zoonoses and communicable diseases common to ... - PAHO/WHO

80 BACTERIOSESMost cases have occurred in children, who have more contact with cats.In temperate climates, the disease tends to be seasonal, with most cases occurringin fall and winter. In hot climates, there are no seasonal differences.Source of Infection and Mode of Transmission: The most salient fact in the epidemiologyof this disease is its causal relation with a cat scratch. It is estimated thatabout 65% of patients were scratched or bitten by cats and that 90% of the cases hadsome contact with these animals. Nevertheless, cases have been observed in whichthe skin lesion was inflicted by such inanimate objects as splinters, thorns, or pins.Cats undoubtedly play an important role in the epidemiology, but there is doubtabout whether it is as host for the etiologic agent or simply as a mechanical vector.Another possibility is that the etiologic agent is part of the normal flora of the cat’smouth and is transferred to the nails when the cat grooms itself (Hainer, 1987).Several observations—among them the fact that some cases were caused by inanimateagents—suggest that cats could be mechanical transmitters. Cats implicated inhuman cases were healthy animals, almost always young, that did not react to theHanger-Rose intradermal test. It is also interesting to note that cats inoculated withmaterial from the lymph nodes of human patients did not become ill. In summary, ithas not yet been possible to show that cats are infected with the disease or are carriersof its causal agent, despite the many attempts made. According to Margileth(1987), cats are only able to transmit the infection for a short time (two to threeweeks). CSD is usually transmitted from cats to man through a scratch and, less frequently,through a bite or licking. In Parinaud’s oculoglandular syndrome, the pointof entry for the agent is the conjunctiva or eyelids when a person rubs his or her eyesafter picking up a cat (August, 1988).Diagnosis: CSD can be clinically confused with other diseases that cause regionallymphadenopathies, such as tularemia, brucellosis, tuberculosis, pasteurellosis,infectious mononucleosis, Hodgkin’s disease, venereal lymphogranuloma, lymphosarcoma,and lymphoma. All these diseases must be excluded before consideringa diagnosis of CSD. The symptoms described above, a history of a skin lesioncaused by a cat scratch or bite, the histopathology of biopsy material taken from theaffected lymph node, and the Hanger-Rose intradermal test constitute the basis fordiagnosis. The Hanger-Rose antigen is prepared by suspending pus taken from anabscessed lymph node in a 1:5 saline solution and heating it for 10 hours at 60°C.The antigen is very crude and difficult to standardize. The test is carried out by intradermalinoculation with 0.1 ml of the antigen. The reaction may be read in 48 hours.Edema measuring 0.5 cm and erythema of 1 cm are considered a positive reaction.The test is very useful, since 90% of 485 clinically diagnosed cases gave positiveresults, while only 4.1% out of 591 controls tested positive.There is a danger of transmitting viral hepatitis with this antigen; therefore, thepreparation should be heat-treated for a lengthy period, as indicated above. It maybe very useful to demonstrate the presence of the putative etiologic agent, A. felis,using Warthin-Starry stain on histological sections from the skin or lymph nodes.Control: Prevention is limited to avoiding cat scratches and bites. Cutting thecat’s nails, washing and disinfecting any scratch or bite, and washing one’s handsafter petting or handling a cat are also recommended (August, 1988).