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AVBS3001 > Parasitology > Flashcards

Parasitology Flashcards

1
Q

Parasite definition

A

Dependance on another for food and shelter

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2
Q

Endo vs Ecto parasites

A

Endo (inside)
- protozoa
- worms
Ecto (outside)
- insects
- arthropods

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3
Q

Cestodes cause problems for which host?

A

intermediate

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4
Q

What are the 5 types of hosts?

A
  • definitive host (where parasite becomes sexually mature)
  • intermediate host (temp environment for parasite to complete lifecycle)
  • paratenic (transfer host) (remains alive until can infect another host but doesn’t undergo development)
  • vectors (intermediate hosts and carriers)
  • reservoir hosts (harbour infection transmitted to humans)
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5
Q

What are parasite factors?

A

Dose
Virulence (ability to cause damage)
infectivity

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6
Q

What are host factors?

A

Innate resistance (genetic ususally)
previous exposure
passive immune status (neonates)
age
Reproductive status (preg, lactating vs non preg, sterile vs intact)

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7
Q

What are environmental factors?

A

Animal stocking density
animal movemnt between groups (rotational vs continous grazing)
Quarantine of new stock
Houseing (ventilation, sanitation)
Enviro conditions (temp, humidity, rainfall)
Nutrition (protein, energy and macromineral/ micromineral balance)

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8
Q

Host factors affecting parasitism?

A

age
exposure
amount of parasites
genetics
periods of stress
preg/lactating
management factors

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9
Q

Definitive host

A

parasite reaches sexual maturity and undergoes repro in this host

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10
Q

Reservoir host

A

non human definitive host which maintains parasite for possible human infection

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11
Q

Endoparasite

A

inside
protozoa
worms

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12
Q

Ectoparasite

A

outside
insects
arthropods

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13
Q

How is pathology produced?

A

production of something toxic or foreign material excereted
migration through tissues
host reaction (allergies/inflammation)

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14
Q

Host specific parasites

A

Narrow host range
well adapted
niche relation

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15
Q

Non host specific parasites

A

broad host range
possibility of paratenic hosts (resoivoirs)
zoonotic possibility

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16
Q

Arthropod

A

joined limbs
hard exoskeleton
head, thorax and abdomen
90% of all species on planet

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17
Q

Ectoparasite path

A

direct trauma
removal of metabolites and blood
allergic irritaion and dermititis
interference with functioin or behaviour

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18
Q

Ectoparasite vectors

A

Mozzies
Tsetse fly
Bufflo fly
Blackflies
Midges, snadflies
fleas
ticks (arachnid)

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19
Q

Types of vectors

A

Mechanical (infection directly to host –> not essential for lifecycle)
Biological (undergo development or multiply (essentail for life cycle

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20
Q

WHat are the HOT rumunanet nematodes

A

H barbers pole
O small brown stomach worm
T Black scour worm

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21
Q

What are the general features of parasitism (DAD)

A

Diarrhoea
Anaemia
Death

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22
Q

Conditions for encystment

A

loss of food source
* dessication
* increase in tonicity (salts)
* change in O2 concentration
* change in pH
* temperature change
* or terminal stage of a life cycle (ie. oocyst coccidia)

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23
Q

4 major protozoa groups

A

Amoebas
Flagellates
Cilliates
Sporozoa

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24
Q

How is malaria transmitted

A

Sporozoited injected with saliva
enter circulation
trapped in liver (recpetor ligand)

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25
Q

Which malaria is the worst and why?

A

Falciparum (constant high fevers that barely come down)

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26
Q

What is a pellicle

A

combination of plasma membrane and thin,
translucent, secreted envelope

IN FLAGELLETE

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27
Q

Tritrichomonas foetus causes what in cows

A

infertility
abortion up to 5 motnhs after breeding

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28
Q

What is the gold standard?

A

The “artificial insemination” industry
prescribes for bovine trichomonosis
a rigorous protocol of six weekly T. foetus
negative cultures for bulls older than 365
day of age.
GOLD STANDARD

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29
Q

Water borne disease

A

Cryptosporidiosis caused by Cryptosporidium spp.
feacal oral
diarrheoa
NO TREATMENT

30
Q

Food borne disease

A

Trichinellosis (trichinosis) caused by Trichinella spp.
through meat (worms)
reproduce in body and babies go into muscles
Pigs intermediate host

31
Q

What are examples of secondary tests

A

Oxidase
Catalase
O/F (Oxidative/fermentation

32
Q

What are examples of tertiary tests

A

Acetoin
CAMP
Carb fermentation
Clumping
Enteropluri
lactose fermentation
motility
Oxi/ferm
sorbitol
sucrose
urea
trehalose

33
Q

How would you best control strangles

A

Quarantiine

34
Q

What is an obligate parasite?

A

a parasite that depends on a host for nourishment, repro, habitat and survival. Can’t survive away from host.

35
Q

What is a saprophyte

A

An organsim that gets its nourishment from dead or decaying organisms
Fungi

36
Q

Give an example of an obligate parasite

A

Flea, tick, louse, blood fluke, takeworm etc.

37
Q

Classes of Mycoses

A

– Opportunistic mycoses
– Dermatophytes
– Systemic mycoses
– Mycotoxicoses

38
Q

Opportunistic mycoses

A

saprophytes
mucosal commensals
Chronic lesions (reponse resembles that to foreign bodies)

39
Q

Aspergillus

A

Opportunistic mycoses
Ubiquitous saprophytic moulds
Cause respitory disease
Outbreaks occur when large numbers of conidia are inhaled or penerate eggs

40
Q

Aspergillus fumigatus

A

conidial nd hyphal adhesions
triggery proinflammatory cytokines (cell wall)
exoenzymes
catalase
siderophores
melanin (free radical scavenger)
Caseating tubercle-like lesion in which hyphae may be seen

Horses - topical tratment (antifungal)
Clean environment, sanitise and ventiation (all animals)
Cause encephilitis in eggs

41
Q

Cryptococcus neoformans

A

Yeast
– Spherical cells single bud attached by a slender stalk
– Surrounded by a polysaccharide capsule
– Grow rapidly (2-4 days) on blood agar or Sabouraud agar
– Creamy white colonies variably mucoid
– Worldwide distribution
– Serotypes A – C. neoformans var grubii
– Serotypes B & C – C. neoformans var gattii
– Serotype D – C. neoformans var neoformans

– Ecological niche
* Grows well in bird poo

– C. neoformans var. gattii =
Certain eucalyptus species
provide saprophytic niches

– Tropism for nervous tissue

– Virulence
– Capsule
* Inhibits phagocytes
* Activates the alternative complement pathway
* Suppresses leucocyte migration
* Depresses antibody synthesis
– No evidence of transmission between animals
– Environmental exogenous infection
– Inhalation
* Nasal, sinuses and brain
– Direct entry via wounds
– Granulomatous lesions

– Disease usually occurs in animals with cell mediated
immunity deficit
(except C. neoformans var. gattii)
– Young
– AIDS patients
– FIV in cats
– Koalas ??
* Housing in niches
* Koala susceptibility
– C. neoformans var. gattii virulence
– Diagnosis
– Latex cryptococcoal agglutination test (LCAT)
* Detects the presence of capsular antigen in serum or CSF
* Crypto-LA test

42
Q

Dermatophytes

A

Fungi associated with the skin
- Microsporum
* M. canis → carnivores (cats and dogs)
* M. gypseum → horses
- Trichophyton
* T. equinum → horses
* T. verrucosum → cattle

43
Q

Classification of Dermatophytes

A

Geophilic
– Inhabit the soil
– Infections of animals due to prolonged exposure
of contaminated soil
– Sporadic
– Not easily spread from animal to animal (not
very contagious)
– Hair in soil enhances infectivity
– Infections promoted by wet conditions and biting
insects

Zoophilic
– Specialised skin parasites of animals
– Some easily infect species other than
preferred host
– Young animal in close contact ✓
* Contagious
– High humidity and temperature✓
– Skin trauma and poor nutrition ✓
– Concurrent disease ✓

Anthropophilic
– Specialised skin parasites of humans
– Survive briefly in soil
– May infect animal

44
Q

Dermatophyte pathogenesis

A

– Entry via skin abrasion
– Conidia (asexual spores) can survive for long
periods in moist environments
– Up to 3 years in some species
– Hyphae invade walls of hair follicle.
– Hyphal tip penetrates the hair cortex both by
pressure and by hydrolysing the keratin
– Secondary bacterial infection of follicles
– Antigens are highly allergenic and induce a
delayed hypersensitivity reaction

45
Q

Dermatophytes Diagnosis

A

– Microscopy examination of skin scrapings

– Culture
– Sabouraud agar
– Dermatophyte Test Medium

46
Q

Dermatophytes: Treatment, prevention and control

A

– UV light can have some curative effect (sunlight)
– Some may be self-limiting
– Clipping hair
– Topical treatment
– Iodine
– Imidazoles (inhibit ergosterol synthesis)
– Antisepetic rinses and antifungal shampoos

– Prolonged treatment necessary
– Does not stop spread
– Does prevent re-infection
– DISINFECT THE ENVIRONMENT !!!
– Bleach, Iodine and most common disinfectant
– Inanimate objects (fomites), bedding and rugs
etc..
– Drying and exposure to sunlight !!!

– **Isolation if zoophilic !!

47
Q

Microsporum canis

A

– Zoophilic
– Natural host is the cat
– Ringworm in cats and dogs
– Can infect many species including humans
– Zoonosis
– Carriers in cats and dogs
– ~ 50% will fluoresce under Wood’s lamp
– Colony appearance
– Fluffy, white to yellow flat colony with
radiating edges
– The reverse surface exhibits a lemony to
chromic yellow pigment
– Microscopic features
– Spindle shaped thick walled macroconidia

48
Q

Microsporum gypseum

A

– Geophilic
– Natural soil saprophyte
– Infects a wide range of animals and man
– Lesions highly inflammatory
– Colony appearance
– Powdery cinnamon surface
– The reverse surface may or may not be
pigmented
– Microscopic features
– Thin walled symmetrical spindle shape
macroconidia

49
Q

Trichophyton equinum

A

– Zoophilic
– Horses
– Very rarely in humans
– Young horses most susceptible
– < 4 years old
– Most cases occur particularly in humid weather during autumn and winter
– Affected animals must be isolated
– Contaminated harness and grooming gears
disinfected
– Bleach (0.5% sodium hypochlorite)
– Colony appearance
– White, cottony with a yellow edge
– Reverse is yellow to red-brown
– Microscopic features
– Macroconidia rare
– Microconidia spherical to pyriform (pear-shape)

50
Q

Trichophyton verrucosum

A

– Zoophilic
– Cattle
– Can infect humans
– Can survive for many years in farm buildings
– May grow on semi-dried faecal
material
– Calves most susceptible
- Lesions around the face and eyes
– Most cases occur in the winter
– Groups of animal affected
– Contagious
– Usually, self-limiting
– Topical treatment
– Colony appearance
– Deeply folded, white to brilliant yellow
– Grow slowly requires thiamine and inositol
– Microscopic features
– Macroconidia rare
– Microconidia ovoid to pyriform (pear-shape)

51
Q

Mycotoxicoses

A

– Mycotoxins
– Low molecular weight, non-antigenic substance ,
many are heat-stable
– Formed on feeds following growth of fungi
under favourable temperature and moisture
– Exposure by ingestion (mostly)
– Toxins are secondary metabolites
– Formed during the stationary phase of culture
– Growth may occur on crops or in poorly
stored feed
– Pigs, dairy and feedlot cattle
– Optimum conditions for toxin production
vary between species
– Varying host susceptibility with age

– Disease manifestation
– Acute disease with overt signs
– Chronic with reduced growth rate or
reproductive efficiency
– Increase susceptibility to other disease
– Diagnosis can be difficult
– Absence of specific signs in chronic disease
– Uneven distribution of toxin in feed
– Instability of some toxins and lack of detection
methods
– Fusarium graminearum
– Aspergillus flavus
– Perennial rye grass staggers
– Claviceps spp.
– Pithomyces chartarum

52
Q

Aspergillus flavus

A
  • produce extremely toxic aflatoxins, the most toxic
    being aflatoxin B1
    – A. flavus is ubiquitous and can grow and
    produce toxin on most solid foodstuffs
    – Considerable variation in species susceptibility
    to toxin
    – Humans cause of food poisoning
    – Outbreaks occur particularly in warm moist
    conditions

– The toxins inhibit RNA and protein synthesis and cause hepatic centrilobular necrosis and fatty infiltration
– Acute disease may cause sudden death, or there may be less acute forms with haemorrhage, jaundice and anorexia
– Chronic disease may cause reduced feed conversion and enhanced susceptibility to concurrent disease.
– Intoxication of sows may cause abortion with few other signs
– Aflatoxins are highly carcinogenic
– Control and prevention
– Minimise storage time (time from harvesting
to feeding)
– Monitor feed
– Ammonia gas to detoxify contaminated feed
– Dilute infested feed to reduce concentration
(no longer acceptable in EU)

53
Q

Aflatoxin detection

A

– Feed and tissue
– Thin-layer chromatograpy
* Examined under UV
* B1 and B2 is blue
– High performance liquid chromatography
– Immunoassay
– Biological assay
* Ducklings
* Chicken embryos
* Shrimp larvae
* Trout embryos

54
Q

Conditions for encystment

A
  • loss of food source
  • dessication
  • increase in tonicity (salts)
  • change in O2 concentration
  • change in pH
  • temperature change
  • or terminal stage of a life cycle (ie. oocyst coccidia)
55
Q

Isospora suis (Cystoisospora suis)

A

neonatal porcine coccidiosis
* pale, watery diarrhoea
* decreased growth
* 5-15 day old piglets
* high morbidity & low mortality

56
Q

WHat does Neospora caninum do to which animal

A

Abortion in cows
* no clinical signs in cows that abort
* mostly in the second trimester of pregnancy
* autolysis but no gross pathological lesions
* seropositive congenitally infected heifers have a 7.4 times
increased risk of abortion in their first pregnancy

57
Q

Toxoplasmosis

A

Brain cyst

Epidemiology
* domestic and wild cats main transmitters
* oocysts in cat faeces most likely source (children)
* raw or undercooked meat (adults)

  • causes abortion in sheep
    death in kangaroos
    Multiple births in cattle
58
Q

What are nematodes?

A

roundworms

59
Q

How do nematodes infect?

A

Feacal oral injection

60
Q

Trichostrongyloid nematodes (genrea of importance)

A

HOT
*Haemonchus (“Barber’s pole”)
*Ostertagia (“small brown stomach
worm”)
*Trichostrongylus (“black scour
worm”)

61
Q

Trichostrongylid nematodes-
general features of parasitism

A

Ill thrift- poor condition, lethargy
Scouring- poor condition, fly strike
Anaemia- pale mm, bottle jaw,
lethargy
Basically DAD: Diarrhoea, Anaemia & Death

62
Q

Trichostrongylid nematodes- host factors

A
  • Age (young and lactating most susceptible)
  • Nutrition (protein enhances immunity)
  • Stress
  • PPR (around birth and lactation)
  • Resistance due to the immune response (IR)
  • Resilience – the ability to produce under parasitism
63
Q

What are trematodes?

A

Flukes

64
Q

WHat are cestodes

A

Tapeworms

65
Q

Where do trematodes live

A

water

66
Q

Where do cestodes live

A

prey intermediate host
exploite predator prey relationship

67
Q

Where do nematodes live?

A

grass and soil

68
Q

Other features of Trematodes

A
  1. Associated with
    water
  2. Indirect life cycles –
    snails as IH;
  3. Many have wide host
    range (F.hepatica)
  4. Most persist for
    years in the host so…
  5. Cause chronic
    disease
69
Q

What causes bottle jaw?

A

Liver fluke

70
Q

Diagnosis and control of
Trematodes (flukes)

A
  • Signs are weakness, pale mucous membranes due to
    anaemia (blood loss) and often jaundice (yellowing)
  • Drenching (TCBz)
  • Non-chemical control (pipe
    water and keep
    dams/creeks fenced)
  • Vaccination (exptn)
  • Selective breeding (n’yet)
  • Biological control (of IH?)
71
Q

Cestode life cycle

A

From rabbit to dog when dog eats rabbit
Rabbit gets it from faecal eggs shead on ground

AVBS3001 (5 decks)

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