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Diseases of Dairy Cattle(based on Dr. Swists notes)

PATB 4110 - Diseases of Food Animals and Horses

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Diseases of specific concern in dairy cattle

The Big Three: mastitis; lameness; fertility And three important infections: Salmonellosis Johnes Tuberculosis

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Retained placenta Brisket [personal interest] Milk fever ( calcium) Grass tetany ( magnesium) Ketosis

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General Concepts

Nutritional & management problems vs. infectious disease (contagious vs. non-contagious)

Clinical vs. subclinical disease Cost of diseases

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Veterinary & drug expenses Loss of production (unrealized income) Early culling/death

One animal vs. the herd Prevalence

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Disease can often occur in a predictable sequence or cascade

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Overconditioning

Optimal BCS for a cow at calving is 3.5-3.75/5 Overconditioning increases susceptibility to

all metabolic disorders Alters hormonal balance

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Alters hormonal balance Greater decreases in feed intake prepartum Faster rate of body weight loss

Rapid fat mobilization to meet energy needs Decreased milk yields Longer period of negative energy balance

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Body condition score in dairy cattle6

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Displaced abomasum7

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Displaced abomasum

Repositioned abomasum from right ventral side of abdominal cavity Twisting from repositioning slows or stops flow of digesta Gas buildup leads to bloat appearance

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Gas buildup leads to bloat appearance Pinging detected with stethoscope by thumping the cow near last

rib and listening on left flank

85-90% left-sided 75% occur within 1st 14 days post calving Rare in heifers

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B

D

B

D

A

Normal Abomasum Position Displaced Abomasum

A

CC

Abomasum = A

Rumen = B

C = Omasum

D = Liver

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Symptoms of DA

Dramatically decreased feed intake Drastic drop in milk production Pain (back arched)

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(b )

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Causes and Risk Factors

Etiology is multifactorial, although abomasal hypomotility & gas production major contributors to displacement or volvulus

Abomasal hypomotility: Hypocalcemia

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Hypocalcemia Mastitis/metritis-endotoxemia & decreased rumen fill

Hypomotiliy also associated with: Ingestion high-concentrate, low-roughage diets ( VFA) Diets also result in gas production

Changes in position of organs and fetus prior to birth Genetic predisposition; deep-bodied cows Ketosis

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Displaced Abomasum

Non-surgical Removal of gas from abomasum Rolling cow over, taking on rough trailer ride Tethering of right hind leg

87% recovery rate

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87% recovery rate

Surgical Move abomasum into place and attach it surgically to

body wall Open incision or blind tack 92% recovery rate

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Displaced Abomasum

Prevention Ensure rapid increase in rumen volume following calving Feed a total mixed ration Avoid rapid dietary changes

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Maintain adequate roughage in diet Cows should be in proper body condition at parturition Prevent hypocalcemia & other metabolic disease

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Bovine Tuberculosis14

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Bovine Tuberculosis (TB)

Historic Disease: Bovine TB caused more losses among US farm animals in early

1900s than all other infectious diseases combined

Meat inspection: looking for TB esp. 1917, USDA/APHIS began national eradication program; 2010 TB

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1917, USDA/APHIS began national eradication program; 2010 TB nearly eliminated

Highly contagious to all warm-blooded animals & humans Reportable disease in WY & US Wildlife can spread TB to commercial cattle (and cattle to wildlife)

Mycobacteria M. bovis, M. avium & M. tuberculosis

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Transmission & clinical signs

Transmission: Aerosol>ingestion(milk)>intrauterine/sexual

Clinical signs: Depends on organ/location Usually chronic disease but can have acute episodes

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y p

General: emaciation, lethargy, weakness, anorexia, fever Granulomatous inflammation/disease

i.e., Lung, liver, lymph nodes

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Emaciated Cow Lung & liver granulomas

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Lung & lymph node granulomas

Acid fast stain of Mycobacterium

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Diagnosis TB

Most important diagnostic test: Intradermal tuberculin test

Diagnosis on clinical signs alone difficult even w/advanced cases

Other :

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Other : Radiographs, microscopic exam sputum/fluids Meat inspection Necropsy

Definitive diagnosis: Isolation & ID of bacteria ~4-8wks PCR ~2-4 days

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TB Tuberculin skin test

Animal exposed to tuberculin Mycobacterial antigen- M. bovis or M. tuberculosis

Checked for reaction after 72 hrs Delayed type hypersensitivity

If h t t ti ti l t l l i fl ti / ki

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If host a reactor, antigen stimulates local inflammation c/o skin swelling

Test sites vary in sensitivity & between countries ~neck, anal or caudal fold of tail

Disadvantage: Poor specificity-cross reacts with other Mycobacteria spp. & Nocardia spp.

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Control

#1:Test & slaughterOnly way to assure eradicationSlaughter of reactors detected by tuberculin testIn affected herd, test every 3 mo.

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UM&R

#2: Test & segregate #3: Chemotherapy

Elephants, nonhuman primates, humans

Routine hygiene Clean & disinfect contaminated food, water troughs, etc.

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Control

Nationwide slaughter plant surveillance activities If positive found, trace back to herd of origin

T t & l ht h d if

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Test & slaughter herd if necessary Depopulation voluntary, so may quarantine

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Wyoming Livestock Board: Animal Import Rules

Import permit required on all bovines entering WY Certificate of Veterinary Health Inspection required Bovine originating from a state not accredited TB free must

t USDA/APHIS i t f TB

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meet USDA/APHIS requirements for TB

Cattle must be tested prior to movement Based on status of state/zone and class of cattle

(breeding, sexually intact vs. spayed heifers and steers for feeding)

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Mastitis

What is it? Inflammation of the mammary gland

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Healthy Udder & Mammary gland tissue 9/8/2010

Healthy mammary gland tissue

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Causes of Mastitis

Infectious mastitis Invasion of bacteria into gland Clinical or sub-clinical

Many more subclinical cases than clinical

Non infectious mastitis

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Non-infectious mastitis Due to injury, chilling, bruising, improper milking

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Mastitis Quick Facts

All dairy herds have cows w/subclinical mastitis Varies from 15-75% Of cows affected, 5-40% are infected in more than one quarter

On average, 2 infections per lactation

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Mastitis29

Above totals are from 1996. USDA/APHIS Dairy report: From 1996-2007 % of cows w/clinical mastitis increased 13.4 to 16.5%. The

total economic loss is closer to $250/cow. 9/8/2010

Mastitis

Clinical mastitis Visible inflammation in udder (swelling, heat, pain, redness)

Systemic-fever, anorexia & shock Abnormal milk (e.g., color, fibrin clots)

Subclinical mastitis

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Subclinical mastitis Infection and inflammation without clinical mastitis or

systemic involvement (asymptomatic)

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For each clinical mastitis case (Orange), 15-40 subclinical cases (Green)

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Mastitis pathogens

Contagious

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Co tag ous

Environmental

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Contagious mastitis

Pathogens colonize mammary gland Spread by milking machines, milkers & cow to cow Staphylococcus aureus

l i

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Streptococcus agalactiae Corynebacterium bovis Other Streptococcus spp. & Staphylococcus spp. Mycoplasma spp. can spread from cow to cow through

aerosol transmission

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Contagious mastitis

Staphylococcus aureus Worst of the contagious agents Penetrates deep into glandular epithelium Not very responsive to antibiotics resistance common Immune response of cow not as successful in eliminating

infections as with other pathogens

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Once established in herd, difficult/impossible to eradicate Dry treat or cull Survives in multiple locations in cow Transmitted esp. by hands

Streptococcus agalactiae Obligate infection of mammary gland Readily eradicated with antibiotics Multiply in milk and on mammary epithelial surfaces Will not survive in the environment

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Mycoplasma

Primarily respiratory pathogen Can infect many tissues

Spreads through multiple routes

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Contagious and environmental

High shedding rate Severe purulent mastitis in multiple quarters No treatment - identify and cull

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Environmental mastitis

Pathogens do not normally infect mammary gland Infection when cows environment, milking machine

or teats/udder are contaminated access through teat canal

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Streptococcus uberis & other non-agalactiae Streptococcusspp.

Escherichia coli and Klebsiella sp. (coliforms) Arcanobacterium pyogenes

Important to maintain good sanitary conditions

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Environmental mastitis

Infect cows between milkings Streptococcus dysgalactiae and Streptococcus

uberis Symptoms confined to mammary gland

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Escherichia coli Easily out-competed (opportunistic) Easily eradicated (antibiotics, immune system) Toxins released when killedSystemic effects (fever, depression, death)

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Pathways for Infection

Most common route of entry is streak canal Smaller diameter streak canals more resistant to mastitis If keratin plug compromised, animals more susceptible to

mastitis

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In udder...

Bacteria proliferate, destroy secretory cells Some release toxins when killed Destroy more secretory cells

Ab b d i bl d

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Absorbed into bloodstream systemic effects (fever, low appetite)

Milk ducts blocked by clotted milk Blood vessels dilate, slowing blood flow Interferes with treatment access

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Acute mastitis:

Udder hot, hard, tender Increased temperature, refusal to eat, dull eyes,

rough coat

Increased blood proteins and leukocytes in

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Increased blood proteins and leukocytes in mammary tissue and milk

Blood vessels greatly dilated Milk ducts compressed

Treatments more likely to be unsuccessful under these conditions

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Chronic Mastitis

If treatment unsuccessful Scar tissue Ducts permanently blocked

L f f ti i l d b t

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Loss of function in glands may be permanent

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Mastitis signs and symptoms

High somatic cell count (SCC) indicates mastitis Composed of neutrophils from the blood and epithelial

secretory cells Neutrophils in milk = response to infection Epithelial cells in milk

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Epithelial cells in milk Each doubling of SCC >50,000 cells.ml = loss of 0.5 kg/milk/day

In chronic mastitis, only symptom is milk thick or lumpy

Terms you will hear: Summer mastitis = A. pyogenes = loss of quarter Gangranous mastitis = various causes; life-threatening

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Milk quality changes

Altered composition Decreased fat, protein, lactose Increased chlorides Lower total solids

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Lower total solids As low as 1/3 normal milk

Poor flavor (salty) Clumping of somatic cells Clumpy, stringy milk Only 2-3% of all cases show clinical symptoms

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Risk factors

Majority of new infections occur during: First 3 weeks of dry period

Milk left in udder First month after parturition

Immune system compromised Frequency of milking affects risk of infection

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Frequency of milking affects risk of infection Pathogen load decreased by evacuating milk more frequently

Position of the gland More exposed to environment, greater the risk

Chilling on cold ground Improper ventilation and dampness Injury

Heritability (conformation of udder/teat)

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Prevention and control

Clean and dry environment Clean and dry teats at milking Good hygiene, esp. for environmental causes Teat dips (pre- and post-milking)

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Well maintained equipment Segregate clinical cases Early identification Prompt treatment Milking machine maintenance Dry cow treatment

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Uncomfortable free stalls increase the incidence of mastitis by increasing exposure to environmental pathogens

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Latex Gloves50

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Backflush systems reduce spread of contagious pathogens, such as S. aureus, by sanitizing milkers between groups of cows

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Teat dips only effective if adequate coverage of all teats9/8/2010

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Barrier teat dips useful to prevent mastitis in dry & transition cows9/8/2010

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Barrier dips block bacterial access to the animal and can be used to protect cut areas where the skin barrier compromised.

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Treatment

Antibiotics During lactation Dry period

Frequent milkingR d bili lif

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Reduce ability to proliferate Oxytocin Reduce volume of media Reduce pathogen population

Fluid therapy for endotoxemia

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Treatment

Treatments used on dry cows most effective method of treating Staphylococcus aureus infections Long-lasting antibiotic preparations Should not be used if cows will not have full dry period

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Should not be used if cows will not have full dry period All intramammary infusions should be conducted

aseptically Clean teat ends with alcohol Insert infusion tube only as far as necessary

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Cannulas on commercial mastitis treatments should only be inserted one-quarter inch into the teat end to minimize keratin removal

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Treatment

Many reasons to avoid antibiotic contamination of milk supply Illegal - contamination results in financial penalties Development of antibiotic resistance

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Development of antibiotic resistance

Keep treated milk separate Use separate equipment

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