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Epidemiologic Notes and Reports Psittacosis at a Turkey Processing Plant -- North Carolina, 1989

On October 14 and 15, 1989, a physician in North Carolina treated two poultry workers from a turkey processing plant (plant

  1. in North Carolina for possible psittacosis. Following notification on October 16, the Division of Epidemiology, North Carolina Department of Environment, Health, and Natural Resources, conducted a telephone survey of 12 health-care providers in the locality around plant A and identified 32 adults (aged 18-50 years) who had been evaluated for febrile respiratory or gastrointestinal illnesses during the first 2 weeks of October. These persons were considered as having suspected psittacosis, and all were employees at plant A. This report describes the investigation of this outbreak of psittacosis, which was the largest documented in North Carolina since 1956.

Persons with suspected psittacosis were identified by reviews of patient records at the plant clinic, area hospitals, area physicians' offices and clinics, and county health departments and by reviews of information from the Virology/Serology Section of the North Carolina State Laboratory for Public Health. A suspected case of psittacosis was defined as a febrile, respiratory, or gastrointestinal illness with onset during October in an employee at plant A; a confirmed case was defined as a suspected case having at least one of the following laboratory findings: 1) isolation of Chlamydia psittaci from a patient specimen, 2) a fourfold rise in complement-fixation (CF) antibody to Chlamydia group antigen, or 3) a single Chlamydia CF titer of greater than or equal to 32. Acute-phase serum specimens were obtained within 14 days of illness onset; convalescent-phase serum specimens were obtained within 60 days of illness onset.

Sixty suspected cases of psittacosis were identified among workers at plant A. Of these, 40 (67%) met the definition for a confirmed case (Figure 1). Thirty-nine cases were confirmed by serology alone; one also was confirmed by isolation of Chlamydia from a bronchial washing specimen. Records were available for 38 patients; among these patients, the most frequently recorded symptoms were fever (89%) and cough (71%). Other reported symptoms included aches (42%), chest pain (39%), headache (37%), nausea (37%), vomiting (34%), diarrhea (34%), and abdominal pain (18%). Twenty-four (60%) of the 40 persons meeting the case definition were hospitalized.

For the 32 patients with confirmed psittacosis whose temperatures were recorded, the mean maximum body temperature was 39.4 C (103 F) (range: 36.6-41.1 C (98-106 F); median: 39.4 C (103 F)). The mean maximum white blood cell (WBC) count for the 22 patients whose WBC counts were recorded was 10,600 per mm3 (range: 7100-20,900 per mm3; median: 10,100 per mm3). Abnormal chest radiograph results were reported for at least 29 patients, and abnormal liver function tests, for at least seven.

Thirty-eight (95%) of those meeting the case definition worked on the day shift at plant A. Day-shift employees working in the "chilling," "cut-up divided by ebone," and "other" areas of the plant had direct contact only with cleaned and processed turkeys and appeared to be at lowest risk for meeting the case definition (Table 1). In contrast, workers exposed to turkey viscera in the "offal/truckwash," "U.S. Department of Agriculture (USDA) inspection," and "evisceration" areas were at highest risk. Workers exposed to live birds and their feces in the "live hang" area (where live turkeys are uncrated and hung on the processing line) were at intermediate risk (Table 1).

A plant veterinarian reported that a portion of a flock of tom turkeys processed at plant A during the day shift on September 29 had a carcass condemnation rate of 25% attributed to air sacculitis*; the usual rate of carcass condemnation at plant A is 1%-3%. None of the condemned carcasses or specimens from that flock were retained for necropsy, culture, or further examination. Assuming that exposure occurred on September 29, the mean incubation period for the 40 cases was 15 days (range: 3-31 days; median: 14 days) (Figure 1).

The total compensation disability insurance payments to 34 psittacosis patients was nearly $13,000, and the total medical costs paid for 35 patients was greater than $124,000, according to information from plant A's workers' compensation insurer. Reported by: JA Rhyne, MD, Wilmington; L Hunter, DVM, C Staes, MPH, RA Meriwether, MD, JN MacCormack, MD, State Epidemiologist, North Carolina Dept of Environment, Health, and Natural Resources. Div of Field Svcs, Epidemiology Program Office, CDC.edEditorial Note:

Psittacosis ("parrot fever") is caused by the obligate intracellular bacterium C. psittaci, which can infect a variety of mammalian, avian, and reptilian species (1). Inhalation of infectious aerosols derived from feces, fecal dust, and secretions of C. psittaci-infected animals is believed to be the primary route of infection for most psittacosis patients; percutaneous exposure may be an alternate, but less important, route (1-3). Most cases of psittacosis are attributed to exposure to infected birds. The source birds can be asymptomatically infected (i.e., carriers) or can show signs of infection, such as anorexia, ruffled feathers, depression, and watery, green droppings.

Psittacosis is a rarely reported mild illness with no specific signs and symptoms, most often occurring as a sporadic illness in persons having contact with infected cage birds. Occasionally, clusters of cases occur among workers at poultry processing plants or in other settings (1,2). The diagnosis can be established with certainty only by paired serologic testing or identification of the organism by culture. In North Carolina, the nation's largest turkey-producing state ( greater than 50 million turkeys produced each year), fewer than 10 cases of psittacosis per year have been reported in the past 10 years; most cases were related to pet bird exposure.

The clinical and epidemiologic findings of the North Carolina study are comparable to those in other reported outbreaks (1,3). This report demonstrates that poultry workers having contact with turkey viscera and feces or with live birds are at greatest risk for psittacosis. However, it also supports a recent report from Minnesota (3) in which defeathered, eviscerated, and chilled turkey carcasses may transmit psittacosis. In addition, in both of these outbreaks, the incubation period for psittacosis was longer than the 4-14 days commonly cited (1,2).

The principal strategies for the elimination of psittacosis outbreaks among poultry workers are reducing C. psittaci infection in the flocks and protecting workers from exposure to the organism, even if they work with infected birds. Raising turkey flocks in controlled, indoor environments would minimize the contact between domesticated fowl and C. psittaci-infected wild birds and animals, thereby reducing the risk for infection in the flocks. Testing of flocks for C. psittaci infection is difficult, time consuming, and nonspecific because the majority of strains isolated have no potential for causing human illness. Testing ill birds in flocks for C. psittaci infection and treating infected flocks with chlortetracycline according to USDA regulations before slaughter may reduce worker exposure to this agent. Nevertheless, birds can remain asymptomatically infected after treatment (4) and can transmit infection at slaughter to humans.

As a result of the North Carolina outbreak, the management of plant A initiated an ongoing program of increased flock surveillance for ill turkeys. A short-term program of culturing flocks raised on open land for Chlamydia species and necropsy of any dead birds was also initiated. When chlamydial infection was detected, the implicated flocks were treated with chlortetracycline according to USDA regulations, and plant A employees were strongly encouraged to wear paper face masks when these flocks were processed.

The use of respiratory protection approved by the Mine Safety and Health Administration and by CDC's National Institute for Occupational Safety and Health (NIOSH) may further reduce the inhalation risk of exposure to infectious Chlamydia aerosols (5,6). However, no research-based information exists on which to recommend an appropriate class of respirator.


  1. CDC. Psittacosis surveillance, 1975-1984. Atlanta: US Department of Health and Human Services, Public Health Service, 1987.

  2. Schaffner W. Psittacosis. In: Mandell GL, Douglas RG Jr, Bennett JE, eds. Principles and practice of infectious diseases. New York: John Wiley and Sons, 1979:1476-9.

  3. Hedberg K, White KE, Forfany JC, et al. An outbreak of psittacosis in Minnesota turkey industry workers: implications for modes of transmission and control. Am J Epidemiol 1989;130:569-77.

  4. Benenson AS, ed. Control of communicable diseases in man. 13th ed. Washington, DC: American Public Health Association, 1980.

  5. Office of the Federal Register. Code of federal regulations: occupational safety and health standards. Subpart I. Personal protective equipment. Washington, DC: Office of the Federal Register, National Archives and Records Administration, 1983. (29 CFR *** 1910.134).

  6. NIOSH. Guide to industrial respiratory protection. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1987; DHHS publication no. (NIOSH)87-116.

    • An avian disorder similar to pleurisy in mammals that is a common but nonspecific manifestation of psittacosis in turkeys.

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