Parasitology Flashcards
Parasite definition
Dependance on another for food and shelter
Endo vs Ecto parasites
Endo (inside)
- protozoa
- worms
Ecto (outside)
- insects
- arthropods
Cestodes cause problems for which host?
intermediate
What are the 5 types of hosts?
- 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)
What are parasite factors?
Dose
Virulence (ability to cause damage)
infectivity
What are host factors?
Innate resistance (genetic ususally)
previous exposure
passive immune status (neonates)
age
Reproductive status (preg, lactating vs non preg, sterile vs intact)
What are environmental factors?
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)
Host factors affecting parasitism?
age
exposure
amount of parasites
genetics
periods of stress
preg/lactating
management factors
Definitive host
parasite reaches sexual maturity and undergoes repro in this host
Reservoir host
non human definitive host which maintains parasite for possible human infection
Endoparasite
inside
protozoa
worms
Ectoparasite
outside
insects
arthropods
How is pathology produced?
production of something toxic or foreign material excereted
migration through tissues
host reaction (allergies/inflammation)
Host specific parasites
Narrow host range
well adapted
niche relation
Non host specific parasites
broad host range
possibility of paratenic hosts (resoivoirs)
zoonotic possibility
Arthropod
joined limbs
hard exoskeleton
head, thorax and abdomen
90% of all species on planet
Ectoparasite path
direct trauma
removal of metabolites and blood
allergic irritaion and dermititis
interference with functioin or behaviour
Ectoparasite vectors
Mozzies
Tsetse fly
Bufflo fly
Blackflies
Midges, snadflies
fleas
ticks (arachnid)
Types of vectors
Mechanical (infection directly to host –> not essential for lifecycle)
Biological (undergo development or multiply (essentail for life cycle
WHat are the HOT rumunanet nematodes
H barbers pole
O small brown stomach worm
T Black scour worm
What are the general features of parasitism (DAD)
Diarrhoea
Anaemia
Death
Conditions for encystment
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)
4 major protozoa groups
Amoebas
Flagellates
Cilliates
Sporozoa
How is malaria transmitted
Sporozoited injected with saliva
enter circulation
trapped in liver (recpetor ligand)
Which malaria is the worst and why?
Falciparum (constant high fevers that barely come down)
What is a pellicle
combination of plasma membrane and thin,
translucent, secreted envelope
IN FLAGELLETE
Tritrichomonas foetus causes what in cows
infertility
abortion up to 5 motnhs after breeding
What is the gold standard?
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
Water borne disease
Cryptosporidiosis caused by Cryptosporidium spp.
feacal oral
diarrheoa
NO TREATMENT
Food borne disease
Trichinellosis (trichinosis) caused by Trichinella spp.
through meat (worms)
reproduce in body and babies go into muscles
Pigs intermediate host
What are examples of secondary tests
Oxidase
Catalase
O/F (Oxidative/fermentation
What are examples of tertiary tests
Acetoin
CAMP
Carb fermentation
Clumping
Enteropluri
lactose fermentation
motility
Oxi/ferm
sorbitol
sucrose
urea
trehalose
How would you best control strangles
Quarantiine
What is an obligate parasite?
a parasite that depends on a host for nourishment, repro, habitat and survival. Can’t survive away from host.
What is a saprophyte
An organsim that gets its nourishment from dead or decaying organisms
Fungi
Give an example of an obligate parasite
Flea, tick, louse, blood fluke, takeworm etc.
Classes of Mycoses
– Opportunistic mycoses
– Dermatophytes
– Systemic mycoses
– Mycotoxicoses
Opportunistic mycoses
saprophytes
mucosal commensals
Chronic lesions (reponse resembles that to foreign bodies)
Aspergillus
Opportunistic mycoses
Ubiquitous saprophytic moulds
Cause respitory disease
Outbreaks occur when large numbers of conidia are inhaled or penerate eggs
Aspergillus fumigatus
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
Cryptococcus neoformans
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
Dermatophytes
Fungi associated with the skin
- Microsporum
* M. canis → carnivores (cats and dogs)
* M. gypseum → horses
- Trichophyton
* T. equinum → horses
* T. verrucosum → cattle
Classification of Dermatophytes
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
Dermatophyte pathogenesis
– 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
Dermatophytes Diagnosis
– Microscopy examination of skin scrapings
– Culture
– Sabouraud agar
– Dermatophyte Test Medium
Dermatophytes: Treatment, prevention and control
– 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 !!
Microsporum canis
– 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
Microsporum gypseum
– 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
Trichophyton equinum
– 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)
Trichophyton verrucosum
– 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)
Mycotoxicoses
– 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
Aspergillus flavus
- 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)
Aflatoxin detection
– 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
Conditions for encystment
- 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)
Isospora suis (Cystoisospora suis)
neonatal porcine coccidiosis
* pale, watery diarrhoea
* decreased growth
* 5-15 day old piglets
* high morbidity & low mortality
WHat does Neospora caninum do to which animal
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
Toxoplasmosis
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
What are nematodes?
roundworms
How do nematodes infect?
Feacal oral injection
Trichostrongyloid nematodes (genrea of importance)
HOT
*Haemonchus (“Barber’s pole”)
*Ostertagia (“small brown stomach
worm”)
*Trichostrongylus (“black scour
worm”)
Trichostrongylid nematodes-
general features of parasitism
Ill thrift- poor condition, lethargy
Scouring- poor condition, fly strike
Anaemia- pale mm, bottle jaw,
lethargy
Basically DAD: Diarrhoea, Anaemia & Death
Trichostrongylid nematodes- host factors
- 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
What are trematodes?
Flukes
WHat are cestodes
Tapeworms
Where do trematodes live
water
Where do cestodes live
prey intermediate host
exploite predator prey relationship
Where do nematodes live?
grass and soil
Other features of Trematodes
- Associated with
water - Indirect life cycles –
snails as IH; - Many have wide host
range (F.hepatica) - Most persist for
years in the host so… - Cause chronic
disease
What causes bottle jaw?
Liver fluke
Diagnosis and control of
Trematodes (flukes)
- 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?)
Cestode life cycle
From rabbit to dog when dog eats rabbit
Rabbit gets it from faecal eggs shead on ground
