Respiratory specimens include nasopharyngeal aspirations, nasal washings, and nasal aspirations.
The ELISA, immunofluorescence assay, and fluoroimmuno-assays are used to detect HPIV antigen directly in urine speci-mens. These methods are sensitive and specific. Shell viral assay is a sensitive method for rapid demonstration of the virus.
Cell culture: The virus can be isolated from clinical speci-mens by culture in PMK and LLC-MK2 cell lines. The CPEs are rarely demonstrated during primary isolation of the virus in tissue culture with exception of HPIV-2. The latter causes formation of syncytium in the infected cells. Hemadsorption inhibition using guinea pig erythrocytes is also used for detection of virus antigen in cell lines within 3–10 days of incubation.
Hemagglutination inhibition, neutralization, ELISA, and Western blot are frequently used antibody-based serological tests for diagnosis of HPIV infection. A fourfold rise in antibody titer of acute and convalescent sera is diagnostic of acute infection.
Ribavirin has been shown to be effective against HPIV infection in vitro. Uses of ribavirin aerosols or systemic therapy for treat-ment of HPIV infection in children and adults who are severely immunocompromised have shown mixed results with uncer-tain clinical benefit.
Live attenuated vaccine is available. Field trials of formalin-killed whole HPIV (HPIV-1, HPIV-2, and HPIV-3) have proved to be ineffective in children. These vaccines failed to protect against natural infection by parainfluenza virus.