Clinical Manifestations, Diagnosis, Treatment, and Control
Lymphocytic Choriomeaingitis (LCM)
LCM has been found in the Americas, Europe, and Asia, but not in Africa or Australia. Outbreaks are sporadic and often associated with experimental animal colonies.
The disease in humans is usually benign, with symptoms resembling influenza. Inapparent cases (determined by serologic changes) are frequent during outbreaks. Meningitis (with 90 to 95 percent lymphocytes in the cerebrospinal fluid) may occur as a primary symptom of disease, or more usually as a relapse several days after apparent recovery from the acute illness. In some cases there may be meningoencephalitic signs and symptoms, with reflex changes, paralyses, cutaneous anesthesias, and somnolence. Fatal cases are rare. When infections occur in pregnancy, complications of encephalitis, hydrocephaly, and chorioretinitis in the fetus and the newborn may be seen. Treatment is limited to supportive care. Control is limited to control of mouse populations in houses and to vigilant supervision of laboratory colonies of mice and hamsters.Argentine Hemorrhagic Fever (Junin)
The disease occurs in the heavily agricultural moist pampas provinces to the west of Buenos Aires. It is seen in the rural regions, mostly in farm workers, including migrant workers. Several hundred cases are seen annually, occurring mainly in the harvest season between April and July. Infection in humans results from contact with field rodents. The incubation period is from 10 to 14 days, with an insidious onset beginning with malaise, fever, chills, head and back pains, nausea, vomiting, and diarrhea or constipation. In progressive cases, hemorrhagic manifestations begin about the fourth day of illness, and may proceed to death (in about 10 percent of confirmed cases). In some cases, neurological symptoms may predominate.
Laboratory findings include leukopenia, thrombocytopenia, albuminuria, and cylindruria.
Serologic testing is an aid to diagnosis, but as is the case with many virus diseases, virus isolation and identification are recommended. Convalescence lasts several weeks after severe illness, and recovery is then usually complete. There are no proven specific antiviral agents; but there are recent reports of successful treatment with immune plasma. When it has been given before the eighth day of illness, marked reduction in mortality has been observed. Rodent control would appear to be an obvious prevention measure, but it is not practical, given the vast areas where the virus is endemic. Much attention has been given to development of a vaccine, and at present a live attenuated vaccine shows promise of becoming useful in preventing disease in human beings. Another vaccine possibility being explored utilizes the avirulent Tacaribe virus to induce immunity against Junin.Bolivian Hemorrhagic Fever (Machupo)
This disease is localized to several provinces of the Department of Beni, in the Amazonian lowlands, and is endemic in the local rodent (Calomys) populations. Exposed human beings have an incubation period of about 2 weeks. Patients have a high fever for at least 5 days; myalgia, headache, conjunctivitis, cutaneous hyperesthesia, nausea, and vomiting are features of the illness. Hemorrhagic manifestations occur in some 30 percent of patients, and there may be serious bleeding. Hypotension in the second week of illness is seen in about 50 percent of patients, and in many patients it proceeds to hypovolemic shock and death. Symptoms indicative of central nervous system involvement, among the tremors of tongue and extremities, convulsions, and coma, appear in almost half the patients. The death rate in several epidemics has been about 25 percent. Convalescence is protracted. Laboratory findings include leukopenia, hemoconcentration, and proteinuria. Pathological findings include generalized adenopathy and focal hemorrhages in various organs. No specific therapy is known. Treatment is limited to supportive measures. Rodent control in homes and villages has proven to be an effective means of controlling epidemics, and also of preventing sporadic cases of disease.
Wilbur G. Downs