Bovine mastitis

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Medicina pediátrica en pequeños animales

Presentation brochure

ESSENTIAL G IDES ON CATTLE FARMING

Bovine mastitis Maria E. Prado



Bovine mastitis

Author: Maria E. Prado. Format: 17 x 11 cm. Number of pages: 70. Binding: Paperback, wire-o.

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Mastitis is the inflammation of the mammary gland and udder tissue, and represents a major endemic disease of dairy cattle. Sometimes permanent damage to the udder occurs. Severe acute cases can be fatal and lactations may be compromised despite of the apparent recovery of the mammary tissues. This condition is a very complex disease affected by several factors and it is usually presented subclinically in herds. Moreover, mastitis treatment and control supposes large costs and losses to the industry. In accordance with the current situation, an updated review has been carried out using graphic resources such as photos, tables, flowcharts, etc. The author, a specialist in this field, has developed an accurate handbook analyzing the most highlighted features of this condition and pointing out the main control measures to prevent it as maximum as possible.


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Bovine mastitis

Presentation of the book Mastitis is the inflammation of the mammary gland and udder tissue, and represents a major endemic disease of dairy cattle. It occurs as an immune response to bacterial invasion of the teat canal by variety of bacterial sources present on the farm or as a consequence of chemical, mechanical, or thermal injury to the cow’s udder. There is sometimes permanent damage to the udder. Severe acute cases can be fatal and lactations may be compromised despite of the apparent recovery of the mammary tissues. This condition is a very complex disease affected by several factors and it is usually presented subclinically in herds. Mastitis treatment and control supposes large costs to the industry and there are lots of losses due to this illness (reduction in yields, milk thrown away, extra labour, veterinary care and medicines, reduced longevity). In accordance with the current situation, an updated review has been carried out using graphic resources such as photos, tables, flowcharts, etc. The author, a specialist in this field, has developed an accurate handbook analyzing the most highlighted features of this condition and pointing out the main control measures to prevent it as maximum as possible. An interesting chapter referred to case investigation has been included to illustrate this topic in a more practical way.


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Bovine mastitis

The author Maria E. Prado MV, PhD, DACVIM. Dr. Maria E. Prado obtained her veterinary medicine degree (MV) from the University of Zulia in Maracaibo, Venezuela in 1987. Following two years of bovine private practice, she came to the United States to further her education. She completed a one year internship in Food Animal Medicine and Surgery and Equine Theriogenology at Oklahoma State University (1993-1994) followed by a residency in Food Animal Medicine and Surgery (1995-1998) and board certification in the American College of Veterinary Internal Medicine (2000). Dr. Prado performed graduate studies in Veterinary Pathobiology and obtained a PhD at Oklahoma State University in 2003 and a postdoc in Molecular Virology. Since 2005, she has been employed by the University of Tennessee where she conducts research in the areas of bovine mastitis and respiratory disease as well as teaching.


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Table of contents 1. The bovine mammary gland Macroscopic anatomy Microscopic anatomy Physiology of the lactation Mammary gland growth (mammogenesis) Milk production and lactation Milk ejection reflex

Defense mechanisms Physical barriers Cellular defenses Noncellular defenses

2. Epidemiology Prevalence and incidence Distribution and frequency of isolation of pathogens from clinical mastitis Source and transmission of infection Risk factors

3. Pathogenesis Infectious aetiology

4. Clinical presentation

5. Diagnosis Subclinical mastitis SCC

Clinical mastitis Physical exam Milk culture and sensitivity

6. Treatment 7. Control and prevention 8. Case investigation Herd goals Mastitis problem investigation

9. References


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The bovine mammary gland

Bovine mastitis

Macroscopic anatomy » The bovine udder consists of four separate glands or “quarters” and each drains into a teat.

» A medial suspensory ligament separates the udder into two halves and provides its major support.

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» Fibers from lateral ligaments extend from the medial ligament to each side of the gland providing support via a “sling” of connective tissue.

» Blood, nerves and lymph vessels supply the mammary glands from the abdominal cavity through inguinal canals.

» The fore teats are morphologically longer but the rear quarters have larger capacity (ratio 40:60) and tend to have one or more supernumerary teats (~ 40 %).

THE BOVINE MAMMARY GLAND

Pelvis

Lateral suspensory ligament

Pelvis

Median suspensory ligament (separates left from right quarters)

Left

Front 5 Right

Rear

Connective tissue (attaches udder to the abdominal wall)

Figure 1. Anatomical attachments of the bovine udder.

Teat

Skin

Fine connective membranes (separate front and rear quarters)


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The bovine mammary gland

Bovine mastitis

Milk ejection reflex » Mechanical stimulation of receptors in the teat skin, either by suckling or manipulation of the gland, triggers an impulse that travels to the posterior hypothalamus which acts on the posterior pituitary to release oxytocin.

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» Milk letdown occurs about 1 minute from first stimulus. Peak oxytocin levels occur within 2 minutes and return to basal levels by 10 minutes.

» Oxytocin binds receptors on the myoepithelial cells stimulating their contraction and increasing alveolar intraluminal pressure with subsequent expulsion of milk.

THE BOVINE MAMMARY GLAND

Hypothalamus

Lobe

Contraction of myoepithelial cells

Alveoli

Oxytocin n toci Oxy

Milk

Duct

Pituitary Anterior lobe

Milk

Mammary quarter Posterior lobe

Brain

Suckling Milking machine sound or touch of gland by milker

Heart Udder

Figure 6. Milk ejection reflex (milk let-down).

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Epidemiology

Bovine mastitis

Source and transmission of infection

Healthy cow

The infected cow is the source of infection for contagious pathogens. Transmission usually occurs during milking by exposing the healthy gland to contaminated milking equipment, towels and/or milker’s hands. Environmental pathogens are ubiquitous to the cow’s environment and infections may develop anytime as the mammary gland is continuously being challenged.

Between milkings

Environment Manure Contaminated bedding Soil Water

Cow with mastitis

During milking

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Contaminated equipment

Towels

Hands

Figure 11. Transmission of mastitis in dairy cows. Adapted from Dr. Jerry Roberson.

EPIDEMIOLOGY

a

c

b

d

Figure 12. (a) Milk residue in milking liner is a good source for transmission of contagious mastitis pathogens from cow to cow; (b) unsanitary bovine udder and improper placement of teat cups (hanging low); (c) worker spraying udder with water (this practice favours the development of environmental mastitis); (d) milker’s hands and towels are good sources of contagious mastitis pathogens. Courtesy of Dr. Jerry Roberson.

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5

Diagnosis

Bovine mastitis

Table 6. Current methods for detecting subclinical mastitis in the lab, on-farm and/or on-line (where available). Somatic cells (SC)

Changes in milk composition

Method

Flow cytometer (FC)* Portable counters

California mastitis test (CMT) Electrical conductivity

Sensors

What it does

Quantify SC concentration

Relative estimate of SC concentration

Determines increases in conductivity of milk samples caused by alteration of ionic concentration (sodium, potassium, calcium, magnesium and chloride)

Monitor milk components (i.e. fat, protein, lactose, NAGase)

Relatively inexpensive

Low cost

Performed on-farm

Potential for

Advantages

Accurate, rapid,

precise Low cost

Some counters

have good correlation with FC Performed onfarm Some available for on-line detection

Practical, rapid, simple,

user-friendly Performed on-farm Minor equipment needed Low cost Available for on-line detection

Most commonly used

method for on-line detection during each milking

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on-line adaptation

w

* Gold standard.

DIAGNOSIS

Somatic cells (SC) Disadvantages

False positives

(colostrum, early or late lactation, sudden drop milk production) Must send to lab for analysis Results not available immediately

See false positives See false positives for FC

for FC On-line system uses composite milk sample High cost, need counter and cartridges (expiration date)

Changes in milk composition False positives as ionic

concentration is also affected by inflammation composite milk sample Ionic concentration may Correlation with FC is low also be affected by Subjective scoring milk sample physical system may vary characteristics (viscosity, between individuals temperature, fraction) Scores based on range of Sensitivity and specificity SC in sample and not on for this method can actual count be improved with consistency of sampling or by combining with production data On-line system uses

Accuracy might

fluctuate and thus the need for routine calibration Time required to complete assay Mostly used as a research tool

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Diagnosis a

Bovine mastitis

c

b

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Figure 22. Proper method to collect a milk sample from a cow for bacteriological culture. (a) The opening of the teat canal is cleaned with an alcohol swab; (b) strip teat 2-3 times to remove the fore milk; (c) aseptically collect milk sample into sterile tube taking care to not contaminate the lid or the edges of the tube. Courtesy of Mr. Mark Lewis.

DIAGNOSIS

a

b

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Figure 23. Bacteriological culture of milk sample. (a) Blood plate agar demonstrating Streptococcus aglactiae colonies. Courtesy of Mr. Mark Lewis. (b) Antibiogram. Courtesy of Dr. David Bemis.


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Treatment

Bovine mastitis

» Goals: » Curing the infection. » Speeding the recovery to a clinical cure. » Saving the affected quarter and the cow. » Severity of each case will dictate the order in which these goals are prioritised.

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» When possible, therapy should be based on culture results as there are no other methods that accurately predict aetiology. This would ensure appropriate therapy towards a specific pathogen(s) of those cases that need it, resulting in the overall reduction of the use of antimicrobials and decrease chances of residue violations. Cultures should be available within 24 hours to be of benefit.

TREATMENT

Table 8. Intramammary (IMM) therapy for clinical mastitis based on severity. Severity

Mild

Moderate

Severe

Frequency

60-90 %

10-30 %

10-15 %

Presentation

Abnormal milk

Abnormal milk and/or quarter + one systemic sign

Abnormal milk and/or quarter and more than one systemic sign

Treatment

Culture-based decision to treat

± Wait for culture results

Treat immediately

Not an emergency

Examine again later on.

Do not wait for culture results

IMM antibiotics*

If worse, then start treatment

Only treat culture-positive cases with approved products Most products are effective against Gram+ pathogens. Their use

enhances clinical cure and prevents spread and/or chronic infections

Use best judgment. Most severe cases are due to Gram- but Gram+ are capable as well

Regarding Gram-, ceftiofur is approved for E. coli but mild infections

will probably self-cure. Klebsiella sp. can become chronic so treat

No effective treatment for Mycoplasma, Prototheca and yeast

* Use approved products: amoxicillin, ampicillin/hetacillin, ceftiofur, cephapirin, cloxacillin, erythromycin, novobiocin, penicillin and pirlimycin.

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Control and prevention

Bovine mastitis

a

b

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CONTROL AND PREVENTION

c

d

e

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Figure 28. Udder preparation for milking process. (a) First a pre-dipping solution is applied to the each teat and allowed to remain for 30 seconds. (b) Next, the milker wearing clean gloves, cleans and dries each teat with disposable towels. (c) Then each teat is stripped to check for abnormalities in the milk. (d) If everything is normal, the milking cups are properly attached. (e) After the cow is done milking, a post-dipping teat disinfectant is evenly applied to each teat, ensuring that it covers the whole teat. Courtesy of Mr. Mark Lewis.


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Case investigation

Bovine mastitis

Clinical mastitis outbreak

SCC mature cow, early lactation = dry cow management problem

Bacterial count in bulk tank

Identify cows by SCC2 or CMT3

Bulk tank SCC Reflects subclinical mastitis Bull tank SCC values may be affected by season, region, herd size and could be normal despite mastitis levels Must use routinely for surveillance

Milk culture

Reflects equipment problems Identify by SPC1

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CASE INVESTIGATION

Identify pathogens

Identify cows by SCC or CMT

Contagious:

Environmental:

Infected cows are the main source

Inadequate milking routine Defective milking equipment

Cull or treat cows 1 2 3

SPC = Standard Plate Count. Most reliable aid to estimate prevalence, incidence and evaluate efficacy of mastitis control measures. Most obtain monthly from testing service. The only reliable, user-friendly, economical, cow-side test for detecting subclinical mastitis. Read results within 15 seconds.

Figure 30. Common case scenarios that would require an investigation at the problem farm.

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