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Abomasum   The fourth and final compartment of the ruminant´s stomach.
Abscess   A confined collection of pus.
Acute   Sudden; an acute infection is one that develops rapidly and is usually of short duration.
Albumin   A blood protein which helps to prevent edema by drawing fluid from the tissues into the blood.
Allergenic   Capable of causing allergy (a sudden inflammatory response).
Alternate grazing   The technique of periodically changing the type of livestock that graze on a given pasture; reduces parasite loads on pasture since different animals are affected by different parasites.
Alveolus   One of the network of tiny spaces in the lung; the site where oxygen is presented to the blood and waste gases are removed for exhalation.
Anaemia   Condition of low blood concentration of haemoglobin, the oxygen–carrying protein in red blood cells. Haemoglobin must contain iron to function properly. Continual blood loss can cause iron–deficiency anaemia by depleting body iron stores.
Anorexia   Loss of appetite.
Anterior   Front; toward the head.
Anthelmintic   Drug used to eliminate helminth parasites from the host.
Arachnid   Arthropod with two body segments: a fused head and thorax, and an abdomen. The life cycle is one of incomplete metamorphosis. Adults have four pairs of legs and lack both wings and antennae.
Arthropod   Animals with jointed legs and hard external skeletons; includes insects, arachnids, centipedes, crustaceans (crabs, shrimps), and others.
Ascites   Fluid accumulation in the abdominal (peritoneal) cavity.
Bladder worm   1. Infective stage of Taenia tapeworm (Cysticercus), Name refers to the fluid filled bladder which surrounds the larval scolex of scolices. 2. Common name of Capillaria plica, found in the dog urinary bladder
Bots   Larvae of several fly species, particularly Gastrophilus (horse bot), Oestrus (sheep bot), and Dermatobia and Hypoderma (affect cattle and other species).
Bottle jaw   Fluid accumulation under the lower jaw (submandibular edema).
Bronchi   Larger–sized airways of the lungs, which connect the trachea with the smaller airways.
Bronchitis   Inflammation of the inner lining of the bronchi.
Buccal capsule   Mouth cavity of a nematode.
Bursa   A system of expansions of the cuticle at the posterior end of male strongyle nematodes. The bursa is involved in holding the male and female together in copulation; its shape is species characteristic, and is used to identify nematodes.
Capillary   One of the tiny blood vessels which form a network in the body tissues.
Capitulum   False head of a tick; bears the mouthparts and the probing and sensory structures. Its shape is characteristic of the tick species.
Carrier   An apparently healthy animal which is infected with a pathogenic organism; the carrier can transmit the organism to other animals, which may then develop disease.
Cercaria   A free–living larval trematode which develops from a sporocyst or redia in snail intermediate hosts.
Cestode   Tapeworm.
Chronic   Long–standing; a chronic disease is one that develops slowly and persists for a prolonged time.
Colostrum   The first milk secreted at the end of pregnancy.
Complete metamorphosis   The process of development involving dissimilar larval, pupal, and adult stages; occurs in parasitic flies and fleas.
Coprophagous   Feeding on manure.
Copulation   Mating.
Cutaneous   Pertaining to the skin.
Cuticle   Outer layer ("skin") of a parasite.
Cysticercus   Infective stage of a Taenia tapeworm, consisting of a fluid–filled bladder with a single scolex on its inner wall. When found in the muscles of livestock, these small bladders cause the mottled appearance termed "measly" meat.
Definitive or principal host   Animal in which a parasite reaches sexual maturity.
Dermatitis   Inflammation of the skin.
Direct life cycle   Life cycle in which parasites do not require development within an intermediate host.
Ear canker   Acute inflammation of the ear and auditory canal.
Ectoparasite   A parasite that lives on the body surface of its host.
Eczema   Inflammation of the skin, often accompanied by itching, crusting, and scaliness.
Edema   Accumulation of fluid in the tissues or body cavities.
Embryonated egg   Egg which contains a formed larva.
Emphysema   Increased size of the tiny air spaces (alveoli) of the lung due to destruction of their walls, a condition which interferes with oxygen uptake by the blood.
Endemic   Present continually in a region or among a certain group of animals.
Endoparasite   A parasite that lives within the body of its host.
Engorgement   Distention of a feeding tick with blood; cannot occur in male hard ticks, which are totally covered by a hard body surface.
Enteritis   Inflammation of the intestine.
Epithelium   The tissue layer which covers the skin and lines the inner walls of many body organs, including the digestive tract.
Exudate   Leaking of fluid from injured tissue and blood vessels.
Feed efficiency   The efficiency with which an animal is able to use ingested nutrients for growth, milk or wool production
Festoon   Rectangular raised areas separated by grooves; occurs on the posterior edge of hard ticks of certain species.
Fibrosis   The formation of fibrous tissue, often as a response to tissue damage.
Gastritis   Inflammation of the stomach.
Generation time   The time required for completion of the entire life cycle of an organism.
Gravid proglottid   A mature tapeworm segment filled with eggs.
Helminth   General term for parasite worms, including nematodes, cestodes, and trematodes.
Haemorrhage   Bleeding.
Hermaphroditism   The presence of both male and female reproductive organs in the same organism, which may be capable of reproducing singly.
Heterogonic   Alternation of sexual with asexual reproduction in successive generations of an organism.
Hexacanth   (synonym: onchosphere) The motile, six–hooked, first–stage larva of certain tapeworms; stage which hatches from the cestode egg and infects the intermediate host.
Homogonic   Successive generations of an organism, which reproduce in the same manner.
Host–specific   Able to parasitise only certain species of animals
Hydatid cyst   The infective stage of the Echinococcus tapeworm, which forms a fluid–filled bladder with many invaginated scolices. Parts of the wall pinch off within the capsule and form secondary cysts, or "brood capsules," each with several scolices. A single hydatid cyst can contain thousands of potential tapeworms. Hydatid cysts are found in humans and livestock.
Hypobiosis   Arrested growth or development of larval or adult parasites.
Immunity   Resistance to a disease or infection.
Incomplete metamorphosis   The development of some arthropods from eggs to adult–like nymphs, which moult to become adults. Characteristic of ticks, mites and lice.
Indirect life cycle   Life cycle in which immature parasitic forms must develop to the infective stage inside an intermediate host.
Inflammation   General response of organisms to irritation or injury. The process is characterised by increased blood supply to the area; signs include reddening, swelling, raised temperature, and pain.
Inornate tick   Solid–colored; nonpatterned.
Insect   Arthropod with distinct head, thorax, and abdomen. One pair of antennae is present on the head and three pairs of legs on the thorax. Wings may or may not be present.
Intermediate host   A host that is necessary for part of the development of an immature parasite.
Iron–deficiency anaemia   Anaemia produced by lack of sufficient iron reserves to replace iron in lost blood.
Jaundice   A condition which can result from damage to the liver; characterised by yellowish skin and whites of the eye.
Lumen   The space in the interior of a hollow organ.
Lymph   A clear fluid that normally seeps from capillaries into body tissues, flows in the lymph vessels, and is eventually returned to the blood.
Mange   Skin disease caused by mites; often produces an expanding area of scabby skin which has lost its hair.
Metacercaria   The infective stage of a fluke enclosed in a protective cyst that resists adverse environmental conditions. This stage develops from the cercaria and is infective for the principal host.
Metacestode   Immature tapeworm which develops from the hexacanth embryo and grows in the intermediate host (mammal).
Microfilaria   Stage of filarial worm transmitted to the biting insect from the principal host.
Miracidium   The first developmental stage larva of a fluke which hatches from the egg and penetrates the intermediate host.
Moulting   Process of growth in which a new, expandable skin is formed beneath the old one; the original skin is shed, allowing the parasite to expand in its new skin.
Morbidity   The amount of sickness caused by a disease.
Mortality   The death rate caused by a disease.
Mucosa   The inner layers of the wall of the digestive tract, mucous membranes.
Myiasis   Invasion of body tissues by parasitic fly larvae.
Necropsy   Autopsy; postmortem examination.
Nematodes   Parasitic worms of the class Nematoda, which includes the intestinal roundworms, filarial worms, lungworms, kidney worms, heartworms, etc.
Nit   Louse egg.
Occult infection   Hidden infection; one in which no eggs or larvae are produced. For example, infections can be occult when only worms of one sex are present of a species that requires mating to produce eggs or larvae. (See hypobiosis.)
Oncotic pressure   The force exerted by proteins to draw tissue fluids into the blood.
One–host tick   Tick that completes all its moults on the same individual host animal.
Operculum   Lid or cap–like structure at one or both ends of certain worm eggs, i.e., Trichuris and fluke; the larval parasite emerges from the egg at the operculum.
Organophosphate   A substance that can interfere with the function of the nervous systems of some parasites and host animals by inhibiting the enzyme cholinesterase.
Ornate   Colored; patterned.
Ovoviviparous   Laying or deposition of an egg which contains a larva.
Parasite worry   Annoyance and nervousness caused by parasites.
Paratenic host   An animal that carries a parasite to the principal host. The parasite does not develop inside the paratenic host. The principal host may become infected by eating the infected paratenic host.
Parthenogenesis   The laying of fertile eggs by a female without the need for fertilization by a male.
Parturition   Giving birth.
Pasture rotation   Alternating the areas on which animals graze, allowing time for parasites contaminating pasture to die off before animals are grazed on that land again.
Prepatent disease   Disease produced by larval or immature adult parasites before the parasites are producing eggs.
Prepatent period   The period from the time larvae enter the host until the time the adult female worms begin to lay eggs.
Proboscis   The structure at the anterior end of an organism permitting attachment and/or feeding.
Proglottid   Tapeworm segment.
Pyriform (piriform) apparatus   The inner membrane of the eggs of certain tapeworms, which often is pear–shaped and bears hooks.
Rays   Finger–like structures which support the copulatory bursa.
Redia   Trematode stage in the intermediate host which develops from the sporocyst, and which becomes the cercaria. Rediae may have the ability to divide.
Rumen   The first of the four compartments of the stomach of a cow or sheep. The rumen is a large chamber that serves as a fermentation vat for microbial digestion of feedstuffs
Safe pasture   Pasture on which infective larvae are present in numbers below that necessary to damage animals.
Scolex (pl.: scolices)   The "head" of a cestode; the part which attaches to the host and generates proglottids.
Scutum   A hard plate or shield on the upper body surface behind the capitulum of hard ticks. The scutum is much more extensive in male than in female ticks.
Sebaceous gland   Oil glands of the skin and hair follicles.
Seed ticks   Tiny tick larvae before their first blood meal.
Segmented egg   Egg within which the inner mass has divided into cells.
Self–cure   Elimination of parasites from a host as the result of the development of immunity to the parasites.
Sheath   Outer protective layer; ensheathed larvae retain an unshed cuticle from a previous moult.
Site of predilection   The location in a host animal of adults of a given parasite type.
Somatic   Pertaining to the body tissues.
Somatic migration   Migration of larvae through the tissues of a host´s body.
Spicules   Long, slender, rigid structures at the posterior end of male nematodes; serve to align the male with the female and to keep the female genital pore open.
Sporocyst   Trematode stage which develops inside the intermediate host from the miracidium; may be capable of multiplication within the intermediate host.
Spring rise   The increase in egg production from worms in the spring months; leads to increased numbers of infective larvae on the pastures.
Sputum   Mucus coughed from the lungs.
Strike   Myiasis, particularly blowfly larval infestation of sheep
Strobila   Body of a tapeworm; composed of maturing proglottids.
Strongyle–type egg   Egg form laid by a number of nematodes of the order Strongyloidea, characterised by oval shape, a thin, smooth wall, and an inner segmented cell mass.
Subcutaneous   Under the skin.
Systemic   Distributed throughout the body, as in the blood.
Tertiary blowfly strike   Myiasis caused by blowfly larvae of species which lay eggs only on sheep having chronic infestation and primary and secondary blowfly larvae
Therapeutic index   The margin of safety of a drug; the difference between the dose that kills parasites and the dose that harms the host.
Three–host tick   Tick that seeks a new host animal for a blood meal after each of its three moults.
Tick paralysis   An ascending paralysis associated with the engorgement of female ticks; probably caused by a toxin in the saliva of a tick
Toxin   Poisonous or noxious material.
Trachea   Windpipe; extends from the mouth area to the lungs, where it connects with the bronchi.
Tracheal migration   Migration pattern characteristic of many nematode species. Larvae in the blood break through the lung alveoli walls into the airways and are coughed up and swallowed.
Transovarian transmission   Passage of a microorganism into eggs within an infected female host.
Transfer host   Paratenic host.
Trematode   Any parasitic animal organism belonging to the class Trematoda, including flukes.
Two–host tick   Tick that remains on one host for the larval and nymphal stages, drops off to moult to an adult, and seeks a second host on which to take another blood meal and copulate.
Unthrifty   Failing to grow or develop normally, because of disease.
Ventral   Lower, or toward the belly.
Viviparous   Giving birth to living young.
Warbles   Swellings under the skin produced by larvae of Dermatobia and Hypoderma flies.