March 11, 2014
• Host finding
o Active and passively.
Actively. Eg: hookworms. (Necator americanus, Ankylostoma spp)
• Taenia solium, Trichinella spp., Toxocara cati and
• Establishment within the host
o Eg: Trichinella adults are in the host’s intestines.
o Eg: Echinococcus multilocularis was found in a lot of coyotes in the
Calgary area. Humans get it by ingesting the eggs. Dogs get it by ingesting
the carcass of a rat or a vole.
o There are 5 million companion animals in Alberta. Soon, there will be
nearly 6 million companion animals. The huge number of animals increase
the potential for spread of zoonotic diseases.
o There is a lot more host specificity among helminthes than protozoa.
Helminths are way more host specific
We cannot become infected by adult Echinococcus. That is because
canid bile has different bile acids; the canidspecific bile acids are
necessary for the activation of oncospheres.
o Echinococcus adults are found in the junction between the duodenum and
the jejunum of the canid. Highly sight specific.
o Trichinella tends to hang out in the upper small intestine.
o E. granulosus ▯ hydatid cysts are found in the liver and the lungs
o E. multilocularis ▯ multilocular cysts are found in the liver and in the
peritoneal cavity. Canids tend to want to nom on the entrails of the
o Schistosoma use chemoreceptor and tactile receptors to figure out where to
go. They have very specific tissues and organs that they target. If the
parasites end up in the wrong tissue, which does happen, they can’t live
o Dirofilaria immitis (dog heartworm) ▯major killer of pets. First cases
were in Morocco, Algeria, etc. Got exported to North America and
Europes fairly early. Adult parasites live in the heart and in the lungs
o Wuchereria bancrofti adults live in the lymphatics.
o Onchocerca volvulus adults live in the tissues near the skin. Their
microfilaria live in the skin so that they can be taken up by mosquitoes.
The adults live there so that they can put the microfilaria out near the skin
so that they can be picked up by mosquitoes to increase transmission.
o Microfilaria follow a diurnal migration pattern. They tend to move to the
skin at night (that is when the What do the microfilariae use to get back to the skin at night?
Probably due to the decrease in cardiac output. Microfilariae
follow a pressure gradient towards the extremiti