Biology of Parasitism 1 PDF

PARASITOLOGY 1 Biology of Parasitism I Dr. Cassan Pulaski  Hi! Education: UGA CVM since 2019 – MPH, LSU (2012) – post-doc: Drs. Kaplan & Moorhead...

PARASITOLOGY 1 Biology of Parasitism I Dr. Cassan Pulaski  Hi! Education: UGA CVM since 2019 – MPH, LSU (2012) – post-doc: Drs. Kaplan & Moorhead – DVM, LSU (2013) Current position: – Clinical Parasitology Residency, LSU (2015-2018) – 40% Teaching – PhD, LSU (2022) – 40% Service (AVDL, Parasitology Section) Major: Parasitology, Minor: Entomology – 20% Research (VBDs, AH resistance, EPI) Small Animal practitioner since 2013 (relief) Teaching veterinary students since 2013 Field experience with small animal, large animal, wildlife Lesson Learning Objectives: Students will be able to identify the difference between a definitive, intermediate and paratenic/transport host. Students will be able to identify whether a parasite is a helminth, protozoa, or arthropod. Students will be able to explain a nematode, cestode, and trematode life cycle to a peer. Students will be able to compare and contrast ectoparasites. BUT FIRST… My cell: 985-590-8416 DINK household in West Athens  * * * References www.capcvet.org www.heartwormsociety.org * https://www.wormx.info/ https://aaep.org/ g g Boards & What is a parasite? “One who dines at the table of another” Eukaryote implied (not viral or bacterial) An organism that derives a survival benefit from a host, at the expense of the host – Living inside a host: infection (hookworms, coccidia) – Living on a host: infestation (fleas, ear mites) The ratio of free-living to parasitic is about 60:40 for all living species on Earth  Bony fishy Huge group  Parasites Helminths Protozoa Arthropods Nematodes Flatworms Insects Arachnids (Roundworms) n Flies Ticks Cestodes (Tapeworms) Fleas Mites Trematodes Lice (Flukes)  Infections versus Disease Grazing/herd animals -> don't necessarily GOAL to Control Infection: presence of a parasite in a host > - treat infections disease – May be clinically inapparent or result in local or generalized tissue injury VS infestation: on a host VS contamination: on an inanimate object Disease: GOA to – Any deviation from the normal structure or function of any body tissue or organ – “physiological dysfunction”  Life Cycle Terms and Concepts Patent: when infection becomes diagnostically evident ↳ "early infection" ↳ (i. e in feces). eggs Direct versus Indirect lifecycle – Direct: transmission from host to host (including those with forms in environment) – Indirect: transmission through intermediate host or vector ex Heart worms non-negotiable intermediate. - - mosquito doge mosquito dog - Definitive Host: host in which sexual stages of parasite occur Intermediate Host: parasite develops but does not reach sexual maturity, often a required part of ↳ lifecycle mosquito for heart ex. worms - Paratenic / Transport Host: simple mechanical carry of infectious form of parasite, without examp Aberrant (dead-end) Host: parasite infects and may cause disease, but further transmission does growth/development of the organism (ex parasite mouse) dies-cat eats · in mouse - (toxoplasma) not occur (ex EPM horses stops horses/horses. in - wh (ex can't shed it) primates Malaria normally. in that it shouldn't be Reservoir Host: parasite infects without host experiencing any negative effects, but can still Symptoms no transmit it to other susceptible species  Definitive Host Normal host in which parasite reaches sexual maturity and reproduction occurs  Intermediate Host Parasite develops/grows but does not reach sexual maturity Required part of life cycle Often the prey species in a predator/prey relationship Intermediate Hosts  Intermediate Hosts Arthropods also commonly serve as intermediate hosts May also serve as vector – any agent that transmits a disease organism (insect not be an intermediate - mechanical transmission might as VECTORS to host , but can carry parasites other animals through their normal behavior Paratenic/Transport Host Transport host – Not required part of life cycle sex Fly · exampleepore – Parasite survives but does not develop – May assist parasite in making the jump in biologic niche from intermediate host to definitive host Aberrant Host Host is not normally part of the life cycle – Not the normal course of events -- accidental infection – Parasites usually do not fully mature -- infections usually do not become patent – May be associated with a greater degree of pathology  Parasites Helminths Protozoa Arthropods Nematodes Flatworms Insects Arachnids (Roundworms) Flies Ticks Cestodes (Tapeworms) Fleas Mites Trematodes Lice (Flukes) Protozoan ↳ frequently wh in cells Single cell eukaryotic organism Very small (compared to worms) with specialized structures and organelles Complex life cycles with many different stages and often multiple hosts – Different terms for different stages, and parasite specific Wide range of morphology  Trematode Nematode Round Round Cestode Hook Protozoan Tape Hook  Parasites Helminths Protozoa Arthropods Nematodes Flatworms Insects Arachnids (Roundworms) Flies Ticks Cestodes (Tapeworms) Fleas Mites Trematodes Lice (Flukes) Trematodes (Flukes) Flatworms – Very complex life-cycles – All species require at least 2 hosts First host is always a snail Cor snail-like Slug) Many species use 3 or 4 hosts Shistozome General Structure of Trematodes Flat, bilaterally symmetrical and acoelomate 2 Suckers: specialized holdfast organs Incomplete (blind) digestive tract Hermaphrodites (usually) ↳ female a male repro. w/in same organism Example of Trematode Life Cycle Fasciola hepatica (common liver fluke) Trematodes Dicrocoelium dendriticum o behavior A f nas blades -changes  Parasites Helminths Protozoa Arthropods Nematodes Flatworms Insects Arachnids (Roundworms) Flies Ticks Cestodes (Tapeworms) Fleas Mites Trematodes Lice (Flukes) Cestodes (Tapeworms) Dorsoventrally flat – Bilaterally symmetric – No body cavity, No digestive tract Basically a string of reproductive organs – Hermaphrodites: each segment has both ovaries and testis “All” tapeworms use at least 2 hosts (usually predator-prey relationships) – Most worms fairly harmless to DH ↑ definitive host Adults usually in digestive tract – Larval stages in IH assoc with greatest pathology Immature forms usually in tissues Structure of Cestodes proglottids scolex = anchor strobila neck  Example of Cestode Life Cycle Anoplocephala spp. Tapeworms  Parasites Helminths Protozoa Arthropods Nematodes Flatworms Insects Arachnids (Roundworms) Flies Ticks Cestodes (Tapeworms) Fleas Mites Trematodes Lice (Flukes) Nematodes (“Roundworms”) Perhaps the most successful type of animal on earth – Believed to be the most abundant animals on earth So far 25,000 species have been classified, there could be >100 million Free-living, Plant-parasitic and Animal-parasitic present in every imaginable habitat – Sulfurous sediment, deep-sea trenches, arctic ice, soil, mammals, insects, plants, others Body sizes range from than 1 m Cylindrical, elongate, tapered at ends Majority of important helminth pathogens are nematodes Nematode Structure and Function Example of Nematode Life Cycle Toxocara canis (canine roundworm)  TREMATODE CESTODE NEMATODE Leaf-like, Shape Tape-like, segmented Elongated, cylindrical unsegmented Monoecious Sexes Monoecious Diecious (not blood flukes) Anterior End Suckers, no hooks Suckers & hooks No suckers/hooks Present but Alimentary Canal Absent Present & Complete incomplete Body Cavity Absent Absent Present  Parasites Helminths Protozoa Arthropods Nematodes Flatworms Insects Arachnids (Roundworms) Flies Ticks Cestodes (Tapeworms) Fleas Mites Trematodes Lice (Flukes) The Arthropods Largest of the animal phyla – Few are parasitic or serve as vectors of pathogens Characteristics: – Segmented body – Paired segmented appendages – Bilateral symmetry – Chitinous exoskeleton · diatomaceous earth ↳ can exoskeleton out dry Phylum Arthropoda Class Class Class Insecta Arachnida Pentastomida  Definitive versus Intermediate Hosts Normal host in which Parasite develops but does parasite reaches sexual not reach sexual maturity maturity and reproduction Required part of life cycle occurs Often the prey species in a predator/prey relationship Biological vs. Mechanical Transmission Biological: pathogen reproduce or develop in arthropod before transmission Biological Mechanical: pathogen does not reproduce or develop in vector Vector Biological Vector: A living obligate host in which the parasite undergoes growth/development and/or multiplication (REQUIRED) Mechanical Vector: Object (animate or inanimate), which transports a parasite to its host 3 pairs of legs 4+ pairs of legs  Phylum Arthropoda Class Insecta Class Insecta Class Arachnida Class Pentastomida Air-breathing arthropods with 3 distinct body regions (head, thorax, abdomen) One pair of antennae 3 pairs of legs 1-2 pairs of wings (adult)  Phylum Arthropoda Class Arachnida Class Class Class Insecta Arachnida Pentastomida Cephalothorax and abdomen are combined into one body region No antennae 4 pairs of legs No wings Questions?