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

52 BACTERIOSESFigure 5. Bovine brucellosis (Brucella abortus). Mode of transmission.BullArtificial inseminationCowDirect and indirect contact,ingestion of raw milkand fresh cheesesCowFetuses, fetalmembranes,vaginal secretionsContact with fetuses,contaminated objectsEnvironmentalcontamination(pasture, forage,water, stable)Ingestion, contactBull andCowManB. melitensis biovar 3 was identified in a cervical culture. Cervical and blood culturescontinued to be positive. Although the child was asymptomatic, a positiveblood culture of the same biovar and an agglutinating titer of 1:100 were obtained.Splenomegaly was the only abnormality found in the child at 13 days. Prior to thesecases, there were descriptions of human-to-human transmission due to transfusionor bone marrow transplants.INFECTION IN CATTLE (Figure 5): The main sources of infection for cattle arefetuses, afterbirth, and vaginal discharges containing large numbers of brucellae. Toa lesser extent, farm areas can be contaminated by fecal matter of calves fed on contaminatedmilk, since not all the organisms are destroyed in the digestive tract.The most common route of transmission is the gastrointestinal tract followingingestion of contaminated pasture, feed, fodder, or water. Moreover, cows customarilylick afterbirth, fetuses, and newborn calves, all of which may contain a largenumber of the organisms and constitute a very important source of infection. Cows’habit of licking the genital organs of other cows also contributes to transmission ofthe infection.It has been shown experimentally that the organism may penetrate broken andeven intact skin. The extent to which this mode of transmission is involved in naturalinfection is unknown.Bang and others experimentally reproduced infection and disease via the vaginalroute. The results of those experiments indicate that a large number of brucellae arenecessary to infect a cow by this means. However, there is no doubt that the