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Human Psittacosis Linked to a Bird Distributor in Mississippi -- Massachusetts and Tennessee, 1992

During April-May 1992, CDC was notified of a possible outbreak of psittacosis involving members of two families in Massachusetts and Tennessee who had recently purchased birds as pets. In the subsequent investigation of this problem, human psittacosis was defined as a fourfold rise in complement-fixing antibody titer to greater than or equal to 32 or a single titer of greater than or equal to 32 in a patient with fever and/or respiratory symptoms. This report summarizes the investigation of this problem. Massachusetts

On March 1, a 34-year-old man was hospitalized with radiographically confirmed lobar pneumonia following 2 days of fever, malaise, and sore throat. A presumptive diagnosis of psittacosis was made; he was treated with tetracycline and recovered. Also on March 1, the patient's wife and their 5-year-old child developed mucopurulent conjunctivitis -- presumed to be caused by Chlamydia psittaci--that responded to doxycycline and oral and topical erythromycin, respectively. Convalescent serum samples obtained from the man on March 16 and June 4 revealed titers of 64 and 32 against psittacosis, respectively.

The man had purchased a parakeet from a local pet store on February 17; on February 27 the parakeet became lethargic. On March 4, the parakeet was euthanized by a local veterinarian and sent to the U.S. Department of Agriculture (USDA) National Veterinary Services Laboratory, which isolated C. psittaci from a cloacal swab. Tennessee

During March 1-April 8, six members of a family (age range: 20-61 years) had onset of fever (five family members), anorexia (four), sore throat (three), cough (two), headache (two), vomiting (two), and myalgias (two). Medical evaluation of three of the patients included chest radiographs; in all three, diffuse interstitial pulmonary infiltrates were present. A presumptive diagnosis of psittacosis was made. Two persons required hospitalization. All six persons improved after therapy with doxycycline (five) or erythromycin (one). On May 7-8, blood samples were obtained from all six family members; psittacosis was diagnosed serologically in two persons.

The family had purchased a lutino cockatiel from a local pet store on February 17 and noted that the bird was irritable. The bird was euthanized by a local veterinarian in early April, and hepatosplenomegaly was detected on necropsy. Chlamydial antigen was detected by enzyme-linked immunosorbent assay from both cloacal and throat swabs, but cultures for C. psittaci were not obtained. Follow-up Investigation

The pet birds in both of these reports were traced to a distributor in Mississippi. Although the distributor shipped birds of both species to each of the associated pet stores in Massachusetts and Tennessee on February 13, the stores were unable to determine the exact shipment date of the infected birds.

On June 24, the Mississippi State Department of Health and USDA inspected the premises of the bird distributor and detected few (less than 1%) ill birds among the approximately 3000 in stock. The distributor reported that nestlings supplied by domestic breeders and imported birds received from quarantine typically were held at the facility for a maximum of 1 week before being shipped to retailers throughout the United States. Birds are given chlortetracycline hydrochloride (CTC)-treated water while at the facility. The distributor received parakeets from four domestic breeders and cockatiels from seven other domestic breeders. However, neither the parakeet nor cockatiel in this report could be traced to specific breeders.

To achieve higher serum levels of CTC in birds, the bird distributor was advised to feed all birds only CTC-impregnated feed and to notify customers of the need to maintain all shipped birds on CTC-treated feed for 45 days. Since May 1992, no additional cases of psittacosis associated with birds supplied by this distributor have been reported.

Reported by: AJ Lardner, Univ Health Svcs, Univ of Massachusetts, Amherst; S Lett, MD, E Harvey, Massachusetts Dept of Public Health. M Currier, MD, B Bracken, MPH, FE Thompson, Jr, MD, State Epidemiologist, Mississippi State Dept of Health. FT Satalowich, DVM, Psittacosis Compendium Committee, National Association of State Public Health Veterinarians, Nashville; R Hutcheson, MD, State Epidemiologist, Tennessee Dept of Health. G Birkhead, MD, Acting State Epidemiologist, New York State Dept of Health. Council of State and Territorial Epidemiologists. K Hand, DVM, Animal and Plant Health Inspection Svc, United States Dept of Agriculture. Div of Field Epidemiology, Epidemiology Program Office; Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Human psittacosis is a notifiable disease in 42 states (1), and approximately 100-250 cases are reported to CDC each year (2). However, this problem may occur more often than reflected by reported cases because 1) persons infected with C. psittaci may be only mildly symptomatic and not seek medical attention; 2) physicians may not elicit a history of bird exposure when evaluating patients because the diagnosis may not be suspected or because patients may not recall transient bird exposure; 3) convalescent-phase serum samples may not be obtained on patients who show clinical improvement on therapy; and 4) prompt initiation of appropriate antibiotic therapy may blunt the antibody response to C. psittaci, making convalescent serologies unreliable. Consequently, the extent of this multistate outbreak may have been greater than reported.

Domestic and imported pet birds are at risk for infection with and transmission of C. psittaci to other birds and to humans because shipping, crowding, and breeding promote shedding of the organism. Avian infection, which has a prevalence of less than 5%, may increase to 100% under such circumstances (National Association of State Public Health Veterinarians, unpublished data, 1992). There are no federal regulations that require CTC treatment/prophylaxis by domestic breeders, although states may promulgate such regulations. However, USDA requires a 30-day quarantine period for all imported birds to prevent the introduction of velogenic viscerotropic Newcastle disease; during this period, psittacine birds receive medicated feed containing at least 1% CTC with not more than 0.7% calcium to prevent transmission of C. psittaci to USDA staff (3). Unless treatment is continued for 45 days, infected birds arriving to distributors from breeders and from quarantine may shed C. psittaci and continue to do so after purchase by consumers (4,5). Therefore, breeders and importers should ensure that all domestic nestlings and imported birds receive prophylactic CTC for 45 continuous days to prevent future outbreaks of human psittacosis.

Administration of antibiotics through drinking water is ineffective because resulting serum concentrations of CTC are insufficient for elimination of the organism (2). Birds that do not eat CTC-impregnated feed can be given daily intramuscular injections of tetracycline hydrochloride.

Suspected cases of human psittacosis require investigation to confirm the diagnosis and establish the presence of avian infection. If the bird was purchased during the preceding 2 months, the retailer should be identified and active surveillance conducted for additional cases in owners of birds recently purchased from the retailer. Birds in pet stores associated with an infected bird should be evaluated for infection with C. psittaci by cloacal swabs on three consecutive days; birds diagnosed with C. psittaci infection should be traced to the respective distributors and breeders or importers. All birds in a retail store associated with an infected bird should be treated with CTC for 45 days. Distributor's stocks, breeder's flocks, and importer's lots supplying birds known to be infected in a retail store should be evaluated for C. psittaci infection and, if present, appropriate treatment given to groups of birds exposed to any infected birds. For accurate identification of owners and suppliers of infected birds, retailers and suppliers should maintain records identifying the origin and destination of birds. Separating birds by source and shipment date will facilitate accurate recordkeeping and may diminish the likelihood of disease transmission among birds at retailer and supplier facilities.

Forms used for surveillance conducted by CDC are being modified to include data that will assist in identifying outbreaks associated with a common source. Cases and suspected outbreaks of psittacosis should be reported promptly through local and state health departments to the Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.


  1. Chorba TL, Berkelman RL, Safford SK, Gibbs NP, Hull HF. Mandatory reporting of infectious diseases by clinicians. JAMA 1989;262:3018-26.

  2. CDC. Summary of notifiable diseases, United States, 1990. MMWR 1991;39(no. 53):55.

  3. Animal and Plant Health Inspection Service, US Department of Agriculture. 9 Code of Federal Registry (1-1-92 Edition) section 92.106

  4. Arnstein P, Eddie B, Meyer KF. Control of psittacosis by group chemotherapy of infected parrots. Am J Vet Res 1968;29:2213-27.

  5. CDC. Psittacosis surveillance, 1975-84. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, 1987.

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