What We Do
What is parasite immunology?
The parasite-host interaction can best be described as an arms race. In the face of constant challenges by parasites, hosts have evolved a complex and elaborate series of measures to prevent or dampen infection. Parasites on the other hand, utilize multiple mechanisms to modulate and evade the host’s immunological responses in order to persist within their specialized niche. Parasite-immunology is the integration of two disciplines: the study of parasites (parasitology) and the study of an organism’s response to challenge and the recognition of self versus non-self, to answer scientific questions regarding the intricate and complex nature of host-parasite interactions.
What is a parasite?Parasites are organisms live in or on another organism (the host) and survives at the expense of the host. Microparasites classically refer to parasitic organisms that replicate within the host. Microparasites are often tiny and not visible by the human eye without the aid of a microscope such as the single-celled, eukaryotic protozoa such as Giardia, Leishmania, and Plasmodium (the parasite that causes malaria). Macroparasites can be found either in or on the host and do not replicate within the host. These parasites are multicellular and large enough to be seen without the aid of a microscope. Macroparasites come in two varieties: Ectoparasites and endoparasites. Ectoparasites live on the host and include fleas, lice, ticks, mites and flies. Endoparasites live in the host in various tissue niches and include nematodes (roundworms), trematodes (flatworms or flukes), and cestodes (tapeworms).
Gastrointestinal nematode parasitism
Gastrointestinal nematode parasitism is responsible for vast economic losses in sheep production systems across the United States. While there are several genera of gastrointestinal nematodes of sheep, Haemonchus contortus has the highest clinical significance. Haemonchus contortus is a trichostrongylid nematode that parasitizes the abomasum (the section of the four-chambered ruminant stomach that is most similar to ours) of sheep.
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The lifecycle of H. contortus is simple, containing both environmental and parasitic stages as seen in the illustration above (further information can be found here). H. contortus has a specialized mouthpart called a stylet that it can extend from its buccal cavity like a switchblade that is uses to nick the abomasal wall causing blood to flow which it will feed on. A single female can consume about 50µl of blood a day. While this may not seem like a lot of blood, when you consider than an animal is often infected with several thousand worms at a time the loss of blood can quickly take its toll. Heavy infections result in severe anemia, hypoproteinemia and submandibular edema of the host. Clinically, infected animals present with general signs of weakness, unthriftiness and failure to thrive as they often have loss of appetite and weight loss. These symptoms can be followed by death of the infected animal. Breeds of sheep resistant to GIN are able to survive, and in some cases perform well despite infection due to production of rapid and protective immune responses. Immunological events contributing to superior immunity in these breeds are not well defined, yet studies indicate that resistant sheep generate a potent, local inflammatory response shortly after infection. Susceptible breeds however, have a delay in generating a sufficient inflammatory and protective response which allows the parasite to mature and establish an infection.