Disease Triad: Environment

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33 Terms

1
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What are the three main environmental components that can contribute to disease?

  • soil

  • atmosphere

  • housing

2
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How does soil contribute to disease?

  • impacts on feed nutrient content

  • pathogen access

  • environmental toxins

3
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How does soil interact with plants?

  • nutrient source for plants

    • indirect nutrient supply for animals

  • plant composition may be influenced by:

    • climate - temperature, light, precipitation

    • soil pH

    • moisture

  • uptake of nutrients into plant may be affected by:

    • amount of nutrient in soil

    • pH of soil affects ionization and availibity

    • interactions of minerals with each other and with organic material

4
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What minerals are deficient in soil?

  • selenium

  • iodine

  • phosphorus

  • copper

  • cobalt

  • magnesium

5
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What minerals are abundant in soil and can cause toxicities?

  • selenium

  • copper

  • molybdenum

  • iron

  • sulfur

  • fluorine

  • nitrates

6
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What interactions do microbes and parasites have with soil?

  • body wastes - Leptospira, E. coli, Salmonella, Clostridium

  • dead carcasses and remains

    • Anthrax, Botulinum, Clostridium

    • spores of organisms may survive for years or decades or centuries

  • Invertebrates in soil may harbor pathogens

    • earthworm: pig lungworm

    • snails: intermediate host for range of parasite

  • parasite eggs/larvae - Hookworm, Trichostrongyles, Ascarids, Trichuris

7
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How does excess moisture in soil impact pathogens?

  • movement of pathogens and contaminants can be easier

  • favorable for organism survival

8
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How does insufficient soil moisture or drought affect pathogens?

  • increased risk for plant toxins - prussic acid, nitrates

  • higher potential for poisonous plant consumption

  • favorable for aerosol transmission of organisms

9
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How does soil impact tissue trauma?

frozen soil can cause poor footing, leading to slippage and injuries

10
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How does the atmosphere contribute to disease?

  • ambient temperature stress

  • aerosolized toxins, pollutants

  • elevation

11
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What is the biggest environmental stress factor?

temperature

12
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Thermoneutral zone

  • the environmental temperature range in which the animal does not expend energy to maintain normal body temperature

  • TMZ is dependent on …

    • species

    • body size

    • haircoat, housing, bedding, wind exposure

13
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What kinds of animals are more tolerant to cold stress but less tolerant to heat stress?

ruminants (opposite case of nonruminants)

14
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Are younger or older animals more susceptible to cold?

younger animals due to limited subcutaneous fat and brown adipose tissue; they can also shiver and use up all of their glucose

15
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Lower critical temperature

  • temperature at which an animal must increase heat production to maintain core body temperature

  • cold stress

  • feed intake increases and heat production increases → increased energy requirements for maintenance to generate heat

16
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The effects of cold are more severe when …

conditions are wet and windy

17
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Deleterious effects of cold

  • interference with water intake (frozen water supplies)

  • injuries (frozen ground)

  • frostbite

  • pulmonary hypertension

  • death by hypothermia

18
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Pulmonary hypertension

  • change in environmental temp by 40 degrees Fahrenheit or more in 24 hours can induce this

  • increases susceptibility to certain types of pulmonary diseases

19
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Frostbite

  • worse in un-adapted animals

  • extremities usually affected

    • ears

    • tail

    • scrotum

  • more severe if body part is wet

    • newborns affected

    • animals grooming each other

20
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Upper critical temperature

  • temperature at which an animal must expend energy to dissipate heat

  • heat stress

  • feed intake decreases and heat production increases → increased energy requirements for maintenance to dissipate heat

21
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Heat stress

  • a situation in which high environmental temperature and humidity result in the body’s inability to cool itself

  • mild degree of hyperthermia

    • elevation of 1-2 degrees C in some species

    • rectal tempts 103-104 degrees Fahrenheit in cattle

  • effects include

    • decreased DM intake

    • changes in metabolism

    • decreased production of milk, growth, and eggs

    • decreased reproductive efficiency → lower conception rates and higher embryo mortality

22
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Factors increasing heat load

  • increased metabolic rate

  • exercise

    • at maximal intensity, muscle energy increased 40-60 fold

  • high environmental temperature

  • high environmental humidity

  • competition for cardiac output

    • redistribute perfusion among organ systems → body is trying to get blood to the skin to dissipate heat; takes it away from other organs

    • may reduce radiation and conduction

    • may reduce GI blood flow and affect digestion and absorption

  • rectal temp 106 or higher represents hyperthermia in horses

23
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Heat stroke

  • most extreme form of heat stress

  • severe hyperthermia

    • body temperatures 107 degrees F and above

    • brain damage begins at 109-110 F

  • medical emergency

  • cool safely, and as rapid as possible

  • if cooled too rapidly, it may result in fatal lung changes

24
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Malignant Hyperthermia

  • elevated body temperature of 110 F and above

  • fatal in nearly every case

  • Porcine stress syndrome is an example

    • genetic trait

    • often associated with anesthesia

  • cases reported in other species including humans

25
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How does the atmosphere impact aerosol transmission?

  • microbial transmission

    • feet to many miles

  • increases with relative humidity

    • as humidity increases, so does microbe survivability

    • droplet transmission

26
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Noxious gases

  • may originate from many sources

    • manure or manure storage areas

    • feed storage - especially tower silos

    • heating devices

  • never enter a confined space without good ventilation support

27
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Carbon monoxide

  • a noxious gas that competes with O2 for transport sites

  • usual source is heaters operating at a reduced efficiency (ex. farrowing facilities)

28
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Nitrogen oxides

  • silo gas

    • forms during the fermentation process

    • crops high in nitrates are most at risk

    • heavier than air - accumulates toward the ground

  • causes lung pathology in humans and animals

    • high concentrations: immediate distress, collapse, death

    • lower exposure: respiratory congestion, water eyes, cough, difficulty breathing, fatigue, and nausea

  • safety must be exercised when entering silos and good ventilation is ideal

29
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Ammonia

  • manure and urine are the usual source

  • >25 ppm depresses muco-ciliary apparatus

  • increases respiratory disease

  • the smell of ammonia does not equal manure odor

30
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Manure gases

  • mixture of

    • methane

    • nitrogen oxides

    • sulfur oxides

  • release rate may be increased during agitation of storage areas

  • results in acute and chronic lung pathology

31
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How does housing contribute to disease?

  • impacts from:

    • ventilation

    • sufficient space

    • animal management

    • cleanliness

    • dryness

    • appropriate lighting

    • allowance or normal behaviors

32
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Factors to consider with housing

  • animal welfare

    • space requirements

    • adequate facilities for examination and treatment

  • animal physiology and behavior

    • dry bedding

    • ventilation

    • good footing

  • weather conditions

    • wind breaks

    • cold/heat stress

33
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Lighting

  • adequate lighting in confined systems

  • chickens

    • pullets no more than 10 hours of light daily

    • laying hens → 14-16 hours of light daily to stimulate egg production

    • meat birds → constant low-level light