Canine Endoparasites

Canine Endoparasites

1. GIT Nematodes

   • Hook worms
     • Ancylostoma caninum
       • Life cycle
         • L3 ingested and migrate through lungs to tissues, or L3 penetrate skin and migrate. Feed in SI on blood, an caue haemorrhage from feeding sites (x6/d). Arrest in muscle until late pregnancy where migrate to mammary glands and infect pups via milk
         • PPP 14-21d
         • Dogs
       • Young dogs: severe acute haemorrhagic anaemia and haemorrhagic D+. Immunity is acquired so older animals get more chronic anaemia
         • Tx: BZ + ivermectin q3m, or fenbendazole in pregnant bitch
           • Vax: Ab to nematode gut wall = starvation, reduced egg shedding and fewer CS
           • dirt and grass support growth
         • Dx: eggs non-diagnostic, must hatch in lab and ID based on morphology - buccal teeth
       • ZOONOTIC
     • Uncinaria stenocephala
       • Northern Hookworm
         • Endemic in UK
       • Life cycle
         • Oral infection of sheathed L3 (cutaneous L3 migration unsuccessful - pedal dermatitis), no ALD or transmammary infection. Can cause a PLE from SI damage, but doesn't cause anaemia.
           • Dx: Faecal eggs similar to A caninum but bigger (70-80um) and adult has cutting plates not buccal teeth
         • Dogs,cats, foxes
   • Whipworms
     • Trichuris vulpis
       • T suis (pig), T trichuria (man)
       • Life cycle
         • Adults found in large intestine, 7cm long, release eggs into faeces. L1 develops in eggs which are long lived in environment. Ingestion of L1 in egg = digestion of egg shell plugs, L1 penetrates mucosal glands where it develops to L4 and adult.
           • Dx: faecal eggs have bipolar plugs
           • Tx: BZ, ProBZ, or ivermectin
             • Dry, clean bedding, earth runs, Clean kennel by disinfectant, heat or steam
         • PPP 6-12w
   • Toxocara canis
     • Routes of infection
       • Oral - L3 ingestion, Transplacental, Transmammary, Paratenic host
     • Outcome of infection
       • <3 months old: adults develop in SI, eggs produced
       • 3-6m - larvae tend to arrest in tissues, no adult. ALD
         • Reactivation ~3w prior to parturition in the bitch meaning 100% of puppies are infected at birth. Transmammary transmission for ~5w. Highest burden in pups <6m. Most worms expelled by 6-8m from SI, but arrested stages persist
     • Treatment
       • Treat puppies at 2w old to stop patent adults. Treat again at 5w to remove infection acquired from milk
         • Treat dam too: 3w pre-partum + 2d post partum
       • Fenbendazole 5d
   • Toxocara leonina
     • Ingestion of larvated L3 directly or via paratenic host

2. Anthelmintics

   • Benzimidazoles
     • Nematodes, Cestodes, Trematodes
     • White drench = suspension
       • Short acting, stays in GIT,
     • Binds tubulin
   • Macrocyclic Lactones
     • Nematodes and arthropods
     • chloride channels opened = flaccid paralysis of pharyngeal pumps
     • long acting, lipid soluble, high Vd
     • Ivermectin
       • Not safe for collies
     • Selamectin
       • Safe for all dogs over 6w
     • Miblemycin
       • oral, chewable, 95% stays in GIT
   • Pyrantel
     • adult nematodes and tapeworms
     • poorly distributed from GIT
     • Nicotinic ACh receptor to cause paralysis
   • Praziquantel
     • Cestodes and trematodes
       • Embedded larval stages
   • Cyclooctadepsipeptides
     • nematodes
       • formulated with praziquantel
       • pre-synaptic inhibition of ACh NT release

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