An outbreak of Q fever probably due to contact with a parturient cat

Thirty-three cases (24 definite, nine probable) of Q fever were diagnosed in Victoria County, Cape Breton, Nova Scotia from May to August, 1985. Twenty-six of the cases occurred in residents of Baddeck (population 900, attack rate 2.8 percent), and 21 of the cases occurred during the month of June. There was geographic clustering of the cases: 14 of the 33 (42 percent) lived or worked in four buildings located side by side in the center of town. A case control study revealed that 25 of 29 cases were exposed to a cat that gave birth to stillborn kittens on June 8, 1985 and had bled per vaginum for three weeks prior to delivery. The cat lived in one of the buildings where geographic clustering occurred and frequently visited the other buildings. None of the 40 control subjects was so exposed (p less than 0.001). This cat had an antibody titer of 1:512 to Coxiella burnetii phase 1 antigen and a titer of 1:1024 to phase 2 antigen. Exposure to cattle, sheep and goats, the traditional reservoirs of Q fever, was uncommon among patients and control subjects and none of eight cattle tested had antibodies to C burnetii phase I antigen. We conclude that the infected parturient cat was probably responsible for this outbreak of Q fever affecting 2.8 percent of the population of the town of Baddeck.