Immunological surveys of diphtheric antitoxic antibodies in some African and Asian countries

Abstract

Immunological surveys of diphtheric antitoxic antibodies confirmed the existence of a high circulation of Corynebacterium diphtheriae in some African and Asian countries. The high immunity level in early childhood confirms the well known fact that other forms of diphtheria, in particular the cutaneous forms, participate in the formation of antitoxic antibodies. Immunological surveys can determine relatively exactly the extent of risk of infection in the separate age groups and thus delimit the range of the planned vaccination campaigns. Exact determination of the age groups eligible for vaccination makes it possible efficaciously to employ the means allotted for the health services. In some cases, it is possible to dispense with vaccination altogether. However, it should be borne in mind that a change in the socio-economic conditions and increasing urbanization of these countries may induce a radical change in the situation. Children not protected from the cutaneous forms thanks to a better hygienic and social standard, might fall ill with diphtheria of the throat in the future. It is therefore advisable to continue the follow-up of the immune state of the child population at several years time intervals and, in case of necessity, timely to intervene by vaccinating the endangered groups.

PIP: This article summarizes diphtheria antitoxic antibody surveys in 6740 sera from 11 African and Asian countries, and reviews the literature on the immunology of diphtheria. Classic diphtheria of the throat is primarily a temperate zone phenomenon. In subtropical and torrid zones, other forms, mainly cutaneous diphtheria, still prevail. Antitoxic antibodies are present in the majority of preschool children in the tropics, while complete immunization in the subtropics takes 10-15 years. In this survey, in collaboration with the WHO Reference Serum Bank, the authors assayed diphtheria antitoxic antibodies in 6740 sera from 1967-1973 by titration on monkey kidney tissue cultures, by the pH metabolic inhibition test. The countries surveyed were Nigeria, Niger, Kenya, Togo, Burma, Algeria, Tunisia, Afghanistan, Mongolia, Yugoslavia. Most countries had adequate natural immunity at an early age. Exceptions were parts of Tunisia, and most of Afghanistan where morbidity was high. Yugoslavia used to have the highest morbidity in Europe from diphtheria, but 90% of children are now immunized. It is important to note that the percentage of immunized children is highest where hygiene is poor, in the tropics, and among rural rather than urban dwellers, and in boys rather than girls. Prolonged breast feeding appears to confer immunity in children. Therefore, as hygiene improves with modernization and urbanization, cutaneous diphtheria disappears, and populations will need to be protected by vaccination.