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212 Cards in this Set
- Front
- Back
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Parasitology
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Eukaryotic organisms that are metabolically dependent on another animal during one or more stages of their life cycle.
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Endoparasite
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Found inside a host
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Ectoparasite
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Found outside of a host
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Obligate parasite
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MUST be a parasite to survive.
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Facultatise parasites
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Can live as parasites or as free living organisms. Often, these are accidental parasites.
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A maggot infestation would be an example of which kind of parasite?
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Facultative
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Direct Life Cycle
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Parasites with only one host
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Indirect Life Cycle
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Parasites with more than one host
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Definitive Host
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The host in which the parasite attains sexual/reproductive maturity
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Intermediate Host
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Serve as a temporary but necessary environment for the completion of immature stages of the life cycle
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What is the intermediate host in canine heartworm disease?
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Mosquitos
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Paratenic Host
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Host not needed to complete the life cycle, but that serves as a vehicle for reaching a necessary (usually definitive) host.
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Transport Host
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Same as a paratenic host.
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What kind of development occurs in a paratenic host?
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NONE!
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Vector
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Arthropods or other invertebrates that serve as hosts or carriers for infectious agents.
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Reservoir Host
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Infected animals which serve as a source of infection for others.
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Sylvatic reservoir
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A wild animal reservoir
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Are reservoir hosts always symptomatic for the diseases they carry?
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Sometimes - deer mice are not symptomatic for Lyme disease, but skunks will show symptoms from rabies.
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Prepatent Period
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Period required to reach reproductive maturity after infection of the definitive host
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Patent infection
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An infection that is reproductively mature
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Generation Time
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The time it takes a parasite to go from one infected host to another with a mature infection.
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Zoonosis
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A disease that can be transmitted between animals and humans
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Taxonomic Divisions
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Kingdom, Phylum, Class, Order, Superfamily, Family, Genus, species
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When treating parasites in large animals, we aim for…
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control.
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When treating parasites in companion animals, we aim for…
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elimination.
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What are two factors that make an animal more susceptible to parasitic diseases?
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Stress and age (younger are more likely)
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Classes included in phylum Arthropoda
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Insecta, Arachnida, Crustacea
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Withdrawal period
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The length of time that a food animal or product must be withheld from entering the food chain following treatment with a drug.
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Extra label use
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Use of an approved drug in a manner that is not in accordance with the approved label directions.
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Three types of arthropod control agents
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Pesticides, biological control, physical control
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Pyrethrins
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Natural botanicals that disrupt ion transport in nerve membranes, leading to paralysis of the organism. They work against many species, but are not for nursing pups or kittens and directions must be followed carefully with cats. They have a repellant activity and are quickly metabolized.
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Signs of pyrethrin toxicity
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salivation, diarrhea, vomiting, ataxia, convulsions, death
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Pyrethroids
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Synthetic, pyrethrin-like but more potent and longer lasting. Cause paralysis of organism, have repellent activity, toxic to fish, and NEVER for cats unless specifically labelled as such.
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Examples of pyrethroids
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usually end in "-thrin": permethrin, cypermethrin, deltamethrin, lambdacyhalothrin, beta-cyfluthrin
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Macrolides (Macrocyclic Lactones)
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Avermectins or milbemycins. Act on internal and external parasites by binding glutamate gated chloride channels leading to hyperpolarization of nerves and muscles (paralysis.)Work against arthropods, nematodes. Persist in animal because lipophilic and are found as oral meds, spot ons, feed additives, plant pesticides.
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Examples of Macrolides
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Avermectins: ivermectin, doramectin, selamectin, eprinomectin. Milbemycins: milbemycin, moxidectin.
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Neonicotinoids (nicotinoids, chloronicotinyls)
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Work against fleas, lice, plant pests by binding to postsynaptic nicotinic acetylcholine receptors in insects. Low toxicity because mammalian receptors are different. Persist for very short time to weeks and can be administered orally or topically.
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Examples of Neonicotinoids
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Imidacloprid, nitenpyram, dinotefuran
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Spinosyns
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Technically a macrocyclic lactone, but work like a neonicotinoid. Work against insects by activating nicotinic acetylcholine receptors. Low toxicity, persist for weeks, oral or topical (in large animals.)
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Example of Spinosyn
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Spinosad
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Phenylpyrazoles
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Work against insects, ticks, mites by binding to GABA receptors, inhibiting the flux of ions into nerve cells, resulting in hyperexcitability and death. Do not seem to bind to mammalian receptors but should NOT be used inr abbits, fish, aquatic systems. Persist because lipophilic, stored in hair follicles, sebaceous glands, released onto skin. Administered topically.
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Example of a Pheylpyrazole
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Fipronil
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Formamidines
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Works primarily against ticks, mites by inhibiting monoamine oxidase. Safe, but should NEVER be used in horses. Persists for days, administered topically.
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Example of Formamidine
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Amitraz
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Signs of formamidine toxicity
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Lethargy, hypotension, mydriasis, hypothermia, vomiting. In horses, or in dogs who eat their preventic collars.
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Mydriasis
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Dilated pupils
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Semicarbazone
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Works against insects by blocking sodium channels in axons, preventing neurotransmission. Low toxicity because mammalian receptor different, stays for weeks distributed in the haircoat. Administered topically.
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Example of Semicarbazone
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Metaflumizone
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Organophosphates
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Works against many arthropods by inhibiting acetylcholinesterase. Effective but dangerous, especially in cats. May see used in large animals with mites. Absorbed systemically from topical products, persists for several weeks.
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Signs of organophosphate toxicity
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salivation, lacrimation, urination, diarrhea, respiratory failure, chronic neurotoxicity
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Examples of Organophosphates
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Chemical names will contain "phosphate," "phore," "phosphore," "phos." Generic names include fenthion, chlorpyriphos, dichlorvos, diazinon, tetrachlorvinphos.
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Carbamates
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Work similarly to organophosphates and CAN NOT be combined with them! Not as toxic as OP's.
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Example of Carbamates
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Names usually includes "carbamate." Sevin dust.
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Chlorinated Hydrocarbons (organochlorines)
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Useful for vector-born diseases, but most unavailable in the US because of environmental persistence. Work by inhibiting ion Na, Ca flux which interferes with depolarization and repolarization of cell membranes.
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Examples of Chlorinated Hydrocarbons (Organochlorines)
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DDT, lindane, dieldrin, aldrin, methoxychlor
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Lime Sulfur
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Safe, especially for very young animals. Smells bad - usually used in hospitals, but not as much anymore.
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Human Repellant Products
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DEET, picardin (oil of lemon eucalyptus)
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"Natural" Repellant Products
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D-limonene (citrus oil), herbal preparations
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Insect Development Inhibitors
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Low toxicity, can be used at low doses, may persist for months, can be topical or environmental. Inhibit the synthesis of chitin, a protein used in making insect exoskeletons.
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Examples of Insect Development Inhibitors
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Diflubenzurone, lufenuron
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Insect Growth Regulators
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Low toxicity, can be used at low doses, may persist for months, can be topical or environmental. Analogs to juvenile hormones that prevent insects from going from one stage to another.
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Examples of Insect Growth Regulators
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Methoprene, Pyriproxyfen
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Parasitoid
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An animal that feeds on host animals as a larva, then kills the host after the larval stage.
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Biological controls
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Traps containing pheromones, parasitoid wasps, predators
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Integrated Pest/Parasite Management
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Uses a combination of control techniques and may attack different stages of the parasite's life cycle. Can help slow the development of resistance.
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Resistance
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When a strain of an organism develops the ability to tolerate doses of toxicants that would prove lethal to the majority of individuals in a normal population of that organism. A heritable characteristic resulting from random mutations always present in a population.
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Target-site resistance
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Genetic differences in the molecular target of a drug keep it from binding
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Metabolic Resistance
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Increased inactivation or removal of a drug.
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Penetration Resistance
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Slower absorption of a drug.
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Behavioral resistance
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Avoidance of a pesticide.
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Important Factors in Resistance Development
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Doses of drugs used (heterozygotes are less susceptible to standard doses), formulations of drugs used (short acting = less selection pressure for resistace), human factors, size of refugia
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Refugia
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Portion of the parasite population not exposed to a drug. A larger refugia means a lower rate of selection for resistance.
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Techniques for minimizing resistance development
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Maximizing the use of non-pesticide controls, using pesticides only when necessary, using the appropriate dose and route of administration, rotating pesticides
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Orders within class Insecta
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Siphonaptera (fleas), Diptera (flies), Phthiraptera (lice), Hemiptera (true bugs, kissing bugs)
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Order within class Arachnida
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Acari (ticks and mites)
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General characteristics of Insecta
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Adults have 6 legs, body divided into head, thorax, abdomen. Salivary glands often harbor pathogens. Oxygen diffused through spiracles. Ganglia and nerve cords are target of insecticides.
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Complete metamorphosis
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Larvae bear no resemblance to adults.
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Incomplete metamorphosis
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larvae look like small adults.
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Venemous or Irritant Insect Orders
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Hemiptera (assasin bugs), Coleoptera (blister beetles), Lepidoptera (urticating caterpillars), Hymenoptera (wasps, bees, ants.)
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Siphonoptera
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Fleas - macroscopic, usually brown. Wingless, laterally compressed, undergo complete metamorphosis.
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Ctenocephalides felis felis
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The cat flea - the most common flea on dogs and cats, also on ferrets. Worldwide distribution, four stage life cycle, prefer high humidity and warmth.
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Ctenocephalised canis
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The dog flea - much less common than the cat flea.
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Ctenocephalides pulex
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The human flea.
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Life Cycle of C. felis
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Minimum around 14 days (egg = 2, larva = 6, pupa = 6.) Adults are permanent ectoparasites once on the host. Femailes lay eggs on the host, eggs fall off, hatch in a few days if warm and humid. Larvae feed on organic debris and MUST eat adult flea feces. Pupa is in a sticky, silky cocoon and can hatch from 5 days - several months. Pupae can sense vibrations and CO2, which tell them the host is around and to emerge from their cocoons.
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Winter Survival of C. Felis
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No stages can withstand sustained cold, so fleas overwinter in houses or reservour hosts.
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Reservoir Hosts of C. Felis
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Raccoons, opossums, other animals with warm nests.
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Diagnosis of C. felis
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Observation of adults, flea dirt, clinical signs (scratching, pruritis if sensitive, hot spots, anemia.) Usually found on tailhead, thighs, abdomen, neck.
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Clinical important of C. felis
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Common cause of vet visits, important income source in the southeast.
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Fleas act as vectors for…
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tapeworms, Bartonella henselae (Cat scratch disease)
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Drugs used for flea control
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Imidacloprid, fipronil, nitenpyram, selamectin, metaflumizone, spinosad, pyrethrins, pyrethroids, organophosphates, lufeneron (IDI), methprene (IGR), pyriproxyfen (IGR)
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True of False: Organophosphate flea collars work well to treat and prevent fleas.
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FALSE - they are a waste of money! IGR collars work better.
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Ultrasonic collars, brewers yeast, and garlic are effective for the control of…?
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NOTHING - specifically, studies show they do not work well against fleas.
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Environmental Flea Control
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Vacuuming, lavendar pet bedding, sprays/foggers with IGR/IDI (sprays penetrate better), control of flea habitats outside
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Clinical importance of C. felis in other hosts
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Can be found on ferrets (use cat parasiticides), humans (transient host - can cause severe hypersensitivity), confined goats and calves.
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Rodent fleas are vectors of…
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Yersinia pests (plague, especially in SW US.)
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Echidnophaga gallinacea
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Stick tight flea of poultry
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General Characteristics of Lice
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Small, wingless, dorsoventrally flattened, often white or gray, some brown, no complete metamorphosis
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Anoplura
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Sucking Lice
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Mallophaga
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Biting or chewing lice
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Systemic drugs can affect which kinds of lice?
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Sucking lice, but they may not affect biting lice
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How much of a louse's life cycle is spent on the host?
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The ENTIRE life cycle
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Minimum louse life cycle
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3 weeks
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Transmission of lice occurs through…
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Direct contact with infested animals or fomites
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What makes lice so host specific?
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The claws on the ends of their feet are sized to fit the hair shaft size of their specific host.
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During which season are lice most common on outdoor animals?
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Winter because haircoats get longer and lice are not exposed to as much sun and because animals tend to be closer together and may be nutritionally depressed.
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Clinical Signs Associated With Lice
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Pruritus, hair loss and poor hair coat, and in severe cases anemia, debilitation
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Clinical Importance of Lice in Small Animals
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Uncommon in well cared for pets
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Clinical Importance of Lice in Horses
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Uncommon, but easily introduced and spread
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Clinical Importance of Lice in Birds
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Common in wild animals and usually well tolerated, but uncommon in pets except outside poultry
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Clinical Importance of Lice in Food Animals
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Common, but usually not severe
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Are lice commonly present in the environment, as fleas are?
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No. Lice can live for only a few days off the host.
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Drugs Used to Treat Lice
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Depend on the host, but could be pyrethrins/pyrethroids, macrolides, organophosphates, neonicotinoids, and others
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Treatment of Lice
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Drugs kill adults, NOT eggs. Repeat treatment at 2 weeks or use products with long residuals. Usually must treat all animals.
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Which small animals may be sources of human lice?
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NONE
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Pediculus
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Human head and body louse
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Phthirus
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Pubic Louse (crabs)
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Order Diptera
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Flies
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General Characteristics of Flies
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1 pair of membranous wings (usually), complete metamorphosis
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Types of Flies That Cause Problems
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Adult non-biting, adult biting, larval flies
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Nonbiting Flies
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Musca domestica and others. Not parasites but can act as a vectors, eggs often found in decaying organic material, house flies have a 2 week cycle.
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Musca autumnalis
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Face fly - females are parasites who eat secretions. Eggs laid in fresh manure, primarily on ruminants/horses. Cause irritation around eyes and mechanically transmit Moraxella bovis.
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Moraxella bovis
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Bovine pink eye spread by face flies. Can eventually cause inflamed eyes, chronic fibrosis and scarring, blindness.
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Haematobia irritans
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The horn fly, a biting fly. Found on the back and ventrum of cattle and horses - a resident parasite. Eggs are laid in fresh manure. Cause irritation and decreased production. Only females feed on animals and take blood meals.
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Stomoxys calcitrans
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The stable fly, a biting fly. Visit host 1-2x/day, bite flanks or legs. Lay eggs in decaying plants and manure. Cause fly worry and fly bite dermatitis.
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Fam. Tabanidae
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Horse and deer flies (biting flies.) Females are parasitic, lay eggs near water. Cause fly worry and act as mechanical disease vectors.
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Mosquitoes
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Biting flies that lay eggs in water. Females bite. Cause fly worry, hypersensitivity, important disease vectors.
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Simulium
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Blackflies, buffalo gnats. Small, lay eggs in rapidly moving water. Cause fly worry, fly bite dermatitis, act as disease vectors. Often bite horse and dog ears.
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Culicoides
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No-see-ums, midges. Very small biting flies, larvae are aquatic or in moist soil/humus. Cause fly worry, fly bite allergy (esp. horses), disease vectors (blue tongue.)
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Control of Adult Flies
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Mechanical (screens, sheets), control manure (get rid of it, feed through pesticides, wasps/traps), use of dust bags, ear tags, pour on pesticides on large animals.
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Common Pesticides Used in Fly Control
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Organophosphates, pyrethrpids, macrolides
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How do flies survive the winter?
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By surviving in inactive stages as adults, surviving as eggs or larva (species dependent.)
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Myiasis
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Any infection due to the invasion of the tissues or cavities of the body by the larvae of dipterous insects. May be cutaneous ("fly strike") or internal (obligatory for parasite.)
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Fly Strike
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Eggs that are normally laid in decaying matter are laid in an animal. Flies are attracted to the animal bu necrotic smells of wounds, body secretions, dried blood. Maggots ONLY feed on necrotic tissue. Commonly from blow flies, flesh flies.
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Calliphorids
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Blow flies - a common source of cutaneous myiasis.
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Sarcophagids
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Flesh flies - a common source of cutaneous myiasis.
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Clinical Signs of Fly Strike
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Maggots, may cause systemic toxic reactions.
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Treatment of Fly Strike
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Removal of maggots, antibiotics.
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Prevention of Fly Strike
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Wound sprays in fly season, castration/dehorning/etc performed before fly season.
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Cochliomyia
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Fly strike caused by screwworms - requires LIVING tissue. Eradicated from the US by sterile male release programs. NOTIFIABLE disease.
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Internal Myiasis
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aka bots/grubs/warbles. Adults are hairy looking, look like bees. Hosts actively avoid them. Larvae are obligate internal parasites.
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Gastrophilus spp.
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Horse bots. Eggs laid on legs/face, migrate in gums/tongue. Move to stomach for 10-12 mos, pass out in feces, pupate on ground. No recognizable clinical syndrome (occasional lesions in mouth, eggs may be seen on legs, rarely ulceration/perforation.)
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Treatment/control of gastrophilus
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ivermectin, moxidectin, warm water on legs to stimulate egg hatching
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Hypoderma bovis and lineatum
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Cattle grubs/warbles/heel flies (occasionall horses/goats.) Eggs glued to leg hairs, larvae burrow through skin, migrate to tissues along esophagous or spinal cord for 2-4 mos, migrate to SQ tissue on back, make bump with hole 5-8 weeks, pupate on ground. Cattle actively avoid flies.
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Clinical signs of cattle grubs
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lumps on back, economic loss from gadding and from migration/hide damage caused by larvae.
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Gadding
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When cattle run around to avoid flies that cause grubs/warbles.
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Treatment/Control of Cattle Grubs
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Systemic - usually use macrolides or organophosphates. DO NOT treat when grubs are along esophagous or spinal cord because can cause lots of inflammation --> bloat or paralysis. Ideally, treat @ end of season before bots develop.
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Cuterebra spp.
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Rodent/rabbit bot flies. Lay eggs near burrows or along trails, host picks up larva, develop in SQ cyst, pupate on ground.
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Clinical signs of cuterebra?
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SQ nodule (back of head/neck), secondary infection.
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Which species of bot may infect dogs and cats?
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Cuterebra
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Treatment/Control of cuterebra
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Remove carefully (don't damage bot or it releases lots of antigen!), antibiotics if needed.
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Which species of bot occasionally infects humans?
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Cuterebra
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Oestrus spp.
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Nasal bots of small ruminants. Larvae migrate to upper nasal passages/sinuses. Cause nasal discharge.
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Diptera Hippoboscidae
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Bloodsucking house flies. Adults have flat looking body.
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Ked
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Melophagus - a fly that affects sheep and goats. Very small wings/wingless
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Phlebotamine flies
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Sand flies. Transmit Leishmania infections worldwide (though not common in US.)
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Tsetse flies
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Transmit African trypanosomiaisis.
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Bed Bugs
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Cemiz, order Hemiptera. True bugs. Mostly on humans, but will feed on other warm blooded animals.
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Kissing Bugs
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Triatomid bugs. Transmit Chagas Disease (Trypanosoma cruzi.)
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Stages in Arachnid Life Cycle
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4: egg, larva, nymph, adult
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Leg Numbers in Arachnid Life Stages
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Nymphs and adults: 8, larvae: 6
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Body Parts of Arachnids
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2 Parts: gnathosoma (capitulum) and Idiosoma
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Gnathosoma
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The capitulum of arachnids. Carries the mouthparts.
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Life Cycle of Parasitic Mites
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All stages on host, usually short
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Transmission of Mites
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Transmitted by direct contact, fomites. Don't survive well off of host.
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Mange
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A general term for describing mite infestations. No specific meaning.
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Sarcoptic Mites
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Burrowing mites, females make tunnels. Round with short legs. Life cycle ~3 weeks, easily spread.
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Diagnosis of sarcoptic mites
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Skin scraping: scrape multiple areas, especially at the periphery, until you get capillary bleeding. May find adults or eggs on fecal exam.
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Sarcoptes scabiei
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Separate varieties for each host species, but can't tell these apart when looking morphologically. Most often on dogs in US, pigs, rare on ruminants and horses. Mites like hairless areas or thin hair.
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Clinical Signs of Sarcoptes Scabiei
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Intense pruritis, alopecia, thickened/wrinkled skin (chronic), secondary bacterial infection, self inflicted trauma
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Treatment/ Control of Canine Sarcoptes
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Treat ALL animals, use macrolides/amitraz, don't need to treat environment extensively.
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Zoonotic Potential of Sarcoptes Scabiei
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Lesions in areas of contact, but humans have their own sarcoptes.
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Sarcoptes in Swine
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Important in younr pigs (lost production), carried by old sows, can be eradicated from closed systems with macrolides
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Treatment of Sarcoptes in Large Animals
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Macrolides
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Sarcoptes in Camelids
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SEVERE disease
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Notoedres cati
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Sarcoptic mange mite of cats. Found everywhere, but rare in US. Diagnose through skin scraping - lesions on head and neck.
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Knemidocoptes spp.
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Sarcoptic mange mites of poultry, pet birds. Most common on nonfeathered parts of body. Mites burrow in and cause crusty, scaly lesions with a honeycomb appearance. Scaly leg mites (poultry), scaly face mites (pet birds)
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Treatment of Knemidocoptes spp.
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Use macrolides
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Psoroptic Mites
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Surface dwellers (no burrowing), oval shaped, longer legs than sarcoptes. Short life cycle (min 2 weeks), diagnose by skin scraping (except ear mites), macrolides effective.
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Psoroptes ovis
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On ruminants (probably host specific), worldwide but eradicated in US sheep.
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Transmission of Psoroptes ovis
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Direct contact
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Clinical importance of Psoroptes ovis
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Severe pruritus and skin leasions. Notifiable infestation. Importance diminishing b/c macrolide use, treat all animals.
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Psoroptes cuniculi
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Otic parasite of rabbits. Occasionally in alpacas, goats, horses (rare.)
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Chorioptes
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Ruminants, horses (host specific), found everywhere. Transmitted by direct contact.
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Location of Chorioptes on host
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Cattle: tailhead, udder and perineal reagion; Small ruminants: leg, lower body; horses: legs (especially feathered horses.)
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Clinical Importance of Chorioptes
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Usually not important in cattle. Pruritus/dermatitis in small ruminants and horses.
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Otodectes cynotis
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Parasite of ear canal in dogs, cats, ferrets. Transmitted by direct contact.
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Clinical Signs of Otodectes cynotis
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Otitis externa (intense pruritus), "coffee grounds" in ear
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How are Otodectes cynotis and Chorioptes differentiated?
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You MUST have context - they look just the same.
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Treatment of Otodectes cynotis
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Clean ear, use a miticide (macrolides, pyrethrins)
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Demodex spp.
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Separate species for each host, very host specific. Parasite of hair follicles or sebaceous glands. Transmitted from dam shortly after birth and can be thought of as normal skin fauna.
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Diagnsosis of Demodex
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Deep skin scraping. Squeeze the skin fold first. Look like a cigar with legs.
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Clinical Importance of Demodex
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Important in dogs. Clinical signs appear when mites proliferate beyond normal levels. Interfere with follicles, gland function.
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Forms of Canine Demodecosis
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Localized, generalized
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Localized Form of Demodecosis
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Some pups (~3-10 mos/age.) Small, hairless regions (nonpruritic), 90% resolve spontaneously, 10% progress.
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Generalized Form of Demodecosis
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May spread from localized form in pups or may be adult onset.
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Clinical Signs of Canine Demodecosis
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Alopecia, erythema, sebhorrhea, pyoderma, pruritus later.
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Generalized demodex is more common in which kinds of dogs?
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Purebred, shorthaired dogs.
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Treatment and Control of Canine Demodex
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Amitraz, macrolides. Don't breed animals with a history of the generalized form.
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Cat Demodex
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Rare - causes ear and face mange
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Ruminant demodex
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Usually causes non-pruritic pustules
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Human Demodex
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Rare lesions
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Cheyletiella spp.
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"Walking Dandruff" infrequently on dogs, cats, rabbits. A surface mite spread through direct contact transmission. Often few clinical signs, but may show dandruff and pruritus.
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Diagnosis of Cheyletiella
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Hair coat brushings, scotch tape to hair coat.
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Treatment/Control of Cheyletiella
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Can use flea/tick products, control environmentally.
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Zoonotic Potential of Cheyletiella
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Temporary in areas of contact
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Trombiculid Mites
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Chiggers or Harvest mites. Found worldwide, spp vary. Only larvae are parasitic, acquired from environment and attach for several days. Pruritus lasts after mites are gone.
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Diagnosis of Trombiculid Mites
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See red/orange mites, especially on face and ears. Pruritic leasions.
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Treatment of Trombiculid Mites
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Acaracidal treatment if mites present. Treat symptomatically.
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Mesostigmatid Mites
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Larger than some other parastitic mites, longer mouthparts.
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Ornithonyssus sylvarium
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Northern fowl mite, a mesostigmatid mite - an avian blood feeder that spends its entire life cycle on the host. Causes decreased weight gain and egg production.
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Rodent Ornithonyssus
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A mesostigmatid mite than can affect humans.
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Dermanyussus gallinae
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Red poultry mite - a mesostigmatid mite that affects poultry and can be a pest to people. Found on host at night (bloodsucking.) Find red or black mites in environment during the day.
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