Parasitology B Flashcards
What stage of ascaradids is passed in the faeces? How long does it take for them to become infective in the soil? How long can they survive in the soil?
Unembryonated eggs
2-3 weeks to become embryonated and infective
Last for years (5-10) in soil
What type of toxocara canis lifecycle does not involve tracheal migration?
How long is the PPP for different types of lifecycle with this species?
Transmammary (2-3 weeks)
Transplacentally (2 weeks)
Eggs ingested by pup (4-5 weeks)
What diseases are of particular public health significance with respect to ascarids?
Visceral larva migrans
Ocular larva migrans
What are some characteristic features of enoplids? What worms are included in this order?
Non-muscular oesophagus with stichosome.
male either has a single ensheathed spicule or none (trichinella).
1. Trichinella
2. Trichuris (whipworm)
3. Capillaria (hairworm)
4. Acanthocephalans (thorny-headed worms)
Briefly describe the lifecycle and significance of trichinella
Adult worms occur in SI. Female worms penetrate deep into mucosal glands -> lymphatics-> blood-> skeletal muscle. Ingested through meat-eating.
Significance: causes trichinellosis through ingestion of raw or undercooked infected meat, especially pigs.
What are the differences between the two groups of Trichinella sp.
- Encapsulated species- found in mammals only. The L1 is surrounded by a collagen capsule (“nurse cell”) within muscle.
- Unencapsulated species- in mammals, birds, reptiles and marsupials. L1 is freeeeeee!
Which trichonella species is present in Aust?
Trichonella pseudospiralis
What are some clinical signs of trichinellosis?
In animals there are none. in humans, the severity of clinical signs is proportional to the dose ingested.
In peracute infections- diarrhoea, abdominal pain, vomiting, fever.
in acute infections, eosinophilia, elevated CK, myalgia, fever, vasculitis, cardiac problems and death
How do you diagnose trichonellosis and how may it be treated? How may it be controlled?
Dx: serology
Tx: corticosteroids and albendazole
Control: prevent raoming/ scavenging of pigs, proper meat prep (microwave, salting and smoking are all ineffective)
Which trichuris species affect the following animals:
- Primates
- Dogs
- Pigs
- Primates- T. trichiura
- Dogs- T. vulpis
- Pigs- T. suis
What clinical signs might one see with trichuris infections? How might these be diagnosed and treated?
CS: congestion, submuc oedema, epithelial desquamation, necrosis/ fibrosis, watery/mucoid diarrhoea, tenesmus, rectal prolapse, hypoproteinaemia/ hyperkalaemia (colitis causes loss of Na and K)
Dx: Faecal float (SG>1.2)
Tx: Oxantel, MLs (not selamectin though) or BZs
Which capillaria are of concern in poultry and where do they occur? What do they cause?
C. annulata (crop)
C. contortus (crop)
C. caudinflata (SI)
C. obstignata (SI)
CS: Light infections-> poor weight gain, decreased egg prod.
Heavy infections: catarrhal thickening, infl. of oesophagus and crop and enteritis. High mortality
Tx: ivermectin, BZs, levamisole
Which worms have no digestive tracts?
Acanthocephalans (thorny-headed worms)
What is the IH of acanthocephalans? What are some examples of this species of worm?
Arthropods Macracanthorhynchus hirudinaceus (piggies) Onicola sp. (dogs and cats)
Briefly describe the general lifecycle of Ascarids.
DIrect lifecycle. Eggs are passed unembryonated in the faeces, they take 2-3 weeks to embryonate. Paratenic host may then ingest the L3 stage. Definitive host may ingest infected paratenic host or may ingest L3 egg. Larvae undergo hepatopulmonary migration before being coughed up and swallowed. Adults in small intestine.
What are the effects of ascarids in pigs?
HPM causes mechanical and infl. damage to organs. Milk spots. Eosinophilic pneumonia
What stage of ascarid is found in muscle and passed though milk?
L3
How can you tell the difference between toxocara canis and toxascaris leonina?
T. canis has a ventriculus and a digitiform tip on its posterior end (in males)
How long is the prepatent period for T. leonina
7-9 weeks
What are some important ascarids of birds? What is their predilection site? What are their effects?
Ascaridia galli (SI)- Usually not a big deal but can cause haemorrhagic enteritis or intestinal occlusion and nutritional deficiency.
Heterakis gallinarum (caecum)- may cause caecal thickening but of liitle pathological sig. Phoresy.
What is phoresy? Give an example
An association between two organisms. The transmission of ameboid, histomonas meleagradis, occurs through the egg of Heterakis gallinarum.
Why is Phoresy a problem in Heterakis gallinarum?
The protozoa histomonas meleagradis is not pathogenic to chickens but is extremely pathogenic to turkeys causing necrotizing typhlitis and focal liver necrosis
What are some treatment and management options for ascarids?
- Hygiene, decontamination of property (flame gun, Na hypochlorite).
- Disinfect? Often resistant to bleach
- Rodent and pest control
- Don’t feed raw meat
- Treat and quarantine new arrivals
- deworm regularly
- Reduce environmental contamination (pick up poo daily)
- Anthelmintics (MLs, morantel, benzimidazoles)
- Rotate pastures (horses)
Propose a treatment regime to control ascaris suum in pigs.
Drugs: levamisole, ivermectin, morantel, piperazine or fenbendazole (in feed)
Treat growers at 8 weeeks old (bc that the PPP of A. suum)
Treat sows and boars every three months (to reduce pasture cont)
Treat sows 7-14 days prior to farrowing
Test herd every 6 months
Propose a treatment regime to control parascaris equorum in horses.
Deworm foals every 2 months for the first year of its life with rotations of MLs, BZs and pyrantel. Start this at 2 months of age.
Rotate pastires for mares and foals annually
Do a FEC prior to deworming adults in spring and autumn (want to test before you treat in adults to reduce resistance)
Propose a treatment regime to control Toxocara canis in dogs.
Deworm puppies first at 2wo (3wo for kittens) then fortnightly until 10wo (8 wo for kittens), then monthly until 6 months old.
Deworm the bitch at the same time
During pregnancy: fenbendazole 50mg/kg daily from day 40 to 14 days post whelping (larvacidal) OR selamectin topically at day 40 and day 55 PLUS monthly moxidectin (This is for bitches not queens. For queens apply selamectin topically at the end of gestation)
What is anasakiasis?
Illness caused by ingestion of L3 anisakidae in raw or uncooked fish.
Where do oxyurids (“pinworms”) occur?
Caecum, colon and rectum
What are some features of spirurids?
- Two lateral lips (or none)
- Unequal spicules
- Arthropod IH
- Oesophagus with anterior muscular and posterior glandular secretions
What is the difference between Draschia sp. and Habronema sp?
Habronema causes ulcers/ gastritis and draschia causes nodules in stomach wall
What is the IH for Draschia? What about Habronema? how can you tell the difference between these worms?
Draschia megastoma= Musca spp.
Habronema microstoma= stomoxys calcitrans
Draschia has a cephalic constriction and a big funnel shaped buccal capsule (cff cylindrical)
What is important to remember if you want to do a faecal floatation of equine spirurids?
Floatation solution needs to have a SG>1.2
How can spirurids of horses be treated/controlled?
- Adults can be targeted with OXFENDAZOLE or MOXIDECTIN.
- For cutaneous lesions: MLs (eg. Ivermectin) +/- surgical debridement, cryotherapy, CSs
- Fly control (get rid of manure, insect growth regulators)
- Face and eye masks, fans etc.
Where is spirocerca lupi common? How might it be diagnosed?
Tropical/ subtropical regions globally
Eggs may not be present in faeces. Therefore, endoscopy or radiography
How might spirocerca lupi be managed/ treated?
Difficult because adults are protected in granulomas
- Moxi (prophylactically)
- Surgical removal where feasible
- Aid feeding (upright position)
- Prevent free-roaming/ scavenging
- Tx= off label use of doramectin, moxi and milbemycin for up to 6 months
Which parasite has a characteristic uni-plugged eggs on faecal floatation>
Gnathostoma spp
How does gnathostomiasis occur in humans?
Fish borne zoonosis
What is the IH for Ascarops strongylina/ physocephalus sexalatus in pigs?
Dung beetle
What does thelezia cause?
Keratitis, ulceration and opacity of eye
What are some spirurids in birds and where do they occur?
Gongylonema spp. - crop, IH= cockroach
Acuaria spp. and Tetrameres spp. - proventriculus/ ventriculus. IH=grasshoppers and beetles
Oxyspirura mansoni- conjunctival sac. IH= cockroach
Where are adult filaroids located?
Blood and lymph (NOT GIT)
Where is Onchocerca cervicalis found (what animal and where in animal)? What does it cause?
What about Onchocerca reticulata?
Horses nuchal ligament-> oedema, chronic granulomatous nodules and fibrosis
Horse flexor tendons
What is Queensland itch?
Onchocerciasis in horses. Mff dying in dermal tissue causes pruritic dermatitis on the ventral midline, face, neck, chest, withers, forelegs and abdomen. Can also cause scales, crusts, ulcerations, alopecia and depigmentation. Treat with Ivermectin or moxi. Permethrin pour on can be used by way of prevention.
What are the filaroidea of cattle and where do they occur?
O. gutturosa (Nuchal ligament)
O gibsoni (dermal tissue of brisket)
O. lienalis (gastrosplenic ligament)
Stephanofilaria stilesi (ventral thorax and abdomen)
What is the vector for Stefanofilaria stilesi? How may this be controlled?
Haematobia irritans
Control is difficult. No anthelmintic is effective against adults.
-Walk through fly traps
-Dung beetle
-Synthetic pyrethroids or OPs (pour-on, ear tags, dips)
What is the pathogenesis of heartworm?
Presence of worm and its endosymbyont (wolbachia) -> proliferative endarteritis of pulmonary arteries.
This leads to decreased arterial compliance plus thrombosis and thromboembolism (esp. from dead parasites) -> pulmonary hypertension -> increased afterload for RV -> RV hypertrophy and dilation -> RSCHF +/- caval syndrome
How may heartworm be diagnosed?
Hx, CSs, detection of mff in blood (Knotts test and filtration method), SNAP ELISA antigen test (need at least 3 females though)
Up to 30% of heartworm infections may be occult. Why is that?
All worms may be same sex
May have a single worm infection
May have a pre-patent infection or geriatric worms
May have ectopic infections
May have drug induced/ immunologically mediated elimination
What is the “soft kill” regimen for heartworm treatment?
ML + Doxycycline (10 mg/kg, 1 month on, 2 months off) over 9-12 months
How does heartworm differ in cats from dogs? WHat are some clinical signs of it in cats? How is it treated? How is it diagnosed?
Prevalence is 5-20% of that in dogs Most worms don't mature PPP=8 months (cff. 3) Often no mff Shortened adult survival time Aberrant migration
CS: Heartworm associated resp disease (HARD)
Tx: Prednisolone or surgery. NO MELARSAMINE
Dx is challenging. Can do Ab test (at 8 weeks post infection), Ag test if more than 1 female, radiographic changes (bronchioalveolar pattern, enlargement of caudal lobar arteries, adults on ultrasound)
What are some radiographic signs of HARD?
bronchialveolar patter
slight enlargement of caudal lobar arteries
adult worm on ultrasound
How might heartworm in dogs be treated?
- Day 0: start pred (0.5 mg/kg) every altenate day before and up to 1 month starting adulticide treatment.
- MLs from day 0 to prevent new infections. Monthly.
- Doxy (10mg/kg) from day 0 to target walbachia (1 month)
- Melarsamine from day 60. 1 injection followed by 2 injections one month later given 24hrs apart
- Retest 6 month
- Restrict exercise
Which three classes of platyhelminths are trematodes?
Monogenea (marine and freshwater)
Digenea (vertebrates)
Aspidogastrea (marine or freshwater)
What are some distinguishing features of platyhelminths?
- flattened
- tegument instead of cuticle
- tribloblastic and acoelomate
- hermaphroditic
- flame cells
What are flame cells?
Cells in trematodes responsible for osmoregulation (primitive kidneys)
What is the mechanism of reproduction in hermaphroditic trematodes?
Sperm stored in testes travels to seminal receptacle. The oocyteis released from the ovary and travels up oviduct to be fertilised. Fertilised egg is nurtured in ootype where shell formation takes place as a result of vitelline material and Mehlis gland. Egg shrinks in size as it passes down the uterus and is released from genital pore.
What is the general lifecycle of digenean trematodes?
eggs-> miracidium-> rediae-> cercariae-> metacercariae-> ingested (note, with schistosomes, the cercariae are ingested directly after being released form the snail).
What is a miracidium?
The first larval stage of trematodes with an aquatic lifecycle. They have a ciliated epithelium and respond to 5 factors:
- negative geotaxis
- water salinity
- light intensity
- temperature
- chemotaxis
What is a sporocyst?
The asexual reproductive stage of trematodes that occurs in the snail. Stage is between miracidium and rediae.
What is a cercariae?
Actively motile larvae of flukes which escape from the snail. They swim tail first
What are metacercariae?
Final stage larvae of flukes which encyst on vegetation and modify host behaviour when eaten.
What snail is the intermediate host of Fasciola flukes? What are some characteristics of this snail?
Lymnae snails
Clockwise spiral, flat/ triangular tentacles
What is the difference between the acute and chronic forms of fascioliasis. Include things in your comparison such as timeframe, animal affected etc.
ACUTE: 4-6 weeks. Large numbers of 5-6 week old juvenile flukes. Flukes go through intestinal wall to peritoneal cavity and liver. Seen in sheep more than cattle. Can lead to black disease and acute toxaemia.
CHRONIC; more than 6 weeks. Involves adult flukes which establish in bile ducts and cause fibrosis and hypertrophy. May see calcification of parasite. Seen in Cattle more than sheep. May cause bottle jaw.
When and how does acute fascioliasis occur? What are some DDx?
Massive intake of metacercariae over short time. Usually in spring-> clostridium novyi
DDx: other clostridials, toxins (pasture), anthrax
What are some DDx for chronic fascioliasis?
Hypoproteinaemia Protein-losing enteropathy Haemonchus Johne's Strongyles
What diagnostic technique would you use for fascioliasis?
Necropsy or Serology.
Not faecal float because it has a long PPP (unless its a chronic infection)
What are the effects of fascioliasis that lead to production losses?
Reduced production Decreased wool and milk quantity/quality Low lambing rates Poor growth and feed conversion Sudden death 10 million in drenching Total of 60-80 million loss
Liver flukes are found in all australian states except…?
WA and NT
When are different stages of the lifecycle of Fasciola hepatica seen in Victoria? With this in mind, when would you treat and with what?
Eggs hatch mid-sept.
2 months later- cercariae
5-6 weeks later- acute infection in sheep
Chronic fluke disease seen in winter
Tx:
- Late Dec/Jan- triclabendazole (kills juvs)
- Going into Autumn (April/ May)- adulticide (eg. Closnatel + oxfendazole)
- Aug/Sept- adulticide to reduce pasture contamination and remove fluke carrying over from late autumn and winter
How might Fasciola hepatica be controlled within a herd/mob?
- Keep sheep away from water source
- fence off snail-prone areas
- drain marshy pastures
- build dams - Strategic flukicide treatment
- 5-in-1 vaccines
What s fasciola buski?
Giant intestinal fluke. Pigs act as reservoirs for human infection
Are fasciola eggs passed embryonated or not?
Not. takes 2-3 weeks to embryonate
What is the intermediate host for paramphistomatidae flukes?
Planorbid snail (Gyraulus sp. or Helicorbis sp.)