Necropsy of Chickens, Turkeys, and Other Poultry

Necropsy Techniques

Necropsy of Chickens, Turkeys, and Other Poultry L. Dwight Schwartz, D.V.M., M.S.* and Arthur A. Bickford, V.M.D., Ph.D.t

The purpose of the postmortem examination (necropsy) is to determine illness or cause of death by examining the bird, the organs, and the tissues and to harvest specimens necessary for confirmatory procedures. The technique, or necropsy procedure, varies from person to person, but the goal-an accurate diagnosis-remains the same. Perhaps one of the most important things about the necropsy is evaluation of the lesions that are present and how specific lesions of one bird fit into the health problem of the flock. Seldom will a single bird exhibit all lesions typical of the flock problem. The professional opinion is strongly influenced by the quality and type of specimens submitted for examination. Many producers and servicemen are quite skillful in early recognition of poultry health problems in their flocks. Congenital and anomalous conditions can be explained to the client on an individual bird basis but usually do not pose a problem for the remainder of the flock. In contrast, infectious, parasitic, and nutritional conditions are flock-wide problems and must be dealt with accordingl y. . It is of interest and reassuring to the veterinarian in a mixed food animal practice to know that most disease processes in small farm poultry flock situations are single-entity, environmentally induced diseases, as opposed to "disease complexes," which are more prevalent in large commercial poultry flocks. This is not to say that concomitant infections do not occur in small flocks. They do occur, because the poultry farm flock possesses all of the disease susceptibilities of their commercial cousins. Lowered production pressure, multiple ages, multiple species, less tendency for ongoing medications, and less attention to vaccinations are conducive to per-

* Professor,

Animal Health Diagnostic Laboratory, Michigan State University College of Veterinary Medicine, East Lansing, Michigan t Veterinary Laboratory Services, Department of Food and Agriculture, Turlock, California

Veterinary Clinics of North America: FoodAnimal Practice-Vol. 2, No.1, March 1986.

43

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DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

Kidney

Lungs Ovary

~.;.;;:,j~-'4--I----+- Oviduct

Proventriculus Gall Bladder Spleen

Small Intestine

Duodenal Loop

NECROPSY OF CHICKENS, TURKEYS, AND OTHER POULTRY

45

petuation of endemic and environmentally induced maladies. In the commercial setting, poultry disease complexes result from multifactorial events associated with intensive poultry production practices. For example, average flock size has increased from a few hundred birds per flock to up to 100,000 birds per house and up to 1 million birds per farm. Other examples include floor pens to cages, genetic selection for high egg production and/or rapid growth, least-cost feed formulation, and intense vaccination programs. It is important to establish an orderly, consistent necropsy procedure and to evaluate the gross lesions as to their likely cause and significance. A very high percentage of farm flock poultry maladies can be diagnosed by gross lesions plus a few simple laboratory procedures, such as direct microscopy, Gram's stain, fecal flotation, and aerobic bacteriology. Many gross lesions are pathognomonic, such as lymphoid tumors or avian leukosis, clostridial diseases such as ulcerative lesions of the lower intestine of quail and chickens, clostridial and/or Eimeria necatrix ballooned necrotic intestine, slipped tendon (perosis) in young chickens, rickets, and vitamin A deficiency. Finally, it is appropriate to offer some commentary on why an article on the necropsy of poultry species is being offered in this publication. Veterinary involvement in avian diseases currently seems to be concentrated at two extremes: (1) attention to medical problems of individual household pet or zoo birds or (2) full-time service by highly trained veterinary specialists to commercial poultry flocks. There are substantial avian populations between these extremes that receive little recognition from the veterinary profession. These populations include backyard poultry (chickens, turkeys, and waterfowl), breeder stock maintained by bird fanciers, game birds (chukars, quail, pheasants, and so on) reared for hunting preserves or domestic markets, pigeons reared and maintained for pleasure, racing, or domestic markets, and so on. Practitioners willing to offer veterinary service to these populations could make a significant contribution to avian health and, in some areas, would uncover a sizable and most appreciative clientele. In any case, necropsy of dead or terminally ill birds is a key approach to disease diagnosis.

PRECAUTIONS The usual precautions with regard to use of sharp instruments during necropsy are in order as a safety reminder. Poultry necropsies can be done with a limited amount of instrumentation, and no special equipment is necessary. Most of the instrumentation will already be available in the practice. Suggested instruments for routine necropsy of poultry include disposable syringes with needles, blood tubes, 6inch knife or scalpel, necropsy shears, tissue scissors (preferably with sharplblunt blades), thumb forceps with teeth, and disposable gloves (either vinyl or latex). Inclusion of other instruments is optional. It is advisable to wear rubber or vinyl necropsy gloves in per-

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DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

forming necropsies of poultry, primarily to minimize odors and minor cutaneous infections of the hands. Most of the commonly diagnosed diseases of poultry are host specific and do not even cross species barriers within avian groups. It is to the veterinarian's advantage to have a working knowledge of host-specific infections as well as those infections that cross species barriers. Likewise, knowledge of zoonotic diseases of birds is essential to minimize self-exposure, to outline treatment and control programs for the clients, and to advise the client or consumer on determining the wholesomeness of home-dressed poultry. Zoonotic poultry diseases are essentially limited to chlamydiosis, equine encephalomyelitis (EE), erysipelas, and salmonellosis. Occasionally, under laboratory or other special situations, there are reports of humans ill with diseases of birds , such as Newcastle disease viral conjunctivitis in laboratory workers or chlamydial respiratory illness in workers in poultry slaughter plants. Newcastle disease virus (NDV) is not infectious to humans unless inoculated in the eye, after which a local conjunctival inflammation occurs. Similarly, chI amydiosis is not a common infection of domestic poultry; only turkeys are very susceptible. Therefore, handlers of live birds who load and unload these occasionally infected flocks are at risk for contracting the disease. The risk is not great during necropsy. In view of this, the veterinarian should exercise usual precautionary measures, such as dampening the table and the bird in a germicidal solution, wearing protective gloves for the necropsy, and sanitizing instruments after the necropsy. Disposable masks are available, too, for the person who is sensitive or allergic to feather dust. The mask would also offer protection against chlamydiosis in situations in which the case history indicates that it is a possibility.

ANAMNESIS Review the clinical history and consider all likely diagnoses. Not having seen the flock or the farm of origin, the veterinarian is at a disadvantage and consequently relies heavily on the flock history and description of the problem for completeness and accuracy. In addition, the situation, signs, and events should be reported chronologically as they were observed by the client, service person, or person who submitted the birds. The flock history should include the following: primary problem or complaint as the client sees it; species, number, age, sex, strain, and type of birds; vaccinations; ages and known endemic farm diseases; feeding program; feed consumption before and after onset of the problem; production before and after onset of the current problem; and mortality before and after onset of the problem. A good history provides several clues to the primary problem. Commercial-size flocks may have to be visited in order to identify and resolve the problem, especially if the flock does not respond to treatment based on the original diagnosis. A variety of negative environmental or managerial conditions can interfere with or even nullify

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response of the flock to medication; therefore, these conditions must be recognized and corrected in order to resolve the problem. Thorough questioning of the producer about chick source, hatching, brooding procedure, possible temperature stress (chilling or overheating) of chickens, and early chick/poult mortalities may provide the essential clue to the case. Several maladies of very young poultry fit into an age time frame of the chick. For instance, omphalitis is observed in the first week of life and is associated with dirty hatching eggs and unsanitary incubation and hatching. Salmonella infections, usually transmitted by egg, are observed after about 8 days of age. Epidemic tremor is also transmitted by egg and most likely will be observed at about 12 days of age in chickens. Coccidiosis, which is litter-borne, first appears at 21 days of age or later depending on the cleanliness of the broiler house and litter conditions. Questions that will determine age at the time of onset as well as signs and symptoms are extremely useful in history taking to categorize the nature and likely etiology of the condition. The history taker should learn what medications have been administered and the duration of treatment, including when or if medication had continued up to submission time. Many infections, such as salmonellosis and pasteurellosis, can be controlled, but not necessarily cured, by medications; however, medications will interfere with making a definitive diagnosis. When this occurs, the diagnostician should be prepared either to request a second submission if confirmatory tests and cultures are negative or to hold some of the birds off medication for 2 to 3 days and then post and culture for the pathogen in question.

ANTEMORTEM EXAMINATION All birds should be closely examined physically for any visible external lesions, such as those caused by trauma, tumors, and ectoparasites. Feathering, weight, and general appearance of the bird should be noted, including size and condition of comb, wattles, facial tissues and eyes, respiratory rales, dyspnea, nasal exudates, lacrimation, sinusitis, dehydration, and cyanosis of the skin and underlying tissue. Pigmentation of the beak and legs on laying hens should also be noted. Deformities, crippling, fractures, and contusions are important to detect before the bird is killed for necropsy. Many deformities are genetically predisposed, whereas conditions such as curled-toe paralysis, perosis (slipped tendon), and gout are more likely to be induced by poor nutrition. Fowl pox lesions on the face, comb, and unfeathered parts are a true pox caused by the fowl pox virus and, in small farm flocks, are almost entirely transmitted within the flock by mosquitoes or cannibalism. Fowl pox virus, an epitheliotropic virus, will not penetrate unbroken skin, except the conjunctiva. There is some debate among avian pathologists as to whether or not the pharyngeal form

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DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

(wet fowl pox) is caused by exposure to air-borne virus. However, that is not the important thing to debate in diagnostic cases. External parasites, including lice (head, body, and feather lice), mites (especially Northern fowl and scaly leg mites), and possibly ticks and/or bedbugs may be seen on the live bird. All poultry lice are biting insects and therefore are rather easily controlled with pesticide dusts. However, mites are arachnids and are more difficult to control and usually require several treatments of the birds and the poultry house. When a condition such as avian leukosis or avian encephalomyelitis is suspected, close scrutiny of the live bird is important. Leukotic birds may have lesions in the eye, and the comb, in advanced stages of the disease, is shriveled, scaly, and bright yellow to brick-colored. The bird will be emaciated, have ruffled feathers, paralysis of a leg or wing, and often green diarrhea. With avian encephalomyelitis, the bird may be normal in appearance, weight, and feathering, except that there may be hemorrhage in the eye and/or cataracts in one or both eyes.

COLLECTING BLOOD Equipment includes disposable syringes (2.5 to 3 ml), disposable hypodermic needles (about 21-gauge, 3/4 -inch long), and blood tubes. Blood samples from domestic birds are collected either from the wing vein or by cardiac puncture. Each person must develop a technique for the preferred procedure. There are several points to be considered: (1) Veins of birds are very thin-walled and venipuncture frequently results in a hematoma at the puncture site. (2) Veins in birds move around and must be steadied for successful venipuncture. (3) In a procedure that prevents hematomas, the needle is inserted under the tendons on the inner surface of the wing joint and the venipuncture is made from the back of the vein. (4) Blood samples can be collected by puncturing the wing vein with a stylus where it crosses the bony surface of the joint; the extravasated blood can be collected into a blood tube or vial. Cardiac puncture is most commonly used when the birds are to be killed and necropsied. Cardiac puncture is particularly useful in young, small birds or even adult chickens and game birds. Turkeys and many adult chickens have large wing veins; therefore, heart bleeding would not necessarily be an advantage. There are two approaches for cardiac puncture in birds. Anterior Approach

The anterior approach requires the needle to be inserted through the thoracic inlet and directed posteriorly and toward the tail in a plane that is in line with the keel (Fig. 1). A second person is needed to hold the bird. The bird can be positioned on the edge of the table with its head and neck held down at a sharp angle. A long or 2-inch needle is required. Cardiac puncture is through the auricle and into

NECROPSY OF OF CHICKENS, CHICKENS, TUI}KEYS, TURKEYS, AND AND OTHER OTHER POULTRY POULTRY NECROPSY

49 49

Figure 1. 1. Cardiac Cardiac puncture puncture via via anterior anterior approach. approach. Figure

the ventricle. ventricle. Gentle Gentle negative negative pressure pressure should should be be held held on on the the syringe syringe proceeds and and blood blood is is aspirated. aspirated. The The needle needle isis rereas the puncture proceeds as desired desired blood blood volume volume is is obtained. obtained. When When the the bird bird isis held held moved as bleeder, grasp grasp the the bird bird by by the the legs, legs, anchoring anchoring the the wings wings by bythe the by the bleeder, feathers into into the the same same hand hand to to control control flapping. flapping. With With the the bird bird in in aa feathers vertical, upside-down upside-down position, position, proceed proceed as as described described above. above. vertical,

Lateral Approach Approach Lateral Restrain the the bird bird in in lateral lateral recumbency recumbency on on the the right right side side on on the the Restrain necropsy table table or or on on another another suitable suitable flat flat surface surface at at aa comfortable comfortable necropsy height. The The bird bird is is restrained restrained by by an an assistant. assistant. The The wings wings are are working height. together, as as are are the the legs, legs, then then the the bird bird isis stretched stretched with with enough enough held together, tension to to be be taut taut in in case case of ofstruggle. struggle. The The position position and and restraint restraintof ofthe the tension determine the the location location of of the the heart heart in in relation relation to to landmarks. landmarks. bird determine Proper positioning positioning and and restraint restraint of ofthe the bird bird are are essential essentialfor forconsistent consistent Proper success of of cardiac cardiac puncture puncture by by this this route. route. Cardiac Cardiac puncture puncture isis quite quite success safe when when done done rapidly rapidly with with precision precision and and aanew, sharp hypodermic hypodermic new, sharp needle. The The landmarks landmarks for for insertion insertion of of the the needle needle are are the the anterior anterior needle. of the the sternum, sternum, the the anastomosis anastomosis of ofthe the superficial superficial pectoral pectoral vein, vein, point of the dorsal dorsal border border of of the the pectoral pectoral muscles. muscles. The The point point of of needle needle and the insertion is is into into the the groove groove formed formed by by the the dorsal dorsal border borderof ofthe thepectoral pectoral insertion muscles, about about 1.5 1.5 cm cm posterodorsal posterodorsal to to the the venous venous anastomosis anastomosis and and muscles, vertical plane plane that that intersects intersects the the point point in in line line with with the the sternum sternum on a vertical (Fig. 2). 2). Hold Hold the the syringe syringe in in aa vertical vertical position, position, insert insert the the needle needle into into (Fig.

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L. L. DWIGHT SCHWARTZ AND ARTHUR A.A.BICKFORD DWIGHT SCHWARTZ AND ARTHUR BICKFORD

Figure 2. 2.Cardiac puncture viavia lateral approach. Figure Cardiac puncture lateral approach.

thethe thoracic cavity, and penetrate thoracic cavity, and penetratethe thecardiac cardiacventricle. ventricle.Create Createnegnegative pressure in in thethe syringe and continue the ative pressure syringe and continue thethrust thrustinto intothe theventricle ventricle until blood flows into thethe syringe. Holding the until blood flows into syringe. Holding thesyringe syringemotionless motionlesswill will minimize damage to to thethe cardiac muscle. Aspirate toto2.5 blood, minimize damage cardiac muscle. Aspirate1.5 1.5 2.5mlmlofof blood, withdraw thethe needle, and inject the blood withdraw needle, and inject the bloodgently gentlyinto intothe theopen openblood blood tube. Stopper thethe tube, laylay it it flat, tube. Stopper tube, flat,and andallow allowthe theblood bloodtotoclot. clot. Euthanasia Euthanasia See thethe preceding article. See preceding article.

NECROPSY NECROPSY Necropsy of of a few dead-on-arrival Necropsy a few dead-on-arrival(DOA) (DOA)birds birdsmay maybebeadvisable advisable to to identify thethe nature lesions identify natureofof lesionsanticipated anticipatedininthe thelive liveand andfreshly freshly killed birds to to bebe used forfor bacteriologic killed birds used bacteriologicculturing culturingand andother otherconfirmconfirmatory clinical pathology. atory clinical pathology.The Theactual actualnecropsy necropsyprocedure procedurecan canbebeiniinitiated from either end ofof thethe bird-head oror abdominal tiated from either end bird-head abdominalend. end.Regardless Regardless of of which end of of thethe bird you start on,on,it it is isquite which end bird you start quiteimportant importanttotouse usethe the same approach same approachononevery everybird. bird.Most Mostpoultry poultrydiagnosticians diagnosticiansuse usethe the necropsy steps that areare essential to to confirm a diagnosis. necropsy steps that essential confirm a diagnosis.Although Althoughone one does have license to to omit certain ofof the does have license omit certain theprocedures, procedures,one onemust mustbebecaucautious notnot to to overlook steps that will reveal lesions tious overlook steps that will reveal lesionsthat thatare arekey keyfeatures features of of thethe problem. problem.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _i. . . .

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Figure 3. Position and procedure for initial abdominal incision.

Necropsy Technique

1. Moisten the feathers with water-containing detergent. If ornithosis (psittacosis) is suspected, the bird should be soaked in 5 per cent lysol solution and a laminar flow hood utilized for the necropsy. 2. With scissors, cut through one lateral commissure of the mouth and examine the oral cavity. 3. Continue at the cut commissure and make a longitudinal incision through the skin of the neck to the thoracic inlet. Reflect the skin laterally and examine the paired vagus nerves. 4. Make a longitudinal incision in the larynx and trachea and examine. 5. With heavy scissors, remove the upper beak by a transverse cut near the eyes. This will allow inspection of the nasal cavity and will expose the open anterior end of the infraorbital sinuses. 6. Insert one blade of a sterile scissors into the infraorbital sinus. Make a longitudinal lateral incision through the wall of each sinus and examine them. Culture the sinuses if indicated. 7. Incise the loose skin between the medial surface of each thigh and abdomen (Fig. 3). Reflect the legs laterally and disarticulate the hip joints. Incise the skin on the medial aspect of each leg and reflect it to expose the muscles and stifle joint. 8. Connect the lateral skin incisions with a transverse skin in-

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Figure 4.

DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

Exposed breast and abdomen.

cision across the middle of the abdomen. Reflect the skin of the breast anteriorly and reflect the skin of the abdomen posteriorly (Fig. 4). 9. Make a longitudinal incision through the pectoral muscles on each side of the keel and over the costochondral junctions. The anterior end of each incision should intersect the thoracic inlet at the dorsoventral midpoint. With heavy scissors, cut through the coracoid and clavicle bones (Fig. 5). 10. With sterile scissors, make a transverse incision through the posterior part of the abdominal muscles. On each side, continue the incision anteriorly through the costochondral junctions. Remove the ventral abdominal wall and breast as one piece, observing the air sacs as they are torn during removal. 11. Without touching them, examine the viscera and air sacs in situ (Fig. 6). 12. Using sterile instruments, remove any organs and take any swabs desired for culturing. The spleen can be exposed aseptically by freeing the left margin of the gizzard and reflecting that organ to the bird's right side. All unnecessary manipulations and delays prior to culture increase the probability of contamination. Take intestinal cultures last. 13. Examine the pancreas (Fig. 7). Transect the esophagus at the anterior border of the proventriculus. Reflect the entire gastrointestinal tract posteriorly by cutting the mesenteric attachments and then remove it after transecting the rectum. 14. Remove and examine the liver and spleen.

NECROPSY OF CHICKENS, TURKEYS, AND OTHER POULTRY

Figure 5.

Figure 6.

Cut to open abdomen.

Exposed viscera in normal position.

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DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

Figure 7. and pancreas.

Duodenal loop

15. Examine the genitalia. In the female, remove the ovary and oviduct and open the oviduct longitudinally. 16. Examine the ureters and kidneys in situ. If indicated, you may remove them for closer examination. 17. Remove and examine the heart. 18. Examine the lungs by reflecting them medially from between the ribs. 19. With tissue scissors, make a longitudinal incision through the proventriculus, ventriculus, small intestine, ceca, colon, and cloaca. Examine for lesions and parasites. 20. Both brachial plexuses and sciatic nerves should be examined. The brachial plexus is most easily observed anterior to the first rib. The extrapelvic sciatic nerve is exposed by careful separation of the adductor muscles. The intrapelvic portion is exposed by removal of the overlying portion of the kidneys by blunt dissection. 21. With strong shears, split one femur longitudinally and examine the bone marrow. 22. To examine the brain, disarticulate the head and skin it. Remove the calvarium with strong scissors using the same technique as for mammals.

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CLINICAL PATHOLOGIC EXAMINATIONS Clinical pathologic examinations should be incorporated as part of the diagnostic procedure so that at the completion of necropsy all general and microscopic observations are known. Only bacteriologic, serologic, and virologic procedures will be pending. Use of such a procedure will enhance your proficiency and competence in avian pathology.

Coccidia Examine serosal surfaces and note coccidial colonies before incising the intestine. The entire length of the intestine is subject to infection because of the multiple coccidial species for respective bird species. Coccidia are host specific and do not cross bird species lines. Even so, coccidiosis is a common infection of all bird species. Scrapings and wet mounts should be made from various areas of the intestine. Examine the wet mounts directly under the microscope for the presence of oocysts. With most species of coccidia, oocysts occur at the lesion site. However, with Eimeria necatrix (chicken), the lesion is located in the jejunum and the oocyst in the cecum. Lesions caused by coccidia vary in severity, appearance, and location. Lesions associated with coccidiosis of chickens include thickening of the intestinal mucosa, ballooning, intestinal necrosis, and hemorrhage. Cecal hemorrhage is almost diagnostic for E. tenella (chicken). In contrast, coccidial lesions in turkeys and game birds tend to be a whitish, foamy, mucocatarrhal exudate. Speciation of the coccidia is not important in a clinical diagnosis, with a few exceptions. Most avian coccidial species are sensitive to the same anticoccidial drugs. Flagellated and Other Intestinal Protozoa A clinical diagnosis is made by demonstrating the protozoa. Most protozoa die shortly after the death of the host. Therefore, freshly killed birds are necessary to confirm the infection. Clear, watery intestinal contents are a clue that the etiology may be a pathogenic protozoan. Make a wet mount of the liquid intestinal contents, apply a coverslip, and examine immediately, looking for movement. Most of these protozoa have a characteristic movement or motion. The prevalent protozoa seen in domestic poultry include Histomonas (movement by pseudopodia), Trichomonas (undulating membrane and flagella), Hexamita (flagella), Entameba (pseudopodia), and Giardia (flagella). Different species of Trichomonas cause either upper (crop) or lower (intestinal) lesions. If crop Trichomonas is suspected, make a wet mount from the crop. Birds with crop trichomoniasis exhibit a fetid mouth and crop odor.

eapillaria and Ascarid Larvae Intestinal scrapings often reveal Capillaria ova and ascarid larvae in otherwise undetected infections of these nematodes. Detection of

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DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

ascarid larvae in the mucosa is sufficient confirmation of the infection. However, further examination should be made to confirm diagnosis of capillariasis. Intestinal (duodenal) capillariasis is the most prevalent form in domestic poultry, whereas primarily crop and esophageal capillariasis occurs more frequently in game birds or turkeys. Capillaria worms can be demonstrated in wet mounts of deep mucosal scrapings or by floating opened sections of duodenum, crop, and esophagus in water in a petri dish and examining them under a dissecting scope. Excess ingesta and contents can be removed under a stream of water. The free end of the worm will be detectable as it floats away from the mucosal surface. Fecal Flotation Fecal flotation is not commonly used in poultry diagnostic procedures. However, it is a tool that would be useful to detect certain nematodes without killing the bird. The procedures are the same as those for any other animal species. Likewise, culturing or fecal smear Gram staining are useful procedures when necropsy with full laboratory workup is not possible. Yeast and Fungus

Candida albicans, as the cause of crop mycosis, is the most prevalent yeast infection in poultry. Yeast organisms can be demonstrated by staining crop scrapings with methylene blue, applying a coverslip, pressing, and examining microscopically under low-power magnification. The dye provides contrast and yeast cells become identifiable. Fungal wet mount smears should be digested for 15 minutes with 20 per cent sodium hydroxide with frequent warming and then examined under high-power magnification for mold hyphae. Exudates and Tissue Impression Smears

Clostridia. Gram-stained intestinal impression smears give a fast and accurate recognition of clostridial bacteria in cases of necrotic and ulcerative enteritis. Merely make impression smears or put a droplet of the clear fluid from the intestinal lesion on a slide, air dry, use Gram stain, and examine under a microscope for clostridia-like bacteria. Clostridium perfringens and Clostridium colinum are the etiologies, respectively, of these two diseases. Coryza. When infectious coryza is suspected (especially in chickens), make thin smears of the clear nasal or sinus exudate for staining. Giemsa and methylene blue stains may be preferred to Gram stain. Culturing and identifying any of these bacteria provide indisputable confirmation. Tuberculosis. Tuberculosis is ordinarily diagnosed on gross findings alone. However, the mycobacteria can be demonstrated readily from tubercles by acid-fast staining of smears from the incised lesion.

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Bacteriologic Culturing Aerobic bacteriologic cultures are a valuable adjunct to poultry necropsy and diagnosis. The majority of prevalent avian bacterial pathogens can be cultured in a small private laboratory by using a small variety of selected media. Bacterial culturing procedures can be limited to streaking agar plates directly from the lesion during necropsy, incubating, and identifying the bacterium by colony type and Gram stain. Even a no-growth result from a culture is valuable information when nonbacterial etiologies are involved. For example, synovitisarthritis infections can be caused by Staphylococcus, Erysipelas, Mycoplasma, and reovirus. Lack of bacterial growth from joint exudates is helpful to confirm the presence of Mycoplasma or reovirus. Serologic Tests A variety of plate agglutination tests can be used routinely or selectively as case history dictates to confirm a diagnosis. Common tests that should be considered for use in small farm flocks, exhibit poultry, game cocks, and other hobby poultry include Pullorum testing by either the whole blood rapid plate test or the serum plate agglutination test and the Mycoplasma gallisepticum (MG) Serum Plate Agglutination Test. Other tests are available, such as the agar gel precipitin test for avian influenza, reovirus, and adenovirus. However, when these diseases are suspected, the flock owner should be referred to the official state diagnostic laboratory. Avian serologic testing is now quite sophisticated and is being used to monitor health and performance of commercial poultry production. Poultry owners should be referred to the state laboratory for such testing.

DIAGNOSTIC INTERPRETATION It is tempting in a article such as this to present a brief, simplistic guide for associating necropsy findings with specific diseases. Because this may be more misleading than helpful, the reader is referred to available reference sources. Since the necropsy is primarily a visual effort, the most helpful information sources on poultry diseases are those with abundant high-quality illustrations. However, to gain a solid understanding of specific diseases, the more standard reference texts must be consulted. Whatever reference sources are used, it is helpful initially to prepare a checklist of diseases affecting various organs, systems, or regions of the body. It is also frequently helpful to categorize diseases by the age at which they most frequently occur and by the nature of the etiologic agent (viral, bacterial, fungal, and so on). Tables 1 (Differential Diagnosis of Avian Respiratory Diseases) and 2 (Diagnosis of Nonrespiratory Diseases) have been developed as a quick diagnostic reference for the more prevalent diseases of poultry.

Turkeys

RNA virus

Herpesvirus

Virus (pox) chicken, Many birds, not turkey, pigeon, canary parakeets

Infectious bronchitis

Infectious laryngotracheitis

Fowl pox

Chicken, pheasant

Chicken only

All birds, all ages

Myxovirus

Newcastle disease " avian pneumoencephalitis"

Chicken, turkey, pigeon, guinea, game birds

Chickens, pheasants, quail

Aspergillus fumigatus All birds

Haemophilus gallinarum Mycoplasma gallisepticum

Aspergillosis brooder pneumonia

Mycoplasmosis CRD

!,nfect!,ous coryza roup

Pasteurella multocida All birds

Fowl cholera

HOSTS/AGE

CAUSE

Facial edema and scattered hemorrhages

Respiratory, nervous (young), no eggs in adults

None Topical iodine and vaccinate

Cutaneous scabs Diphtheritic

Wet form

Hemorrhagic, mucous None specific, antibiotics, vaccinate exudate in trachea

N one specific, increase house temperature, antibiotics (course 1014 days)

Supportive, increase house temperature, antibiotics (course 1014 days)

N one specific, copper sulfate, change litter

Cutaneous

Severe respiratory

Caseous plugs in bronchi

Plaques on air sacs, cottony trachea, granulomas

Respiratory, 30-50% egg production, poor egg quality

Sulfa, erythromycin, streptomycin

Antibiotics (tetracyclines), sulfa drugs

TREATMENT

Ty losin, erythromycin Thickened air sacs, pericarditis, perihepatitis, sinusitis

Odoriferous sinus

Abscesses, wattles

Hemorrhages, septicemia

LESIONS

Respiratory gaping

Respiratory, stunting, swollen sinuses

Respiratory, facial edema

Chronic

Acute/chronic

CLINICAL SIGNS

Differential Diagnosis of Avian Respiratory Diseases

DISEASE

Table 1.

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Chicken only (mature and semimature) All poultry

Chickens (adult)

Chickens, turkeys

Turkeys, pea-fowl, partridges

Unnamed Vibrio

Candida albicans

Reovirus/metabolic

Escherichia coli

Histomonas meleagridis Coccidia (host

"Vibrionic hepatitis"

Crop mycosis "thrush"

Avian monocytosis "blue comb"

Coligranuloma (Hjarre's disease)

Blackhead "histomoniasis" All bird species, young birds

Quail, chickens

Clostridium colinum

Ulcerative enteritis " quail disease"

specific: chicken-9 species, turkey-4 pathologic species)

All birds, swine, mink, rabbits, cattle sensitized, humans rarely

Mycobacterium avium

Avian tuberculosis

Coccidiosis

HOSTS/AGE

CAUSE

LESIONS

Diarrhea, depression, paleness, stunting, death

Diarrhea, depression, anorexia, weight loss

Emaciation, depression, diarrhea, death

Anorexia, depression, diarrhea, weight loss, subnormal temperature

Anorexia, diarrhea

Weight loss, sudden death, anemia

Sudden death, depression, emaciation

Dilated gut, may be blood in cecum, white streaksduodenum, focal lesions/serosa

Cecal cores, liver necrosis

Granulomas

Watery ingesta to thick mucus in gut, crop empty, chalky foci in pancreas, dehydration

Rough, thickened mucus-covered, dirty gray crop wall (may also see in gizzard and gut)

Necrosis of liver, ascites

Ulcers (intestine), peritonitis

Weight loss, generally Emaciation, 1 yr old or older, granulomas emaciation

CLINICAL SIGNS

Diagnosis of Nonrespiratory Diseases

DISEASE

Table 2.

Sulfa, amprolium

Emtryl, ipropan

nf-IBO, furazolidone

Antibiotics, molasses, high level tetracyclines

Mycostatin, copper sulfate (1 :2000 in water)

Terramycin, neomycin, furazolidone

Streptomycin, neomycin, bacitracin, lincomycin

None, incinerate

TREATMENT

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DWIGHT SCHWARTZ AND ARTHUR A. BICKFORD

Any discussion of reference sources must distinguish between the introductory and the definitive sources. Both can be highly recommended for specific uses, but there is a vast difference in depth of coverage and objectivity, and this needs to be recognized. Among the introductory treatises on poultry diseases, one that has long been an outstanding guide to interpreting necropsy findings is Peckham, M. C.: The Diagnosis of Poultry Diseases. Veterinary Scope, 11 (no. 1): 1966. This article is especially helpful, for it contains 84 high-quality color photographs and follows a regional approach in the sequence of a routine postmortem examination. The seventh edition of the Salsbury Manual of Poultry Diseases is also an excellent introductory guide with numerous color photographs, but diseases are presented in alphabetical order. Although not illustrated, other publications, such as The Merck Veterinary Manual (Merck & Company, Inc., Rahway, New Jersey) and The Merck Poultry Serviceman~s Manual (Merck & Company, Inc., Rahway, New Jersey), are also useful, quick reference sources. Offering an intermediate level of detail are the Poultry Health Handbook (Pennsylvania State University, University Park, Pennsylvania) and the AAAP Avian Disease Manual (American Association of Avian Pathologists, Kennett Square, Pennsylvania). The definitive textbook in this field is Diseases of Poultry (Iowa State University Press, Ames, Iowa), which offers encyclopedic detail on historical perspective, etiology, pathogenesis, diagnostic methodology, prevention, and control, as well as gross and microscopic pathology for each major poultry disease. A new book entitled Color Atlas of Diseases of the Domestic Fowl (Iowa State University Press, Ames, Iowa) should be a particularly valuable adjunct to other texts in offering a well-illustrated guide for the interpretation of necropsy findings. Finally, those interested in pursuing microbiologic followup of infectious poultry diseases will find the AAAP publication Isolation and Identification of Avian Pathogens (American Association of Avian Pathologists, Kennett Square, Pennsylvania) to be very valuable. Animal Health Diagnostic Laboratory College of Veterinary Medicine Michigan State University P. O. Box 30076 East Lansing, Michigan 48909