Notes from the Field: Q Fever Outbreak Associated with Goat Farms --- Washington and Montana, 2011

On April 22, 2011, the Q fever bacterium Coxiella burnetii was detected in a goat placenta collected from a farm in Washington, where 14 of 50 (28%) pregnant does had aborted since January. A county health alert advised health-care providers to ask patients with symptoms compatible with Q fever (e.g., fever, headache, chills, and myalgia) about exposure to goats, and the owners of the farm informed purchasers of their goats that C. burnetii had been detected in their herd. On May 25, the county health department reported a symptomatic patient with antibodies to C. burnetii who had purchased goats from the farm in February. On May 27, a report from Montana identified a child seropositive for C. burnetii whose family had purchased goats from the Washington farm in October 2010; one of the goats aborted triplets 2 weeks before the child's May 12, 2011, illness onset. On May 31, five more persons reported onset of symptoms compatible with Q fever from late March to mid-May, following exposure at a Montana farm to goats purchased from the Washington farm at various times during October 2010--January 2011. On June 10, the Washington State Department of Health and Montana Department of Public Health and Human Services requested CDC assistance to characterize the extent of the outbreak, distribute Q fever information, and identify others at risk for infection.

Goats sold after June 2010 by the Washington farm where C. burnettii initially was detected were traced to 21 farms in Washington (10 counties), Montana (three counties), and Oregon (one county). Seventeen farms participated in the outbreak investigation. C. burnetii infection was detected in 16 of 17 goat herds, including polymerase chain reaction confirmation of bacterial shedding in feces, vaginal mucous, or milk in 161 of 667 (24%) goats tested and an overall seroprevalence of 21% (131 of 615) by enzyme-linked immunosorbent assay. To date, 19% (20 of 108; 11 in Washington and nine in Montana) of serologically tested persons met the outbreak case definition of a person epidemiologically linked to at least one farm of interest (i.e., as a goat owner, farm visitor, or neighbor) since January 2011 with a C. burnetii phase II immunoglobulin G titer ≥1:128 by immunofluorescence assay (1). No deaths were reported; four of the 20 persons were hospitalized, and five were asymptomatic.

Both states implemented a herd management plan to promote continued communication between public health and agricultural authorities and to advise goat owners to disinfect birthing areas, avoid contact with birth products, limit visitor access to animal holding areas, maintain an animal registry, and report animal abortions and positive Q fever test results to state authorities. All homes within a 1-mile radius of the Washington farm where C. burnetii was initially detected and a Montana farm that also had high goat seroprevalence linked to human illness were visited once by CDC or by county public health officials and CDC in July or August 2011 to provide Q fever health education and offer human serologic testing. The states have received no additional reports of Q fever since July.

Q fever (a category B bioterrorism agent) is a nationally notifiable disease in humans and is endemic throughout the United States with a national seroprevalence of 3% (2). Washington and Montana typically report ≤3 cases of Q fever annually. Acute Q fever is characterized by a self-limited febrile illness or, less often, by pneumonia or hepatitis. Less common still is chronic Q fever, which affects <5% of infected persons and presents as endocarditis in patients with preexisting valvular disease. Pregnant women, immunosuppressed persons, and patients with a preexisting heart-valve defect are at greatest risk for chronic Q fever. Doxycycline is recommended for treatment of acute Q fever. C. burnetii is highly infectious, persists in the environment, and can travel for miles once windborne (3). Transmission can occur via inhalation of contaminated aerosols or dust; human-to-human transmission is rare. Cattle, sheep, and goats are the primary Q fever reservoirs. Continued community awareness is essential for disease prevention and control. Additional information is available at http://www.cdc.gov/qfever.

Reported by

Washington State Dept of Agriculture; Washington State Dept of Health. Montana Dept of Livestock; Montana Dept of Public Health and Human Svcs. Oregon Dept of Human Svc. Veterinary Svcs, Animal and Plant Health Inspection Svc, US Dept of Agriculture. Rickettsial Zoonoses Br, Div of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases; EIS officers, CDC. Corresponding contributors: Adam Bjork, PhD, abjork@cdc.gov, 404-639-2603; Alicia Anderson, DVM, aha5@cdc.gov, 404-639-4499.

References

1. Bamberg WM, Pape WJ, Beebe JL, et al. Outbreak of Q fever associated with a horse-boarding ranch, Colorado, 2005. Vector Borne Zoonotic Dis 2007;7:394--402.
2. Anderson AD, Kruszon-Moran D, Loftis AD, et al. Seroprevalence of Q fever in the United States, 2003--2004. Am J Trop Med Hyg 2009;81:691--4.
3. Hawker JI, Ayres JG, Blair I, et al. A large outbreak of Q fever in the West Midlands: windborne spread into a metropolitan area? Commun Dis Public Health 1998;1:180--7.