I

I

I chemical symbol, iodine (L. iodum).

I_a antigen MHC class II histocompatibility antigens found primarily on B lymphocytes but also on some macrophages, T lymphocytes and skin.

I band the lighter colored cross-striation of muscle fibers; composed of filaments of actin.

I-cell disease see mucolipidosis II.

-ia word element, state; condition.

-iasis word element. [Gr.] condition, state.

IATA International Air Transport Association; administers the Live Animals Regulations, which is the global standard for transporting live animals by commercial airlines, ensuring safe and humane transport.

iatric [i-at′rik] pertaining to medicine or to a physician. Also loosely construed to include veterinary medicine and veterinary physicians, e.g. buiatrics.

iatr(o)- word element. [Gr.] medicine, physician.

iatrogenic [i-at″ro-jen′ik] resulting from the activity of a veterinarian; said of any adverse condition in a patient resulting from treatment by a veterinarian, for instance, death after injection of an inappropriate solution or of an appropriate solution in an inappropriate manner, e.g. rapid injections of solutions of magnesium salts, unbuffered solutions of high alkalinity or acidity, or of a substance to which the animal is allergic. See also iatrogenic hyperadrenocorticism.

IACuC Institutional Animal Care and Use Committee.

Ibaraki disease see Ibaraki virus.

Ibaraki virus an orbivirus which causes a disease of cattle in Japan characterized by fever, anorexia and difficulty swalowing. See also epizootic hemorrhagic fever.

IBD 1. infectious bursal disease of chickens. 2. inflammatory bowel disease.

ibex wild goats of the genus Capra; males have a sizeable beard and long, thick, curved horns with transverse ridges or rings. They are hunted for trophy horns and some species are endangered.

Ibizan hound a medium-sized (22–27 inches tall), very lean, muscular dog with a short or wire-haired coat of white, chestnut or lion (light yellowish-red). The ears are very large, thin, erect and highly mobile, the head long and flat, and the tail long and thin. Overall, there is a deer-like appearance. The breed was an ancient Egyptian hunting dog but in recent times, considered to orginate in Spain.

IBK see infectious bovine keratoconjunctivitis.

ibotenic acid [i″bo-ten″ik] the insecticidal agent in the mushroom Amanita muscaria.

IBR see infectious bovine rhinotracheitis.

IBR/IPV see infectious bovine rhinotracheitis/infectious pustular vulvovaginitis.

ibuprofen [i′″bu-pro′fn] a nonsteroidal anti-inflammatory agent that possesses analgesic and antipyretic activities; used for symptomatic relief of rheumatoid arthritis and osteoarthritis in humans, but its use in dogs is limited by the occurrence of severe side- effects such as gastrointestinal hemorrhage.

IC inspiratory capacity.

i.c. medical record abbreviation for intracardiac.

-ic suffix meaning pertaining to.

iCa ionized (blood) calcium.

-ical suffix meaning pertaining to.

ICAMs intercellular adhesion molecules.

ICD 1. International Classification of Diseases (of the World Health Organization). 2. intrauterine contraceptive device. 3. isocitrate dehydrogenase.

ice plant [īs] see Mesembryanthemum.

Icelandic cattle usually polled, mostly red or red and white dairy cattle.

Icelandic pneumonia see maedi.

Icelandic horse, pony a sturdy horse, averaging 13–14 hands high in many colors; derived from North British ponies brought by the Vikings. They typically have five gaits: walk, trot, gallop, toelt, and pace.

Icelandic sheep multipurpose, usually white with light brown head and legs; sometimes black, gray or pied; horned.

Icelandic sheepdog a medium-sized, spitz-type dog with erect ears, thick double coat of either medium or long length that is predominantly tan, brown, gray or black with white markings. The tail curled over the back. Called also Iceland spitz.

ICG indocyanine green.

ICH infectious canine hepatitis.

Ich [ik] see Ichthyophthirius multifiliis and Cryptocaryon irritans.

ichor a watery discharge from wounds or sores.

ichorrhea copious discharge of ichor.

Ictadenovirus a genus in the family Adenoviridae that contains a virus isolated from sturgeon.

ichthammol [ik′thm-ol] an ammoniated coal tar product, used as an ointment in the treatment of acute, septic lesions such as cellu- litis and abscesses, and for a variety of skin conditions.

ichthyismus ichthyotoxism.

Ichthyoboda a genus of small, flagellate protozoan parasites of the skin of freshwater and marine fish. Cause a steel-gray discoloration of the skin and often respiratory distress.

ichthyoid [ik′the-oid] fishlike.

ichthyology [ik″the-ol′-je] the study of fishes.

ichthyophagous [ik′the-of-gs] eating or subsisting on fish.

ichthyophoniasis see Ichthyophonus.

Ichthyophonus a genus in the class Mesomycetozoea causing ichthyophoniasis, cutaneous ulcers and cysts in most body organs, of aged aquarium and wild fish.

Ichthyophthirius [ik″the-o-thi′re-s] a genus of protozoan parasites in the phylum Ciliophora.

I. multifiliis causes white spot disease or Ich in freshwater fish in aquariums and hatcheries. Characterized by white nodules on the skin; these may coalesce and cause sloughing of the skin and many affected fish die. Affects also the gills leading to respiratory distress.

ichthyosarcotoxin [ik″the-o-sahr′ko-tok″sin] a toxin found in the flesh of poisonous fish.

ichthyosarcotoxism [ik″the-o-sahr-ko-tok′siz-m] poisoning due to ingestion of poisonous fish, marked by various gastrointestinal and neurological disturbances.

ichthyosis [ik″the-o′sis] a rare congenital disorder of keratinization in dogs, cats, calves and swine, characterized by adherant scales covering the body. Hyperpigmentation, alopecia, lichenification, fissures and secondary infection may occur. Called also fish scale disease.

inherited congenital i. alopecia and plates of horny epidermis over the entire skin surface. Seen in calves at birth and they are not viable. Also occurs in dogs. Called also fish scale disease.

I-1: Icelandic pony.

From Sambraus HH, Livestock Breeds. Mosby, 1992.

Ichthyospofidium obligate, intracellular protozoan parasites in the class Microsporea.

I. giganteum found in the connective tissue of the body wall of fish, causing large ventral swellings full of cysts.

ichthyotoxin [ik′the-o-tok″sin] any toxic substance derived from fish. See also ichthyosarcotoxin.

ichthyotoxism [ik″the-o-tok′siz- m] any intoxication due to an ichthyotoxin.

icosahedral [i″ko-S-he′drl] a regular polyhedron with 20 triangular faces, 12 corners and 30 sides, having cubic symmetry with 5:3:2- fold axes. A common structural form for the capsid of many viruses including herpesviruses, adenoviruses, parvoviruses, reoviruses, picornaviruses and retroviruses.

ICP intracranial pressure.

ICSH interstitial cell-stimulating hormone. See luteinizing hormone.

ICSI intracytoplasmic sperm injection. The process of fertilization in vitro by microinjection of a single spermatozoa into the matured oocyte.

ictal [ik′t l] pertaining to or characterized by a seizure.

Ictalufus a genus of catfish in the family Ictaluridae. Includes I. punctatus (channel catfish) and I. furcatus (blue catfish).

icteric [ik-ter′ik] pertaining to or affected with jaundice.

icteroanemia [ik″t r-o--ne′me-] jaundice with mucosal pallor as in hemolytic anemia; see also eperythrozoonosis.

icterogenic [ik″t r-o-jen′ik] causing jaundice, e.g. icterogenic hepato- pathy.

icterogenins pentacyclic triterpene acid hepatoxins present in the plant Lippia rehmanni. Cause cholestasis and photosensitization.

icterohepatitis [ik″tr-o-hep″-ti′tis] inflammation of the liver with marked jaundice.

icteroid [ik′t r-oid] resembling jaundice.

icterus [ik′tr-s] see jaundice.

i. index is the density of color of the serum of an icteric patient compared to the standard solution. A rough measure of severity of hepatic insufficiency.

ictus [ik′ts] a seizure, stroke, blow, or sudden attack.

ICU see intensive care unit.

ID 1. infective dose. 2. L-iditol dehydrogenase.

ID₅₀ median infective dose; the dose that will infect 50% of the experimental group.

id see dermatophytid.

-id [Gr.] a suffix meaning having the shape of, or resembling.

idarubicin [i″d-roo′b-sin] an anthracycline antibiotic used as an antineoplastic agent; similar to doxorubicin.

idazoxan an α₂-adrenoceptor antagonist used to reverse xylazine.

IDDM insulin-dependent diabetes mellitus.

-ide suffix indicating a binary compound.

identical twins see monozygotic twins.

identification [i-den″t-f-ka′shn] a description of an animal sufficient to distinguish it from others. The means of identification include a written description, earmark, paint brand or paper or fabric applied by special adhesive, freeze branding and fire branding (see brand), tattooing, neckbands, ankle bands, ear tagging, tail tagging and tail painting, and electronic identification systems including activated responders or transponders carried on the animal, often subcutaneously. See also microchip.

electronic i. electronic devices, such as transponders, carried by animals that allow their identification; used widely in domestic animal control programs to permanently record ownership and facilitate recovery of lost animals. See also microchip. In agricultural animals, they permit identification and farm origin from a distance, such as sale yards. They can also be used on-farm to trigger off sensitometers, thus recording the animal’s feed consumption, milk yield and identity.

intraruminal i. bolus contain passive radiofrequency responders for individual animal identification. Used in sheep and cattle.

patient i. an adequate identification includes species and breed, sex, color and markings, brands and other distinguishing marks or attachments, whether horned or polled where appropriate, age, name or number used by the owner, and name and address of the owner or custodian.

national farm animal i. national programs that allow identification and traceability to enhance animal disease monitoring, surveillance of disease, and control and eradication of animal and zoonotic disease.

identity [i-den′t-te] the aggregate of characteristics by which an individual is recognized.

idio- word element. [Gr.] self, peculiar to a substance or organism.

idiocy a state of severe mental retardation, difficult to determine in an animal but typical examples are calves with hydranencephaly, yearling cattle with polioencephalomalacia.

juvenile amaurotic familial i. see amaurotic familial idiocy.

Idiogenes a genus of tapeworms of bustards belonging to the family Paruterinidae.

idiogram [id′e-o-gram″] a drawing or photograph of the chromosomes of a particular cell.

idiopathic [id″e-o-path′ik] self-originated; occurring without known cause.

idiopathy [id″e-op′-the] an undiagnosed morbid state arising without known cause.

Idiospermum australiense Australian rainforest tree in the family Idiospermaceae; fruit contains the toxic pyrrolidinoindoline (indole) alkaloid, idiospermuline; eating the fruit causes a syndrome of tetanic convulsions, hypersensitivity; called also idiot fruit.

idiosyncrasy [id″e-o-sin′kr-se] 1. a habit or quality of body or behavior peculiar to any individual animal. 2. an abnormal susceptibility to an agent (e.g. a drug) that is peculiar to the individual animal.

idiot fruit see Idiospermum australiense.

idiotope [id′-o-tōp″] an antigenic determinant on the variable region of an antibody.

idiotrophic [id″e-o-tro′fik] capable of selecting its own nourishment.

idiotype (Id) [id′e-o-tīp′] the antigenic characteristics of the variable region of an antibody. A set of idiotopes.

cross-reacting i. (IdX) one that is present on other anibodies produced in response to the same antigen, permitting a cross reaction. See also cross-reaction.

idioventricular pertaining to the cardiac ventricle alone.

L-iditol dehydrogenase see L-iditol dehydrogenase.

IDL intermediate density lipoprotein formed during the metabolism of very low density lipoprotein (VLDL) to low density lipoprotein (LDL).

idopsin a visual pigment in the cone membranous lamellae of the eye.

idoxuridine [i-doks-ūr′-dēn] a pyrimidine analog that prevents replication of DNA viruses; used topically in infection by herpes- viruses.

IDR insect development inhibitor; idiosyncratic drug reaction.

IDST intradermal skin test.

IDU see idoxuridine.

iduronic acid [i″du-ron′ik] major uronic acid component of the dermatan sulfate and heparin molecules; also present in heparan sulfate.

iduronidase deficiency [i″du-ron′-dās] see mucopolysaccharidosis I.

α-L-iduronidase enzyme involved in the breakdown of dermatan sulfate and heparan sulfate; deficiency is considered to be counterpart of mucopolysaccharidosis in cats and dogs; a neuronal storage disease.

IDV intermittent demand ventilation.

IEWG International Elbow Working Group.

IF intermediate filaments.

IFA test indirect fluorescent antibody test.

IFLUTD idiopathic feline lower urinary tract disease

IFN interferon.

iforrestine heterocyclic nephrotoxin in Isotropis spp.

ifosfamide [i-fos′f-mīd] a nitrogen mustard alkylating agent used in cancer chemotherapy. It is given combination with the thiol drug mesna to avoid the development of sterile hemorrhagic cystitis. Used in dogs and cats for the treatment of sarcomas, including feline vaccine-associated sarcoma.

Ig immunoglobulin of any of the five classes: IgA, IgD, IgE, IgG and IgM.

IgA immunoglobulin A. See immunoglobulin.

IgD immunoglobulin D. See immunoglobulin.

IgE immunoglobulin E. See immunoglobulin.

IGF-I insulin-like growth factor I. See somatomedin C.

IgG immunoglobulin G. See immunoglobulin.

IgM immunoglobulin M. See immunoglobulin.

IgM deficiency occurs as an inherited defect and as part of the primary severe combined immunodeficiency in Quarter horses and Arabian horses.

ignipuncture [ig′n-punk″chr] therapeutic puncture with hot needles.

Ignis sacer [ig′nis] see rye ergot¹.

IGR insect growth regulator.

iguana lizards in several genera in the family Iguanidae; characterized by the a long, whiplike tail with row of prominent spines down the back. They have an extendible dewlap and a photosensitive organ on the head, which is sometimes called a ’third eye’, or ’parietal eye’ (seen also in the tuatara). The green iguana (Iguana iguana) is common and popular as a pet.

IgY immunoglobulin Y, the avian equivalent of IgG; found in chicken yolk.

IHA isoimmune hemolytic anemia. See alloimmune hemolytic anemia of the newborn.

IHA indirect hemagglutination.

IK immunoconglutinins.

IL interleukin.

IL-1 interleukin-1.

IL-I catabolin.

Ile isoleucine.

ileac [il′e-ak] 1. of the nature of ileus. 2. pertaining to the ileum.

ileal, ileac [il′e-l] pertaining to the ileum. i. atresia see inherited alimentary tract segmental atresia. i. conduit use of a segment of the ileum for the diversion of urinary flow from the ureters.

i. muscular hypertrophy a cause of chronic or intermittent colic of horses characterized by loud ileocecal gut sounds and a palpably enlarged terminal ileum on rectal examination. Hypertrophy of the circular and longitudinal muscular layers results in narrowing of the intestinal lumen and partial or complete obstruction. Also recorded as occurring in the duodenum of horses. See also intussusception.

transmissible i. hypertrophy see wet tail.

ileitis [il″e-i′tis] inflammation of the ileum or distal portion of small intestine, manifested by chronic or intermittent diarrhea and weight loss.

granulomatous i. see granulomatous enteritis.

proliferative i. 1. see porcine proliferative enteropathy. 2. see wet tail of hamsters.

regional i. see terminal ileitis (below).

terminal i. a disease of young animals including pigs, lambs and horses characterized by illthrift and sometimes diarrhea. transmissible i. see wet tail.

ile(o)- word element. [L.] ileum.

ileocecal [il″e-o-se′kl] pertaining to the ileum and cecum.

i. valve the valve, or ileal papilla guards the opening between the ileum and cecum. In most species, the position, or papilla, where the ileum joins the large intestine marks an arbitrary T-shaped junction beetween cecum and colon, where the stem of the T indicates the ileum and the two arms of the T the cecum and colon. In horses, the entrance of the ileum is directly into the cecum. Called also ostium ilealis, ileocolic valve.

i. valve frenulum a fold of the large intestine mucosa attached to the ileal papilla; see retinaculum morgagni.

i. valve impaction is common in horses as result of feeding on finely chopped indigestible roughage. Causes mild colic initially, followed by evidence of acute intestinal obstruction. Fatal without surgical correction. See also intestinal obstruction colic.

ileocecocolic, ileocaecocolic pertaining to the combined ileum, cecum and colon.

ileocecostomy [il″e-o-se-kos′t-me] surgical anastomosis of the ileum to the cecum.

ileocolic [il″e-o-kol′ik] pertaining to the ileum and colon. i. intussusception intussusception of the ileum through the ileocecal valve into the colon. May extend through the rectum, appearing as a rectal prolapse.

i. valve ileocecal valve.

ileocolitis [il″e-o-ko-li′tis] inflammation of the ileum and colon.

ileocolostomy [il″e-o-k-los′t-me] surgical anastomosis of the ileum to the colon.

ileocolotomy [il″e-o-ko-lot′-me] incision of the ileum and colon.

ileocystoplasty [il″e-o-sis′to-plas″te] repair of the wall of the urinary bladder with an isolated segment of the wall of the ileum.

ileocystostomy [il″e-o-sis-tos′t-me] use of an isolated segment of ileum to create a passage from the urinary bladder to an opening in the abdominal wall.

ileoileostomy [il″e-o-il″e-os′t-me] surgical anastomosis between two parts of the ileum.

ileorectal [il″e-o-rek′tl] pertaining to or communicating with the ileum and rectum.

ileorrhaphy [il″e-or′-fe] suture of the ileum.

ileoscope inspection of the lumen of the ileum, usually with a flexible endoscope.

ileoscopy inspection of the lumen of the ileum with an endoscope.

ileostomy [il″e-os′t-me] an artificial opening (stoma) created in the small intestine (ileum) and brought to the surface of the abdomen for the purpose of evacuating feces.

urinary i. use of a segment of the ileum as a stoma for the diversion of urinary flow from the ureters. See also ileal conduit.

ileotomy [il″e-ot′-me] incision of the ileum.

ileum [il′e-m] the distal portion of the small intestine, extending from the jejunum to the cecum. See also ileal.

duplex i. congenital duplication of the ileum.

i.-umbilicus fistula a persistent and patent Meckel′s diver- ticulum.

ileus [il′e-as] functional obstruction or failure of peristalsis. It frequently accompanies peritonitis, and usually results from disturbances in neural stimulation of the bowel. In the horse it is a major problem in the recovery period after surgical treatment for colic.

adynamic i. paralytic ileus.

dynamic i. spastic ileus.

functional i. paralytic ileus.

paralytic i. loss of all intestinal tone and motility as a result of reflex inhibition in acute peritonitis, from excessive handling during bowel surgery, prolonged and severe distention due to intestinal obstruction and in grass sickness of horses. The effect is the same as that of an acute intestinal obstruction. Called also ileus, adynamic ileus.

mechanical i. obstructive ileus.

obstructive i. a physical lesion accounts for the intestinal distention.

sentinel loop i. a distended intestinal loop caused by localized paralytic ileus, usually resulting from local infection or pain.

spastic i. persistent contraction of a segment of ileum, effectively causing an obstruction.

Ilex [i′leks] a plant genus in the family Aquifoliaceae; includes I. aquifolium (holly); berries contain saponins and cause vomiting and diarrhea.

iliac [il′e-ak] pertaining to the ilium.

i. artery thrombosis in horses an acute onset is characterized by severe pain, even recumbency, and marked reduction of the amplitude of the digital arterial pulse. The affected limb is cold and is not used. The chronic disease is characterized by increasing weakness of the affected limb as exercise progresses. In both forms there is a unilateral abnormality of the iliac artery palpable per rectum. Dogs and, more commonly, cats are affected by thrombosis of the aorta (saddle thrombus) or an iliac artery, usually in association with cardiac disease, particularly cardiomyo- pathy. Depending on the rate of development, the affected limb becomes weak, cold and painful, the pulse is weak, and the animal becomes distressed. See also aortic embolism.

iliadelphus [il″e--del′fs] iliopagus.

ilial iliac.

ili(o)- word element. [L.] ilium.

iliocaudal muscle [il″e-o kaw′dl mus′l] the more cranial of the two of the levator ani muscles; it originates on the medial surface of the body of the ilium and inserts on the ventral aspect of the tail.

iliofemoral [il″e-o-fem′or-l] pertaining to the ilium and femur.

ilioinguinal [il″e-o-in′gw-nl] pertaining to the iliac and inguinal regions.

iliolumbar [il″e-o-lum′br] pertaining to the iliac and lumbar regions.

iliopagus [il″e-op′-gs] symmetrical conjoined twins united in the iliac region.

iliopectineal [il″e-o-pek-tin′e-al] pertaining to the ilium and pubes.

iliotrochanteric [il″e-o-tro-kan-ter′ik] pertaining to the ilium and femoral trochanters.

ilium [il′e-dm] pl. ilia [L.] the cranial portion of the hip bone. See also Table 10.

Ilizarov external ring skeletal fixation a device for stabilization of fractures using an external circular frame and a series of wires, nuts, bolts and rods.

illacrimation [hlak″rima′shn] see epiphora.

Illawarra cattle Australian red or red roan dairy cattle. Called also Australian milking shorthorn, Australian Illawarra shorthorn, AIS.

Illinois semen diluent used in the storage of boar semen; saturated with CO₂ it will store semen for days. Called also Illinois Variable Temperature Semen Diluent.

Illinois sternal needle a needle with a screw-in stylet, large hub and guard used for aspiration of bone marrow.

illness [il′nis] a subjective state in a human marked by feelings of deviation from the normal healthy state; a term not thought to be applicable to animals.

illthrift [il thrift] failure to grow, increase in weight or maintain weight in the presence of apparently adequate food supplies and in the absence of recognizable disease. See also weaner illthrift.

illumination [-loo″m-na′shn] the lighting up of a part, cavity, organ or object for inspection.

darkfield i., dark-ground i. the casting of peripheral light rays upon a microscopic object from the side with the object becoming visible as a result of its refraction of the light; the object appears bright on a dark background.

illuminator [-loo″m-na′tr] the source of light for viewing an object; the light source used to aid visualization through an endoscope, usually using a Xenon or Halogen lamp.

ILT infectious laryngotracheitis.

IM intramuscularly.

im- a prefix, replacing in- before words beginning b, m and p.

image [im′j] the picture reproduced on the X-ray film or by other radioimaging methods such as ultrasonography.

i. amplifier system includes amplifer and viewer or television camera and tape player.

digital i. see digital image.

i. display modes see ultrasonography, A-mode, B-mode and M- mode.

i. formation exposure of the film to the X-ray beam ionizing radiation or to other radiant energy forms causes ionic changes in the silver bromide crystals in the film emulsion so that it acquires a silver atom. It is the deposition of reduced silver atoms in particles or zones that causes the black zones or foci on the film. The amount of silver deposited depends on the intensity of the initial radiation X-ray exposure.

i. intensification a technique used to increase the brightness of the image while maintaining its sharpness. Used particularly in fluoroscopy and viewing directly or indirectly through a television camera and monitor, cineradiography, videotape or split-film device.

latent i. the invisible picture on the film after it has been exposed to the X-ray beam. It requires exposure to a developer and fixer before the image is visible and permanent.

i. level the mid-point brightness value of a computer display; the image level is adjusted to whiten or darken the image on a computer monitor.

weak i. said of X-ray films which lack density due to underexposure, too brief period of development, insufficient developer or developer temperature too low.

i. window determines the range of pixel values about which the image level will be displayed so controlling the image contrast.

imaging [im′-jing] the production of diagnostic images, e.g. radiography, ultrasonography, computed tomography, magnetic resonance imaging or scintigraphy.

digital i. a computer graphic file made up of a matrix of picture elements (pixels).

electrostatic i. a method of visualizing deep structures of the body, in which an electron beam is passed through the patient and the emerging beam strikes an electrostatically charged plate, dissipating the charge according to the strength of the beam. A film is then made from the plate.

gray-scale i. see gray scale ultrasonography.

nuclear i. see scintigraphy.

organ i. outlining the size and location of organs by the injection of nuclides into the animal and observing their location by the use of a rectilinear scanner or a scintillation camera. See also scintigraphy.

imago [i-ma′go] pl. imagoes, imagines [L.] the adult or definitive form of an insect.

imbalance [im-bal′ns] lack of balance; especially lack of balance between muscles, as in insufficiency of ocular muscles.

autonomic i. defective coordination between the sympathetic and parasympathetic nervous systems, especially with respect to vasomotor activities.

sympathetic i. vagotonia.

vasomotor i. autonomic imbalance.

imbecile an animal in a continuous state of imbecility.

imbecility a state of mind in which an animal does feeble, weak, absurd things and does not respond to usual environmental stimuli. Usually congenital. See also hydranencephaly, encephalopathy.

imbibition [im″b-bish′n] absorption of a liquid.

imbricated [im′br-kāt″d] overlapping like shingles or roof slates or tiles.

imbrication [im″br-ka′shn] surgical pleating and folding of tissue to realign organs and provide extra support, e.g. chronically stretched joint capsule.

Flo i. a method for repair of cranial cruciate repair in the dog in which sutures are placed around the patellar tendon and the fabellae.

IMHA immune mediated hemolytic anemia.

imidacloprid a neonicotinoid used topically on dogs and cats for its sustained adulticidal activity against fleas.

imidazoles [im″id-az′ōl] a class of synthetic antifungal agents with a five-ring heterocyclic ring structure; includes clotrimazole, miconazole, econazole and ketoconazole.

imidazothiazoles a group of broad-spectrum anthelmintics including butamisole and levamisole.

imide [im′id] any compound containing the bivalent group -CONHCO-.

imidocarb [imĩ-do-kahrb] an antiprotozoal agent, used as the hydro- chloride or dipropionate, in the treatment of babesiosis and ehrlichiosis.

imino acid [im′-no] proline or hydroxyproline, the two amino acids in which the amino group is part of a closed ring.

imipenem [im″-pen′m] one of the carbapenem class of antibiotics which are β-lactamase resistant. It has a very wide spectrum, but is inactivated by renal tubular enzymes and is given in association with cilastatin, which inhibits renal metabolism.

imipramine [-mip′r-mēn] a tricyclic antidepressant used in the treatment of behavior disorders and urinary incontinence in dogs.

imiquimod [im″-kwim′od] a topical immune response modifier with antiviral and antineoplasia effects. Used in veterinary medicine to treat squamous cell carcinomas, viral papillomas, feline cutaneous herpesvirus infection, and sarcoid and aural plaques in horses.

immature [m″-ch r′] unripe or not fully developed.

immediate [-me′de-t] direct, precipitating or primary; having no intermediate stage or mechanism, e.g. direct cause, immediate variant.

immersion [-mur′zhn] 1. the plunging of a body into a liquid. 2. the use of the microscope with the air between specimen and front objective lens replaced by a liquid, either immersion oil or water.

i. chilling method used for chilling poultry carcasses with iced water to ensure rapid cooling immediately after slaughter.

i. foot a condition similar to immersion foot in humans has been reported in cattle standing in cold water for days. There was erythema, edema and pain, followed by necrosis and sloughing of tissue.

i. syndrome vagal reflex, induced by contact with very cold water, causes cardiac arrest and death.

immiscible [-mis′hbl] not susceptible to being mixed.

immobility [-″mo-bil′-te] standing still and disinclined to move, as in an animal suddenly blinded; responds to other stimuli unless immobility is part of a dummy syndrome when all stimuli are ignored.

immobilization [-mo″bil--za′shn] the rendering of a part incapable of being moved.

i. band see compression band.

electrical i. pulses of low voltage current are passed through the skin and through the body. It causes a tetanic immobilization but does not decrease pain perception.

immobilize [-mo′bil-īz] to render incapable of being moved, as by a cast.

immobilizing drugs see muscle relaxant.

Immobilon trade name for a muscle relaxant composed of a mixture of etorphine and a phenothioazine tranquilizer such as acepromazine or methotrimeprazine. Comes in two strengths, one for small animals and one for large animals.

immortality said of cell lines which are capable of undergoing an unlimited number of cell divisions.

immotile cilia syndrome congenital defect of ciliary movement recorded in dogs. See also primary ciliary dyskinesia, Kartagener’s syndrome.

immune [-mūn′] 1. being highly resistant to a disease because of the formation of humoral antibodies or the development of immunologically competent cells, or both, or as a result of some innate immune mechanism, such as interferon activities in viral infections. 2. characterized by the development of antibodies or cellular immunity, or both, following exposure to antigen. . produced in response to antigen, such as immune serum globulin. The essential feature of antibody and cell-mediated immunity is that they are highly antigen specific.

i. adherence the binding of antibody-antigen-complement complexes to complement receptors found on red blood cells, the result of which leads to clearance of immune complexes from the blood circulation.

i. competent an individual with a fully functional immune system.

i. complex see antibody-antigen complex.

i. complex disease disease induced by the deposition of or association with antigen-antibody-complement complexes in the microvasculature of tissues. Fixation of complement component C3 by the complexes initiates inflammation. See also serum sickness, hypersensitivity.

i. complex reaction type III hypersensitivity (1).

i. deficiency disease one in which animals have inadequate immune responses and so are more susceptible to infectious disease. The defect may be primary (inherited), or secondary (acquired) which usually develops after birth because of toxins or infectious agents. See also combined immune deficiency syndrome, hypogammaglobulinemia, agammaglobulinemia, inherited parakeratosis, Chediak-Higashi syndrome and canine granulocytopathy syndrome.

i. hemolysis see immune-mediated hemolytic anemia.

i. interferon see interferon.

i. modulator see immunomodulation.

i. reaction immune response.

i. reaction fever aseptic fever occurring in anaphylaxis, angioedema.

i. response the specific response to substances interpreted by the body as not-self, the result being humoral and cellular immunity. The immune response depends on a functioning thymus and the conversion of stem cells to B and T lymphocytes. These B and T lymphocytes contribute to antibody production, cellular immunity and immunological memory. See also humoral immunity.

i. response (Ir) genes see immune response genes.

secondary i. response see anamnestic response.

i. surveillance the detection by lymphocytes, especially T lymphocytes, of new antigens, particularly on tumor cells.

i. system consists of the primary lymphoid organs (thymus and Bursa of Fabricius or its equivalent (bone marrow) in mammals) and secondary lymphoid organs (lymph nodes, spleen and other lymphoid tissue).

i. tolerance see immunological tolerance.

immune-mediated caused by an unspecified immune reaction.

i.-m. contact hypersensitivity see allergic contact dermatitis.

i.-m. hemolytic anemia (IMHA) occurs in many species in which autoantibodies directed against red blood cells are produced. The most common immune-mediated disease of dogs; Cocker spaniels and English springer spaniels are predisposed. Different classes of immunoglobulins may be involved giving rise to differing clinical syndromes. Signs include pallor, lethargy, splenomegaly, and sometimes icterus, bilirubinuria and hemoglobinuria. There may also be an accompanying throm- bocytopenia with bleeding tendencies. Diagnosis is supported by a positive Coombs test. Called also autoimmune hemolytic anemia.

immunifacient producing immunity; said of diseases, such as strangles and salmonellosis, that produce immunity against reinfection, which lasts for some time after an infection.

immunity [-mu′n-te] 1. the condition of being immune; security against a particular disease; nonsusceptibility to the invasive or pathogenic effects of microorganisms or helminth parasites or to the toxic effect of antigenic substances. Called also functional or protective immunity. 2. responsiveness to antigen that leads to more rapid binding or elimination of antigen than in the nonimmune state; it includes both humoral and cell-mediated immunity (below). 3. the capacity to distinguish foreign material from self, and to neutralize, eliminate or metabolize that which is foreign (non-self) by the physiological mechanisms of the immune response. The mechanisms of immunity are essentially concerned with the body’s ability to recognize and dispose of substances which it interprets as foreign and sometimes harmful to its well- being. When such a substance enters the body, complex chemical and mechanical activities are set into motion to defend and protect the body’s cells and tissues. The foreign substance, usually a protein, is called an antigen, that is, one which generates the production of an antagonist. The most readily recognized response to the antigen is the production of antibody. The antigen-antibody reaction is an essential component of the overall immune response. Of equal or greater importance to antibody, particularly for some antigens, is the development of so-called cell-mediated immune response, which involves clonal expansion of specifically reactive T lymphocytes including cytotoxic T lymphocytes (T_c lymphocytes) which play a major role in eliminating the foreign antigens that are cell associated. Immunological responses in animals can be divided into two broad categories: humoral immunity, which refers to the production of antibody which becomes part of the body fluids (humors), especially serum, and cell-mediated or cellular immunity, which involves a variety of activities designed to destroy or at least contain cells that are recognized by the body as expressing foreign antigens on their cell surface, e.g. viral antigens. Both types of response are mediated by lymphocytes that originate in the bone marrow as stem cells and later are converted into mature cells having specific properties and functions.

acquired i. antigen specific immunity attributable to the production of antibody and of specific immune T lymphocytes (responsible for cell-mediated immunity), following exposure to an antigen, or passive transfer of antibody or immune lymphoid cells (adoptive immunity).

active i. that which follows exposure to an antigen; acquired immunity attributable to the presence of antibody or of immune lymphoid cells formed in response to antigenic stimulus. Called also adaptive immunity.

adoptive i. passive immunity of the cell-mediated type conferred by the administration of sensitized lymphocytes from an immune donor to a naive recipient.

artificial i. includes acquired (active) immunity produced by deliberate exposure to an antigen, such as a vaccine or the administration of antibody (passive).

cellular i. dependent upon T lymphocytes which are sensitized by first exposure to a specific antigen. Subsequent exposure stimulates the release of a group of substances known as lymphokines, such as interferon, and interleukins as well as direct killing by cytotoxic T lymphocytes.

functional i. see immunity (above).

humoral i. mediated by antibodies formed by antigen-specific B lymphocytes. Each B lymphocyte has monomeric IgM receptors which capture specific antigen, initiating production of the specific immunoglobulins. B lymphocytes activated by the presence of their specific antigen undergo transformation, lymphocyte blastogenesis, whereby they become metabolically active, divide, and some mature to plasma cells, which are major producers of antibodies. Some cel s revert to small lymphocytes, ’memory’ cells, and the expanded clone of these cells, on re-exposure to the antigen, undergo further lymphocyte blastogenesis, leading to further increased antibody production and numbers of memory cells. There are two types of humoral immune response: primary and secondary. The primary response begins immediately after the inital contact with an antigen; the resulting antibody, predominantly IgM, appears 48–72 hours later. The secondary response occurs within 24–48 hours and produces large quantities of predominantly IgG. The secondary response persists much longer than the primary response and is the result of repeated contact with the antigens.

I-2: General dynamics and characteristics of the primary and secondary antibody responses.

From Cunningham JG, Klein BG. Textbook of Veterinary Physiology, 4th Edition. Saunders, 2007.

herd i. a level of resistance in a herd or flock which is sufficient to prevent the entry of a particular disease into, or its spread within, the herd. The resistance may be innate, a genetically based resistance, or acquired as a result of previous exposure to the particular agent or of vaccination. The general usage of the term relates to the prevention of spread of infection at an epidemic level. So that in a herd in which there are 70–80% of immune animals there may be sporadic cases but the prevalence is unlikely to be significant. The same comments apply to larger populations, e.g. a wild animal or companion animal population which is really not managed as a herd.

’herd’ i. the same principles that apply in herds or groups of animals (see herd immunity above), also apply to human populations. The extra protection that exists when a disease cannot find enough unprotected hosts to infect, preventing outbreaks from taking hold.

innate i., native i., natural i. natural immunity resulting from the genetic makeup of the host, before exposure to an antigen.

lactogenic i. intestinal immunity associated with the presence of immunoglobulins in milk, particularly IgA and, of the agricultrual animals, most important in pigs. See also colostrum.

maternal i. that acquired by the neonate by transplacental transfer of immunoglobulins (primates) or from ingestion of colostrum (most other mammals) or via the yolk sac (birds). The placentation of all agricultural animals precludes trans-placental transfer of immunoglobulin and only 5–10% is transferred in dogs and cats. Passive transfer of maternal immunity is effected by the transfer of immunoglobulilns present in high concentration in the first milk, colostrum, through the intestine of the newborn. The success of this transfer is dependent upon the time after birth that colostrum is ingested (physiologically 24–36 hours, but effectively for adequate transfer, 8 hours after birth) and on the mass of immunoglobulin ingested which is determined by the concentration of immunoglobulin in colostrum and the amount of colostrum ingested. Failure of passive transfer results in a significant increase in risk for neonatal disease. Neonates that fail to acquire serum concentrations of IgG₁ greater than 10 mg/mL are at significantly higher risk of septicemic, enteric and respiratory disease. Failure of passive transfer occurs as a result of neonates sucking the dam or acquiring colostrum by artificial feeding too late in the absorptive process, or by receiving too little colostrum or receiving colostrum with low immunoglobulin concentration. See also passive immunity (below) and colostral immunoglobulin.

natural i. see innate immunity (above).

passive i. the transfer of antibodies from a donor in which they were produced to a recipient for temporary immunity. Can be in the form of serum or colostrum or yolk. Significant transplacental transfer of antibodies is found in primates, but does not occur in domestic animals. Passive immunity in domestic mammals comes via the colostrum, with its high concentration of antibodies, and the more than normally pervious epithelium of the neonate’s intestinal epithelium. In birds maternal antibody is transferred to the yolk, from where the developing chick embryo absorbs it from about day 11 of incubation. See also passive immunization.

protective i. see immunity (above).

transplacental i. see passive immunity (above).

immunization [im″u-n-za′shn] the process of rendering a subject immune, or of becoming immune. See also vaccination.

active i. stimulation with a specific antigen to promote an immune response. In the context of infectious diseases, the antigenic substances may include: (1) inactivated bacteria, as in botulism immunization; (2) inactivated viruses, as in the canine parvovirus vaccination; (3) live attenuated viruses, e.g. rabies virus; and (4) toxoids, chemically treated toxins produced by bacteria, as in immunization against tetanus and pasteurellosis. Any of a vast number of foreign substances may induce an active immune response. Since active immunization induces the body to produce its own antibodies and specifically reactive cells and to go on producing them, protection against disease may last several years, in some cases for life.

antihormone i. immunization against hormones, e.g. against androstenedione for the stimulation of multiple ovulations in ewes. See also immunological contraception.

deliberate i. the administration of an immunogen, usually by injection but sometimes orally or by inhalation, for the purpose of producing immunity.

natural i. stimulation of the immune system through exposure to antigens that have not been deliberately administered.

passive i. transient immunization produced by the introduction into the system of pre-formed antibody or specifically reactive lymphoid cells. The animal immunized is protected only as long as these antibodies or cells remain in the blood and are active — usually from 4–6 weeks. The immunity may be natural, as in the transfer of maternal antibody to offspring, or artificial, passive immunity following inoculation of antibodies or immune cells.

immunize [im′u-nīz] to render immune.

immunoabsorbent [im″u-no ab-sor′bnt] a preparation of antigen attached to a solid support or antigen in an insoluble form, which absorbs homologous antibodies from a mixture of immunoglo- bulins. See immunosorbent, ELISA.

immunoadjuvant [im″u-no-aj′-vnt] see adjuvant.

immunoassay [im″u-no-as′a] the quantitative determination of either antibody or antigen, e.g. hormones, drugs, vitamins, and specific proteins, by means of antigen-antibody interaction, as by agglutination, precipitation, ELISA, radioimmunoassay, etc.

immunoaugmentation [im″u-no awg′men-ta′shdn] to enhance immune response in a nonantigen specific manner by stimulating macrophage and reticuloendothelial function.

i. agents include BCG, mixed bacterial vaccine (MBV), and Cory- nebacterium parvum.

immunobiology [im″u-no-bi-ol′-je] that branch of biology dealing with immunological effects on such phenomena as infectious disease, growth and development, recognition phenomena, hyper- sensitivity, heredity, aging, cancer and transplantation.

immunoblast [im″u-no-blast′] lymphoblast. See also B immunoblasts.

immunoblastic [im″u-no-blas′tik] pertaining to or involving the stem cells (immunoblasts) of lymphoid tissue.

immunoblot [im′u-no-blot″] see Western blot.

immunochemistry [im″u-no-kem′is-tre] the study of the chemical basis of immune phenomena and their interactions.

immunochemotherapy [im″u-no-ke″mo-ther′-pe] a combination of immunotherapy and chemotherapy.

immunocompetence [im″u-no-kom′p-tns] the capacity to develop an immune response following exposure to antigen.

immunocomplex [im″u-no-kom′plks] immune complex.

immunocompromised [im″u-no-kom′pr-mīzd] having reduced immune responsiveness as a result of inherited defects or infection, particularly by retroviruses and herpesviruses or by administration of immunosuppressive drugs, including antilymphocyte serum, by irradiation, by malnutrition, and by certain disease processes, e.g. cancer.

immunoconglutinin [im″u-no-kn-gloo′t-nin] antibody formed against complement components that are part of an antibody-antigen complex, especially C3.

immunoconjugates [im″u-no-kon′ja-gāt] monoclonal antibodies which are target-specific carriers for specific compounds such as plant or bacterial toxins, radionuclides, photoactive agents and chemotherapeutic drugs.

immunocyte [im′u-no-sīt″] any cell of the lymphoid series which can react with antigen to produce antibody or to participate in cellmediated immunity; called also immunologically competent cell.

immunocytoadherence [im″u-no-si″to-ad-hēr′ns] the aggregation of red cells to form rosettes around lymphocytes with surface immunoglobulins.

immunocytochemical staining [im″u-no-si″to kem′-kl] see immuno- histochemical.

immunocytochemistry [im″u-no-si″to-kem′is-tre] see immunohisto- chemical.

immunodeficiency [im″u-no-d-fish′n-se] a deficiency in the immune system, either that mediated by antibody or T lymphocytes, or both. See also agammaglobulinemia, hypogammaglobulinemia, feline immunodeficiency virus, bovine immunodeficiency virus.

acquired i. see immune deficiency disease.

cancer-associated i. in general, associated with cachexia and debilitation, and also related to the type of neoplasia. Tumor- related effects on the immune system include impaired function of lymphocytes, altered cytokine production and activation of suppressor cell functions.

combined i. see combined immune deficiency syndrome (disease).

common variable i. a term encompassing a heterogeneous group of syndromes, which may be inherited or acquired, characterized by recurring persistent infections and deficiencies of some of the immunoglobulin classes.

congenital i. see immune deficiency disease.

i. disease see immune deficiency disease, combined immune deficiency syndrome (disease).

iatrogenic i. see secondary immune deficiency disease.

severe combined i. see combined immune deficiency syndrome (disease).

X-Iinked i. an inherited form of severe combined immunodeficiency that has been reported in dogs. Puppies fail to grow and die from overwhelming infections at an early age.

immunodepression [im″u-no-d-presh′n] see agammaglobulinemia, hypogammagIobuIinemia, immunodeficiency.

immunodermatology [im″u-no-dur″m-tol′-je] the study of immuno- logical phenomena as they affect skin disorders and their treatment or prophylaxis.

immunodiagnostic [im″u-no- di″g-nos′tik] pertaining to diagnosis by immune reactions.

immunodiffusion [im″u-no-d-fu′zhn] in vitro assays that involve the diffusion of antigen and antibody through a gel matrix such as agarose. For example, double immunodiffusion assays where antigen and antibody are placed in separate wells, cut in agar, such that precipitation lines form in the agar between the wells.

radial i. (Mancini technique) antigen diffuses into the agar which contains specific antibody and a ring of precipitate is formed, the diameter of which is directly proportional to the concentration of the antigen and can thereby be used to quantitate the amount of antigen. A reverse radial immunodiffusion test, in which antigen is incorporated in the agar, can be used to quanti- tate the amount of antibody in a sample.

i. tests include double immunodiffusion (Ouchterloney technique) which is used in the Coggins test for equine infectious anemia and single immunodiffusion (Oudin technique), as well as radial immunodiffusion.

immunodominance [im″u-no-dom′-nns] the property of an anti- genic determinant that causes it to be responsible for the major immune response in a host.

immunoelectrophoresis [im″u-no-e-lek″tro-f-re′sis] electrophoretic separation, usually in an agar gel, of complex mixtures of antigens which, following immunodiffusion, combine with antibody to forming precipitation lines for each separated antigen.

counter i. antigen and antibody are placed in separate wells, close together and oriented so that the electric field drives them together. When they migrate and meet, a line of precipitin is formed.

rocket i. electrophoresis in which antigen migrates from a well through agar gel containing antiserum, forming cone-shaped (rocket) precipitin bands; the area under the cone is used to calculate the amount of antigen.

immunofiltration [im″u-no-fil-tra′shdn] purification of antibodies by their binding to specific antigen immobilized on a solid phase; the antibody is eluted by denaturing treatments that interfere with antigen antibody binding. Called also affinity purification of antibodies.

immunofluorescence [im″u-no-fl-res′ns] a method of determining the location of antigen (or antibody) in a tissue section or smear using a specific antibody (or antigen) labeled with a fluoro- chrome. In the direct methods, the fluorochome is chemically linked to the specific antibody. In indirect methods, a labeled anti-immunoglobulin that binds to the specific antibody is used. See also fluorescence microscopy.

i. testing see fluorescence microscopy.

immunofluorescent see immunofluorescence.

i. antibody test see fluorescence microscopy.

i. microscopy see fluorescence microscopy.

immunogen [im′u-no-jn] substance that elicits an immune response.

immunogenetics [im″u-no-j-net′iks] the study of the genetic factors controlling the animal’s immune response and the transmission of those factors from generation to generation.

immunogenic [im″u-no-jen′ik] producing immunity; evoking an immune response.

immunogenicity [im″u-no-j-nis′ĩ-te] the ability of a substance to provoke an immune response or the degree to which it provokes a response.

immunoglobulin [im″u-no-glob′u-lin] a specialized class of serum proteins, which may occur naturally in serum, but are usually produced in response to exposure to foreign antigens. Called also antibody. Immunoglobulins combine only with the antigen (or one closely related to it) that elicited their production. Immuno- globulins are major components of what is called the humoral immune response system. They are synthesized by B lymphocytes and their derivative plasma cells, and are found in the serum and in other body fluids and tissues, including the urine, spinal fluid, lymph nodes and spleen. See also immunity. Immunoglobulin molecules consist of two kinds of polypeptide chains: heavy chains (H-chains) and light chains (L-chains). There are five antigenically different kinds of H-chains, designated 7, a, 6 and e, and this difference is the basis for the classification of immunoglobulins. Classes vary in their chemical structure and in the number of antigen-binding sites. The five classes of immunoglobulins (Ig) are: IgG, IgM, IgA, IgD and IgE. Only IgG, IgM and IgA are found in all species of domestic animals. IgA is present in low concentrations in the serum, but it is the major immunoglobulin of secretions and has a major first-line defense role in infections that enter via mucosal surfaces. Two IgA molecules are linked by a polypeptide called the secretory piece and by a J chain. Secretory IgA is present in nonvascular fluids, such as saliva, bile, synovial fluid, and intestinal and respiratory tract secretions. Both secreted and circulating IgA types are known to have antiviral properties; their production is preferentially stimulated by local administration of antigens such as oral and aerosol immunizations. IgD is found in trace quantities in the serum in humans and chickens. It is found on the surface of immature B lymphocytes, often simultaneously with IGM. Its function is uncertain. IgE, once called reaginic antibody, is present in very low concentrations in serum and is generally present in increased concentrations in individuals with allergy. It has not been found in the chicken. IgE binds to Fc receptors on the surface of cells particularly mast cells and basophils, via the Fc part of the molecule. Following exposure to antigen (allergen), and its binding to the Fab of two adjacent IgE molecules, perturbations of the cell membrane are produced, leading to the release of vasoac- tive amines, particularly histamine and serotonin, which are the mediators of anaphylaxis and atopic reactions, including urticaria, asthma, hayfever and gastroenteritis. It is recognized in humans and dogs that there is an inherited (familial) predisposition for certain individuals to produce IgE. IgG is the most abundant of the five classes of immunoglobulins, representing about 80% of serum immunoglobulin protein. It is the major antibody in the secondary humoral response of immunity, serves to activate the complement system, and is frequently involved in opsonization. IgG is the only immunoglobulin that crosses the placenta and is the major component of passive maternal antibody transfer via colostrum and yolk. The avian equivalent of IgG is termed IgY. IgM is the first antibody produced in the primary immune response. It represents about 20% of serum antibodies. Like the IgG, IgM bound to antigen activates the complement system, and together these two classes of immunoglo- bulins serve as specific antitoxins to neutralize diphtheria, tetanus, botulism and anthrax toxins and play a major role in defense against most infectious diseases.

I-3: Structure of an immunoglobulin molecule.

From Tizard IR, Veterinary Immunology. An Introduction, 6th Edition. Saunders, 2001.

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