Dry cow therapy Cull chronics Avoid purchase of older cattle Pre-purchase screening (Biosecurity) 28
Prevention & Control Outbreaks may occur in herds with excellent milking time hygiene (Smith et al., 1998). May require more aggressive control program (Middleton et al., 2001; Zeconni et al., 2003) Segregation & milk last Dry-off infected quarters Accelerated culling In contrast, some herds have sporadic strains that are not highly transmissible (non-host-adapted S. aureus) and may not require intervention. 29
Vaccination A S. aureus mastitis vaccine should reliably prevent intramammary infection because the reservoir of infection is the cow s udder and the majority of transmission occurs from cow-to-cow at the time of milking. 30
Staphylococcus aureus Vaccines No vaccines studied to date consistently prevent new S. aureus IMI. Two commercial vaccines (Lysigin, BIVI; Startvac, HIPRA) 31
Lysigin Lysed polyvalent S. aureus bacterin 5 strains; 3 capsular serotypes (Ma et al., 2003) Serotype 5 1 strain Serotype 8 2 strains Serotype 336 2 strains Capsular serotypes 5, 8, and 336 are the most common mastitis causing S. aureus serotypes (Guidry et al., 1997 & 1999) 32
Lysigin in Heifers MU Heifer Challenge Trial No difference in S. aureus IMI clearance (P 0.214) No difference in milk SCC (P 0.148) No difference in milk yield (P = 0.617) Cattle vaccinated with commercial Lysigin had a lower mean duration of clinical mastitis and lower cumulative mastitis score than control (P = 0.045 & 0.046, respectively) No significant difference in milk opsonizing Ab (P > 0.05) 33
Field Trial Data Lactating dairy cattle (44 vaccinates and 46 controls). New S. aureus IMI 7/44 vaccinates and 4/46 controls (P = 0.511) New CNS IMI 18 of 157 at risk quarters in vaccinates Incidence = 0.82 new IMI/quarter month 20 of 159 at risk quarters in controls Incidence = 0.81 new IMI/quarter month Median time to new IMI = 56 days (P = 0.944) No significant difference in milk Ab (P > 0.30) 34
Nickerson et al., 1999 Early vaccination of heifers @ 6-months with 6-monthly follow-up until calving. Staphylococcus aureus IMI 44.8% reduction in new IMI during pregnancy 43.1% reduction in IMIs becoming chronic 44.7% reduction in new IMI at freshening Other Staphylococcal spp. 0.0% reduction in new IMI during pregnancy 34.7% reduction in IMI becoming chronic 30.8% reduction in new IMI at freshening 35
Vaccination as an Adjunct to Treatment Adjunct to extended pirlimycin IMM therapy -14d, -7d, 2d relative to treatment Luby et al. 2005. Vet Record. 157, 89-90. Middleton et al. 2007. Proc Natl Mast Counc. 45, 232-233. No significant difference between vaccination and treatment versus treatment alone. 36
Startvac Multivalent mastitis vaccine Inactivated E. coli (J5 strain) Inactivated S. aureus (CP8) SP140 strain expressing slime associated antigenic complex (SAAC) Label reduce incidence of subclinical mastitis and decrease the clinical severity of mastitis caused by S. aureus, coliforms, and CNS. 37
Schukken et al., 2014 45% decrease in basic reproduction ratio for S. aureus 35% decrease in basic reproduction ratio for CNS Efficacy age dependent (> reduction in Parity 1 vs. 3 or >) Results varied between herds 38
Schukken et al., 2014 39
Startvac Stimulates humoral immune response. Ameliorates inflammation in the udder following challenge with inactivated S. aureus. Does not completely prevent infection, but recent data suggests it may decrease S. aureus transmission rates within herd by reducing incidence and duration of IMI. Piepers et al., 2012; Schukken et al., 2014 40
Take Home Messages Have we learned anything about S. aureus mastitis in the last 50 years? YES! Has what we have learned changed the basic premise that milking time hygiene is the main critical control point? NO! Ultimately, decisions on how to manage S. aureus mastitis in a given herd will depend on the contagiousness, persistence, and inflammatory nature of the infecting strains. 41
Take Home Messages Use of historical data on new IMI rates, SCC, and response to therapy will be valuable tools in making management decisions. Culture and strain-typing may be necessary in some herds. If most infections are caused by a single strain that is refractory to treatment, then culling may be the only option. If strains are diverse and sporadic, drastic measures may not be needed. Vaccination against S. aureus will not completely prevent IMI, but some strategies may be beneficial in reducing transmission when used in conjunction with contagious mastitis pathogen control procedures outlined in the NMC 10- point plan. 42
Questions? 43