Infectious Disease

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Infectious Disease
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Johnes Disease (Paratuberculosis)

• Causative agent Mycobacterium paratuberculosis
• Extremely slow onset, chronic, progressive,
  incurable, fatal
• minimum 18 months to clinical status
• incubation period up to 10 years
• Prevalent in 20 of US herds
• 5-20 of ALL dairy cattle infected
• 25-30 of all herds
• increasing in both dairy and beef
• sheep, goats and deer also susceptible

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International Prevalence

• Denmark
• almost half of all herds test positive
• Holland
• 50 80 of herds infected?
• New Zealand
• 16 50 of herds infected

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History
Johnes disease is not at all widespread. It
does occur, however, and as the years go by it
will become more and more common and will places
a great tax on the cattle industry Beach and
Hastings 1922
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Johnes Disease (Paratuberculosis)

• Following calfhood exposure there is no evidence
  of infection for six months to several years
• Rate of progression dependent on age, genetic
  background, nutritional status, management, etc

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Johnes symptoms

• Clinical status after high stress period
• Progressive and fatal
• Non-treatable
• Primarily affects intestine and associated lymph
  tissues
• Causes proliferation of intestinal tissue
• Malabsorption diarrhea
• Animal loses condition
• Displays diarrhea and constipation
• Decreased milk, same feed intake (until late
  stages)

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Fig 35-1. Cows with Johne's disease typically
lose tremendous amounts of body weight, although
feed consumption may be normal (Courtesy of Mark
Kirkpatrick)
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Johnes Disease (Paratuberculosis)

• Apparently healthy animals can spread the disease
• Test at regular intervals of 3-6 months
• Diagnostic testing is often inaccurate
• Fecal culture is most accurate method in live
  animals
• False negatives are still a problem
• No treatment
• Prevention through keeping infected animals
  isolated

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Johnes Transmission

• Fecal-oral
• Organism remains viable in feces for 6-11 months
• Transplacental transfer
• Organism present in milk, colostrum
• Severity of infection depends on level of
  infective dose
• Age of exposure is critical
• lt5 of infected animals develop clinical symptoms

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Age Effects

• Newborn calf most susceptible
• susceptibility decreases with age
• not clinical - no shedding until gt 9 mos.
• Cows least susceptible
• infection unlikely after 1 year of age
• shedding rate highest in mature, clinically
  infected cows

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Costs

• Lost milk costs
• Lost cow value and slaughter value
• Lost marketing ability of herd
• Longer calving intervals
• Increased mastitis
• Increased vet costs
• 250/cow (all cows, not just infected)
• Infected 100 cow herd with average infection rate
  loses 25,000/year

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Antibody Tests
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Fig 35-2. Enzyme-linked immunosorbent assays
(ELISA's) are a useful diagnostic tool for
estimating the prevalence of Johne's disease in
infected herds (Courtesy of Mark Kirkpatrick)
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Testing

• ELISAs and other antibody tests have high
  incidence of false positives
• If ELISA or antibody test is positive, fecal
  culture should be used to confirm status
• Fecal cultures take 16 weeks, very expensive
• Negative result does not necessarily indicate
  uninfected cow, just non-shedding cow
• Positive result is fairly accurate

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Fig 35-3. To confirm infection with Johne's
disease, tissues can be stained for the
immunohistological detection of M.
paratuberculosis (Courtesy of Mark Kirkpatrick)
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Johnes Disease (Paratuberculosis)

• Control measures for infected herd
• Reduce contamination by good sanitation
• Do not spread manure on pasture land
• Raise young stock in uncontaminated environment,
  separate from mature animals

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Control Program

• Prevent transmission
• sanitary maternity barn
• clean perineal area and udder
• Remove calf from dam prior to nursing, wash udder
  well prior to milking
• feed colostrum from test-negative cows
• raise shedders separate from susceptibles
• spread manure on crop ground, not pasture

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Control Program

• Reduce incidence in herd
• test mature animals every 6 months
• remove test-positive animals immediately
• cull any apparent clinicals
• regardless of test results
• purchase only from tested clean herds
• vaccinate infected herds
• not cost-effective in clean herds
• does not prevent disease, only reduces severity
• interferes with antibody tests

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Is Johnes a Food Safety Issue?
Crohns disease is a bowel disease in
humans Overall incidence 5.6 cases per
100,000 Severe and very unpleasant
condition Cause unknown, maybe infectious agent
like Mycoplasma Johnes organism found in Crohns
patients
No firm link established, the evidence is still
inconclusive - but the issue is a source of
concern to the dairy industry
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Bovine Virus Diarrhea (BVD)

• Incubation period of 7-9 days
• Characterized by
• High temperature (105-107 F)
• Nasal discharge
• Rapid breathing
• Loss of appetite
• Diarrhea
• Causes abortions in pregnant cows (3-6 weeks
  after infection)
• Decrease in milk production in lactating cows

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Bovine Virus Diarrhea (BVD)

• Prevention
• Avoid contact with infected animals
• Keep away from contaminated feed and water
• Isolate all incoming animals for 30 days
• Treatment
• Electrolytes
• Antibiotics combat the secondary bacterial
  invaders

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Bovine Virus Diarrhea (BVD)

• If BVD is a constant problem, vaccinate animals
• Intramuscular administration of modified live or
  inactivated vaccines
• One vaccination should last a lifetime
• DO NOT vaccinate pregnant cows
• Causes abortions
• DO NOT vaccinate calves under 6 months of age
• Ineffective due to interference from maternal
  antibodies from colostrum
• Replacement heifers should be vaccinated at 9-12
  months of age

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BVD control

• Multiple strains exist (identify!)
• Fecal-oral
• Sanitation crucial
• Vaccines highly effective
• not 100
• BVD-PI (persistently infected) are exceptional
  situation

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BVD-PI animals

• 1 in every 200 calves is PI
• Infected in utero between 80 and 120 days
• Infection from 120-150 days
• congenital defects
• weak calf syndrome
• Infection after 150 days
• immune response
• abortion, mummification

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BVD-PI calves

• No immune response
• recognizes virus as self permanently
• Virus replication unchecked
• incredibly high shedding rates
• potential threat to entire operation
• Difficult to identify
• Ab titers ineffective method
• must directly test for presence of virus

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Fig 35-4. Obtaining an ear notch tissue sample
for immunohistochemical diagnosis of BVD
infection (Courtesy of Mark Kirkpatrick)
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Fig 35-5. Immunohistochemical techniques help
veterinarians visualize the BVD virus in ear
tissue (Courtesy of Mark Kirkpatrick)
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Salmonella

• Invasive coliform
• fecal-oral transmission
• penetrates gut lining
• systemic infection common
• Present on up to 75 of dairies
• clinical expression after stress (shipping)
• Highly rate of transmission
• herd epidemics common
• high shedding rate
• high mortality rate

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Salmonella

• Pathogen associated with stress and
  immunocompromised animals
• Calves and transition cows most susceptible
• maternity barn sanitation
• isolation of sick or recently purchased animals
• Characterized by rapid onset and severe watery
  diarrhea
• Weak and rapidly dehydrated
• Often becomes systemic infection
• Pathogen transmitted in feces
• High sanitation standards are critical
• Infected cattle should be isolated
• Animals are responsive to antibiotics

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Challenges

• Some strains infect people
• Carriers include pets and pests
• Different strains present in different herds
• S. typhimirium DT 104 is problem pathogen
• multiple antibiotic resistance (cassette
  resistance)
• resistant to ampicillin, florfenicol,
  streptomycin, sulphonamides, and tetracyclines
• use of one antibiotic selects for the rest

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Treatment

• Identify early
• Isolate infected animals
• Extreme sanitary measures
• cows AND people
• Use appropriate antibiotic treatment
• test for susceptibility
• Supplemental fluids crucial
• Use herd-specific vaccine if necessary

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Drenching Fluids
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Bovine Respiratory Disease Complex (BRDC)

• Acute respiratory disease
• Most common in calves
• Commonly associated with transportation stress
• First sign of disease is a tired appearance and
  reduced appetite
• Depression, nasal discharge, high temperature,
  cough, rapid breathing
• Loss of appetite, then loss of body weight and
  milk production

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Bovine Respiratory Disease Complex (BRDC)

• Caused from multiple infection due to interaction
  of viruses and bacteria
• Accentuated by environmental conditions and
  stress
• Three main causative viruses
• Infectious bovine rhinotracheitis
• Bovine virus diarrhea
• Parainfluenza

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Fig 35-6. Adequate ventilation is one of the most
important considerations for the prevention of
bovine respiratory disease complex in dairy
cattle (Courtesy of USDA)
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Bovine Respiratory Disease Complex (BRDC)

• Immunity against the three main viruses can be
  achieved
• Modified live or inactive vaccines, in single or
  combination forms
• Treatments, if given early in the course of
  disease, are effective
• Antibiotics and sulfa drugs

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Fig 35-7. For this ELISA test for BRSV virus, the
intensity of the blue color is proportionate to
the titer of specific antibody in the sample
(Courtesy of Mark Kirkpatrick)
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Pneumonia

• Inflammation of lungs in which the air sacs fill
  with discharge
• Often a disease secondary to other conditions
• If left untreated, 50-75 of animals die
• Characterized by elevated temperature
• Quick shallow breaths, nasal discharge, cough, no
  appetite

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Fig 35-8. Fever, dullness, inappetance, coughing,
and nasal discharge are the most common symptoms
of pneumonia in calves (Courtesy of University of
Illinois)
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Pneumonia

• Causes are numerous
• Many microorganisms and many different viruses
• Changeable weather and poorly ventilated damp
  barns are conducive to pneumonia
• Prevention
• Providing good hygienic surroundings with
  adequate ventilation
• Segregate sick animals
• Treat sick calves with broad spectrum antibiotics

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Pinkeye (Keratitis)

• Several causes - two most common types, one
  caused by virus, one by bacteria
• Characterized by liberal flow of tears and
  inability to keep eye open
• Redness and swelling of the membrane lining of
  eye
• If untreated can cause blindness

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Pinkeye (Keratitis)

• In viral pinkeye, causative organism is
  infectious bovine rhinotracheitis
• Eyeball is only slightly affected
• Mainly affects eyelids and tissues surrounding
  the eye
• Occurs most frequently in winter
• Highly contagious by direct or indirect contact
• Prevention
• Proper vaccination prior to disease onset
• Treatment is seldom of value

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Pinkeye (Keratitis)

• Bacterial pinkeye caused by Moraxella bovis
• Produces a toxin that irritates and erodes the
  coverings of the eye
• Occurs mainly in warm weather
• Transmission mainly by flies and direct contact
  between animals
• Prevention
• Controlling face flies, isolate infected animals

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Pinkeye (Keratitis)

• Bacterial pinkeye treatment
• Application of antibiotics or sulfa drugs to the
  affected eye
• Cortisone injected into eye can reduce swelling
• Eye patch
• Isolate animal

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Ringworm

• Contagious disease of the outer layers of skin
• Caused by microscopic molds or fungi
• Characteristics
• Incubation period of one week
• Round scaly patches of skin, devoid of hair
• Organisms spread between animals
• Must disinfect surfaces as well as treat animals
• Isolate infected animals

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Coccidiosis

• Parasitic disease caused by microscopic organisms
  called coccidia
• Cattle infected by 21 species of coccidia
• Only Eimeria bovis and Eimeria zuerni cause the
  most serious infections
• Infected animals pass organism through feces
• Gains entry into an animal by being swallowed
• In the hosts intestine the outer membrane of
  oocyte ruptures, releasing the sporozoites which
  destroy epithelial cells

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Coccidiosis

• Severe infection produces diarrhea and bloody
  feces
• Hemorrhage of blood vessels into intestinal lumen
• Segregate infected animals immediately
• Try to keep feed/water from being contaminated

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Foot and Mouth Disease (FMD)

• Highly contagious disease of cloven-footed
  animals
• Humans are mildly susceptible
• Characterized by appearance of watery blisters in
  mouth and on skin between claws of the hoof
• Moderate fever, excessive salivation

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Fig 35-9. Foot and mouth disease (FMD) is
characterized by blister-like vesicles on the
tongue and lips, mouth, on the teats, and between
the hooves (Courtesy of USDA)
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Fig 35-10. The blisters in the mouth and on the
tongue caused by foot and mouth disease result in
excessive slobbering (Courtesy of USDA)
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Foot and Mouth Disease (FMD)

• Infective agent is a small virus
• Six different strains
• Virus is present in blisters, blood, milk, meat,
  saliva, and urine of infected animals
• Can be spread through infected biological
  products and by cattle fever ticks

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Anaplasmosis

• Caused by parasite, Anaplasma marginale
• Invades red blood cells
• Transmitted by biting insects
• Once infected, the animal permanently retains
  parasite in blood
• No signs of ill health may be evident
• Clinical symptoms generally do not appear until
  18 months of age
• Calves usually only have mild symptoms

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Anaplasmosis

• In mature animals
• Symptoms of anemia and jaundice skin
• Rapid heart rate, labored breathing, fever, loss
  of appetite
• Recovery is usually slow, yet the animal still
  retains the parasite

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HBS - One Syndrome with Several Names

• HBS Hemorrhagic bowel syndrome
• JHS Jejunal hemorrage syndrome
• BBS Bloody bowel syndrome

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Hemorrhagic Bowel Syndrome

• Sporadic in morbidity
• A typical case incidence rate is 2-3, with some
  farms experiencing an outbreak form
• Mortality may approach 85-100 of cases due to
  peracute nature

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Clinical Signs of HBS

• Short incubation period hours rather than days
• Severe sweats
• Bruxism (teeth grinding)
• Sternal recumbancy
• Lethargy (extreme depression)
• Enopthalmia (sunken eyes)

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Clinical Signs of HBS

• Slight bloating may be evident
• Pale mucous membranes
• Fluid slosh in lower right abdomen
• Distended gut loops per rectal palpation
• SUDDEN DEATH

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Post-Mortem Findings

• Severe segmental small intestinal inflammation
• Segmental hemorrhaging and clotting forming a
  functional plug.
• Necrosis /-
• Impaction

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Diagnostics

• Appearance of characteristic lesions and clinical
  signs
• Isolation of Clostridium perfringens type A from
  the lesion site in high numbers. Overgrowth
  occurs fast.
• Fecal cultures not diagnostic

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Treatment Efforts

• Prognosis is extremely poor
• Surgical intervention
• Some areas of segmental clots may be massaged out
  to resolve the case
• Intestinal resection anastamosis is usually
  required to remove affected tissue
• Success Rate 5-10

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Are Clostridial species involved?

• C. perfringens type A has to be present in the
  diet to cause disease
• Readily fermentable carbohydrate is needed to
  support growth sporulate
• Partial slowdown or stoppage of ingesta flow
  allowing proliferation of C. perfringens.
• Generation time 8.8 min.

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Field Observations
Food Poisoning Is there a source of C.
perfringens type A (human model)?

• Model of Infection

Lamb Enterotoxemia Carbohydrate engorgement or
presence in small intestine in high amounts.
Gut Physiology? Rumen emptying rates, local
hypomotility? Serum Ca levels?
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Herd Breaks

• Fermentable Carbohydrate
• NFC levels in excess of 40?
• Which high moisture feeds are being used in the
  ration and at what levels?
• How soluble are the starches?

Wet vs. Dry Fermented Fineness of Grind
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Vaccination?
Commercial Vaccines ?Vaccination with a 7-way
Clostridial bacterin/toxoid has shown little
effect. ?C. perfringens CD toxoid may have some
effects if the infection was mixed.
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Summary
Carbohydrate availability Acidosis? Rumen
Emptying Rate?
Feed Contamination Poor fermentation Contamination
Intestinal Motility Ca Levels, DMI or Acidosis
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Reproductive Diseases and Disorders
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Brucellosis (Bangs Disease)

• Causative bacteria Brucella melitensis
• Contagious abortion disease in cattle, Brucella
  abortus
• Hidden, lesions frequently are not evident
• In other species , can cause similar problems
• National testing program
• Control and eradication has helped lower
  infection rates

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Brucellosis (Bangs Disease)

• Symptoms are indefinite
• Abortions in cattle, but not all animals infected
  will abort
• Infected animal may have a normal birth, but calf
  may be weak, milk production reduced
• Joint pain, abcesses
• Humans are susceptible to all three species of
  brucellosis
• Swine organism causes most severe disease
• Undulant fever caught by handling affected
  animals, raw meat or milk

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Brucellosis (Bangs Disease)

• Brucella organism is resistant to drying
• Killed by disinfectants and pasteurization
• Found in tissues, membranes, and fluids, of the
  aborted young
• Harbored indefinitely in the udder
• Brucellosis is contagious
• Licking infected animals
• Through contaminated feed/water

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Brucellosis (Bangs Disease)

• Control programs
• Testing
• Removal of infected animals
• Strict sanitation
• Brucellosis eradication program (1934)
• Finding infected animals and eliminating them
• Vaccinating where there is a disease problem
• Certifying brucellosis-free herds and areas
• Providing indemnity to farmers whose animals are
  condemned under the program

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Leptospirosis

• Humans can contract disease through skin
  abrasions when handling infected animals, raw
  meat or milk
• Usually a mild disease
• Fever, poor appetite, abortion, ropy milk
• Caused by several species of corkscrew shaped
  organisms

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Fig 36-1. Leptospirosis can cause abortions
during the last half of gestation (Courtesy of
USDA)
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Leptospirosis

• Preventative measures
• Test animals prior to purchase, isolate for 30
  days, then retest
• Keep premises clean
• Control rodents and other vectors (canines)
• Vaccinate susceptible animals annually if disease
  is present in the area

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Leptospirosis

• Carrier animals spread the infection by shedding
  organism in their urine
• Recovered animals remain carriers for 2-3 months

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Vibriosis

• Infectious venereal disease
• Causes infertility and abortion
• Must be diagnosed through laboratory
• Caused by Campylobacter fetus
• Prevention
• Avoid contact with diseased animals and
  contaminated feed, water, and materials
• Vaccinate annually
• Artificial insemination

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Bovine Trichomoniasis

• Protozoan venereal disease
• Causes early abortions and temporary sterility
• Caused by Trichomonias foetus
• Found in aborted fetuses, fetal membranes and
  fluids, vaginal secretions
• Infected bull is source of infection
• Disease is self limiting in cows
• Signs not shown in bulls, but cows indicate
  infection
• Prevention use clean bulls or AI

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Fig 36-2. This bull, infected with
trichomoniasis, appears normal and will breed
normally, but can infect an entire herd through
natural service (Courtesy of University of
Illinois)
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Metritis

• Inflammation of uterus caused by various bacteria
• Usually develops after giving birth
• Symptoms
• Foul smelling discharge from vulva, brown color
• High temperature, rapid breathing, loss of
  appetite, lowered milk production
• Affected animals may die in 1-2 days or acute
  infection may cause sterility

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Metritis

• Most commonly caused by Escherichia coli
• Preventative measures
• Alleviate predisposing factors
• Bruises and tears while giving birth
• Exposure to wet and cold
• Introduction of bacteria during or after birth

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Bovine Protozoal Abortion

• Not all infected cows will abort
• Calves born from infected cows will experience
  nervous system disease
• Caused by Neospora
• Transmitted through congenital infection and
  fecal-oral transmission

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Foothill Abortion

• Reported in western US and Europe
• Cows abort when 3-6 months pregnant
• Some calves are stillborn while others are weak
  at birth
• Caused by a virus
• A soft bodied tick is the vector
• Prevention
• Move cattle out of tick-infested areas during 3-6
  month gestation period
• Animals that have aborted are usually immune and
  can be returned to herd