The organism Infection process Tissue reaction SCC response Prevention Treatment

Transcription

1 Prevention and control of Staphylococcus aureus mastitis The organism Infection process Tissue reaction SCC response Prevention Treatment

2 Staphylococcus aureus: Gram-positive Staphylo = Coccus = Cluster Sphere aureus = golden

3 Staphylococcus aureus Toxins Alpha toxin: Vasoconstrictor blood flow Gangrene Leukocidin: Protease: Kills leukocytes Digests protein Casein Lipase: Digests lipids Milk quality Phospholipase: Digests cell membranes Milk yield

4 Infection Process Mammary Anatomy Mastitis

5 Gross Anatomy: Bovine (separates F & R) (separates L & R) Milk-producing tissues Rear Fore Ducts Cisterns (extra) Teat Mammary gland: Modified skin (sweat) gland derived from the embryonic ectoderm.

6 Anatomy of a mammary quarter The teat canal, ventral to the teat cistern or collecting space, drains milk from the teat and gland cisterns, milk ducts, and glandular tissue, which is made up of millions of microscopic alveoli.

7 Alveolar structure The alveolus is lined with milk-producing epithelial cells that secrete milk into a lumen. Each is surrounded by myoepithelium that contract in response to oxytocin. This squeezes milk from the alveolus into draining ducts during the milking process. Alveolar structure is very sensitive to Staph. aureus toxins

8 Udder and teat skin are colonized with Staphylococcus aureus

9 Bacteria on teat surface are in an opportunistic position to access the teat canal and enter the interior of the quarter. Millions of staph

10 Development of mastitis: Invasion Bacteria pass through teat canal Multiply in cisterns glandular tissue Toxins produce inflammation Alpha toxin Looking at individual alveoli Bacteria

11 Bacteria Bacteria multiply and release toxins, such as alpha toxin Macrophages send message to blood via cytokines (IL-1) Leads to the recruitment of somatic cells (leukocytes) Engulf bacteria Neutrophils

12 Establishment of infection If leukocytes and soluble factors in milk cannot contain bacteria, they multiply The infection is established and may become chronic, with clinical flare-ups

13 Mammary tissue response Blood stream Uninfected quarter: SCC <200,000/ml (Loss: 2.6 lb/day) Somatic cell Alveolus Somatic cell (Neutrophils, macrophages, lymphocytes) As more somatic cells move through the alveolus, more milk producing cells are lost and yield Somatic cells in milk look for mastitis-causing bacteria At a SCC of 200,000/ml,? cells/d? 1 qtr produces 5 L/day or 5000 ml 5000 x 200,000 = 1,000,000,000!!!

14 Somatic cells Somatic cell 10,000 Somatic cells vs. 1 staph bacterial cell (Random collision) If somatic cell response fails & bacteria continue to multiply toxins Clinical mastitis Bacteria multiply Milk production is reduced SCC Yield Massive influx of somatic cells in response to bacterial growth

15 Somatic cells Somatic cell Enzymes, toxic O 2 radicals Toxins (Phospholipase Bacterial toxins In addition to the mechanical damage done by leukocytes, milk production is also reduced by bacterial toxins and the toxic byproducts released by the leukocytes. Mastitis: Increase in somatic cells in response to presence of bacteria

16 Staph is spread during the milking process Preventing spread of SA+ is by postdipping Infected Uninfected Contaminated teat cup liners [Bred heifers: Spread by horn flies]

17 How does postdipping work? Staph. aureus quarter

18 S. aureus Inflations are contaminated with milk from infected quarters

19 When inflation comes off the cow, staph contaminates teat cup liner S. aureus Contaminated inflations introduce bacteria to surfaces of cows teats that are next in line to be milked C:\slides\pdpw

20 The contaminated inflation will deposit bacteria on teat surface of the next cow in line. S. aureus

21 After removal, the contaminated inflation leaves a milk film with bacteria on teat surface S. aureus

22 After the milking unit is removed, Bacteria multiply Milk film supports bacterial growth

23 Another tool to prevent new Staph infections? Post dipping Replaces milk film with the teat germicide

24 Immunization Antibody S. aureus Vaccine (antigen) Opsonization: Neutrophil Neutrophils recognize these sites, phagocytize, and kill the bacteria S. aureus Antibodies also function to neutralize S. aureus toxins, such as alpha-toxin. Vaccination: Promotes antibody production against common Staph. aureus antigens

25 Lysigin Staph. aureus Vaccine Lysigin R USDA licensed (#124) Boheringer-Ingelheim AKA Somato-staph BI Lysed culture of polyvalent somatic antigens. Contains S. aureus phages I, II, III, and IV. Prep. uses aluminum hydroxide as adjuvant. Cows: spontaneous cures, SCC, but does not prevent new IMI

26 Staph vaccine: Successful in heifers 120-cow Holstein herd 22,000 lb milk Average SCC: 200,000/ml ~20% S. aureus infection rate in heifers Prevention of mastitis via vaccination? 106 heifers 6-12 mo allotted to vaccinated and control groups (53 heifers/group)

27 Immunization Schedule Semimembranosus At 6-12 mo 14 days later At 6-mo intervals Pre-calving Monitored level of S. aureus mastitis after freshening

28 Percentage of heifers with mastitis Percentages of heifers freshening with Staph. aureus infections Minimize spread to milking herd % Reduction (P<0.001) 13.3 Vaccinated What if prevention fails? 50% reduction in SCC 8.6% increase in prod. Control

29 Antibiotic Treatment Is used when the prevention of new staph infection fails

30 Somatic Cells Antibodies Antibiotic Therapy: Aid host defenses in eliminating the invading bacteria A challenge with S. aureus mastitis Reach all sites of infection Remain at adequate levels Persist for sufficient time Kill all infecting bacteria

31 Staph. aureus Initially, bacteria damage the tissues lining cisterns, then move into the ductal system, establishing deep pockets of infection in milkproducing tissues

32 Infused antibiotic is not evenly distributed within the infected quarter, and concentrations may be too low to kill bacteria.

33 Staph. aureus Clot Deep-seated foci of infection Initially, bacteria damage the tissues lining cisterns, then move into the ductal system, establishing deep pockets of infection in milkproducing tissues Scar tissue X Swelling

34 Most infusion products: treat for up to 2 to 3 milkings. Cannot kill bacteria with 2-3 infusions of antibiotic. - Concentration insufficient - Distribution is inadequate - Short treatment duration (1-2 days)

35 Cure rates for subciinical mastitis caused by common pathogens following label instructions (2-3 milkings) % 50-60% 40-50% 20-30% 25% 0-10% Strep. ag Staph. spp Env. streps S. aureus Coliforms

36 More successful: (40-50% cure) Maximum that dairymen are willing to dump milk (1-2 additional milkings) 2X daily for 3 days, or 3X daily for 2 days (Extended therapy) Vet. supervision

37 Staph. aureus Initially, bacteria damage the tissues lining cisterns, then move into the ductal system, establishing deep pockets of infection in milkproducing tissues Clot Scar tissue X Swelling Deep-seated foci of infection Real mammary tissue

38 Uninfected RF quarter Infected RR quarter with chronic SA+ Cross-section of an udder infused with antibiotic + green food dye Allowed to disperse throughout mammary tissue overnight then cow was sacrificed, udder was frozen, then sectioned.

39 Cross section of an udder Systemic administration needed to contact bacteria via blood Staph. aureus Uninfected quarter Infected quarter Treatment labeled with green food dye

40 Parenteral Administration Systemic antibiotic IM or SC Staph Staph Contacts bacteria living in deep mammary parenchymal tissues Staph Staph Teat and gland cisterns & ducts Infused antibiotic

41 Infusions plus: intramuscular injections of 9 million U the p.m. milking 3 d 25 cows received combo therapy 51.4% cure Combination Therapy 78 qtrs. of 50 Jerseys: chronic subclinical Staph. aureus mastitis Japan2000 Infusions of 62.5 mg each milking for 3 days (Amoxymast) 25 cows received infusions alone 25% cure

42 Cured 5000Failed * 340 Preinf ect ion At treatment Infection 8 d Post tm 21 d Po *Different from quarters that cured (P<.05) SCC x 1000 Quarters destined to fail: Significantly er SCC 1900* *

43 Success of therapy depends on SCC? UGA: Ongoing 10-yr study to determine cure rates of antibiotic therapy against: Staph. aureus Env. streps CNS ~40% SCC at time of treatment for: Quarters destined to cure Quarters destined to fail. at time of treatment More cells = harder to cure?

44 Figure 1. SCC (in 1000s) of infected quarters at the time of treatment that cured or failed after therapy. Bacteria remain viable (protected) inside the PMN The more PMN, the more viable bacteria present 2994 Across all bacterial species (P<0.05) 0 Cured Failed

45 SCC x 10 3 in infected quarters that cured or failed after treatment for all therapies and regimens Cure Fail If SCC is 2,000,000 or above, do not treat If SCC is 800,000 or less, attempt therapy (P<0.065) (P<0.021) (P<0.112) CNS S. aureus Streptococci Bacteria remain viable (protected) inside the PMN, especially SA+ (intracellular) The more PMN, the more viable SA+ present to be inactivated by antibiotics

46 Optimal time to treat S. aureus mastitis: Beginning of the dry period Treatment at Cure rate greater - Higher drug conc. - Drug lasts longer - Kills more bacteria Drying off 50 to 60% cure rate

47 Heifers: Only animals that respond well to tmt! DCT: ~100% effective vs. Staph. aureus mastitis Extra-label: Requires a VCPR

48 Dry cow product use in heifers Cefa-Dri Tomorrow Dry-clox Albadry Plus Biodry Quartermaster Orbenin-DC Spectramast DC Treat prior to 30 days prepartum (avoid residues)

49 Cure rate is ~100% against Staph. aureus **Sanitize teat orifice, use partial insertion technique, dip teats

50 Why tmt. more successful in heifers vs. cows? Use DCT longer acting base Remains in quarter longer Smaller volume (50 ml vs ml) Smaller surface area Well distributed in udder Greater contact with bacteria Infection not as deep-seated Less abscess formation

51 Heifer 50 ml vs. Cow: 5000 ml 10 ml antibiotic

52 SUMMARY Staph. aureus naturally colonizes the udder/teat Infections spread among cows during milking Prevention: Postmilking teat antisepsis Prevention: Vaccination? Cows: Spont. cures, SCC Heifers: 45-60% successful as preventative and SCC Treatment cows: Success depends on SCC: <800,000? Treatment heifers: DCT d prepartum ~100% Reduces spread to lactating herd

53 This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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