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

172 BACTERIOSESwhite nodules. Some children born apparently healthy fall ill with meningitis shortlythereafter (a few days to several weeks). In these cases, the infection was probablyacquired in utero or during birth. In the US, neonatal meningitis is the most commonclinical form, while in Europe, perinatal septicemia prevails. Hydrocephalus isa common sequela of neonatal meningitis.Meningitis or meningoencephalitis is the most common clinical form in adults,especially in those over 50. Listerial meningitis often occurs as a complication indebilitated persons, alcoholics, diabetics, in patients with neoplasias, or in elderlypatients with a declining immune system. Before the existence of antibiotics, casefatality was 70%. Listerial septicemia also occurs among weakened adults, especiallypatients undergoing long-term treatment with corticosteroids or antimetabolites.In addition, listeriosis may result in endocarditis, external and internalabscesses, and endophthalmitis. A cutaneous eruption has been described amongveterinarians who handled infected fetuses.The recommended treatment for maternal-fetal listeriosis is ampicillin. Variousantibiotics, such as ampicillin (alone or in combination with aminoglycosides),tetracycline (not for those under 8 years of age), and chloramphenicol, may be usedfor the other forms of the disease (Benenson, 1990).The Disease in AnimalsSHEEP, GOATS, AND CATTLE: Listeriosis manifests itself in ruminants as encephalitis,neonatal mortality, and septicemia. The most common clinical form is encephalitis. Insheep and goats, the disease has a hyperacute course, and mortality may vary from 3%to more than 30%. In cattle, listerial encephalitis has a chronic course, with the animalssurviving for 4 to 14 days. In general, only 8% to 10% of a herd is affected.A ruminant with encephalitis isolates itself from the herd and shows symptoms ofdepression, fever, lack of coordination, torticollis, spasmodic contractions and paralysisof facial muscles and throat, profuse salivation, strabismus, and conjunctivitis.The animal tries to lean against some support while standing and, if able to walk,moves in circles. In the final phase of the disease, the animal lies down and makescharacteristic chewing movements when attempting to eat.Listerial encephalitis can affect animals of any age, but it is more common in thefirst three years of life. Nevertheless, it does not appear before the rumen becomesfunctional. Septicemia is much more common in young animals than adults.Abortion occurs mainly during the last months of gestation and is generally the onlysymptom of genital infection, the dam showing no other signs of disease. If uterineinfection occurs in the cow before the seventh month of pregnancy, the dead fetus isusually retained in the uterus for several days and has a macerated appearance, withmarked focal necrotic hepatitis. In addition, the placenta may be retained and metritusmay develop. If infection occurs in the final months of pregnancy, the fetus ispractically intact and shows minimal lesions.L. monocytogenes can also cause mastitis in cows. There are few described cases,either because the presence of this agent in cows has not been studied or because itsoccurrence really is rare. Mastitis caused by Listeria varies in severity from subclinicalto acute and chronic. Elimination of the agent in milk occurs over a longperiod of time and may have public health repercussions, especially since pasteurizationdoes not guarantee complete safety if the viable bacteria count is high beforeheat treatment (Gitter, 1980).