Small ruminant lentivirus infections and diseases.

Small ruminant lentiviruses include viruses with diverse genotypes that frequently cross the species barrier between sheep and goats and that display a great genetic variability. These characteristics stress the need to consider the whole host range and to perform local surveillance of the viruses to opt for optimum diagnostic tests, in order to establish control programmes. In the absence of effective vaccines, a comprehensive knowledge of the epidemiology of these infections is of major importance to limit their spread. This article intends to cover these aspects and to summarise information related to characteristics of the viruses, pathogenesis of the infection and description of the various syndromes produced, as well as the diagnostic tools available, the mechanisms involved in transmission of the pathogens and, finally, the control strategies that have been designed until now, with remarks on the drawbacks and the advantages of each one. We conclude that there are many variables influencing the expected cost and benefits of control programs that must be evaluated, in order to put into practice measures that might lead to control of these infections.

MR imaging and CT of central nervous system tuberculosis in the patient with AIDS.

CNS TB represents a disease that complicates AIDS with an increasing incidence in endemic areas as well as in developed countries in those patients who have some risk factors such as intravenous drug abuse. Although TB infection of the CNS in AIDS patients may follow a rapidly progressive course, the imaging findings otherwise are similar to those of the nonimmunosuppressed population. Meningeal enhancement, hydrocephalus, parenchymal granulomata, and infarcts are seen frequently and are often observed in combination with one another. Nevertheless, the differential diagnosis in AIDS patients must include other opportunistic infections and primary or metastatic lymphoma of the CNS. Spinal TB usually is seen in the form of epidural abscess secondary to tuberculous spondylitis, although it may be seen in isolation of spinal column involvement. The differential diagnosis includes spinal lymphoma or pyogenic abscess formation. Radiculomyelitis or isolated spinal cord tuberculomata are much less frequently observed and can be suspected on imaging only if there is concomitant evidence of the classic findings of intracranial TB.

Intracranial tuberculosis in AIDS: CT and MRI findings.

CT and MRI findings in 35 patients with the acquired immune deficiency syndrome (AIDS) and proven intracranial tuberculosis (TB) are presented. Over 90% of the patients were intravenous drug abusers and in two-thirds TB was the first manifestation of AIDS. CT was normal in one quarter, the most frequent findings being hydrocephalus (51%) and meningeal enhancement (41%), commonly seen together (31.5%). Meningeal enhancement was seen in 48% of the CT studies with intravenous contrast medium and in 3 cases studied with MRI and i.v. gadolinium DTPA, in 2 of which CT was negative. Parenchymal involvement was found in 37% of cases; MRI was more sensitive than CT for its detection. One quarter of the patients had ischaemic lesions, mainly in the basal ganglia. We confirm the usefulness of CT and the superiority of MRI in the diagnosis of intracranial TB and in differential diagnosis from other conditions likely to be found in these patients.