Compendium of Psittacosis (Chlamydiosis) Control 1997

[Graehstone]

Compendium of Psittacosis (Chlamydiosis) Control 1997
National Association of State Public Health Veterinarians Inc.

Infection with Chlamydia psittaci is an important cause of systemic illness in companion birds and poultry (chlamydiosis). Infection can be transmitted from infected birds to humans, causing illness with pneumonia (psittacosis). The purpose of this compendium is to provide information on chlamydiosis in companion birds and psittacosis in humans (also known as ornithosis or parrot fever) to public health officials, veterinarians, physicians, the companion bird industry, and others concerned with control of the disease and protection of public health. The intent of these recommendations is to facilitate the standardization of chlamydiosis disease control procedures for companion birds. These recommendations will be reviewed and revised as necessary.
Introduction
Chlamydiosis is a zoonotic disease caused by Chlamydia psittaci. The bacterium has been isolated from at least 129 avian species and is most commonly identified in psittacine birds (for example, parakeets, parrots, macaws, and cockatiels). Among non-psittacine caged birds, infection occurs most frequently in pigeons, doves, and mynah birds. The incidence in canaries and finches is relatively low.
The time between exposure and illness (the incubation period) in caged birds varies from days to weeks, and may be as short as 3 days. Among infected birds, latent infections are common and active disease may occur years after exposure. Shipping, crowding, chilling, breeding, and other stressful factors may activate shedding of the infectious agent. Normal appearing birds may be carriers and intermittent shedders of C. psittaci. The organism is excreted in the droppings and nasal discharges of infected birds, is resistant to drying, and can remain infective for several months.
Since several human diseases can be caused by other species of Chlamydia, the infection in humans with C. psittaci is frequently referred to as psittacosis. From 1985 through 1995, more than 1,100 human cases of psittacosis were reported to the Centers for Disease Control and Prevention. However, because the diagnosis of psittacosis in humans can be difficult, these figures may underestimate the actual incidence of infection. Data from surveillance carried out in the 1980s revealed that caged pet bird exposure accounted for 70% of human cases in whom source of infection was known. The largest single group of affected people were pet bird owners or fanciers (43%). Pet shop employees accounted for an additional 10% of cases. Other people at risk include pigeon fanciers, poultry processing plant employees, veterinarians, veterinary technicians, laboratory workers, avian quarantine station workers, farmers, and zoo workers. Because human infection can result from transient exposure to infected birds or their contaminated droppings, many individuals with no identified avocational or occupational risk may become infected. Psittacosis is a public health problem which merits improved surveillance and better control, as the disease can result in serious human illness, hospitalization, or death.
THE NASPHV COMMITTEE
Millicent Eidson, MA, DVM, Dpl. ACVPM (Epidemiology); Chair
William B. Johnston, DVM, Dpl. ACVPM
Kathleen A. Smith, DVM, MPH
Mary Grace Stobierski, DVM, MPH, Dpl. ACVPM

CONSULTANTS TO THE COMMITTEE
Jay C. Butler, MD; Dpl. AVIM, ABP; Centers for Disease Control and Prevention (CDC)
Keven Flammer, DVM; Dpl. ABVP (Avian Practice); North Carolina State University; Association of Avian Veterinarians (AAV)
Kevin F. Reilly, DVM; AVMA Council on Public Health and Regulatory Veterinary Medicine
Susan L. Clubb, DVM; Dpl. ABVP (Avian Practice); Pet Industry Joint Advisory Council (PIJAC)
Susan E. Lance, DVM, PhD; Council of State and Territorial Epidemiologists (CSTE)

ENDORSED BY:
American Veterinary Medical Association (AVMA); Council of State & Territorial Epidemiologists (CSTE);
Association of Avian Veterinarians (AAV); Pet Industry Joint Advisory Council (PIJAC)

Address all correspondence to:
Dr. William Johnston, Alabama Dept. of Public Health, Div. of Epidemiology, 434 Monroe St., Montgomery, AL 36130
Clinical Signs
Chlamydial infection in birds may be asymptomatic or may appear clinically as an acute, subacute, or chronic disease. Clinical signs and mortality vary with the species of bird affected, virulence of the strain, infective dose, stress factors, age, route of exposure, and extent of treatment or prophylaxis.
Birds with symptomatic chlamydiosis typically resemble birds with any other systemic illness. Affected birds may be lethargic, anorectic, and have ruffled feathers. Other signs of illness include serous or mucopurulent ocular or nasal discharge and diarrhea, with urates stained green to yellow-green. Anorectic birds may have sparse dark green drippings. Birds may die acutely, or as the disease progresses, the bird may become emaciated, dehydrated, and die.
Avian Chlamydiosis Case Classification (See Appendix A)
A confirmed case of chlamydia infection is defined as a bird with or without clinical illness compatible with chlamydiosis and one or more of the following confirmatory laboratory results:
• (1) isolation of C. psittaci from a clinical specimen
(2) chlamydial antigen detected by immunofluorescence (fluorescent antibody, FA) or ELISA of tissues
(3) fourfold or greater change in serologic titer between 2 specimens obtained 2 or more weeks apart, run at the same lab, preferably in parallel
(4) Chlamydia organisms identified within macrophages in stained (Gimenez, Machiavelo) smears or sections of tissues.
A probable case of chlamydiosis is defined as a bird with clinical illness compatible with chlamydiosis and one or more of the following confirmatory laboratory results:
• (1) A single high serologic titer in 1 or more specimens obtained after the onset of signs
(2) Chlamydia antigen detected by ELISA or FA of feces, a cloacal swab, or respiratory or ocular exudates.
A suspect case of chlamydiosis is defined as either:
• (1) a clinical illness compatible with chlamydiosis without confirmatory laboratory results (especially in birds epidemiologically linked to other human or bird cases)
(2) an asymptomatic condition in which laboratory results are equivocal, for example, a single high serologic titer or detection of chlamydial antigen
(3) a clinical or asymptomatic condition in which laboratory results are positive using a new investigational or non-standardized test
(4) a clinical illness compatible with chlamydiosis which is responsive to appropriate therapy

General treatment recommendations (see Appendix B)
All birds with confirmed or probable chlamydiosis should be placed in isolation and treated, preferably under the supervision of a licensed veterinarian. Suspect birds, or birds exposed to chlamydiosis, should be isolated and retested, or treated. There is no vaccine against avian chlamydiosis. Because a treated bird can be reinfected with C. psittaci after treatment, it should be kept isolated from untreated birds or other potential sources of infection. Thorough cleaning and sanitizing of the aviary is necessary to prevent reinfection from environmental sources.
• (1) Stress, poor husbandry, and malnutrition will reduce the effectiveness of treatment and encourage the development of secondary infections by other bacteria and yeast. Fresh water and appropriate vitamins should be provided at all times.
(2) The birds should be observed daily to ensure they are eating and should be weighed every 3 to 7 days.
(3) Administration of antibiotics through the drinking water is not effective.
(4) Birds to be treated should be held in clean cages and not overcrowded. All breeding should be stopped.
(5) Spilled food should be cleaned up promptly and water and food containers washed daily.
(6) High dietary concentrations of calcium or other divalent cations will reduce absorption of tetracyclines.
Importation of birds and import regulations
Recent changes in importation regulations have greatly reduced the number of imported birds. While helpful, import regulations do not guarantee that birds released from USDA import stations are free of chlamydiosis. The disease is also imported through smuggled birds. Current regulations regarding commercially imported birds require:
• (1) Import permit in advance of shipping and a health certificate from the exporting country.
(2) Minimum quarantine period of 30 days for each lot of birds. The 30-day holding time is in response to the threat of exotic Newcastle Disease to the poultry industry.
(3) All psittacines birds must receive medicated feed (see Appendix B)
(4) Recommendations by the USDA are made to importers to continue CTC treatment for an additional 15 days except for budgerigars.
Recommended Control Measures
(1) Maintenance of accurate records on all bird transactions is strongly encouraged to aid in identification of sources of infected birds and potentially exposed individuals. Records should include the source, date of purchase, species, and any identified illnesses or deaths. When birds are sold, the name, address and phone number of the customer, date of purchase, species purchased, and the band number (if applicable) should be recorded by the seller.
(2) Birds with signs compatible with chlamydiosis should not be purchased or sold.
(3) Before adding new birds to a group, the birds should be quarantined and observed for a 14-30 day period and tested or prophylactically treated. Birds that are boarded or sold on consignment should be placed in a separate part of the store that has separate air-handling equipment. Birds should be tested for chlamydiosis prior to boarding or agreeing to sell birds for a third party.
(4) Preventive husbandry: Cages should be positioned so that droppings, feathers, food and other materials from one cage cannot enter another cage. Cages should not be stacked. Solid-sided cages or barriers should be used if cages are adjoining. Each cage should be cleaned daily. Food and water bowls should be emptied, cleaned with soap and water, rinsed, placed in a disinfectant solution, and rinsed well on a daily basis. Between occupancy by different birds, the cages should be thoroughly scrubbed with soap and water, disinfected and then rinsed in clean running water. Exhaust ventilation should be sufficient to prevent accumulation of aerosol in the air.
(5) Husbandry during infection: If chlamydiosis is found or suspected, birds requiring treatment should be held in isolation. Rooms and cages where infected birds were housed should be immediately cleaned and disinfected. Cages should be of ample size, preferably one bird to a cage, and should have a wire mesh bottom to keep birds off the floor. A nondusty litter, such as newspapers, should be placed underneath the wire mesh. When the cage requires cleaning, the bird should be transferred into a clean cage, and the soiled cage should be thoroughly scrubbed with a detergent to remove all droppings, rinsed, then disinfected. Allow adequate contact time (at least 5 minutes), and rerinse to remove the disinfectant. The cages, air handling system, and room holding the bird should be thoroughly disinfected prior to the end of treatment to eliminate chlamydial organisms from the environment. All items that cannot be adequately disinfected (e.g., wooden perches, nest material, and litter) should be discarded. During treatment, precautions should be taken to keep circulation of feathers and dust to a minimum. This can be done by frequent wet-mopping with disinfectants, liberal use of oil-impregnated sweeping compound between moppings and prevention of air currents and drafts. To reduce dust contamination, the floor can be sprayed with an appropriate disinfectant or water prior to sweeping. The use of vacuum cleaners is strongly discouraged to prevent aerosolization of particles. Cage waste should be frequently removed (after moistening) and burned or double bagged before disposal. Whenever possible, healthy birds should be cared for prior to handling isolated birds.
(6) Disinfection: Because the infectious particle of C. psittaci is high in lipid content, it is susceptible to most disinfectants and detergents. In the clinic or laboratory, 1:1000 dilution of quarternary ammonium compounds (alkyldimethylbenzylammonium chloride e.g. Roccal or Zephiran) is effective, as well as 70% isopropyl alcohol, 1% Lysol, 1:100 dilution of household bleach (2 ½ tbsp. per gallon), or chlorophenols. Chlamydia organisms are susceptible to heat and resistant to acid and alkali. Disinfectants can be respiratory irritants, and should be used in a well ventilated area. Avoid mixing disinfectants with any other product.
(7) Personal protection: All persons in contact with infected birds should be informed about the nature of the disease. A physician should be consulted if respiratory illness develops in personnel so that early and specific treatment for psittacosis can be initiated. Personnel should wear protective clothing, gloves, a paper surgical cap, and a dust-mist mask when cleaning cages or handling infected birds. Surgical masks may not be effective in preventing transmission. In high risk situations the use of a well-fitting sub-micron or high efficiency particulate (HEPA) mask may be considered. When potentially infected birds are necropsied, additional precautions include wetting the carcass with detergent and water to prevent aerosolization of infectious particles, and working under an exhaust-fan examining hood.
Veterinarian's Responsibility
Veterinarians should be aware that chlamydiosis is not rare in pet birds. The disease should be considered in any lethargic bird with non-specific signs of illness, especially if the bird was recently purchased. If chlamydiosis is suspected, appropriate laboratory specimens should be submitted to a veterinary diagnostic laboratory to confirm the diagnosis. Laboratories and the attending veterinarian should follow local and state regulations and/or guidelines regarding reporting of cases and should work closely with the authorities who conduct investigations in their jurisdiction. The veterinarian should inform the client that the bird should be isolated and treated appropriately. In addition, the client should be informed of the public health hazard, appropriate precautions, and the need to seek medical attention if persons exposed to the bird develop flu-like symptoms or respiratory tract illness.
Epidemiologic Investigations
The following situations should prompt an epidemiologic investigation to control the spread of chlamydiosis in birds and human beings:
•
o (1) a bird with confirmed chlamydiosis that was procured from a pet store, breeder, or dealer within 60 days of the onset of signs
(2) a bird in contact with a human being with confirmed chlamydiosis
Birds or human beings with probable or suspect chlamydiosis should be investigated at the discretion of the local or state authorities. Investigations involving recently purchased birds should include a visit to the site where the infected bird is located, and identification of the location where the bird was originally procured (e.g., pet shops, dealers, breeders, and quarantine stations). When conducting investigations, it is helpful to document the number and types of birds involved, the health status of personnel and birds, bird location, ventilation, and the treatment protocol. In order to facilitate detection of multi-state outbreaks of psittacosis, local and state authorities should report suspected outbreaks by telephone to the Childhood and Respiratory Diseases Branch, Centers for Disease Control and Prevention, 404-639-2215.
Quarantine
Because of the severe economic impact of quarantines, reasonable options should be made available to the owner/operator. The purpose of quarantine is to prevent further disease transmission, not to discourage further disease reporting. With the approval of appropriate local or state authorities, the owner of the quarantined birds may choose one of several options:
• (1) treat the birds (See Appendix B);
(2) remove the birds from the premises and treat in a separate quarantine area;
(3) euthanize the birds.
Birds under quarantine may be sold if they have completed at least 7 days of treatment , provided that the new owner agrees in writing to continue the quarantine and treatment, and is informed of the disease hazards. Following complete treatment or removal of the birds, a quarantine may be lifted after the infected premises are thoroughly cleaned and disinfected. At that point, the area can be restocked.
Additional Information:
• Fudge AM. Avian Chlamydiosis. In, Rosskopf WJ and Woerpel RW (eds.): Diseases of Cage and Aviary Birds. Baltimore: Williams & Wilkins, pp. 572-85, 1996.
Gerlach H. Chlamydia. In, Ritchie BW, Harrison GJ, and Harrison, LR (eds.): Avian Medicine, Principles and Application. Lake Worth, Florida, Wingers Publishing, pp. 984-996, 1994.
Grimes JE. Detection of Chlamydial Infections. In, Rosskopf WJ and Woerpel RW (eds.): Diseases of Cage and Aviary Birds. Baltimore: Williams and Wilkins, pp. 827-35, 1996.
Reports from the Symposium on Avian Chlamydiosis. J Am Vet Med Assoc, 195:1501-76, 1989.

Appendix A: Diagnostic Methods for Chlamydiosis (Psittacosis) in Birds
Gross/histopathologic findings
No specific gross lesion is pathognomonic; however, cloudy air sacs and large liver and spleen are usually observed. Laboratory diagnostic procedures include PCR, antigen capture ELISA, and the chromatic and/or immunostaining of tissue impression smears to identify organisms. Isolation of C. psittaci from spleen, liver, air sacs, pericardium, heart, or intestines is the optimal diagnostic verification procedure.
Culture
The most specific diagnostic procedure is recovery of the etiologic agent. Chlamydia are obligate intracellular parasites, and must be isolated in tissue culture, mice, or chick embryos. Specialized laboratory facilities and training are necessary for reliable identification of chlamydial isolates. Relatively few laboratories do chlamydial cultures.
In live birds, depending on clinical signs, combined choanal and cloacal swab specimens should be collected, refrigerated, and sent to the laboratory with ice packs. Specimens should not be frozen. Sample handling is critical for maintaining the viability of organisms for culture, and a special transport media is required. Veterinarians should contact their specific diagnostic laboratory for procedures required for submission of specimens for isolation. When screening live birds for C. psittaci, the microorganism may not be shed daily, therefore, serial specimens should be collected for 3 to 5 consecutive days and pooled to save laboratory costs. Liver and spleen are the preferred necropsy specimens for isolation of C. psittaci.
When there is a chance of legal action resulting from chlamydiosis cases, use of culture is recommended to avoid limitations associated with other tests.
Summaries below are for those tests which have peer-reviewed reports available.
Serologic Tests (tests for antibody)
The major problem with serologic testing is the interpretation of results. A positive serologic test result is evidence that the bird has been infected with C. psittaci, but does not prove the bird currently has active disease. False negative results may occur with acute infection when birds are sampled prior to seroconversion. Treatment may also blunt antibody response.
Among serologic diagnostic methods used to detect antibody are complement fixation, modified-direct complement fixation, latex agglutination, elementary body agglutination, and microimmunofluorescence. A single testing method may not be adequate, because of the diversity of reactions with immunoglobulins from the various avian species. Therefore, the use of a combination of antibody and antigen detection methods for the diagnosis of chlamydiosis seems prudent at this time, particularly when an individual bird is the subject. With individual birds, serologic testing is most useful when paired sera are examined and the results are compared with WBC counts, liver enzyme activities, serum or plasma protein electrophoresis, signs of disease, and the flock or aviary history.
Direct complement fixation
DCF is more sensitive to antibody activity than agglutination methods. No commercial antigen is available. False-negative results are possible in specimens from small psittacine birds, such as budgerigars, young African Grey Parrots, and lovebirds. High titers may persist after treatment and confuse interpretation.
Modified DCF is more sensitive than DCF .
Latex agglutination (antigen is currently unavailable)
Elementary body agglutination
EBA is commercially available and may detect early infection. Titers of 10 in budgerigars, cockatiels, and lovebirds, and titers of 20 in larger birds, are interpreted by the laboratory as indicating current infection. However, positive titers may persist after treatment is completed, and EBA is offered only by a single laboratory.
Tests for Antigen
Immunofluorescent staining
Monoclonal or polyclonal antibodies and fluorescein staining techniques and fluorescent microscopy are used to identify elementary bodies in impression smears from tissues. When used with cloacal or fecal smears, the test sensitivity and specificity are questioned by some authorities. The test is most useful if the bird is shedding large amounts of antigen. The advantages of the test are that the test gives a rapid diagnosis and does not require live, viable organisms. Accurate interpretation of fluorescent staining requires an experienced microscopist.
ELISA
Two of the ELISA (IDEIA, Surecell) currently being used to detect C. psittaci were originally developed for detection of the lipopolysaccharide antigen on C. trachomatis, a human pathogen. The sensitivity and specificity of these tests for detecting C. psittaci are not known. The test results must be evaluated in conjunction with other clinical findings. If a bird has a positive ELISA result but appears clinically normal, the veterinarian should attempt to verify that the bird is a shedder through isolation of the organism. When a clinically ill bird has a negative ELISA result, chlamydiosis cannot be ruled out. The ELISA test does not require viable organisms. It is rapid, and some tests can be done in house (e.g. Surecell). Due to intermittent shedding of antigen, sensitivity is questionable in asymptomatic birds, and some ELISA tests may cross-react with other bacteria.
Additional tests
These tests are in use but peer-reviewed reports are not currently available. Methods currently under investigation include microagglutination, microimmunofluorescence, and polymerase chain reaction (PCR).
Laboratories
Many state diagnostic laboratories and veterinary colleges perform routine chlamydial diagnostics. Additional laboratories are listed below; others may be available. Inclusion in this list does not imply endorsement from the Psittacosis Compendium.
Micro Biology Reference lab; 800-233-7182; 714-220-1900
Comparative Pathology Laboratory, University of Miami; 800-232-1056; 305-243-4726
Texas Veterinary Medical Laboratory; 409-845-3414
Animal Health Diagnostic Laboratory; 517-353-1683
Avian and Exotic Animal Clin/Path Labs; 213-542-6556
Marshfield Laboratories, Vet. Division; 800-222-5835
Labcorp Veterinary Services; 800-334-5161
Research Associates Laboratory, Inc., 513-248-4700
California Avian Laboratory; 800-783-2473
Appendix B: Chlamydiosis Treatment Options for Companion Birds
There are several methods for treating avian chlamydiosis (psittacosis). Aureomycin (chlortetracycline) powder is labeled for use in producing a medicated mash diet; however it is generally recognized that doxycycline is more effective in eliminating the disease. While these protocols are usually successful, information in this area is evolving and no treatment protocol guarantees safe treatment or complete elimination of infection in all avian species; thus, treatment should be supervised by a licensed veterinarian.
Methods of treatment:
1. medicated feed: The medicated feed should be the only food provided to the birds for the entire treatment period. Acceptance of the medicated feed is variable so food consumption should be monitored. Acceptance may be enhanced by first adapting the birds to a similar non-medicated diet. The treatment period begins when the birds accept the medicated feed as the sole food in the diet.
• a. medicated mash diets: 1% chlortetracycline (CTC) mash diet can be used. The recommended recipe is 2 pounds rice, 2 pounds hen’s scratch feed, and 3 pints water cooked for 15 minutes at full pressure in a pressure cooker. Add 10 mg CTC/gram feed after the cooked feed cools. This diet is unpalatable and acceptance by the birds may be limited.
b. white millet seed (for budgerigar parakeets and finches only) impregnated with 0.5 mg of CTC/gram of seed should be used for a treatment period of 30 days (Keet Life, Hartz Mountain is the only manufacturer)
c. pellets and extruded products: Diets containing 1% CTC are available and appropriate for use in most companion birds. A size of pellet should be selected that is appropriate for the size of bird being treated. The treatment period is 45 days.
d. A special diet may be necessary for birds belonging to a subfamily of psittacine birds known as Loriidae (lories and lorikeets) which feed on nectar and fruit in the wild.
2. oral or parenteral treatments (birds should be treated for a total of 45 days)
• a. Oral doxycycline: Doxycycline is the drug of choice for oral treatment and either the monohydrate or calcium syrup formulations may be used. Based on non-peer-reviewed studies, dosage recommendations are: 40-50 mg/kg PO SID in cockatiels, Senegal parrots, and Blue-fronted and Orange-winged Amazon parrots, 25 mg/kg PO SID in African grey parrots, Goffin's cockatoos, and Blue and Gold and Green winged macaws. In untested species it is impossible to precisely extrapolate dosages; however 25-30 mg/kg PO SID is the recommended starting dose in cockatoos and macaws, and 25-50 mg/kg PO SID is recommended in other psittacine species. If regurgitation occurs, another treatment method should be used.
b. Injectable doxycycline: Intramuscular injection into the pectoral (breast) muscle is often the easiest method of treatment but not all injectable doxycycline formulations are suitable for IM injection. All current formulations may cause irritation at the site of injection. The Vibrovenos formulation (Pfizer Laboratories) is available in Europe and Canada and is effective if given at doses of 75-100 mg/kg IM every 5-7 days for the first 4 weeks and then every five days for the duration of the treatment period. There are anecdotal reports of successful use of pharmacist-compounded injectable doxycycline products in the U.S.; however, studies are currently lacking to determine precise dosage schedules. The injectable hyclate formulation labeled for IV use in humans in the U.S. should not be used for IM use as severe tissue reactions will occur at the site of injection.
c. Injectable oxytetracycline: There is limited information guiding the use of an injectable long-acting oxytetracycline product (LA-200, Pfizer Laboratories). Current dosage recommendations are: 75 mg/kg SQ every 3 days in Goffin's cockatoos, Blue-fronted and Orange-winged Amazon parrots, and Blue and Gold macaws. This dose may be suitable for other species but has not been tested. This product will cause irritation at the site of injection and is best used to initiate treatment in sick birds or those that are reluctant to eat. Following stabilization with oxytetracycline treatment, the birds should be switched to another form of treatment to reduce the tissue irritation that would be caused by repeated oxytetracycline injection.
3. experimental methods: Treatment protocols using fluoroquinolones, late generation macrolides, pharmacist compounded injectable doxycycline, and doxycycline medicated feed are currently being investigated. Information about these treatment protocols may be available in scientific literature or from avian veterinary specialists.
Sources of Medicated Feeds: These are not listed as an endorsement of said company or products. Other sources may be available.
Avi-Sci, Inc.; PO Box 598; Okemos, MI 48805; 800-942-3438
The Bird Company, 619-748-3847
Hartz Mountain Corp.; 700 Frank E. Rogers Blvd.; Harrison, NJ 07029; (201) 481-4800
Lafeber Company; RR2; Odell, IL 60460; (800) 842-6445
Kay Tee Products Inc.; P.O. Box 230; 292 E. Grand St.; Chilton, WI 53014;800-669-9580; 800-356-5020
Pretty Bird International Inc.; 5810 Stacy Trail; Stacy, MN 55079; 800-356-5020
Rolf C. Hagen; P.O. Box 9107; Mansfield, MA 02048; 800-225-2700/2701
Roudybush; P.O. Box 908; Templeton, CA 93465; 800-326-1726; 805-434-0303
Ziegler Bros., Inc.; PO Box 95, Gardners, PA 17324--0095; 800-841-6800
Appendix C: Psittacosis in Human Beings
Clinical Signs
Human infection usually occurs through the inhalation of the organism aerosolized from bird droppings and respiratory secretions. Other sources of exposure can include bird bites, mouth to beak contact, and handling plumage and tissues. Transient exposures may be adequate to induce disease. The incubation period varies from 5 to 14 days and infections range from inapparent to severe systemic disease with pneumonia. Infected human beings typically develop fever, chills, headache, malaise, and myalgia, with or without symptoms referable to the respiratory tract. A nonproductive cough usually develops, and auscultatory findings may underestimate the extent of pulmonary involvement. Radiographic findings may include lobar or interstitial infiltrates. Other causes of pneumonia that may be confused with chlamydiosis include infections with Coxiella burnetii, Mycoplasma pneumoniae, C. pneumoniae, Legionella spp, and viruses such as influenza. Extrapulmonary involvement of chlamydiosis may include endocarditis, myocarditis, hepatitis, arthritis, keratoconjunctivitis, and encephalitis. Fatality is <1% in properly treated patients.
Reinfection can occur. Person-to-person transmission occurs rarely, if ever; therefore, patient isolation and prophylaxis of contacts is not indicated.
Case definition
These case definitions have been established by the Centers for Disease Control and Prevention and the Council of State and Territorial Epidemiologists for epidemiologic purposes and should not be used as sole criteria for establishing clinical diagnoses.
A person is confirmed to have psittacosis if clinical specimens are culture-positive for C. psittaci or if clinical illness is compatible with psittacosis and there is a fourfold or greater increase in Chlamydia CF or microimmunofluorescence (MIF) antibody titer to 32 in paired sera obtained at least 2 weeks apart. A probable case of psittacosis consists of a clinically compatible illness that is epidemiologically linked to a confirmed case or that has a single Chlamydia CF or MIF antibody titer 32 in one or more serum specimens obtained after symptom onset.
Diagnosis
In human beings, the infective agent (elementary body) may be isolated from sputum, pleural fluid, and clotted blood during acute illness prior to treatment with antibiotic. Diagnosis is usually established by serologic methods in which paired sera are tested for Chlamydia CF antibodies. However, because Chlamydia CF antibody is not species-specific, high CF titers may also result from C. pneumoniae (TWAR) and C. trachomatis infection. Testing samples with MIF assays may distinguish C. psittaci infection from infection with other chlamydial species. Acute and convalescent serum specimens should be obtained as soon as possible after onset of symptoms and no earlier than 2 weeks afterwards, respectively. Treatment with tetracycline may delay or blunt the antibody response, so a third serum sample may help confirm the diagnosis. All sera should be tested simultaneously at the same laboratory. Additional information about laboratory testing may be available at state laboratories.
Treatment
Tetracyclines are the drugs of choice for treating psittacosis in human beings; most persons respond to oral therapy (doxycycline 100 mg BID or tetracycline 500 mg QID). In severely ill patients, tetracycline hydrochloride may be administered intravenously at a dosage of 10-15 mg/kg body weight/d. Remission of symptoms usually is evident within 48 to 72 hours, however, relapse may occur, and treatment must continue for at least 10 to 14 days following defervescence. Although in vivo efficacy has been questioned, erythromycin is probably the best alternative agent in people in whom tetracycline is contraindicated, for example, children under 9 years of age and pregnant women.
Responsibility of physicians
Reporting of human psittacosis to health authorities is required in most states. Timely diagnosis and reporting may aid in identifying the source of the infection and control of further disease spread. Because single serum titers are both insensitive and nonspecific for diagnosis of psittacosis, confirmation with paired acute and convalescent sera is recommended. Birds which are suspect sources of human cases should be referred to veterinarians for evaluation and treatment. Local and state authorities may conduct epidemiologic investigations and institute further disease control measures.