Pathogens
• Ways livestock agriculture may increase pathogens
in the environment
– Indirect effects on water
– Direct contamination in water
• Drinking
• Irrigation
– Antibiotic resistance in microorganisms
– Direct contamination in air
• Indirect effects on pathogens in water
– Effect
Excess N
or P
Blooms of toxic algae
Pfiesteria piscidida
(Red tides in marine
environments)
Cyanobacteria
(called blue-green algae
in fresh water)
Toxins
Contact causes
confusion,
memory loss and
gastrointestinal
problems
Toxins
Can kill livestock
– Control
• Reduction of N and P excretion and losses during storage and
application
• Direct pathogen contamination of water
– Major microorganisms of concern
• Protozoa
• Bacteria
• Viruses
Cryptosporidium parvum
Giardia
E. Coli O157:H7
Bovine rotavirus
Bovine coronavirus
Effects (Particularly severe
in very young, elderly, or
individuals with
compromised immunity)
Severe diarrhea, vomiting
fatigue, dehydration
Bloody diarrhea,
dehydration, kidney
failure
Diarrhea
– Number of cases
Cryptosporidium parvum
Giardia
E. Coli O157:H7
US Outbreaks (1989-96)
Drinking water
Recreational water
Surface Ground Natural Pool
4
4
2
11
12
6
4
5
0
3
7
1
– Reasons for problems these organisms
• The organisms or their reproductive forms are shed by
infected animals in large numbers
• The organisms survive and remain infectious in the
environment for long periods
– Some are resistant to water treatment
• E. Coli O157:H7 can multiply outside the host if adequate
nutrition
• Low dose needed for infection
• Wide range of animal hosts
– Other potentially harmful bacteria in the
environment
•
•
•
•
Campylobacter
Listeria monocytogenes
Salmonella
Mycobacterium paratuberculosis
– Causes Johne’s Disease
– Association with Crohn’s disease in humans
– Risk is largely
unknown
5000
Downstream
4500
Upstream
Fecal Coliform, CFU / 100 ml
4000
3500
3000
2500
2000
1500
1000
500
0
29
v
No
ov
ct
O
N
8-
25
ct
p
Se
p
Se
g
Au
g
Au
O
9-
27
13
30
15
ug
l
Ju
A
8-
31
• Most studies on water
quality have
demonstrated that
poor manure
management
increases fecal
coliforms in water
supplies
• Relationship between
fecal coliforms and
pathogens has not
been established
• Difficult to separate
contamination from
humans, domestic
animals and wild
animals
• Pathogenic organisms
– Cryptosporidium parvum
• Life cycle (1 – 8 days)
Oocysts consumed by host animal
(Contain 4 sporozoites)
Sporozoites released in intestine
Sporozoites invade intestinal cells
and reproduce in cells
New sporozoites invade
new cells
Oocysts released
in feces
Damage intestinal cells
Severe diarrhea
• Oocysts in 39 to 87% of US surface waters
• Hosts
– Species
» Humans
» Domestic livestock (Cattle, sheep, goats, swine,
horses)
» Companion animals (Dogs, cats)
» Wildlife (Mice, Raccoons)
– Age
» Calves
50% of calves shed oocysts between 1-3 weeks
Few shed in cattle > 6 months
» Swine
Shed oocysts during nursing and weanling stages
» Foals
Shed oocysts up to 19 weeks
» Sheep
Adult ewes will shed oocysts around lambing
• Viability characteristics
– Resistant to most public water treatments
– Very susceptible to drying
» 2 hours of dryness is lethal
– Very susceptible to high temperatures
» >100oF
– Susceptible to freezing temperatures
» Freezing for 10 days reduced viability by 90%
– Susceptible to pH>9.0
» Public water treatment plants often treat water to pH 12.0
– Oocysts remain in upper soil unless transported to ground
water with macropore flow
– Giardia
• Life cycle (7-9 days)
Cysts ingested
(Contain trophozoites)
Trophozoites attach to
upper small intestine
Severe
diarrhea
Produce cysts
Cysts released
Cysts release more
in feces
trophozoites
• Cysts are present in most surface waters
• Hosts
– Species
» All mammals, some birds, reptiles, and amphibians
– Age
» Occurs at all ages, but most common in animals that are
less than 6 months
• Viability characteristics
– Similar to Cryptosporidium
• No evidence of human infection from domestic livestock
– Escherichia Coli O157:H7
• A potentially deadly bacteria
– Causes bloody disease, dehydration and kidney failure
– Particularly hazardous to young, elderly, and compromised
immune systems
– Infection can occur with as few as 10 cells
• Life cycle
– E. Coli O157 is consumed from water troughs or moist rations
» Can survive in water trough for 4 months
– E. Coli only present in cattle for 1 to 2 months
» More frequent in cattle fed high grain diets
Feeding forage at the end of finishing will decrease
numbers
Role of distillers grains???
» More common in summer than winter
» More frequent in cattle that are 3 – 18 months old than
mature cows
» More frequent in large herds
– Excreted in feces as viable bacteria
– Capable of multiplying in the environment
» Dependent on nutrients
» Usually decrease over time
• Viability
– E. Coli O157:H7 are killed by chlorine, high
temperature, drying, aerobic storage
• At this time, few cases of direct human
infection through water
– Contamination of spinach believed to occur from
irrigation water with a feedlot ½ mile away
» E. Coli may be transported by flow, adhesion of
soil particles or motility.
• Factors affecting extent of pathogen problem
– Size of loading dose
• Percentage of herd infected
• Frequency on manure addition to storage
• Amount of dilution
– Length of storage
– Manure treatment
• Anerobic > Aerobic > Compost
– Storage characteristics
•
•
•
•
•
•
•
Aerobic/anerobic
Drying
Temperature
Freeze/thaw
pH
Nutrients
Inhibitors
– Form of organisms excreted
• Cysts or oocysts > vegetative forms
– Routes of pathogen contamination
• Run-off from bare lots
• Direct deposit in pastures or lots
• Run-off from manure application
– Vegetation on land application
• Tall forage reduces run-off
– Prevents microorganisms from reaching water sources
• Tall forage provides shade and moisture
– Increases survivability
– Soil of land application area
• Organic or clay soils trap protozoa and bacteria
• E. Coli can move rapidly through saturated soils or soils with
macropores
• Control of pathogen transport from livestock units
– Prevent import of pathogen onto farm
• Feed feedstuffs not contaminated with feces from rodents or
other livestock
– Prevent infestation of rodents or other wild or domestic
animals in feed storage areas
– Purchase feeds from sources that prevent fecal
contamination of feedstuffs
• Provide water sources with low risk of pathogen
contamination
– Keep livestock out of streams and ponds
» Provide alternate water sources
– Divert precipitation run-off from livestock facilities
• Purchase livestock from sources with good health
management
– Avoid purchases from sales barns
– Separate and quarantine new animals
• Avoid transport of manure onto farm
– Have visitors wear plastic boots
– Thoroughly clean tires on vehicles
– Prevent amplification and proliferation of organisms on farm
• Frequent cleaning and drying of housing units
– Particularly maternity areas
• Use separate implements for feeding and cleaning
• Frequent cleaning of equipment
– Tires and blades
• Provide feed and water free of fecal contamination from
livestock, pets, rodents, wildlife, and humans
• No feeding of wasted adult feed to young livestock
• Segregate calves by age
– Prevent contact of calves < 3 months with older cattle
• Prevent run-off from entering or leaving areas housing young
animals
– Limiting pathogen proliferation during manure storage
• Store manure from animals less than 6 months separate from
mature animals and spread on non-hydrologically sensitive
areas
– If calf manure can’t be stored in area that restricts leaching
or run-off, mix it with manure from mature cattle and apply
by Best Management Practices (Dilutes organisms)
• Composting at 140oF will kill most pathogenic organisms
and cysts
– Prevention of pathogen contamination by manure
application
• Application methods
– Incorporation into the soil
» Particularly effective during wet weather
» Reduces risk of contamination of water sources by:
Adsorption of organisms to soil particles
Filtration of organisms
Attack by predator organisms
Freeze-thaw activity
– Surface application
» Effective in dry weather
» Reduces risk by:
Drying
UV light
• Hydrologic considerations
– Avoid manure application in major water flow paths
– Should consider:
» Soil permeability
» Slope steepness
» Flood plains
» Flow paths
• Grassland manure application considerations
– Manure should be stored for at least 60 days
– Manure should be applied at least 30 days before grazing
– Grass should be short when manure is applied
– Pastures fertilized with manure should only be grazed by
mature animals
– Preventing export of pathogens from farm
• Control run-off from livestock facilities
– Particularly facilities housing young animals
– Place cow winter feeding areas away from streams
• Utilize buffer strips
– Grass strips lining sides of streams or ponds
– Width
» > 4.5 m from field with manure application
» > 10 – 20 m from animal feeding operations
– Effective as part of a group of Best Management Practices
» Should not be relied on as only practice
• Proper grazing management
– Use of rotational grazing
» More uniform distribution of manure
– Avoid over-grazing
– Limit or prevent access of water bodies to animals
• Release of antibiotic resistant
microorganisms into the environment
– Numerous antibiotics fed at subtherapeutic levels
to promote growth and feed efficiency
• Chlortetracycline, Oxytetracycline, Penicillin, Bacitracin,
Tylosin
– Actions
• Prevent subclinical disease
• Increases nutrient absorption
• Improves metabolic processes
– Increases rate of protein synthesis
– Problem
• Selection of organisms that are resistant to antibiotics
– Concern for penicillin, tetracyclines, and
erythromycin
• Organisms released from non-sealed lagoons and from
surface-applied manure
– Recommend
• Proper use of antibiotics
– Don’t use antibiotics as a substitute for good
management
– Rotate antibiotics used on operation
• Proper manure storage
– No run-off or leakage
• Proper manure application
– Minimize run-off
• Direct contamination of the air
– Endotoxin
• Lipopolysaccharide component of the cell wall
of gram-negative bacteria
• Problem in confinements, not in outside
environment
• Health effects on works in confinement
buildings
–
–
–
–
–
Cough
Chest tightness
Headache
Fever
Flu-like symptoms
• Control dust control measures