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

180 BACTERIOSEStries of the former Soviet Union. In the Asian countries, the tick that transmits theinfection is I. persulcatus.In the Northern Hemisphere, the disease has the highest incidence in summer duringthe months of June and July, but it may appear in other seasons depending onthe tick life cycle in the region (Benenson, 1990).Occurrence in Animals: In endemic areas and areas near to them, various speciesof domestic animals (dogs, horses, and cattle) are infected by B. burgdorferi.In the natural foci of the infection, wild animals form the major part of the lifecycle of the tick and of the agent it transmits. In these foci, high rates of reactors tothe indirect immunofluorescence test, using antigens from the etiologic agent, havebeen found in several wild animal species. The prevalence of reactors among animalsinfested with I. dammini in eastern Connecticut from 1978 to 1982 was as follows(Magnarelli et al., 1984): white-tailed deer (Odocoileus virginianus), 27%;white-footed mice (Peromyscus leucopus), 10%; eastern chipmunks (Tamias striatus),17%; gray squirrels (Sciurus carolinensis), 50%; opossums (Didelphis virginiana),17%; raccoons (Procyon lotor), 23%; and dogs, 24%. The spirochete was isolatedfrom the bloodstream of 1 out of 20 white-footed mice examined (Andersonand Magnarelli, 1983; Bosler et al., 1984).Of 380 samples obtained from dogs from two locations selling animals inWisconsin, 53% reacted positively to the immunofluorescence test and the pathogenicagent was isolated from the blood of 8 out of 111 dogs (Burgess, 1986). In Texas, thesame test was used to examine 2,409 canine samples in 1988; of these, 132 (5.5%)yielded positive results. Many of the seropositive dogs were from the north-centralpart of the state, where most of the human cases are recorded (Cohen et al., 1990).It has been noted that horses are frequently bitten by I. dammini. In a serologicalstudy of 50 randomly selected horses in New England (USA), a known endemicarea, 13 of the horses were reactive to the indirect immunofluorescence test.In another serological survey using the enzyme-linked immunosorbent assay(ELISA) technique, 13 of 100 horses examined in the month of June tested positiveand 6 of 91 (7%) tested positive in the month of October. The horses came from fiveeastern US states. The frequency of antibody responses was higher in horses fromNew Jersey than in horses from Pennsylvania (Bernard et al., 1990). In contrast, noreactive horses were found in central Texas (Cohen et al., 1992).The Disease in Man: The characteristic cutaneous lesion, erythema migrans(EM), appears from 3 to 20 days after the tick bite. The lesion begins with a red maculaor papule that widens. The borders are clearly delineated, the central lesionpales, and an annular erythema forms. The erythema may be recurrent, with secondarylesions appearing on other parts of the body. The cutaneous lesions may beaccompanied for several weeks by malaise, fever, cephalalgia, stiff neck, myalgias,arthralgia, or lymphadenopathy. The EM constitutes the first stage or phase of thedisease and lasts a few weeks, but may recur. In the second stage, after several weeksor months have passed and the agent has disseminated, some patients develop multipleEMs, meningoencephalitis, neuropathies, myocarditis, and atrioventriculartachycardia. Some suffer arthritic attacks in the large joints, which may recur forseveral years, at times taking a chronic course (Steere et al., 1983). Months or yearslater, the third stage may occur in some patients; this stage sometimes includes acrodermatitischronica atrophicans and neurological and articular changes.