PID 1 Flashcards
introduction to parasites
definition parasitism
non-mutual symbiosis where one species (parasite) lives at the expense of the other (host) causing damage
mechanical damage example
Ascaris suum in pigs –> occlusion of the intestines
traumatic damage example
hookworms attach in epithelium with buccal capsule
inoculation of pathogens example
ticks
malabsorption example
protozoan Gardia –> increase intestinal permeability
definitive host definition
where sexual stages of parasites develop
practical definition of definitive hosts
vertebrate
intermediate host
where parasite evolves into a further stage of development
terminal host
intermediate host that doesn’t allow transmission
paratenic host
where parasite is simply carried
biological versus mechanical vectors
biological plays a role in lifecyle whereas mechanical only carries parasite passively
direct lifecycle
when it is completed in a single host
definition of helminths
worms
categories of helminths
plathelminths (flatworms= trematoda + cestoda) and nematoda (=roundworms)
trematoda definition
bi-laterally symmetrical, leaf-like, no body cavity
cestoda
elongated, segmented as adults, no body cavity
nematoda
circular in cross-section, body cavity
basic morphology of nematodes
body covered with cuticle, body cavity ‘tube within a tube’ is pseudocoelom, mouth sometimes opens into a buccal capsule
forms of oesophagus of nematodes
filariform = bursate nematodes / bulb-shaped = ascaridoids/ double-bulb shaped = oxyuroids / muscular-glandular /trichuroid= capilary form of signle column of cells/ rhabditiform ) anterior and posterior swelling
nematodes: difference of intestine between females and males
females= terminates in an anus, in males terminates into a cloaca where vas deferens opens
definition spicules
accessory male organs, inserted in the female genital opening during copulation, guide the sperm, important for identification
copulatory bursa
embraces female during copulation, supported by bursal rays
basic life cycle of nematodes
larval stages L1/L2/L3 are infectlive stages, L4 and L5 which is the immature adult
direct life cycle in nematodes
female lays eggs –> excreted –> L1 –> L2/L3 –> new host eats L3 (except in hookworms that penetrate skin or ascarids that develop into larvae after being ingested)
indirect lifecyles of nematodes
L1/L2 in intermediate host –> infection of final host by ingestion of intermediate host or inoculation of L3s
what is the pre-patent period (PPP)
the time elapsed between infection and detectable evidence of the parasite (eg: detection of eggs/cysts in the faeces)
optimum temperature for development of maximum number of larvae of nematodes
18-26°C
optimal humidity for larval development
100%, but microclimate in the faeces or in soil may provide sufficient humidity
hypobiosis
seasonal arrested development
preparturient rise (PPR) in faecal egg counts
increase in nematode eggs in the faeces around parturition, more marked in ewes, sows and goats
trematoda (flukes) morphology
muscular suckers, tegument covered with spines, no body cavity,
trematoda sexual organs
hermaphrodites –> cross or self-fertilisation
basic life cycle of trematoda
see picture
cestoda (tapeworms) basic morphology
head/scolex with 4 suckers with hooks –> short unsegmented neck –> chain of segments = strobila each segment being a proglottid
sexuality of proglottids
hermaphrodites
