Laboratory diagnosis of poliomyelitis
Throat swabs taken soon after the onset of illness, stool samples or rectal swabs are used as specimens for laboratory examination.
Viral cultivation is made in WHO recommended genetically modified murine cell culture that expresses CD155 or in human rhabdomyosarcoma RD cultures.
Cytopathic effects appear in 5-7 days on inoculation. Isolated virus is identified by neutralization tests with specific antisera that distinguish 3 basic serotypes of polioviruses.
For laboratory confirmation of cases of vaccine-associated poliomyelitis (or VAP) molecular genetic tests are applied (PCR and viral genome sequencing), as they are able to identify mutant viral strains within the same polio serotype.
Serological testing is used to evaluate the growth of antibody titers during the course of the disease.
Principles of treatment and prophylaxis of poliomyelitis
In case of poliovirus infection only symptomatic treatment is available. Administration of human donor’s immunoglobuln containing antiviral antibodies may foster patient’s recovery.
For specific prophylaxis both live- and killed-virus vaccines are commonly used. Inactivated polio vaccine (IPV or Salk’s vaccine) is prepared from the virus grown in cell cultures. Killed vaccine induces humoral antibodies, but doesn’t stimulate local intestinal immunity.
Oral trivalent vaccine contains live attenuated virus (Sabin’s vaccine) grown in cultures. This polio vaccine multiplies in human intestinal epithelium. Live vaccine treatment produces not only IgM and IgG antibodies in the blood, but also secretory IgA antibodies in the intestine. As the result, live vaccine confers both systemic and local immunity.
Oral vaccine is administered at least thrice because of 3 distinct serotypes of polioviruses.
Extremely rare cases of vaccine-associated paralytic poliomyelitis (paralytic VAP) may occur in vaccinated with live poliovaccine resulted from possible vaccine strain mutations.
The applications of genetic engineering create the opportunities for the development of a live poliovirus recombinant vaccine that can’t mutate to virulent strain. Nevertheless, current strategy of polio vaccination in many countries (e.g., in Belarus) relies on administration of inactivated vaccine only to preclude virus human circulation and to escape putative VAP cases.
The Global Polio Eradication Initiative governed by the World Health Organization (WHO) from 1988 strives for eradication of poliovirus on the Earth as it was done for smallpox virus.