Serological evidence of hantavirus infection in laboratory rats and personnel.

Laboratory-acquired haemorrhagic fever with renal syndrome (HFRS) has been reported in many countries. A serological survey of laboratory white rats and of laboratory personnel for antibodies to hantaviruses was conducted in Singapore. Forty-four per cent (143/329) of rats were seropositive by the indirect immunofluorescent antibody test but none had hantaviral antigens in lung tissues. Two of 74 laboratory personnel were seropositive but neither had a history of clinical illness. The high seropositivity rate among laboratory rats led to their replacement with Hantaan virus-free strains. To eliminate the hazard of laboratory-acquired HFRS, regular serological screening of laboratory rats and replacement of infected animals with seronegative stocks should be implemented. High risk techniques with laboratory rats, which are likely to generate aerosols, should be performed in biological safety cabinets. Serological surveillance of laboratory personnel and reporting of suspected HFRS cases are useful in the early detection of hantavirus infection.

Hantavirus infections in humans and commensal rodents in Singapore.

To determine the extent of hantavirus infection in Singapore, serological studies using the indirect immunofluorescent antibody (IFA) test were conducted on commensal rodents and on human patients in 4 diagnostic groups. Virus isolation using a Vero E6 cell line was performed on hantaviral antigen-positive rodent lung tissue. Of 142 rodents and 3 insectivores studied, 37 (26%) were seropositive for IFA. Rattus norvegicus was the predominant species captured, with the highest species-specific seropositive rate of 32% (36 of 113). A hantavirus strain, R36, was isolated from one R. norvegicus. Seropositive rates for human patients were: 8% respectively for dengue haemorrhagic fever suspects and for non-A non-B hepatitis patients, 3% for leptospirosis suspects and 2% for acute nephritis patients. 2 patients had marked liver dysfunction but mild renal involvement. This hepatitis-like manifestation appears to be a clinical variant of hantavirus infection.

Differential diagnosis of extra-axial intracranial tumours by dynamic spin-echo MRI.

Dynamic MRI was performed on 22 patients with extra-axial intracranial tumours. Serial images were obtained every 30 s for 3 min using a spin-echo sequence (TR 200, TE 15 ms) after rapid injection of Gd-DTPA, 0.1 mmol/kg body weight. The contrast medium enhancement ratio (CER) was correlated with the histology of the tumours. Meningiomas and extra-axial metastases showed a sharp rise, then a gradual decline. Although both had a definite early peak of CER, metastases showed a more rapid decline. Neuromas and extra-axial lymphoma showed a slow, steady increase with no peak within 180 s. This study indicates that the CER is helpful in the differentiation of extra-axial tumours.