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VBSC 50 Quiz 3: Disease Conditions

Terms in this set (83)

Infectious Disease Triad
- Host factors revolve around the abilities of the immune response
- Influenced by nutrition
- Disease severity a function of agent pathogenicity, virulence
- Mode of pathogen transmission
Environment, agent, host
Host-Pathogen Interactions
- Pathogens
- Host susceptibility
- Modes of pathogen shedding
- Reservoir host
- Routes of entry
- Modes of transmission
Modes of Transmission
- Direct
- Direct contact
- Droplet spread
- Indirect
- Airborne
- Fomite borne
- Vector borne (mechanical or biological)
Prokaryotic Cell Types
- No organized nucleus
- No organelles other than ribosomes
- Plasmids: pieces of DNA
- Plasma membrane
- Cell wall: determines type
- Pilli and/or flagellum for attachment
Bacterial Cell Wall
- Cell staining characteristics
- Gram-negative bacteria
- Gram-positive bacteria
Steps in Bacterial Disease Process
- Invasion of body: respiratory, ingestion, wound entry
- Evade immune response: induce immune suppression, hide in cells
- Once in the body, bacteria will colonize locally, systemically, or in specific tissues: leptospira, clostridium, brucella
- Once established, bacteria will cause tissue damage via: inflammatory reaction, release of toxins
Leptospira
Colonizes in the kidney
Clostridium
Colonizes intestine or dead tissue of wounds
Brucella
Preferentially colonizes in reproductive tract
Anaplasmosis
- Blood parasite by Anaplasmosa spp.
- Spreads by ticks
- Prevalence higher in southern states, though moving north
- Control
- Low level tetracyclines
- Immunization
- Some states require testing for entry
Anthrax
- Bacteria: Bacillus anthracis
- Spore-forming bacteria
- Many modes of transmission: zoonotic, aerosol, ingestion, vector-borne (mechanical), direct contact
Tularemia
- Bacteria: Francisella tularensis
- Zoonotic disease
- Complex ecology in environment
- Many modes of transmission: direct contact (animals/carcasses), inhalation, contaminated food/water, indirect via various insects (mechanical vectors)
Mastitis
- Various bacterial agents can induce mastitis
- Bacterial penetration of streak canal
- Fomite transmission
- Contagious pathogens: through milking process
- Environmental pathogens: contaminated bedding material
Clostridium spp.
- Affect a range of species
- Some disease types are seen more in selected species
- Disease based on release of exotoxins
- Clostridium difficile: common disease resulting in colitis in humans
Tetanus
- Clostridium tetanii
- Vegetative organism common in GI tract of horses and some other species
- Exposure usually via contamination of a wound
- Anaerobic conditions in wound promote growth or organism and production of neurotoxin
Virus
Parasitic life form that requires another living cell to complete replication
Virus Structures
- Viral genome (DNA or RNA)
- Capsular proteins
- +/- Envelope
- Surface proteins
Virus Shapes
- Helical
- Polyhedral
- Spherical
- Complex
- It is debated whether viruses are "alive"
- Viruses hijack a host cell and take over cell organelles to propagate their genome
- Viruses can lyse, mutate, or alter cell function resulting in disease
- Different viruses attack different cell types
How do viruses cause disase?
Viral Replication Process
- The virus enters the cell body releasing RNA, or DNA
- Virus RNA invades the cell nucleus and takes over
- Viral RNA uses the host cell to create new RNA and assemble more viral particles
- New viral particles are released, sometimes destroying the cell in the process
Rabies
- Family: Rhabdoviridae
- Genus: Lyssavirus
- Single non-segmented negative stranded RNA genome
- At least 7 Lyssavirus species or genotypes cause rabies
- Recently, 4 new Lyssaviruses collected from Eurasian bats have been described
Rabies Transmission
- 99.99% of exposures are through bites
- Other recognized ports of entry include saliva contact with: mucous membranes and breaks in skin
- Aerosolization of virus
- Two types of disease: furious and dumb
Warts
- Most warts are caused by a virus
- Papilloma viruses specific to a wide number of species
- Double-stranded DNA virus
- Induce cellular growth, benign tumors or cancerous growths
- Transmitted by contact
BVD Virus
- Bovine Viral Diarrhea
- Can directly cause disease in non-immune animal
- Can pass placenta and cause deformities or death of fetus
- Can cross the placenta and become part of the fetus (persistently infected)
Foot and Mouth Disease
- Foreign animal disease fo U.S.
- Picornavirus: single stranded RNA virus
- Multiple serotypes to virus
- Highly transmissible disease that affects many species (direct contact, indirect contact, fomites)
Epizootic Hemorrhagic Disease
- Disease caused by two different viruses: EHD virus, bluetongue virus, many serotypes
- Acute vs. Chronic disease
- Transmitted by Culicoides midges
Parvovirus
- Viral agent: Parvovirus (single stranded DNA virus)
- Causes intestinal disease with diarrhea, vomiting, malaise, especially in puppies
- New variant recognized in 2000
- Transmitted by contact with feces
- Vaccination can be protective
Parasitology
- Branch of zoology and of medicine that studies parasitism and all its relations
- Current convention is to limit parasitology to study of parasites from animal kingdom: insects and arachnids, helminths (flat and round), protozoa, chordates
- Bacteria and Rickettsia (Bacteriology)
- Viruses (Virology)
- Fungi (Mycology)
Parasitism
- Symbiosis in which an organism (parasite) lives on or in another host and draws in nourishment there from
- Historically implied to be deleterious to host
- Prevalence of parasites and intensity of infection in host are nonrandom
- Range in physiologic, biochemical dependence
Definitive Host
Host in which the parasite reproduces sexually
Intermediate Host
Host in which the parasite is sexually immature or reproduces asexually, and is required to complete the life cycle
Paratenic/Transport Host
Host in which there is no development and is not required to complete the life cycle
Reservoir Host
Host in which an infection is unapparent but may act as a source of infection to hosts important to humans
Abberant (Dead End) Host
Host that is not suitable to the parasite's life cycle, potential for serious disease
Coccidia
- Enteric protozoal parasite of many species though species specific
- Direct life cycle, but elaborate reproductive process
- Transmission via contamination of the environment
Role of Vectors
Anthropod, mollusk, or other invertebrate that transmits a parasitic agent to a vertebrate host and can act as either a definitive or intermediate host
Types of Vectors
- Mechanical Vector: transmits parasite from one host to another; no development takes place
- Biological Vector: required for the life cycle of the parasite; development or replication takes place
African Sleeping Sickness
- Caused by protozoan parasite Trypanosoma (blood parasite)
- Tsetse fly is the biological vector (indirect life cycle)
- Causes severe disease leading to coma
- Prevent through fly control
- Physical and mechanical damage: obstruction, fibrosis
- Invasion and cell destruction
- Nutritional losses
- Immunologic responses
- Physiologic disturbances
- Disease transmission
How do parasites cause disease?
Parasitic Control Basics
- Need to understand the life cycle and where interventions may break the cycle
- Chemotherapeutic agents
- Targeting the parasite
- Targeting the vector
- Environmental controls: minimize exposure
Cryptosporia parvum
- Direct life cycle protozoal parasite
- Causes severe diarrheal disease
- Zoonotic disease passed among many different species
- Common disease of calves and veterinary students
Toxoplasma gondii
- Zoonotic protozoal parasite
- Complex, indirect life cycle with many potential hosts
- Cat is the definitive host
- Intestinal disease of cats, but is self-limiting
- Serious potential disease in pregnant women
- Control through minimizing contact with infectious agent
Malaria
- One of the most important parasitic diseases
- Indirect life cycle with complex development
- Mosquito is biological vector and definitive host
- Human is the intermediate host
- Much research addressing drug resistance and control methods
Schistosomiasis
- "Blood fluke" trematode parasite
- Indirect life cycle with humans (DH) and snails (IH)
- 3 important species that cause disease in humans
- "Egg granulomas" in various tissues
Dipylidium caninum
- Common tapeworm of dogs and cats
- Intermediate host is the dog or cat flea
- Potentially zoonotic, need to inadvertently consume infected flea
Ancylostoma caninum
- Common hookworm of dogs and cats
- Direct life cycle
- Environment contamination important part of disease transmission
- Larval stage can cause disease in humans
Hemonchus contortus
- "Barberpole" worm of ruminants
- Most serious worm for sheep and goat production
- Direct life cycle
- Adult worms are in abomasum and significant blood feeders
- Significant problem with drug resistance in sheep and goats
Dirofilaria immitis
- Heartworm disease of dogs and rarely cats
- Indirect life cycle
- Significant disease of dogs with reservoirs in wild canids
- Control with monthly ivermectin-type medications
Scabies
- Sarcoptic mange caused by Sarcoptes scabiei
- Fairly species specific but potential for short-term transfer
- Mites live in and burrow through dermal layers
- Induce a rash that is very pruritic (itchy)
Ticks
- Two groups: hard ticks and soft ticks
- Life cycles: 1-host, 2-host, 3-host, multiple hosts
- Primary issue is the transmission of many different disease agents
Lice
- Ectoparasites of many species: biting lice, chewing lice
- Entire life cycle is on the host
- Eggs (nits) attached to hairs
- Sucking lice if in high numbers can cause anemia
- Biting lice can cause itching and hair loss
Anthroponoses
Diseases transmitted between humans
Zoonotic Disease
- Disease agent that is passed from animal to human to induce disease clinical signs
- Most now use "zoonosis" to describe
Sapronoses
Disease obtained from the environment and not from a living individual
Zoonoses Agents
- Bacterial
- Viral
- Rickettsial
- Protozoal
- Helminthic
- Fungal
- Ectoparasitic
Zoonotic Diseases of Most Concern in U.S.
- Zoonotic influenza
- Salmonellosis
- West Nile Virus
- Plague
- Emerging coronaviruses
- Rabies
- Brucellosis
- Lyme Disease
Disease Transmission
- Multiple modes for infectious agents to pass from animal to human host
- Direct Contact
- Indirect Contact: vector-borne, food-borne, fomite
- Importance of reservoirs
Emerging Diseases
- Of the >1700 pathogens affecting humans, 833 are zoonotic
- Of the 156 emerging pathogens, 113 are zoonotic
- Many zoonotic pathogens become established in wildlife before transmission to humans and domestic animals
Plague
- Pathogen: Yersinia pestis
- Responsible for the "Black Death Plague" in Europe in the Middle Ages
- Various rodents serve as reservoir hosts to the bacterium
- Transmission modes:
- Rodent fleas primarily responsible
- Contact with contaminate fluids or tissue from infected animal
- Infectious droplets
- Commonly seen in parts of Africa and Asia as well as western parts of the U.S.
- Rodent hosts not affected
- Cats very sensitive to disease
- Humans have three forms depending on transmission mode: bubonic (flea bite), septicemic (flea bite or direct contact), and pneumonic (aerosol)
Lyme Disease
- Borreliosis
- Agent: Borrelia burgodorferi (bacteria)
- Widespread distribution, especially northeast U.S.
- Reported incidence variable
- Transmitted by 3-host ticks
- Reservoir hostL white-footed deer mouse
- Syndromes described in dogs and horses
Toxoplasmosis
- Cats can clear the infection with age
- Only young kittens high risk for disease
- Many intermediate hosts that can harbor tissue cysts
Trichinosis
- Control in swine by prohibiting garbage feeding without cooking
- Rat control
- Cook wild meats completely
- Curing methods may inactivate larvae
Nutritional Triad
- Understanding the animal
- Feed analysis, nutrient content
- Feeding management, nutrient delivery
Digestive Process
- Ingestion
- Mastication
- Digestion/Fermentation
- Absorption
- Utilization
- Excretion
Essential Nutrients
- Water
- Energy
- Amino Acids
- Fatty Acids
- Minerals (macro, micro)
- Fiber (to contain microbes, gut health)
Requirement Modifiers
- Genotype/breed: body size, metabolic rate
- Environment: temp, humidity
- Gender: intact, castrated
- Production level
- Composition of gain, milk, efficiency of gain
- Work/activity level
- Nutrient bioavailability
- Health status
- Toxins, inhibitors
Essential Nutrient Assimilation
- Depends upon digestive tract design and feeding behavior
- Carnivores: simple GI tract with large stomach
- Omnivores: highly variable GI tract with some expansion of tract to accommodate fiber fermentation
- Herbivores: complex GI tract to accommodate microbial populations for fiber fermentation
- Nutrient imbalances
- Deficiencies: absolute, secondary (induced)
- Excesses: direct, secondary (indirect)
- Clinical
- Subclinical (poor animal performance)
What is nutritional disease?
Metabolic Disorder
Inability to maintain body homeostasis for a nutrient or physiologic function
Energy Deficiency
- Marasmus: exclusive dietary energy deficiency
- Protein-Energy malnutrition: various stages of starvation
- Loss of body weight
- Loss of body condition
- Monitor with body condition scoring
Energy Excess
- Obesity: varying levels of excess body mass, mainly adipose (fat) tissue
- Many secondary disease impacts from being obese
- Routine monitoring of body condition
Body Condition Scoring
- Systematic, but subjective, method of assessing subcutaneous fat
- Typical scoring systems are 1 (emaciated) to 5 (obese)
- Scoring system may include ½ scores
- Need to feel bony prominences to determine layer of fat
Protein-Related Disease
- Requirement is for amino acids: essential, nonessential
- Dietary protein composition: digestibility, amino acid composition, biologic value
- Amino acid deficiencies: poor haircoat, weight loss
- Kwashiorkor (true total protein deficiency): enlarged abdomen with fluid, skin and hair discoloration, lesions, poor growth, productivity
Unique Requirements for Cats
- Cats have highest protein requirement for any species
- Vitamin A needs to be preformed
- Niacin preformed
- Arachidonic acid
- Taurine
Mineral Related Diseases
- Primary issues are with calcium and phosphorus relative to bone development
- Nutritional hyperparathyriodism
- Rickets/Osteomalacia
- Lactational eclampsia
Urolithiasis (Urinary Stones)
- Commonly diagnosed problem in companion animals (dogs and cats)
- Debilitating and life-threatening disease process
- Almost exclusively seen in males, intact or castrated
- Requires early recognition and prompt therapy
- Medical/surgical management not uniformly successful in long term recovery
Vitamin Related Diseases
- Fat-Soluble: rickets, bony changes, pansteatitis
- Carnivores cannot make Vitamin D in skin
- High in take of vitamins with animal tissues
- Water-soluble
- Not stored in body so need to be continuously consumed
- Cooking can destroy in some foods
- B12 required from animal sources
- Thiamin (B1) most common deficiency
Energy Related Diseases
- Herbivores can also experience inadequate or excess energy intake
- Negative energy balance often associated with start of lactation or late pregnancy
Pregnancy Toxemia
- Pregnancy disease, twin lamb/kid disease, pregnancy ketosis
- Metabolic disease of late pregnancy due to negative energy balance
- Deficiency of glucose to support fetus
- Excess lipid mobilization
- Characterized by poor appetite, weakness, depression, dullness, neurological signs, blindness, incoordination progressing to coma and death
Rickets
- Typically seen in weaned animals
- Inappropriate mineral supplementation
- Rapid rate of growth
- Potential nutritional causes are deficiencies of Ca, P and Vitamin D
Copper Toxicity
- Toxicity
- Acute toxicity
- Subacute to chronic: liver accumulation
- Clinical signs: anorexia, depression, weakness, and diarrhea
- Caused by high dietary intake inappropriate for species
Selenium Deficiency
- Disease process termed nutritional myodegeneration
- Clinical deficiency of selenium resulting in muscle degeneration
- Vitamin E is protective in Se deficiency
- Muscle lesions can occur anywhere but typically seen: tongue, heart, leg muscles
One Health Approach
- Concept that human and animal diseases are interlinked has been proposed in the 18th century
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