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Animal Disease 1 > Infectious Agents and Diseases > Flashcards

Infectious Agents and Diseases Flashcards

1
Q

Define pathogen.

A

Anything that can produce disease. An infectious agent such as a virus, bacterium or other microorganism that causes disease in its host.

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2
Q

Define infection.

A

Invasion of a host’s bodily tissues by a disease-causing agent, the agent’s multiplication, and the reaction of host tissues to the agent and toxins it produces.

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3
Q

Define transmission.

A

Passing of a communicable disease from an infected host individual or group to another individual or group.

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4
Q

Define microorganism.

A

Microscopic organism, may be a single cell or a multicellular organism.

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5
Q

Define pathogenicity.

A

Potential capacity of a particular species of microorganism to cause disease.

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6
Q

Define zoonosis.

A

An infectious disease that is transmitted from animals to humans or from humans to animals (sometimes known as reverse zoonosis).

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7
Q

Define virulence.

A

Degree of pathogenicity within a group or species of agent of infectious disease, as indicated by host fatality rates and/or the ability of the agent to invade the tissues of the host.

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8
Q

Define vector.

A

Any living organism that carries and transmits an infectious agent into another living organism.

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9
Q

List the taxonomic categories of agents causing infectious diseases in animals and man.

A

Viruses
Bacteria
Fungi
Protozoa (parasite)
Helminths (parasite)
Arthropods (parasite)
Prions
Cancerous tissues

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10
Q

What is foot and mouth disease?

A
  • Highly contagious
  • Affects the upper alimentary tract and feet
  • Affects cloven hoofed animals: all antelope, bovine, deer, goat, sheep and pig species
  • Extremely resistant and can survive in environment for a very long time
  • Severity depends on type/subtype and host animal species
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11
Q

What is rabies virus?

A
  • Acute encephalitis in warm blooded animals
  • Transmission mostly through bites from infected animals
  • Long incubation period before clinical signs appear
  • Fatal within 6-14 days of onset of clinical signs
  • Globally important zoonosis
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12
Q

What is influenza virus?

A
  • Waterborne, enteric infections in wildfowl
  • Adapts readily to domestic fowl, domestic animals and humans
  • Many different types varying in their pathogenicity for different species of animals and man, which can cause major pandemics
  • Evolving constantly and new types appear every year through genetic mutation and recombination of genetic material
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13
Q

What is coronavirus?

A
  • Well known as causing various diseases in poultry, pigs, cattle and cats for a long time
  • Natural host are bats, very large number of coronaviruses
  • Originally found in poultry in 1930s
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14
Q

What is E.coli?

A
  • Gram-negative rods with flagella
  • Can cause intestinal disease in many species of animals especially in young animals. Generally mild illness, lasts few days
  • Some are zoonotic and can be acquired by humans
  • Occasionally complications, especially in children and the elderly
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15
Q

What is brucella?

A
  • Brucella abortus, Brucella melitensis, Brucella suis
  • Intracellular, Gram-negative rods
  • Abortion, infertility and chronic arthritis in ruminants, swine and humans
  • Transmission via birth materials
  • Important globally as a zoonosis
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16
Q

What is mycobacterium bovis?

A
  • Bovine tuberculosis – still common in UK cattle
  • Intracellular bacteria, causing chronic disease
  • An important zoonosis
  • Wildlife reservoirs complicate eradication from domesticated animals: badgers (in the UK and Spain) and possums (New Zealand)
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17
Q

What is bacillus anthracis?

A
  • Anthrax
  • Gram positive rod
  • Causes rapid death in most animals
  • Spores can stay alive for decades in the soil
  • Disease reappears after floods, landslides etc.
  • Affects farm animals, humans and also elephants, hippos
18
Q

What is clostridium botulinum?

A
  • Gram-positive rods
  • Grows in anaerobic conditions
  • Pathogenic effect through toxin production (‘Botox’)
  • Toxins produce paralysis in extremely low quantities. Death through paralysis of respiratory muscles
  • Typically seen in summer, such as waterfowl on stagnant water
  • Toxic for humans: badly canned food
19
Q

What are fungi?

A
  • Large family of organisms, largely non-pathogenic
  • Mushrooms may be edible, therapeutic, poisonous and hallucinogenic
  • Yeasts: many are useful (baking, alcohol production) and some pathogenic (thrush, oral infections)
  • Moulds: antimicrobial producing moulds (Penicillium), decaying of dead material and spores can be important causes of disease
20
Q

What are some characteristics of pathogenic species of fungi?

A
  • Causing dermal infections, ringworm
  • Causing internal infections, coccidioidomycosis of lungs and aspergillosis
  • Producing harmful mycotoxins: Aflatoxicosis (Aspergillus flavus) and Ergotism (Claviceps purpurea)
  • In wildlife: white nose disease of bats in USA (Pseudogymnoascus destructans) and chytridiomycosis of amphibians (Batrachochytrium dendrobatidis)
21
Q

What are protozoa?

A
  • Single-celled eukaryotic microorganisms
  • Many species are in water, in intestines (e.g. in rumen of ruminants) and in other body systems (mostly pathogens)
  • Multiplication through binary fission, although sexual reproduction also occurs
22
Q

What are coccidia?

A
  • A broad group of protozoan parasites affecting all domestic animal species, most other mammals and many birds
  • Many cause gastrointestinal diseases
  • Others cause generalised systemic disease and reproductive losses
  • Both direct and indirect life cycles
  • Some infect a single host species and others have definitive and intermediate hosts
  • Undergo sexual reproduction and have sexual life cycle stages
23
Q

What is trypanosoma?

A
  • African trypanosomiasis (sleeping sickness): anaemia, weight loss and death in domestic animals and cerebral symptoms and death in humans
  • Extracellular blood parasite
  • Transmitted by tsetse fly
24
Q

What are macroparasites?

A

Multicellular organisms from various phyla:
- Helminths (worms) – roundworms, flatworms (flukes), tapeworms
- Insects – biting flies that may be disease vectors, blow flies, nuisance flies
- Acari (8 legged) – ticks and mites

25
Q

What are helminths?

A
  • From microscopic to metres long
  • Various locations: alimentary canal often as adults, liver e.g. liver fluke, both as larvae and adults, and other organ systems, often as larval stages
  • Often complicated life cycles, involving various hosts for different stages of development Three major groups: nematodes (roundworms), trematodes (flatworms/flukes) and cestodes (tapeworms)
  • Many different species in each group
26
Q

What are nematodes?

A
  • Roundworms
  • Mostly live in the gastrointestinal tract
  • Also found in lungs, heart, blood, liver, kidneys, skin, eye
  • Found in almost all domestic and wild animals
  • Many are harmless
  • Some cause a variety of diseases and sometimes death
27
Q

What are trematodes?

A
  • Flatworms
  • Parasitic species referred to as ‘flukes’
  • Generally have snail intermediate hosts
  • Liver fluke of cattle and sheep is the classic example
  • Very common cause of disease and losses in farm animals
  • Often zoonotic
28
Q

What are cestodes?

A
  • Tapeworm
  • Many species cause serious zoonoses of public health concern in the UK and globally
  • Intermediate hosts may be animals or insects, depending on cestode species
  • Larval stages may cause pathogenic cysts in intermediate hosts and sometimes in humans
29
Q

What are arthropods?

A
  • Insects: 6 legs, with a head, thorax and abdomen
  • Acari: 8 legs, with cephalothorax and abdomen
  • Many different species in each group
  • Some important as disease vectors
  • Others are pathogens in their own right
30
Q

What are the arthropod insects?

A
  • Important as disease vectors: mosquitoes, midges, tsetse flies, sandflies, fleas
  • Pathogens in tehri own right: fleas, horseflies, horn flies, blowflies, midges
  • Fly strike: larvae penetrate skin and cause severe lesions
31
Q

What are acari?

A
  • Ticks: many species, feed on blood of host, cause blood loss, irritation and may transmit diseases
  • Mites: microscopic organisms/sometimes just visible, live on or burrow in skin, causing irritation and lesions, can cause death in serious situations
32
Q

What are prions?

A
  • Abnormal brain protein – misfolded proteins that cause normal proteins to misfold
  • Accumulation of prion protein causes brain cell death in many animal species and man
  • Always fatal
  • Highly resistant to cleaning and disinfection
  • Bovine spongiform encephalopathy (BSE) is a famous example
  • Scrapie in sheep
33
Q

What is a canine transmissible venereal tumour?

A

A transmissible cancerous tissue.

  • Transmitted through sexual contact
  • First emerged in a dog that lived about 11,000 years ago
  • All CTVT tumours carry the DNA belonging to this “founder dog”
  • Generally self-limiting, regression after 3 to 6 months
34
Q

What is facial tumour disease in Tasmanian devils?

A

Transmissible cancerous tissues

  • Transmitted through fighting
  • Tumours interfere with feeding, death through starvation
  • Serious concerns for the conservation of the species
35
Q

How can pathogens be transmitted via ingestion?

A

After ingestion, pathogens may affect:

  • The intestinal tract: E.coli, salmonella, many viruses, some coronaviruses via the faeco-oral route. Gastrointestinal nematodes, transmitted via pasture or soil
  • Other organ systems: liver fluke, larval tapeworm cysts in peritoneal cavity, lungs, liver, brain, brucella abortus in reproductive tract and joints, bovine TB anywhere
36
Q

How can pathogens be transmitted by inhalation?

A
  • Pathogen enters lungs
  • Depending on pathogen type, lungs mainly affected or other organ systems involved
  • Foot and mouth disease – wind borne spread is possible, hence initial infection may be by inhalation. Clinical signs are nevertheless in virus predilection sites in upper alimentary tract and coronary band of hooves.
  • TB is acquired by inhalation initially develops in lungs and eventual spread to affect other parts of the body.
37
Q

How can pathogens be transmitted by inoculation and some examples?

A

Pathogen is injected into the body through vectors such as ticks or being insects. May cause local disease, but mostly cause systematic disease. Examples:

  • Virus – West Nile virus and Bluetongue
  • Bacteria – tick-borne fever and tick pyaemia
  • Protozoa – plasmodium and trypanosoma
38
Q

What is deposition?

A

Pathogen is deposited one the skin and spreads across or penetrates the skin: blow fly larvae, mites and ringworm. Biting insects ticks actively seek out their hosts: questing by ticks and attraction of flying biting insects to odours.

39
Q

What is vertical transmission?

A
  • Transmission of infection from 1 generation to the next
  • Disease agent crosses the placenta or perinatal transmission
  • Important in many viruses, bacteria and parasites
40
Q

What are 4 infectious agents that occur via vertical transmission?

A
  • Bovine viral diarrhoea virus
  • Mycobacterium avium paratuberculosis – a bacterial disease of cattle
  • Neospara caninum – a protozoan affecting cattle (Johne’s)
  • Toxocara canis – a common roundworm of dogs

Animal Disease 1 (25 decks)

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