1
Q
What is the coexistence of microorganisms and parasites with a living host called?
A
Symbiosis
2
Q
What does “symbiosis” literally mean
A
Living together
3
Q
What is the type of symbiosis where two organisms live together without disadvantage to either?
A
Mutualism
4
Q
What is the type of symbiosis where one partner benefits but the other is unaffected?
A
Commensalism
5
Q
What is the coexistence of two organisms where one causes damage and disease to the other?
A
Parasitism
6
Q
Enumerate the factors in host–parasite relationship
A
- Entry to the host
- Must not be destroyed and not destroy a vital function of the body
- Must multiply
- Must be released from the host and be able to get into the next host or cells
7
Q
What is the result of the interaction of host, agent, and environment?
A
Disease
8
Q
Enumerate the 3 important factors of disease causation:
A
- Host factor
- Agent
- Environment
9
Q
What is the term for the ability of a host to resist infection or disease?
A
Resistance
10
Q
Enumerate the 4 types of host resistance:
(G-A-I-N)
A
- Genetic (natural) resistance
- Age resistance
- Immune resistance
- Nutritional resistance
11
Q
Genetic (Natural) Resistance is?
A
The agent may enter the host but not become established.
Lesions depend on the foreignness of the agent.
Example: Pneumostrongylus tenuis causes no lesions in white-tailed deer, but chronic encephalitis in moose.
Example: Hog cholera virus affects only pigs.
12
Q
What type of resistance is determined by the host’s genetic make-up and species specificity?
A
Genetic (natural) resistance
13
Q
Agent may infect only young animals or vice versa.
Example: Canine parvovirus affects only puppies (below 1 yr old).
A
Age Resistance
14
Q
What type of resistance depends on the age of the host?
A
Age resistance
15
Q
Obtained through previous exposure or immunization.
A
Immune Resistance
16
Q
What type of resistance is acquired through previous infection or vaccination?
A
Immune resistance
17
Q
Animals in good nutritional condition are more resistant to disease.
A
Nutrional resistance
18
Q
What type of resistance is enhanced by good nutrition?
A
Nutritional resistance
19
Q
What refers to the ability of an organism to invade and cause lesions?
A
Virulence
20
Q
What refers to the degree of pathogenicity measured as morbidity or mortality?
A
Virulence
21
Q
Enumerate the factors that contribute to the virulence of an organism:
A
- Toxin production
- Enzymes
- Number of invaders
- Tissue affinity
- Resistance of the host
22
Q
What is the affinity of an agent to a particular tissue of the host due to biochemical preference?
A
Tropism
23
Q
Give an example of tropism.
A
Brucella has an affinity to the placenta because of its erythritol content.
24
Q
What is the ability of an agent to spread and persist in the host called?
A
Persistence
25
Enumerate the mechanisms for persistence of infectious agents:
**1. Intracellular existence** (protection from immune system) – e.g. Salmonella sp.
2. **Ability to survive outside** the host – e.g. FMD virus, Clostridia spores
3. **Ease of spread** (e.g. FMD virus via aerosol 40–60 miles)
26
Enumerate the 3 forms of **disease expression:**
1. Clinical disease
2. Subclinical disease
3. Latent infection
27
What is the form of disease with **abnormal functional/morphological changes and visible signs?**
Clinical disease
28
What form shows **no obvious illness** but causes reduced growth or production?
Subclinical disease
29
What form occurs when a host harbors and **excretes a pathogen** with **no clinical signs?**
Latent infection
30
What is considered the most important factor of disease causation?
Environment
31
What can turn subclinical or latent infections into clinical diseases?
Alterations in environmental conditions
32
What bacterial disease results from rapid accumulation of organisms?
Acute bacterial disease
33
Through what routes do bacteria typically enter?
Skin, digestive, respiratory, or urogenital tract
34
Enumerate the ways disease is produced in acute bacterial disease:
1. Necrosis of cells
2. Host’s immune response
3. Direct effects of toxins on tissue cells
4. Effects on the blood (e.g. sludging, DIC)
35
What bacterial disease **involves long-term persistence** of the agent **causing localized lesions?**
Chronic bacterial disease
36
Enumerate the ways disease is produced in chronic bacterial disease:
1. **Space-occupying lesions** (granulomatous inflammation)
2. **Large abscess with systemic infection**
37
Enumerate the **requirements of bacteria for pathogenicity:**
a. **Enter into the host** by surviving on and penetrating mucous membranes
b. **Multiply in vivo**
c. **Avoid stimulation of host’s defense mechanism**
d. **Damage the host**
38
Enumerate the effects of bacteria on the host:
1. **Production of aggressins** (impair phagocytosis)
2.** Attachment to epithelial surfaces** and **toxin secretion** (e.g. enterotoxigenic E. coli)
3. **Invasion and destruction of epithelial cells** (e.g. Shigella sp.)
4. **Invasion of lamina propria** for dissemination (e.g. Salmonella)
39
Enumerate the 3 main ways viruses cause disease:
1. Cytolysis
2. Maintain a steady state within the host
3. Integrate into the genome of the host
40
Enumerate the cytolytic effects of viruses:
1. Destruction of host cell after intracellular viral maturation
2. Release of infectious viruses to infect new cells
3. Production of compounds toxic to host cells
4. Release/activation of lysosomal enzymes causing lesions
41
What type of infection allows the host cell to survive while continuously producing viruses by budding?
Steady-state infection
42
Steady-State Infection example?
RNA viruses
43
What type of infection involves viral integration or masking by antibodies?
Integrated infection / Slow virus infection
44
Integrated infection / Slow virus infection example?
**Oncogenic viruses, agents of visna and scrapie**
45
Enumerate examples of specific tissue affinities of viral agents:
1. Coronavirus (TGE) – villus epithelia
2. Rotavirus (calf diphtheria) – upper half of villus
3. Rotavirus (epidemic diarrhea of mice) – tip of villus
4. Parvovirus (panleukopenia in cat) – crypt epithelium
46
What type of agents cause disease through local destruction, circulation interference, space occupation, or nutritive competition?
Parasites
47
What mechanism of parasitic disease involves direct destruction of host cells or tissues?
Local destruction of cells or tissues
48
Give examples of parasites that cause local destruction of cells or tissues.
*Coccodia*, migrating nematodes
49
What parasitic effect involves disturbance of blood flow and circulation?
Affecting blood circulation
50
Give examples of parasites that affect blood circulation.
*Strongyle* infection in horses **(thrombosis & infarction);**
**blood-borne protozoa** (sludging, microthrombi, DIC);
**Hookworms** (anemia)
51
What parasitic effect involves formation of lesions or occupying host tissues?
Space-occupying lesions
52
Give examples of parasites that cause space-occupying lesions.
*Trichinella* and *Cysticercus* (encyst in muscles);
*Spirocerca lupi* (granuloma in esophagus)
53
What parasitic mechanism involves competition for nutrients with the host?
Nutritive competition
54
Give an example of a parasite that causes nutritive competition.
*Ascarids*
55
What type of agents can cause disease by invasion, allergy, or toxicosis?
Fungi
56
What fungal mechanism involves direct invasion of tissues?
Give examples of fungal diseases caused by invasion of living tissues.
**Invasion of living tissues**
= *Blastomycosis, Histoplasmosis*
57
58
What fungal mechanism causes hypersensitivity to fungal antigens?
Allergies / Hypersensitivity
59
Give an example of a fungal allergy and its cause.
*Micropolyspora faeni* – found in **moldy hay** inhaled by humans & cattle, **causes Farmer’s lung**
60
What fungal mechanism involves poisoning due to ingestion of toxic fungal metabolites?
Toxicosis
61
Give examples of fungi that cause toxicosis.
*Aspergillus flavus, Aspergillus parasiticus* (produce **hepatotoxins** found in moldy grains & nuts)
→ *Fusarium* sp. – present in **moldy corn**
62
Enumerate the ways fungi cause disease:
1. Invasion of living tissues (e.g. Blastomycosis, Histoplasmosis)
2. Allergies and hypersensitivity (e.g. Micropolyspora faeni → Farmer’s lung)
3. Toxicosis (e.g. Aspergillus flavus, A. parasiticus, Fusarium sp.)
63
What are poisonous substances that cause degeneration or necrosis of cells?
Toxins
64
What are the two main ways toxins cause disease?
**Direct contact** and **absorption through skin, digestive or respiratory tracts**
65
What happens when toxins act by direct contact?
Degeneration or necrosis of the cells
66
How do toxins enter the host besides direct contact?
By absorption through skin, digestive or respiratory tracts
67
What determines the severity of toxin effects?
Dose dependence
68
Enumerate the ways toxins cause disease:
a. By direct contact – causes degeneration or necrosis of cells
b. By absorption through the skin, digestive, or respiratory tracts
69
Enumerate the characteristics of toxin effects:
1. Dose-dependent in nature
2. May cause local or systemic degeneration/necrosis
70
What is the transfer of an infectious agent from one host or object to another called?
Mode of transmission
71
Enumerate the 6 modes of transmission of infecting agents:
1. Sexual contact
2. Vectors (arthropods)
3. Fomites
4. Excretions or secretions
5. Food
6. Airborne
72
Examples: Vibriosis, Leptospirosis, Trichomoniasis
SEXUAL CONTACT
73
What mode of transmission occurs via copulation or sexual activity?
Sexual contact
74
Examples: Anaplasmosis – mosquito; Swine pox – lice
VECTORS (ARTHROPODS)
75
What mode of transmission involves insects or arthropods
Vectors
76
Any inanimate object or substance other than food that carries infection
Examples: harness – Ringworm, vehicles – Brucellosis
FOMITES
77
What transmission route involves body fluids or excretions?
Examples: Brucellosis, Leptospirosis
EXCRETIONS / SECRETIONS
78
What transmission route involves ingestion of contaminated food?
E.g = pasture – Anthrax, Erysipelas; moldy food – Mycotoxicosis
Food
79
Examples: dust – Pinkeye, Shipping fever; spores – Anthrax
**route involves inhalation of infected air or particles**
AIRBORNE
80
What type of relationship involves one organism benefiting at the expense of another?
Parasitism
81
What can be the range of harm in parasitism?
From mild discomfort to severe illness or death
82
Enumerate the types of parasites under parasitism:
1. Obligate parasites – cannot survive without a host
2. Facultative parasites – can live freely but exploit a host when available
83
type of parasite cannot live independently and requires a host for survival and reproduction?
Obligate parasite
84
Give examples of obligate parasites.
Certain bacteria and viruses such as HIV and Mycobacterium leprae
85
What type of parasite can live independently but may infect a host opportunistically?
Facultative parasite
86
Give an example of a facultative parasite.
Candida albicans – causes opportunistic infection in immunocompromised hosts
87
What relationship benefits one organism while the other is neither harmed nor helped?
Commensalism
88
examples of commensal relationships
E. coli in intestines (helps digestion, harmless to host)
→ Skin flora bacteria
89
What type of host–parasite relationship benefits both organisms?
Mutualism
90
Give examples of mutualism.
→ Symbiotic gut bacteria aiding digestion and vitamin synthesis
→ Bees pollinating flowers while obtaining nectar
91
Enumerate the factors influencing pathogen-host dynamics:
1. Co-evolution
2. Disease severity
92
What is the process by which hosts and parasites evolve together, adapting to each other?
How does this affect virulence?
**Co-evolution**
-Some pathogens evolve to become less harmful to ensure host survival.
93
What factor determines how severe a parasitic disease becomes?
Host immunity and environmental conditions
94
What can cause variation in disease severity among hosts?
Differences in immunity or environmental stressors
Pathology 141
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