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

LEPTOSPIROSIS 161lasts several months. Leptospires have been detected in eye lesions of affected animals,and a high concentration of antibodies can be found in the aqueous humor.However, it should be borne in mind that leptospirosis is not the only cause of periodicophthalmia. One hundred horses from the Minnesota River valley (USA) wereexamined ophthalmologically and serologically. A statistically significant associationwas found between uveitis and serology positive for pomona. Not all theseropositive horses were affected by uveitis, possibly due to different levels of exposure,strains of varying virulence, or different routes of infection (Sillerud et al.,1987). Serious cases of leptospirosis with hepatonephritic and cardiovascular syndromeshave been described in Europe.SHEEP AND GOATS: Epizootics in these species are not very frequent. Variousserovars that appear to have come from other animal species in the same environmenthave been isolated from sheep and goats in different countries (Faine, 1982),for example, hardjo in Australia and New Zealand, pomona in the United States andNew Zealand, grippotyphosa in Israel, and ballum in Argentina. In WesternAustralia (Australia), a persistent leptospirosis caused by the serovar hardjo wasfound in sheep that had no contact with cattle infected by the same serovar (Cousinset al., 1989). The authors conclude that, in addition to cattle, sheep could be a maintenancehost for hardjo.As in other ruminant species, the disease is characterized by fever, anorexia, and,in some animals, by jaundice, hemoglobinuria, anemia, abortion, birth of weak orstillborn animals, and infertility. The virulence of the infecting serovar and the conditionof the animal determine the severity of the clinical picture.DOGS AND CATS: The predominant serovars in dogs throughout the world are canicolaand icterohaemorrhagiae. In addition to these serovars, pyrogenes, paidjan,and tarassovi have been isolated in Latin America and the Caribbean, and ballum,grippotyphosa, pomona, and bratislava have been isolated in the United States(Nielsen et al., 1991). Similar serovars predominate in Europe. The infection mayrange from asymptomatic to severe. The most serious form is the hemorrhagic,which begins suddenly with a fever that lasts from three to four days, followed bystiffness and myalgia in the hind legs, and hemorrhages in the oral cavity with a tendencytoward necrosis and pharyngitis. In a subsequent stage, there may be hemorrhagicgastroenteritis and acute nephritis. Jaundice may occur with infection bycanicola or by icterohaemorrhagiae, particularly in infection caused by the latterserovar. Case fatality is estimated at 10%.The disease rarely occurs in cats.WILD ANIMALS: Many wild animals, including rodents, are perfectly adapted toleptospires and show no symptoms or lesions.Source of Infection and Mode of Transmission (Figure 12): After a week ofleptospiremia, animals shed leptospires in their urine, contaminating the environment.The best reservoirs of the infection are animals that have prolonged leptospiruriaand generally do not suffer from the disease themselves. For example, thisis true of rats, which harbor icterohaemorrhagiae and rarely have lesions. The infectionin man and animals is contracted directly or indirectly, through skin abrasionsand the nasal, oral, and conjunctival mucosa. Indirect exposure through water, soil,or foods contaminated by urine from infected animals is the most common route. An