Equine Parasites & Parasite-Associated Disease Flashcards
what are the nematodes in horses (5)
- parascaris equorum
- small and large strongyles
- strongyloides westeri
- oxyuris equi
- dictyocaulus arnfieldi
what are the cestodes
- anoplocephala perfoliata
what are the arthopods
gastrerophilus
what is the lifecycle of nematodes
- adult parasites produce eggs or L1 in host
- eggs hatch L1 and
- moult to L2
- L3
- L4 ingested
which is the largest nematode
parascaris equorum
where do parascaris equorum reside in
small intestine
what age do parascaris equorum affect
foals, weanlings and yearlings
adults develop acquired immunity
how is parascaris equorum diagnosed
distinctive eggs in feces
what is the prepatent period of parascaris equorum
10 weeks
what is the parascaris equorum lifecycle (4)
- egg + L3 ingested
- hatching of L3 in the stomach and small intestine, penetration of intestinal veins
- larvae reach liver via portal vein, migration through liver tissue and penetration of liver veins
- larvae reach lung via vena cava and right heart, penetration into lung alveoles and migration via trachea and pharynx to small intestine (moulting to L4 and St5 prior to development into adults
what is the disease parascaris equorum in foal and weanlings
larvae can cause tissue damage during migration –> mirgrate through liver (areas of fibrosis)
2-4 weeks after infection migrate through lungs and cause cough
what disease does parascaris equorum cause in adult horses
cause ill thrift –> don’t attch to mucosa but compete for nutrients
can cause colic by luminal obstruction –> ascarid impaction, especially post deworming
how is parascaris equorum controlled (3)
- avoid using same paddocks for nursing mares and foals in successive years
- resistence to fenbendazole, ivermectin and pyrantel –> fenbendazole less resistance in UK vs ivermectin
- deworm from 1 month of age, treat every 4 weeks, until 6mo old
how is parascaris equorum treated (4)
- low bulk diet
- NGT with liquid paraffin (lubricate)
- treat with fenbendazole
- repeat FWEC 3 weeks after last dose
which has a faster mode of action between ivermectin, pyrantel and fenbendazole in killing parascaris equorum
ivermectin and pyrantel cause quicker worm death than fenbendazole
what is the dosing schedule in treating with fenbendazole in foals and weanlings
day 1: 2.5 mg/kg
day 4: 2.5 mg/kg
day 7-11: 10 mg/kg once daily for 5 days
what are the large strongyles (3)
- strongylus vulgaris
- strongylus edentatus
- strongylus equinus
where do adult strongylus vulgaris reside
in cecum and ventral colon attached to mucosa
how is strongylus vulgaris infection diagnosed
eggs easily detected in feces
what is the PPP of strongylus vulgaris
6-7 months
what anthelmintics are strongylus vulgaris sensitive to
macrocyclic lactone
what disease does strongylus vulgaris cause
associated with colic
what is the life cycle of strongylus vulgaris (10)
- parasitic phase: L3 taken up orally with grass, exsheathment in small intestine
- penetration into wall of large intestine
- moulting to L4
- migration on or in intima of arteries of large intestine
- migration to cranial mesenteric artery
- moulting to pre adult stage
- migration to intestine and peentration of intestinal wall to enter lumen where development to adults is complete
- free living phase: thin shelled eggs expelled with feces
- development to L1 within the egg
- moulting to L2
- infective stage L3
how do s. vulgaris develop in the horse
- L3 penetrate the intestinal wall and moult to L4
- migration of L4 into the cranial mesenteric artery
- moulting to St5 from 90th day post ingestion
- backwards migration from arteries to the gut
how does strongylus vulgaris cause disease
migration through mesenteric artieries leads to thrombosis, infarctions and necrosis of the intestine
non-strangulating infarction
surgical colic
how is strongylus vulgaris controlled
sensitive to anthelmintics
but possible increased prevelance due to selective deworming strategies
what are the small strongyles
cyathostomins
where do cyathostomins reside
cecum and large colon
what is the appearance of cyathostomins worms
<1.5cm long white to dark red
what do cyathostomins invade
mucosal lining
what do cyathostomins form once they invade the mucosal lining
encysted larvae
what is the life cycle of cyathostomins (7)
- eggs shed into feces –> L1, L2, L3
- oral uptake of L3
- exsheathment through gastric fluids
- passage of exsheathed L3 through small intestine
- invasion of mucosa/submucosa of colon and cecum
- moult to L4
- return to intestinal lumen and final moult before development to adult stage
where do the L3 of cyathostomins reside
ileum and travel to the cecum
where do L4 of cyathostomins reside
develop from L3 in the cecum and travel to the ventral colon
what disease do larval cyathostomins cause
sudden onset diarrhea in late winter/spring
synchronous emergence of L4 from mucosa (potentially large #s)
life threatening colitis/diarrhea
at what age is colitis/diarrhea especially common from cyathostomins
< 5 years old
how is cyathostomins disease treated (4)
- replace lost fluid and protein (enteral or IV fluids, plasma transfusion/synthetic colloids)
- anti-inflamamtories (corticosteroids?)
- deworming (moxidectin vs fenbendazole)
- supportive care and nursing
how is cyathostomins controlled (2)
- encysted larval burden NOT detected by FWEC
- limited # of anthelmintics active against encysted larvae (treat in winter) –> moxidectin or fenbendazole (wide spread resistance)
what does strongyloides westeri affect
sucking foals
what is the PPP of strongyloides westeri
8-14 days
how is strongyloides westeri transmitted
arrested larvae in dam abdominal wall mobilized and excreted in milk
foals infected immediately after birth
what does strongyloides westeri cause
diarrhea in foals
how is strongyloides westeri controlled
deworm dam
- moxidectin 4 weeks before parturition
- ivermectin around time of foaling
what is the life cycle of strongyloides westeri
- ingestion of food
- free living L3 embed in ventral tissues of mare then called parasitic L3 which pass in milk to foal
- parasitic L3 develop to adults in foals
- two molts: L3 to L4 to L5
- adult females in small intestine of foal
- embryonated eggs (L1 inside) pass in foals feces
- L1 hatch
what is oxyuris equi also called
pinworm
where do adult worms of oxyuris equi reside
in lumen of colon
where do oxyuris equi migrate to
gravid female mirgrates to anus, extrude anterior and lays her eggs in clumps
what is the PPP of oxyuris equi
5 months
what do oxyuris equi cause
irritation in perianal area –> tail rubbing
how is oxyuris equi diagnosed
tape strip
how is oxyuris equi controlled
difficult
scrub environment
washing perianal area can reduce itch
fenbendazole for 5 days or pyrantel
what are dictyocaulus arnfieldi
lungworms
what disease does dictyocaulus arnfieldi cause
patent infection in donkeys that rarely produce clinical signs
horses develop severe bronchial inflammatory response
how are horses infected with dictyocaulus arnfieldi
by co grazing with donkeys
how is dictyocaulus arnfieldi diagnosed
difiicult to diagnose
what are cestodes
tapeworms
what is the basic lifecycle of cestodes (tapeworms) (7)
- cysts ingested by final host
- adults in S.I
- gravid segments shed from worm and pass out in feces
- contain eggs which are resistent
- ingested by intermediate host
- embryo released from egg in IMH
- larva settles down and encysts
what is the most common cestode
anoplocephala perfoliata
where do anoplocephala perfoliata reside
in cecum
particularly adjacent to ileo-cecal junction
what is the intermediate host of anoplocephala perfoliata
forage mites (orbiatidae)
how is anoplocephala perfoliata diagnosed
eggs difficult to detect in feces
serum/saliva ELISA more sensitive
what disease is anoplocephala perfoliata assocaited with
colic
what is the life cycle of anoplocephala perfoliata (6)
- gravid proglotids filled with eggs are expelled with the feces
- eggs are released and taken up by box mites as IMH
- infective cysticercoids develop in IMH
- following oral uptake of infected mite with grass
- cystercircoids are released during digestion of the mite
- larvae attatch to intestinal mucosa and develop into adults
what type of colic does anoplocephala perfoliata cause (3)
- spasmodic colic
- ileal impactions
- intussusception of cecum and colon
how is anoplocephala perfoliata controlled (3)
- forage mites are widespread
- FWEC not helpful –> ELSA?
- pyrantel/praziquantel in spring and autumn, twice yearly if high ELISA, once yearly if low
what are trematodes
fasciola hepatica
but rare in horses
may cause liver disease
what are gasterophilus species (4)
- G. intestinalis: cardia of stomach
- G. nasalis: pylorus/duodenum
- G. hemorrhoidalis: rectum
- G. pecorum
what are gasterophilus
athropod: bot files gast
what are gasterophilus intestinalis transmitted
eggs laid on legs and hatch on contact with lips (grooming)
what diesease does gasterophilus intestinalis cause
not generally associated with disease just irritation from flies laying eggs
what is the disease that gasterophilus hemorrhoidalis/nasalis cause
attached to rectal mucosa and can cause rectal prolapse
summarize the intestinal parasites and where they reside
what parasite(s) resides in the cecum/ileocecal valves
a. perfoliata (tapeworm)
what parasite(s) resides in the small colon/rectum
o. equi
what parasite(s) resides in the stomach
G. intestinalis (bots)
what parasite(s) resides in the small intestine
- P. equorum - young hroses
- S. westeri - foals
what parasite(s) resides in the cecum/large colon
- large strongyles
- cyathostomins (small strongyles)
what should parasite control strategy combine (3)
- chemical (anthelmintic dosing)
- non-chemical (pasture hygeine)
- all horses from grazing group should share same regimen
how can pasture management reduce parasites
- regular removal of manure
- rotation grazing or mixed grazing with ruminants
- avoid high stocking density/young horses
how should deworming be done
based on FWEC of all animals 3-4x per year in grazing season
anthelmintic treatment for positive horses (>200 epg)
